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A recent report from the Carbon Trust notes that there are "more carbon emissions from crisps (potato chips) than cement." Although it may be a surprising bit of news at first, it conceals the greater issue of scale. Undoubtedly though, someone is certain to rail against potato chips and argue that we don't need to worry about cement production when snack foods are the bigger problem. While the Carbon Trust's statement is factually correct from one perspective, as the famous saying goes, there are "Lies, damned lies, and statistics", so let's talk about numbers a bit.
First, let's take a look at the amount of CO2 produced for each item. Producing cement releases about an equivalent amount of CO2 (producing one ton of cement releases one ton of CO2), while producing potato chips releases about 2.3 times as much CO2 (producing one ton of potato chips releases 2.3 tons of CO2). What is key here is that the factor of CO2 produced is in relationship to the weight of the finished product. Cement is much denser and heavier than potato chips, so a sack of cement has a much, much higher carbon footprint than an equivalent volume of potato chips.
Secondly, let's consider the annual production of each item. A figure for yearly global production of potato chips wasn't readily available, but just looking at relatively recent US consumption, roughly 3 million tons of potato chips are produced annually, yielding about 7 million tons of CO2. However, US cement production is around 100 million tons per year, yeilding about 100 million tons of CO2.
Even though cement produces less CO2 per pound, cement production is still nearly 15 times more significant to US production of CO2. Although there is more CO2 per unit of potato chips, a lot more cement is produced, which helps make that the larger problem.
However, there's more to it than just that. Global cement production in 2000 was 1.56 billion tons. The US production is only about 6% of that total. On the other hand, the US is probably responsible for a higher percentage of total potato chip consumption, so the global figure for cement production is even more significant.
Big numbers and surprising ratios can catch our attention, but it's important to look at the overall picture. Although more CO2 per pound was released when the potato chips were made, a one pound bag of potato chips still represents less impact than an 80 pound sack of cement; the bags are far from equivalent to one another. And even though producing a pound of chips releases more CO2 than producing a pound of cement does, that doesn't make potato chips a greater environmental hazard than cement.
Thanks @MelStarrs
Image credit: CC-By-SA-2.5 by Paul Hurst
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written by Joshua Mitchell, April 10, 2010
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written by Simone, April 11, 2010
Chips are packaged in a way which is not volumetrically efficient whereas cement is (there is probably more air than solids in the typical chips packet). However chips are transported by truck to their destination. If we consider the amount of fuel burned doing this, it is likely that chips are possibly much worse than this article suggests.
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written by Alex Charlton, April 11, 2010
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written by Amy Thomson, April 11, 2010
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written by Carl Hage, April 11, 2010
There is a goof above-- I think the units for potato are probably pounds, not tons, so potato chip emissions would be 30,000 times less significant not 15.
I followed the links and found the measurement on potato chips (the only one in the "snacks" category). I was not able to use the database to find CO2 for cement-- good example of why database search is a poor (in this case unusable) user interface. The results also doesn't give much detail on the methodology or assumptions, but they supposedly use independent "experts".
What was more interesting was the link to the Pepsi page where they mention working with the Carbon Trust:
Working with Walkers since 2000, the Carbon Trust conducted an audit of our energy use, from field to shelf. As a result of this process, we were able both to work out our carbon footprint and to reduce our energy use per kilo by 32%.
Energy efficiency might be more important than just absolute pound-for-pound measurements. By performing these audits, companies see how to reduce emissions and often save money as well. The 32% reduction in footprint is significant.
Rather than comparing potato chips to cement (or was it really concrete), compare products that can be substituted, e.g. potato chips vs pretzels, concrete vs steel. A CO2/kg isn't the best measure to compare, it would be CO2 per amount required for a lightpole, building wall, etc.
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written by P Proefrock, April 11, 2010
Cement and concrete are not the same thing. Cement is one of the ingredients in concrete (along with water and aggregates, as well as additives which are used increasingly today). Cement is the most energy intensive part of concrete, and I was pretty certain that all the numbers I followed were for cement rather than for concrete.
I also think that having a base number of CO2 weight per unit weight of product is the best figure to have in order to do piece versus piece comparisons. That way, manufacturing efficiencies that reduce the weight of material in a finished product can more easily be compared.
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written by Temujin Kuechle, April 11, 2010
Cement/concrete usually lasts quite a long time after it has cured/becomes hard. Transportation costs aside, they are equally significant (maybe not important or needed in all situations) to us, although there are alternatives that might be better for us in the long run.
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written by ffarkle, April 12, 2010
Anything that deviates from a pre-industrial age carbon cycle has to go, right now.
Of course, we'll all have to learn how to ride horses again, and weave our own flax shirts and cotton breeches. But I guess there's enough old tires laying around that we'll never have to use shoe leather again.
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written by Louise Denny, April 12, 2010
I am shocked to see the massive figures that crisps produced, but I do agree that our snack foods can't possibly be doing as much harm to the environment as building marterials are.
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written by MikeB, April 12, 2010
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written by Knuckle Boom, April 13, 2010
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written by hydrophilia, April 20, 2010
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written by Mina, May 17, 2010
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Cement does not have a growth cycle to use up carbon and produce oxygen. It is probably a safe generalization that food production has less of a footprint than the creation of building materials that are not plant-based. (Except perhaps for the production of Peeps—I'm pretty sure they have little plant matter in them.)