Impact of Dispersing on the Production and Extraction of Bio-Based Basic Chemicals from Biogenic Secondary Waste

Biogenic waste from waste treatment plants, secondary waste, can be used to produce bio-based carboxylic acids, conventionally produced by chemical synthesis from petroleum-based feedstocks or by synthesis from natural oils. The cascading use of organic residues and wastes to produce bio-based products can contribute to the circular bioeconomy. In the process of biologically treating waste to produce bio-based carboxylic acids, microorganisms already present in the secondary waste use ethanol to convert short-chain into medium-chain carboxylic acids. The medium-chain carboxylic acids were separated from the secondary waste using in-situ extraction (liquid-liquid extraction). In previous studies, laboratory-scale bioreactors without a dispersing function were used. To optimise production and extraction of medium-chain carboxylic acids, the bioreactors were equipped with a device to disperse the extraction solvent in the secondary waste. By increasing the surface area between the phases, the ability to extract the medium-chain carboxylic acids was improved. The study aimed to evaluate the impact of this dispersing process. Production and extraction rates of static bioreactors without dispersing were compared to those of dynamic bioreactors with dispersing on a laboratory scale, using leachate from a composting plant as secondary waste. The results confirmed that dispersion has a positive effect on the process. Dispersing increased the reduction of the nutrient ethanol, the production of medium-chain carboxylic acids in the secondary waste and the extracted medium-chain carboxylic acids.