Analysis of secondary waste from a plastics recycling plant for the production of carboxylic acids

The production of bio-based platform chemicals through the chain elongation of short-chain carboxylic acids to medium-chain carboxylic acids by ethanol-acetat fermentation can be a contribution to the circular economy. To avoid further waste, secondary waste that already contains short-chain carboxylic acids can be used. The potential for the production of bio-based carboxylic acids from a secondary waste of a recycling plant for plastic waste is examined in this paper. Therefore, practical experiments with the process water of a recycling plant for plastic waste were conducted in order to assess the potential for carboxylic acids production. At the end of the experiment, the concentrations achieved by chain elongation in the secondary waste result in 496 mg/L butyric acid and 87 mg/L caproic acid and the concentration in the extraction solvent is 933 mg/L caproic acid. To conclude, chain elongation of carboxylic acids in secondary waste, in this case the process water from a treatment plant for plastic waste, is generally possible. In order to estimate the total potential for the production, the fluctuations of the quality of the process water have to be considered.