The progressing degradation of the natural environment taking place over the last few decades and resulting from the systematically growing production of synthetic polymer materials led to the search for technological innovations aimed at producing environmentally friendly materials. Moreover, the increasing importance of sustainability promotes the development of bio-based and biodegradable polymers, sometimes misleadingly referred to as “bioplastics”. Inability to degrade synthetic polymer materials and the problem of their persistence in the environment even for hundreds of years have caused the production of polymer materials with the addition of components that may accelerate their degradation more and more important in recent years. Additionally, the growing interest in environmental issues makes the requirements for new materials that will not significantly burden the environment higher. In Poland 29.1% and 26.8% of post-consumer polymer materials, respectively, were recovered and recycled, which means that up to 44.1% of post-consumer polymer materials were sent to municipal landfills. In 2017, for the first time in Poland, more plastics were recovered (55.9%) than stored (44.1%). However, by 2020, the level of energy recovery and recycling of post-consumer polymer materials in Poland should cover a total of 84.5%. When looking at the average values for Europe (recycling 31.1%, recovery 41.6%, storage 27.3%), it should be noted that Poland has much to catch up in this area and decisive actions should be taken to actually solve this problem. For this reason, it is extremely important to know the mechanisms responsible for the degradation of polymer materials and understand the interaction between these materials and abiotic and biotic factors that cause structural changes in polymers. Recent studies show that knowledge of the conditions determining the decomposition of polyethylene polymer materials and their impact on the natural environment is still insufficient. The literature reports reveal many contradictory theories, especially those that relate to the degradation of polymer materials in the soil environment. This study constitutes a comprehensive review of researches on (bio)degradation of polymer materials over the last decades, various methods of polymer structure modification to increase the degree of their degradability, as well as methods of recycling post-consumer polymer materials. Because there is a need to assess the performance of polymer innovations in terms of their biodegradability, especially under realistic waste management and environmental conditions, to avoid the unwanted release of plastic degradation products to the environment.