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2.1 History and General Introduction of Plastic

2.2 Plastic Statistics of the World

2.3 Plastic Statistics of India

2.4 Issues Related with Plastic Bags

2.5 Plastic Footprints in Oceans and Impact on Marine Life

2.6 Issues Related to Plastic Products Manufacturing

2.7 Plastic Waste Scenario (Quantity and Composition)

2.8 Facts Related to Degradation of Plastic

2.9 Problems in Recycling and Incineration of Plastic Garbage

2.10 Biodegradable Polymers and Bio-plastic (Issues and Scope)

2.10.1 Types of biodegradable plastics

2.10.2 Economical aspects of biodegradable plastic/polymers

2.10.3 Decomposition of biodegradable plastic/polymers

2.10.4 Problems and challenges

2.11 Citation of Related Patents

2.12 Commercially Available Biodegradable Products

2.13 Nursery Bags & Containers Related Research (Type/Shape/Size/ Design)

2.14. Air Induced Root Pruning

2.15 Role of Copper in Root Pruning

2.16 Copper as Biocide

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 8

2.1 HISTORY AND GENERAL INTRODUCTION OF PLASTIC

According to the „Oxford Dictionary‟ word „Plastic‟ was coined in the mid of 17th

century and derived from French „plastique’, Latin „plasticus’ or from Greek „plastikos’/

„plassein’. Meaning of all these cognates is „able to be molded into different shapes‟ (Joel,

1995). The first man-made plastic, a modification of cellulose, was created by Alexander

Parkes in 1862 and called „Parkesine‟. In 1868 John Wesley Hyatt invented Celluloid,

derived from cellulose and alcoholized camphor that could be molded with heat and pressure

into a durable shape. By 1900, movie film was an exploding market for celluloid (Harris,

1981).

Plastic, from the time of their origin have become an indispensable part of our life and

in modern society. Synthetic plastics are extensively used in packaging of products like food,

pharmaceuticals, cosmetics, detergents and many products manufactured from plastics are a

boon to public health, e g. disposable syringes and intravenous bags (Halden, 2010). This

utilization is still expanding at a high rate of 12% per annum (Sabir, 2004) and has replaced

paper and other cellulose-based products for packaging because of their better physical and

chemical properties viz. strength, lightness, resistance to microorganisms (Shah et al., 2008)

and favorable mechanical/thermal properties, stability and durability (Rivard et al., 1995).

With time, stability and durability of plastics have been improved continuously, hence this

group of materials is now considered as a synonym for the materials being resistant to many

environmental influences (Joel, 1995). Plastic is inert i.e. resistant to biodegradation, durable,

hygienic, lightweight, cheap, and malleable (Mohee and Unmar, 2007). It has been proven

that polyolefins especially low density polyethylene (LDPE), are resistant against degradation

and microorganism attacks (Mahmood and Reza, 2004).

These are manmade long chain polymeric molecules (Scott, 1999). The basic materials

used for making plastics are extracted from oil, coal and natural gas that comprise inorganic

and organic raw materials, such as carbon, silicon, hydrogen, nitrogen, oxygen and chloride

(Seymour, 1989). Petroleum-based synthetic polymers are introduced in the ecosystem as

industrial waste products that generate several problems e.g. visual pollution, blockage of

gutters and drains, livestock deaths and threat to aquatic life (Shimao, 2001).

2.2 PLASTIC STATISTICS OF THE WORLD

Production of plastic has increased from 0.5 million tonnes in 1950 to 260 million

tonnes in 2007. This increase in usage, especially disposable items of packaging, makes up

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37% of all the plastic produced (Plastic Europe, 2008). Packaging utility is the biggest field

where polythene and its kind material are used. It is estimated that 41% of plastics are used in

packaging, and that almost half of that volume is used to pack food products (O'Brine and

Thompson, 2010). Low density polyethylene is the most applied polyolefin in packaging,

horticulture and agricultural utilizations (Bastioli et al., 1991).

As population is increasing so the consumption of synthetic plastic is increasing, only

in a span of one year (1996-95) shipments from the Canadian Plastic Industry increased by

10.6% (Charron, 2001). In Australia about 1 million tones of plastic materials are produced

each year and a further 587,000 tonnes are imported (Australian Academy of Science, 2002). In European countries on an average 100kg of plastic is used per person each year (Mulder,

1998.) The bags, with a typical thickness of 16 microns and weight of 7-8 gm are provided

free of charge in Israeli stores and supermarkets (Ayalon et al., 2009). In Mauritius, plastic

wastes constitute around 8% by weight (or 100 tonnes) of the total solid waste generated

daily. The amount of plastic carry-bags disposed at the landfill is approximately 1000 tonnes

annually, while the local plastic industries generate around 250–300 million plastic carry

bags per annum (Mohee and Unmar, 2007). In Israel, 2 billion HDPE carrier bags are

manufactured every year. The total amount of these bags is 30,000 tons/year. At the end of

2007, there were 2,007,300 households in Israel. It means that the consumption in Israel per

household is 1000 bags /yr, 2.7 bags per day. Every person in Israel uses an average of 300

bags /yr, similar to other countries such as Ireland, where before introduction of the levy, a

yearly average was of 330 bags per person (Ayalon et al., 2009). The estimated figure of

plastic waste generation across the Pakistan was 1.32 million tons per annum (Sabir, 2004).

The plastic industry in Pakistan was reported to be growing at an average annual growth rate

of 15% (Shah et al., 2008).

2.3 PLASTIC STATISTICS OF INDIA

In India, plastic consumption grew exponentially in the 1990s. In the decade 1990 -

2000, total consumption of plastics grew twice (12% /yr) as fast as the gross domestic

product growth rate based on purchasing power parities (6% /yr). The current growth rate in

Indian polymer consumption is higher than that in China and many other key Asian countries.

The average Indian consumption of virgin plastics per capita reached 3.2 kg in 2000/2001 (5

kg if recycled material is included) from a mere 0.8 kg in 1990/1991 that is only one-fourth

of the consumption in China (12 kg/capita, 1998) and one sixth of the world average i.e.18

kg/capita (Muthaa et al., 2006). This consumption led to more than 5400 tones of plastics

waste being generated per day in 2000/2001 and the percentage of plastics in municipal solid

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 10

waste (MSW) has also increased significantly from 0.7% in 1971 to 4% in 1995

(TERI,1998). Polyolefin account for about 60% of the total plastics consumption, followed

by PVC and polystyrene. Together, the commodity plastics (PE, PP, PVC and PS) accounted

for 83% of the total plastics consumption in India in 2000/2001. Between 1990 and 2000,

LLDPE was the material with the strongest growth rate of (20% /yr), followed by PP (16%

/yr), HDPE (14% /yr), PVC (12% /yr), PS (10% /yr) and LDPE (Muthaa et al., 2006).

Polyolefin account for the major share of 60% in the total plastics consumption in

India. Packaging is the major plastics consuming sector, with 42% of the total consumption,

followed by consumer products and the construction industry. This is similar to the situation

in Western Europe where packaging accounts for 37- 40% of the total plastics consumption

(APME, 2002; SGCCI, 2000; VKE, 2002). In the year 2000-01, the share of recycling

accounted for 47% of the total volume of waste generated including primary, secondary and

tertiary recycling (Muthaa et al., 2006). According to ICPE (2005) the per capita

consumption of the plastic is 4 kg in India whereas in china it accounts 18 kg while 20 kg in

the other developed nations. Recycling is highest in India that is 60 % while it comes only 20

% for the rest of the world.

Further, according to Muthaa et al. (2006) the consumption of plastics will increase

about six-fold between 2000 and 2030 and LLDPE, HDPE, PP will dominate in India due to

their versatility and cost benefits. PVC will grow very slowly because it will be replaced by

PP and HDPE. Due to the increasing share of long-life products in the economy, and

consequently in the volume of waste generated, the share of recycling will decrease to 35%

over the next three decades. The total waste available for disposal will increase at least 10-

fold up to the year 2030 from its current level of 1.3 million tones. This model result assumes

that the plastics recycling rates will remain at the current level for the next three decades.

However higher recycling rate improved waste management system still a strong

regulatory discipline is required in India because volumes of plastic waste will clearly rise in

the future as the per capita consumption of plastic products increases. Plastics waste

management, therefore, needs continued policy attention from both stakeholders:

Government and Industry. Some initiative examples are; Plastics Waste Management Task

Force established the Ministry of Environment and Forests in 1997 and the Indian Center for

Plastics and Environment (ICPE) that was established by the Indian plastics industry in 1999

(Muthaa et al., 2006).

Recently, Ministry of Environment and Forests issued a new gazette of rules (4th

Feb,

2011) known as Plastic Waste (Management and Handling) Rules, 2011. Some salient

features of these rules are; (a) No person shall use carry bags made of recycled plastics or

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 11

compostable plastics for storing, carrying, dispensing or packaging food stuffs. (b) No person

shall manufacture, stock, distribute or sell any carry bag made of virgin or recycled or

compostable plastic, which is less than 40 microns in thickness. (c) Sachets using plastic

material shall not be used for storing, packing or selling gutkha, tobacco and pan masala.

2.4 ISSUES RELATED WITH PLASTIC BAGS

Plastic grocery bags have been a part of daily life in developed countries since their

introduction in 1977 and in more recent years, their use has spread to many developing

countries as well (Williamson, 2003). Countless numbers of bags filling landfills and spilling

over every surface of the Earth (Chauhan, 2003; Thiel et al., 2003). This prevalence results in

several critical environmental and social impacts associated with their use and immediate

disposal. Plastic bags are also problematic in terms of the loss of agricultural potential and

impacts on tourism, in addition to the high cost of cleanup that falls to local and national

governments. In these regions, plastic bags are found everywhere, from remote tourist

destinations to city streets where they can clog drain pipes, contributing to massive flooding

that has already cost thousands of lives. In 2005, city Mumbai, India experienced massive

monsoon flooding, resulting in at least 1,000 deaths, with additional people suffering injuries

(The Asian News, 2005). City officials blamed the destructive floods on plastic bags that

clogged gutters and drains, preventing the rainwater from leaving the city through

underground systems. Similar flooding happened in 1988 and 1998 in Bangladesh that led to

the banning of plastic bags in 2002 (World Watch, 2004). By clogging sewer pipes, plastic

grocery bags also create stagnant water that produces the ideal habitat for mosquitoes and

other parasites that have the potential to spread a large number of diseases, such as

encephalitis and dengue fever, but most notably malaria (Edwards, 2000; World Watch,

2004).

