The end of the European milk quotas in 2015 resulted in a steep increase of Irish milk production from 5 to over 7.2 billion litres annually. Dairy processing ads value, but generates up to 10 litres wastewater (WW) per litre processed. Organic pollutants in the WW need to be removed before discharge. Our approach aims to turn this waste into a resource for polyhydroxyalkanoates (PHA), bioplastic production. Bioplastics are promising materials to reduce our dependency on fossil fuels and waste production. The first production step includes an adaption of the dairy processing WW in an anaerobic, hydrolytic reactor, where acidogenic bacteria metabolise the organic fraction of the WW and form volatile fatty acids (VFAs) the building blocks of PHA. The second step comprises the adaption of biomass towards PHA accumulation. The adaption is driven by an aerobic dynamic feeding strategy to increase the formation of the storage molecule PHA. Addition of the WW as substrate is followed by a starvation period, where bacteria capable of PHA storage have a selection advantage. Over time the mixed microbial system is therefore optimised for PHA accumulation. In a final production step the adapted WW and biomass is combined in a fed-batch reactor to produce the end product PHA. The laboratory scale system could be established and is currently optimised. A later scale-up will help to assess the full economic potential of this waste to value approach.

  • This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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