“Environment friendly Biogas Plants”

Course Title: Agriculture and Environment

Course No: ES 2209

Date of Submission: October, 2005.

Submitted to:Dr. Subrota Kumar SahaAssistant ProfessorES DisciplineKhulna UniversityKhulna

Submitted By:Md. Mahmud Hasan TuhinRoll: 0310212nd year 2nd termES DisciplineKhulna UniversityKhulna

ACKNOWLEDGEMENT

All praise is to the Supreme Being; creator and ruler of the universe, God whose mercy keep us alive and to pursue my education in Environmental Science Discipline and to complete the assignment for the fulfillment of the course Agriculture & Environment.

I am really pleased and proud to express my deepest sense of gratitude, indebt ness, since appreciation and profound respect to our reverend teacher, Dr. Subrota Kumar Saha, Environmental Science Discipline, Khulna University, Khulna for his scholastic guidance, constructive criticism, and unwearing efforts to execute this assignment.

I would like to express my hearty reverence, profound adoration and devout respect to our honorable teacher Dr. Subrota kumar Saha, Assistant Professor, Environmental Science Discipline, Khulna University, Khulna for his valuable suggestions.

However, I am responsible for any remaining errors or inadequacies.

Md. Mahmud Hasan TuhinRoll No. 031021

CONTENTS

TOPICSIntroductionBiogasHow Biogas producedMechanism of Biogas formationWho introduce biogas plant in BangladeshCross section of a biogas chamberPotentials of Biogas in BangladeshTypes of Biogas Digester invented by LGEDGas Generation RateUses of Biogas ResiduesAdvantages of Biogas TechnologyOther uses of biogasAffordabilityImpact on health and environmentSome ExamplesConclusionReference

Introduction:

Bangladesh is densely populated country. Large proportions of rural and urban poor traditionally harvest; fire wood, Vegetation, animal excreta and agricultural residues for domestic cooking.  These methods proved to be unsustainable as fire woods contributed to higher levels of deforestation.  Vegetation covers only 9-10 % of total land, which is lowest as world average. Population explosion and to meet related energy demands deforestation level is higher than forestation efforts which is resulting environmental degradation. Uses of fire wood increases at rate of 2 % annually. The high cost of petroleum products, low coverage of the electricity grid, gasification and increasing scarcity of traditional fuel woods due to deforestation created an energy deficit situation in rural Bangladesh. Environmental experts predicted massive deforestation if crisis is not being met from alternative source. 

However long term sustainable development in energy sector requires a gradual shifting towards renewable sources of energy. Country like Bangladesh, making people renewable way meeting energy demands, considerably Biogas technology is cheaper option.

Biogas:

Organic matters such as animal and human excreta, agricultural and industrial waste, water hyacinth etc. when fermented under an anaerobic condition produce a combustible gas called Biogas. 

It is a renewable source of energy, can be used as fuel for cooking, lighting, running vehicles and generators, etc.  Other natural resources like oil, gas etc. are limited and will be exhausted in course of time.   That is why, the developed countries consider their natural resources very precious and are cautious about extracting those.  In Bangladesh neither the decision-makers nor the experts pay due importance on proper extraction and use of natural resources.  With the present rate of consumption, natural energy resources like gas will be exhausted shortly and this is high time to derive policy and practice for exploration and use of alternative renewable sources if we want to meet energy crisis in near future.  Biogas has been found to be a proven renewable energy option.

How Biogas produced:

We know that when any organic materials like cow dung and other organic matters fermented under an anaerobic condition produce a combustible gas. But without anaerobic condition bio gas cannot be formed. For this a chamber is needed. The chamber is made especially, which shape is dome like have a inlet and a outlet chamber.

Fig: Bio Gas plant

Fig: Fixed dome Biogas Plant

Gas Outlet

Dome

Inlet Pipe

Outlet Chamber

Digester

Gas collecting pipe

Mechanism of Biogas formation:

Who introduce biogas plants in Bangladesh?