Plastic also have the potential to leach their chemical components and toxins into soil

and water sources that can be passed on to humans, resulting in health dangers such as

neurological problems and cancers (Butte Environmental Council, 2001; Lane, 2003). Plastic

bags are mistakenly eaten by animals, leading to suffocation or blockage of digestive tracts,

and eventually death. South Africa, Kenya, Somaliland, and India are four nations that report

high levels of these problems, with as many as 100 cows dying per day in India (World

Watch, 2004; Edwards, 2000). Due to their propensity to be carried away on a breeze and

become attached to tree branches, fill roadside ditches or end up in public waterways, rivers

or oceans. In one instance, Cape Town, South Africa, had more than 3000 plastic grocery

bags that covered each kilometre of road (Ryan and Rice, 1996). In this century, an estimated

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 12

46,000 pieces of plastic are floating in every square kilometre of ocean worldwide (Baker,

2002). According to Williamson (2003) about 96 % of all grocery bags are thrown into

landfills. A bag can last up to 1000 years, inhibiting the breakdown of biodegradable

materials around or in it (Stevens, 2001). According to Matlack (2001) problems of air and

water pollution become more intensive in several countries with few environmental

regulations over plastic shopping bags that results in even greater impacts on the environment

and human health.

The ecological footprint of the plastic bag grows with each increasing statistic.

Australia alone imports 4 billion bags annually (Australian Bureau of Statistics, 2004).

Container ships used to transport these bags to each consumer country use fuels that produce

high levels of pollutants, such as sulphur (Long and Wagner, 2000). To illustrate, of the

estimated 4 to 5 trillion plastic bags produced per year, North America and Western Europe

account for nearly 80 %, with the U. S. that throwing away 100 billion plastic grocery bags

annually (Geographical, 2005; Murphy, 2005). Australia uses 7 billion plastic bags annually,

of that 53 per cent come from supermarkets (Australian Bureau of Statistics, 2004; Brown,

2003). The United Kingdom consumes between eight and 10 billion bags annually and in

Taiwan this number rises to 20 billion (Geographical, 2005).

2.5 PLASTIC FOOTPRINTS IN OCEANS AND IMPACT ON MARINE LIFE

Human activities are responsible for a major decline of the world‟s biological

diversity, and the problem is so critical that combined human impacts could have accelerated

present extinction rates to 1000–10,000 times the natural rate (Lovejoy, 1997). One particular

form of human impact constitutes a major threat to marine life: the pollution by plastic debris.

Plastics are synthetic organic polymers, and though they have only existed for just over a

century (Gorman, 1993). These threats to marine life are primarily mechanical due to

ingestion of plastic debris and entanglement in packaging bands viz. synthetic ropes and lines,

or drift nets Broken or discarded fishing gear, pellets, scrubbers, microplastics, films and

flakes (Gregory, 2009; Mallory et al., 2006; Thompson et al., 2004; Derraik, 2002; Moore et

al., 2001; Baird and Hooker, 2000; Blight and Burger, 1997; Laist, 1987, 1997; Quayle,

1992; Colton et al., 1974; Rothstein, 1973; Carpenter and Smith, 1972).

Plastic fragments on beaches are derived either (1) from inland sources and are

transported to coasts by rivers, wind, man-made drainage systems or human activity, or (2)

directly from the oceans where low density floating varieties accumulate and are transported

across great distances. (Corcoran et al., 2009) Floating plastic fragments in the world‟s

oceans have been reported since the early 1970‟s (e.g. Carpenter and Smith, 1972; Colton et

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 13

al., 1974), with the amount of debris showing a documented exponential increase (Ryan and

Moloney, 1993).

The majority of these items are non-biodegradable and can attract encrusting

organisms as drift plastics (Minchin, 1996; Gregory, 1983; Winston, 1982).Types and

amounts of plastic debris on beaches are controlled mainly by topography, current and storm

activity, proximity to litter sources and extent of beach use (Storrier et al., 2007). Surveys

carried out in South African beaches, showed that the densities of all plastic debris have

increased substantially (Ryan and Moloney, 1990). In Panama, experimentally cleared

beaches regained about 50% of their original debris load after just 3 months (Garrity and

Levings, 1993). Plastic pellets can be found across the Southwest Pacific in surprisingly high

quantities for remote and non-industrialised places such as Tonga, Rarotonga and Fiji

(Gregory, 1999). In New Zealand beaches they are found in quite considerable amounts, in

counts of over 100,000 raw plastic granules per meter of coast (Gregory, 1989), with greatest

concentration near important industrial centers (Gregory, 1977). Their durability in the

marine environment is still uncertain but they seem to last from 3 to 10 years, and additives

can probably extend this period to 30–50 years (Gregory, 1978). Since they are also buoyant,

an increasing load of plastic debris is being dispersed over long distances in marine

environments and beaches across the globe are littered with plastic debris. Items of plastic

have been reported from the poles to the equator (60–80 percent of marine litter being plastic)

(Oigman-Pszczol and Creed, 2007; Storrier et al., 2007; Thompson et al., 2004; Derraik,

2002, Gregory and Ryan, 1997). Even far and remote beaches (Subantarctic islands and

South Pacific) are becoming increasingly affected by plastic debris, especially fishinglines

(Walker et al., 1997; Benton, 1995)

In 1975 the world‟s fishing fleet alone dumped into the sea approximately 135,400

tons of plastic fishing gear and 23,600 tons of synthetic packaging material (DOC, 1990;

Cawthorn, 1989). Horsman (1982) estimated that merchant ships dump 639,000 plastic

containers each day around the world and ships are therefore, a major source of plastic debris

(Shaw, 1977; Shaw and Mapes, 1979). Recreational fishing and boats are also responsible for

dumping a considerable amount of marine debris, and according to the US Coast Guard they

dispose approximately 52% of all rubbish dumped in US waters (UNESCO, 1994).

Unfortunately, plastics do not degrade rapidly through mineralization, and may remain

in microscopic form indefinitely (Corcoran et al., 2009). Conventional plastics show high

resistance to aging and minimal biological degradation (O'Brine and Thompson, 2010) and

when they finally settle in sediments they may persist for centuries (Goldberg, 1995, 1997;

Hansen, 1990; Ryan, 1987). According to Kanehiro et al., (1995) plastics made up 80–85%

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 14

of the seabed debris in Tokyo Bay. The accumulation of such debris can inhibit the gas

exchange resulting hypoxia or anoxia in the benthos that can interfere with the normal

ecosystem functioning (Goldberg, 1994). In addition, chemicals including phthalates, PCB‟s

and organochlorine pesticides, reported in plastic fragments may present a toxicological

hazard (Teuten et al., 2009, 2007; Mato et al., 2001; Andrady et al., 1993). Dispersal of

aggressive alien and invasive species by these mechanisms leads one to reflect on the

possibilities that ensuing invasions could endanger sensitive or at-risk coastal environments

(both marine and terrestrial) far from their native habitats (Tourinho et al., 2010).

This plastic can affect marine wildlife in two important ways: by entangling creatures,

and by being eaten. However, the impact of plastic bags does not end with the death of one

animal; when a bird or mammal dies in such a manner and subsequently decomposes, the

plastic bag will be released into the environment to be ingested again by another animal

(Derraik, 2002). The problem may be highly underestimated as most victims are likely to go

undiscovered over vast ocean areas, as they either sink or are eaten by predators (Wolfe,

1987). Marine debris are affecting at least 267 species worldwide, including 86% of all sea

turtle species, 44% of all seabird species, and 43% of all marine mammal species (Laist,

1997). Some representative examples typifying the global spread of plastic ingestion

behaviour are red phalaropes (Connors and Smith 1982); 15 species of sea birds, Gough

Island, South Atlantic Ocean (Furness ,1985); Wilsons storm-petrels, Antarctica (Van

Franeker and Bell 1988); storm-petrels (Blight and Burger 1997); short-tailed shearwaters,

Bering Sea (Vlietstra and Parga 2002); southern giant petrels, Southern Atlantic Ocean

(Copello and Quintana, 2003); northern fulmars, Nunavut, Davis Strait (Mallory et al.,2006).

Most distressing, over a billion seabirds and mammals die annually from ingestion of plastics

(Baker, 2002). Brown (2003) mentioned that in Newfoundland 100,000 marine mammals are

killed each year by ingesting plastic.

2.6 ISSUES RELATED TO PLASTIC PRODUCTS MANUFACTURING

The manufacturing of plastic bags accounts for 4 per cent of the world‟s total oil

production (Greenfeet, 2004). The energy used to make one high-density polyethylene

(HDPE) plastic bag is 0.48 mega-joules. To give this figure perspective, a car driving one

kilometre is the equivalent of manufacturing 8.7 plastic bags (Australian Bureau of Statistics,

2004). If a country such as Ireland, with approximately 1.23 million shoppers, switched 50

per cent of plastic bag users to cotton, 15,100 tones of CO2 emissions would be saved per

annum. This is equivalent to one person driving around the world 1,800 times (Simmons,

2005). Two plastic bags require 990 kJ (kilojoules) of natural gas, 240 kJ of petroleum, and

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 15

160 kJ of coal (ILEA, 1990). Additionally, there are large amounts of energy used to acquire

oil, such as the large, fuel-burning heavy machinery, and most of the electricity used in the

process of manufacturing the actual bags comes from coal-fired power plants (Greenfeet,

2004).

Manufacturing process of plastic bags contribute to air pollution i.e. acid rain, smog

etc. Other harmful effects associated with the use of petroleum, coal, and natural gas, such as

health conditions of coal miners and environmental impacts associated with natural gas and

petroleum retrieval is a significant environmental impact. Additionally, the manufacturing of

plastic grocery bags produces waterborne waste, that has the capability of disrupting

associated ecosystems, such as waterways and the life that they support (Environmental

Literacy Council, 2005; ILEA, 1990; NPBWG, 2002).

Toxic chemicals that are most frequently released during the production of plastics

include trichloroethane, acetone, methylene chloride, methyl ethyl ketone, styrene, 3 toluene,

and benzene (IFC, 2009). Other major emissions are sulfur oxides, nitrous oxides, methanol,

ethylene oxide and volatile organic compounds (NSEPB, 1987). Benzene is believed to be

extremely toxic while a cause of cancer. Sulfur oxides are known to harm the respiratory

system, nitrous oxides adversely affect the nervous system and child behavioral development

and ethylene oxides harm the male and female reproductive capacity (Xiao and Levin, 2000;

IARC. 1998; Schaumburg, and Spencer, 1978; Seppäläinen and Tolonen 1974).

