Small-Scale Energy Conversion of Agro-Forestry Residues for Local Benefits and European Competitiveness

Dear Colleagues,

The current way to produce, convert and consume energy throughout the world is not sustainable. However, our economic growth and social development can be implemented only by means of an appropriate availability of energy services. Large-size plants present several problems: 1. high biomass supply; 2. authorization problems for the large-size plants; 3. Biomass conversion technologies more adapted to change biomass residual in energies. The small size plants are a technology for future energy supply systems. The unique and advantageous point in the combination of residual biomass and small-size plants results from the fact that biomass is a renewable source of energy which can be utilized most efficiently using gasification technology. Thermo-chemical processes can be seen as an energy-efficient technology for the transformation of biomass, especially lignocellulosic feedstock, into a syngas which can be used for various utilization routes (heat, heat and power, gaseous as well as liquid biofuels, chemicals, etc.).  The use of biomass for energetic purposes within Europe varies widely from country to country and from region to region, depending on the climate, the traditions in the use of the land, the available biomass and on the political and financial support for energy from biomass. In some European countries where the energetic use of biomass is considerably supported by national programs (e.g., Austria, Denmark, Finland and Sweden), biomass as a source of energy is already used to a remarkable amount. In Finland, biomass contributes with 17% to the fossil primary energy consumption. In Sweden, Portugal and Austria the share of biomass use is between 12 and 14%. The main biomass resources that are already widely used in Europe are:

• fuel wood in households for heating and for cooking;
• wood chips from thinnings and tree harvesting in district heating plants;
• wood processing residues in the wood processing industry and in district heating plants;
• residual wood and bark from wood processing including recovered wood products (i.e., demolition wood) in the wood processing industry and power generation sector and pulping liquors in the pulp and paper industry (particularly in the Scandinavian countries).

Biomass already contributes to the European energy supply to a certain extent, though, according to the assessments made above about the potential of biomass as a source of energy, this share could be considerably higher than it is today. From the shares of the currently used fossil energy carriers and the calculated biomass potential, the maximum reachable share of biomass to cover the energy demand can be calculated. The following enumeration shows the results of such calculations: i) Biomass resources below 10 % of the fossil energy supply in the Netherlands, Belgium and Luxembourg, United Kingdom, Germany, and Italy; ii) biomass resources between 10 and 30% of the fossil primary energy consumption in Denmark, Spain, France, Greece, Portugal and Austria; iii) biomass resources above 30% of the fossil primary energy consumption in Ireland, Sweden, and Finland.

Additionally, the share of the already-used biomass is analyzed against the background of the overall available biomass resources. This shows that, in nearly all of the EU-countries, only slightly more than 25% of the available biomass resources are currently used. In most countries, the share is even significantly lower. It is only higher in countries where the energetic use of biomass is promoted by governmental measures.

The increasing demand for energy and related environmental concerns are the main drivers for the strong interest in biomass residues in the agro-forestry sector and in appropriate small- scale energy conversion. Biomass residues (e.g., prunings, thinnings and forest residues) constitute a highly promising (and currently largely under-utilized) feed stock with a significant potential to be converted into useful end products. This Special Issue proposal has the overall aim of developing a network around technologies for small-scale energy conversion of forestry residues for local benefit and European competitiveness. The following targets will be addressed: i) to improve knowledge of different energy conversion processes for forest residues; ii) to develop an expert group on forest biomass supply chains; iii) to identify best practice for sampling of available forest biomass residues; and iv) to create agro-forestry-scale energy districts.

The purpose of this Special Issue is to publish high-quality research papers, as well as review articles, addressing recent advances on systems, processes, and materials for work safety, health, and environment. Original, high-quality contributions that have not yet been published, or that are not currently under review by other journals or peer-reviewed conferences, are sought.

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