INTRODUCTION

What is a carbon footprint?

Carbon footprint (CF)-also named Carbon profile-is the overall amount of carbon

dioxide and other greenhouse gas (GHG) emissions (e.g. methane, laughing gas,

etc) associated with a product, along its supply-chain and sometimes including

from use and end-of-life recovery and disposal. Causes of these emissions are, for

example, electricity production in power plants, heating with fossil fuels,

transport operations and other industrial processes.

The carbon footprint is quantified using indicators such as the Global Warming

Potential (GWP). As defined by the Intergovernmental Panel on CLIMATE Change

(IPCC), a GWP is an indicator that reflects the relative effect of a greenhouse gas

in terms of climate change considering a fixed time period, such as 100 years

(GWP100). The GWPs for different emissions (see Table 1) can then be added

together to give one single indicator that expresses the overall contribution to

climate change of these emissions.

How can I measure the carbon footprint of my product?

The carbon footprint is a sub-set of the data covered by a more complete Life

Cycle Assessment (LCA). LCA is an internationally standardized method (ISO

14040, ISO 14044) for the evaluation of the environmental burdens and resources

consumed along the life cycle of products; from the extraction of raw materials,

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the manufacture of goods, their use by final consumers or for the provision of a

service, recycling, energy recovery and ultimate disposal.

One of the key impact categories considered in an LCA is climate change, typically

using the IPCC characterization factors for carbon dioxide equivalents. Hence, a

carbon footprint is a life cycle assessment with the analysis limited to emissions

that have an effect on climate change. Suitable background data sources for the

footprint are therefore those available in existing LCA databases. These databases

contain the life cycle profiles of the goods and services that you purchase, as well

as of many of the underlying materials, energy sources, transport and other

services.

Table 1: Global warming potentials of some Greenhouse Gases (source: IPCC,

2007)

Species Chemical formular GWP100

Carbon dioxideCO2

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Methane CH4 25

Nitrous oxide N2O 298

HFCs - 124 - 14800

Sulphur hexafluoride SF6

22800

PFCs-

7390 - 12200

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Why the evaluation must be broadened to avoid misleading results and wrong

decision?

Although building upon a life cycle approach, carbon footprints address only

impacts on climate change. When exclusively carbon footprint data are used to

support procurement decisions or to improve goods and services, other

important environmental impacts are neglected while often running opposite to

climate change, resulting in a “shifting of burdens”. Achieving sustainable

consumption and production requires the consideration and evaluation of all

relevant environmental impacts at the same time, such as e.g. acid rain, summer

smog, cancer effects and land use. This can only be ensured by the more

complete Life Cycle Assessment.

If organizations are now developing carbon footprint data, then it makes sense to

evaluate also relevant non-greenhouse gas emissions (e.g. NOx, particles, SO2)

along the product supply chain or full life cycle. The in-house effort is only slightly

higher and same background data sources will be used.

Are there standards or guidelines to perform carbon footprint calculations?

The international standards ISO 14040-14044 provide robust and practice-proven

requirements for performing transparent and accepted carbon footprint

calculations. Over the past ten years, a wide consensus on climate change

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evaluations in this life cycle context has been built up in the scientific community

and has successfully been applied by many leading companies in all sectors. In a

policy context, the carbon footprint can be seen as a subset of the growing

demand for life cycle based information that is being used for knowledge-based

decision making in the context of sustainable consumption and production.

ISO standards also support specific communication needs on climate change

topics. The ISO type I Eco-labels and type III Environmental Product Declarations

are the best reference framework for third party verified claims on carbon

performance of products. We note here the importance of critical third-party

reviews to help ensure problems do not arise later.

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TOP SOURCES OF GREEN HOUSE GAS EMISSIONS

Power: Today hundreds of aged power plants release large volumes of green

house gases (GHGs) while supplying electricity for U.S. These seldom top 38%

thermal efficiency even though technologies exist that can better 50%. A 1%

efficiency improvement out of 26 quadrillion Btu conversion losses from U.S.

power production would result in savings of 260 trillion Btu, an equivalent of GHG

emissions from3.5-million passenger automobiles.

Integrated gasification, combined-cycle (IGCC) leads the list of solutions to this

problem. IGCC combines two thermodynamic cycles: a gas combustion cycle and

a steam cycle, each with its own turbine and generator. Natural gas or coal

gasification provides energy for the first cycle. Heat from the flue of the first cycle

is used to generate superheated steam to drive the second set of turbines. Larger

temperature differences between the hot and cold ends of the combined cycle

allow higher thermal efficiency relative to single cycles, netting benefits of 20%

less GHG and 20-40% lower water usage.

