Clearing forests to plant energy crops mean use of biomass can lead to additional GHGs, German climate researchers find; with forest protection, biomass can contribute up to 270 exajoules to global energy supply in 2095
August 19, 2011
– Forest protection – safeguarding woodland from being cleared and converted to fields for energy crops – reduces the global economic potential of bioenergy only in the short term. If less additional land is available for cultivation, this can be compensated by higher rates of yield-raising investments. This is shown by a new study. However, following this scenario global food production prices could rise considerably.
Energy from biomass pays even with forest protection in the long term
Generating energy from crops instead of oil and coal can have counterproductive effects. “The use of biomass can lead to additional emissions of greenhouse gases”, says lead author Alexander Popp of the Potsdam Institute for Climate Impact Research (PIK). “This is the case if forests get cut down to plant energy crops instead.” Forests are important CO2 sinks. At the same time, biomass is expected to play an important role in future energy systems.
Therefore, a team of nine researchers investigated the potential of bioenergy constrained by forest protection. “We did not just calculate the biophysical potential”, Popp points out. “We established which amount of bioenergy, competing with other forms of energy, in the end is really cost-effective.” The scientists simulated this with complex computer-based models. The results now have been published in the journal Environmental Research Letters.
For the first time, a global land-use model was coupled with a model of the energy system and a vegetation model in a way that allows dynamic and detailed simulation of the tradeoffs between different factors. Amongst the factors taken into account are technological change, cropland expansion, and the change of dietary patterns in societies with growing wealth.
The outcome is that biomass in 2095 can contribute up to 270 exajoules to the worldwide energy supply – mainly in combination with Carbon Capture and Storage (CCS). This is just ten percent less than the potential without forest protection. Thus, about one fifth of the estimated global energy demand by the end of the century could be satisfied. In the year 2055 things look different. At this point in time, forest protection still shows the effect of considerably reducing the economic potential of bioenergy: from 100 to 70 exajoules, or 30 percent less. However, with respect to the importance of CCS for the contribution of bioenergy to climate change mitigation one needs to consider that the availability of this technology is still uncertain.
When forests get excluded from conversion to cropland for energy plants this increases competition for arable land between bioenergy and food production. This is the case even if – as done in the study presented – instead of edible crops such as corn and sugar cane, rather species like poplar and Miscanthus grass are planned for energy production. This leads to an increase of food production costs. “If one wants to achieve high potentials of bioenergy under the constraint of forest protection, much more investment has to be made in increasing agricultural productivity”, Popp says. “Also, we need to find new ways of really transfering technological change for instance to peasants in developing countries.”
If the goal is to prevent dangerous climate change, this can hardly be reached without expanding the use of energy from biomass, says Ottmar Edenhofer, co-author of the study and chief economist of PIK. “Without biomass plus carbon capture and storage – the sequestration of CO2 when those plants are used to fire power stations – climate protection might get quite expensive, as many studies show.” On the other hand, it becomes clear how inappropriate some one-sided praise of bioenergy is. “This kind of energy also comes at a price”, Edenhofer says. “Policies therefore shouldn’t just aim at the bioenergy but also integrate issues of land-use change and global food security.”
Article: Popp, A., Dietrich, J.P., Lotze-Campen H., Klein, D., Bauer, N., Krause, M., Beringer, T., Gerten, D., Edenhofer, O. (2011): The economic potential of bioenergy for climate change mitigation with special attention given to implications for the land system. Environmental Research Letters [doi:10.1088/1748-9326/6/3/034017]