Optimizing algae based polyurethanes for controlled biodegradation

Today approximately 7,000 million metric tons (MMt) of plastic waste has been generated, and only a few percentage of that had been recycled, with the vast majority accumulating in landfills, or worse in the natural environments like our oceans. If we continue at this same rate, there will be 96 billion tons of plastic waste accumulated on this planet by 2050; this has to change. Our goal is to develop sustainable and biodegradable polyurethanes derived from algae biomass. We developed algae-based polyurethane foams for both athletic shoe midsoles and flip flop footbeds. These polyurethane foams are based on two synthetic routes, one using cellulosic hydrolysates to make polyol precursors in cyanobacteria and algae, and a second based on modification of fatty acids derived from photosynthetic algae. The two synthetic routes result in different polyols that we have used to formulate polyester polyurethanes with performance metrics that exceed those required for flip flops, and are close to specification for midsoles for shoes. Because we produce bio-based polyurethanes which have chemical bonds that occur in nature, the resulting polyurethanes are biodegradable, and we have identified that they degrade at approximately 3 - 4% a month, in the correct environment. Biodegradation of any polyurethane requires three things: polyurethanes that are suitable for enzymatic digestion, microorganisms capable of producing the degradation enzymes, and an environment that promotes microorganism growth (moisture and temperature). For an optimal product lifecycle we need to make sure that the foams we produce do not degrade while in use, but then degrade quickly once the end of life of the product has been reached. In order to “tune” biodegradation of our products, we will further evaluate the structural and materials properties of the polyurethane foams we are producing, identify the microorganisms that are degrading the foams, identify the enzymes these microorganisms utilize to facilitate degradation, and finally characterize the composition of the polyurethane breakdown products. If we can identify and understand these key components and processes, then we can control the life cycle of our products, such that we can optimize their performance during their useful life, and facilitate their end of life degradation. Under this award we specifically propose to: 1) Identify the set of microorganisms that can degrade our polyurethane foams when placed in four different environments; soil, ocean water, lagoon mud, and plant biomass compost. 2) Characterize the polyurethane breakdown products produced in each of these environments, 3) Identify and characterize the specific enzymes responsible for cleaving key bonds within the polyurethane foams.