Future carbon footprint reduction for power generation – Ways to mitigate emission:

Future carbon footprint reduction for power generation – Ways to mitigate emission:

The greatest potential for carbon footprint reduction is in conventional fossil fuelled electricity generation, using improved combustion technologies, carbon capture and storage and co-firing with biomass. We tried to examine most the technologies available to know the potential to reduce their carbon footprint.

a. Fossil fuel generation – future carbon footprint - Technology improvements could increase the energy efficiency of existing coal fired plants from current levels of ~35% (where only 35% of the fuel energy is converted into electricity) to over 50% (by using super-critical thermal power plant). Improvements in energy efficiency can halve life cycle carbon emissions in both coal and gas fired plants. Carbon capture and storage (CCS) could potentially avoid 90% of CO2 emissions to the atmosphere in the future.

b. Co-firing fossil fuels and biomass - Co-firing biomass along side fossil fuels in existing power plants can also significantly lower their carbon emissions, because the fossil fuels are replaced by ‘carbon neutral’ biomass.

c. Future carbon footprint reductions in all technologies - Carbon footprints could be further reduced in all electricity generation technologies if the manufacturing phase and other phases of their life cycles were fuelled by low carbon energy sources. For example, if steel for wind turbines were made using electricity generated by wind, solar or nuclear plants. Using fewer raw materials would also lower life cycle CO2 emissions, especially in emerging technologies such as marine and PV. New semi-conducting materials (organic cells and nano-rods), are being researched for PV, as alternatives to energy and resource intensive silicon.

d. Future nuclear footprint & global uranium resources - Some analysts are concerned that the future carbon footprint of nuclear power could increase if lower grade uranium ore is used, as it would require more energy to extract and refine to a level usable in a nuclear reactor. Point is to be noted: if lower grades of uranium are used in the future the footprint of nuclear will increase, but only to a level comparable with other ‘low carbon’ technologies and will not be as large as the footprints of fossil fuelled systems.

Overview of future carbon footprint reduction –

(1) All electricity generation technologies emit CO2 at some point during their life cycle. None of these technologies are entirely ‘carbon free’.

(2) Life cycle inventory analysis is used to measure the amount of CO2 emitted by each technology.

(3) Fossil fuelled electricity generation has the largest carbon footprint (up to 1,000gCO2eq/kWh). Most emissions arise during plant operation.

(4) ‘Low carbon’ technologies have low life cycle carbon emissions (<100gco2eq/kwh).>

(5) Future carbon footprints can be reduced for all electricity generation plants if high CO2 emission phases are fuelled by low carbon energy sources.

Carbon Dioxide Emission by Combustion Fuels:

Carbon Dioxide Emission by Combustion Fuels:

A. Environmental emission of carbon dioxide - CO2 - from fuels like coal, oil, natural gas, LPG and bio energy are responsible for global warming.

To calculate the CO2 emission from a fuel, the carbon content of the fuel are multiplied by the ratio of the molecular weight of CO2 (44) to the molecular weight of carbon (12) -> 44/12 = 3.7.

Approximately environmental emission of Carbon Dioxide – CO2 - from the combustion of different fuels can be approximated from the table below:

Fuel	Carbon Content (kg C/kg fuel)	Energy Content (kWh/kg)	Emission of CO2 (kg CO2/kWh)
Coal (bituminous/anthracite)	0.75	7.5	0.37
Gasoline	0.9	12.5	0.27
Diesel	0.86	11.8	0.24
Light Oil	0.7	11.7	0.26
Natural Gas, Methane	0.75	12	0.23
LPG - Liquid Petroleum Gas	0.82	12.3	0.24
Bioenergy	0	-	0

B. Bioenergy is produced from biomass derived from any renewable organic plant, such as:

(a) Dedicated energy crops and trees;

(b) Agricultural food and feed crops;

(c) Agricultural crop wastes and residues;

(d) Wood wastes;

(e) Aquatic plants;

(f) Animal wastes;

(g) Municipal wastes and other waste materials

Emissions of CO2 can contribute to climate change. Combustion of bioenergy do not add to the total emission of carbon dioxide as long as the burned biomass do not exceed the renewed production. (Emission of CO2 from combusting wood is in reality approximately 0.18 kg/kWh)

C. A variety of biofuels can be made from biomass resources, such as,

(a) Ethanol;

(b) Methanol;

(c) Bio-diesel;

(d) Fischer-Tropsch diesel;

(e) Gaseous fuels like hydrogen or methane.

Carbon emission from bio-fuels:

Carbon emission from bio-fuels:

Bio-fuels are the fuels of solid, liquid or gaseous in nature, which has been derived from bio-mass – recently living organisms or their metabolic byproducts. Thus, it could be oils from plants, manure from cows, wood from trees etc. For example, bio-gas (i.e., gas produced by the biological breakdown of organic matter in the absence of oxygen); bio-ethanol; bio-diesel; straight vegetable oil etc., are the bio-fuels. It is a renewable energy source, mostly have agricultural based, unlike other natural resources such as petroleum, coal and nuclear fuels.

It has been seen that certain social and environmental benefits bio-fuels has as compare to use of fossil fuels, such as reduction of greenhouse gas emission, increased national energy security, increased rural earnings and development and above all, reduction of use of fossil fuel.

Bio-fuels and other forms of renewable energy are thought to be ‘carbon neutral’ or ‘carbon negative’. Carbon neutral or carbon negative is the difference of quantum of carbon produced and emitted to the atmosphere when these are used as fuels and the quantum of carbon absorbed in the process of their growth. If both are same, is called carbon neutral or if quantum of carbon absorbed through photo-synthesis is more than the emission is called carbon negative. Both the cases are advantageous towards environment point of view and reduction of global warming.

Strictly speaking, bio-fuels are neither carbon neutral nor carbon negative. This is because extra energy is required to grow crops and process them into fuel. This extra energy releases extra carbon to atmosphere as emission. For example, plants require fertilizer to grow, requires energy for transportation and processing; this extra energy releases carbon to the atmosphere as emission. Therefore, this emission aspect is to be debated, whether we are really gaining in respect of carbon emission, by using bio-fuel. However, the arid lands can be better utilized if people shift towards bio-fuels; so the rural earnings. The poorly irrigated land mass also can be taken up for cultivation.