electricity generation » biomass » biofuels - Summary of different biofuels and the debate over their use.

Biomass: Biofuels

Biofuels are an incredibly popular topic of conversation these days and it's no surprise why - fuel prices are soaring and as a global community we are becoming increasingly aware of the effect our fossil-fuel consumption is having on the environment. Many believe strongly that biofuels are the solution to this crisis as they are harvested and produced from renewable sources - plant matter, wood, algae, even garbage and sewage can be utilized for their incredible energy potential. The resultant products of the processing of these biomass materials are generally referred to as 'biofuel' though this broad description can be broken down into further distinctions, such as plant oil, biodiesel, biogas, bioalcohol (bioethanol and biomethanol) and solid biofuel.

Debate Over Use

All can be used to generate energy in some form, be it heat, electricity or motion (such as for powering a car). It is important to note that while these forms of energy generation are certainly renewable, they do still emit carbon dioxide into the atmosphere. Supporters argue that as the biomass used would have died and decomposed naturally anyway (and thus released carbon dioxide and methane, amongst other gases) it is better to harvest the biomass' energy potential and channel the emission of the gases towards energy production.

There is also controversy over the effect of biofuel production on food prices: with increasing amounts of agricultural land being given over to producing biofuels, it has been claimed that this has had the effect of reducing the space available for food production, therefore reducing supply and raising food prices. In the long term this may lead to governments turning away from large-scale biofuel projects, but is less likely to affect the adoptiuon of biofuel solutions by individuals, families and small business.

Biodiesel

Generally the most popular biofuel, biodiesel is used all over the world for engine fuel and to a lesser extent for fuelling boilers and stoves (sometimes referred to as bioheat). Aside from being used in diesel-fuelled cars, biodiesel can also be used in trucks, buses and trains. Experimental use of the fuel in aircraft is also under way.

Biodiesel is manufactured from vegetable oil, algae and animal fats through the process of transesterification. Vegetable oil is the most common biomass source (it is cheapest and most readily available), and usually comes from plants that have been grown specifically for the production of biodiesel. Popular crops for this use include those with high sugar or starch content such as sugar cane, sorghum and corn. The process for converting the oil into biodiesel is relatively simple and can be done in a non-industrial setting - it involves heating the oil to remove any water, adding a base (commonly sodium hydroxide) to neutralize the free fatty acids contained in the oil, heating to instigate transesterification, the mixing in of a condensing agent, and then the siphoning off of glycerine, waste products and alcohol. The end product, biodiesel, should be suitable for use almost straight away.

It is important to note that biodiesel fuel is different to straight vegetable oil used as fuel; engines with suitable modifications can certainly take straight vegetable oil (SVO, or sometimes PPO - pure plant oil), whilst biodiesel can be used in any diesel engine.

Other Biofuels

Biodiesel is one of several first generation biofuels, meaning that it has been produced from plant products that have been grown solely for the purpose of creating fuel. Other examples of first generation biofuels include bioalcohols such as biobutanol (generated through the fermentation of sugar or starch and believed to be suitable for use in normal petrol-fuelled car engines) and biogas (created through the anaerobic digestion of any biological matter).

Second generation biofuels, such as biohydrogen and biomethanol, are those which have been manufactured from left-over parts of plants that have already been used for food (stalks, shells, husks and roots which are not edible, for instance). Third generation biofuel is perhaps the most interesting of all the biofuels as it is an up and coming area of scientific research; it involves the growth of algae for manufacturing into algal fuel and biobutanol. Because the British government has introduced the Renewable Transport Fuel Obligation, which states that by 2010 5% of road vehicle fuel must be supplied from renewable sources, it is expected that first, second and third generation biofuels will continue to gain prominence in the fuel market.