Carbon Emission Pathways of Biodegradable Thermoplastic-based Species in Natural and Simulated Aqueous Conditions

Abstract

This study assessed the carbon emission pathways of the biodegradation processes of bio-based thermoplastic moieties in two aqueous (surface and simulated marine water) environments and its implications on environmental quality. The physicochemical parameters of the aqueous media were determined using standard methods. The American Society for Testing and Materials’ standard was used to assess amount of CO2 evolved. Cellulose, bioplastic and polyethylene were inserted in two aquatic environments and arranged thrice in a randomized experimental arrangement of 2x4x3. Ultimate biodegradations of the test films were monitored using Scanning Electron Microscopy (SEM). The amount of CO2 evolved was assayed using the titration method. Data obtained were subjected to descriptive and inferential statistical analyses using Statistical Packages for Social Sciences (SPSS) version 25.0. After biodegradation, the initial values of the physicochemical parameters were within recommended values of the WHO standards with slight (less than 2%) differences. Moreover, CO2 captured from the two aqueous  conditions were lower than the amount of CO2 evolved in aqueous solution with cellulose which is a natural polymer in this order: 88.725×102 mg from the soaked cellulose samples in marine > 85.215×102 mg of CO2 evolved from cellulose entrenched in surface  water > 82.758×102 mg of CO2 evolved from bioplastic soaked in marine water > 82.758×102 mg of CO2 evolved from bioplastic soaked in surface water > 65.046×102 mg of CO2 evolved from polyethylene soaked in marine water > 60.152×102 mg of CO2 evolved from polyethylene soaked in surface water. Moreover, the SEM results revealed high level of biodegradation and growth of biofilm on the biodegradable thermoplastics while the nylon 6 had little or no biofilm growth because of the recalcitrant nature. This study concluded that some biodegradable thermoplastics can biodegrade totally in aquatic environments without the release of greenhouse gases that could threaten the integrity of the aquatic environment as well as the release of toxic residues.