An integrated Water Curtain-Microalgal Culture system (WCMC) to mitigate air emissions and recover nutrients from animal feeding operations

Abstract

Economically and technologically feasible air emission mitigation technologies are in high demand to sustain future animal agriculture. In this study, we designed an integrated Water Curtain-Microalgal Culture (WCMC) system to mitigate air emissions and recover nutrients to culture microalgae from Animal Feeding Operations (AFOs). The WCMC system included a water curtain, a windbreak wall and a raceway pond bioreactor. The water curtain was formed by continuously pumping water into a perforated water tank that flowed into the raceway pond bioreactor. The exhaust pollutants (NH3 and particulate matter-PM) from a poultry house were dissolved and absorbed by the water droplets. Microalgal species were collected from local ponds and went through natural selection. Desmodesmus (R. Chodat) showed the best tolerances of temperature, nutrients, pH, and circulation shear force. The microalgal culture in the bioreactor was run in batch mode and the average productivity was 12.7±2.9g/m2/day. Exhaust ammonia (NH3) and total suspended particle (TSP) concentrations were reduced by 74.9% and 89.2%, respectively. The harvested microalgal biomass had a protein content of 41.3%. The amino acid profile of microalgae demonstrated comparable quality to the WHO/FAO reference. Omega-3 fatty acids accounted for about 23% of total fat acids. Heavy metals (Pb, Cu, Fe and Zn) did not exceed the tolerance levels. The adaptation of this new technology will reduce AFOs environmental impact, create a win-win situation for future animal agriculture and microalgal cultivation, and generate new alternative protein sources as food and feed supplements.