CH4 and CO2 Emissions from the Decomposition of Microplastics in the Bottom Sediment—Preliminary Studies

In recent years, a significant new threat to the environment has emerged, namely contamination with microplastics and their degradation products. The decomposition products of microplastics include, among others, greenhouse gases that are responsible for climate change. The article analyzes the emission of carbon dioxide and methane during the decomposition of various types of plastics in the form of microplastics in the bottom sediments in the presence of water. The research covers plastic materials made of polyvinyl chloride with a high and low content of plasticizers, polypropylene, and rubber. All analyzed microplastics generated the tested greenhouse gases. However, the quantity of gases generated depended on the type of polymer used. The highest concentration of methane, at 25,253 ppm after 180 days of incubation, was characterized by high plasticizer polyvinyl chloride, i.e., di (2-ethylhexyl) phthalate. In the case of carbon dioxide emissions, the values were comparable. The maximum value was obtained at 65,662 ppm for polypropylene microplastics. The influence of particle size on the amount of the emissions of these gases was also investigated. During the decomposition of microplastics in the bottom sediments in the presence of water, it was observed that the smaller the microplastic particles are, the greater the production of methane and carbon dioxide.