Pilot Evaluation of Single Cell Protein from Waste Activated Sludge Biomass as a Nutritional Supplement in Poultry

Large amounts of protein are destroyed from unlikely resources such as municipal biosolids and single cell protein from waste activated sludge. Up to 95,000 metric tonne/yr could potentially be recovered from wastewater flows in Gauteng Province in South Africa for example, almost the same order of magnitude of the national protein demand as animal feed supplement. Single cell protein from wastewater sources has not been utilized because of the high content of toxic heavy metals and other potential carcinogenic pollutants in the wastewater streams and because of the negative public perception of using a short closed loop on human wastes. In this study, a pretreatment method, modified aqua regia dilute acid wash, was used to lower the metal content by approximately 60%. This resulted in 33% loss of amino acids in the acid washed WAS. A feed substitution test in poultry with different fishmeal:sludge ratios (0%, 25%, 50%, 75%, and 100%) showed no impact of sludge SCP on mortality rate. However, sludge substitution in the feed yielded weight gains and cost savings up to 46%.