Temps de lecture :5 minutes
Three types of biofuels
Agrofuels (also called biofuels) are agriculture-based fuels. There are three main types: alcohol-based agrofuels which are used in petrol engines; oil-based agrofuels which are used in diesel engines; and agrofuels made of gas.
Alcohol-based agrofuels are produced from plants rich in sugar such as sugarcane or sugar beet, or from plants rich in starch, such as wheat. These agrofuels include bioethanol and its derivative ETBE (Ethyl tert-butyl ether).
The oils are extracted from oleaginous plants such as rapeseed, palm, sunflower or soybean. They can be pure vegetable oils, referred to as “raw oils” (these are sometimes cooking oils), or processed products. In the latter case, one speaks of diester, biodiesel or VOME (vegetable oil methyl esters). Both are made from 90% oil and 10% methanol, a petroleum derivative.
The gases are produced by fermenting organic matter. The resultant biogas (methane) is also known as motor vehicle natural gas.
Agrofuel production is agriculture-based and therefore varies from one country to another. In Brazil, they are produced from sugarcane, whereas they are produced from corn in the USA, and from beets (70%) and cereals (30%) in France.
In 2007, Brazil and the USA alone accounted for nearly 90% of the world’s annual production of ethanol, which was around 50 billion litres. As for VOME, global production reached 4 million tons, of which 88% was produced by Europe (44% by Germany, 22% by France and 17% by Italy).
Agrofuels represent 40% of fuel consumed on roads in Brazil, while they onlyn account for 1.5% in the United States and 1.2% in Europe. A European Commission directive has set a target of 5.75% agrofuel content in petrol and diesel fuel by 2010. The French government has declared that it wishes to gio further and increase the biofuel content by 7% by 2010.
Energy has to be used to produce agrofuels : to produce the fertilizers and the pesticides, to run the agricultural equipment, to transport the plants to the plant where the agrofuels are produced, to make this plant work etc. An important parameter in judging the extent to which agrofuels are useful is therefore that of energy efficiency : whether the energy that is produced by the agrofuel is worth the energy that had to be used to make it.
Estimations vary, but, according to an ADEME study, the energy efficiency of alcohol made from Brazilian sugar cane is excellent : it is worth 5.82. Other agrofuels are less energy efficien : 2.23 for rapeseed diester, 1.35 for wheat and 1.25 for sugar beet. For corn-based ethanol, it is less than 1 which means that it releases less energy than it takes to produce !
According to the Ministry of Agriculture and consumer associations, in the United States, 1 litre of fuel is needed to produce 1.2 litres of corn ethanol which can allow one to cover the same distance as with one litre of petrol made out of oil.
Greenhouse effect and deforestation
As they grew, the plants which are used to make the agrofuel absorbed the CO2 (carbon dioxide) which is released during its combustion. The total amount of greenhouse gas emissions from agrofuels is therefore reduced. It is lower than that of conventional fuels by at least 53% for VOME, and by about 30% for ethanol.
However, one must take into account the fact that large forested areas are destroyed to make way for palm oil plantations. In Malaysia, 87% of the deforestation between 1985 and 2000 was due to oil palm planting. The primary forests of Sumatra are experiencing a similar fate. In Brazil, sugarcane culture is also leading to deforestation. All this deforestation causes high emissions of greenhouse gases. It is also destroying the habitat of many endemic species.
Impact on food security
The current increase in agrofuel production is partly occurring at the expense of food production. But all the planet’s agricultural surfaces would not be enough to replace all the oil/ petroleum by-products which exist.
According to the OECD, the United States, Canada and Europe (the EU-15) would each have to devote between 30% and 60% of their current cultivated land to replace a mere 10% of their fuel consumption with biofuels! (5)
According to INRA (French National Institute for Agricultural Research), the inclusion of 5.75% of agrofuels in motor vehicle fuel by 2010 would require the use 18% to 20% of the arable land. And that would only reduce oil imports by 3%.
According to the INRA (French National Institute for Agricultural Research), incorporate 5.75% biofuels into gas and diesel by 2010 would lead to between 18% and 20% of arable land being used. And this would only reduce oil imports by 3%.
Moreover,the increase in the demand for biofuels is fuelling the rise in agricultural prices.
New agrofuels could show more positive results. They are called second-generation agrofuels and are made from cellulose,a molecule which can be found in all plants. They do not have to be food-crop based and can also be made using parts of non-edible plants; straw, trees or algae. Thus, their production does not compete with agricultural surfaces and requires little input (fertilizers, water, energy). The use of ligno-cellulosic ethanol could therefore enable greenhouse gas emissions to be reduced by 78% and the consumption of non-renewable energy to be reduced by 76%.
Different ideas are being toyed with. According to INRA, Miscanthus, a hybrid grass which is very rich in ligno-cellulose, provides three times more energy than wheat and emits less CO2 than it stores during its combustion ; part of it is stored in its rhizomes. Some species of microscopic algae can synthesize oils which, once extracted, can be processed in the same way as traditional vegetable oils. Their yield per hectare could be thirty times greater than that of rapeseed, and their cultivation would absorb large amounts of CO2.
A tropical plant called Jatropha curcas, which grows in semi-arid environments, could also be an interesting source of VOME. A British company is currently cultivating thousands of hectares of Jatropha in China, India and Africa.
Finally, the “biomass to liquid” (BTL) option makes it possible to convert biomass (waste, plants not grown for food) using a reactive gas (water, dioxygen). The gas obtained is mainly made up of carbon monoxide and dihydrogen and can be turned into either gasoline or diesel oil. Fuel made in this way does not contain any sulphur or nitrogen and emits less particles when combusted.
Brazil, the world’s second largest producer of ethanol (via sugarcane), has 340 factories which produced 490 million tonnes (mt) in 2007. This was an 8 % increase compared to 2006. The government forecasts production levels of 730 mt by 2012. For investors, this means the construction of 90 new plants and the cultivation of an extra four million hectares. In 2012, sugarcane could thus cover 10.3 million hectares. This faith in the future of agrofuels is causing the inflation of land prices (+113% in the State of Sao Paulo for instance). And whilst it seems that the single-crop farming of sugarcane is set to become the trend, Brazil is importing an increasing amount of its food supplies.