Biofuels is a term used to describe all liquid, solid, or gas fuels derived from living organisms, who were alive recently, or their metabolic waste. As a renewable energy source, biofuels have great potential to reduce greenhouse gases. Solid biofuels (biomass), such as wood, manure, and crop residues account for nearly all global bioenergy supplies and are the primary energy source of 2.5 billion people. Rudolf Diesel, the inventor of the diesel engine, ran his 1892 demonstration model on peanut oil, and the Model T Ford, first produced in 1908, ran on ethanol, which Henry Ford described as, “the fuel of the future”. But, the question remains: Is it really a fuel of the future?

At present, the transport sector accounts for 14 per cent of anthropogenic greenhouse gas emissions in the world. Policies that increase fuel prices “at the pump” are met with strong resistance by consumers, so introducing a cost penalty on emissions (example, a carbon tax) is politically difficult for governments. Biofuels, along with more fuel-efficient vehicles, electric and hybrid-electric vehicles, natural gas, and a modal shift (from private car to public transport and bicycles) are all expected to contribute to reducing transport sector emissions. In the longer term, beyond 2030, fuel cells and hydrogen could also make a contribution. This is particularly true at present in Brazil because biofuels now provide over 40 per cent of Brazil’s road transport fuel requirements. However, this figure stands in stark contrast to the less than 2 per cent share of biofuels in global transport fuel consumption. This clearly raises the why? question.

Before we answer the question, is important to see that there are two primary commercial biofuels: first, bio­ethanol, a substitute for gasoline derived from fermented plant sugars and starches and second, bi­odiesel, a substitute for mineral diesel produced by processing plant and animal oils. At present, a 100 per cent substitution of bioethanol for gasoline in standard engines can result in engine damage and a 10–20 per cent loss of power. No­netheless, the difference between gasoline and bioethanol is not great, and blends of up to 10 per cent bioethanol (so called E10) can be used without modification or noticeable loss of power. Research is ongoing into a bioethanol “second-generation technology” that utilises cellulose as the primary feedstock to produce bio­ethanol. There are two primary advantages of second-generation bioethanols. First, they enable fuel to be made from non-food crops, avoiding competition with food production and consequent upward pressure on food prices. Second, feedstock can be grown on margi­nal lands.

Unlike bioethanol, biodiesel can be used up to a 100 per cent direct replacement for fossil fuel-derived diesel. No engine or infrastructure modifications are required, unless being used in extremely cold temperatures, as biodiesel has a slightly higher melting point and may begin to thicken at temperatures below around −15 degree Celsius, in which case small amounts of antifreeze can be added. There are no technical barriers to biodiesel as a replacement for conventional diesel. Nonetheless, even at oil prices of $100 per barrel, most biodiesel production still requires subsidies to be cost competitive.

Biofuels can provide urban air quality benefits as they burn more cleanly and produce less particulate aerosols, but they produce more nitrogen compounds that have other adverse environmental effects. Genetically modified organisms (GMOs) have been proposed as a way to increase productivity and possibly reduce the use of pesticides and fertilisers, but these remain controversial issues and face considerable resistance from some groups. Environmentalists fear that a dramatic expansion in biofuel production to meet mitigation targets will exact a heavy toll on the environment. Similarly, biofuels. produced from food crops (including corn, wheat, and barley), increase demand for grains and directly increase food prices (by up to 50 per cent by 2016), impacting the poor the most.

However, the most significant issue facing a large scaling up of biofuels production is the competition for arable land and the related impact on global food supplies and prices. Already, biofuels production uses around 1 per cent of arable land. If biofuel production increases in line with projections to 2030, they will account for up to 4 per cent of arable land area (equivalent to the area of Australia, Japan and New Ze­aland combined). Other studies estimate that if biofuels were to substitute for 10 per cent of global gasoline and diesel consumption (using existing production methods), they would require 9 per cent of earth’s existing agricultural land area (which might be impossible to generate considering the growing population explosion and greater future food demand).

Second-generation technologies producing bioethanol may alleviate some of these issues and potentially provide land rehabilitation benefits. New research into using algae, seaweed, or plankton as biofuel feedstock may offer hope of alleviating land conflict issues, but these technologies presently remain at the research scale. If it is assumed that biofuels are able to displace 7 per cent of road transport fossil fuels by 2030 (a mid-range estimate), their contribution to greenhouse gas mitigation would be relatively small. At higher growth rates, it is plausible that biofuels could reduce global emissions. However, given the present political, economic and technological constraints on the biofuel technology, its future is presently debatable and uncertain.