Possibilities and limitations for sustainable bioenergy production systems

Abstract

The focus of this thesis is on the possibilities and limitations of sustainable bioenergy production systems. First, the potential contribution of bioenergy to the energy supply in different world regions in the year 2050 from different biomass sources (dedicated woody energy crops, residues and waste and biomass from forest growth) is analysed. The results show that particularly the potential of dedicated crops produced on land that is no longer required for the production of food can be very large in various world regions. However, a reduction of the area of agricultural that is needed to cover the demand for food requires substantial increases in the efficiency with which food is being produced through the application of state-of-the-art technologies, which are not realistic considering current socio-economic trends. Next, the possibilities and limitations of a certified production of short rotation coppice in Brazil and Ukraine and ethanol from sugar cane in Brazil are investigated. Compliance with sustainability criteria may require changes in the management of energy crop production or in the operation of processing plants that may limit the potential or increase the costs of bioenergy. Potential bottlenecks are the impacts on biodiversity and food security, because of the increase of the area of land used for the production of energy crops. Genetically modified sugar cane is currently being developed, but not (yet) applied. Both a ban on and an allowance of the use of genetically modified cane could become a bottleneck, considering the potentially large advantages as well as disadvantages involved. Both are highly uncertain at this moment. Compliance with most other environmental and socio-economic criteria can be guaranteed at limited additional costs and using existing certification systems. Further, special attention has been paid to the impact of fertilizer- and manure-induced nitrous oxide (N2O) emissions from energy crop production on the reduction of greenhouse gas (GHG) emissions when replacing conventional transportation fuels by first-generation biofuels (taking into account also other GHG emissions across the life cycle) is analysed. The results show that N2O emissions can be very important for the GHG balance of biofuels depending, amongst others, on the type of land use that is replaced by energy crops. Finally, the economic performance and environmental performance of switchgrass and miscanthus production chains in the European Union are analysed. The results show that miscanthus and switchgrass have a favourable and robust greenhouse gas and energy balance compared to oil and natural gas. Miscanthus and switchgrass can be produced in East Europe at competitive costs compared to fossil fuels. Also the impacts on biodiversity can be favourable, provided that attention is paid to the harvest regime and the size and location relative to existing areas of natural vegetation.