At the moment, in most of the anaerobic digestion sites for management of Organic Fraction Municipal Solid Wastes (OFMSW), bioplastics are separated together with petrochemical plastic and their treatment does not differ. The marketing and use of biodegradable single-use products, such as shopper bags, sidesteps the problem of using common plastics without completely solving it. Therefore, there is a need to identify technological solutions that allow for the complete degradation of biodegradable plastics without the need to modify the process in place in organic waste treatment plants. For this purpose, on biodegradable plastics composed mainly of starch and PBAT, anaerobic digestion tests were carried out to assess whether the degradation kinetics are consistent with the digestion hydraulic retention time of the organic fraction. Tests of fungal pretreatment and anaerobic digestion of biodegradable plastics were conducted. Fungi were isolated from plastic fragments collected in an industrial composting plant. They were identified and used to set up degradation experiments of bioplastic bags. The tests were conducted for 60 days with sampling to check degradation efficiency every 20 days. The top three fungi in terms of bioplastic degradation were found to be: Cladosporium sp., Alternaria sp., and Didymella sp. The pre-treated plastic was used for anaerobic digestion experiments. The tests were conducted on a laboratory scale in combination with digestate and organic waste to allow the growth of anaerobic bacteria responsible for the degradation of waste material in composting plants. The results showed that adding organic waste to digestate increases the rate of PBAT degradation in the first 30 days. In general Alternaria sp. and Didymella sp. were the most effective in terms of PBAT degradation and were also able to produce degradation intermediates.
Fungal pretreatment and anaerobic digestion of biodegradable plastics
Federica Spina;Davide Ferrero;Cristina Varese
2023-01-01
Abstract
At the moment, in most of the anaerobic digestion sites for management of Organic Fraction Municipal Solid Wastes (OFMSW), bioplastics are separated together with petrochemical plastic and their treatment does not differ. The marketing and use of biodegradable single-use products, such as shopper bags, sidesteps the problem of using common plastics without completely solving it. Therefore, there is a need to identify technological solutions that allow for the complete degradation of biodegradable plastics without the need to modify the process in place in organic waste treatment plants. For this purpose, on biodegradable plastics composed mainly of starch and PBAT, anaerobic digestion tests were carried out to assess whether the degradation kinetics are consistent with the digestion hydraulic retention time of the organic fraction. Tests of fungal pretreatment and anaerobic digestion of biodegradable plastics were conducted. Fungi were isolated from plastic fragments collected in an industrial composting plant. They were identified and used to set up degradation experiments of bioplastic bags. The tests were conducted for 60 days with sampling to check degradation efficiency every 20 days. The top three fungi in terms of bioplastic degradation were found to be: Cladosporium sp., Alternaria sp., and Didymella sp. The pre-treated plastic was used for anaerobic digestion experiments. The tests were conducted on a laboratory scale in combination with digestate and organic waste to allow the growth of anaerobic bacteria responsible for the degradation of waste material in composting plants. The results showed that adding organic waste to digestate increases the rate of PBAT degradation in the first 30 days. In general Alternaria sp. and Didymella sp. were the most effective in terms of PBAT degradation and were also able to produce degradation intermediates.
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