processes Article Design of a Centralized Bioenergy Unit at Comarca Lagunera, Mexico: Modeling Strategy to Optimize Bioenergy Production and Reduce Methane Emissions José Alberto Silva-González 1 , Inty Omar Hernández-De Lira 2, *, Antonio Rodríguez-Martínez 2 , Grace Aileen Ruiz-Santoyo 3 , Berenice Juárez-López 3 and Nagamani Balagurusamy 2, *   Citation: Silva-González, J.A.; Hernández-De Lira, I.O.; Rodríguez-Martínez, A.; Ruiz-Santoyo, G.A.; Juárez-López, B.; Balagurusamy, N. Design of a Centralized Bioenergy Unit at Comarca Lagunera, Mexico: Modeling Strategy to Optimize Bioenergy Production and Reduce Methane Emissions. Processes 2021, 9, 1350. https://doi.org/10.3390/ pr9081350 Academic Editor: Albert Ratner Received: 14 June 2021 Accepted: 29 July 2021 Published: 31 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Laboratorio de Biorremediación, Facultad de Ciencias Biológicas, Universidad Autónoma de Coahuila, Torreón 27000, Mexico; alberto_silva@uadec.edu.mx 2 Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autónoma del Estado de Morelos, Cuernavaca 62209, Mexico; antonio_rodriguez@uaem.mx 3 Facultad de Economía y Mercadotecnia, Universidad Autónoma de Coahuila, Torreón 27000, Mexico; grace.ruiz@uadec.edu.mx (G.A.R.-S.); berenice.juarez@uadec.edu.mx (B.J.-L.) * Correspondence: omar.hernandez@uadec.edu.mx (I.O.H.-D.L.); bnagamani@uadec.edu.mx (N.B.); Tel.: +52-871-234-4917 (I.O.H.-D.L.) Abstract: A centralized bioenergy unit was simulated, focusing on optimizing the manure trans- port chain, installing a centralized biogas plant, operation costs of the process, biogas upgrading, organic fertilizer production, and economic analyses. Comarca Lagunera from northeast Mexico was chosen as a study zone due to the existing number of dairy farms and livestock population (64,000 cattle heads). Two scenarios were analyzed: The first centralized scenario consisted of se- lecting one unique location for the anaerobic digesters for the 16 farms; the second decentralized scenario consisted of distributing the anaerobic digesters in three locations. Optimal locations were determined using mathematical modeling. The bioenergy unit was designed to process 1600 t/day of dairy manure. Results indicated that biomethane production was a more profitable option than generating electricity with non-purified methane. The amount of biomethane production was 58,756 m 3 /day. Economic analysis for centralized bioenergy unit scenario showed a net production cost of USD $0.80 per kg of biomethane with a profit margin of 14.4% within 10.7 years. The decentral- ized bioenergy unit scenario showed a net production cost of USD $0.80 per kg of biomethane with a profit of 12.9% within 11.4 years. This study demonstrated the techno-economical and environmental feasibility for centralized and decentralized bioenergy units. Keywords: biogas; centralized bioenergy unit; Comarca Lagunera; methane; process simulation; economic analysis 1. Introduction Mexico is a country with particular concern about greenhouse gas emissions (GHG) and energy generation. According to the National Inventory of Greenhouse Gas Emissions (INERE), the total GHG emissions in 2015 were estimated at 748 million tons of carbon dioxide equivalent (CO 2 eq.) units, in which energy production and agriculture accounted for 67.3% (503,817.6 Gg) and 12.3% (92,184.4 Gg), respectively [1]. This highlights the need to deploy strategies to reduce GHG emissions from both energy and agriculture sector. Anaerobic digestion is considered one of the most bioenergy-efficient technologies for reducing GHG emissions [2]. Under this context, biogas production from agricultural wastes such as animal manure offers a sustainable means to generate renewable energy and achieve GHG mitigation from the agriculture sector. Furthermore, Mexico has implemented several reforms in its laws to promote renew- able energies, such as the law on the use of renewable energy and the financing of energy transition (LAERFTE). The objective of these laws is that the electricity sector by 2024 must Processes 2021, 9, 1350. https://doi.org/10.3390/pr9081350 https://www.mdpi.com/journal/processes