2.7 PLASTIC WASTE SCENARIO (QUANTITY AND COMPOSITION)

The dramatic increase in production and lack of biodegradability of commercial

polymers, particularly commodity plastics used in packaging (e.g. fast food), industry and

agriculture, focused public attention on a potentially huge environmental accumulation and

pollution problem that could persist for centuries (Albertsson et al., 1987). Moreover, the

problem of wastes cannot be solved by landfilling and incineration, because suitable and safe

depots are expensive, and incineration stimulates the growing emission of harmful,

greenhouse gases, e.g. NOx, SOx, COx, etc. (Miskolczia et al., 2004). The same as in

wealthy countries, light-weight and dirty plastics products (e.g. packaging films) are disposed

of in India together with the normal household waste (without reimbursement). The major

part of this waste stream is either dumped on landfill sites or remains in the environment

where it is the main contributor to littering. A minor part of this light-weight and dirty

plastics waste is suitable for recycling and is collected in various stages via various

middlemen; it ultimately finds its way to the preprocessors (Muthaa et al., 2006)

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 16

Since they are also buoyant, an increasing load of plastic debris is being dispersed over

long distances, and when they finally settle in sediments they may persist for centuries

(Goldberg, 1995, 1997; Hansen, 1990; Ryan, 1987). Clearly indicates the predominance of

plastics amongst the marine litter, and its proportion consistently varies between 60% and

80% of the total marine debris (Gregory and Ryan, 1997). Kikuchi et al. (2006) reported

following statistic data of composition of post-user plastic wastes (municipal waste and

industrial waste) in Europe; 32.9% low density polyethylene (LDPE), 14.1% high density

polyethylene (HDPE), 11.6% polypropylene (PP), 11.0% polyvinyl chloride (PVC), 8.7%

polystyrene (PS), 5.7% polyurethane (PU), 3.6% polyethylene terephtalate (PET), 2.5%

acrylonitrile butadiene styrene (ABS) and others.

Environmental health costs associated with a plastic product life cycle could reveal the

true costs of plastic bag consumption. Western nations have infrastructures that are able to

deal well with waste and recycling; generally do not feel the same effects of plastic bags in

the environment like underdeveloped countries (Spivey, 2003). However, this is far from the

case in developing nations where waste management is not well established or is non-existent

(Environmental Literacy Council, 2005). The effects of plastic bags are most severely felt in

poor and rural areas, where shopping bags are dispensed and used widely but not disposed off

properly (Reynolds, 2002). The footprint of plastic grocery bags also includes high civic

costs to governments, most of that are incurred through clean-up efforts. Plastic bags can

litter roads, sewers and waterways, making litter collection and disposal difficult and costly

(NPBWG, 2002; Reynolds, 2002; Ryan and Rice, 1996; World Watch, 2004). High costs are

being shouldered by governments and taxpayers that result in the loss of funds from other

services offered by the government. Because of this myriad of problems, many governments

have banned plastic grocery bags entirely or imposed levies on their use (The Asian News,

2005; Environmental Literacy Council, 2005; World Watch, 2004).

2.8 FACTS RELATED TO DEGRADATION OF PLASTIC

As a known fact, sustainability requires that a degradable material breaks down

completely by natural processes so that the basic building blocks can be used again by nature

to make a new life form (Gautam, 2009).

Plastics made from petrochemicals are not a product of nature and cannot be broken

down by natural processes. Also, there is no data presented about complete biodegradability

within the one growing season/one year time period. It is assumed that the breakdown

products will eventually biodegrade. In the meanwhile, these degraded, hydrophobic, high

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 17

surface area plastic residues migrate into the water table and other compartments of the

ecosystem causing irreparable harm to the environment (Gautam, 2009).

PE is a synthetic polymer with -CH2-CH2- repeating units in the polymer backbone.

Among different types of synthetic polymers, PE is considered to be highly resistant to

biodegradation. Several features of PE have been identified to make it resistant to

biodegradation: (1) highly stable C-C and C-H covalent bonds, (2) higher molecular weight

(MW) of PE polymer, that makes them too big to penetrate cell walls of microbes, (3) lack of

readily oxidizable and/or hydrolyzable carbonyl, amide, and C=C double bond groups etc. in

the polymer backbone, (4) lack of chromophores that can act as catalysts for synergistic

photo and biodegradation, and (5) highly hydrophobic nature. Because of these features, PE

has been considered almost inert to biodegradation and a literature review revealed differing

views among authors regarding whether to consider PE as a biodegradable polymer or not

(Gautam et al., 2007).

Some plastic articles may take 500 years to decompose (Gorman, 1993; UNESCO,

1994). Due to the long-life of plastics on marine ecosystems, it is imperative that severe

measures are taken to address the problem at both international and national levels, since

even if the production and disposal of plastics suddenly stopped, the existing debris would

continue to harm marine life for many decades (Derraik, 2002).

Synthetic polyolefins are inert materials whose backbones consist of only long carbon

chains. The characteristic structure makes polyolefins non-susceptible to degradation by

microorganisms. It takes several centuries until it is efficiently degraded (except when

exposed to UV from sunlight) (Yamada et al., 2001). Introduction of microorganisms for the

specific digestion of polymer materials is another more intensive approach that ultimately

costs more but it circumvents the use of renewable resources as biopolymer feed-stocks.

Although microorganisms are researched to target and breakdown petroleum based plastics

but this method only reduces the volume of waste and does not help in the preservation of

non-renewable resources (Andreopoulos, 1994).

According to Yamada et al. (2001) degradation always follows photo degradation and

chemical degradation. Otake et al. (1995) reported the changes like whitening of the

degraded area and small holes on the surface of PE film after soil burial for 32 years.

Biodegradation of LDPE film was also reported as 0.2% weight loss in 10 years (Albertsson,

1980). Polyvinyl chloride (PVC) is a strong plastic that resists abrasion and chemicals and

has low moisture absorption. There are many studies about thermal and photodegradation of

PVC (Braun and Bazdadea, 1986, Owen, 1984) but there only few reports available on

biodegradation of PVC.

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 18

In Europe, some countries allow the addition of paper and biodegradable polymers to

the bio-waste fraction (Venelampi et al., 2003). Wilde and Boelens (1997) have proposed

three characteristics of bioplastics and/or paper that would render them suitable for use in

composting and organic recovery. These characteristics are: biodegradation, disintegration

and no effect on compost quality.When plastics are exposed to UVB radiation in sunlight and

the oxidative and hydrolytic properties of the atmosphere and seawater, polymers can be

oxidized, forming hydroperoxides that lead to polymer chain scission (Billingham et al.,

2000). However, these would require further degradation before they would become bio-

available. The mineralization rate from long-term biodegradation experiments of both UV-

irradiated samples (Albertsson and Karlsson, 1988), In addition, the burning of

polyvinylchloride (PVC) plastics produces persistent organic pollutants (POPs) known as

furans and dioxins (Jayasekara et al., 2005).

On the other hand, it is important to have comparable international standard methods

of determining the extent of biodegradation. Unfortunately, the current standards have not, so

far, been equated to each other and tend to be used in the countries where they originated

[e.g. ASTM (USA), DIN (Germany), JIS (Japan), ISO (international standards), CEN

(Europe)]. Many, that are otherwise harmonious, differ in the fine details of the testing. There

is an urgent need to standardize all details so that researchers may know that they have all

worked to the same parameters (Shah et al., 2008).

2.9 PROBLEMS IN RECYCLING AND INCINERATION OF PLASTIC GARBAGE

According to conventional economics, recycling does economically efficient if it costs

more to recycle materials than to send them to landfills or incinerators. Many critics also

point out that recycling is often not needed to save landfill space because many areas are not

running out of it (Tierney, 1996). It is hard to understand why recycling is held to a different

standard and thus forced to cover its own costs. As well, the lower charges for depositing

wastes in landfills in North America and the lower prices paid for recycled plastic shows that

recycling is not a priority for most governments, businesses and individuals, causing grave

consequences around the globe (Porter, 2000). An ecoprofile analysis shows that the

incineration of plastics with heat recovery is the most environmentally friendly and resource

compatible process if it is not technically and economically easy to sort different types of

plastic material (Kikuchi et al., 2008).

McKinney and Schoch (2003) discussed three reasons that affect the recycling rates of

plastic bags. First, plastics are made from many different resins, and because they cannot be

mixed, they must be sorted and processed separately. Such labour-intensive processing is

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 19

expensive in high-wage countries like the United States and Canada. Most plastics also

contain stabilizers and other chemicals that must be removed before recycling. Second,

recovering individual plastic resins does not yield much material because only small amounts

of any given resin are used per product. Third, the price of oil used to produce petrochemicals

for making plastic resins is so low that the cost of virgin plastic resins is much lower than that

of recycled resins (Miller, 2005). Hence, recycling is not a simple solution to lessen the

ecological footprint of the plastic encroachment.

Recycling can be divided into further important categories, such as mechanical

recycling and chemical recycling. Chemical recycling is virtually a thermal method that

yields a liquid with high sulphur and nitrogen content. This is a disadvantageous property for

further utilization (Miskolczia et al., 2004). However, with used thin films, recovery is often

not economically feasible, more oil being used to provide the energy for collection and

sorting from other refuse than is saved by the recovery of the plastics material (Philip et al.,

1993). Although it is important to individually separate various types of waste plastic with a

high accuracy, it must also be environmentally helpful to sort mixed waste plastics according

to their final destination (waste-to-energy application or landfilling) by a simple approach.

Without proper measures, there may be no alternative but to dump them at a landfill. The

plastic densities change with the order PVC > PET > PU> PS > ABS > PE > PP. The number

of floatable plastics increases with an increase in the liquid density. After pre-sorting by the

current process, the mixed waste plastics contain 2.2% Cl. If these plastics are combined with

a waste-to-energy project the Cl content is too great for the same (Kikuchi et al., 2008).

However, mechanical recycling has some limitations. Firstly, the recycled plastics lose

their properties steadily and their final appearance is different. Besides, small contaminations

by other polymers give low quality plastics because of the material incompatibility, and

therefore they can only be used in lower-quality applications. Finally, mechanical recycling is

limited to thermoplastics (Aguado et al., 2006). However, recycling appeared to be a viable

way to reduce pollution and environmental damage when it was first introduced as a waste

reduction technique but use of plastics that are compostable or easily degraded must be

encouraged to reduce toxic emissions when plastic material is recycled or decomposed

(Kolybaba et al., 2003).

