The original biofuel, as used in the discovery of fire and a firm favourite for millions of years.
Jargon: ‘Biomass’ usually means wood.
Current use: Around 90 per cent of all biofuel use is locally harvested wood, charcoal and dung for small cooking stoves. Thirty-eight per cent of the world’s population rely on this energy, and its pollution kills around 1.5 million people per year. The single biofuel technology that could provide the greatest benefit to the world is probably the cleaner-burning wood stove.
New ‘biomass’ power stations are springing up around the US, and are proposed for Britain. Where the extra millions of tonnes of wood per year will come from is not yet clear.
Methane from waste
Methane from sewage and domestic waste – in use for thousands of years.
Jargon: Biogas or biomethane.
Current use: With the help of new anaerobic digesters (which convert food waste into methane gas and organic fertilizer), around 30 million homes in China and India now make their own cooking and heating gas in this way. Also has potential as vehicle fuel – but waste is not an unlimited resource, and overall more energy (and carbon) would be saved by producing less waste in the first place! Some companies are talking about making biogas by fermenting new crops rather than from waste, which would have the same problems as liquid biofuels (see 4-7).
Recycled cooking oil
Waste oil from restaurants and fast-food joints which is reprocessed into fuel.
Jargon: Confusingly, fuels made from vegetable oils are often referred to simply as ‘biodiesel’, whether they are recycled or made from new crops.
Current use: There’s only a limited amount of waste oil sloshing around. Even if all the available waste oil in the US were poured into its cars, it would replace less than 0.1 per cent of the nation’s liquid fuels.
Ethanol and biodiesel
Ethanol is made from sugary or starchy crops such as corn, sugar cane, wheat, sugar beet and barley. Biodiesel is made from oily crops such as soybean, rapeseed, oilseed and oil palm.
Jargon: ‘First generation’ biofuels.
Current use: These make up nearly all of the existing liquid biofuels. The biggest producers are the US (around 40 billion litres of corn ethanol per year) and Brazil (25 billion litres of sugar cane ethanol). Biodiesel production is much lower – less than 20 billion litres per year for the whole world.
Many countries are already blending these biofuels in with their transport fuel supply – around 3 per cent biodiesel in the EU, and 10 per cent ethanol in the US
Liquid biofuel from wood and grasses
High-yielding non-food crops which can be grown on so-called ‘marginal land’.
Jargon: Cellulosic, or ‘second generation’ biofuels.
Current use: Still at the research stages. The plan is to make ethanol or other liquid fuels from the carbon in the cellulose of plants like elephant grass and willow. ‘Marginal land’ is a brilliantly vague term – most land in the world is being used by someone for something, or is important for ecosystem maintenance. This technique could be useful for growing some specialized fuels on a limited scale under careful control, but otherwise it could gobble up grazing land, wilderness, or end up on arable land anyway to improve yields and make a bigger profit.
Liquid fuels from agricultural waste
From waste such as corn stover – the leftover bits which aren’t eaten by humans.
Jargon: Sometimes grouped together with second generation biofuels, sometimes termed third generation. They’re also cellulosic (made from the carbon in cellulose).
Current use: Also still at the research stage. This could be a useful source of liquid fuel on a local, well-managed scale, but in mass production it could end up creating serious problems. Some ‘wastes’ like straw have many other uses that would need to be provided by other materials instead; crop residues are also important natural fertilizers, and would need to be replaced by alternative inputs.
These can be macro-algae (seaweed) or micro-algae (pond scum). Can be grown in the sea or in tanks, and so don’t require agricultural land.
Jargon: Second, third, or even fourth generation, depending on whom you speak to.
Current use: This supposed ‘wonder fuel’ is still in development (and not expected for at least a decade). The huge seaweed farms proposed for the ocean could cause the same sort of problems – reduced biodiversity, unpredictable knock-on ecosystem effects and fertilizer leakage – as land-based monocultures. Tiny oil-producing algae in tanks still need large amounts of space, water, sunlight – and, crucially, nutrients. No-one is clear where these nutrients will come from – the algae will be competing with food crops here, especially for phosphates. The algae are expected to be genetically modified to churn out as much oil as possible – so what happens if (or when) they get loose into streams, rivers and reservoirs?
WGBU, Future Bioenergy and Sustainable Land Use 2008; nin.tl/mig7A6
Biofuels Digest nin.tl/itTSti
Dept of Biological and Agricultural Engineering, University of Idaho nin.tl/m7vYcF
World Bank Policy Research Working Paper 5364. Biofuels: Markets, Targets and Impacts, July 2010.
REN21, Renewables 2010: Global Status Report, September 2010. nin.tl/kKowSx
ETC Group, The New Biomasters: Synthetic Biology and the Next Assault on Biodiversity and Livelihoods, February 2011.
Photos: Md. Didarul Alam Chowdhury / Drik / Majority World; Daniel under a CC Licence; stellar678 under a CC Licence; tallpomlin under a CC Licence; 24oranges.nl under a CC Licence
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