Economic Optimization of the Synthesis Section of a Small-Scale Biogas-to-Methanol Plant

As global concerns about carbon emissions and the sustainability of energy sources grow, the utilization of biogas has gained significant attention for reducing greenhouse gas emissions and moving away from fossil-based chemicals. Biogas, predominantly composed of methane and carbon dioxide, is generated through the anaerobic digestion of organic materials, such as agricultural residues, municipal waste, and wastewater sludge. To exploit the full potential of biogas and increase its energy density, the conversion of biogas into valuable chemical products seems to be a viable and feasible solution. Specifically, the production of methanol and the development of small-scale biogas-to-methanol plants has received notable recognition. This study focuses on the economic optimization of the synthesis section within such plants. The optimization of this section plays a crucial role in ensuring both the economic viability and the sustainability of the process. The synthesis section is modeled with two reactors arranged in series, where liquefaction of the methanol and water produced takes place after each reactor. To maximize methanol production, unreacted gases are recycled back to the first reactor. This article presents the economic optimization perspective on the reactor's design and operating conditions, finding a compromise between maximizing methanol yield and minimizing reactor costs. This study highlights the potential for biogas-based methanol in the transition between greener energy alternatives. Moreover, it offers a systematic procedure for optimizing the design of the synthesis sections, which is applied to a typical case study. By addressing the complex factors involved in this process, this research actively contributes to the progress of sustainable energy solutions and provides a valuable baseline for future development.