Comparative techno-economic assessment of electricity and renewable natural gas production from dairy farm anaerobic digesters
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Camila Valderrama
Exhibition Number 123
Abstract
Anaerobic digestion (AD) is a promising solution for sustainable energy, converting underutilized agricultural and agro-industrial materials into bioenergy. Its main product, biogas, can be used raw or upgraded to generate electricity, heat, or Renewable Natural Gas (RNG). With high methane content, RNG can replace natural gas in pipelines and transportation fuels. Studies in the U.S. highlight AD’s potential for climate and environmental benefits. However, high initial costs and economic uncertainties limit adoption, especially for small and medium-sized dairy farms, which make up 86% of the industry but average only 200 cows. Currently, AD is economically viable mainly for farms with over 500 cows. This study examines co-digestion strategies and biogas upgrading to improve AD’s economic performance. Co-digestion, processing multiple feedstocks simultaneously, enhances methane yield, system stability, and nutrient availability. Upgrading biogas to RNG increases its value and potential applications. A techno-economic analysis evaluates cost-effective electricity and RNG production using dairy manure co-digested with switchgrass and corn stover, chosen for their environmental benefits and availability. The analysis considers capital costs, sustainability credits, RNG injection, feedstock collection, operational expenses, and transportation, particularly for centralized systems. Under the assumed conditions, AD results in negative cash flow due to capital and operational expenses. Future work will explore cost-sharing among multiple farms to develop economically viable systems.
Importance
The U.S. has the potential for 2,700 anaerobic digestion (AD) systems using dairy manure, yet only 255 are in operation. AD helps farmers convert manure into energy, providing electricity and/or an additional source of income. However, high investment costs have slowed its adoption. My research contributes to ongoing research in making AD technology accessible and financially viable for farmers and stakeholders. By analyzing the economic feasibility of different strategies, my research provides valuable insights into the real costs and benefits of AD. This study research will help guide better decision-making on AD adoption by considering current market and government incentives, advancing sustainable energy production.