Paper bags are greener than plastic
Life cycle assessments generally find that paper bags require more energy and water to produce than plastic bags and must be reused fewer times to break even, while both are outperformed environmentally by reusable bags made of durable material used many times.
What we know
Paper bags are widely assumed to be the more environmentally responsible choice compared to plastic, largely because paper is biodegradable and derived from a renewable resource, while plastic is petroleum-based and persists in the environment for a long time. Life cycle assessments, which measure environmental impact across the full production, use, and disposal chain, complicate this simple picture considerably.
A frequently cited 2011 study commissioned by the UK Environment Agency compared the life cycle greenhouse gas emissions of different bag types and found that a paper bag needed to be reused about three times, and a conventional cotton tote bag about 131 times, to match the lower per-use global warming potential of a single-use plastic HDPE bag, because paper and cotton production are more energy and water intensive than plastic bag production, and paper bags are typically heavier, increasing transportation-related emissions. Producing a paper bag also requires substantially more water than producing a plastic bag, and the pulping and bleaching processes used in paper manufacturing generate their own pollution byproducts, including chemical effluent that has historically been a concern for pulp mill wastewater.
Plastic bags, in exchange for their lower production footprint per bag, generate a different category of harm: because they are lightweight and can persist for a long time without breaking down, they are more prone to becoming litter, entering waterways, and contributing to ocean plastic pollution, including harm to marine wildlife that can ingest or become entangled in plastic debris. Paper bags degrade much faster in the environment and are less likely to persist in the same visible way, even though this benefit is less relevant if bags are disposed of properly in landfills or recycling rather than as litter in either case.
The conclusion most life cycle assessments converge on is that the single most impactful factor is not the bag material but the number of times a bag is reused. A reusable bag made from polypropylene, a strong lightweight plastic often used in supermarket reusable totes, typically needs to be reused only around 10 to 20 times to have a lower environmental footprint than continually using disposable paper or plastic bags, according to several national environmental agency assessments, including analyses referenced by Denmark's Ministry of Environment and Food in a widely cited 2018 lifecycle study.
That same Danish study also compared organic cotton bags specifically, finding they required an especially high number of reuses, in the thousands, to break even with a single-use plastic bag on climate impact, largely because organic cotton farming is markedly more land and water intensive than conventional cotton or synthetic fiber production, a distinction that matters for shoppers choosing between different styles of reusable bag rather than simply between paper, plastic, and reusable in general.
The common shorthand that paper is automatically greener than plastic oversimplifies a more complicated tradeoff between different environmental impact categories, greenhouse gas emissions, water use, eutrophication from pulp production, and persistent litter and marine plastic pollution, each of which paper and plastic bags affect differently. Policy responses in many jurisdictions have moved toward encouraging reusable bags broadly, rather than simply substituting one single-use material for another, reflecting this more nuanced life cycle evidence.
Common claims
- Paper bags are better for the environment than plasticMisleading - paper has higher carbon and energy footprint per use
- Paper bags biodegrade and are therefore sustainablePartially true - biodegrades faster but production impact is higher
- Reusable bags are the best optionTrue if used many times - requires 10-20+ uses to offset higher production impact
Evidence hierarchy
All sources
- Plastic, Paper or Cotton: Which Shopping Bag is Best?Columbia University State of the Planet · 2020
- Review of Life Cycle Assessments Comparing Paper and Plastic ProductsNCASI · 2020
- Life Cycle Assessment of Supermarket Carrier BagsUK Environment Agency · 2011
- Life Cycle Assessment of Grocery Carrier BagsDanish Ministry of Environment and Food · 2018