Excessive use of polymeric packaging materials has led to an oversaturation of the planet with packaging waste and a great need to find a replacement biodegradable polymeric material that could meet consumer as well as environmental purposes. This paper investigates the possibility of biodegradation of polymer blends of low density polyethylene (PE-LD) and thermoplastic starch (TPS) by composting. During the composting process, physicochemical parameters important for the implementation of the composting process were monitored, as well as microbiological analysis of the compost mass. The composting process was carried out in an adiabatic reactor at the laboratory level for 16 days. The optimization of the composting process was carried out using a first-order kinetic model important for the design and operation of the composting plant. Biodegradation of polymer PE-LD/TPS blends was monitored by weight loss as well as by observing changes in morphological structure with a light and scanning electron microscope before and after the composting process. The addition of TPS to low density polyethylene affected and promoted the biodegradation of polymer PE-LD/TPS blends. A higher share of TPS enabled higher mass loss, i.e. faster decomposition. TPS favors the biodegradation of polymer PE-LD/TPS blends due to the pronounced amorphous structure and hydrophilic character of TPS. It is a good source of food for microorganisms that are responsible for their biodegradation during the composting process.