Including albedo in time‐dependent LCA of bioenergy. Issue 6 (19th April 2020)

• Record Type: Journal Article
• Authors: Sieber, Petra; Ericsson, Niclas; Hammar, Torun; Hansson, Per‐Anders
• Is Part Of: Global change biology. Volume 12:Issue 6(2020)
• Page Start: 410
• Page End: 425
• Publication Date: 2020-04-19
• Subjects: albedo -- bioenergy -- climate impact -- greenhouse gases -- land use change -- LCA -- life cycle assessment -- willow; Biomass energy -- Periodicals; Biomass energy -- Environmental aspects -- Periodicals; Energy crops -- Periodicals; 662.88
• DOI: 10.1111/gcbb.12682
• Languages: English
• ISSNs: 1757-1693

Abstract

Abstract: Albedo change during feedstock production can substantially alter the life cycle climate impact of bioenergy. Life cycle assessment (LCA) studies have compared the effects of albedo and greenhouse gases (GHGs) based on global warming potential (GWP). However, using GWP leads to unequal weighting of climate forcers that act on different timescales. In this study, albedo was included in the time‐dependent LCA, which accounts for the timing of emissions and their impacts. We employed field‐measured albedo and life cycle emissions data along with time‐dependent models of radiative transfer, biogenic carbon fluxes and nitrous oxide emissions from soil. Climate impacts were expressed as global mean surface temperature change over time (∆ T ) and as GWP. The bioenergy system analysed was heat and power production from short‐rotation willow grown on former fallow land in Sweden. We found a net cooling effect in terms of ∆ T per hectare (−3.8 × 10 –11 K in year 100) and GWP100 per MJ fuel (−12.2 g CO2 e), as a result of soil carbon sequestration via high inputs of carbon from willow roots and litter. Albedo was higher under willow than fallow, contributing to the cooling effect and accounting for 34% of GWP100, 36% of ∆ T in year 50 and 6% of ∆ T in year 100. Albedo dominated the short‐term temperature response (10–20 years) but became, in relative terms, less important over time, owing to accumulation of soil carbon under sustained production and the longer perturbation lifetime of GHGs. The timing of impacts was explicit with ∆ T, which improves the relevance of LCA results to climate targets. Our method can be used to quantify the first‐order radiative effect of albedo change on the global climate and relate it to the climate impact of GHG emissions in LCA of bioenergy, alternative energy sources or land uses. Abstract : Albedo change can substantially affect the life cycle climate impact of bioenergy. In this study, albedo was included in time‐dependent life cycle assessment, which accounts for the timing of emissions and their impacts. We used field‐measured albedo together with life cycle greenhouse gas (GHG) data to model the climate impact of short‐rotation willow bioenergy over time. We found a net cooling effect due to soil carbon sequestration and increased albedo relative to former fallow land. Albedo dominated the short‐term temperature response but under sustained production it became less important over time relative to GHGs.