Polyhydroxyalkanoate production from food residues.

Polyhydroxyalkanoate (PHA) is an important bioplastic, its production has been commercialized, and an increase of production capacities is expected. As with many other basic chemicals, PHA production requires a currently unavailable amount of renewable carbon if bioplastic production is ever to compete with plastic production from petroleum. This extensive demand for raw materials poses challenges in terms of costs, logistics, and land use. The application of biogenic residues is therefore one of the prerequisites for any economically significant and environmentally friendly PHA production. Against this background, recent findings on the possibilities of using biogenic residues from food production and consumption to produce PHA are summarized. Waste animal fats, waste cooking oil, but also mixed food waste, either from food production or consumer food waste represent the most abundant food-related residues. They are explored for their potential to serve as substrate for PHA production. While waste animal fat and waste cooking oil can be fed directly into suspension cultures, mixed food waste can be converted into short-chain carboxylic acids from microbial hydrolysis and acidogenesis in dark fermentation before being fed. Titers and productivity of the several feedstock options are compared. The potential for economically viable and sustainable production and integration into local material cycles is highlighted, although there are still several challenges to overcome. KEY POINTS: • Waste cooking oil enables low-cost and scalable PHA production • Thermally liquefied animal fats are a suitable feed for emulsifier-free PHA production • Coupling dark fermentation and PHA production is economically feasible • The impact of carboxylic acid composition on PHA synthesis is explored.