Characteristics of soil amendment produced from composting food waste and bioplastic bags

• This research characterized soil amendment produced by composting bioplastics. • Bioplastic and food waste were composted with or without a microbial activator. • The compost produced was suitable as a soil amendment. • The optimal C:N ratio for bioplastic degradation was 30:1. • The bioplastics were degraded within 20 days. The purposes of this research were to study the characteristics of soil amendment produced by composting food waste and bioplastic bags and to monitor the changes in the bioplastic bags during composting. This study used a 2 × 2 factorial in a randomized complete block design. Four composting conditions were investigated: food waste (T1t1), food waste with microbial activator (T1t2), food waste with bioplastic bags (T2t1), and food waste with microbial activator and bioplastic bags (T2t2). Except for the total Kjeldahl nitrogen content and the exchangeable potassium content, which were significantly different ( p < 0.05) between the treatments with and without bioplastic bags (T2 vs T1), the physical and chemical properties of the soil amendment were not significantly different between treatments ( P > 0.05). The total organic carbon, the C:N ratio, and the available phosphorus of the compost did not meet Department of Agriculture standards of Thailand after any treatment but were still suitable as a soil amendment. An experiment to optimize the initial C:N ratio for bioplastic degradation was performed. A C:N ratio of 30:1 generated the highest temperature throughout the experimental period. Higher temperatures are often associated with increased microbial activity, particularly of thermophilic microorganisms, which play a key role in the faster degradation of bioplastics. These findings suggest that an optimized C:N ratio is critical for promoting effective bioplastic degradation and this is achieved through enhanced microbial activity and thermophilic conditions. The bioplastic bags in compost were studied by scanning electron microscopy and were found to be degraded within 20 days.