New technology allows waste carbon dioxide to be repurposed into a sustainable feedstock for plastic production. Here we take a look at how viable this method is and the possible consequences for the environment.

Plastic production and consumption are two of the most significant environmental issues facing our planet today, with global plastic production estimated at 390.7 million metric tonnes in 2021 alone. Plastic, including polyurethane, is integral to many areas of industry, including construction, automotive, chemicals and upholstery.

Polyurethane is a type of polymer (a long chain of functionalized carbon) with a wide range of properties, from strong and rigid to flexible and brittle. While not plastic in the traditional sense, polyurethane’s ability to be flexible and hard, along with other physical properties, highly resemble those of more common plastics.

The production of traditional polyurethane relies heavily on fossil fuel-derived feedstocks. This reliance leads to increased carbon dioxide (CO2) and other toxic gases being released during production, contributing further to the climate impact of plastics; 2019 saw 1.8 billion tonnes of greenhouse gas emissions from global plastic production.

In recent years, there have been significant strides in using waste CO2 from industry as a partial feedstock for polyurethane production instead of petrochemical derivatives, with the hope that this will reduce the CO2 emissions associated with its production.

Production of CO2-based polymers

Traditional polyurethane is formed through polymerisation reactions of diisocyanates and polyols — a type of polymer that contains alcohol groups (OH). Polyols are typically formed from the polymerisation of epoxides (carbon-oxygen ring structure), which are obtained from crude oil using energy-intensive processes, such as cracking, that release harmful materials. As a result, traditional polyurethane production is costly for both the pocket and the environment.

Instead of using purely fossil fuel-derived epoxide to produce the polymer, CO2 can be added during the reaction and incorporated into the backbone of the polyol, thus acting as a co-polymer.

This reaction occurs in the presence of a catalyst (a substance that speeds up a reaction), typically metal complexes or organic bases. The reaction leads to the formation of cyclic carbonates, which undergo further polymerisation, resulting in the formation of polymers.

Environmental Impact and Climate Benefits

The CO2 used in this process is often obtained from industrial emissions or captured directly from the atmosphere. This process, known as carbon capture and utilisation (CCU), has gained much momentum in recent years. By combining the reduction of fossil fuels with the removal of toxic waste gases from the atmosphere, there is vast potential to reduce the negative environmental impact of traditional polyurethane production.

Life cycle assessments indicate that incorporating CO2 can reduce greenhouse gas emissions by up to 19% and save 16% in fossil fuels, a significant amount considering how much is produced annually.

These polymers can also be used to manufacture insulation for homes, a material that will be needed in abundance to create the energy-efficient housing required in the future. An interesting added benefit of incorporating the CO2 is the increased fire resistance of the material. This is because having CO2 already present in the material slows the burning process.

Companies such as Econic Technologies in the UK, Covestro in Germany, and Aramco in Saudi Arabia have already developed catalysts to assist in the production of these CO2-based polymers. These polymers are used to produce everyday items such as foam for mattresses, the soles of trainers and car interiors.

Challenges and future outlook

While the benefits of using CO2 feedstocks are clear, there are inevitably still challenges to be overcome. High production costs stemming from the need for specialised catalysts, limited scalability and complex synthesis processes are significant obstacles.

Another challenge is achieving desired material properties, such as durability and strength, while maintaining cost-effectiveness. Compatibility with existing manufacturing processes and infrastructure is crucial for widespread adoption; this includes retrofitting production plants to fit the new technology and obtaining new reactor systems.

Additionally, it is essential to ensure the benefits of CO2-based polymers are not outweighed by concerns over biodegradability or end-of-life management. It is not enough to assume that this will tackle all the problems we have with plastic consumption; however, it should be noted that in combination with techniques such as CCU, this is a step in the right direction for the industry.