A study published in Nature Food finds that diverting food waste from US landfills could reduce climate impacts by 89% to 99% compared with landfilling. But the researchers warn that microplastics can remain in compost and could contaminate US agricultural soils at a rate of up to 20,000 tonnes a year.
The findings show that food-waste policy has two linked environmental challenges: reducing emissions and nutrient pollution while preventing plastic from entering compost and other reuse systems. The researchers say plastic contamination should be considered when food-waste diversion policies are designed.
At a glance:
- About one-third of food produced worldwide is wasted each year, according to UN data.
- In the US, 40% of food waste goes to landfill, producing 30 million metric tonnes of carbon dioxide equivalent annually.
- Even plastic-separation technology that is 99% efficient could leave food-waste diversion increasing microplastic pollution in soil by an order of magnitude.
- Vermont’s Universal Recycling Law has required food scraps to be diverted from landfill for households since 2020.
| Landfilling food waste | Diverting food waste from landfill | |
|---|---|---|
| Climate impact | Higher climate impact in the study’s modelling. | Reduced climate impacts by 89% to 99%. |
| Nutrient pollution | The study compared landfill impacts with alternatives that could reduce eutrophication. | Could reduce nutrient pollution in water bodies, including pollution linked to algal blooms. |
| Plastic contamination | Does not create the same compost pathway described by the researchers. | Microplastics can persist in compost and reach agricultural soils. |
What the researchers studied
Researchers based at the University of Vermont used life-cycle analysis modelling to compare food-waste management scenarios. The analysis considered climate impacts, nutrient pollution and plastic contamination rather than measuring only greenhouse-gas emissions.
Related coverage: Adana farmers face microplastics and smoke from imported plastic waste.
The researchers said no previous study had examined the plastic-pollution footprint of different food-waste management strategies at national scale. Lead author Kate Porterfield described the approach as similar to calculating the carbon footprint of a product or process by adding impacts across each stage of management.
Why packaging changes the calculation
A common approach uses a mechanical depacker: packaging is separated from food, with the packaging sent to landfill and the food sent for uses such as composting or anaerobic digestion. The study found that this pathway can still carry a substantial microplastic risk.
The researchers said food often remains in packaging because it spoils before reaching consumers. Even with 99% efficient separation technology, diverting food waste from landfill could increase microplastic pollution in soil by an order of magnitude, because neither people nor machines separate every item perfectly.
What this means for food-waste rules
Vermont’s Universal Recycling Law, fully effective from 2020, requires food waste to be diverted from landfill. It applies to all households and bans food scraps from household bins. The study’s authors said their results can help evaluate whether similar rules are scaled up nationwide.
The researchers called for plastics to receive more attention from the beginning of policy design. Co-author Eric Roy said systems need to make separation easy and reduce “wish recycling”, in which people place non-recyclable items in recycling bins hoping they can be processed.
The packaging tradeoff
The study’s findings do not resolve the tension between reducing packaging and preventing food waste. Phil Holtam of Sussex Surplus said plastic packaging can extend the shelf life of fresh produce, particularly for smallholder farms, making it a tradeoff rather than simply an unnecessary material.
Max La Manna said expectations that produce should look perfect can also contribute to waste, including the rejection of misshapen or cosmetically imperfect food. Roy added that schools and other institutions may face food-safety rules that make it harder to move away from highly packaged foods.
Questions readers ask
Does diverting food waste from landfill always reduce pollution?
The study found major climate benefits and possible reductions in nutrient pollution, but it also found a risk of microplastic pollution whenever food waste is diverted, including through composting.
What should households do with questionable items?
Roy advised making every effort to separate materials, buying in bulk where possible and, if an item is not suitable for recycling, putting it in the landfill stream rather than “wish recycling” it.
Why not eliminate plastic packaging altogether?
The source describes packaging as potentially important for extending the shelf life of fresh produce, so reducing food waste and reducing plastic use can involve competing goals.
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