Biogas technology has been gaining popularity and importance, especially in the developing countries because of its appropriateness in the context of technical, socio-economical and resource endowments of these countries. With zeal and commitment to serve the nation, LGED has been involved in dissemination of biogas technology since 1985 and has been able to demonstrate its usefulness at more than thousand sites in different parts of the country. The full meaning of LGED is “Local Government Engineering Department”. This is a government motivated village development organization working for development of village people.

Fig: LGED constructed biogas plants of Bangladesh

With out LGED some other organization like “Bangladesh Council of Scientific and Industrial Research”, “Bangladesh Rural Advancement Committee”, “Grameen Shakti” etc government and non government organization are working for development for biogas plant in Bangladesh. In next page a table shows the numbers of biogas plants.

Cross section of a biogas chamber:

Potentials of Biogas in Bangladesh:

Cattle dung available from 22 million cows and buffaloes is nearly 220 million kg. One kg. Of dung can produce 0.037 cum of Biogas. i. e. available cattle dung can produce 2.97XIO9  cum of gas which is equivalent to 1.52X106 tons of kerosene or 3.04X106 tons of coal. Besides, a substantial amount of Bio-gas can be produced from human and animal excreta, garbage and water hyacinth.  If all the household can be brought under Biogas technology, it is possible to get 1.03X 10 9 cum of gas from the filth of human being only. A conversion of 5% of different raw materials should produce an estimated 2X108 cum/day of Biogas. At present Bangladesh meet 46.15% of its energy need by agricultural residue, 10.5 % by fuel wood and 33% by tree residue. Biogas will reduce energy deficit 15 %.  

Types of Biogas Digester invented by LGED:

There are three types of basic designs of biogas plants tried in Bangladesh:

(i)    Floating cover digester, (ii) fixed cover digester, and (iii) plastic cover digester. 

(i) Floating cover digester:

It works on the principle of constant pressure, changing volume. The digester, cylindrical well, commonly made from brick and cement, is covered with a floating steel cylinder with an open bottom (Fig. A). As the cylinder has a constant weight, it moves up when gas production is higher than consumption and comes down under the reverse conditions.  

(ii) Fixed cover digester :

It works according to the principle, constant volume, changing pressure. When the rate of gas production is higher than that of gas consumption pressure inside the digester rises and expels some digester contents into the outlet compartment. When the consumption is higher than production, pressure inside the digester falls and the expelled materials in the outlet compartment run back to the digester

(iii) Plastic Cover digester:  

    A long cylindrical polythene/PVC bag, half-buried longitudinally in the ground, is fed with fresh cow-dung slurry at one end and discharged at the other. With the formation of gas, the bag swells like a balloon and the gas is led out to the point of use through a pipe by putting pressure on the balloon form outside

In early 80’s, the floating type design was used for biogas plant. But due to corrosion of the steel dome, the gas leakage problem happened and it could not be removed. Later on BCSIR tried with fixed done type design and it has been successful in all biogas plants. The plastic bag type design is not used in Bangladesh it is used in China. In this project, the fixed dome type design has been proposed.

Gas Generation Rate:

Daily input in the digester is 221xO.5 kg. =110.05 kg.   Assuming water content to be 83% the quantity of suspended solid will be 18,71 kg.   For optimum gas generation, the percentage of suspended solid should be 8%.  To attain this percentage, water and night soil mixing proportion should be 1:1.  But in practice the users generally use more then 3 liters of water for the cleansing purpose, as a result the percentage of solid reduced to 2.5. This causes drastic reduction in gas production.  This problem is no more acute where there is no water supply reduction in gas production.   This problem is no more acute where there is no water supply system.   To improve this situation, we have decided to add kitchen waste with night soil.

