Sustainable bioconversion of ice cream waste into bioenergy and bioproduct

Abstract: Ice cream waste is a new food waste stream that occurred 20 years ago since the implementation of the Food Allergen Act. Ice cream waste is generated from overproduction or imperfect storage. The current treatment involves landfilling, contributing to greenhouse gas emissions， or animal feed, incurring additional costs from storage and transportation. We focus on sustainably utilizing ice cream waste for bioenergy and bioproduct production through novel, cost-effective biomanufacturing approaches and integrated techno-economic analysis (TEA). In this research, four bioconversion pathways were developed, and four types of bioenergy and bioproduct were produced, i.e., biodiesel, bioethanol, methane, and a mixture of peptone and glucose/lactose. (1) Ice cream waste was treated with various proteases, and the fat was separated from the ice cream waste under various centrifugation conditions. The separated fats were transferred to fatty acid methyl esters or biodiesel using lipase-assistant saponification. The biodiesel produced was analyzed using GC-MS. The six most abundant fatty acid methyl esters were methyl palmitate, methyl oleate, methyl stearate, methyl myristate, methyl laurate, and methyl linoleate. (2) The defatted fractions were freeze-dried to be the mixture of peptone and glucose/lactose, which can be used as media for cell culture by providing nitrogen and carbon sources. The amino acid composition of the media product was comparable to that of commercial peptone measured using LC-MS. (3) In another pathway, the ice cream waste was incubated with K. lactis and S. cerevisiae for ethanol production, during which the levels of glucose, sucrose, lactose, and ethanol were monitored using HPLC. (4) We also conducted anaerobic digestion to use ice cream waste as a co-substrate for methane production. The optimal bioconversion conditions, yield, and composition, were obtained for the four types of bioenergy and bioproduct. TEA models of each bioconversion pathway were developed to determine economic viability.