Production of volatile fatty acids by anaerobic digestion of biowastes: Techno-economic and life cycle assessments.

Production of volatile fatty acids from food waste and lignocellulosic materials has potential to avoid emissions from their production from petrochemicals and provide valuable feedstocks. Techno-economic and life cycle assessments of using food waste and grass to produce volatile fatty acids through anaerobic digestion have been conducted. Uncertainty and sensitivity analysis for both assessments were done to enable a robust forecast of key-aspects of the technology deployment at industrial scale.

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 80L bioreactor. The bioreactor was continually-fed with grass waste, containing 40gL total solids, over three, seven-day, hydraulic retention times. A VFA solution with a concentration up to 4,500 mgL was recovered.

Continuous recovery and enhanced yields of volatile fatty acids from a continually-fed 100 L food waste bioreactor by filtration and electrodialysis.

A novel method to recover VFAs from a continually-fed 100 L food waste bioreactor was developed using industrially applicable methods. The in-situ recovery of VFAs increased production rates from 4 to 35 mg g day by alleviating end-product inhibition and arresting methanogenesis, and electrodialysis was able to concentrate the recovered VFAs to 4000 mg L. There remains considerable scope to increase the production rates and concentrations further, and the VFAs were recovered in a form that made them suitable for use as platform chemicals with minimal refining.

Overcoming nutrient loss during volatile fatty acid recovery from fermentation media by addition of electrodialysis to a polytetrafluoroethylene membrane stack.

This research investigated the use of an innovative polytetrafluoroethylene (PTFE) membrane configuration coupled to electrodialysis for the in-situ removal of Volatile Fatty Acids (VFAs) from a mixed culture bioreactor. It was shown that by stacking the PTFE membranes to increase the active membrane surface area, shortened VFA recovery times was seen. The addition of electrodialysis to the PTFE membrane stack enabled the continuous extraction of VFAs from fermentation media whilst retaining essential nutrients and organic compounds in the diluate stream.