(430e) Multiscale Analysis for the Substitution of Natural Gas Boilers Using Biomass

The progress of humankind has been tightly bound to the intense use of fossil fuels, resulting in large greenhouse gas emissions mainly composed of CO₂ whose levels are upwards of 36.8 Gt CO₂/year (IEA, 2022). Over the last decades, natural gas was positioned as the main fossil fuel to obtain energy in the combined cycle, cogeneration plants as well as in domestic heating systems. Nonetheless, the interruption of Europe's natural gas supply from Russia via the Nord Stream pipeline due to the Ukrainian War has resulted in substantial fluctuations in global energy prices, which leads to the need to develop alternative strategies towards energy security using local resources to obtain energy and chemicals. This fact, along with the transition to renewable and clean energy sources places biomass as one of the most promising alternatives for the future to guarantee energy security. It could be used through anaerobic digestion to obtain biomethane yet this process to reduce energy dependence is not enough to satisfy the demand (Martín-Hernández et al., 2020; Taifouris and Martín, 2018). In addition, the European Union agreed to phase-out boilers powered by fossil fuels in a gradual manner, whose installation will not be allowed as of January 1^st 2025 (European Commission, 2023). Concerning this scenario, the exploitation of lignocellulosic material can be carried out from X-to-power via generating electricity burning the biomass waste to supply heat pumps or power-to-X-to-power through pellet production.

The problem is approached as a two-level analysis bound by a multiscale techno-economic study. First, the process level includes the optimization of the performance of pellet factories, previously evaluated in the reference work (Cifuentes et al., 2024), and TPS, which includes a Rankine cycle and a cooling tower that is modelled are based on previous work (Guerras and Martín, 2020). Input-output models are developed to predict their yield and economics (CAPEX and OPEX). At the second level, the strategy decision-making one, an extended facility location problem (FLP) is formulated with the purpose of determining the optimal combination of the pair of technologies, satisfy the demand, as well as the spots to install the facilities to process the biomass through a supply chain, performed having regard to economic, social, and environmental factors. The structure of the model consists of five different layers, corresponding to biomass availability, biomass transformation factories to produce pellets, thermal power stations (TPS), electric knots, and customers. Before being supplied to the customers, it is first distributed to the electric knots located in transformer substations, and from there, electricity arrives at population centers. The pellets manufactured, as the objective is energetic, have to be transformed into energy with their experimental heating value outlined (Yancey et al., 2013). In order to validate the methodology, Spanish peninsular soil is selected which is divided into spatial units between the province and the municipality called agricultural shires (MAPAMA, 2024).

To meet the demand for heating within Spain, the optimal outcome is the installation of 18 TPS and 3 pellet factories based on corn stover and eucalyptus wood, with the consumption of 12.2% of the total lignocellulosic waste. The sum to be invested is up to 2,200 M€, where up to 13% corresponds to pelletization and the remaining 87% to electricity generation. Another 2 case studies were performed as the budget overpasses the Spanish Governmental fund for energy, 1,150 M€ (Gobierno de España, 2022), as the aggregate of the 15 regional ones (From 40 to 450 M€, being 1,600 M€ the total). Using the State budget, 2 TPS and 6 pellet plants are the results, however, by limiting the investment per region the obtained facilities are 10 TPS added to 7 pellet plants.

Acknowledgments

The authors would like to acknowledge Salamanca Research for the optimization licenses, Europa Union’s Horizon research and innovation program under the Maria Skłodowska-Curie grant agreement no. 778168 (IProPBio), the funding received from the Junta de Castilla y León and the European Commission under the program Contratación de Personal Técnico de Apoyo a la investigación por las Universidades Públicas de Castilla y León and the FPU PhD fellowship from the Spanish Ministry of Universities.

References

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