Agricultural intensification has the potential to reduce indirect land-use change from biofuels. If such intensification is realised only by applying more fertiliser, this may lead to substantial indirect greenhouse gas emissions. Improvement of fertiliser-use efficiency is essential to prevent these emissions.
Agricultural intensification may restrict indirect effects of bio-energy
Indirect land-use change caused by the cultivation of energy crops on agricultural land is an important issue in the discussion on the sustainability of bio-energy. Displacement of agriculture and resulting conversion of natural areas lead to additional greenhouse gas emissions, potentially outweighing any reductions in greenhouse gas, and to a further loss of biodiversity. Intensification of agricultural production is often suggested as the most important solution to this problem; biofuel crops could be grown on existing agricultural land, and any losses in production of other crops would be compensated, not by expanding agriculture, but by increasing the yield on existing agricultural land. However, intensification can also cause additional greenhouse gas emissions, due to increased fertiliser use and related N2O emissions. Merely increasing the quantity of nitrogen fertiliser - probably the simplest way to produce higher yields - could lead to additional emissions of up to 150 kg CO2 eq per GJ of fuel. If higher yields would be achieved by simultaneous improvement of management, crop varieties and fertiliser input, additional emissions could stay below 5 kg CO2 eq per GJ of fuel.
As large yield increases will also be necessary to feed a larger and wealthier future world population, yield improvements that limit the indirect effects of biofuels need to be larger than they would have been under a business-as-usual scenario, that is, additional improvements need to be made apart from any business-as-usual development.
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