Life cycle assessment of mountain forest wood fuel supply chains : case studies from Norway and Italy

Abstract

Concerns about the fast growth in greenhouse gas emissions have encouraged several countries to increase their use of renewable energy. According to the EU’s Renewable Energy Directive (RED), 20% of all the energy production in the EU should come from renewable energy sources by 2020. Woody biomass can be one choice within bioenergy for mitigating climate change if replacing fossil fuels. However, the demand for wood fuels has increased recently, and in Europe, the demand is predicted to exceed European supply, so we therefore need to consider more wood energy sources. Here, wood fuels from mountain forests can be an interesting alternative. Globally, mountain forests cover 28% of the total forested areas, while in Europe one quarter of the forest is located in mountain areas. Thus, there is a large potential for harvesting woody biomass for bioenergy use. The aim of this PhD study is to assess the GHG emissions associated with two wood fuel supply chains from mountain forests. Two case studies, one in Norway (Hedmark-Oppland counties) and one in Italy (Valle di Fiemme -Trentino-Alto Adige region) are analyzed and compared. The methodology used is the Life Cycle Assessment, which is an established tool for assessing the mentioned environmental impact for the supply system through its life cycle – from the forest stand to the user (bioenergy plant), through forest management, logging operations, transportation and combustion at the plant. The chosen functional unit is one solid cubic meter over bark (1 m3 s.o.b.). The environmental impact category under assessment was climate change, expressed as global warming potential (GWP) with a time horizon of 100 years in terms of the amount of GHG emissions. In the study, a cost analysis (NOK or euro/m3 s.o.b.) is performed, and an analysis of the employment impacts (hours/m3 s.o.b.) is conducted in the Italian case related to the examined supply chains. Comparison with lowland forest or other types of renewable energy is outside the scope of this study. The PhD thesis consists of four papers. Papers 1 and 2 deal with the Norwegian case study, while Paper 3 describes the Italian case study. Paper 4 compares the main findings of each case study, analysing the differences and similarities between the Norwegian and Italian supply chains. Paper 1 provides the first part of the Norwegian case study, comprising the production stages from the mountain forest stands to the terminal. Mountain forests were highlands located in flat terrain. Forest management, logging operations and transportation to the terminal were the processes assessed. Forest residues, generally left at the forest stand, were harvested and bundled. Fuel consumption, raw material and primary energy use were calculated as input parameters. Results showed that the operation with the highest emissions and costs was transportation of woody biomass to the terminal, due to high fuel consumption and long transportation distance. Forest management had the lowest emissions, but highest costs. Bundling had high emissions and costs, even if long transport distance might make this operation advantageous in mountain areas. The present forest management and transport logistics are elements, which can be improved, seen from a GHG perspective. In Paper 2, the second part of the Norwegian supply chain is assessed; i.e. from the terminal to the biomass combustion plant. The benefits of replacing fossil fuel (natural gas, coal and oil) with wood fuel from the mountain sites, as described in paper 1, were calculated based on the assumption of carbon neutrality. Two alternatives were analyzed: i) a local supply chain, where raw materials from lowland forests were chipped at the terminal and transported by truck to a local district heating plant, and ii) an international supply chain, where raw materials from both lowland and highland forests were chipped at the terminal and exported by train to a combined heat and power plant in Sweden. The local supply chain had larger emissions than the export alternative. Both railway transportation and energy cogeneration made the international supply chain more efficient than the local alternative. The wood chips from mountain forests in Norway can be an option for covering the increasing demand for wood fuels in Sweden. Furthermore, the results indicate that the export of wood chips from Norway to Sweden is currently economically viable. Paper 3 presents the Italian case study carried out in Valle di Fiemme-Trentino region. In this paper, the social aspect (i.e. the direct employment potential) was assessed in addition to the environmental and economic aspects. The LCA concerned a local supply chain from mountain forest stands located in steep terrains to combustion at a district heating plant, where wood fuels were assumed to replace a fossil fuel plant (natural gas or oil plant). Logging residues, generally left at the forest stand, were harvested and chipped at the landing site. Chipping was the operation with the largest emissions followed by transportation by truck. Extraction by cable yarder was the operation with the highest costs along the supply chain. Regarding the analysis of employment, transportation and yarding operation created working opportunities. The use of woody biomass for energy can generate new jobs, although the topic of job creation is under discussion in the forestry sector. Furthermore, comparisons between an innovative (more mechanized) and a traditional logging system (more manual work) were presented, indicating that the substitution of a motor manual with a mechanized logging system reduced both emissions and costs. Paper 4 compares results from the Norwegian case study (paper 1 and 2) and the Italian case study (paper 3). Distinctive features of each case study, both similarities and differences, are discussed. The main results from the Norwegian case study were: a high rate of mechanization in harvesting highland forests located in flat terrain, chipping at the terminal, and a preference for an international supply chain (i.e. export to Sweden). The main features of the Italian supply chain were: a predominance of motor manual operations, felling trees in steep terrain, chipping at the landing of logging residues, absence of a terminal, and a local supply chain. The overall comparison between the case studies showed larger emissions for the Norwegian supply chain than the Italian one, due to higher mechanization and more steps involved in the supply chain. That also explained the higher costs for the Norwegian case. However, the greenhouse gas balance for the studied supply chains was still positive when wood fuels substituted fossil fuels. The analysis of employment was a critical aspect, and needs further investigation. The papers show large differences in how wood fuel supply chains are handled in the studied mountainous areas, making it difficult to formulate general conclusions. However, our case studies clearly show the potential for using woody biomass for bioenergy from mountain forests and the feasibility of harvesting wood fuels there with positive GHG impacts and without increasing the operative costs dramatically. The improvement of critical aspects of the supply chain operations may reduce emissions and costs. The evaluation of other impacts, in particular biodiversity aspects and deeper analyses should be made to ensure the fulfilment of sustainability criteria.

