Techno-Economic Analysis of an Integrated Process for Cyanobacteria-Based Nutrient Recovery from Livestock Waste

The dairy industry largely operates as a linear economy in which large amounts of non-renewable energy and mining resources are used for the production of synthetic chemical fertilizers (e.g., phosphate rock and ammonia). Moreover, significant greenhouse gas emissions (carbon dioxide, methane, nitrous oxide, ammonia) and nutrient emissions (phosphorus and nitrogen species) result from the improper management of manure waste, leading to the simultaneous degradation of valuable air, soil, and water resources. In this work, we present a techno-economic analysis (TEA) framework to investigate the viability of an integrated process that aims to recover nutrients from dairy manure. A central tenet of the proposed process (which we call ReNuAl) is that it uses cyanobacteria (CB) as a key integrative component that simultaneously: (i) harnesses renewable energy (solar energy via photosynthesis) to capture waste nutrients and (ii) captures carbon dioxide that results the anaerobic digestion of waste. Moreover, because biogas can be obtained via anaerobic digestion and CB biomass can be used as a concentrated biofertilizer, ReNuAl provides a pathway to a more circular fertilizer economy that helps manage air and water pollution. Our TEA framework is used to evaluate the phosphorus recovery costs and capital/operating expenses under varying levels of process integration. This analysis highlights key aspects of the process that have the most impact on economic/environmental performance and to provide performance targets for new CB strain variants.