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Climate impact of the sustainable use of forest biomass in energy and material system: a life cycle perspective
Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human society releases greenhouse gas emissions to the atmosphere while providing housing, heat, mobility and industrial production. Man-made greenhouse gas emissions are the main causes of climate change, coming mainly from burning fossil fuels and land-use changes. Sustainably managed forests play an important role in climate change mitigation with the prospect of sustainably providing essential materials and services as part of a low-carbon economy, both through the substitution of fossil-intensive fuels and material and through their potential to capture and store carbon in the long-term perspective.

The overall aim of this thesis was to develop a methodology under a life cycle perspective to assess the climate impact of the sustainable use of forest biomass in bioenergy and material systems. To perform this kind of analysis a methodological framework is needed to accurately compare the different biological and technological systems with the aim to minimize the net carbon dioxide emissions to the atmosphere and hence the climate impact. In such a comparison, the complete energy supply chains from natural resources to energy end-use services has to be considered and are defined as the system boundaries.

The results show that increasing biomass production through more intensive forest management or the usage of more productive tree species combined with substitution of non-wood products and fuels can significantly reduce global warming. The biggest single factor causing radiative forcing reduction was using timber to produce wood material to replace energy-intensive construction materials such as concrete and steel. Another very significant factor was replacing fossil fuels with forest residues from forest thinning, harvest, wood processing, and post-use wood products. The fossil fuel that was replaced by forest biomass affected the reductions in greenhouse gas emissions, with carbon-intensive coal being most beneficial to replace. Over the long term, an active and sustainable management of forests, including their use as a source for wood products and bioenergy allows the greatest potential for reducing greenhouse gas emissions.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2018.
Series
Linnaeus University Dissertations ; 306/2018
Keywords [en]
forest residues, fossil fuel substitution, forest management, radiative forcing, land use change, climate change, bioenergy
National Category
Energy Systems Civil Engineering
Research subject
Technology (byts ev till Engineering), Bioenergy Technology; Technology (byts ev till Engineering), Civil engineering
Identifiers
URN: urn:nbn:se:lnu:diva-69561ISBN: 978-91-88761-11-8 (print)ISBN: 978-91-88761-12-5 (electronic)OAI: oai:DiVA.org:lnu-69561DiVA, id: diva2:1170666
Public defence
2018-01-18, 10:00 (English)
Opponent
Supervisors
Available from: 2018-01-05 Created: 2018-01-04 Last updated: 2018-05-17Bibliographically approved
List of papers
1. Climate mitigation comparison of woody biomass systems with the inclusion of land-use in the reference fossil system
Open this publication in new window or tab >>Climate mitigation comparison of woody biomass systems with the inclusion of land-use in the reference fossil system
2014 (English)In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 65, p. 136-144Article in journal (Refereed) Published
Abstract [en]

While issues of land-use have been considered in many direct analyses of biomass systems, little attention has heretofore been paid to land-use in reference fossil systems. Here we address this limitation by comparing forest biomass systems to reference fossil systems with explicit consideration of land-use in both systems. We estimate and compare the time profiles of greenhouse gas (GHG) emission and cumulative radiative forcing (CRF) of woody biomass systems and reference fossil systems. A life cycle perspective is used that includes all significant elements of both systems, including GHG emissions along the full material and energy chains. We consider the growth dynamics of forests under different management regimes, as well as energy and material substitution effects of harvested biomass. We determine the annual net emissions of CO2, N2O and CH4 for each system over a 240-year period, and then calculate time profiles of cRF as a proxy measurement of climate change impact. The results show greatest potential for climate change mitigation when intensive forest management is applied in the woody biomass system. This methodological framework provides a tool to help determine optimal strategies for managing forests so as to minimize climate change impacts. The inclusion of land-use in the reference system improves the accuracy of quantitative projections of climate benefits of biomass-based systems. (c) 2014 Elsevier Ltd. All rights reserved.