Uses of Biogas Residues:

The residues come out through outlet chamber have various uses. As for example:

Improved organic fertilizer For Mass room cultivation Aquaculture Purl Cultivation Poultry, fish foods Seeds fermentation

Advantages of Biogas Technology:  (a) Produces pollution free bio fuel (b) Improved organic fertilizer

Bio product of biogas plant is improved organic fertilizer. This fertilizer contains organic component like Nitrogen, Phosphorus, and Potassium & Micro Nutrients

Nitrogen Prosperous PotassiumProducing compost fertilizer Nitrogen losses calculated  50 % in every three months at the time of aerobic fermentation, on the other hand 10 % losses calculated while producing from  biogas

Organic and inorganic phosphorus calculated 1 to 3 times higher from biogas residues  than compost fertilizer

Potassium losses for leaching   rain water in organic compost is higher than anaerobic fermentation of  biogas residues

residues

(c) Nutrition's comparison between Compost fertilizer and biogas residues. (Production in percentage): 

Type of fertilizer Types of Crops 

Paddy Wheat Corns Cotton

Common Organic fertilizer

100 100 100 100

Biogas Residues 110 112.5 128 124.7

d) Nutrition's comparison of   between Chemical fertilizer and biogas residues from Biogas plant. (Production in percentage):

Other uses of biogas:

With the help of biogas we can drive gas generator to produce electricity in rural area.

We can use gas incubator to produce poultry chicken from egg. We can use gas lantern by using bio gas in night time in village area. Hotel and restaurant can use biogas for cooking purposes by using the

residue of vegetable and food waste. We can drive gas hitter for hitting water during winter season. Different poultry and dairy farm can mitigate their need of gas by

using their own animal excreta.

Affordability:

Biogas is a proven technology, There is no risk of failure if proper design and supervision can be ensured.  Most of the commercial banks are now convinced and took decision to provide loan for the construction of Biogas plants.  Most of the urban poor can not afford gas connection as it costs Tk.  200 to Tk. 400 per month.  Instead they can install Biogas

CropsCrop production from Chemical

fertilizer (ton/ha.)

Crop production from Biogas residues

(ton/ha.)

Production acceleration in

%Paddy 8.28 9.02 8.93Corn 7.0 9.5 35.7

Cotton 3.13 3.97 26.8Vegetables Actual production Higher production -

plants with. Bank loan and repay the loan out of their fuel savings 'domestic' size Biogas plant of 100 cft capacity cost Tk. 15,000 to Tk. 18,000 and can meet the cooking energy need for a five- member family.

Biogas Plants installation under Local Government Engineering Department (LGED):

Raw materials Type of DesignDaily gas

productionNo. of plants

Comments

Family Type of Biogas Plants

Cow dung Fixed dome: 1059 nos. 120-150 cft 700

Cow dung Floating dome: 6 nos. 120-150 cft 6200-300 cft 259390-430 cft 55580-780 cft 45

Human excreta Fixed dome 140 cft 5233 cft 25374 cft 27561 cft 3800 cft 1

Human excretaCommunity Biogas Plant (Fixed dome)

140 cft 3Cluster Villages

Water hyacinth Fixed Dome 350 cft 2Experimental

Basis

Organic Waste Fixed Dome 380 cft 15Experimental

Basis

Poultry dropping Fixed Dome 420 cft 20

Family Type of Biogas Plants Total 1042

Community Biogas Plants

Human ExcretaCommunity Biogas

Plants300 cft 102

Human Excreta Fixed Dome 250 cft 20

Secondary Town

Infrastructure Development

Project-II

Human ExcretaCommunity Biogas

Plants400 cft 2

Done by SRE project, LGED

Community Biogas Plants 124

Total Biogas Plants installed under LGED

1166

Impact on health and environment:

Large scale bio energy development in Bangladesh could bring significant environmental benefits. Sustainable bio-energy development could: Reduce higher level of deforestation. Reduce net greenhouse gas emissions. Improve air quality and reduce acid deposition. Improve soil quality and reduce erosion. Reduce land filling by adding value to residues. Reduce agricultural chemical runoff. Improve sanitation condition. Improve habitat for native wildlife and improve biodiversity. Outlining sustainable land use and improved air quality. Improved habitat for wildlife and reduced use of fertilizers and

insecticides compared with lands used for row crops,        protection of riparian areas, and erosion protection for sensitive land areas.

Reduction of Greenhouse Gases from biomass power takes place because the carbon dioxide released during combustion is absorbed by the plants as they grow.

