Producing polyhydroxyalkanoate (PHA) from the organic fraction of municipal solid waste (MSW) using a mixed microbial culture.

In Europe, around 87.6 million tonnes of food waste are produced each year. This food waste has been viewed as a potential or actual source of a number of low-value and high-value products. A recent report has looked at the complete process of how food waste can be used to produce one high-value product - polyhydroxyalkanoate (PHA) - the basis of a class of biodegradable plastics. The report examines how the process of first producing organic acids from the food waste can be maximised. The organic acids are then converted to PHA.

Using a 100L anaerobic percolation biocell reactor to optimise the process, each kg of food waste could produce 151 g of organic acids. Each kg of organic acids could then be converted into 223 g of PHA. This equates to each kg of fresh food waste producing c. 33 g of PHA, or each kg of total solids in the food waste producing c. 114 g of PHA. The PHA produced contained 53% hydroxybutyrate and 47% hydroxyvalerate.

The report gives a value for the PHA of $2,600 - $5,800/tonne. The value of PHA that could theoretically be produced from food waste in Europe is therefore calculated to be $7.6 - 16.9 billion.