Pilot-Scale Composting Test of Polylactic Acid for Social Implementation

Abstract

The chemical industry and subsequent value chain of plastics are facing significant challenges from the viewpoints of resource conversion and environmental burden. Now is the time to explore the future direction of plastics, which will require an integrated scheme using resource circulation, carbon neutrality, and a social system to promote after-use treatment under the concept of a circular economy. Polylactic acid (PLA) should help reduce greenhouse gas (GHG) emissions as a biobased material and contribute to waste management after use due to its biodegradability if managed properly. That is, it will be necessary to treat biodegradable products appropriately in closed systems such as composting facilities after use and recovery. To realize the implementation of fully approved composting facilities in society, simply evaluating biodegradability in the laboratory is insufficient. In this study, a pilot-scale test using PLA under actual composting conditions was conducted in accordance with both international standards and domestic evaluation methods. The results not only confirm its biodegradability and disintegration, but also demonstrate that the presence of a biodegradable plastic product has a negligible impact on the composting process. The obtained compost did not adversely affect plant germination or growth, demonstrating its safety and high quality. Such a multifaceted perspective makes this study unique and useful for creating a social framework.

Study of PLA pre-treatment, enzymatic and model-compost degradation, and valorization of degradation products to bacterial nanocellulose

“…However, this study highlights the possibility of optimizing PLA pretreatment towards improved composting in mild, home composting conditions, thus leading to reduced greenhouse gas (GHG) emissions and better waste management globally. Until proper PLA composting is established, not only in composting plants, but in households as well, it is somewhat pointless to use PLA and other biodegradable plastic products, since they will not contribute to waste reduction drastically (Kawashima et al 2021 ).…”

“…Although the detected weight loss seems modest, it must be considered that promising results reported in the literature come from composting PLA under industrial conditions, at elevated temperatures (45-60 °C) (Kulikowska et al 2020;Kalita et al 2021aKalita et al , 2021b, while in this study the composting was performed at 37 °C. Wilfred and coworkers showed similar weight loss of PLA films, 0.7%, after two-week incubation at 45 °C (Wilfred et al 2018), while weight loss of up to 90% is characteristic for composting at close to 60 ºC (Kawashima et al 2021;Boonmee et al 2016). Currently, temperatures achieved in home composts are lower than ASTM/ ISO test temperatures, so that compostable PLA in a home pile is unlikely to complete the process of biodegradation within the time limits.…”

Isolation of a Nocardiopsis chromatogenes strain that degrades PLA (polylactic acid) in pig waste-based compost

“…Many studies have the degradability of PLA products in a pilot scale compost, e.g., compost with ber, fat, and protein in animal fodder at 58°C [31]; compost with cow manure and wood waste at 60-65°C [12,13]; and compost with green yard waste at about 60°C [14]. In addition, in the PLA degradation test with our pilot scale compost [11], we used compost containing horse manure and plants. Because this was a fresh and large-scale compost with a total weight of 110 kg, the internal temperature was 70°C or higher at the beginning of the composting process.…”

“…In regard to social implementation, we published a paper that describes degradation of PLA products in compost on a pilot scale. The results revealed that the presence or absence of PLA products does not adversely affect the degradation process or the quality and safety of the resultant compost [11]. In addition, pilot and commercial-scale composts, which contain cow dung as the main component [12][13][14] or green yard waste as the main component [15,16,42] were used to test the degradability of PLA products.…”

“…For animal waste-based compost, a previous study examined cow dung and pig dung-composts for the degradation of food waste [10]. We previously conducted a pilot-scale composting study of PLA products to con rm that there were no adverse effects on the composting process as well as the growth of plants cultivated using the obtained compost [11]. To date, studies have examined the e ciency of PLA degradation in compost at pilot and commercial scales [12][13][14][15][16].…”