With regard to recycling the situation is very specific in India since the percentage of

plastics recycling is much higher than that in most developed and in many developing

countries e.g. China 10%, South Africa 16%, compared to ~ 47% in India (Muthaa et al.,

2006). The recycling sector in India has developed autonomously because of the particularly

low cost of labour and on account of the fairly large market for second-grade (lower-quality)

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 20

products. Recycled products are available at a 20–40% lower price than the same products

manufactured from virgin plastics. The cost per hour in India (according to report issued by

the Plast India Foundation) is 35 times less than in Germany, 19 times less that in the United

States and 6 times less than in Taiwan (NetPEM, 2001).

The pollution that occurs in the disposal stage is largely during incineration. A large

amount of plastic wastes is burnt in incinerators and burning of these chlorine-containing

substances releases toxic heavy metals and emits noxious gasses like dioxins and furans. The

latter two are two of the most toxic and poisonous substances on earth and can cause a variety

of health problems including damage to the reproductive and immune system, respiratory

difficulties and cancer. In fact, dioxin has been shown to have hormonal activity and is an

endocrine disrupt or disruptor (Hicks et al., 2005). On the other hand Incineration coupled

with energy recovery, that has received great support from the industry and Government in

India, could minimize the immediate waste disposal problems in India; but this could also

aggravate pollution problems if strict standards are not enforced. Further there are huge costs

associated with incineration, if it has to be profitable and carried out in an environmentally

friendly manner. Another key aspect is composition of municipal solid waste in India. The

waste has a very low calorific value and additional fuel is required to carry out incineration

effectively. This would further add to the costs associated with incineration. Another

important complication arising from introduction of incineration in India is that it may

adversely affect the recycling industry (Narayan, 2001).

2.10 BIODEGRADABLE POLYMERS AND BIO-PLASTIC (ISSUES AND SCOPE)

As a known fact, sustainability requires that a degradable material breaks down

completely by natural processes so that the basic building blocks can be used again by nature

to make a new life form. Plastics made from petrochemicals are not a product of nature and

cannot be broken down by natural processes hence the use of biodegradable is the need of the

hour to implement immediate application for biodegradable plastics (Gautam, 2009).

Marlet (2004) has shown that plastic bags are preferable to paper bags throughout their

life cycle due to lower energy needs for production and environmental pollution. Hill (2005)

was unable to show significant advantages or disadvantages of bags produced from one type

of plastic over those made from other kinds of plastic, including recyclable material (Ayalon

et al., 2009). Furthermore, comparison with the paper bag alternative, which is accepted by

the public as the „„greener” choice, reveals that the paper bag uses almost 10 times as much

material as that needed to produce a single-use plastic bag. The production process also

requires the use of cellulose derived from trees an important environmental resource for

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 21

sequestering greenhouse gasses. Moreover, the process of producing paper bags demands the

use of larger volumes of water than plastic bags and the degradation process of paper bags in

landfills releases greenhouse gasses. No difference was found between plastic and

biodegradable bags in reference to the problems associated with a whole life cycle, and both

these alternatives are preferable to the paper bag alternative (DEHA, 2002).

The great advantage of bioplastic is the conservation of fossil resources and reduction

in CO2 emissions. It makes them one of the most important innovations for sustainable

development. Plastics, with their current global consumption of more than 250 million tonnes

consume 5% crude oil. This consumption may appear comparatively small, however it does

emphasise how dependent the plastics industry is on oil. Making, disposal and recovery of

bioplastics have the additional advantage of using renewable resources. According to IBAW

(2004), the use of biodegradable plastics has doubled between 2001 and 2003 to 40,000

tonnes.

So far the paper and board sector has been by far the largest bio-polymer producer. Its

world-wide production amounted to approximately 365 million metric tonnes (Mt) in 2006

(FAO, 2008). Non-food starch (excluding starch for fuel ethanol), cellulose polymer and

alkyd resins are also important bio-polymers but they are much smaller in terms of

production volumes. In total, they account for approximately 20 Mt /yr, of that non-food

starch takes the lion‟s share (75% or 15 Mt), followed by cellulose polymers (20% or 4 Mt,

excluding paper) and alkyd resin (5% or 1 Mt) (Shen et al., 2009).

Bioplastics (Biopolymers) obtained from growth of microorganisms or from plants that

are genetically-engineered to produce such polymers are likely to replace currently used

plastics at least in some of the fields (Lee, 1996). The global interest in PHAs is high as it is

used in different packaging materials, medical devices, disposable personal hygiene and also

agricultural applications as a substitute for synthetic polymers like polypropylene,

polyethylene etc. (Ojumu et al., 2004).

2.10.1 Types of Biodegradable Plastics

According to Shen et al., (2009) there are three principal ways to produce bio-based

plastics,

i) To make use of natural polymers which may be modified but remain intact to a large

extent (e.g. starch plastics)

ii) To produce bio-based monomers by fermentation or conventional chemistry and to

polymerize these monomers in a second step (e.g. polylactic acid)

iii) To produce bio-based polymers directly in microorganisms or in genetically modified

crops.

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 22

Naturally occurring biopolymers are derived from four broad feedstock areas Animal

sources provide collagen and gelatin, while marine sources provide chitin that is processed

into chitosan, are the most promising source for future development and expansion. Many

naturally occurring organisms (plant and animal) have potential to be modified and employed

as biopolymers. Microbial biopolymer feedstocks are able to produce polylactic acid (PLA)

and polyhydroxy alkanoates (PHA). The remaining two categories are the agricultural feed-

stocks. This variety of polymers falls into the categories of hydrocolloids, and lipids and fats.

Starch is an agricultural feedstock that is a hydrocolloid biopolymer (Martin et al., 2001;

Salmoral et al., 2000; Chandra and Rustgi, 1998). Amylose, the linear polymer, comprises

approximately 20% w/w of starch while amylopectin, the branched polymer, constitutes the

remain (Tharanathan, 2003).

Plastics can be made from other glucoseintensive materials such as potato scraps, corn,

molasses, and beets (Kings et al., 1992; Sharpley and Kaplan, 1976). As cornstarch is a

native agricultural product, replacement of petroleum-based plastics with starch-based

plastics could reduce our need to import petroleum or could conserve petroleum for other

uses. Starch is totally biodegradable. Degradation or incineration of starch in plastics would

recycle atmospheric CO2 trapped by the corn plant and would not increase potential global

warming (Swanson et al., 1993). Starch in many ways, as a filler and bonding agent as well

as a strengthen additive, is a good objective for the research in the making and development

of biodegradable materials (Andersen and Hodson, 2001; Yoo et al., 1995). Recently, starch

graft copolymers, starch-plastic composites and starch itself have been proposed as plastic

materials (Swanson et al., 1993). Natural filler materials may be incorporated into synthetic

plastic matrices as a rapidly biodegradable component. Often, granular starch is added to

polyethylenes in order to increase the degradation rate of the plastic material (Kolybaba et al.,

2003). Glycerol is often used as a plasticizer in starch blends, to increase softness and

pliability. Starch granules that have been plasticized with water and glycerol are referred to as

plasticized starches (Martin et al., 2001). Plastic materials that are formed from starch-based

blends may be injection molded, extruded, blown, or compression molded (Kolybaba et al.,

2003).

Cellulose has a very long molecular chain, which is infusible and insoluble in all but

the most aggressive solvents (Chandra and Rustgi, 1998). Therefore, it is most often

converted into derivatives to increase solubility, that further increases adhesion within the

matrix (Kolybaba, et al., 2003). Flax fibers continue to receive the majority of the

consideration of Canadian researchers, as they are mechanically strong and readily available

as agricultural by product or waste (Kolybaba et al., 2003). Chemical treatment (acetylation)

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 23

of the fibers is performed in order to modify the surface properties, without changing the

fiber structure and morphology (Frisoni et al, 2001). Bledzki and Gassan (1999) concluded

that fibers that have been thoroughly dried prior to being added to the matrix show improved

adhesion as opposed to fibers with a higher moisture content. Research has shown that

polyvinyl alcohol is an appropriate polymer to use as a matrix in natural fiber reinforced

composites, as it is highly polar and biodegradable (Chiellini et al., 2001).

Due to similar material properties to conventional plastics the biodegradable plastics

(polyesters), namely polyhydroxyalkanoates (PHA), polylactides, polycaprolactone, aliphatic

polyesters, polysaccharides and copolymer or blend of these, have been developed

successfully over the last few years. The most important are poly(3-hydroxybutyrate) and

poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (Hocking and Marchessault, 1994;

Steinbuchel and Fuchtenbusch, 1998).

2.10.2 Economical Aspects of Biodegradable Plastic /Polymers

Bio-based plastics represent an emerging, very dynamic field with a very positive

development potential for the future. Bioplastics development is just beginning. Their market

share is currently well under one percent. The market is growing and in many application

areas e.g. packaging or agricultural films, the number and quantity are increasing

dramatically. Today, the combined volume of these non-food non-plastics applications of

starch and man-made cellulose fibers is 55 times larger than the total volume of the new bio-

based polymers (approx. 20 Mt versus approx. 0.36 Mt in 2007). The new bio-based

polymers may reach this level in 20-30 years from now. The use of starch for paper

production only amounts to 2.6 Mt and is hence still seven-folds larger than today‟s

worldwide production of bio-based plastics. By 2013, the world-wide capacity of bio-based

plastics could increase to 2.3 Mt and by 2020 to 3.5 Mt. (Shen et al., 2009). Starch is

inexpensive (about 10 cents/lb) and is available annually in multimillion ton quantities from

corn produced in excess of current market needs in the United States (Swanson et al., 1993).

Bio-based and biodegradable plastics are a very promising innovation for both industry

and the economy. The recommended products, that may be made out of compostable /

biodegradable plastics, are Agricultural Mulch Film, Nursery Bags, Garbage Bags / Wet

Waste Disposal Bags, Special Food Wraps, Coating on Paper/Jute/Textile, specialized fishery

items, plastic water bottles to be carried during expedition in mountains, cutlery to be carried

in boats / ships / trains, foam packaging products medical sector etc. Bioplastics sector

registers continuous growth: As estimated by IBAW, pan-European consumption of

bioplastics in 2003 was at 40,000 tons. This indicates that consumption has doubled from

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 24

2001. Especially in Great Britain, Italy and the Netherlands the market development was

dynamic (ICPE, 2010).