Bekymringer vedrørende den store økningen i klimagassutslipp har ført til en sterk interesse i bruk av fornybar energi, herunder bioenergi. Bioenergi fra skog har store muligheter til å redusere klimagassutslippene når fossil energi erstattes. Den økte etterspørselen etter bioenergi fra skog har gjort at flere land har begynt å se etter alternative kilder for slik energi. Bioenergi fra fjellskog har vist seg å være en interessant mulighet. Målet med denne doktorgraden er å vurdere klimagassutslippene fra to tilbudskjeder for bioenergi fra fjellskog. To casestudier, en i Norge (Hedmark og Oppland fylker) og en i Italia (Valle di Fiemme - Trentino-Alto Adige-regionen) er analysert og sammenlignet. Livsløpsanalyse, en etablert metode for å studere miljøpåvirkninger av et produkt gjennom dets livsløp – i dette tilfellet bioenergi fra bestandet til bruker (bioenergianlegg) – er benyttet. Den funksjonelle enheten er en fastkubikkmeter over bark. Studien inneholder også kostnadsanalyser, og den italienske studien også en sysselsettingsanalyse. Avhandlingen inneholder fire artikler. Artikkel 1 og 2 analyser den norske tilbudskjeden, mens den italienske studien er presentert i Artikkel 3. Artikkel 4 fremstiller hovedresultatene fra hver studie og sammenligner resultatene og konklusjonene for å belyse forskjeller og likheter mellom den norske og den italienske tilbudskjeden. Den norske tilbudskjeden i studien kjennetegnes av en høy mekaniseringsgrad i avvirkningen, lokalisering av tømmeravvirkning i relativt flatt terreng, flising ved terminal og at den er internasjonal (eksport til Sverige). Den italienske tilbudskjeden karakteriseres av en overveiende bruk av motormanuelle drifter, avvirkning i bratt terreng, flising ved landing av hogstavfall, ingen terminal og lokal bruker. Den overordnete sammenligningen av studiene viser at den norske tilbudskjeden har en høyere mekaniseringsgrad og inkluderer flere driftsledd enn den italienske, noe som kan forklare de høyere klimagassutslippene i den norske kjeden. Reduksjonene i klimagassutslipp i energianlegget, altså unngåtte klimagassutslipp ved erstatning av fossile brennstoff med bioenergi fra fjellskog, var signifikante i begge tilfeller. Imidlertid bør man være forsiktig med å generalisere resultatene til andre fjellskogsområder. Videre foreslår vi at før økt avvirkning i de to områdene anbefales, inkluderes andre bærekraftskriterier i analysene.