Agricultural Bioenergy Production

Abstract

World population and energy consumption per capita have highly increased significantly during the last two centuries. At the same time the relative contribution of bioenergy has decreased and been replaced by fossil fuels. However, these fossil resources will eventually become exhausted and their use is causing social and environmental problems. Hence in many regions the use of bioenergy is promoted by law. The role of agriculture in the production of bioenergy feedstock is predicted to increase and therefore minimising potential social and environmental risks is essential. For this purpose balanced analyses on the impacts of the different bioenergy crops and of new conversion technologies are required. This review reveals that very sophisticated matrixes of biorefinery are theoretically available. The greatest attention has been paid to technologies of producing transport-fuels from lignocellulose and therefore an increased demand for this type of feedstock can be expected. Besides the high concentration of material that is needed for a specific bioenergy conversion method, the choice of potential bioenergy crop species should also be taken into account in relation to the local weather conditions since both the natural species and genetically modified cultivars can only perform to their full growth potential under optimal growing conditions. Unfortunately there is no clear picture available about trends in areas under energy crop cultivation. For a deeper analysis of both the economic and ecological attributes of different crops and patterns of common practice we used the wide-spread classification of different generations of energy crops. In general, both the investment costs and potential ecological benefits increase with each generation and therefore special support mechanisms are required in order to increase the area of dedicated and multiannual energy crops. The impact of land use change can be diminished by better utilisation of areas experiencing human population decline especially through the cultivation of perennial crop, since its carbon sequestration is greater than that of annual food crops. To help reduce greenhouse gas emission the number of work operations in the field should be kept to a minimum and use of wastewater or sewage sludge instead of mineral fertilizers should be considered. Biodiversity can be protected by planting of scattered areas of perennial crops and avoidance of potentially invasive species. The ecological benefits of bioenergy production can be increased by more efficient utilization of by-products. Manure, straw or biomass from high conservation-value grasslands can be used for bioenergy production, if their feedstock-specific characteristics are taken into account to protect the environment. All these activities should be incorporated into the goal of energy saving and should be a platform for establishing good practice standards of bioenergy production in agriculture.