All over the world, industries are using various systems to manufacture biodegradable

bags. Om-Bioplast Ltd in Pune (India) uses carbohydrates to manufacture plastic that

disintegrate under UV radiation and also degradable by microorganisms. ECOSAC LTD,

official supplier of Ecosac Biodegradable/Compostable Packaging in the UK and Ireland. In

the US, BIO Group USA is the sales partner for Europe‟s major manufacturer of 100%

biodegradable and 100% compostable „„plastic‟‟ bags and films produced from cornstarch

(Mohee and Unmar, 2007).

According to Shen et al. (2009) the market of emerging bio-based plastics has been

experiencing rapid growth. From 2003 to the end of 2007, the global average annual growth

rate was 38%. In Europe, the annual growth rate was as high as 48% in the same period.

There are very large opportunities for the replacement of petrochemical by bio-based plastics.

World-wide, bio-based plastics add up to a total production capacity of 0.36 Mt in 2007 and

to 1.5-4.4 Mt in 2020. In terms of size, both small and medium enterprises (SMEs) and large

companies are active in the area of bio-based plastics. In most cases the SMEs were the

pioneers that made the first steps in technology development, production and

commercialization. These SMEs have partly grown to a remarkable size in the last ten years.

Successful reconstruction of the chemical industry using bio-based feed-stocks can be seen as

Third Industrial Revolution. The progress made in bio-based plastics in the past ten years is

very impressive. Also in research and development major activities are ongoing, contributing

to the increased attractiveness of chemical sciences and chemical technology for a new

generation of scientists and engineers. Even by 2020, the European production of biobased

plastics is projected not to exceed 2 kg per capita, while petrochemical plastics may amount

to 166 kg per capita (the current values are 0.27 and 103 kg per capita respectively). On the

other hand, the advantages of the slow substitution of petrochemical plastics are that

technological lock-in.

The concept of biodegradable plastics is new in India and research is still in

preliminary stage in the development of biopolymers due to higher cost and lack of

initiatives. The cost of biodegradable plastics is 2- 10 times more than conventional plastics

e.g. Oxo/Photo Degradable plastics film / bags - Rs.90 to 120 per kg and Biodegradable

plastics film / bags - Rs.400 to 500 per kg (Gautam, 2009).

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 25

2.10.3 Decomposition of Biodegradable Plastic/Polymers

The decomposition of the biodegradable material sharply depends on the condition

provided (open heap, land-filling, different type of normal or controlled decomposing).

Decomposition rate varies with many factors like humidity, temperature, aerobic or anaerobic

conditions, depending on the formulation used, and the microorganisms required. Even the

material that is subjected to decomposition itself has its different susceptibility towards

decomposition. Polymers that are based on naturally grown materials (such as starch or flax

fiber) are susceptible to degradation by microorganisms (Kolybaba et al., 2003). When

biodegradable material (e.g. starch or cellulose) is used as an additive to a conventional

plastic matrix, is attacked by the microbes. The microbes start to digest the starch and when

the starch component has been depleted, the polymer matrix begins to be degraded by an

enzymatic attack results in the slowly reduced weight of the matrix until the entire material

has been digested (Huang et al., 1990). In an experiment Philip et al. (1993) tested some 33

different commercial formulations of polythene containing starch as an additive in five

different natural and seven different laboratory-model environments combinations, at time

intervals of up to one year. It was founded that of the 232 plastics/environments/time

combinations, fewer than 10% showed statistically significant degradation and

biodegradation tended to be faster in those with a high starch. As the microorganisms utilize

or remove the starch present in the polymer there would be some physical or mechanical

damage on the specimen (Austin, 1991). The process is called depolymerization. When the

end products are CO2, H2O, or CH4, the degradation is called mineralization (Hamilton et al.,

1995; Frazer, 1994).

It is important to note that biodeterioration and degradation of polymer substrate can

rarely reach 100% and the reason is that a small portion of the polymer will be incorporated

into microbial biomass, humus and other natural products (Atlas and Bartha, 1997; Narayan,

1993). The evaluation of visible changes in plastics can be performed in almost all tests.

Effects used to describe degradation include roughening of the surface, formation of holes or

cracks, de-fragmentation, changes in color, or formation of bio-films on the surface. These

changes do not prove the presence of a biodegradation process in terms of metabolism, but

the parameter of visual changes can be used as a first indication of any microbial attack (Shah

et al.,2008). Many biopolymers are designed to be discarded in landfills, composts or soil.

The materials will be broken down, provided that the required microorganisms are present.

Normal soil bacteria and water are generally all that is required, adding to the appeal of

microbial reduced plastics (Selin, 2002).

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 26

2.10.4 Problems and Challenges

Products must be developed that satisfy real needs of the public. Performance must

meet public expectations and costs must be competitive to those of extant plastic materials

used for the same applications. Study of the influence of compounding variables on

morphology, physical properties, and biodegradability can provide basis for tailoring

properties of starch plastics to fit specific applications Lower material performance of some

bio-based polymers e.g. starch-based materials fell short in strength and impact properties is

also a big challenges that need to be successfully addressed (Swanson et al.,1993).

On the other hand, high cost for production and processing is major obstacle for the

development and establishment of biodegradable objects e.g. the cost of starch in Europe is

clearly higher than in the US. However, according to Shen et al. (2009) further, for starch

blends, the main cost component is the modification of starch and this area is of great thrust

for considerable for improvement. Use of agricultural land and forests, with maintaining

economical viability against the food production demand will be a limiting factor if bio-based

products increase in next decades. Adverse effects on biodiversity will be the other

environment and ecological issues.

As bio-polymers are modified for the bio-plastic purpose or incorporated with the

traditional non-degradable plastic, sustainable disposal, biodegradation and recycling of these

semi-biodegradable hybrids are another environmental, economical and technical concern

(Swanson et al., 1993).

2.11 CITATION OF RELEVANT PATENTS

Many inventions and research related to developments of different types of

biodegradable containers are compiled and registered as patents. Here examples of some

patents, mainly those of relevant to substitutes of polybags or useful for nursery purposes, are

cited;

Biby et al. (2001) documented a patent, entitled “Water resistant degradable foam

thermoformed sheet”, in that making of such foam that is the extrudate of a mixture of a

biodegradable polymer, starch, talc, and a blowing agent is provided. This foam is water-

resistant and in some variations waterproof making it an effective packing material that is

biodegradable, and thus, it can be disposed. In addition, the foam may be extruded into sheets

to form various articles. „Biodegradable cellulosic material and process for making such

articles‟, is another patent by Wyatt and Wyatt (1994). In this patent a process is described

for making a shaped biodegradable cellulosic article from cellulose-containing material

having a water content of less than about 50 percent by weight.

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 27

In his patent no. 7036272, Hermann (2006) disclosed a plant container consisting of

decayable and ecologically safe materials is collapsible and assembled from its parts

consisting of a pre-cut casing and a bottom made of dimensionally stable wire mesh or

biologically degradable plastic and a decayable organic material attached. The plant container

can be inexpensively transported and easily assembled just before it is put to use. It is

permeable to water and air, prevents the accumulation of wetness, root rot and mildew,

hinders the formation of spiraling roots and promotes a safe growth of the plant. The plant

container is robust and dimensionally stable and therefore suited for use with planting

machines. Patent No: 246163 entitled „Molded starch-bound containers and other articles

having natural and/or synthetic polymer coatings‟ by Simon (1999) described suitable

inorganically filled mixtures are prepared by mixing together a starch-based binder, a solvent,

inorganic aggregates, and optimal admixtures, e.g., fibers, mold-releasing agents, rheology-

modifying agents, plasticizers, coating materials, and dispersants, in the correct proportions

to form an article that has properties similar to articles as paper, paperboard, polystyrene,

plastic, or other organic materials and useful particularly in food and beverage containers.

Invention entitled as „Biodegradable or compostable containers‟ patented by Joe and

Christine (2003), provides an improved method and materials for biodegradable containers

using of a pre-gelled starch suspension that is unique in its ability to form hydrated gels and

to maintain this gel structure in the presence of many other types of materials and at low

temperatures. Patent no. 3852913, „Shaped biodegradable containers from biodegradable

thermoplastic oxyalkanoyl polymers‟ by Clendinning et al. (1974) disclosed the shaped

containers fabricated from material comprising biodegradable thermoplastic oxyalkanoyl

polymers, e.g., epsilon-caprolactone polymers, said containers possessing a medium to

germinate and grow seed or seedling, and optionally, a seed or seedling in such medium. The

resultant of scientific work entitled „Peat containers for the planting of containerized‟ by

William (1976) (Patent No: 3990180) describes manufacturing of an article that involves a

plug shaped receptacle or hollow container made of peat, pre-shaped and reacted at

conditions of temperature and pressure sufficient to cause reaction and polymerization of the

naturally occurring functional groups of the peat.

Theuer (2005) disclosed a research as „Plant pot that fertilizes when it biodegrades‟,

regarding a bio-pot that improves on present bio-pots in three ways. First, the current

invention remains sturdy until it and the growing plant it contains are transplanted into the

ground. This sturdiness is the result of a thin coating on the interior and exterior bottom of the

bio-pot that protects the pot from biodegradation before it is transplanted. Second, the current

invention competes in price with pots made from traditional petroleum-based plastic. Finally,

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 28

the invention improves plant growth that results after transplantation and the invention

biodegrades releasing the unique ingredient alluded to above, fertilizer.

The invention „Biodegradable container for liquid and/or semi-solid products united‟

by Dayton and Park (2010) provides methods and systems for constructing a container for

storage and transport and may be entirely biodegradable and/or recyclable. The body of the

container and/or bottle may be manufactured from paper pulp and assembled from a plurality

of dissimilar parts made of a biodegradable plastic resin and assembled to form a container

and/or bottle. The paper pulp may be treated inside and outside to make it water and air tight

but when exposed to extreme biodegrading influences it may breakdown into compostable

material. Other way is that it may be recycled again. In their patent named „Hydrophobic

biodegradable cellulose containing composite materials‟ Ioelovich and Figovsky (2001)

disclosed a invitation related to the field of manufacturing waterproof and biodegradable

cellulose containing composite materials like paperboard, cardboard and other cellulose

containing materials using natural polymers starch and its derivatives, dextrin, alginates,

lecithin, casein, gelatin, soybean protein and some synthetic polymers like methyl-

carboxymethyl- or hydroxyethyl-cellulose, polyvinyl alcohol, polyacrylic acid and other

hydrophilic polymers or their combinations used for manufacturing of cellulose composite

materials, like sized and coated paper, paper-and cardboard etc. It is well known to add

hydrophilic polymers to the pulp for sizing of cellulose material. The hydrophilic polymers

are also used for coating the surface of cellulose materials. The coated cellulose materials are

in fact composites and since the material of coating is biodegradable such composites are

environmentally friendly. The disadvantage of such composites is associated with the fact

that they are hydrophilic and not stable against humidity, water and aqueous solutions.

