ECO-CBET: Modular Electrochemical Processes for Simultaneous Nitrogen Recovery and Carbon Dioxide Mitigation

Livestock farming is an essential branch of agriculture that provides protein-rich food products to humans. However, ruminant animal systems produce substantial amounts of greenhouse gas emissions and can have deleterious environmental impacts. Such livestock systems are increasingly under pressure to become more environmentally sustainable.

Many of the environmental issues stem from the release of livestock manure constituents, including nutrients, pathogens, and organic matter, into the environment. These releases contaminate surface and ground waters, increase the risk of climate change, cause nuisance odors, and, ultimately, pose a threat to human and animal health. In addition, manure’s high water content and low nutrient density increase the transportation cost to farmlands and limit its effective use.

Recovering nutrients from manure can improve nutrient management and minimize the possibility of negative environmental impacts. Climate impacts could be further mitigated by converting the carbon dioxide in the biogas generated from manure processing into fuels and other useful products. This project, a collaboration between investigators at the University of Wisconsin–Madison and Massachusetts Institute of Technology, seeks to overcome the challenges facing manure processing systems through the development of novel modular electrochemical processes.

The proposed system will integrate electrochemical processes to simultaneously recover ammonia from livestock manure as fertilizer and convert carbon dioxide to locally-valuable chemicals. The knowledge generated from this research will address the growing need for sustainable and effective livestock manure management. The team will engage K-12, undergraduate, and graduate students in STEM outreach and research experiences.

Students identifying as a member of an underrepresented group in STEM will be recruited and mentored through partnerships with on-campus organizations. Benefits to society will also be achieved through outreach and education activities for farmers, policymakers, agriculture educators, and the general public.

Livestock manure can lose nutrients, pathogens, and organic matter to the environment, degrading both surface and ground water quality, contributing to climate change, and creating human and animal health issues. Processing manure to recover embedded nutrients can mitigate these impacts by increasing nutrient density, making a more manageable fertilizer that can be economically transported to remote locations.

The overall goal of this ECO-CBET project is to develop modular electrochemical processes to tackle carbon, nutrient, and water challenges in livestock manure systems by recovering ammonia as fertilizers with increased nutrient density and producing valuable chemicals from carbon dioxide for on-site application. These electrochemical processes are uniquely enabled by redox reservoirs, which reversibly store electrons and specific ions while serving as interchangeable counter electrodes for flexible integration with complementary electrochemical half-reactions.

The ammonium-rich manure wastewater can be fed into a galvanic cell with a bioelectrochemical anode and a redox reservoir cathode that selectively extracts ammonium cations from the milieu. The redox reservoir is introduced into an electrolytic cell, where it serves as an anode, releasing ammonium, and is paired with a carbon dioxide-reducing cathode for co-generation of useful products, including formic acid, a supplemental animal feed preservative, and methane, a renewable feedstock that can be injected into natural gas pipelines.

The specific objectives are: 1) develop the pretreatment of livestock manure, synthesize and characterize new redox reservoir materials, and demonstrate the feasibility of redox reservoir-enabled selective ammonia recovery from manure; 2) integrate ammonia recovery with carbon dioxide conversion to value-added products in modular systems; and 3) perform techno-economic and life cycle analyses of individual and combined modular systems. The success of this project will introduce transformative concepts for more efficient nutrient and carbon resource recovery from manure, generate new insights for distributed and sustainable chemical manufacturing, train the next generation of interdisciplinary scientists and engineers, and provide exciting STEM outreach and education opportunities at the intersection of the farmers, policymakers, agriculture educators, and the public.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.