Environmental performance of gasified willow from different lands including land‐use changes

Koldo Saez De Bikuña,Michael Zwicky Hauschild,Andreas Ibrom,Kim Pilegaard

doi:10.1111/gcbb.12378

Abstract

AbstractA life‐cycle assessment (LCA) of a low‐input, short rotation coppice (SRC) willow grown on different Danish lands was performed. Woodchips are gasified, producer gas is used for cogeneration of heat and power (CHP), and the ash–char output is applied as soil amendment in the field. A hybrid model was developed for the estimation of greenhouse gas (GHG) emissions from indirect land‐use changes (iLUC) induced by willow cropping on arable land (iLUCfood). For this, area expansion results from a general equilibrium economic model were combined with global LUC trends to differentiate between land transformation (as additional agricultural expansion, in areas with historical deforestation) and occupation (as delayed relaxation, DR, in areas with historical land abandonment) impacts. A biophysical approach was followed to determine the iLUCfeed emissions factor from marginal grassland. Land transformation impacts were derived from latest world deforestation statistics, while a commercial feed mix of equivalent nutritive value was assumed to substitute the displaced grass as fodder. Intensification effects were included in both iLUC factors as additional N‐fertilizer consumption. Finally, DR impacts were considered for abandoned farmland, as a relative C stock loss compared to natural regeneration. ILUC results show that area related GHG emissions are dominant (93% of iLUCfood and 80% of iLUCfeed), transformation being more important (82% of iLUCfood) than occupation (11%) impacts. LCA results show that CHP from willow emits 4047 kg CO2‐eq (or 0.8 gCO2‐eq MJ−1) when grown on arable land, while sequestering 43 745 kg CO2‐eq (or −10.4 gCO2‐eq MJ−1) when planted on marginal pastureland, and 134 296 kg CO2‐eq (or −31.8 gCO2‐eq MJ−1) when marginal abandoned land is cultivated. Increasing the bioenergy potential without undesirable iLUC effects, especially relevant regarding biodiversity impacts, requires that part of the marginally used extensive grasslands are released from their current use or energy cropping on abandoned farmland incentivized.

Highlights

In the light of the Peak Oil and Global Climate Change, a gradual shift in the energy provision from fossil to renewable sources has ensued in many industrialized countries since the Kyoto Protocol (UNFCCC, 1998)
A hybrid model was developed for the estimation of greenhouse gas (GHG) emissions from indirect land-use changes induced by willow cropping on arable land
The suggestions for the reference land use and the modelling period (500 years) were not followed. This is because this study aims at integrating, rather than focusing exclusively on, land-use impacts in life-cycle assessment (LCA) of dedicated bioenergy systems

Summary

Introduction

In the light of the Peak Oil and Global Climate Change, a gradual shift in the energy provision from fossil to renewable sources has ensued in many industrialized countries since the Kyoto Protocol (UNFCCC, 1998). The crops that are displaced by bioenergy crops increase pressure on biodiversity wherever they are brought into production (Koh, 2007; Butchart et al, 2010; Dale et al, 2010). To avoid these problems, biological residues and biomass grown in marginal farmlands have been pointed as a solution to the food-energyenvironment trilemma (EEA, 2005; Tilman et al, 2009). Dedicated energy crops grown on marginal lands are expected to meet the major part of the increasing biomass demand in EU (4.5 EJ yrÀ1) by 2020 (Bentsen & Felby, 2012). If the target marginal land is abandoned a spontaneous, site-dependent, natural regeneration process ought to be considered (Mila i Canals et al, 2007a,b; Koellner et al, 2013)

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Conclusion