New insights into anaerobic digestionhybridization, bioproducts and microparticles

Resum

The anaerobic digestion process has been studied for years, leading to numerous applications. Research in this technology has been focused on improvement through various scientific approaches: the most fundamental study of the process, the kinetics of the stages, the final use of the products and by-products obtained as well as pretreatments for process optimization, among other aspects. This biological process presents a significant opportunity for renewable energy generation and its integration into the energy mix. Furthermore, its implementation could lead to savings in greenhouse gas emissions and the mitigation of fossil fuel use associated with population growth. Emissions captured through controlled anaerobic digestion have enormous potential when dealing with agricultural organic substrates or residues from the anthropogenic activity since, these emissions account for 40% of methane released into the atmosphere spontaneously. Therefore, it is imperative to focus efforts on mitigating this effect through a better management of this agricultural activity within the primary sector. This involves a double approach to transform the sector by enhancing its profitability through the management of generated by-products and by mitigating its impact as a source of greenhouse gases, ultimately making it a much more sustainable process. In this context, livestock waste, by-products from basic cereal crops, or the agricultural product industry can significantly contribute to bioenergy generation in the primary sector. However, the biological transformation within the anaerobic digestion process will vary for each type of substrate due to their distinct chemical composition and physical properties. Thoroughly studying the different available by-products for management through anaerobic fermentation is critical to maximise their transformation. In this way, technological development in the anaerobic digestion process applied to the agricultural sector is fundamental for a biogas production implementation and a more efficient operation of the installations. This not only ensures environmental improvement but ultimately makes it profitable for the end user. The aim of this thesis is to investigate, at a laboratory scale, the emerging technologies in the anaerobic digestion process using organic substrates from agricultural activities. Additionally, the study includes their integration on a larger, real scale through a simulation projection based on experimental data. Specifically, the aim is to enhance the anaerobic digestion process by controlling and monitoring operating parameters through (i) microbiological analysis of the medium, (ii) the generation of high-value by-products during the process, (iii) the efficient use of microparticles addition to accelerate the biological transformation, (iv) the application of pretreatments on lignocellulosic wastes, and (v) the feasibility of integrating anaerobic digestion with other renewable energy sources. The results obtained confirm the potential of the anaerobic digestion process in the management of agricultural wastes and other by-products as an efficient, clean, and sustainable technology that favors the circular economy. The necessary transformation of the sector relies on such alternatives, which must also prove profitable for investment. Technological advancements in the process are essential to enhance its performance and encourage its widespread implementation.