Most compostable bags labelled as eco-friendly in fact have close to double the global warming impact of traditional plastic and paper, highlighting the scale of greenwashing in the sustainable packaging market.
The findings, from research conducted by packaging platform Sourceful, including contributions from the Sustainable Materials Innovation Hub at the University of Manchester into the systemic considerations of home composting, analysed 20 materials representing three-quarters of the global bioplastics market.
Sourceful examined the Global Warming Potential – all the greenhouse gases that contribute to global warming – of each product’s lifecycle, from production through to disposal.
The materials analysed spanned five groups: compostables, virgin fossil (traditional plastic), recycled plastic, paper, and bio-based non-compostable packaging. Compostable packaging on average generated 228 grams of CO2 equivalent per bag, compared with 118 grams on average for virgin plastics – almost double.
When expanded to other impact categories such as water-use and land-use, the gap widens to approximately 2.5 times worse than traditional virgin plastic.
The findings come only two weeks after the UN’s environment agency warned that progress towards decarbonisation goals has been “woefully inadequate,” leaving us with “no credible pathway” to restricting global warming to levels that will successfully limit the worst impacts of the climate crisis.
The compostables market is growing rapidly – set to triple between 2021 and 2026 – but in the UK today there is a lack of composting infrastructure, with no public collection schemes for compostable packaging and few industrial composting facilities. This means compostables are placed in general waste, with 54% landfilled, 43% incinerated and only 3% fully composted.
At landfill, the climate impact of compostables is 12 times higher than when properly composted due to the release of methane, which is 34 times more potent than CO2.
Sourceful’s CEO and co-founder, Wing Chan, said: “Compostable bags and films have been marketed as a green replacement to fossil-fuel plastic by virtue of being able to compost harm-free. Research is showing that the conditions for this composting don’t exist in practical terms, and the carbon footprint of compostable bags is significantly worse than plastic, recycled plastic or paper options as a result.
“The increased carbon footprint of compostable bags and films contributes to global warming rather than slowing it. The practical reality of compostables does not reflect the narrative used to market them. We recommend avoiding and looking to switch out where possible in your supply chain.”
