Life cycle assessment of wood pellets and wood split logs for residential heating

Paula Quinteiro,Luís Tarelho,Pedro Marques,Mario Martín-Gamboa,Fausto Freire,Luís Arroja,Ana Cláudia Dias

doi:10.1016/j.scitotenv.2019.06.420

Paula Quinteiro, Luís Tarelho + Show 5 more

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https://doi.org/10.1016/j.scitotenv.2019.06.420

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Abstract

Wood-fuelled systems are commonly used all over the world for residential heating, and recently wood pellets have been replacing traditional firewood. This article presents an environmental life cycle assessment of five wood-based combustion systems for residential heating: i) a pellet stove using maritime pine pellets; a wood stove using ii) eucalyptus (Eucalyptus globulus Labill.) and iii) maritime pine (Pinus pinaster Ait.) split logs; and a fireplace using iv) eucalyptus and v) maritime pine split logs. The functional unit is 1 MJ of thermal energy for residential heating. System boundaries include four stages: (1) forest management; (2) pellet and wood split log production; (3) distribution; and (4) thermal energy generation. Environmental impacts were calculated for seven impact categories from the ReCiPe 2016 midpoint method, and a sensitivity analysis was performed using the Product Environmental Footprint (PEF) life cycle impact assessment method and modifying the distances travelled.Of the five heating systems analysed, the fireplace presents the worst performance for all the impact categories with the exception of freshwater eutrophication and marine eutrophication, when maritime pine split logs are burned in the fireplace. Comparing the pellet stove with the wood stove, neither system is better for all the impact categories analysed. Regarding sensitivity analysis, the use of an alternative characterisation method leads to similar trends in the results in comparison with those obtained from the ReCiPe method, while changes in transport distances do not affect the total impacts to a large extent.

Highlights

The use of woody biomass for energy purposes has been increasing in recent decades, highlighting the importance of woody resources in sustainable economies (Branck, 2017; IEA Bioenergy, 2002), due to the potential to reduce fossil fuel dependency and greenhouse gas (GHG) emissions
The objective of this study was to assess the environmental impacts of five different wood-based residential heating systems in Portugal: i) a pellet stove using maritime pine (Pinus pinaster Ait.) pellets as feedstock; a wood stove using ii) eucalyptus (Eucalyptus globulus Labill.) and iii) maritime pine split logs as feedstocks; and a fireplace using iv) eucalyptus and v) maritime pine split logs as feedstocks
Functional unit and system boundaries Five different wood-based residential heating systems were evaluated as follows: – PS-MP: thermal energy generation through combustion of maritime pine pellets in a pellet stove; – WS-E: thermal energy generation through combustion of eucalyptus split logs in a wood stove; – WS-MP: thermal energy generation through combustion of maritime pine split logs in a wood stove; – F-E: thermal energy generation through combustion of eucalyptus split logs in a fireplace; – F-MP: thermal energy generation through combustion of maritime pine split logs in a fireplace

Summary

Introduction

The use of woody biomass for energy purposes has been increasing in recent decades, highlighting the importance of woody resources in sustainable economies (Branck, 2017; IEA Bioenergy, 2002), due to the potential to reduce fossil fuel dependency and greenhouse gas (GHG) emissions. The use of woody fuels for residential heating leads to the emission of other air pollutants, namely carbon monoxide (CO), non-methane volatile organic compounds (NMVOC) and sulphur dioxide (SO2) (Cespi et al, 2014; Kocbach Bølling et al, 2009; Nyström et al, 2017; Solli et al, 2009) which should be taken into account in the environmental assessment of forest biomass for residential heating This can be accomplished by applying a life cycle assessment (LCA)-based methodology, which has been widely used to assess the environmental impacts of forest-based products Wood stoves and fireplaces are the most used wood-based appliances in Portugal (Gonçalves et al, 2012), and the use of wood pellet stoves has been largely increasing over the last few years (Vicente et al, 2016)

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