Abstract
Awareness of elevated CO2 levels in the atmosphere and resulting climate change has increased focus on renewable energy sources during recent decades. Biomass for energy has been predicted to have the greatest potential for CO2 reductions in the short term and the IPCC assumes that the use of biomass for energy is CO2 neutral. Several studies have however criticized this CO2 neutrality assumption and questioned whether CO2 reductions actually are achieved through use of biomass for energy.
The purpose of this thesis is to investigate the biomass production potential of poplar plantations on southern Scandinavian sites, managed under different systems both in agriculture and in forests. In addition, the objective is to assess the potential of the poplar plantations to mitigate climate change by using poplar biomass for substitution of fossil fuels in comparison to a traditional product orientated beech forest strategy and an unmanaged forest strategy.
The studies of the growth potential of poplar showed that, with the right clone selection, stock density, and application of appropriate establishment methods, poplar could produce up to 14 Mg of dry matter ha-1 yr-1 on the best sites. The production results were, however, heavily site dependent, with soil texture and C/N ratio of the soils being the best site productivity indicators for poplar.
The comparison of three forest management strategies, poplar, beech or unmanaged beech, showed that the poplar for bioenergy management strategy resulted in the largest CO2 emission reductions, but the results were heavily dependent on the maintenance of high growth rate for poplar and on which types of fuels substituted by biomass. In cases where lower productivity for the poplar was applied, the product-oriented beech forest strategy was more favorable for reduction of CO2 emissions. In all analyzed scenarios, however, the managed poplar and beech forest strategies resulted in lower CO2 emissions than the unmanaged forest.
The studies also showed that it cannot readily be assumed that the use of biomass is entirely CO2 neutral, due to use of fossil fuels in silviculture, harvest, transport etc., and due to the fact that most managed forests have a lower carbon stock than unmanaged forests.
The purpose of this thesis is to investigate the biomass production potential of poplar plantations on southern Scandinavian sites, managed under different systems both in agriculture and in forests. In addition, the objective is to assess the potential of the poplar plantations to mitigate climate change by using poplar biomass for substitution of fossil fuels in comparison to a traditional product orientated beech forest strategy and an unmanaged forest strategy.
The studies of the growth potential of poplar showed that, with the right clone selection, stock density, and application of appropriate establishment methods, poplar could produce up to 14 Mg of dry matter ha-1 yr-1 on the best sites. The production results were, however, heavily site dependent, with soil texture and C/N ratio of the soils being the best site productivity indicators for poplar.
The comparison of three forest management strategies, poplar, beech or unmanaged beech, showed that the poplar for bioenergy management strategy resulted in the largest CO2 emission reductions, but the results were heavily dependent on the maintenance of high growth rate for poplar and on which types of fuels substituted by biomass. In cases where lower productivity for the poplar was applied, the product-oriented beech forest strategy was more favorable for reduction of CO2 emissions. In all analyzed scenarios, however, the managed poplar and beech forest strategies resulted in lower CO2 emissions than the unmanaged forest.
The studies also showed that it cannot readily be assumed that the use of biomass is entirely CO2 neutral, due to use of fossil fuels in silviculture, harvest, transport etc., and due to the fact that most managed forests have a lower carbon stock than unmanaged forests.
| Original language | English |
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| Publisher | Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen |
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| Number of pages | 182 |
| Publication status | Published - 2016 |
