Biodegradable bio-based plastics toward climate change mitigation

World society relies quite strongly on the use of fossil-based conventional plastics. Low cost and versatility paved the way for a wide range of applications. The most used plastics in daily life have been polyethylene (PE, as HDPE and LDPE), polypropylene (PP), polystyrene (PS), poly (ethylene terephthalate) (PET), and poly (vinyl chloride) (PVC), which, despite advances in processing and manufacturing, generate two major problems: the first one concerns the use of non-renewable resources to obtain the raw materials, and the second one is related with the large amount of waste generated since less than 10% of plastics are recycled today. As the greatest environmental impacts of fossil-based plastics are focused on the phases of obtaining the raw materials and disposal, as well as microplastics, the use of renewable, biodegradable bio-based plastics brings, as a gain for the environment and the whole society, the reduction of the volume of the plastic waste present, coupled with a reduction in resource consumption. Despite the great contribution that bio-based plastics can make to the environment since they are obtained from renewable biological sources and can be biodegradable, there are certain limitations, like the unavailability of biomass, difficulties in scale-up, and high economic costs, which still need to be overcome. A common raw material is starch, which is hydrolyzed to sugar and fermented, e.g., to lactic acid, to make polylactic acid (PLA). Other common biopolymers are thermoplastic starch (TPS) and polyhydroxybutyrate (PHB). Microalgae and seaweed, as a source of biopolymers, can represent an alternative due to their high yields and ability to grow in a wide range of environments. Also, microalgae and seaweed are economical and developments in this field of research have shown to be increasingly promising. Although algae-based plastics are at a very early stage of development, once they will have been commercialized, they are likely to find applications in a wide industrial range, such as food packaging and medicine storage. Another emerging raw material for bioplastics is methane, for which different sources exist, mainly biogas and synthesis gas from biomass gasification. Methane from natural gas is already used to produce ethylene and propylene in thermocatalytic processes, and (preferably biobased) methane can also be converted by methanotrophic bacteria, to yield, e.g., biodegradable materials like PHB. Bio-based polymers are a more eco-friendly choice over their fossil, persistent counterparts, as they can be made from renewable carbon sources and may contribute to climate change mitigation. Bioplastics might be an alternative to conventional fossil-based plastics, particularly when they are recycled.