Can biodegradable plastics solve plastic solid waste accumulation ?

Abstract

Polymers are fast becoming a serious environmental hazard, and are normally disposed of through landfilling, recycling, and incineration. Landfill sites are becoming increasingly scarce, and incineration contributes to air pollution and global warming. Recycling is still not applied in most countries of the world. The uncontrolled disposal of plastic waste gives rise to a large amount of plastics ending up in the earth’s oceans, where they degrade very slowly into micro-plastics that are consumed and converted to toxic persistent organic pollutants by marine fauna. Biodegradable polymers, which can be petrochemical- or bio-based, may be a solution to these problems. They can be degraded by microorganisms to CO2, water, and biomass through a process of biodeterioration, bio-fragmentation, and assimilation. Although a large number of bacteria and enzymes have been identified to biodegrade these polymers, they cannot universally degrade all kinds of biodegradable polymers, and the effectiveness and/or rate of biodegradation depend on the polymers’ morphology and physical properties. In many cases the microbial degradation has to be preceded by UV- or hydrolytic degradation, or a specific composting environment has to be created. Even if biodegradable polymers with acceptable properties can be synthesized, and if most of the existing nonbiodegradable polymers can be replaced by biodegradable polymers, commercial composting sites still have to be established in all the countries of the world. As in recycling, the different biodegradable polymers will have to be separated, and the different kinds of polymers will have to be composted in environments that contain microorganisms that are effective for the biodegradation of the specific polymer(s).