IGCC capacity planned for 2014 is 14.8 GW with 27 projects in 16 states.

Worldwide, nearly 4 GW of IGCC currently operate and 50 new projects totaling

27 GW have been announced.

Ocean and terrestrial (vegetation and soils) CO2 sequestration are being

investigated. The environmental impact of these methods is unknown at this. CO2

storage in soils as magnesium carbonates or as CO2 clathrate are promising as

safe, solid materials offering compact storage with potential commercial value.

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Transportation fuels: Transportation fossil fuels release the second largest

volume of GHGs. Renewable fuels (bio-ethanol and biodiesel) are leading

solutions reducing GHGs from 7 to 90% per gallon, compared to gasoline,

depending on feedstock and process type, according to Argonne National

Laboratory. Applying the low end of this range to the 160-billion gal/yr of gasoline

consumed in the U.S., 133-million tons of CO2 emissions would be prevented. For

companies interested in bio-fuels production, an excellent repository of reports

and models is accessible at the National Renewable Energy Laboratory’s (NREL)

website.

Industry, including chemicals: Energy consumption per unit of chemical output

decreased 40% between 1974 and 1990. Since 1990 however, improvement

slowed to a relatively flat rate. In 2005, Oak Ridge National Laboratory reported

possible energy savings for the twelve largest energy users in chemicals totaling

252 trillion Btu/yr. Paper, ethylene, oxygen, ammonia and styrene lead the list (in

that order) with 219 trillion Btu.

Chemical Industry Vision2020 and the U.S. Department of Energy (DOE) estimate

inefficiencies of 2.7 quadrillion Btu in the chemical industry, and estimate that

innovations could cost-effectively achieve 30% improvement by 2020 or 750

trillion Btu/yr, an equivalent to emissions from 9 million passenger cars – enough

to account for most cars in New York City, Los Angeles, Chicago, and Houston

combined.

Many companies responded early to the challenge: Boise Cascade generates 54%

of its energy needs from renewable resources; Dow Chemical built seven new

cogeneration power facilities

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since 1994 that reduced usage by approximately 23 trillion Btu/yr, eliminating

approximately 1.2 million metric tons of CO2 emissions.

Another development is significant investment in bio-refining. Archer Daniels

Midland recently launched commercialization of biochemical replacements for

petroleum-derived chemicals and stated its intentions to develop new chemicals

with increased functionality and lesser environmental impact.

In general there two major ways that green house gases enter the atmosphere,

namely:

-Natural processes

-Human activities

Natural processes: Green house gases are released into the atmosphere through

natural processes such as animal and plant respiration, ocean-atmosphere

exchange soil respiration and decomposition and volcanic eruptions. The amount

of carbon dioxide produced by natural sources is completely offset by natural

carbon sinks and has been for thousands of years. Before the influence of

humans, carbon dioxide levels were quite steady because of this natural balance.

Human activities: Since the industrial revolution, human sources of CO2 and other

greenhouse gases has been growing. The main human sources of greenhouse gas

emissions are: fossil fuel use such as the combustion of fuels for electricity, steam

and heat generation, combustion of fuels for transportation, intensive livestock

farming, use of synthetic fertilizers and industrial processes.

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THE ROLE OF CHEMICAL ENGINEERS IN REDUCING THE CARBON FOOTPRINT

In manufacturing, the most common way to reduce the carbon footprint is by

reducing, reusing, and recycling of refuse. This can be achieved by recycling the

packing materials, by selling the obsolete inventory of one industry to the

industry who is looking to buy unused items at lesser price to become

competitive. Nothing should be disposed off into the soil; all the ferrous materials

which are prone to degrade or oxidize with time should be sold as early as

possible at reduced price. This can be done by using reusable items such as

thermoses for daily coffee or plastic containers for water and other cold

beverages rather than disposable ones. If that option isn’t available, it is best to

properly recycle the disposable items after use. When one household recycles at

least half of their household waste, they can save 1.2 tons of carbon dioxide

annually.

Another easy option is to drive less. By walking or biking to the destination rather

than driving, not only is a person going to save money on gas, but they will be

burning less fuel and releasing fewer emissions into the atmosphere. However, if

walking is not an option, one can look into carpooling or mass transportation

options in their area.

Chemical engineers play a leading role in the design and implementation of

effective technology-based solutions to control CO2 emissions. Some of the

technologies in place include:

-Cleaner burning fuels and alternative fuel strategies

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-Catalytic converters

-Carbon Capture and Storage

-Advanced combustion systems

CLEANER BURNING FUELS AND ALTERNATIVE FUELS STRATEGIES

Chemical engineers help reduce automotive air pollution through advanced

petroleum refining techniques. One example is hydro treatment, which uses

hydrogen gas and a catalyst to produce gasoline and diesel fuel with significantly

lower levels of sulfur and lead. These techniques have made it possible

to produce reformulated fuels that function as effectively as earlier

leaded fuels, while releasing fewer pollutants.

