Dr Hydra Rodrigues, technology analyst at IDTechEx, analyses the opportunities and challenges involved with using captured CO2 emissions as feedstock in the production of polymers, which the organisation suggests could facilitate a circular carbon economy.
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, we 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 utilization (CCU) industry proposes a solution for both issues: creating lower-carbon, degradable polymers using CO2 emissions as the feedstock. The recent IDTechEx report ”Carbon Dioxide (CO2) Utilization 2022-2042: Technologies, Market Forecasts, and Players” analyzes the opportunities and challenges of creating this proposed circular carbon economy.
How to make polymers from CO2?
There are at least three major pathways to convert CO2 into polymers: electrochemistry, biological conversion, and thermocatalysis. The latter is the most mature CO2 utilization technology, where CO2 can either be utilized directly to yield CO2-based polymers, most notably biodegradable linear-chain polycarbonates (LPCs), or indirectly, through the production of chemical precursors (building blocks such as methanol, ethanol, acrylate derivatives, or mono-ethylene glycol [MEG]) for polymerization reactions.
LPCs made from CO2 include polypropylene carbonate (PPC), polyethylene carbonate (PEC), and polyurethanes (PUR). PUR is a major market for CO2-based polymers, with applications in electronics, mulch films, foams, and in the biomedical and healthcare sectors. CO2 can comprise up to 50% (in weight) of a polyol, 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.
Companies such as Econic, Covestro, and 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.
In the realm of emerging technologies, chemical precursors for CO2-based polymers can be obtained through electrochemistry or microbial synthesis. Although electrochemical conversion of CO2 into chemicals is at an earlier stage of development, biological pathways are more mature, having reached the early-commercialization stage. Recent advances in genetic engineering and process optimization 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. Notably, the California-based start-up Newlight 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.
Currently, the scale of CO2-based polymer manufacturing is still minor compared to the incumbent petrochemical industry, but there are already successful commercial examples. One of the largest volumes available is aromatic polycarbonates (PC) made from CO2, being developed by Asahi Kasei in Taiwan since 2012.
More recently, the US-based company LanzaTech has successfully established partnerships with major brands such as Unilever, L’Oréal, On, Danone, Zara, and Lulumelon to use microbes to convert captured carbon emissions from industrial processes into polymer precursors - ethanol and MEG - for manufacturing of packaging items, shoes, and textiles.
Although the idea of reusing waste greenhouse gases as raw material seems like a win-win proposition, many viability questions arise for each CO2 utilization pathway. Will it truly lead to emission reductions? What are the financial and practical barriers to its commercialization? Can it scale to address climate change meaningfully?
These are some of the tough questions IDTechEx addressed in the latest report ”Carbon Dioxide (CO2) Utilization 2022-2042: Technologies, Market Forecasts, and Players”, focusing not only on CO2 use in the polymer and chemical markets, but also in enhanced oil recovery, building materials, fuels, and biological yield-boosting.
The bottom line
Not all CO2 utilization pathways are equally beneficial to climate goals and not all will be economically scalable. Scarce resources that have alternative uses must be allocated where they are most likely to generate economic value and climate change mitigation.
As the world’s thirst for plastics does not seem to fade, a circular carbon economy may help maintain people’s lifestyles by fostering a petrochemical industry that sees waste CO2 as a viable feedstock.