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Climate impacts of woody biomass use for heat and power production in Sweden

Hammar, Torun (2017). Climate impacts of woody biomass use for heat and power production in Sweden. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2017:49
ISBN 978-91-576-8871-2
eISBN 978-91-576-8872-9
[Doctoral thesis]

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Abstract

Global warming is a result of human-induced greenhouse gas emissions, primarily from fossil fuel use, but also from land use changes. To mitigate climate change, fossil fuel-based energy systems need to be replaced with alternative energy sources. Here bioenergy can play an important role, since this renewable fuel is considered to be carbon-neutral, meaning that no extra carbon dioxide (CO2) is emitted to the atmosphere.

However, carbon-neutral is not the same as climate-neutral and, while the CO2 from biomass use was once, and will again, be captured during plant growth, the temporary imbalance in the atmosphere can have consequences for the climate. Furthermore, bioenergy supply chains generally consume fossil fuels and producing biomass for energy requires land, which can lead to carbon stock changes.

This thesis examined the climate impact and energy performance of bioenergy from short-rotation coppice willow and long-rotation forest residues. Willow is a dedicated energy crop grown on agricultural land for energy, while forest residues (tops, branches and stumps) are a by-product harvested after final felling in conventional forests. A time-dependent life cycle assessment (LCA) method was used to capture the timing of greenhouse gas fluxes, including biogenic carbon (carbon stored in biomass and soil). In addition, a new method that combines time-dependent LCA with GIS mapping, and thus assesses the climate impact over a landscape, was developed.

The results showed that growing willow on former fallow land can give a negative climate impact (cooling effect) by sequestering carbon from the atmosphere in biomass and soil and by achieving high productivity, which is important for the final outcome. Initial soil organic carbon content was shown to have a large influence on future carbon stocks. Harvesting forest residues for energy gave a higher climate impact than harvesting willow, with forest stumps giving a slightly higher climate impact than tops and branches. Moreover, forest residues harvested in northern Sweden gave a slightly higher climate impact than forest residues harvested in the south. All bioenergy feedstocks studied gave a lower climate impact than hard coal and natural gas over time and the climate benefit of replacing these fossil fuels increased over time when studying continuous energy outtake (landscape perspective).

Authors/Creators:Hammar, Torun
Title:Climate impacts of woody biomass use for heat and power production in Sweden
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :May 2017
Depositing date:9 May 2017
Volume:2017:49
Number of Pages:87
Papers/manuscripts:
NumberReferences
IHammar, T., Ericsson, N., Sundberg, C. & Hansson, P.-A. (2014). Climate impact of willow grown for bioenergy in Sweden. BioEnergy Research 7(4), 1529-1540.
IIHammar, T., Ortiz, C., Stendahl, J., Ahlgren, S. & Hansson P.-A. (2015). Time-dynamic effects on global temperature when harvesting logging residues for bioenergy. BioEnergy Research 8(4), 1912-1924.
IIIOrtiz, C.A., Hammar, T., Ahlgren, S., Hansson, P.-A. & Stendahl, J. (2016). Time-dependent global warming impact of tree stump bioenergy in Sweden. Forest Ecology and Management 371, 5-14.
IVHammar, T., Hansson, P.-A. & Sundberg, C. (2017). Climate impact assessment of willow energy from a landscape perspective: a Swedish case study. GCB Bioenergy 9(5), 973-985.
Place of Publication:Uppsala
Publisher:Department of Energy and Technology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8871-2
ISBN for electronic version:978-91-576-8872-9
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P05 Energy resources management
P Natural resources > P40 Meteorology and climatology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Climate Research
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 207 Environmental Engineering > Energy Systems
Agrovoc terms:wood residues, wood energy, bioenergy, biofuels, salix, climate change mitigation, climate change, carbon, life cycle analysis, sweden
Keywords:bioenergy, LCA, willow, forest residues, temperature change, soil organic carbon, land use change, GIS
URN:NBN:urn:nbn:se:slu:epsilon-e-4161
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-4161
ID Code:14287
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Energy and Technology
External funders:Energimyndigheten and FORMAS
Deposited By: Torun Hammar
Deposited On:10 May 2017 13:55
Metadata Last Modified:05 Jul 2017 03:09

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