An alternative fuel, most generally defined, is any fuel other than the

traditional selections, gasoline and diesel, used to produce energy or

power. The emissions impact and energy output provided by

alternative fuels varies, depending on the fuel source. Examples of

alternative fuels include biodiesel, ethanol, electricity, propane,

compressed natural gas, and hydrogen.

Alternative fuels being used in transportation are briefly described below:

Biodiesel is a clean burning, renewable alternative fuel that can be produced

from a wide range of vegetable oils and animal fats. Biodiesel contains no

petroleum, but can be blended at any level with petroleum diesel to create a

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biodiesel blend. It can be used in compression-ignition (diesel) engines with little

or no modifications.

Ethanol is a renewable alternative biofuel made from various plant materials.

Ethanol can be blended with gasoline in varying quantities; most spark-ignited

gasoline-style engines will operate well with mixtures of 10% ethanol (E10). E85, a

mixture of 85% ethanol and 15% unleaded gasoline, is an alternative fuel for use

in flexible fuel vehicles (FFVs).

Electricity used to power vehicles is provided by the electricity grid and stored in

the vehicle’s batteries. Vehicles that run on electricity have no tailpipe emissions.

Electric vehicles are not currently available from the major auto manufacturers;

most electric vehicles have been converted by amateur mechanics.

Propane, also known as liquefied petroleum gas, is a by-product of natural gas

processing and crude oil refining. Propane is less toxic than other fuels. It has a

high octane rating and excellent properties for spark-ignited internal combustion

engines. C urrently, less than 2 percent of U.S. propane consumption is used for

transportation; however, interest is growing due to its domestic availability, high

energy density and clean-burning qualities.

Compressed Natural Gas (CNG) is a natural gas that is extracted from wells and

compressed. Natural gas is a fossil fuel comprised mostly of methane and is

cleaner burning than gasoline or diesel fuel. Natural gas vehicles have been found

to produce less greenhouse gas emissions than gasoline vehicles, but very little

natural gas consumption is currently used for transportation fuel.

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Hydrogen (H2) is a renewable, domestically-produced, alternative fuel that can be

used to create electricity. A chemical reaction between oxygen and hydrogen

produces the electric power, and when the transportation fuel is pure hydrogen,

the only resulting emission is water vapour. Depending on the energy source that

causes the chemical reaction, hydrogen can be an emission-free transportation

fuel. Not widely used today, current government and industry research and

development are investigating safe and economical hydrogen production and

hydrogen vehicles.

CATALYTIC CONVERTERS

Cars, trucks, and buses are essential for transportation and freight delivery

around the world. However, the exhaust from the gasoline and diesel powered

engines required to propel these vehicles has been a major cause of air pollution.

The catalytic converter is considered one of the most important contributions to

the field of air-pollution control. It is now a standard feature on vehicles

everywhere. It destroys the three main pollutants found in engine exhaust (i.e.

CO, NOx and unburned hydrocarbons-most often in particulate matter). The

converter consists of a porous honeycomb ceramic base material coated with a

precious metal catalyst. The honeycomb structure provides high catalyst surface

area, which maximizes the contact between the catalysts and the pollutants in the

hot exhaust gases.

When this novel structure was first invented, it featured two distinct chemical

engineering advantages:

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1. It maximized the amount of catalyst-coated surface area to which the

engine exhaust may be exposed.

2. It minimized the amount of expensive precious metal catalyst required.

CARBON CAPTURE AND STORAGE (CCS)

CCS offers the potential for moving towards near-zero emissions to the

atmosphere from coal-fired and gas-fired power stations. The scale of the

potential has been outlined by the IPCC, which has stated: “in most scenarios for

stabilization of atmospheric greenhouse gas concentrations between 450 and

750ppmv CO2 and in a least-cost portfolio of mitigation options, the economic

potential of CCS would amount to 220-2200 Gigatonnes (Gt) CO2 cumulatively,

which would mean that CCS contributes 15-55% to the cumulative mitigation

effort worldwide until 2100” [IPCC 2005].

