Longitudinal Study of Wastewater Greases and Their Potential for the Production of Biofuels

Grease-trap waste (GTW) and sewage-scum grease (SSG) are under-utilized, high-lipid waste streams that have the potential to be converted into biodiesel. This paper presents a longitudinal study of GTW and SSG samples that were obtained over a 1 year period; GTW was sampled from a storage tank at a grease-collection company, and SSG was sampled from scum-concentration buildings at three wastewater resource recovery facilities. Samples were fractionated to quantify their lipids, secondary wastewater, and solids content. Results show that the average lipid content of SSG was seasonally dependent; lipid content was 15–40% in cooler months and 3–21% in warmer months. Alternatively, GTW showed an average overall lipid content of 4% in raw GTW; however, the floating layer from settled GTW had an average lipid content of 34%. These greases could serve as feedstocks for urban low-carbon biodiesel production while reducing the volume of biosolid waste disposal.