Estimation of the future technical potential of biomass as an energy source is dependent on assumptions with respect to land availability and productivity as well as conversion technologies. With the emergence of energy crops as the major source of biomass fuel, land use conflicts, especially in relation to food production, may arise. However, with efficient agricultural practices, plantations and crops could supply a large proportion of energy needs, with residues playing a smaller role without compromising food production or further intensifying agricultural practices.
Considering future projections of increasing energy and food demands associated with increasing standard of living and population, pressure on the availability of land is likely to increase. In the European Union (EU) it has been proposed that biomass could contribute an additional 3.8 EJ annually by 2010, compared with the contribution of 1.9 EJ. Energy crops are expected to provide this extra capacity on 4% of the total land area of the EU. If all of this 1.9 EJ replaced energy from coal in Western Europe, reductions of net CO 2 in the order of 50 MtCyr(-1) or more than 7% of the current anthropogenic CO2 emissions from the region could be expected.
Heat and power generation through internal combustion is still the most common method of generating bioenergy, using the same technology used in power plants burning solid fossil fuels. Co-firing biomass with coal in existing electricity generation plants is becoming more widespread and may be one of the most promising near-term options for increasing market share of bioenergy. With low capital input, fuels such as waste wood, crop debris, forestry residues, and agricultural wastes can be mixed with coal to reduce net GHG emissions. The technique is being developed in the European Union and the United States where biomass has been successfully co-fired with coal at around 10% without compromising energy efficiency technologies. If 10% of the 50,000 PJ of electricity generated each year from coal were to be replaced with biomass feedstock productions in only 10% of installations, approximately 350 MtCO2 yr_ 1 emitted to the atmosphere could be offset. Co-firing offers additional environmental benefits associated with reduced NO x and SO x emissions from conventional generating plants.
Technological advancements in the production of liquid biofuels such as pyrolysis are at the pilot stage, and new processes for the production of ethanol from woody biomass have been developed, however, they are not yet commercial. In developing countries, efficiency of conversion technologies is also being increased. For example, in India, traditional cooking fires are being replaced with improved higher efficiency cooking stoves, and biogas produced from anaerobic digestion of animal and other wastes is now used for cooking, lighting, and power generation. Modernizing biomass production and bioenergy energy conversion technologies will transform this traditional energy source to one that is feasible and widely acceptable and ultimately offer significant GHG reductions.
Although the majority of energy sourced from biomass is converted through combustion, and some through liquification to alcohol, the adoption of new technologies such as gasification can improve the power production efficiency of biomass and bioenergy. Increasing efficiencies in conversion and the global economy will determine to what extent biofuels can displace CO 2 emissions into the future.
