Energy use in Swedish forestry and its environmental impact

摘要

The commitments to sustainable development made by the member countries of the UN, together with the Kyoto Protocol, has raised the profile of issues related to the ecological evaluation of products, production processes and services. In each of the studies underlying this thesis a LCA (Life Cycle Assessment) perspective was adopted. Firstly, site-specific data were collected from three forest management regions in northern, central and southern Sweden in the late 1990s. Secondly, silvicultural and technological forestry developments between the early 1970s and late 1990s were evaluated by comparing the energy use in the forestry system at each of these times. Secondary transport of timber was found to be the most energy-demanding part of the forestry system usually, accounting for about 50 percent of the energy demands, and logging was generally the second most energy-demanding process (33-40 percent), except in systems involving mechanized logging operations in 1972, when logging required the most energy (60 percent). These findings show that increased mechanization since 1972 has not resulted in a rise in total energy use; in fact, it has led to more energy-efficient logging machines, from motor-manual and early mechanised systems, to current machines that are on the verge of automisation. In contrast, energy use in silviculture has increased, possibly due to the use of more supposedly advanced technology and more intensive silvicultural treatments. The same is also true for secondary haulage because of the greater use of road vehicles and longer haulage distances. An analyse of future possible secondary timber transport scenarios involving lorry or lorry-and-train combinations using a variety of potential fuels/energy carriers showed that in biobased-fuel cycles the greenhouse gas emissions are about 96 percent lower than in corresponding fossil fuel cycles. In addition, they involve little fossil energy. Given the expected future scarcity of fossil fuels, and potential consequences of global warming, it could be advantageous for the forest sector to both produce and use a renewable fuel, since it could increase the overall value of forest products and have a low environmental impact.