Sustainable Production of Fertilizers via Photosynthetic Recovery of Nutrients in Livestock Waste

Increases in population and improvements in living standards have significantly increased the demand for animal products worldwide. However, modern livestock agriculture exerts significant pressure on the environment due to high material and energy requirements. These systems also generate significant amounts of waste that can cause severe environmental damage when not handled properly. Thus, if we wish to enable farmers to meet this increased demand in a sustainable way, technology pathways must be developed to convert livestock agriculture into a more circular economy. With this end in mind, we propose a novel framework (which we call ReNuAl) for the recovery of nutrients from livestock waste. ReNuAl integrates existing technologies with a novel biotechnology approach that uses cyanobacteria (CB) as a multi-functional component for nutrient capture and balancing, purifying biogas, and capturing carbon. The CB can be applied to crops, reducing the need for synthetic fertilizers like diammonium phosphate. Using manure profiles obtained from dairy farms in the Upper Yahara region of Wisconsin, we construct a case study to analyze the environmental and economic impacts of ReNuAl. Our results illustrate that the minimum selling price (MSP) of CB fertilizer produced from deploying ReNuAl at a 1000 animal unit (AU) farm is significantly higher than the cost of synthetic fertilizers. We also observe that ReNuAl can return environmental benefits in areas such as climate change and nutrient runoff when compared to current practices. As a result, we see that consideration of environmental incentives can significantly increase the economic viability of the process.