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 ac-complishments are significant step–changes in adding value to waste, and increased substrate utilisation rates will be attractive from a waste remediation perspective.