Saturday, March 31, 2007

Carbon Footprint of a Bag of Potato Chips

To measure Walkers' carbon footprint, the Carbon Trust, on our behalf, has calculated the carbon footprint of a standard packet of Walkers Cheese & Onion Crisps.

The final carbon footprint calculation is 75g.

The flow-chart on this page shows exactly what percentage of our carbon footprint is expended at each stage:

1) 44%: Our raw materials: Potatoes, sunflowers and seasoning
2) 30%: Manufacture: Producing crisps from potatoes
3) 15%: Packaging our crisps
4) 9%: Distribution: Bringing our crisps to you
5) 2%: Disposal of the empty packs
I really like this idea of putting the carbon footprint on every day items, so you can get a feel of the embedded carbon in them.

I also like the breakdown in stages as it lets you know that the raw materials have the majority of the impact and therefore probably the best place to try and reduce emissions. I think many people would have thought that the manufacturing and distribution were the main culprits, and this lets you see that raw materials have an even greater impact than both of them combined.

The 75g number is ultimately the key value on the label, but without something to compare it to, it is not that interesting on its own. Hopefully in the future other potato chip manufacturers and food producers will also label their products so you can choose a low carbon product. Off hand, the only thing I can think of to compare it to is a gallon of gasoline which has around 9 kg of emissions, so one bag of chips is around 1/120 of that.

via Walkers via Food System Factoids


odograph said...

For what it's worth, 75g is (75 * 12/44) = 20 grams carbon

Given Diesel carbon content per gallon (link below): 2,778 grams

One "standard bag" of chips contains the energy equivalent of 0.007 gallons of diesel fuel.

Geez that seems low. If we knew the size or calories in that bag of chips we could calculate the fossil fuel to calorie efficiency as well.

Fat Knowledge said...


Thanks for the comment.

That .007 number is right in line with my estimate of 1/120 of a gallon of gasoline.

I agree, it would be interesting to know what the ratio of fossil fuel energy to edible energy. I also think we would need to know where the energy came from, as diesel fuel, natural gas and coal all have differing carbon intensities.

Actually carbontrust would have to know those number in order to make the label. Too bad they don't make that information public as well.

odograph said...

1/120 = 0.008 ;-)

You got there first.

It suddenly occurred to me that we can translate that 0.007 gallons back into calories, using 32000 as the rough measure of calories in a gallon of diesel.

224 calories.

It's actually hard to think that their reference bag would have fewer than that!

So for something that I actually thought was one of the worst cases (fried food, trucked around in bags of mostly air), we may be 1:1 or better on fuel inputs.


Fat Knowledge said...

I am not quite sure how many calories are in this bag of chips, but yeah more than 225 seems quite likely.

I am also curious if it would use less or more energy/co2 emissions if you bought raw potatoes and cooked them yourself vs. buying them in a bag. I would think that cooking all the potatoes in a large plant would be more efficient than everyone cooking them on their stove top, but I don't know for sure.

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