Life cycle assessment on methods for polyhydroxyalkanoate extraction from aerobic granules

Aerobic granules were cultivated to accumulate polyhydroxyalkanoate (PHA) using palm oil mill effluent (POME) in a sequencing batch reactor (SBR). Five PHA extraction methods using different cell digestion chemicals, namely, sodium hypochlorite, acetone, sodium chloride, and sodium hydroxide, and without chemicals (control), were studied to identify the most environmentally friendly method and the most contributing factor within the methods. Method 1 (sodium hypochlorite) and method 2 (acetone) provided PHA yields of approximately 85% cell dry weight (CDW). The PHA that was recovered was a P3(HB-co-HV) co-polymer. SimaPro software version 8.5, developed by PRé Sustainability, was used to analyze the impact of the extraction methods on seven selected impact categories. Life cycle impact assessment of each of the methods for the production of 1 kg of dried PHA indicated that methods 1 (sodium hypochlorite) and 2 (acetone) had the lowest impact on all impact categories studied. It was found that the cultivation process of aerobic granules, electricity consumption, and usage of trichloromethane during PHA extraction were major contributors to all the impact categories.