Projections of the availability and cost of residues from agriculture and forestry

Abstract

By-products of agricultural and forestry processes, known as residues, may act as a primary source of renewable energy. Studies assessing the availability of this resource so far offer few insights on the drivers and constraints of the available potential, the associated costs and how the availability may vary across scenarios. This study projects long-term global supply curves of the available potential by using consistent scenarios of agriculture and forestry production, livestock production and fuel use from a spatially explicit integrated assessment model. Particular attention is paid to the drivers and constraints. In the projections residue production is related to agricultural and forestry production and intensification, and the limiting effect of ecological and alternative uses of residues are accounted for. Depending on the scenario, theoretical potential is projected to increase from approximately 120 EJ/yr today to 140-170 EJ/yr by 2100, coming mostly from agricultural production. In order to maintain ecological functions approximately 40% is required to remain in the field, and a further 20-30% is diverted towards alternative uses. Of the remaining potential (approximately 50 EJ/yr in 2100), more than 90%, is available at less than 10$2005/GJ. Crop yield improvements increase residue productivity, albeit at a lower rate. The consequent decrease in agricultural land results in a lower requirement of residues for erosion control. The theoretical potential is most sensitive to baseline projections of agriculture and forestry demand; however this does not necessarily affect the available potential which is relatively constant across scenarios. The most important limiting factors are the alternative uses. Asia and North America account for two thirds of the available potential due to the production of crops with high residue yields and socioeconomic conditions which limit alternative uses.