Abstract

A life cycle assessment of a Swedish short-rotation coppice willow bioenergy system generating electricity and heat was performed to investigate how the energy efficiency and time-dependent climate impact were affected when the feedstock was converted into bio-oil and char before generating electricity and heat, compared with being combusted directly. The study also investigated how the climate impact was affected when part of the char was applied to soil as biochar to act as a carbon sequestration agent and potential soil improver. The energy efficiencies were calculated separately for electricity and heat as the energy ratios between the amount of energy service delivered by the system compared to the amount of external energy inputs used in each scenario after having allocated the primary energy related to the inputs between the two energy services. The energy in the feedstock was not included in the external energy inputs. Direct combustion had the highest energy efficiency. It had energy ratios of 10 and 36 for electricity and heat, respectively. The least energy-efficient scenario was the pyrolysis scenario where biochar was applied to soils. It had energy ratios of 4 and 12 for electricity and heat, respectively. The results showed that pyrolysis with carbon sequestration might be an option to counteract the current trend in global warming. The pyrolysis system with soil application of the biochar removed the largest amount of CO2 from the atmosphere. However, compared with the direct combustion scenario, the climate change mitigation potential depended on the energy system to which the bioenergy system delivered its energy services. A system expansion showed that direct combustion had the highest climate change mitigation potential when coal or natural gas were used as external energy sources to compensate for the lower energy efficiency of the pyrolysis scenario.

Keywords

biochar; climate impact metrics; land use change; LCA; pyrolysis; Salix; soil organic carbon; SRC; willow

Published in

GCB Bioenergy
2017, Volume: 9, number: 5, pages: 876-890
Publisher: WILEY

SLU Authors

• Ericsson, Niclas

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

• Nordberg, Åke

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

• Sundberg, Cecilia

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    
  • Royal Institute of Technology (KTH)

• Ahlgren, Serina

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

• Hansson, Per-Anders

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Ensure access to affordable, reliable, sustainable and modern energy for all
Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss
Take urgent action to combat climate change and its impacts


UKÄ Subject classification

Energy Systems


Publication identifier

DOI: https://doi.org/10.1111/gcbb.12415

Permanent link to this page (URI)

https://res.slu.se/id/publ/86839