(243d) Techno-Economic Analysis Towards Revalorization of Biomass through Pellet Production As a Heating Substitute of Methane and Natural Gas: Spain Case

The extensive use of fossil fuels such as coal and oil, burned for energy in the industry, transportation sector, and other human activities, has resulted in huge greenhouse gas emissions, composed mainly of CO₂, reaching levels above over 32Gt CO₂ per year (EPA, 2022). Moreover, the continued utilization of these fuels also contributes to air pollution and poses risks to human health. Over the last years, natural gas was positioned as the better fossil fuel to obtain energy, reducing emissions and improving efficiencies in combined cycle and cogeneration plants, boilers, and heating systems, as well as in domestic use. However, the current international situation with the Ukrainian War has exposed the European dependency on the supply of natural gas from Russia. Alternatives are to be developed and deployed towards energy security , using local resources to obtain energy and chemicals. Thus, cleaner energy sources and technologies, such as renewable energy and energy-efficient systems must be developed. Focusing on local resources, biomass has become more important in the last years. This may be used to produce biogas and biomethane through anaerobic digestion (Martín-Hernández et al., 2020), (Taifouris & Martin, 2018). Methane could be also produced from water electrolysis and CO₂ capture (De la Cruz & Martin, 2016), but that technology is still under development and it’s out of the scope of the study. The utilization of these processes to reduce energy dependence is not enough, so the use of biomass for the production of pellets has become an increasingly important new alternative to exploit and revalue local biomass, achieving a consumption to heat production in the EU around of 17 Mt In the year 2018 (European Pellet Council, 2019), and 23.1 Mt in the year 2021 (USDA, 2022). Pelletization is an increasingly widespread process, generally using lignocellulosic wastes from conditioning and pruning forests, agricultural wastes, etc., and submitting them to the set of operations that allow increasing their density and improving the physicochemical properties, minimizing the problems associated with transportation and storage, low density and moisture content. It consists of a set of operations based on previous drying, reduction, and homogenization of particle size, adjusting the composition of moisture, densification of the residues, cooling, and storage.

The problem is addressed as a multiscale facility location problem, which will allow deciding the better emplacement of the areas to obtain biomass, its transport, and treatment process. The problem is solved following the methodology presented by Heras & Martín (2021). The process yield, product, and investment cost of pellets are estimated based on a techno-economic analysis performed. The equation-based approach is used to model all of the processes. The dry biomass undergoes a crushing process to reduce the size of the particles. Next, part of the biomass will be conducted in a boiler, where it is burned to obtain energy, submitting the rest of the biomass to the following drying process, reducing moisture content up to 12%. Finally, the biomass will be subjected to a pressure granulation process. Depending on the energy needs of the plant, part of the pellets could be reintroduced into the process. Several biomasses are considered. Concerning the macro scale, the KPI of the process for each biomass will be used to formulate a network optimization problem to decide the place to obtain the residues and the best location to install the facility. The problem is formulated as NLP, which includes the social benefits in form of direct and indirect job generated, wealth, and CO₂ emissions in the location chosen to install the facilities and to transport the residues.

For the case study, Spain is selected, taking into account only the peninsula. The Balearic and Canary Islands, the autonomous cities of Ceuta and Melilla, and the rest of the Spanish enclaves in the Mediterranean Sea are not considered. On the one hand, the study is focused on biomass selection, thus lodgepole pine, eucalyptus, hardwood, switchgrass, and corn stover are chosen as the more appropriate lignocellulosic biomasses (Yancey et al, 2013). Later, a systematic comparison of product and investment costs, and income is analyzed to determine the more appropriate biomass for developing the process. On the other hand, the approach to the problem is focused on the facility location, selecting a total of 345 regions to place the facilities (Taifouris & Martin, 2022) depending on biomass availability. Generally, the central and south of the peninsula are the areas with higher probabilities to install the locations, due to the presence of more solar irradiation, huge water reserves to produce cereals, and the pine and eucalyptus growing.

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European Pellet Council. European Wood Pellet Consumption. https://epc.bioenergyeurope.org/about-pellets/pellets-statistics/european-consumption/; 2019.

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USDA. EU Wood Pellet Annual. https://www.fas.usda.gov/data/european-union-eu-wood-pellet-annual; 2022.

US EPA. Overview of Greenhouse Gases. https://www.epa.gov/ghgemissions/overview-greenhouse-gases; 2022.

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