Invention named „Container‟ patented by Single (2005) relates to containers for

transporting plants. The invention relates to an easily assembled container to allow access to

inspect the root ball of a plant within the container. In this plant containers side walls and

base have holes or apertures that permit air to circulate around the container. This feature

facilitates air pruning of the roots as the root structure expands by virtue of the plant growing

in the container. Such a plant growth container and air pruning feature is also disclosed in

U.S. Pat. No. 5,099,607 entitled „Plant growth container‟ by Lawton (1992). This patent

discloses a container in that plants are to be grown and comprises of a flexible rectangular

section of material moulded into a lattice of recesses and corresponding protuberances. Roots

are guided into the recesses that converge to holes providing the air interface for air pruning

to take place. This plant growth container has the advantages of being easily adaptable in

diameter and is reusable.Similar plant growth container is also disclosed patent no. 4,939,865

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 29

named „Method and container for growing transplantable plants‟ by Whitcomb and Stephens

(1990). This patent describes a container comprising a set of upwardly extending removably

joined side panels having a lattice of protuberances and corresponding recesses converging to

holes. Whitcomb (2010) also presents patent entitled as „Plant container and method‟ with an

improved container and method for growing a plant to be subsequently transplanted. Another

patent no. 7481025 by Whitcomb (2009) also disclosed same type of plant container provided

with the facility for proper lateral root development.

Patent nos. 4,863,655 („Biodegradable Packaging Material and method of preparation

thereof‟ by Lacourse and Altieri, 1989) and 5,362,776 (Molded biodegradable packaging, by

Hornstein, and Landrum, 1998) disclose preparation of cellulose composite materials for

packaging that comprise cellulose fibers and hydrophilic binders like starch, gelatin,

polyvinyl alcohol, polyethylene glycol and polyethylene oxide. Despite these materials are

biodegradable they are not sufficient waterproof. Cellulose composite materials having

various hydrophobic protected coating layers have been proposed. Such protected coatings

contain various compounds, e.g. polyolefin and additives (Patent no. 5,296,307 by Bernstein,

1994, entitled „Laminated paper polyolefin paper composite‟) copolymers of olefins and

unsaturated carboxylic acids and pigments (Patent no. 3,970,629 by Izaki et al., 1976, entitled

„Composition for paper coating‟) a mixture of polyvinyl chloride and ethylene-acrylic

copolymer (Patent no. 4,365,029 entitled „Integral overwrap shield‟ by Frangipane et al.,

1995).

Patent nos. 3,985,937 ‘Method of forming a strengthened bond in a paperboard product

and products therefrom‟ by Culhane et al. (1995), 4,117,199 entitled „Process for producing

moisture and water-proof paper‟by Gotoh et al. (1978), 4,395,499 by Rosenski and

Fernandez (1983) entitled „High strength pigment binders for paper coatings containing

carboxylated vinyl ester alkyl acrylic interpolymers‟, 4,599,378 entitled „Vinyl

acetate/ethylene copolymer emulsions for paper coating compositions‟ by Hausman et al.

(1985), 5,763,100 entitled „Recyclable acrylic coated paper stocks and related methods of

manufacture‟ by Quick et al. (1998) and 5,744,547 entitled „Processes for producing vinyl

acetate polymer and saponified product of vinyl acetate polymer and resin composition‟ by

Moritani et al. (1998) are disclosed hydrophobic coatings for protection of cellulose

substrates containing aqueous latex of synthetic rubbers, polyvinyl esters, polyacrylates,

various copolymers, paraffin wax, organically acids, fillers and some other additives. The

coatings were applied on cellulose substrate in a form of aqueous latex and dried then. These

cellulose composite materials are waterproof, however their biodegradability is not sufficient

and therefore they cause pollution.

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 30

There are known also papers treated by silicon organic substances e.g. Patent nos.

3,856,558 entitled „Apparatus for treating cellulosic fiber-containing fabric to improve

durable press and shrinkage resistance‟ by McClain and Shattuck (1996) and 4,349,610

entitled „Method for waterproofing paper‟ by Parker (1982). Ioelovich and Figovsky (2001)

stated that these coated papers are sufficiently waterproof however they are bio-stable and

thus polluted the environment.

2.12 COMMERCIALLY AVAILABLE BIODEGRADABLE PRODUCTS

DOTPOT is a company of Arcadia that provides 100% organic and 100%

biodegradable pots for nursery purposes (Dotpot, 2010). These pots are claimed to be made

of all natural wood fibers, compressed peat moss and free from glues or binders allowing the

plant roots to grow right through the pot during a normal production cycle. The walls of the

pot do not impede plant growth. This creates a vigorous, non-girdled root system that spreads

out evenly and uniformly. The highly porous technology of the DOTPOT allows excluding

drain holes from the pots. Without glue or binders, air and water flow freely through the

entire container without the need of drain holes. The „Organic Materials Review Institute‟

(OMRI) has certified organic production, handling, and processing of the company.

Biodegradable pots known as „coir -pots‟ are also provided by company „Fertile Fibre

Limited, Hereford, UK‟ (Fertilefibre, 2010). Fertile pots are claimed to be biodegradable

fiber pots composed of long coir fibers are manufactured without the use of glues or binders.

These are not peat pots because water, air, and roots will penetrate the walls of the fertile pots

also there is no need for drainage holes. The natural root structure that develops helps to

ensure a successful transplant.

„GREENPOLY‟ is a Chinese company that produces Natural Vegetable Fiber Pot and

exports them. This company claims that these are made of natural vegetable fibers, and 100%

biodegradable resin include PCL (polycaprolactam), PVA (polyvinyl alcohol), PBS

[polybutylene succinate], PHBV [polyhydroxybutyrate-hydroxyvalerate], PHAs

(polyhydroxyalkanoate), PLA (polylactic acid). PCL and PVA always act as carrier resin for

100% biodegradable resin, both PCL and PVA originate from petroleum, but recognized as

biomaterials (Greenpoly, 2005).

„GREENEEM‟, an Indian company (Greeneem, 2010) manufactures biodegradable

cultivation pot made of coconut fibers named as Coco Coir Pot that is used for horticulture,

in ornamental plant, vine and tree nurseries, as well as for the domestic gardening market. It

has exceptionally high permeability to water, air and roots. Coco Coir Pots are claimed to be

very much suitable for faster cultivation, an excellent root system and re-establishment

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 31

without any shock from transplanting. When plants are grown in a Cocoa Coir Pot, the roots

quickly penetrate the pot walls. Contact with the air stops the roots from growing, root buds

start to appear and secondary roots start to develop throughout the pot. This phenomenon is

known as "aerial root pruning".

A U.K. Company named ECO-PACK produce, agro-fiber packaging material made of

more than 90% natural agricultural cellulose fibers (Eco-Pack, 2008). This company claims

that its products are pulp free, emissions free and chemical free. ENVIROARC, an Australian

company (Enviroarc, 2010), claims to be first company in the world that prefers bamboo pulp

for the use in the manufacturing of biodegradable ware. Raw material is 100% organic with

no contaminants, and an uninterrupted supply of raw material allows high volume production

as Bamboo grows naturally easily and quickly (without the need of fertilizers). EnviroArc

products are 100% natural hygienic suitable for use with foods oven proof can withstand heat

of upto1800C microwavable, acid, alkali and oil resistant. Period of degradation is adjustable.

Biodegradable products manufactured by a company named as ECOFORMS (Ecoforms,

2009) are made of Grain husks (primarily rice hulls) and natural binding agents (a

combination of starch based, water soluble binders and biodegradable additives). Under

normal conditions, a pot will last five years. These products are meant to be used and reused

above ground only. They will degrade in the landfill. Although they are not certified organic,

they are ideal for organic production. They contain non-polluting, earth-friendly ingredients.

2.13 NURSERY BAGS & CONTAINERS RELATED RESEARCH (TYPE/ SHAPE/

SIZE / DESIGN)

Plant production in containers is relatively new (Hani, 2009). The production of

container seedlings has increased considerably in the last decades (Dominguez et al., 2006).

In 1984, nearly all of the 10 million long leaf pine (Pinus palustris Mill.) seedlings, planted

in the southern United States, were produced in bare-root nurseries. Two decades later, about

48 million container-grown longleaf pine seedlings were produced that amounts to more than

70% of the total production (South et al.,2005). This rapid shift in stock type occurred

because survival of this species is often less than desired when bare-root stock is planted

(Boyette, 1996). Use of container stock increased average survival by perhaps 22% points

(South et al., 2005). Different container types have been developed that purport to improve

seedling growth and development in the nursery (Dominguez et al., 2006). Containers are

unique and unnatural environments for plants. The perched water table and restricted root

system, containers require changes and adjustments relative to plants grown in landscape

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 32

with natural soils i.e. bare root stock (Hani, 2009). Root restriction is an inherent problem

with container grown trees (Arnold, 1996).

In developing countries polybags are usually filled with native soil and placed on the

ground during production of the nursery crop (Mexal, 1996). Polybags are the most common

used plant growing vessel because of their low cost, apparent simplicity and convenience ,

however all these simplicity and low cost can be deceiving (Jones, 1993). Polyethylene bag

grown seedlings have a deformed taproot, because seedling roots tend to grow in spirals once

they hit the smooth inner surface, this inevitably lead to plants with restricted growth, poor

resistance to stress and wind-throw and even early dieback due to ensnarled root masses or

pathogens (Edwin et al., 2005; Jaenicke, 1999; Jones, 1993). Root spiraling (egression,

kinking, curling) is usually concentrated in the bottom of pots and has been observed in poly

bag seedling production (Aldrete et al., 2002; Sundstrom and Keane, 1999; Dumroese and

Wenny, 1997). Root development problems such as curling, matting and twisting are the

inherent problems of poly bags (Jones, 1993). These started to appear early at the time of

propagation and pose adverse effects into mature trees (Kevin, 2009; Edwin, et al., 2005;

Mexal, 1996; Josiah and Jones, 1992; Sharma, 1987). These deformations can affect seedling

performance several years after outplanting (Halter and Chanway, 1993; Lindstrom, 1990).

