Algal biopolymers as sustainable resources for a net-zero carbon bioeconomy

Problem statement

Total plastic production has exceeded 8300 million tonnes (MT) since 1950s, 380 MT in 2015 alone, and 79% of which is already in the natural environment especially oceans or landfill. The mismanaged plastic wastes, including emergent pollutants such as micro-, and nano-plastics are demonstrated to be present in every conceivable environment affecting biodiversity, economic and human well-being worldwide (Lau et al., 2020). Therefore, alternative renewable resources are required for sustainable polymer production.

Executive summary

The era for eco-friendly polymers was ushered by the marine plastic menace and with the discovery of emerging pollutants such as micro and nano-plastics and plastic leachates from fossil fuel-based polymers. It is important to investigate algae-derived natural, carbon-neutral polysaccharides and polyesters, including their structure, biosynthetic mechanisms, biopolymer and biocomposite production processes, and polymer biodegradability. Accelerated research is proposed in this promising area to address the need for eco-friendly polymers and to increase the cost-effectiveness of algal biorefineries by coupling biofuel, high-value products and biopolymer production using waste and wastewater-grown algal biomass. Such a strategy improves overall sustainability by lowering costs and carbon emissions in algal biorefineries, eventually contributing to circular, carbon net-zero economies.

Technology description

Algae are found everywhere from freshwater springs to lichens to marine environments, exhibiting autotrophic, mixotrophic and heterotrophic lifestyles. In the laboratory or large scale cultivation of algae, the growth can be regulated in favor of production of large amounts of polysaccharides, hydrocarbons and lipids by nutrient starvation or other cellular stress (Kakarla et al., 2018).
Productivity of microalgae is dependent on several factors such as light, temperature, availability and type of energy and nutrients, presence of predators, culture density, species cultivated, and other culture conditions such as pH and salinity. Any large-scale synthesis of biopolymers from microalgae requires devising specific strategies considering the above factors. Nutrient source, extraction process and energy source are the dominant input costs for biopolymer production from microalgae.
Microalgae are used as both fillers and as reinforcing fibers in composites. The blends prepared with microalgae replace certain amount of petroleum plastic, thus decreasing the price and the carbon footprint of polymer (Bulota & Budtova, 2015; Mihranyan, 2011). Chlorella was found to be suitable filler for PVC as it increases the volume of the composite material, decreases density and also contributes to tensile strength.
Sea algal fibres can be utilised for the production of thermoplastic biodegradable polymers. The increase in fibre concentration results in high elastic modulus but low mechanical strength (Bulota & Budtova, 2015).
Alginate, carrageenan, agar, starch, pectin and cellulose are the major film-forming materials among the polysaccharides (Mohamed et al., 2020).

Market deployment considerations

Environmental considerations