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{{Lang|[[Biokraftstoff|Deutsch]] - [[Biofuel|English]]}} | |||
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Revision as of 21:26, 27 February 2008
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Background
Biomass residues can be converted into various non-solid fuel forms. These fuels are referred to as biogas and liquid biofuels. The aim of this conversion process is to improve the quality, specific energy content, transportability, etc., of the raw biomass source or to capture gases which are naturally produced as biomass is micro biologically degraded or when biomass is partially combusted. Biogas is a well-established fuel for cooking and lighting in a number of countries, whilst a major motivating factor in the development of liquid biofuels has been the drive to replace petroleum fuels. In this fact sheet we will be looking at some of these fuels, their applications and the conversion technologies used to derive them.
In Europe and the United States, as well as in several developing countries, there is a move toward cultivating energy crops specifically for the production of biomass as a fuel. The potential for energy production from biomass throughout the world is enormous and as fossil-based fuels become scarcer and more expensive, as carbon emission levels are becoming of greater concern and as people realise the benefits of developing integrated energy supply options, then biomass could begin to realise its full potential as an energy source.
Biomass energy and the environment
There are two areas of environmental concern when considering using biomass as a form of energy. Firstly, there is the issue of land degradation and deforestation. This concern can be addressed by proper management of sustainable energy crops. Although much of the biomass requirement for energy production can be met through utilising residues from the food industry, from agriculture or from commercial activity, careful planning of energy cropping is required to prevent undue stress on the environment.
With the recent global call to reduce carbon dioxide emissions, there is a strong case for promoting the use of sustainable biomass-to-energy technologies worldwide. Using modern technology, enormous reductions can be made in carbon dioxide emissions, particularly if liquid biofuels are used to replace their fossil-based equivalents. In fact, if biomass energy production is done on a sustainable basis, there is little net carbon dioxide addition to the environment.
There are other environmental concerns related to each fuel that need to be kept in mind, such as toxic emissions and production of tars and soots.
References and resources
- Anderson, T., Doig, A., Rees, D. and Khennas, S., Rural Energy Services: A handbook for sustainable energy development. ITDG Publishing, 1999.
- Ravindranath, N. H. and Hall, D. O., Biomass, Energy and the Environment: A Developing Country Perspective from India. Oxford University Press, 1995.
- Karekezi, S. and Ranja, T., Renewable Energy Technologies in Africa. AFREPEN, 1997.
- Kristoferson L. A., and Bokalders V., Renewable Energy Technologies - their application in developing countries. ITDG Publishing, 1991.
- Johansen, T.B. et al, Renewable Energy Sources for Fuels and Electricity. Island Press, Washington D.C., 1993.
Merged material, to be integrated
Biofuels are a form of indirect solar energy, including any fuel that comes directly from biological sources:
- Biogas
- Ethanol
- Gas pyrolisis (wood gas or poor gas)
- Biodigesters
- Methanol
- Wood
Like fossil fuels, biofuels produce carbon dioxide. But unlike fossil fuels, the carbon dioxide produced comes from plants that sucked it out of the air last year, rather than millions of years ago. This means that biofuels are a form of closed-end recycling, whereby the waste product goes directly into production of the fuel.
Pollution is any byproduct that cannot be fed back into the closed-end system. For biofuels, this includes particulates and unburnt hydrocarbons (smoke), oxides of nitrogen, carbon monoxide, and a few others. These are typically much lower level than when fossil fuel is combusted, but they remain a problem.
What is pollution for one technology may be the biofuel in another. For example, if wood is heated anaerobically (with limited oxygen), it produces carbon monoxide, which is normally considered a pollutant, but if collected, can be burnt as a biofuel.
Source: Biofuel from the EcoReality wiki.
Biofuels from cellulose - not yet economic
- Scientists have long known how to turn trees into ethanol, but doing it profitably is another matter. We can run our cars on lawn cuttings today; we just can't do it at a price people are willing to pay.
- The problem is cellulose. Found in plant cell walls, it's the most abundant naturally occurring organic molecule on the planet, a potentially limitless source of energy. But it's a tough molecule to break down...
- No one has yet figured out how to generate energy from plant matter at a competitive price. The result is that no car on the road today uses a drop of cellulosic ethanol. - Cellulosic Ethanol: One Molecule Could Cure Our Addiction to Oil, Evan Ratliff, Wired Magazine October 24, 2007. (The article continues, describing the history of attempts to transform cellulose, and current research.)