Deep Thought and Tomato Ketchup

When I was studying Life Cycle Assessment, the standard textbook was “the Hitch Hiker’s Guide to LCA”. The opening pages are the paragraphs from Douglas Adam’s Hitch Hiker’s Guide to the Galaxy in which Loonquawl and Phoug receive the Answer to the ‘Great Question Of Life, The Universe and Everything’ from the computer Deep Thought. After 7.5 million years work, the answer is 42. “I checked it very thoroughly,’ said the computer, ‘and that quite definitely is the answer. I think the problem, to be quite honest with you, is that you’ve never actually known what the question is.’

Life Cycle Assessment (LCA) is really the only game in town when it comes to doing a detailed assessment of the environmental impacts of a product or service. There are regular academic advances in methods and the capacity for improvement and self-correction, as described in academic journals such as The Journal of Cleaner Production and The International Journal of Life Cycle Assessment. There is also a suite of EN ISO standards governing its use as a technique in more applied settings, so providing the ideal balance of real life application and scientific rigour.

And yet, as Deep Thought illustrates, there is a real risk that LCA experts spend a long time answering meaningless questions. I was reminded of this recently when I saw a journal paper on the environmental impact of tomato ketchup. It’s available here. The authors calculated the climate change impacts of tomato ketchup in both glass and plastic bottles, and found that the CO2e emissions from ketchup consumption by the average Austrian citizen were between 5.66 and 9.16kg CO2e/year. This is a very small number; it’s between 0.07% and 0.11% of an individual’s emissions in Austria.

Deep Thought would not have been impressed.

Other ketchup brands are also available…

But there’s a twist in this tale. When you get to the end of a bottle of tomato ketchup, there are two types of people in the world; those that give up and chuck the bottle without scraping the last bit out, and those that feel guilty about chucking it out so get a spoon out of the drawer and spend some time faffing about. You may even be unfortunate enough to live with one of those people that commit the cardinal sin of starting a new bottle because they can’t be bothered to empty the old one, but still putting the old one back on the shelf. Grrr…

The authors are clearly well aware of the domestic angst caused by ketchup, so they shook, squeezed and swivelled ketchup bottles and left them upside down to see how much was usually left in the container at the end. Bottles were even emptied with a ‘dedicated ketchup spoon’ (whatever that is…). The authors then calculated the impact that the waste of ketchup caused by packaging design had on the overall CO2 emissions. This completely changed the results; for two of the four bottle types, the ketchup wasted had a bigger environmental impact than the ketchup bottle itself.

So it seems that packaging designers don’t care that much about food waste. Convenience, aesthetics and the ability to show food to its best advantage are key to packaging design. And as consumers we’re perhaps not sufficiently annoyed by the waste of a relatively low value product for manufacturers to do anything differently.

But in a more general sense, what do we learn from this? Firstly, despite the scale of problems in the world, there is an astonishing level of pointless micro-detail being studied. It would take a matter of minutes to do a back of an envelope calculation that showed that tomato ketchup is a small part of an individual’s environmental impact, and that an LCA expert’s time would be better spent looking at a more significant problem. Secondly, the assumptions that we make in relation to how different elements of a problem interact can completely change our results. In this case, the impact of the food wasted because of the packaging design was greater than the impact of the packaging itself. The authors go on to point out that they didn’t investigate how the packaging might influence ketchup portion size and discuss the importance of tomato content on viscosity and therefore how much is left in the bottle as waste. The impacts of the dedicated ketchup spoon remain a mystery. There is something truly masochistic about demonstrating how a minor change in assumptions would render your work invalid, and therefore how unapplicable your results are in any wider context. Thirdly, and despite all of the caveats on their assumptions, the answer is expressed with a meaningless level of precision (to the nearest gram of CO2 equivalent emissions per year).  

We have a tendency to believe that if someone has spent a lot of time thinking about a question, the answer is probably both correct and useful. Sadly this is not always the case. I will forever be intrigued by how we decide which problems are worth addressing, and in what level of detail. I liken this to doing a jigsaw. If you are going to spend a long time putting a single piece into a 1000 piece jigsaw, you want to make sure that it’s an important part of the picture, and not just a random bit of sky near the top corner. The trick therefore is to understand enough of the bigger picture to pick the right area of the jigsaw to be working on. Or just wait 7.5 million years and ask Deep Thought.

Postscript: You’ll have gathered that I get really annoyed by pointless LCA studies! And that your choice of ketchup bottle is trivial. But if you want to make change that matters, the things that make the biggest impact in your diet are discussed here. Since some of my friends obsess about plant based milks, I’ve written about those specifically, here. A more general discussion of pro-environmental behaviours is discussed here. There are numerous posts about plastic packaging here, with the most recent summary here.

3 thoughts on “Deep Thought and Tomato Ketchup”

  1. Hey Judith

    I hope you are well. I’m pleased we got to meet up before the lockdown. I imagine that Gawd Only knows when you are likely to be in Aber again, but in the meantime, I’m always pleased to follow your musings on FB 😊

    I enjoyed your most recent blog. Brilliant and entertaining as usual. Good job. Thanks.

    You didn’t discuss the possibility that meaningful information could be extrapolated from such studies, and then used to model the characteristics of a wider range of sauces and similar food items.

    I don’t know that the report findings do get used in this way, but I hope so, and even if it wasn’t, it could I’m sure, still be useful. If only to identify similar correlations in the “more” significant waste element embodied in packaging.

    Of course, you did point out that studies should look at the “bigger picture” and this is the main thrust of your beef.

    So, is there an indirect benefit to tomato sauce research, as I’m suggesting? ..or does it still fall within the realm of missing the point? I.e. even if all of the food wasted in packaging was significantly reduced, it’s still trivial in the scheme of things.

    If you got his far, thanks for listening. Stay safe Martino

    Sent from Mail for Windows 10


  2. Oh dear, I am one of those dweebs who fret about scraping the last scraps of ketchup (and everything else) out of the containers. My partner directed me to this post, but please can you tell her that I know my food-scraping makes negligible difference to anything, nor was it conditioned into me by my poverty-stricken father, I just find it satisfying to do, and it means less food washed down the sink to risk clogging it and making unpleasant smells!


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