• Energy Research

Research into the methods of producing high quality wood chips for a rapidly growing energy sector is becoming increasingly important. For example, small wood chip heating plants require high quality wood chips to ensure efficient operation, thereby minimizing maintenance costs. Moisture content is considered to be an important quality parameter regarding wood based fuels. The objective of this study is to investigate methods to promote the natural drying of wood for bioenergy purposes. The effects on the drying process through covering the wood piles and partial debarking of stems were tested in order to identify methods to reduce the moisture content of the woody material in the storage. Drying trials were established in Finland, Italy and Scotland, utilizing tree species typically used for energy purposes in each area. The results show that natural drying is a viable and effective method to enhance the energy efficiency of wood based fuel products in all the regions studied. Furthermore, by adapting current harvesting methods and storage procedures even better results can be achieved. In addition, the results also indicate that broadleaved trees dry more effectively, if some partial debarking is carried out and that covering of piles is of utmost importance in Scotland and Finland.

Abstract Purpose of the Review This literature review focused on studies on alternative powertrains and fuels of non-road mobile machinery (NRMM) during the last 15 years and investigated their future potential and expectations. The goal was to evaluate different alternative powertrains based on previous research and highlight the possibilities and challenges of each technology. Additionally, the aim was to conduct a comprehensive overview about the technology development phase of alternative powertrains. Recent Findings This review covered a total of 115 studies consisting of hybrid, full-electric, biofuels, biogas, and hydrogen solutions. The results highlighted that hybrid and full-electric technologies have the greatest potential to replace conventional diesel engines in the future. The main challenges identified were battery reliability and high technology costs. Regarding biofuel, biogas, and hydrogen, the benefits were mainly lower emissions while the challenges were high costs and low production. Full-electric and hydrogen powertrains were found to reach zero local emissions during operations, while compared to diesel, repair and maintenance caused less emissions of 36–46% during the life cycle with full-electric and hydrogen solutions. With hybrid, biofuels, and biogas powertrains, the emission reduction potential ranged from 37 to 81% during operations and 36–66% during the entire life cycle. The highest Technology Readiness Levels (TRLs) were identified for hybrid and full-electric technologies in industrial machinery (6.9–7.4). The lowest measurable TRL (2.5) was with biogas powered construction machinery. The TRLs of biogas and hydrogen of forest machinery were excluded from this review due to the lack of research. Summary Alternative powertrains can eventually replace diesel engines, if the challenges with implementation, production, and reliability are solved. Furthermore, the benefits of electric and renewable technologies/fuels are unambiguous from the emission reduction and energy efficiency perspectives. Consequently, we recommend that future research focus especially on the implementation of alternative technologies as well as the improvement of the manufacturing infrastructure.

There is currently great general interest in reducing the use of fossil-based materials. Fossil-based tarps are still widely used as cover for wood chip storage piles, causing additional waste or requiring further waste treatment in the supply chain. This study aimed to investigate the performance of an innovative bio-based wood chip pile cover compared to conventional treatments (plastic-covered and uncovered) in eastern Finnish conditions. The experiment evaluated the drying process during the storage of stemwood chips during 5.9 months of storage. It included the developments of temperature, moisture content, heating value, energy content, basic density, particle size distribution, and the dry matter losses of a total of six piles. As a result, the forest stemwood chips dried by 11%, with dry-matter losses of 4.3%, when covered with the bio-pile cover. Using the plastic covering, the forest stemwood chips dried by 22%, with dry matter losses of 2.9%. At the end of the experiment, the energy content in plastic-covered piles was 6.1% higher than uncovered piles and 3.1% higher than bio-pile-covered piles. While differences in the key drying performance parameters can be observed, the differences between uncovered piles and those covered with plastic tarps, as well as between the bio-based and the uncovered piles, were not statistically significant. We conclude that the bio-based cover, under the studied conditions, do not render better storage conditions than in current practices. However, our study indicates possible fossil-substitutional benefits by using a bio-based cover, which calls for further R&D work in this matter.

Sustainably managed forests provide renewable raw material that can be used for primary/secondary conversion products and as biomass for energy generation. The potentially available amounts of timber, which are still lower than annual increments, have been published earlier. Access to this timber can be challenging for small-dimensioned assortments; however, technologically improved value chains can make them accessible while fulfilling economic and environment criteria. This paper evaluates the economic, environmental and social sustainability impacts of making the potentially available timber available with current and technologically improved value chains. This paper focuses on increasing the biomass feedstock supply for energy generation. Quantified impact assessments show which improvements - in terms of costs, employment, fuel and energy use, and reduced greenhouse gas emissions - can be expected if better mechanized machines are provided. Using three different methods - Sustainability Impacts Assessment (SIA), Life Cycle Assessment (LCA), and Emission Saving Criteria (ESC) - we calculated current and innovative machine solutions in terms of fuel use, energy use, and greenhouse gas emissions, to quantify the impact of the technology choice and also the effect of the choice of assessment method. Absolute stand-alone values can be misleading in analyses, and the use of different impact calculation approaches in parallel is clarifying the limits of using LCA-based approaches. The ESC has been discussed for the recast of the Renewable Energy Directive. Potential EU-wide results are presented.

The comminution of fuelwood for efficient transportation and handling exposes the material to various biological and chemical decomposition processes. The stockpiling of fuel chips can result in significant dry matter losses (DML) and consequent release of CO2 into the atmosphere. The decomposition processes could be controlled by managing the chip moisture content (MC). MC control by utilizing the self-heating of stockpiled stemwood chips together with wind-driven ventilation was tested in a practical storage experiment, using uncovered and plastic-covered piles as references. The data were analyzed with linear mixed models. The predicted DML was 2.4–3.8% during the monitoring period of 5.9 months, but no significant differences appeared between the storage treatments. The increase in the basic density of the chips decreased DML. On average 1.7–3.5% of the recoverable energy content of the chips was lost during the experiment. The predicted average decline in the MC was ca. 4–8 percentage points (p.p.). The MC of the chip samples stored under plastic tarp was 4–5 p.p. lower than those stored in the uncovered piles. Heat generation within the piles was modest due to the high quality of the chips, and the ventilation solution tested only marginally affected the drying process and the mitigation of DML.

Wood pellets have become an important fuel in heat and power production, and pellet markets are currently undergoing rapid development. In this paper, the pellet markets, raw materials and supply structures are analyzed for Sweden and Finland, based on a database of the current location and production capacity of the pellet producers, complemented with existing reports and literature. In Sweden, a total of 94 pellet plants/producers were identified, producing 1.4 million tonnes of pellets, while the domestic consumption was 1.7 million tonnes, and about 400,000 t of pellets were imported to fulfil the demand in 2007. In Finland, 24 pellet plants/producers were identified and the production was around 330,000 t while the domestic consumption was 117,000 t in 2007. In Finland, pellet market has been long time export oriented, whereas domestic consumption has been growing mainly in the small scale consumer sector, estimated 15,000 households had pellet heating systems in 2008. In the future, the increasing number of pellet users will require a reliable delivery network and good equipment for bulk pellet deliveries. Provision of new raw materials and ensuring the good quality of pellets through the whole production, delivery and handling chain will be fundamental in order to increase the use of pellets and sustain the ability to compete with other fuels.

ABSTRACTTree stumps could be a source of renewable energy, contributing to a reduced dependence on fossil fuels. In Finland, stumps are currently harvested when the ground is not frozen to avoid co...