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Study says production of climate-neutral plastics is economically feasible

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New holistic concept for production and disposal of plastics results in net-zero GHG emissions

It is possible to produce plastics both economically and in a climate-neutral manner by using an innovative combination of three existing technologies: recycling, biomass utilisation and carbon capture and utilisation (CCU). This has now been demonstrated in a new study by an international team of researchers from the RWTH Aachen University, the Swiss Federal Institute of Technology (ETH) Zurich and the University of California Santa Barbara. According to the study, a new holistic model for plastics production and disposal would allow plastics to be produced without causing greenhouse gas (GHG) emissions, or, as the scientists put it, with so-called net zero GHG emissions.

Net zero means that all GHGs emitted during production are removed from the atmosphere again. As Raoul Meys from the Chair of Technical Thermodynamics at RWTH Aachen University and Professor André Bardow from the Chair of Energy and Process Systems Engineering at ETH Zurich and formerly RWTH explain, this then results in a zero-carbon footprint. The results of their study show that net zero emissions are possible for plastics. 

Decarbonise, from the extraction of oil to the production of plastics

Specifically, the researchers' concept includes so-called decarbonisation of the energy sources used in the plastics supply chain, in other words switching to processes that release the lowest possible amounts of carbon dioxide (CO2) at all stages of the process, from the extraction of the oil through to the production of the plastics. The scientists' strategy is based on replacing the fossil-based carbon inputs in the plastics production, in other words the oil, by using the closed-loop technologies mentioned above, namely chemical and mechanical recycling, the use of biomass, and carbon capture and utilisation.

The chemical and mechanical recycling of plastic waste allows primary materials to be replaced, thus conserving resources. So-called biobased plastics can be produced from renewable raw materials such as maize, starch or sugar. However, such production competes with the production of food, so the focus is increasingly on the production of bioplastics based on waste material, for example from farming. 

Carbon capture and utilisation (CCU) is also referred to as CO2 recycling. In this process, the carbon dioxide is removed from exhaust gases and then reused for other processes, such as energy-related or chemical processes. Not only does this reuse of the captured carbon make an important contribution to reducing carbon emissions: it can also significantly increase the productivity of industrial processes.

Use as high a proportion of recycled plastics as possible

According to the researchers, one result of their study is that the key to the economic production of climate-neutral plastics lies in using the highest possible fraction of recycled plastics — supplemented by the other production routes mentioned above. The authors of the study emphasise that such production is in line with the principle of a circular economy. They say that an optimal combination of the three production paths can reduce the energy demand of climate-neutral plastics by 34 to 53 per cent, measured against an alternative production route, namely the current process for producing plastics from fossil-based raw materials supplemented by extensive carbon capture and storage (CCS), particularly in waste incineration plants, where the plastic products are burnt at the end of their life cycle.

The researchers estimate the costs of the newly proposed manufacturing route would be of the same order of magnitude as for the alternative fossil-based production scenario. But that's not all: the scientists predict that under favourable conditions, the costs of plastics production worldwide could even be reduced by 288 billion US dollars a year in 2050 compared to the alternative scenario. For this to happen, however, biomass, CO2 and renewable electricity would have to be available at low cost. In addition, the cost-cutting scenario includes making the extraction and supply of crude oil more expensive and introducing investment incentives for recycling. 

Don’t adopt a stand-alone approach to production 

The scientists involved in the study emphasise that their model makes it possible to economically produce plastics that have net zero greenhouse gas emissions over their entire life cycle. They therefore appeal to politicians to promote the path to climate-neutral plastics by providing incentives for more plastics recycling and increased use of biomass and CCU. “We should not consider the various steps in the production of plastics separately, because there is enormous potential to be gained when they are combined skilfully,” concludes Professor Bardow of ETH.

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