Preliminary evaluation of the anaerobic biodegradability of three biobased materials used for the production of disposable plastics

Biodegradable plastics have been introduced to the market to substitute "traditional", non-biodegradable, petro-based plastics to alleviate plastic pollution. Biochemical methane potential tests were carried out on compostable bags made of MaterBi®, biodegradable bottle wine corks and cellulosic plates to examine the anaerobic biodegradability of those materials. The impact of four factors: type of pretreatment (predigestion, mechanical, alkaline, predigestion and alkaline), digestion duration, type of inoculum and temperature were statistically evaluated through regression modeling. Anaerobic tests on compostable and polyethylene bags (control) were carried out in mesophilic (35 °C) and thermophilic (55 °C) conditions, while tests on bottle wine corks and cellulosic plates were carried out in mesophilic conditions only. After 15 days of digestion, a dry mass reduction of 22.8 ± 6.2 % and 27.6 ± 14.0 % for mesophilic and thermophilic tests respectively was recorded for MaterBi®. Chemical pretreatment with NaOH led to a mass reduction of 78.2 ± 7.2 % and was the only statistically significant factor to affect both methane yields and dry mass loss. A higher digestion temperature led to an increased mass loss without a concurrent increase in methane production. The cellulosic plates were completely degraded (99.9 ± 0.03 % mass reduction), while the wine bottle corks weight did not change.