Aerobic Biodegradation of Algae-Derived Bioplastics Under   Controlled Composting Conditions

Background The scale of environmental damage caused by plastic pollution highlights the need to implement sustainably sourced biodegradable plastics within the global economy. Microalgae biofilms cultivated on rotating algae biofilm reactors using municipal wastewater are a possible feedstock for bio-based bioplastic production. Algix, a company based in Meridian, Mississippi, specializes in manufacturing bioplastic products from microalgae. Algix manufactures bioplastics for many products, including shoes and agricultural mulch films. The Sustainable Waste-to-Bioproducts Engineering Center in Logan, Utah has partnered with Algix and Central Valley Water Reclamation Facility in Salt Lake City, Utah to create a biodegradable polyester using microalgae biomass grown on a pilot-scale rotating algae biofilm reactor. However, Algix has not quantified the biodegradation characteristics of this bioplastic polymer blend. The purpose of this research was to generate, analyze, and present data concerning the biodegradation of these algae-based bioplastics under composting conditions. The ASTM D5338 method was used to expose the dog-bone bioplastic samples composed of 30% algae biomass to an aerobic composting process for 45 days. The bioplastic samples were also exposed to industrial-scale aerobic composting conditions for 12 weeks at Central Valley Water Reclamation Facility; the ASTM D6400 method was used to quantify the biodegradability of thin-film bioplastic samples under these conditions. Results Under controlled laboratory conditions, the bioplastics demonstrated approximately 13% biodegradation of the total mass, and 30% biodegradation compared to a cellulose positive control. A polyethylene negative control in the same form as the samples showed no biodegradation. Under industrial-scale field conditions, thin-film samples of the bioplastics completely disintegrated after 12 weeks of aerobic composting. Conclusions Although dog-bone bioplastics composed of 30% algae biomass did not show any significant signs of biodegradation under laboratory-controlled composting conditions, thin-film samples of the bioplastics demonstrated the ability to completely disintegrate under industrial composting conditions at a municipal water treatment plant. More research is necessary to compare biodegradation characteristics of the thin-film samples under laboratory conditions, and biodegradation characteristics of the dog-bone samples under industrial composting conditions.