Keywords
Life cycle assessment, Greenhouse gases, Cumulative radiative forcing, Land-use, Time dynamics, Woody bioenergy
National Category
Energy Systems
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-36191 (URN)10.1016/j.biombioe.2014.04.012 (DOI)000337854900015 ()2-s2.0-84901255653 (Scopus ID)
Available from: 2014-07-24 Created: 2014-07-24 Last updated: 2018-01-04Bibliographically approved
2. Climate effects of bioenergy from forest residues in comparison to fossil energy
Open this publication in new window or tab >>Climate effects of bioenergy from forest residues in comparison to fossil energy
Show others...
2015 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 138, p. 36-50Article in journal (Refereed) Published
Abstract [en]

Forest residues can be left at the harvest site to gradually decompose, or can be collected for energy purposes. This study analyzes the primary energy and climate impacts of bioenergy systems where forest residues are collected and used for electricity, heat and transportation, compared to fossil-based energy systems where fossil fuels provide the same services while forest residues are left on site to decompose. Time profiles are elaborated of primary energy use and carbon dioxide emissions from various energy applications fulfilled by bioenergy or fossil energy systems. Different biological decay functions are considered based on process-based modeling and inventory data across various climate zones. For all scenarios, the changes in cumulative radiative forcing (CRF) are calculated over a 300-year period, to evaluate the short- and long-term contributions of forest residue to climate change mitigation. A life cycle perspective along the full energy chains is used to evaluate the overall effectiveness of each system. The results show largest primary energy and climate benefits when forest residues are collected and used efficiently for energy services. Using biomass to substitute fossil coal provides greater climate change mitigation benefits than substituting oil or fossil gas. Some bioenergy substitutions result in positive CRF, i.e. increased global warming, during an initial period. This occurs for relatively inefficient bioenergy conversion pathways to substitute less carbon intensive fossil fuels, e.g. biomotor fuel used to replace diesel. More beneficial bioenergy substitutions, such as efficiently replacing coal, result immediately in reduced CRF. Biomass decay rates and transportation distance have less influence on climate benefits.

Keywords
forest residues, primary energy, carbon dioxide, radiative forcing, fuel substitution
National Category
Other Environmental Biotechnology
Research subject
Technology (byts ev till Engineering), Bioenergy Technology
Identifiers
urn:nbn:se:lnu:diva-37493 (URN)10.1016/j.apenergy.2014.10.013 (DOI)000347582700005 ()2-s2.0-84909957910 (Scopus ID)
Note

Correction published in: Applied Energy, 2016, vol. 170, pp. 490-493.DOI: 10.1016/j.apenergy.2016.02.087

Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2018-08-30Bibliographically approved
3. Climate change effects of forestry and substitution of carbon-intensive materials and fossil fuels
Open this publication in new window or tab >>Climate change effects of forestry and substitution of carbon-intensive materials and fossil fuels
Show others...
2017 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 67, p. 612-624Article in journal (Refereed) Published
Abstract [en]

We estimate the climate effects of directing forest management in Sweden towards increased carbon storage in forests with more land set-aside for protection, or towards increased forest production for the substitution of carbon-intensive materials and fossil fuels, relative to a reference case of current forest management. We develop various scenarios of forest management and biomass use to estimate the carbon balances of the forest systems, including ecological and technological components, and their impacts on the climate in terms of radiative forcing. The scenario with increased set-aside area and the current level of forest residue harvest resulted in lower cumulative carbon emissions compared to the reference case for the first 90 years, but then showed higher emissions as reduced forest harvest led to higher carbon emissions from energy and material systems. For the reference case of current forest management, increased harvest of forest residues gave increased climate benefits. The most climatically beneficial alternative, expressed as reduced cumulative radiative forcing, in both the short and long terms is a strategy aimed at high forest production, high residue recovery rate, and high efficiency utilization of harvested biomass. Active forest management with high harvest levels and efficient forest product utilization will provide more climate benefit, compared to reducing harvest and storing more carbon in the forest.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Biomass residues ; Forest management ; Climate change ; Radiative forcing
National Category
Forest Science
Research subject
Technology (byts ev till Engineering)
Identifiers
urn:nbn:se:lnu:diva-57660 (URN)10.1016/j.rser.2016.09.056 (DOI)000389088900046 ()
Available from: 2016-10-28 Created: 2016-10-28 Last updated: 2018-01-04Bibliographically approved

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Citation style
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