The impacts of land-use change from grassland to bioenergy Short Rotation Coppice (SRC) willow on the crop and ecosystem greenhouse gas balance

Abstract:

The aim of this research is to better understand the greenhouse gas balance of land-use transition to bioenergy cropping systems in a UK context. Given limited land availability, addressing the food-energy-water nexus remains a challenge, and it is imperative that bioenergy crops are sited appropriately and that competition with food crops is minimised.

Initial analyses included an extensive literature review and meta-analysis with a focus on the effects of land-use change to bioenergy on soil carbon and GHGs. This data mining exercise allowed us to understand the current state of the literature and identify key areas of research which needed to be addressed. Significant knowledge gaps were identified, with particular uncertainty around transitions from grasslands and transitions to short rotation forestry.

A paired site experiment was established on a commercial SRC willow plantation and grassland to measure soil and ecosystem respiration. Initial results indicate that willow was a net sink for CO₂ in comparison to grassland which was a net source of CO₂. This provides evidence that the GHG balance of transition to SRC bioenergy willow will potentially result in increased soil carbon, in the long-term. The empirical findings from this study have been combined with modelled estimates for the site to both test and validate the ECOSSE model. Initial comparisons show that the model is able to accurately predict the respiration occurring at the field site, suggesting that it is a valuable approach for up-scaling from point sites such as this to wider geographical areas, and for considering future climate scenarios. The spatial modelling outputs will be used to build a modelling tool for non-specialist users which will determine the GHG and soil carbon effects of changing land to bioenergy for UK.

This work is based on the Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project, which was commissioned and funded by the Energy Technologies Institute (ETI).