Biofuel: Difference between revisions

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Biofuel is a type of fuel which is made using animal or plant-based resources which are regenerated quickly. Biofuels are hence different from fossil fuels as although fossil fuels too are created trough anaerobic decomposition of buried dead organisms, this process takes a very long time (exceeding millions of years). This means that -unlike fossil fuels- biofuels are a form of closed-end recycling, whereby the waste product goes directly into production of the fuel. Like fossil fuels, biofuels are a form of indirect solar energy.

Background

Biomass residues can be used as is (solid biomass) or 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.

The large growth in the use of biofuels has promoted large scale mono-crop feedstock production and associated problems.

Localised decentralised biofuel production from feedstock grown using sustainable agricultural practices been shown to offer part of a sustainable energy portfolio.

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.^{[1][2][3][4][5]}

Pollution

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.^[6]

Types of biofuel

First generation biofuels

'First-generation (or conventional) biofuels' are biofuels made from substances in crops (ie sugar, starch, and vegetable oil) that can be used for human consumption. Due to this, the production of fuel from these crops effectively creates problems in regards to the global food production.

Solid biofuels

See wood, sawdust, grass trimmings, charcoal, agricultural waste, and dried manure.

Bioalcohols

These include ethanol and methanol. See Alcohols as fuel.

Biodiesel and green diesel

See biodiesel

Pure Plant Oil and Waste Vegetable Oil

See vegetable oil as fuel

Biogas

See biogas

Syngas

See syngas

Second generation biofuels

'Second generation biofuels' are biofuels produced from made from substances in crops (ie cellulose) that can not be used for human consumption.

Cellulosic ethanol

Wood can be converted to ethanol yet at present (2007 D.C.) it is not yet a economicly viable method.^[7]

Algae fuel

See algaculture

Biohydrogen

Biomethanol

DMF

BioDME

Fischer-Tropsch diesel

Bbiohydrogen diesel

Mixed alcohols

Wood diesel

Use

With most biofuels the incompatibility with available engines provides an additional barrier to the adoption as reliable operation requires expensive engine modifications. 'Flexi-fuel' engines are available in some regions, commonly spark ignition engines able to run straight petrol(US-gas) or petrol/ethanol blends. Additives (bio ethers) can be applied to fuels to improve their performance.

Use in heat engines

It is possible to use biofuels in several heat engines, including internal combustion engines (diesel, gasoline) and Stirling engines. Reliability and performance of the engine will depend on:

• biofuel material compatibility - the compatability of fuel system and engine components to the fuel
• engine parameters: such as fuel delivery or spark timing, being optimised for the given fuel
• a suitable maintenance regime

Use in diesel engines

It is possible to use a wide range of biofuels in a diesel engine, most commonly lipid based biofuels are used either in their pure form, pure plant oil, or transesterified as biodiesel. Diesel engine fuel delivery can be altered to suit the fuel. See also: http://en.wikipedia.org/wiki/Diesel_engine

Use in gasoline engine

See http://en.wikipedia.org/wiki/Internal_combustion_engine

Use in Stirling engine

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External links

• Wikipedia:Biofuel
• Open Biofuel Engine Development - Collaborative biofuel engine tuning
• Biofuel Bay - Biofuel primer and educational resource
• Biofuel Debate Forum - Biofuel, Biodiesel and Bioenergy discussion forum