PhD defence: Anders Tærø Nielsen

Anders Tærø Nielsen defends his thesis,

Forest biomass for climate change mitigation

Supervisors:
Professor Karsten Raulund-Rasmussen, IGN
Associate Professor Inge Stupak, IGN
Michael Glud and Lisbeth Sevel, HedeDanmark

Assessment Committee:
Professor Jürgen Bauhus, University of Freiburg - Germany
Professor C.T. (Tat) Smith, University of Toronto - Canada
Professor Lars Vesterdal (chairman), IGN

Summary:
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 thesis is available from the PhD Administration office, 04.1.417