Climate impact and energy efficiency of woody bioenergy systems from a landscape perspective

Abstract

The climate impact of bioenergy is debated, especially due to potential land use change effects and biogenic carbon fluxes. This study assessed the climate impact and energy efficiency of conventional long-rotation forest residues (branches, tops and stumps) and short-rotation forestry (willow) from a landscape perspective. A time-dependent life cycle assessment method, which considers the timing of biogenic carbon fluxes and the impact on global temperature over time, was combined with GIS mapping to assess the impact for a specific Swedish region (Uppsala County), i.e. a 'real' landscape. The results showed that harvesting forest residues decreased the forest carbon stocks over the landscape, while growing willow on previous fallow land increased the total carbon stocks. On average, energy ratios of 49 MJ MJ(-1) for branches and tops, and 30 MJ MJ(-1) for stumps and willow was found. Harvesting forest residues from the studied landscape resulted in climate impacts of around 0.8.10(-15) K MJ(-1) heat for branches and tops, and 1.3.10(-15) K MJ(-1) heat for stumps. Willow energy gave the lowest climate impact of about -0.6,10(-15) K MJ(-1) heat. The landscape analysis showed that spatial variations in the region had an effect on energy efficiency and climate impact, but that this effect was relatively small. A more important factor was the time frame chosen for the analysis, especially for long-rotation forest systems. Methodological choices such as spatial scale (stand or landscape perspective), allocation method and functional unit also influenced the results.

Keywords

Global warming; Temperature change; Soil organic carbon; Salix; GIS; Forest residues; Stumps; Land use; Biogenic carbon; LCA

Published in

Biomass and Bioenergy
2019, volume: 120, pages: 189-199
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

SLU Authors

• Hammar, Torun

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

• Stendahl, Johan

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Sundberg, Cecilia

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

• Holmström, Hampus

  • Department of Forest Resource Management, Swedish University of Agricultural Sciences
    

• Hansson, Per-Anders

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

Global goals (SDG)

SDG7 Affordable and clean energy
SDG13 Climate action

UKÄ Subject classification

Forest Science

Publication identifier

• DOI: https://doi.org/10.1016/j.biombioe.2018.11.026

Permanent link to this page (URI)

https://res.slu.se/id/publ/97978