According to the Food and Agriculture Organization (FAO) of the United Nations, there is about 1.3 billion tonnes of food waste every year.
In 2016, a new company called Genecis had the idea to use food waste for production of bioplastic, producing PHA (polyhydroxyalkanoate) with the help of bacteria. From the fermentation of 1.8 tons of food waste, they can produce 50-70 kg of bioplastic per week. That is a modest win, perhaps, but there is hope that improvements in the process will raise the yields.
Practcally, it would be impossible–theoretically, however, if one could collect all of the human food waste (1.3 billion tonnes per year) and use it to produce bioplastic at the above conversion rate, it would yield about 40 million tonnes of bioplastic per year. Current consumption of plastic is about 400 million tonnes per year. So, bioplastic production from food waste cannot meet the current demand, but it sure would help!