Biofuels: from tiny acorns ...
Conventional wisdom holds that only death and taxes are certain in life, but the prospect that one day we will no longer be able to power our vehicles on fossil fuels can safely be added to the list, writes Cris Heaton
WITH GROWING awareness of the need to prepare for this and concerns about energy security and climate change, alternative fuels that can supplement petroleum are attracting increased attention.
Of these, biofuels are one of the most promising, having already captured a small but growing share of the market. The most successful so far has been bioethanol—ethanol made from fermenting crops such as sugar cane and grain, and used as a supplement for gasoline. Modern engines are capable of running on a blend of 10% ethanol with gasoline; higher blends—up to almost pure ethanol—can be used in adapted engines.
Brazil's advanced market
The most advanced bioethanol market is Brazil, where all gasoline contains 22-26% ethanol and flex-fuel cars, which can run on almost pure ethanol, are proving popular. In 2003, about 14bn litres of bioethanol were produced from sugar cane in Brazil, accounting for 30% by volume of the country's gasoline consumption.
The US is the other major bioethanol user, with over 10bn litres produced in 2003, mostly from grain. This amounted to just over 2% of its gasoline market. Most US bioethanol is sold as a 10% blend with gasoline. Bioethanol is less widespread in Europe, but many countries, such as Germany, France and Italy, have established markets for biodiesel—methyl esters produced from fats or oils and methanol. Some modern engines can run on pure biodiesel, although lower blends —less than 25%—are more common.
Europe is the world's largest biodiesel market, but is far smaller than the bioethanol market. Around 1bn litres of biodiesel were produced in Europe in 2003, amounting to less than 1% of EU diesel consumption. But the EU has set a target of 5.75% of all transport fuels to come from biofuels by 2010, which should kick-start the market. 'Europe over the next five to 10 years will grow rapidly in response to the EU's targets,' says Darran Messem, global biofuels manager at Shell.
The most obvious advantage of biofuels is that they reduce oil dependency, which has benefits in terms of the environment and energy-supply security. The relationship is not a straightforward one-to-one swap, because biofuels have a lower energy content than petroleum, so a larger volume is consumed—the difference depends on the blends and type of fuels used. Also, fossil fuels are generally needed to produce biofuels. The IEA estimates that 0.15-0.2 litres of petroleum are used in making one litre of biofuel. However, biofuels can result in lower carbon dioxide emissions than gasoline over the whole cycle, because carbon dioxide released by burning biofuels is partly or wholly compensated for by the amount taken up in growing more biofuel feedstock.
The difference in carbon dioxide emissions varies depending on the methods used to produce biofuels. Studies suggest Brazilian sugar cane bioethanol releases over 80% less carbon dioxide than gasoline. But bioethanol produced from other feedstocks and using more energy-intensive processes may show no reduction.
The variable level of emissions is a problem for efforts to promote biofuels on environmental grounds. 'If the driver is carbon dioxide reduction, it is important biofuels deliver the promised benefits,' says Andrew Owens, the chairman of Greenergy, the UK-based biofuels and low-sulphur fuels supplier. Greenergy operates a carbon-certification system for its fuels, which verifies the level of emissions released during the production process, and Owens says a similar industry-wide standard should be adopted.
Biofuels can also bring agricultural benefits, as the feedstock crops can provide farmers with an alternative market. 'The number one driver in the US and Europe is agriculture policy,' says Lew Fulton, a transport energy specialist at the IEA. 'They are looking for ways to assist farmers as the food prices keep dropping.'
The clear disadvantage of biofuels is their cost. According to IEA figures, the cost of bioethanol and biodiesel is up to three times the cost of petroleum fuels, making them unviable without government support. However, costs vary widely—Brazilian sugar cane bioethanol is nearly as cheap to produce as gasoline, because of high crop yields, low labour costs and use of bioethanol and electricity co-generation plants.
The amount of land needed for biofuels feedstock production may also be a barrier to wider development. With existing technology and feedstocks, the IEA estimates that to replace 5% of the diesel and gasoline consumed in the EU and the US with biofuels would require 20% of the cropland in the EU and 21% in the US. This might be achievable, says the IEA, but higher levels would begin to impact on food production.
'If OECD countries want to go to 15-20% in terms of oil displacement they are probably going to need some help, due to cropland constraints,' says Fulton. This may be resolved by the emergence of an international trade in biofuels, with countries with surplus land producing biofuels for export. 'There should be plenty of capacity in the sugar-cane growing regions—Latin America, Southeast Asia and, eventually, Africa,' says Fulton.
New biofuels production technologies should also reduce the amount of land the feedstock crops need. The closest to commercial use is cellulose ethanol, which produces bioethanol by using enzymes to convert plant cellulose to sugar for fermentation into ethanol. This will make available alternative feedstocks such as grasses and forestry waste.
Cellulose ethanol can also provide higher well-to-wheel greenhouse gas (GHG) emissions reductions than conventional bioethanol, because the non-cellulose part of the plant can be burnt to power the process, in the place of fossil fuels. Reductions depend on feedstocks and the amount of fossil fuels involved in production. Studies in IEA countries in recent years have found GHG emissions from cellulose bioethanol to be between 51% and 107% less than gasoline—a reduction of more than 100% means more carbon dioxide is taken up than released during production.
The technology is close to commercial application, with small volumes of cellulose ethanol now being sold from the 1m litres a year Shell/Iogen medium-scale plant in Canada. Costs are still high but should come down as large-scale plants are built.
Other technologies, such as biomass-to-liquids, where biomass is gassified and the Fischer-Tropsch process applied to produce fuels such as synthetic diesel, are further from commercial use but may prove important in a decade or two.
Biofuels will probably not replace petroleum fuels by themselves. Ultimately, replacing fossil fuels is likely to involve a number of technologies, such as hydrogen fuel cells. But, over the next two or three decades, biofuels have good prospects, because they are at a relatively advanced commercial and technological stage compared with alternatives.
'Hydrogen is the Holy Grail, but it could take a very long time before the hydrogen-fuel-cell world comes about,' says Fulton. 'If you look out to 2050, it is a smart idea for us to be thinking about biofuels as a very important bridging fuel, at the very least.'