Publication: Life cycle assessment for polyhydroxyalkanoate production from bacteria treating palm oil mill effluent
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Date
2023-08-01
Authors
Lim Rong-Er
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Abstract
Biobased biodegradable plastic is commonly recognized as environmentally friendlier plastic because it is made by renewable resources and its life end compostable process. Among various types of bioplastic, the performance of polyhydroxyalkanoate (PHA) is outstanding. PHA is a bioplastic naturally produced by bacteria but it is expensive due to the limited production. In this study the life cycle assessment for PHA production from bacteria treating palm oil mill effluent (POME) was investigated. The study was carried out in two parts. The first part was divided into three stages. In the first stage, the POME was treated in an anaerobic reactor. In the second stage, the anaerobically treated POME was further treated using aerobic granules in an aerobic reactor. In the third stage, the aerobic granules were harvested from the aerobic treatment reactor and the PHA was extracted from aerobic granules. The Life Cycle Inventory and Life Cycle Impact Assessment were carried out for all the three stages. In the second part of the study, five different PHA extraction methods were investigated to identify the most environment-friendly PHA extraction methods and identify the most contributing factor within the methods. Result from the first part of the study showed that treating POME using anaerobic, aerobic treatment and extraction of PHA from aerobic granules have brought three major environmental impacts and they are human toxicity, marine ecotoxicity and climate change. While the common main contributor for these three processes is due to electricity consumption. The second part of the study showed the environmental impacts of five different PHA extraction methods from aerobic granules. The methods using sodium hypochlorite (Method 1) and acetone (Method 2) had the lowest impact on all impact categories studied. The investigation have found aerobic granule cultivation, electricity consumption, and the use of trichloromethane are the key contributors to almost all impact categories. Further, Methods 4 and 5 have high impact in all impact categories because it does not undergo lyophilization process. In conclusion, the environmental impact of PHA extraction from aerobic granules is dependent on the efficiency of PHA extraction methods.