Introduction
Bio-energy, is obtained from organic matter, either directly from plants or indirectly from industrial, commercial, domestic or agricultural products and waste.
The use of biomass is generally classed as a carbon-neutral process because the carbon dioxide released during the generation of energy is balanced by that absorbed by plants during their growth. However, it is important to account for any other energy inputs that may affect this carbon-neutral balance on a case-by-case basis, for example any use of fertiliser, or energy consumed in vehicles when harvesting or transporting the biomass to its point of use.
Since the bio-energy can provide an income, it is a way of paying for CO2 mitigation and land restoration. To derive maximum benefits, bio-energy production and use must be modernised. Developing countries have been particularly instrumental in pushing modernisation of biomass for energy as they are so heavily dependant on it, and likely to remain so. Both developing and industrialised countries are now realising they can benefit environmentally and economically.
Biomass
Biomass are the residues obtained from pulp and paper operation, agricultural and forestry wastes, urban wood wastes, municipal solid wastes and landfill gas, animal wastes and terrestrial and aquatic crops grown solely for energy purposes, known as energy crops. In large quantities, the biomass source is called a feedstock.
Biomass can be burnt directly or it can be converted into solid, gaseous and liquid fuels using conversion technologies such as fermentation to produce alcohols, bacterial digestion to produce biogas, and gasification to produce a natural gas substitute. Burning plant biomass as a fuel source does not result in net carbon emissions since the bio-fuels will only release the amount of carbon they have absorbed during growth (providing production and harvesting is sustainable). If these bio-fuels are used instead of fossil fuels, carbon emissions from the displaced fossil fuels are avoided as well as other associated pollutants such as sulphur. The development of large-scale energy production from biomass will rely on specifically-grown energy crops. Nevertheless residues (from forestry, crops and dung) are invaluable as an immediate and relatively cheap energy resource. Wood can also be removed in a sustainable manner from existing secondary forests and plantations.
Biomass is already the fourth largest source of energy in the world supplying about 13% (55 EJ/yr; 25 million barrels of oil equivalent) of 1990 primary energy. It is also considered one of the main renewable energy resources of the future due to its large potential, economic viability and various social and environmental benefits. It is estimated that by 2050 biomass could provide nearly 38% of the world's direct fuel use and 17% of the world's electricity.
Biogas
Biogas is a mixture comprising mainly methane and carbon dioxide. It is produced when organic matter decomposes in the absence of oxygen. This can take place in a landfill site to give landfill gas or in an anaerobic digester to give biogas. Sewage gas is biogas produced by the digestion of sewage sludge.
Landfill gas:
Landfill gas is a mixture comprising mainly methane and carbon dioxide, formed when biodegradable wastes break down within a landfill as a result of anaerobic microbiological action. The biogas can be collected by drilling wells into the waste and extracting it as it is formed. It can then be used in an engine or turbine for power generation, or used to provide heat for industrial processes situated near the landfill site, such as in brickworks. Landfill sites can generate commercial quantities of landfill gas for up to 30 years after wastes have been deposited. Recovering this gas and using it as a fuel not only ensures the continued safety of the site after land filling has finished, but also provides a significant long term income from power and/or heat sales.
Anaerobic digestion:
The biological processes that take place in a landfill site can be harnessed in a specially designed vessel known as an anaerobic digester to accelerate the decomposition of wastes. Anaerobic digestion is typically used on wet wastes, such as sewage sludge or animal slurries but the biodegradable fraction of municipal wastes can be added to wetter wastes to increase the biogas output.
There is no evidence to suggest that biomass production will conflict with food production, and with agro-forestry and integrated farming systems there is evidence that it could in fact enhance agricultural output.
Bio-fuels
Solid biomass can also be converted into liquid fuels that power cars, engines including those in diesel generators, and even industrial operations. Methanol, ethanol, biofuel and biodiesel can all be created from biomass.
Methanol is a wood alcohol which is not as efficient as gasoline as a fuel.
Ethanol, or ethyl alcohol, is a clear, colorless, flammable oxygenated fuel currently added as a gasoline additive to increase octane and lower tailpipe greenhouse gas emissions. It is biodegradable and water soluble. Ethanol (which comes from cellulosic biomass such as corn) is produced through fermentation at either a dry mill or at a wet mill. The dry mill process is simpler than the wet mill process. The wet mill breaks the corn into its components and processes each separately. In addition to ethanol, both processes also create distiller's grain, which is fed to farm animals.
Up to 24% ethanol can be added to gasoline before engine modifications are necessary. A blend known as E85, which is 85% ethanol and 15% gasoline, can be used to power flexible fuel vehicles (FFVs). Many cars on the market today are already built to run on E85. Brazil has had much success converting nearly all of its vehicles to run on E85 made from sugar. It even announced that it would stop importing oil by the end of 2006.
Ethanol has a better environmental profile than gasoline as measured at both the production facility and the tailpipe. Ethanol production plants produce less carbon dioxide, methane and particulates than gasoline refineries, which help meet clean air standards. A blend of 10% ethanol, or E10, yields a 26% reduction in greenhouse gases when compared to gasoline alone. For more information on ethanol is available on the Renewable Fuels Association website.
Biodiesel is the result of combining alcohol (including ethanol) with oil extracted from soybeans, rapeseed, animal fats, or other biomass. Biodiesel can be produced from any fat or vegetable oil, such as soybean oil often sold as 2% (B2) or 10% (B10) blends with diesel. �Concerns that biodiesel can't perform or flow well in adverse weather are based on myths,� Biodiesel performs very well in cold climates and is being used in airport snowplows and school buses. It also burns much cleaner than traditional diesel, making it more environmentally friendly.
Future biological methods for atmospheric CO2 reduction include laboratory based research on photobiology and photobiochemistry. Photobiology (efficient microalgal growth in photobioreactors and tanks/ponds to remove CO2 from flue gases) can provide a source of energy, chemicals and food, while wastes can be converted or recycled into useful byproducts (eg. fertilizer). Photobiochemical systems use the CO2 fixing enzyme Rubisco to store energy via organic compounds. These photobiological systems have a considerably higher photosynthetic efficiency than conventional biomass systems, and do not require high quality land or water so would not compete with agriculture and forestry.
An overview of the status of the bio energy technology developments in the European Union countries is given on the European commission's website , and that for India is available on the Indian Ministry of New and Renewable Energy (MNRE) website.
