Fermentative volatile fatty acid production and recovery from grass using a novel combination of solids separation, pervaporation, and electrodialysis technologies

A novel combination of solids screening, centrifugation, microfiltration, pervaporation, and electrodialysis were used for the targeted and exclusive recovery of volatile fatty acids (VFAs) from an 80 L bioreactor. The bioreactor was continually–fed with grass waste, containing 40 g L–1 total solids, over three, seven–day, hydraulic retention times. A VFA solution with a concentration up to 4,500 mg L–1 was recovered. VFA yields were also increased from 707 to 875 mg of VFA per gram of volatile solids by alleviating end–product inhibition. Both these accomplishments are significant step–changes in adding value to waste, and increased substrate utilisation rates will be attractive from a waste remediation perspective.