Cost Assessment of Centralizing Swine Manure and Corn Stover Co-Digestion Systems

Abstract

Livestock in the state of Iowa, United States (US) produce over 50 × 106 Mg of wet-basis manure yearly. Biogas production from manure’s anaerobic digestion (AD) can reduce greenhouse gas emissions, control odors, and provide renewable energy. Despite these benefits, AD is rarely deployed at swine farms in Iowa. In this work, we explore the economics of AD systems in Iowa to evaluate reasons for low deployment and explore the production cost impacts of biogas cleaning and injection into the natural gas grid, amending manure with biomass, and centralizing digesters across multiple farms. This work presents a static, spreadsheet-based technoeconomic model that embodies literature-based estimates of key system technical parameters, costs, and transportation fuel incentives and permits the examination of various scenarios. Key findings include that under the model assumptions, distributed, farm-scale digesters are not competitive with average natural gas prices in Iowa. A centralized production scenario can be competitive, provided that programs such as the low-carbon fuel standard (LCFS) and the renewable fuel standard (RFS) have sufficiently high credit values.

Assessing Digestate at Different Stabilization Stages: Application of Thermal Analysis and FTIR Spectroscopy

“…Conversion into organic acids and subsequent degradation into methane follow a diversity of microbial pathways [9,10], ending with biogas as the product of interest and digestate as a residual by-product. Several digestion configurations have been proposed, including centralized and decentralized centers, partial decentralization by performing the initial digestion stage in small units and centralizing the subsequent digestion phase, or centralizing only the valorization of biogas after the initial digestion stage [11][12][13][14]. Regardless of the configuration option selected, a practical solution for the final disposal of digestate is necessary.…”

The Effect of Agricultural Biogas Plants on the Quality of Farm Energy Supply

“…A stable fermentation process and high biogas production efficiency must characterize all substrates used in biogas plants. An essential criterion in substrate selection is the possibility of using the digestate generated in the biogas plant, e.g., as a natural fertilizer [8,9].…”