Waste and residues of plant, animal or organic origin represent a significant renewable energy resource. Sustainable production management is as important as improving efficiency…

Biomass, the renewable energy source par excellence, is the oldest source of energy used by man. In its so-called "traditional" form (wood derivatives, herbaceous plants or animal waste), it is still the basic energy source for some 1.6 billion human beings who have no access to electricity. For example, in sub-Saharan Africa, as in numerous regions on the Indian sub-continent, in Asia or in South America, biomass is the only source of energy for cooking, lighting and heating for millions of households, sometimes at the risk of uncontrolled usage resulting in deteriorating local ecosystems (deforestation) and polluting emissions that amplify the greenhouse effect…

Towards sustainable management

So-called "commercial" biomass (or bioenergy) is that used for the industrial production of energy, in the form of heat or electricity (combustible biomass) or for transportation (biofuels). In that case, it is a full-fledged renewable energy source that is managed sustainably. It is an almost inexhaustible resource produced by nature, and is consequently attractive for many countries. However, its use requires vast areas and large investments. This limits its use in relation to fossil fuels (coal, gas, oil), of which there are sufficient reserves to dominate the world energy landscape for another half-century.

The first use of combustible biomass was for heat production, sometimes combined with electricity production using a process called cogeneration. In the industrialized countries, it is mainly employed as a secondary energy source at the local level to heat buildings such as schools, private homes, collective housing or for small industrial facilities. Wood-based derivatives and, to a much lesser extent, biogases are the most frequently used forms of combustible biomass.

Although commercial biomass was the second largest source of renewable energy in the world in 2002, after hydroelectricity, its current proportion of use in industrialized countries is low (between 1 and 3%), with the exception of Finland, a country with vast forestry resources, where its use has reached almost 14%. Even a country such as Brazil, the world's leading producer of sugar cane, produces only 3% of its electricity with biomass. In industry, however, the proportion of combustible biomass is higher in developing countries such as Brazil, African nations and India. But as these countries modernize their industry and their demand for energy rises, they will have to turn more and more to other sources of energy, including conventional fossil fuels.

The positive contribution of externalities

Biofuels constitute the other major use of commercial biomass. These liquid or gaseous derivatives of agricultural sources primarily interest the transportation sector, which is almost exclusively dependent on oil and represents more than 30% of the European Union's energy consumption. Production costs are certainly higher than for traditional fuels, but their externalities are attractive.

Because biofuels contribute to the reduction of greenhouse gas emissions and help improve energy self-reliance. They also generate employment through joint development of national energy crops and distillation plants. Additionally, they help sustain agricultural activities that are increasingly environmentally friendly, and they preserve a certain level of biodiversity (optimization of fallow land). However, biofuels are little used compared with fossil fuels. In France for example, some 50 Mtoe (million tons of oil equivalent) are consumed each year, solely in the area of transportation. Experts have calculated that to completely replace oil and natural gas with biofuels derived from sugar beet production (which gives the highest ethanol production yield per hectare), 23% of France's land would have to be used. If we add to this the intermediate energy consumed for fertilizers, farming, harvesting itself, and the whole process of grinding, purification and distillation, that percentage would be more than 120%! Nevertheless, given the geopolitical tensions associated with the oil-producing nations and the increasing price of crude oil, the situation is currently a rather favorable one for biofuels.

Biofuels in the world

Biofuels' role in national economies is largely a consequence of local factors. Brazil, the world's leading ethanol producer with a 70% global market share, is also the world's largest biofuels user (40% of its car consumption). The US, the second-ranked producer with a 23% world market share, has also launched a major program to promote ethanol and biodiesel fuel, but this represents only 1% of their motor vehicle fuels.

Europe, on the other hand, is lagging behind and its legislation only keeps the gap from widening. In 2002, Europe produced only about 2.9 million hectolitres of ethanol, compared with 122 million in Brazil and 76 million in the US. A directive to promote biofuels adopted on April 8, 2003 has set reference goals: sales of biofuels must represent 2% of gasoline and diesel sales in the European Union in 2005 and 5.75% by 2010. To catch up, Europe supports development of the ethanol market through the creation of new distilleries and an increase in suitable energy crops. In the case of France, replacing 5.75% of gasoline with ethanol would result in savings of 918,000 toe, i.e. 1% of its crude oil imports. In addition, since January 2004, EU member states have the option of applying partial or total tax exemptions (except VAT) to biofuels, thus recognizing that the biofuels industry is just starting up and requires specific tax rules to help it develop.

Ecobalance and the greenhouse effect: positive gains

Contrary to other renewable energy sources, combustible biomass – starting with wood – gives off carbon dioxide (CO₂) during combustion. However, their net impact on the greenhouse effect is practically zero, due to the fact that the CO₂ they release to the atmosphere is what was stored by plants during their growth.

For biofuels, the balance is even more positive: replacing 1 liter of gasoline with 1 liter of ethanol results in 75% fewer greenhouse gases being given off. To express this gain in carbon equivalent, we need to consider that one metric ton of ethanol produces 2.7 metric tons less CO₂ than gasoline, and that one metric ton of biodiesel fuel produces 2.5 metric tons less than diesel! Furthermore, by enriching the fuel with oxygen, biofuels improve engine combustion efficiency, thus diminishing atmospheric pollution. In addition, they help reduce gasoline's content of carcinogens such as benzene or aromatics.

Low production yields

Although combustible biomass such as firewood is renewed in a practically natural way, energy crops for the production of biofuels require significant investment, which means that yields are an issue. Upstream, ground cultivation effectively involves significant intermediate energy consumption: drive energy required for mechanization (tractors, equipment for harvesting, grinding and sorting, transportation, etc.) and the spreading of pesticides and nitrogen fertilizers (produced using natural gas as a raw material), whose manufacture requires significant amounts of energy. In addition to their own contribution to greenhouse gas emissions (nitrogen oxides), they have a negative impact on soil and groundwater quality. Moreover, the industrial processes used to distill biofuels, especially ethanol, are in themselves polluting, expensive and energy consuming! The biofuels market would thus appear to require production and processing equipment that significantly compromise overall production yields and are not neutral from an environmental point of view.