Abstract
AbstractLocally produced bioenergy can decrease the dependency on imported fossil fuels in a region, while also being valuable for climate change mitigation. Short‐rotation coppice willow is a potentially high‐yielding energy crop that can be grown to supply a local energy facility. This study assessed the energy performance and climate impacts when establishing willow on current fallow land in a Swedish region with the purpose of supplying a bio‐based combined heat and power plant. Time‐dependent life cycle assessment (LCA) was combined with geographic information system (GIS) mapping to include spatial variation in terms of transport distance, initial soil organic carbon content, soil texture and yield. Two climate metrics were used [global warming potential (GWP) and absolute global temperature change potential (AGTP)], and the energy performance was determined by calculating the energy ratio (energy produced per unit of energy used). The results showed that when current fallow land in a Swedish region was used for willow energy, an average energy ratio of 30 MJ MJ−1 (including heat, power and flue gas condensation) was obtained and on average 84.3 Mg carbon per ha was sequestered in the soil during a 100‐year time frame (compared with the reference land use). The processes contributing most to the energy use during one willow rotation were the production and application of fertilizers (~40%), followed by harvest (~35%) and transport (~20%). The temperature response after 100 years of willow cultivation was −6·10−16 K MJ−1 heat, which is much lower compared with fossil coal and natural gas (70·10−16 K MJ−1 heat and 35·10−16 K MJ−1 heat, respectively). The combined GIS and time‐dependent LCA approach developed here can be a useful tool in systematic analysis of bioenergy production systems and related land use effects.
Highlights
The high consumption of fossil fuels during the past century has generated large emissions of greenhouse gases (GHGs), which have contributed to global warming
In addition to climate change mitigation, bioenergy can play an important role in securing the energy supply in a region when locally produced biomass is utilized
See System description Only including fields located 0–60 km from the CHP plant Only including fields located 0–30 km from the CHP plant Yield decreased by 25% for all fields and years Yield increased by 25% for all fields and years Random yield for all fields, Æ20% with the same average as the base scenario (i.e. 20 Mg DM first harvest, 30 Mg DM subsequent harvest) The top 10% of fields giving the lowest climate impact Fields with initial SOC content
Summary
The high consumption of fossil fuels during the past century has generated large emissions of greenhouse gases (GHGs), which have contributed to global warming. One strategy to reduce GHG emissions and mitigate climate change is to move towards a more bio-based economy, by replacing fossil energy with bioenergy. In addition to climate change mitigation, bioenergy can play an important role in securing the energy supply in a region when locally produced biomass is utilized. One energy crop that has shown potential to generate bioenergy while increasing soil organic carbon (SOC) is short-rotation coppice willow (Rytter, 2012; Ericsson et al, 2013; Zetterberg & Chen, 2015). Growing willow on available agricultural land can be one strategy to provide a local community with a continuous supply of bioenergy. Climate impact assessments of willow are usually performed on stand level (e.g. Ericsson et al (2014); Hammar et al (2014); Porso€ & Hansson
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