(561b) Integration of Biogas Model (ADM1) for Economic and Environmental Analysis of Rng Production

Renewable natural gas (RNG) from farm anaerobic digestion (AD) can provide clean energy and additional products to farmers. Novel co-digestion substrates, such as prairie biomass, can provide synergistic qualities for AD that stabilize the reactor and increase methane (CH₄) production. Prairie biomass often requires less material input than other biomass and can impact the environment beneficially (such as the reduction of soil erosion).

This study focuses on a techno-economic analysis (TEA) and life cycle assessment (LCA) for the co-digestion of cattle manure and prairie biomass utilizing a biogas model, Anaerobic Digestion Model no. 1 (ADM1). While the full synergistic relationship of cattle manure and prairie biomass was not entirely captured, the addition of manure to prairie biomass increased CH₄ production for all scenarios analyzed.

The scenario with the largest CH₄ production from AD had the lowest estimated minimum fuel selling price (MFSP). This scenario was a 1:9 volatile solids (VS) ratio of prairie biomass to manure, with a MFSP decrease of 19.4% when compared to the mono-digestion of prairie biomass. While the feedstock price for prairie biomass was almost three times greater than that of cattle manure, the feedstock price did not significantly impact the MFSP. All impact categories analyzed had avoided burdens from the use of manure. The cultivation of prairie biomass had burdening effects due to the use of resources such as fertilizer.