While CO2 capture technologies are new to the power industry they have been

deployed for the past sixty years by the oil, gas and chemical industries. They are

an integral component of natural gas processing and of many coal gasification

processes used for the production of syngas, chemicals and liquid fuels. There are

three main CO2 capture processes under development for power generation

namely:

Pre-combustion capture systems take the syngas produced from coal gasification

and convert it via a steam-based chemical reaction into separate streams of CO2

and hydrogen. This facilitates the collection and compression of the CO2 into a

supercritical (fluid-like) form suitable for transportation and geological storage.

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Oxyfuel combustion involves combustion of coal in pure oxygen, rather than air,

to fuel a conventional steam generator. By avoiding the introduction of nitrogen

into the combustion cycle, the amount of CO2 in the power station exhaust

stream is greatly concentrated, making it easier to capture and compress.

Post-combustion systems separate CO2 from the flue gases produced by the

combustion of coal in air. Post-combustion CO2 capture technology, based on

chemical absorption processes, is already proven and commercially available in

the oil and gas industry. It is the closest to large –scale commercial deployment

for power generation but not yet at the scale required.

ADVANCED COMBUSTION SYSTEMS

The workhorse of America’s electric power is the coal fired power plant. Today,

coal combustion plants account for more than half of the nation’s electric power

generation. Largely because of these plants, U.S. consumers benefit from some of

the most affordable power in the world.

The technology of burning coal has made remarkable advances in the last quarter

century and much of this progress is due to federal research and development

partnerships with private sector developers.

In the 1900s, fluidized bed combustion (i.e. a process that removes pollutants

inside the coal boiler) was termed “the commercial success story of the last

decade “ by a major power industry publication. The first new coal-fired power

plant to be built in Illinois in more than 15 years will employ a new type of “low

emission boiler” technology developed in the federal government’s energy

program. Innovations in burner designs, refractory materials and high-

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temperature heat exchangers are all products of the department of energy ‘s

research program into cleaner, more efficient ways to burn coal. A good example

of an advanced combustion system is a fluidized bed combustion system.

Fluidized bed combustion (FBC)

Fluidized bed combustion (FBC) is a combustion technology used to burn solid

fuels. In its most basic form, fuel particles are suspended in a hot, bubbling

fluidity bed of ash and other particulate materials (sand, limestone etc.) through

which jets of air are blown to provide the oxygen required for combustion or

gasification. The resultant fast and intimate mixing of gas and solids promotes

capable of burning a variety of low-grade solids fuels, including most types of coal

and woody biomass, at high efficiency and without the necessity for thermal duty,

FBCs are smaller than the equivalent conventional furnace, so may offer

significant advantages over the latter in terms of cost and flexibility. FBC reduces

the amount of sulfur emitted in the form of Sox emissions. Limestone is used to

precipitate out sulfate during combustion, which also allows more efficient heat

transfer from the boiler to the apparatus used to capture the heat energy

( usually water tubes). The heated precipitate coming in direct contact with the

tubes (heating by conduction) increased the efficiency. Since this allows coal

plants to burn at cooler temperatures, less NOx is also emitted. However, burning

at low temperatures also causes increased polycyclic aromatic hydrocarbon

emissions. FBC boilers can burn fuels other than coal, and the lower temperatures

of combustion (8000c/ 15000 F) have other added benefits as well.

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Conclusion

Global warming from the increase in greenhouse gases has become a major scientific and political issue during the past decade.All attempts have been made to reduce the effect this has on the earth surface which has been succinctly illustrated in this paper.Sources of greenhouse gasse can come from burning of fossil fuel,deforestation,farming,industrial waste and landfills.The effect of greenhouse gas has been cotrolled

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REFERENCES

Wright, L., Kemp, S., Williams, I. (2011) 'Carbon footprinting': towards a universally accepted definition. Carbon Management, 2 (1): 61-72.

UK Carbon Trust (2008) "Carbon Footprinting". Parliamentary Office of Science and Technology POST (2006).

Carbon footprint of electricity generation. October 2006, Number 268

Wiedmann, T. and J. Minx (2008). A Definition of 'Carbon Footprint'. Ecological Economics Research Trends. C. C. Pertsova: Chapter 1, pp. 1–11. Nova Science Publishers, Inc, Hauppauge NY, USA. catalog also available as ISA-UK Research Report 07/01

World Energy Council Report (2004). Comparison of energy systems using life cycle assessment.

Energetics (2007). The reality of carbon neutrality. Walkers Carbon Footprint The LCA Resources Directory in Europe and beyond webpage

http://lca.jrc.ec.europa.eu/lcainfohub//directory.vm

European Platform on Life Assessment, European Commission-Joint Research Centre Institute for Environment and Sustainability

http://lca.jrc.ec.europa.eu/ http://lca.jrc.ec.europa.eu/EPLCA/mailing.htm

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