What’s the Bag Deal?

Play_Episode05A couple argues over which is the best bag for grocery shopping: paper or plastic? Both appear to have their advantages and disadvantages, so what are they to do? Sensing a learning opportunity, the Green Ninja appears with a simple solution – a reusable bag! But is it really that simple?

Let’s dig into the issue of bags more closely.
Below is a comparison of the carbon footprint of five different types of grocery bags. In this case, the carbon footprint comes from the energy required to make these different bags. As we can see, not all bags are created equal!


Bag Type HDPE Paper LDPE Non-Woven PP Cotton
Description Conventional plastic bag used at grocery stores. Brown, boxy-looking. Grocery stores use this when you when you ask for paper. Thick shiny bag that is sold as a reusable bag. A.K.A ‘bag for life’ Thick, washable bag that looks like canvas from afar. Very common to see. Fabric bag, less structured than other bags. Usually has large handles.
Carbon Footprint 3.8lbs 12.2 lbs
(3x HDPE)
15.3 lbs
(4x HDPE)
47.4 lbs
(13x HDPE)
598.6 lbs
(158x HDPE)


The chart above is adapted from Edwards and Meyhoff’s life cycle assessment of grocery bags1

But wait a second, isn’t the Green Ninja recommending the high carbon footprint bags? Looking at the chart, reusable bags clearly have a higher carbon footprint than conventional bags.

As it turns out, the carbon footprint of grocery bags directly depends on the extraction of raw materials and the production of the bags. Although more energy goes into making reusable bags, we would expect that they could be used many, many times.

Let’s look at an example.
A family of five goes grocery shopping every week, and they use 3 bags to hold their groceries. We now compare the carbon footprint of using shopping bags for this family, using plastic, paper and reusable bags, over a three-year period.

Bag Type HDPE Paper LDPE Non-Woven PP Cotton
Carbon Footprint after 3 years 1,769.0 lbs 5,700.2 lbs 45.8 lbs 142.3 lbs 1197.3* lbs*2 bags used because of their larger volume2

So, now the Green Ninja’s advice makes more sense. Different bags are going to have different carbon footprints, the most important variable is the number of times that we reuse those bags. So, the best choice is to use the same reusable bags for a long time, and3 occasionally wash them to keep them clean.

Carbon talk aside, what are some other reasons for choosing reusable bags?

Plastic bags harm marine life.


Let’s imagine a plastic bag floating in the ocean and then a squid propelling in the ocean. They look similar. Turtles and whales seem to agree, which is why they often eat plastic bags mistakenly thinking that they are delicious squid4. This is certainly not good for marine life5. An estimated 100,000 marine animals die each year because of plastic bag waste.

A lot of trees are cut down to make paper bags.


Although paper bags are biodegradable, their usage is questionable because so many trees are cut down just to make them. An estimated 14 million trees are cut down each year just to keep up with paper bag demand in the United States6.

Although people mention that they reuse their plastic bags for trashcan liners (or other uses), many of our bags still end up in the ocean and harm wildlife. Today one can purchase biodegradable and compostable bags that work great for many uses, but fully break down in the land and ocean. Our friends at World Centric have a great selection here.


1. Edwards, C., Meyhoff Fry, J. (2011). Life cycle assessment of super market carrier bags: a review of the bags available in 2006. Environment Agency, 12-33.

2. Edwards, C., Meyhoff Fry, J. (2011). Life cycle assessment of super market carrier bags: a review of the bags available in 2006. Environment Agency, 12-33.

3. Gerba, C.P., Williams, D., Sinclair, R.G. (2010). Assessment of the potential for cross contamination of food products by reusable shopping bags. 13-15.

4. Marine Debris Impacts. EPA. (2012). Retrieved from https://water.epa.gov/type/oceb/marinedebris/

5. Leatherback Sea Turtle. DEEP. (1999). Retrieved from https://www.ct.gov/deep/cwp/view.asp?a=2723&q=326028&depNav_GID=1655

6. Bags by the Numbers. WM. (n.d.) Retrieved from https://www.wmnorthwest.com/guidelines/plasticvspaper


Directed and Produced by: Michelle Ikemoto

Host: Alejandro Garcia

Supported by: San Mateo County, Environmental Health (www.smchealth.org/bagban)

Animation: Michelle Ikemoto, Danny Men, Miyuki Richardson, Aaron Soon, Jason Wong, Alex Yip

Backgrounds: Ishmael Hoover

Show Opening: Mark Wanninger

Green Ninja Theme Music: Eli Rosen

Voice Actors: Ovan Chan and Jessica Ellithorpe.

Special Thanks to our Kickstarter Supporters: Andy Griffiths, Clare Cordero, Edward Thometz, Karl Braganza, Robb Drury, Shaun Tanner, Steve McCann, Susan Pitt, Susan Tenney, Tracy DeLuca, W. Stephen Sullins, Phuong-Mai Bui-Quang, Ty Joseph, and Vanessa Warheit.


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