# Valorization of Agri-Food Waste into PHA and Bioplastics: From Waste Selection to Transformation
## 3 Production of Bioplastics from Volatile Fatty Acids
### Economic Aspects and Technology Barriers  
Biodegradable bio-based polymers are potential candidates for the replacement of traditional fossil-based polymers, due to the consideration of pollution and sustainability [243]. The production of polyhydroxyalkanoates (PHAs) from waste originating from the agri-food industry and through various microorganisms is a promising and sustainable alternative to petroleum-derived plastics [244]. However, a significant challenge confronting the widespread adoption of these biopolymers is the high cost associated with their production. A recent study by [PERSON] et al. [245] revealed that PHA can be produced from biogas at a competitive market price (8.6-8.8 \(\upmu\)G/kg PHA) in medium-sized waste treatment plants, irrespective of the economy of scale and technological readiness level. The study also revealed that the optimal scenario for the valorization of biogas within a waste treatment plant involves the use of cogeneration units powered by biogas, which would result in lowering PHA market prices by almost half (4.2-4.6 \(\upmu\)G/kg PHA). Bioplastics have also been shown to exhibit a reduced energy consumption of 57 MJ/kg for their production compared to traditional plastics (77 MJ/kg) [246]. However, as previously referenced, the manufacturing costs of bioplastics remain high. It is estimated that the price of biopolymers is between 2 and 5 times higher than that of conventional plastics [15; 247], ranging from EUR 2 to 6 per kg (depending on the quantity) compared to EUR 1-2 per kg for traditional plastics [248; 249; 250]. The production cost of PHA depends on three main factors, as reported by [PERSON] et al. [203]: (1) the cost of the fermentation substrate; (2) the volumetric productivity of the process (g/L/h); and (3) the percentage of PHA content in the cell. It is estimated that at a scale of 100 kt, production costs range between EUR 2.5 and 6.5 per kg, depending on the microorganism that produces the PHA [251]. However, it is notable that the production costs of certain plastics, such as polyethylene (PE), are less than EUR 1 per kg [203]. The economic viability of current PHA production remains a significant challenge when compared to fossil fuel-derived plastics, which are typically used in high-volume, low-cost applications. Given that raw materials for the manufacture of PHAs constitute a key component of costs, waste, or low-value substrates acquire great relevance and continue to be the main focus of numerous studies and development initiatives around PHAs. Areas for improvement have been identified in the fermentation processes, the scalability of these processes, and the subsequent processing [252]. The utilization of waste materials such as milk, wine, wood, and beet molasses as substrates for the fermentation of microorganisms capable of synthesizing PHAs has been demonstrated to reduce costs and minimize the environmental impact through the reuse of waste products [244]. The production of bioplastics from food loss and waste (FLW) is a viable alternative. However, the assessment of FLW is currently limited by its low technological maturity and significant logistical challenges. This requires a tailored approach to process design and implementation, considering regional specificities, feedstock availability, and regulatory and infrastructural frameworks. A commendable example of strategies that aspire to rectify economic bottlenecks for PHA commercialization is evident in the PROMOFER project [28], funded by the EU Commission. The objective of the project is to optimize the fabrication of bioplastics by utilizing waste as a primary constituent and by boosting pretreatment and extraction processes to maximize the yield of polyhydroxybutyrate (PHB) production. The PHB obtained will be utilized in flexible packaging as biodegradable coatings with specific properties, and in agriculture as biodegradable geotextile nets.