Kevin (2009) estimates that in waxflower planting the extent of loss due to planting of root

bound plants, range from 20 to 100% in different cases. Diseases such as collar rot

(Rhizoctonia spp. and Cylindrocladium spp.) were reported in the plants with knotted root

system after a few years in the field (Reid, 2004). Pruning off curled roots from the bottom of

spiralled roots systems has been used to negate the effects of spiralling (Owston and Seidel,

1978) but does not appear to be successful for many wildflowers-Seaton pers comm. (Kevin,

2009).

Another problem may arise when seedling roots reach the bottom of the bag, they may

enter the soil (Edwin et al., 2005). It also resulted in severing of roots during transplanting

and made subsequent harvest more difficult for the laborer. The resulting cutting or tearing of

roots to free nursery stock from soil adversely affects seedlings survival and growth (Hani,

2009; Dumroese and Wenny, 1997; Jones, 1993).

A relationship exists between root curling and the length of the root system, that is

controlled by time in tubes. It appears that one of the problems of the round tube system is

that if plants are left too long in tubes after root strike, spiraling occurs (Kevin, 2009).

Overgrown seedlings at planting out often lead to low-quality seedlings with root

deformation or J-rooting (Edwin et al.,

2005; Mangaoang and Harrison, 2003). Survival of

plants in the field was dependent on the age of tube stock (Salonius et al., 2000, 2002;

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 33

Burdett, 1978; Smith, 1962). In a research carried by Kevin (2009) plants that were held in

tubes from 7 to 16 weeks showed 20 to 30% losses in survival when out-planted. Plants that

had been held in tubes for 12 months before planting decreased to 50% of planting numbers

within 4 months of planting and all plants had died 12 months after planting. Kevin (2009)

advocates to minimize the nursery time for plants before planting out in the field.

It was understood from the studies that the plants grown in improved containers have

greater advantages than those grown in plastic and traditional containers (Hani, 2009). Root

trainers are better alternative to polybags as potting containers. Many alternative container

types have been designed to reduce the incidence of deformed roots (Gilman et al., 2003).

Root trainers are usually rigid containers with internal vertical ribs that direct roots straight

down to prevent spiraling (Jones, 1993). In a root trainer stock system, the containers are set

on frames above the ground (trays fixed on stands) to allow natural air-pruning of roots as

they emerge from the containers. The hole in the bottom of the cell facilitates natural air

pruning and drainage of excess water (Edwin et al., 2005). For a better criteria of plant

growing container Mullan and White (2002) concluded that the important factor in deciding a

cell shape is to prevent the development of a few dominant roots, and so produce a fibrous

root system that promotes the formation of a large number of active root tips on all sides;

holds the root ball together enabling easy handling without damage; once out-planted will

establish root apical dominance and lose the appearance of a planted root plug and develop a

natural root form; allows easy extraction to minimize damage in the field during planting.

Root trainer systems produce further benefits in simplifying nursery operations such as

disease and insect control, transportation and handling, and monitoring and sampling. Also,

the reusability of root trainer containers offsets their initial higher costs when compared to

poly-bags (Jones, 1993).

Edwin et al.

(2005) carried experiments on (Eucalyptus deglupta) and Mangium

(Acacia mangium) and found that Root deformation of seedlings was absent in hiko trays (a

tray set of root trainer) but high in the polybag seedlings. The nursery trial results indicate

that seedlings grown in hiko trays, although having significantly smaller diameter, height and

number of leaves but farmers and ACIAR researchers approved that these seedlings are of

high quality exhibiting straight shoot, trained roots and homogenous growth (Edwin et al.,

2005).Studies have shown that root trainer-grown seedlings have more vigorous and rapid

root growth than seedlings grown in poly-bags and most importantly, out planting survival

with the long-term survival is greatly ensured (Jones,1993). Although all type of containers

produced seedlings with some root spiralling, including those containers with ribs

(Dominguez et al., 2006) and the degree of deformation varies within and between species

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 34

(Kinghorn, 1978) but Improved container design can affect flexibility and 'shelf life' of plants

in the nursery (Hani, 2009).

Increased container size has been reported to cause increased canopy growth. The

large container volumes led to increased dry matter production that increased plant growth

rate in respect of shoot height, diameter, number of branches-leaves and biomass (Vizzotto et

al., 1993; Alvarez and Caula, 1993; Peterson and Krizeki, 1992; Peterson et al., 1991;

Gilliam et al, 1984; Biran and Eliassaf, 1980; Ruff et al., 1978; Richards and Rowe, 1977)

Seedlings in small containers results in root restriction that reduce canopy growth (expressed

as shoot length ,diameter , fresh weight and dry accumulation and leaf area) (Hanson et al.,

1987; Richards and Rowe, 1977; Vizzotto et al., 1993; Alvarez and Caula, 1993). Root

restriction reduces dry matter production but this has not been attributed to nutrient

deficiency (Peterson et al., 1991; Peterson and Krizeki, 1992; Ruff et al., 1978). The

relatively small size of seedlings in root trainers is attributed to the size of the container and

do not affect survival rate after outplanting. Large seedlings can become stunted when

planted in the field (Kevin, 2009; Edwin et al., 2005). Typically, larger seedlings cost more

initially (Davis et al., 2007), but can outperform smaller seedlings in the field (Dominguez et

al., 2006). The proportional balance of the shoot and root systems is important (Edwin et al.,

2005). O‟Reilly et al., (2002), recommended 3:1 shoot to root ratio (dry weight basis) for

most species seedlings ready to be planted which is a useful indirect measure of the balance

between the transpiration area and water-absorbing area.

Donahue et al., (1983) has also stated that growing media should have high water

movement, good drainage and aeration. The excess water not used by a seedling produces a

waterlogged condition that impairs aeration; this in turn reduces photosynthesis, translocation

and growth (Sutherland and Day, 1988). Alternatively, plants grown in more open surfaces

(walls and bottom) could have suffered from higher levels of moisture loss and hence the

reduction in root growth could be a form of stress response (Hani, 2009).

Each species responded differently to the type of container used (McConnughay and

Bazzar, 1991; Krizek et al., 1971). The type of nursery container used during production can

have a dramatic impact on root morphology of container-grown plants (Gilman, 2001;

Arnold, 1996). Shape of the container also influences the biomass production and root

architecture (Hani, 2009). In a study by Keever et al. (1985) the top dry weight of Euonymus

increased linearly in response to both increased pot diameter and pot depth, with greater

response from increased diameter. Keever et al. (1985) also observed that plant root growth

increased in deep pots. According to Schuch and Pittenger (1996), trees grown in tall

containers had 58% more root dry weight and 39% more shoot dry weight than when grown

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 35

in regular containers of the same volume. Larger container size is well correlated with larger

seedling size at the end of the nursery production cycle (Pinto, 2005). Generally, larger

container volumes have greater water and nutrients availability, along with more space for

root development that result in seedlings with larger height and diameter, greater nutrient

content thus better seed ling growth (Hsu et al., 1996; McConnughay and Bazzar, 1991).

With all the variables the ratio of container depth to container diameter is also an

important indicator of seedling development in the nursery, and the optimum ratio was 4

(Dominguez et al., 2006). The equal container volumes better growth would result with

containers with larger diameters (Hocking and Mitchell, 1974). Container depth has a greater

influence on species with dominant taproots and better for longer taproot system such as

Quercus (Dominguez et al., 2006). However, species with heavy lateral root development do

not grow well in narrow and long containers. Many others viz., Carlson and Endean (1976),

Hanson, et al. (1987), Dominguez et al. (2006) also found significant relationship between

the depth/diameter index of the container and the size of the plant. Growing density is also

correlated with seedling morphology and nutrient concentration in the nursery (Dominguez et

al., 2006). High density leads to plants with small stem diameter and less height growth

following outplanting (Landis et al., 1990).

Very few studies have assessed the relationship between seedling growth and container

shape without confounding influences from changes in container volume it is not easy to find

published comparisons for the results (Sutherland and Day, 1988). In a greenhouse

experiment conducted by (Hani, 2009) to investigate the influence of conventional plastic

containers and root trainers (spring ring containers) on root and shoot growth of two tree

species (Acacia saligna and Eucalyptus viminalis) it was revealed that in case of Acacia

saligna the leaf number, leaf area and total biomass production was not influenced by

container types. Root length was greater in root trainer and spring rings. However, root fresh

and dry were greater in conventional pots. In Eucalyptus viminalis plant height was higher in

conventional nursery pots, while the root fresh and dry weight was the same in both

conventional and spring ring pots. Leaf number, leaf area, total top fresh and dry biomass

were not significantly influenced by container types. The difference in shoot fresh and dry

weight was found to be negligible in both conventional pots and spring rings. This clearly

reveals that the top growth of Eucalyptus was same in all treatments as there was no marked

significant variation among treatments regarding the total top biomass showed that shoot

growth was not affected by the differences in containers shapes (Hani, 2009). Schuch and

Pittenger (1996) grew Eucalyptus citriodora in two different shapes of container and also

found no differences in shoot dry weight. Same results were found by Evans and Hensley,

(2004) where container type did not significantly affect dry shoot weights of Vinca and

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 36

Geranium when grown under simulated field conditions. Mark (2003) demonstrated that there

were no statistical differences in the growth parameters among four types of five types of

container shapes and designs.

2.14 AIR INDUCED ROOT PRUNING

Air root pruning is the technique wherein root tip exposure to air movement desiccates

and kills the root tip in a suitable container. As roots get pruned, the area behind the root tip

is stimulated to produce branches providing many more secondary roots (Whitcomb, 2005).

This root pruning presumably results in a more branched (fibrous) root system, which may

facilitate field transplanting and container production (Harrise et al. 2001).There are many

types of these air root pruning containers and bags and they vary greatly in their ability to air-

prune (Gilman et al. 2010). There are many patents are registered on root pruning

containers/bags e.g. Henry (1993), Henry and Henry (2007), Lawton, (1989) and Whitcomb,

(1985). In several research Air root pruning has been demonstrated for tree species using

open bottomed containers (Lovelace, 1998; Hoppé et al., 2005; Hoppé and Harun, 2005).

