Time-Dependent Climate Impact and Energy Efficiency of Internationally Traded Non-torrefied and Torrefied Wood Pellets from Logging Residues

Charlotta Porsö,Per-Anders Hansson,Daniel Nilsson,Torun Hammar

doi:10.1007/s12155-017-9884-x

Charlotta Porsö, Per-Anders Hansson + Show 2 more

Open Access

https://doi.org/10.1007/s12155-017-9884-x

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Journal: Bioenergy research	Publication Date: Nov 24, 2017
Citations: 14	License type: open-access

Affiliation: Swedish University of Agricultural Sciences

Abstract

Demand for wood pellets as a renewable alternative to fossil fuels has increased in the past decade. However, production and use of wood pellets involves several operations (biomass extraction, chipping, transport, drying, milling, pelleting, combustion) with negative impacts on e.g. the climate. In this study, the energy efficiency and climate impact of production and use of non-torrefied and torrefied wood pellets were analysed and compared. The wood pellets, produced from logging residues extracted from a boreal coniferous forest stand (Norway spruce (Picea abies (L.) H. Karst)) in northern Sweden, were assumed to be exported and finally used in a power plant. Time-dependent life cycle assessment, expressing the climate impact as global temperature change over time, was used to include annual greenhouse gas fluxes of both fossil and biogenic origin. The results showed that carbon stock changes due to extraction of logging residues contributed most of the warming effect on global temperature. Due to greater demand for raw material, a higher warming impact per gigajoule fuel was obtained for torrefied wood pellets than for non-torrefied wood pellets. However, torrefied wood pellets demonstrated a lower climate impact (per GJ electricity) when advantages such as higher electrical energy efficiency and higher co-firing rate were included. A general conclusion from this study is that replacing coal with non-torrefied or torrefied wood pellets made from logging residues can mitigate climate change. The energy output of these systems was about sevenfold the primary energy input.

Highlights

With climate change recognised as a global threat, reductions in emissions of anthropogenic greenhouse gases (GHGs) are crucial [1]
Replacing fossil fuels with biomass is considered a viable approach, and this has increased the demand for biomass for energy conversion [2]
The wood pellets, produced from logging residues extracted from a boreal coniferous forest stand (Norway spruce (Picea abies (L.) H

Summary

Introduction

With climate change recognised as a global threat, reductions in emissions of anthropogenic greenhouse gases (GHGs) are crucial [1]. Replacing fossil fuels with biomass is considered a viable approach, and this has increased the demand for biomass for energy conversion [2]. The global wood pellet market has grown sharply in recent decades and further growth is expected. America and Russia to Europe, which is currently the main market for wood pellets. This is partly a consequence of the European Union’s target to reduce GHG emissions and increase the share of renewable energy sources [3]. Using wood pellets for electricity production in new dedicated bioenergy plants or for co-firing in existing fossil fuel-fired plants has been shown to be a relatively economically and technically straightforward solution to mitigate GHG emissions [2, 4, 5]

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