Bag Footprint Calculator

The choice between "paper or plastic" is more complex than it seems. Each type of shopping bag has its own environmental footprint, primarily related to the energy and resources used in its production and its end-of-life impact. This calculator focuses on the carbon footprint of production, which is a major component of a bag's overall environmental cost.

The Surprising Truth About Reusable Bags

While intuitively better, reusable bags, especially those made of cotton, have a significantly higher production footprint than single-use bags. A conventional cotton tote requires a large amount of water and energy to grow the cotton and manufacture the bag.

The key to making reusable bags the environmentally superior choice is in the name: reuse. You must use them many, many times to offset their initial high production cost.

Understanding the "Break-Even" Point

The "break-even" point is the number of times you must use a reusable bag for its carbon footprint per use to become lower than that of a single-use bag.

• vs. Plastic Bags: Studies show a cotton bag needs to be used around 131 times to have a lower global warming potential than a standard HDPE (plastic) bag that is used once.
• vs. Paper Bags: A paper bag has a higher production footprint than a plastic bag. Therefore, a cotton bag needs to be used fewer times, around 43 times, to break even with a paper bag.

What About Other Factors?

This calculator focuses on the carbon footprint of production. Other important environmental factors include:

• Water Usage: Cotton cultivation is very water-intensive.
• Pollution: Plastic bags are a major source of litter and harm to wildlife, especially in marine environments.
• Recyclability: While paper bags are more widely recyclable than plastic bags, the recycling process itself requires energy and resources. Reusable bags are rarely recycled.
• End-of-Life: Paper biodegrades relatively quickly, while plastic can persist in the environment for hundreds of years.

Conclusion

There is no perfect choice. However, the data strongly suggests that the most sustainable option is a reusable bag that you commit to using hundreds of times. If you must use a single-use bag, reusing it as a trash can liner or for other purposes helps to lower its overall impact.