One of the major environmental issues facing the planet today is the rising levels of plastic consumption and waste. According to a recent OECD study, the world produced 460 million tonnes (Mt) of plastics in 2019 and consumption will continue to rise despite an expected increase in recycling technologies deployment.
As carbon dioxide - CO2 - emissions also soar, the emerging carbon capture and utilisation industry proposes a solution for both issues: creating lower-carbon, degradable polymers using CO2 emissions as the feedstock. In a recent report entitled "Carbon Dioxide (CO2) Utilization 2022-2042: Technologies, Market Forecasts, and Players”, IDTechEx explores the potential of a circular carbon economy.
In the report, three major pathways to convert CO2 into polymers are discussed, namely electrochemistry, biological conversion, and thermocatalysis, with thermocatalysis as currently the most mature. This technology enables CO2 to either be utilised directly to create CO2-based polymers, most notably biodegradable linear-chain polycarbonates, or indirectly, through the production of chemical precursors - building blocks such as methanol, ethanol, acrylate derivatives, or mono-ethylene glycol - for polymerisation reactions.
LPCs made from CO2 include polypropylene carbonate, polyethylene carbonate, and polyurethanes.
The report notes that PUR is especially a promising market for CO2-based polymers, with applications in electronics, mulch films, foams, and in the biomedical and healthcare sectors. Captured CO2 can be incorporated into polyols, one of the main components in PUR. CO2-derived polyols - alcohols with two or more reactive hydroxyl groups per molecule - are made by combining CO2 with cyclic ethers (oxygen-containing, ring-like molecules called epoxides). The polyol is then combined with an isocyanate component to make PUR.
A number of companies, including Econic in the UK, Covestro in Germany, and the US-based Aramco Performance Materials (with intellectual property acquired from Novomer), have developed novel catalysts to facilitate CO2-based polyol manufacturing. Fossil inputs are still necessary through this thermochemical pathway, but manufacturers can replace part of it with waste CO2, potentially saving on raw material costs.
Chemical precursors for CO2-based polymers may also be obtained through electrochemistry or microbial synthesis, although these technologies are still mainly emergent. Of the two, the technology making use of biological pathways is the more mature, having reached the early-commercialization stage. Recent advances in genetic engineering and process optimisation have led to the use of chemoautotrophic microorganisms in synthetic biological routes to convert CO2 into chemicals, fuels, and even proteins.
Unlike thermochemical synthesis, these biological pathways generally use conditions approaching ambient temperature and pressure, with the potential to be less energy-intensive and costly at scale. A case in point is the California-based start-up Newlight, a company that is bringing into market a direct biological route to polymers, where its microbe turns captured CO2, air, and methane into polyhydroxybutyrate (PHB), an enzymatically degradable polymer.