In order to strategically implement climate mitigation projects, policymakers require an accurate accounting of the climate impacts from both biogeochemical and biogeophysical climate forcings. The inclusion of land-use driven biogeophysical effects – specifically albedo – and the incorporation of time-integrated carbon sequestration are often neglected in carbon accounting that considers both life-cycle analyses and averted emissions. We assessed the net impact of three forestry and two short-rotation coppiced willow scenarios on climate forcing in New York State. We estimated the effect of each land use change strategy by calculating emissions from four components: 1) the contribution to short and long-term carbon sequestration, 2) emissions generated by the complete life cycle of biomass production, 3) emissions offset by generating energy through biofuels as a replacement for the standard fuel mix, and finally 4) the impact of land use change on albedo. For each land-use scenario we used a maize agricultural field as the baseline. We calculated emissions from a mixed hardwood forest based on three harvest scenarios and from willow biofuel plantations for two productivity scenarios.
Results/Conclusions
We found that willow bioenergy provided the greatest cooling impact (-447 to -796 Mg CO2-equiv ha-1), but that this effect was based substantially by the assumed default mix of power-generation options. Our scenario found afforestation of agricultural land had the potential to result in a net cooling impact (-156 Mg CO2-equiv ha-1), but that forest harvest reduced or even reversed this effect depending on harvest intensity. Albedo offset 63 to 79% of greenhouse gas driven emissions in the forest scenarios, and 6 to 11% in the willow biomass scenarios. Inclusion of land-use driven biogeophysical effects is essential to calculating the net climatic impact of mitigation projects. We identified conditions under which these projects might be net carbon sinks and sources and determined that quantifying albedo as a carbon-equivalent forcing would be integral to any policy decision. Overall, we determined that willow bioenergy provided the greatest cooling impact, but that this was controlled substantially by the background fuel mix. Afforestation had a net cooling impact, but was substantially reduced by the effect of albedo.