March and Appleton (2004) found no differences in shoot and root dry weights for Quercus

rubra (red oak) when different air root pruning container types were used. It was shown by

Gilman et al. (2002) that the caliper of Live Oak (Quercus viginiana Mill) was not affected

by root pruning, but slight impact on the height was seen. Gamble and Harun (2005) found

that those plants raised in containers which provided air pruning demonstrated accelerated

growth. Marshall and Gilman (1998) reported that AcceleratorR air root pruning containers

caused an increase in number of descending roots compared to smooth sided containers

probably due to the corrugated sides. Gilman et al. (2002) also reported that height of the

seedlings were reduced slightly but not found significant statistically and root weight: shoot

ratio was reduced when root pruning was carried out but root pruned seedlings had better

survival rate.

2.15 ROLE OF COPPER IN ROOT PRUNING

In the case of chemical induced root pruning, Copper compounds have been

extensively researched. Stinson and Keys (1953), Pellet et al. (1980), Ruehle (1985), Arnold

and Struve (1989) experimented copper compound as root pruning agent. Containers treated

with copper-based paints are now commonly used by growers to reduce root circling and to

increase root system febricity (Struve et al., 1994). Struve (1993), Arnold (1996) and Thomas

et al. (1996) applied 100 gm Cu(OH)2/liter in latex carrier at interior surfaces of containers

whereas Armitage and Gross (1996) applied copper hydroxide formulation (0%, 3.5%, 7%

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 37

and 11%) to plug trays. Neither foliar nor any other copper toxicity symptoms are reported in

these studies whereas roots get pruned on the contact with copper-treated containers/bags

wall. Copper-induced changes in root system morphology are associated with improved

mechanical stability (Burdett, 1978) and increased survival (Struve, 1993) of seedlings after

out-planting. Dumroese and Wenny (1997) carried out an experiment in which copper-treated

seedlings of Pinus ponderosa Dougl. produced a much finer, fibrous root system that was

well-distributed throughout the polybag but untreated seedlings were developed abundance

spiraling roots concentrated in the bottom of the polybag. Seedlings grown in copper-treated

polybags had heights, root collar diameters, and biomass values that were similar to those of

seedlings grown without copper whereas in the non-treated polybagss roots were spiraled

matted, often very thick, usually devoid of secondary roots, sometimes kinked, and probably

accounted for the 33% greater root volume, 32% greater root mass, and significantly lower

shoot-root ratio than that of copper-treated seedlings. An absence of copper promoted

surfaces resulted in accumulation of roots at container bottoms have also been reported by

others (Arnold and Struve 1989; Schuch and Pittenger, 1996). Same results were found in

Copper compounds treatments in nurseries experiments viz., in temperate conifers (Wenny

and Woollen, 1989; McDonald et al., 1984, 1981; Burdett, 1978; Saul, 1968), in temperate

hardwoods (Arnold 1996; Arnold and Struve, 1993; Arnold and Young, 1991), and in

subtropical hardwoods (Schuch and Pittenger 1996; Sparks, 1996; Svenson et al., 1995).

When Burdett and Martin (1982) chemically pruned conifer seedling root systems with

copper carbonate, they found that the treated plants were shorter than the controls. The

reduction in root mass of treated seedlings in our study may have been attributable to an

absence of roots at the interface between polybag and medium, as was concluded by Furuta et

al. (1972) for Eucalyptus viminalis Labill., and/or by the reduction of thick spiraled roots at

the bottom of polybags. Furthere it increases the shoot-root ratios significantly when

seedlings grew in contact with copper which again a good indication (Dumroese and Wenny,

1997). On the other hand several studies have shown that height and biomass were unaffected

by copper-coated containers (Wang, 1990; Wenny, 1988; Wenny and Woollen, 1989). South

et al. (2005) reported an increase in the biomass of the copper treated seedlings. Regan and

Davis, 2008 reported better seedling growth after outplanting of copper treated container

grown seedlings of western white pine (Pinus monticola).

Roots of seedlings exposed to the copper coating did not penetrate bottom drainage

holes (Dumroese and Wenny, 1997; Schuch and Pittenger 1996; Svenson et al., 1995; Arnold

and Struve, 1993). On the behalf of the several studied discussed here it can be concluded

that copper is toxic to roots, and roots will self-prune on contact with the copper-treated cell

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 38

wall. After outplanting, these root tips will grow more lateral roots, particularly in the upper

profile of the root plug (Campbell et al., 2006; Dumroese, 2000; Wenny and Woollen, 1989;

Burdett et al., 1983).

Crawford (1997) discussed a practical and commercial example of copper application

(The Spin-Out Coating) to improve nursery seedlings roots development in the container

media. When root tips reach the sides of the container, inhibits root elongation and deflection

and stimulates root branching. As the plant produces new roots, they are pruned, resulting in

a very fibrous root system. Thus Spin Out prevents the “cage root” condition where roots are

only present on the outside of the root ball. SpinOut-treated geotextile fabric prevents weeds

from becoming established by controlling roots that attach and grow through the fabric. This

concept has been also modified where SpinOut-treated fabric is cut into circles or discs and

placed on the tops of pots to control weeds as an alternative to herbicides. Treated fabric also

controls zoospores of Phytophthora crytogea and reduce the spread of disease from infected

to non-infected plants on a sand-bed. Capillary mats used for irrigation of greenhouse crops

remain free of algae growth when treated with Spin Out. Application of spinout coating was

found also helpful to reduce chlorosis in the plants.

In the case of direct availability or contamination of copper in the soil a less quantity

affects the plant health. Strandberg et al. (2006) reported that highest biomass was reached at

intermediate copper concentrations i.e. 200 mg/kg. In his experiment Kjaer and Elmegaard,

1996, studied copper effect on the seedlings of black bindweed (Polygonum convolvulus L.)

with the different dosages of copper sulfate and also found that dosages above 200 mg kg-1

reduced biomass and seed production. Aging of the copper-contaminated soil had only small

effects on bioaccumulation of copper, copper toxicity, and extractable soil copper fractions.

Soil copper had no effect on emergence of cotyledons (Bruus et al., 2000). Cu is a plant

micronutrient (Mutsumi et al., 2010; Michael et al., 2003) essential in several enzyme

systems with minimum requirements generally of 1–5 mg/kg in plant tissue, while at

concentrations higher than 20–30 mg/kg, depending on plant species, it may cause toxicity

(Marschner,1995).Toxicity symptoms include chlorosis, reduced growth, and root

abnormalities. Various mechanisms for dealing with elevated copper levels are found in

plants (Murphy et al., 1999; DeKnecht et al., 1995; Turner 1994; Ernst et al., 1992). Penta

hydrated Copper (II) Sulphate has many roles in different fields but in particular in plant

tissue culture copper salt is used to supply copper ion a micro nutrient (Ganapathi et al.,

2008). In a study copper was added as a CuSO4 solution and the sulfate concentration proved

less toxic than nitrate and chloride (Bruus et al., 2000).

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 39

2.16 COPPER AS BIOCIDE

According to the information rendered by Borkow and Gabbay (2005) the first

recorded use of copper in agriculture was in 1761, when it was discovered that seed grains

soaked in a weak solution of copper sulphate inhibited seed-borne fungi. The greatest

breakthrough for copper salts as fungicides undoubtedly came in the 1880's with the

development of a lime-copper formulation by the French scientist Millardet "Bordeaux

mixture." Within few years Burgundy mixture, also was prepared from copper sulphate and

sodium carbonate (soda crystals) and is analogous to Bordeaux mixture. Use of Bordeaux and

Burgundy mixtures against various fungus diseases were proved very successful in the

agriculture horticulture and forestry throughout the world. The use of copper sulfate for algae

control is still very common, primarily because of its low cost and eases of application.

Copper sulphate has been used to inhibit timber and fabric decay, since it renders them

unpalatable to insects and protects them from fungus attack. Copper sulphate has been in use

since 1838 for preserving timber and is today the base for many proprietary wood

preservatives. Today copper is used as a water purifier, algaecide, fungicide, nematocide,

molluscicide, and as an anti-bacterial and anti-fouling agent.

Copper also displays potent anti-viral activity (Yamamoto et al., 2001; Sagripanti and

Lightfoote, 1996; Sagripanti et al., 1993; Mitun et al., 1983). Copper Metal ions, either alone

or in complexes, have been used for centuries to disinfect fluids, solids and tissues (Block,

2001; Dollwet and Sorenson, 2001). Copper was found to be one of the most toxic metals to

heterotrophic bacteria in aquatic environments. Albright and Wilson (1974) found that

sensitivity to heavy metals of microflora in water was (in order of decreasing sensitivity): Ag,

Cu, Ni, Ba, Cr, Hg, Zn, Na and Cd. More than 23 copper compounds including copper

sulfate, are identified so far for their different applications as bactericide, algicide, fungicide,

molluscicide and acaricide (Borkow and Gabbay, 2005). Penta hydrated Copper (II) Sulphate

solution has anti fungal and anti-bacterial activity. It was also found suitable for surface

sterilization in tissue culture experiments (Ganapathi et al., 2008).

The mechanism of copper antifungal and anti-algae activity has not been well studied.

It has been suggested that the copper ions form electrostatic bonds with negatively charged

areas on the microorganism‟s cell walls. These electrostatic bonds create stresses that lead to

distorted cell wall permeability, reducing the normal intake of life sustaining nutrients

(Borkow and Gabbay, 2005). In contrast to the low sensitivity of human tissue to copper

(Hostynek and Maibach, 2003; DPT, 2002) microorganisms are extremely susceptible to

copper. Copper toxicity to microorganisms may occur through the displacement of essential

Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 40

metals from their native binding sites, from interference with oxidative phosphorylation and

osmotic balance, and from alterations in the conformational structure of nucleic acids,

membranes and proteins (Borkow and Gabbay, 2005).

The supposed mechanism of cyto-toxicity effect of copper sulphate has been proposed

by Carubelli et al. (1995). They found that the cyto-toxic effect may be mediated by a free

radical attack on proteinaceous components of the phage through a site specific generation of

hydroxyl radicals on protein-bound transition metal ions. According to Bartlett et al. (2001)

copper may attack sulfur containing amino acid residues in the proteins used for

photosynthesis inside an algae cell. As a result, photosynthesis is blocked and lead to cell-

lysis and death.

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