Land and climate effects of bioenergy - Brazilian sugarcane ethanol and combined biofuel-district heating in Europe

Doktorsavhandling, 2016

According to the Intergovernmental Panel on Climate Change, use of fossil fuels is the largest source of the increase in atmospheric CO2. The second largest is land use change. To reach stringent climate targets, emissions from fossil fuel combustion and land use change will need to be reduced to near zero within a few decades. Biomass is a renewable energy source that can be used to replace fossil fuels. However, it is a limited resource, expected to become scarce relative to future demand, prompting interest in optimizing efficiency. Further, when biomass for biofuels expands into new land areas, the total biospheric carbon stock (the sum of soil and above-ground carbon) may increase or decrease, influencing the net effect on greenhouse gas balances. This thesis, which consists of five separate papers, analyzes several key aspects associated with two bioenergy systems: (i) combined biofuels and district heat production in the EU and (ii) sugarcane for ethanol production in Brazil, with special attention to integration with existing food and energy systems. The overall aim is to investigate specific options for improving management of land use and land use change, efficient use of resources, and greenhouse gas balances for specific bioenergy systems. In Paper I, we study biomass gasification for the production of biofuels and heat for district heating systems in Europe. We find that each investigated country, except Italy, has a heat sink capacity in its district heating systems that is larger than the amount of heat that would be co-generated in plants producing biofuel volumes corresponding to national biofuel targets. In Papers II–V, we study expansion of sugarcane ethanol production in Brazil at the regional, state, and national levels, including both conventional sugarcane ethanol systems and combined ethanol-milk production systems in which sugarcane residues are used as animal feed. We find that the harvest method influences greenhouse gas emissions from sugarcane-based ethanol production, as does the impact on soil carbon content. How the by-product bagasse is used also affects the results. For Paper V, we interview Brazilian farmers and landholders regarding their actions connected to engaging with sugarcane production. We find that it is common among the interviewees to invest profits from sugarcane production to maintain and improve the prior beef and milk production systems. This likely affects indirect land use change associated with sugarcane expansion on former pasture land.