Making wasteful, tasteful: Increasing circularity in agriculture by reclaiming post-processing poultry wastewater to produce hydroponic greens.

Abstract

To mitigate regional environmental pressures exerted on the Southeast by the increasing global demand for poultry products, post-processing poultry wastewater has been reclaimed for the cultivation of hydroponic greens. The system utilizes bioreactors designed to facilitate microbial interactions which transform available nutrients and degrade pollutants to support lettuce plants downstream. Lettuce is grown in deep-water culture under sole-source lighting on treated wastewater from two types of bioreactors, both inoculated with a consortium from a nearby aquaponics facility dominated by nitrifying bacteria. To increase treatment efficiency and microbial stability, one set of bioreactors is operated under conditions to promote algal growth, which has been shown to support the bacterial nitrifying community. While the growth of plants cultivated solely on wastewater showed reduced growth, diminished plant health, and altered morphology, the addition of supplemental nutrients to treated effluent showed no significant differences from the chemical control. This demonstrates that a waste-derived, organic fertilizer can partially replace mineral nitrogen fertilizer with no significant negative impacts on quantity or quality, while at the same time significantly reducing indirect energy costs (as over half of the energy dedicated to global agriculture is used in the production of mineral nitrogen fertilizer) and producing a sustainable waste management strategy to a growing industry vital to the region.