Design of a Centralized Bioenergy Unit at Comarca Lagunera, Mexico: Modeling Strategy to Optimize Bioenergy Production and Reduce Methane Emissions

A centralized bioenergy unit was simulated, focusing on optimizing the manure transport 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 selecting 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 m3/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 decentralized 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.

The Economic Performance of an Integrated Biogas Plant and Proton Exchange Membrane Fuel Cell Combined Heat and Power System (PEMFC-CHP) in Sweden

A Proton Exchange Membrane Fuel Cell Combined Heat and Power system (PEMFC-CHP) fuelled by the hydrogen-rich gas reformed from biogas may be seen as an efficient and sustainable technology. This system can provide electrical and thermal energy dynamically to residential applications. In this study, an assessment of the economic performance of an integrated biogas plant and PEMFC-CHP for Swedish electricity and heat prices is presented. The economic factors considered are the capital and operation & maintenance (O&M) costs of the biogas plant and the PEMFC-CHP, the price of heat and electricity, and the value of the digestate as fertilizer. The analysis includes two cases: 1) both biogas plant and PEMFC-CHP are located on the farm. The farm sells the electricity and heat to the power grid and district heating system, respectively; 2) the PEMFC-CHP is located in a centralized-biogas plant, not on the farm. The manure is transported from farms to the plant. The plant also sells the electricity and heat to the power grid and district heating system. The results show that the farm-based and the centralized biogas plant have almost the same biogas production cost. The electricity cost of today, expected for 2020, and for the break-even of this integrated system are 530, 305 and 197 €/MWh, respectively. With the current trend of the fuel cell industry development, this break-even price may be reached in the near future.

The feasibility of a centralized biogas plant treating the manure produced by an organized animal farmers union in Turkey

The aim of this study is to evaluate the feasibility and the energy recovery potential of mesophilic (30–35 °C) anaerobic digestion of animal wastes (manure) at a centralized biogas plant (CBP) for 35,000 cattle. The proposed CBP is composed of an equalization tank followed by pasteurization and 3+[1/2] modules; i.e. each module consists of four completely mixed anaerobic reactors with a capacity of treating the manure from 10,000 cattle. The effect of maize silage loading, as the co-substrate, both on biomethane production and feasibility of the system was also evaluated. Besides, the transport fuel substitutes of the produced biomethane with or without co-substrate were also investigated. Results of the proposed CBP indicated that biomethane production increased ca. 1.65 fold with co-substrate addition and pay-back periods for one module treating 10,000 cattle manure are calculated to be ca. 11 and 7.0 yr without and with silage addition, respectively. Besides, considering the potential revenue when replacing transport fuels, about 74 heavy goods vehicles or 1,560 cars may be powered per year by the biogas produced from the proposed CBP where the co-digestion of manure and maize silage is applied.

Anaerobic digestion of macroalgae: methane potentials, pre-treatment, inhibition and co-digestion

In the present study we tested four macroalgae species – harvested in Denmark – for their suitability of bioconversion to methane. In batch experiments (53 °C) methane yields varied from 132 ml g volatile solids−1 (VS) for Gracillaria vermiculophylla, 152 ml g VS−1 for Ulva lactuca, 166 ml g VS−1 for Chaetomorpha linum and 340 ml g VS−1 for Saccharina latissima following 34 days of incubation. With an organic content of 21.1% (1.5–2.8 times higher than the other algae) S. latissima seems very suitable for anaerobic digestion. However, the methane yields of U. lactuca, G. vermiculophylla and C. linum could be increased with 68%, 11% and 17%, respectively, by pretreatment with maceration. U. lactuca is often observed during ‘green tides’ in Europe and has a high cultivation potential at Nordic conditions. Therefore, U. lactuca was selected for further investigation and co-digested with cattle manure in a lab-scale continuously stirred tank reactor. A 48% increase in methane production rate of the reactor was observed when the concentration of U. lactuca in the feedstock was 40% (VS basis). Increasing the concentration to 50% had no further effect on the methane production, which limits the application of this algae at Danish centralized biogas plant.

Integration of centralized biogas plant in cold-snowy region in Japan

A centralized biogas plant was built in Shikaoi town, Hokkaido, Japan to treat manure from 1320 cattle heads. The biogas plant was designed to operate at a feeding amount of 85.8 t/day, a hydraulic retention time (HRT) of 37 days and at a digester temperature of 38 ?C. In this study, the operational performance of biogas plant, utilization of digested slurry and economic balance were investigated. Since the working conditions of the plant became stable, the biogas production was 2,687 m3/day, 92% of produced biogas was consumed in power generation. Average methane concentration in produced biogas was 57.7%. The hydrogen sulfide (H2S) concentration was decreased to below 140 ppm as a result of bio-desulfurization and dry-desulfurization. The average power generation was 3,737 kwh/day and from that 54% of produced biogas was consumed in the facility operation, while 46% was sold to Power Company. About 20,260 t of digested slurry were applied onto 602 ha grassland and agricultural fields. From the results of the operational performance of the plant and the economic balance evidence, it is evident that the centralized biogas plant has a positive effect on the local economy.