Supercritical water gasification of effluents from composted human excreta and recycling of the aqueous phases for microalgae cultivation

Effluents from composted human excreta were sampled and characterized. Results show a constancy in the characteristics and nutrient content of these effluents. Then, these effluents were treated with supercritical water gasification, producing hydrogen rich gas (67-69%). Carbon efficiencies of 41-43% were achieved. Microalgae Chlorella vulgaris (CV) and Phaeodactylum tricornutum (Ph.t) cultivation were studied in the gasification aqueous phase (AP). No growth was observed in the raw AP even with adjusted pH. CV could grow in the activated carbon treated AP with similar results for cell concentration and pigment content, but with higher biomass production than in its control medium. Ph.t was unable to grow even in the treated AP. These results show promising development in recuperating energy and nutrients from effluents from composted human excreta, combining energy production, microalgae valorization and contributing to close the nutrient loop.