Developing a Farm-Scale Water-Energy-Food-Waste Nexus Framework for a Closed-Loop Dairy Concept

Manure management is a significant component of livestock production. Intense livestock production is shown to have negative environmental impacts on air, water, and soil quality. That impact is largely due to manure management, where excessive manure is often applied to soil as fertilizer or stored in lagoons. Some thermo-chemical methods, such as gasification and pyrolysis, can transform manure from waste to resource. The closed-loop dairy concept uses these methods to create cow manure derived biochar for use as a soil amendment and water filtration medium. It has the potential to produce syngas and bio-oil for electricity production and replace land applied solid manure with biochar that further mitigates environmental impacts. Implementing the closed-loop concept, however, would require capital and maintenance cost that may outweigh the benefits. For this thesis, a nexus-based tool for tradeoff analysis and resource allocation was built to evaluate the economic, environmental and social feasibility of the closed-loop dairy concept. With crop yield, biomass conversions, and environmental impact submodules, this tool utilizes several scenario levers to simulate a user-specified dairy operation. Such levers include livestock amount, acres farmed, effluent irrigation amount, distribution of manure and biochar products, and type of biomass conversions. Using financial estimates from central Texas in 2018, the profitability of such practices is evaluated against costs of a dairy and hay operation by this tool. This study showed that the profitability of the closed-loop dairy concept depends on the case. Results showed it may be worthwhile only for large operations because of the high cost of gasification or pyrolysis and that a dairy that fits this model would need to scale up by 3-4 times just to break even