Integrated waste management for sustainable livestock and aquaculturing systems using microalgae

Abstract

As the world population continues to grow, the demand for high quality food will be on the rise. To meet the demands for safe and sustainable food, urgent agricultural practices are needed utilizing water, energy, land, and nutrient resources more efficiently. In this study, 10 different strains of microalgae from Chlorella and Scenedesmus genera were screened to test their capabilities to remove the nutrients of agricultural wastewater collected from a dairy farm. The most successful strain was cultivated in a custom designed reusable plastic photobioreactors operated in batch mode and fed with coagulated, filtered and 1/4 diluted farm wastewater. Physical and chemical parameters including total nitrogen, total phosphorus, chemical oxygen demand and total solids of photobioreactor influent and effluent were measured. Removal efficiencies of 59.4%, 64.2% and 95.7% were obtained for total phosphorus, total nitrogen, and chemical oxygen demand parameters, respectively. Biomass concentration of 1.8 g/L was achieved at reactor closure. To demonstrate a circular bioeconomy case by reusing agricultural wastewater nutrients, generated microalgal biomass was further explored as potential feed formulations for livestock and/or aqua-culturing operations by analyzing protein, carbohydrate, lipid, vitamins, aminoacids, and fatty acid profiles using visible spectrophotometry, LC-MS/MS and GC-FID. Overall, the study aimed to optimize general and specific parameters of a low-cost microalgae-based agricultural wastewater treatment application and generate value added bio-feed products for sustainable livestock production and aquaculturing operations.