Plastic alternatives worse for greenhouse gas emissions in majority of cases

Substituting plastics with alternative materials can result in increased greenhouse gas (GHG) emissions, according to new research led by Sheffield University.


The research, in collaboration with Cambridge University and the KTH Royal Institute of Technology, measured the emissions associated with plastic products in comparison with ‘greener’ alternative materials. 

The study analysed plastics and their replacements across various applications including packaging, construction, automotive, textiles and consumer durables, as these sectors collectively represent a significant portion of global plastic usage. 

For 15 out of 16 of the applications examined, researchers found that the plastic products resulted in lower GHG emissions compared to their alternatives. The reduction in emissions spanned from 10 per cent to as high as 90 per cent across the product life cycle. 

The researchers used life cycle assessment (LCA) to analyse the environmental impact of the different materials over the course of their life cycles.  

Even when focusing solely on direct life-cycle emissions, researchers found that plastics were better in nine out of 14 applications. Factors such as lower energy intensity during production and the weight efficiency of plastics, for instance, mean they have a reduced environmental footprint compared to alternatives like glass or metal. 

Plastics were also found to have lesser environmental impact in upstream processes, including production and transport, in 10 out of 16 applications. Researchers found the advantage stems from the lower energy intensity and lighter weight of plastic, highlighting the efficiency of plastic materials in mitigating emissions, according to the study. 

In a statement, Dr Fanran Meng, assistant professor in Sustainable Chemical Engineering at Sheffield University, said: “Not all alternative or recycled products are better for the environment than the products they replace. Environmental policymaking needs life cycle assessment guided decision-making to make sure that GHG emissions are not unintentionally increased through a shift to more emission-intensive alternative materials.  

“Demand reduction, efficiency optimisation, lifetime extension and reuse/recycling are win–win strategies to reduce emissions effectively. Solely focusing on switching to alternative materials is not.” 

Researchers also revealed the complexity of indirect impacts from background systems surrounding plastics. In scenarios like insulation and hybrid vehicle fuel tanks, researchers found that the indirect impacts overshadowed the direct emissions of plastics. 

Additionally, plastic food packaging was found to preserve the quality of food across a range of categories, helping to prevent food spoilage and the GHG emissions that this creates. As such, researchers highlighted the ‘unmeasured’ environmental benefits of plastic food packaging in comparison to alternative materials.  

Findings from the research suggest that optimising plastic use, extending product lifetimes, boosting recycling rates and enhancing waste collection systems may offer more effective strategies for reducing emissions associated with plastic products. 

“I would also like to stress the importance of not overlooking the impact of plastics on marine ecosystems and potential impacts on human and ecological health,” said Dr Meng. “We need to consider all of these impacts when choosing which materials to use in products to ensure we are using the right materials for the right purpose and to help us develop a sustainable plastics sector.” 

The researchers said that future modelling could be expanded to include reusable bioplastics, compostable and biodegradable alternatives, which were excluded from this study due to small market values and a lack of reliable data about reuse. 

The study, published in Environmental Science & Technology, can be read in full here.