Biomass could play a role in reducing C02 emissions in both of these sectors.  As the slurry remains in the digester for 30-40 days in anaerobic condition, the effluent becomes pathogen free and the output is smell-free combustible gas and organic fertilizer improving the environment and preventing diseases. At present Bangladesh meet 46.15% of its energy need by agricultural residue, 10.5% by cow dung, 12.9% by fuel wood and 33% by tree residue.  This means that to meet our energy need we are depriving, ourselves from organic fertilizer and creating environmental imbalance by deforestation.  One pragmatic estimate puts that the use of Biogas will reduce energy deficit by 15%.

Figures of some biogas plants

Fig: Floating cover digester bio gas plant

Fig: Fixed Dome digester type biogas plant

Fig: In Poultry Farm Fig: Cooking with Biogas

Fig: Biogas Generator

Some figure shows different uses of biogas in home and industrial purpose:

Fig: Gas generator produces electricity in Poultry Farm

Some Examples:

Biogas plants in different institution: LGED has constructed 61 Biogas plants in different educational institutes, orphanages, hospitals, school/college hostels for solving the sanitation problems and getting biogas as an alternative energy source.   One of these important plants is in Faridpur orphanage.  There are 250 students and staff in Faridpur orphanage.  For their night soil disposal they needed to construct a septic tank for 250 users with Tk. 60,000.LGED in mid 1992 constructed a Biogas plant with Tk. 16,000 which served the purpose of septic tank as well as a source of gas and fertilizer.  This has reduced the investment by Tk. 34,000 and the mission has been saving Tk. 25,000 against fuel cost per year.

Ganaktuli Sweeper colony, Dhaka :  There are five buildings for sweepers and 40 families reside in each building.  The latrines of the buildings were not connected with any septic tank or sewerage system.  Previously, night soil was passing through surface drain creating health hazard.  To connect the latrines of building No-I to the nearby sewer line Tk. 60,000 and to construct a septic tank for 221 users of the building Tk. 50,000 were necessary.   Instead, LGED constructed a Biogas plant for Tk. 20,000 in 1993 which is working till today without any problem giving sufficient gas to meet fuel need of all families of 1 building.   There was some maintenance for leakage and Tk. 300 was spent. Observing the performance of the plant, residents of other 4 buildings created pressure on the city corporation to construct similar plant in those buildings. By now Biogas plants have been constructed in all the remaining 4 buildings.

'Ecological Village' Amgram/Uttar Hogla in Madaripur  : LGED took up 'Ecovillage' project on experimental basis as pilot programme with the objectives to make the villagers aware about environment and technology, create clear, healthy and acceptable environment in the villages and inspire the people around the villages to accept such project. There are 662 people in the village in 123 families.  Besides other socio economic activities, the following facilities were also provided: There was no latrine in the village and 95 latrines were constructed. .As an alternative source of energy 15 Biogas plants were installed, three persons were trained in the construction of Biogas plant. The Biogas plants are providing energy input to the villagers.

Conclusion:

Biogas technology, as it uses animal and agricultural wastes and returns the waste as fertilizer, energy being the bonus, is considered as a most appropriate technology to a developing country like Bangladesh which is mainly an agricultural country. With about 90% of the population residing in the rural areas, the land distribution pattern bears a strong relationship to the ownership of cattle and the financial capability for installing and running a biogas plant. Only the upper 20% of the rural families own more than four head of cattle per family. Although 4-5 cattle are needed for a family-size bio plant according to the current technology, only those well-to-do families of rural areas can be brought into the biogas program. There are however, some social and economic aspects, which have strong bearing on the spread of use of this technology. But if we can mitigate the problems by using low cost technology and produce biogas for our daily using purpose then it will be very much acceptable for us by environmentally, economically and reduce pollution.

Reference:

http://www.lged.org/biogas http://www.bcsir.org/fdevproj http://www.lged-rein.org/ http://www.lged-rein.org/biomass/index_probiomass http://www.lged-rein.org/biomass/sre_combio_haor Hassan. “Higher Secondary Botany”, Hassan Book House, Dhaka. Leaflet of “Grameen Shakti”