Already 300,000 to 400,000 years ago, humans started to use wood as an energy source. Until today, this has not changed much. More than two billion people worldwide depend on wood as their primary energy source and use woody biomass for cooking and/or heating, especially in developing countries (Kaltschmitt, Hartmann, & Hofbauer, 2016). This blog will discuss solid biofuels, some advantages/disadvantages, end-products as well as social and environmental challenges using this biomass resource.
Wood is the classical solid biofuel and a second-generation resource, used for thousands of years especially wood from forests. In most countries firewood is used as an energy carrier and it is a product from forestry management (e.g. timber for construction purposes). In addition to forest wood, woody biomass can also be grown on agricultural land. To maximize the average yield and minimize the needs for fertile land, tree plantations are harvested after a few years. Furthermore, wood as fuel can derive from production and consumption of wood and wood products as a residue, a by-product, or a waste material along the supply chain of wood as a raw material as well as pulp and paper products (see Figure 1). Thinning wood and forest residues are produced as a by-product during the production of stem wood as a raw material, for example case goods and furniture production. Industrial residual wood, bark, and wood dust are by-products or waste materials resulting from the production of timber and the manufacturing of wood constructions or wood products. At the end of the lifetime and after recycling some wood fractions, partly contaminated woody material and waste wood remain, which can be used as fuel too (Kaltschmitt, 2019) & (Ahurso, Medina, & Constantí, 2018).
Within the total range of energy carriers from biomass, the solid biofuels dominate the global picture. The main reasons for this are the relatively low costs and the mostly easy access to solid biofuels especially for the poorer parts of the population. Additionally, solid biomass can be used to provide solid, liquid, and/or gaseous biofuels as well as used for heat provision and electricity production. This sustainable provision and production of biofuels have the advantage of being climatically neutral and environmentally friendly compared with other sources of fossil fuel energies. In comparison to other renewable sources of energy, biomass can be used in very different sectors of the overall energy system. The market for heat, for electricity, and for transportation fuels can be fed by energy carriers made of solid biomass. Within all these markets, biomass already plays a certain and increasing role within the global energy system. This development already accelerates due to the policy actions such as the reduction of greenhouse gas emissions to achieve political goals. (Christ, Scherzinger, Neuling, & Kaltschmitt, 2019) & (Kaltschmitt, 2019).
Different conversion techniques developed in the past and are available on the global energy markets. Beside the provision of heat and/or electricity it is possible to produce secondary solid, liquid, and/or gaseous energy carriers characterized by different fuel-related properties. The conversion of solid biomass into these secondary energy carriers utilizes thermochemical processes. This thermochemical conversion proceeds through different conversion phases. Each phase delivers various products. End-products are synthetic natural gases (SNG) like biomethane, hydrogen or other gases (e.g. DME), solid charcoal, or liquids such as bio-crude oil, Fischer-Tropsch diesel and methanol (Kaltschmitt, 2019).
The utilization of woody biomass can be disadvantageous because of impacts on the environment. A biomass plantation depletes nutrients from soil, promote aesthetic degradation and increase the loss of biodiversity. A further negative aspect is the degradability of solid biomass caused by large distances transport activities as well as long-time storage. Disadvantageous is also that agro-forestry residues may have lower quality and contaminated with heavy metals. Furthermore, the low energy density and bulk volume of fresh woody biomass affect storage costs and transportation efficiency. The loss of biodiversity can be avoided through a careful forest management. This contributes the conservation of biodiversity as well as the water regulation, carbon sequestration and leads to recreational benefits in natural or planted forests. Another solution can be the production of agropellets for example, which avoid degradation and transportation issues. Additionally, the biomass energy density enhances, and the moisture content reduced, therefore the transport efficiency increase. The blending of different biomass feedstocks arranges suitable average composition and reduces pollutant loads (Domac, Verwijst, Richardsen, & Schlamadinger, 2003) & (European Biomass Industry Association, 2020).
Ahurso, R., Medina, F., & Constantí, M. (2018). Energies. Significance and Challenges of Biomass as a Suitable Feedstock for Bioenergy and Biochemcial Production: A Review. doi:https://doi.org/10.3390/en11123366
Christ, D., Scherzinger, M., Neuling, U., & Kaltschmitt, M. (2019). Thermochemical Conversion of Solid Biofuels: Processes and Techniques. In M. Kaltschmitt (Ed.), Energy from Organic Materials (Biomass) A Volume in the Encyclopedia of Sustainability Science and Technology, Second Edition (pp. 393-413). New York: Springer Science+Business Media, LLC. doi:https://doi.org/10.1007/978-1-4939-7813-7
Domac, J., Verwijst, T., Richardsen, J., & Schlamadinger, B. (2003). Sustainable Production of Woody Biomass for Energy. New Zealand. Retrieved from https://www.ieabioenergy.com/wp-content/uploads/2013/10/25_PositionPaper-SustainableProductionofWoodyBiomassforEnergy.pdf
European Biomass Industry Association. (2020). Challenges related to biomass. Retrieved 2020 September 19 from https://www.eubia.org/cms/wiki-biomass/biomass-resources/challenges-related-to-biomass/
Kaltschmitt, M. (2019). Biomass as Renewable Source of Energy: Possible Convertion Routes. In M. Kaltschmitt (Ed.), Energy from Organic Materials (Biomass) A Volume in the Encyclopedia of Sustainability Science and Technology, Second Edition (pp. 353-389). New York: Springer Science+Business Media, LLC. doi:https://doi.org/10.1007/978-1-4939-7813-7
Kaltschmitt, M., Hartmann, H., & Hofbauer, H. (2016). Energie aus Biomasse Grundlagen, Techniken und Verfahren (3., aktualisierte und erweiterte Auflage). Berlin, Heidelberg: Springer Vieweg. doi:https://doi.org/10.1007/978-3-662-47438-9