My Steak Dinner

My Steak Dinner
11 December 2018

High-profile businesses may be getting it wrong by reducing their use of plastics to improve environmental performance. Although well-meaning, there are clear flaws in the current anti-plastic media climate. Decisions should be founded on sound environmental science, not knee-jerk populism.

On 11th December 2018, I gave a presentation to the Design for Sustainability conference entitled “Are single-use plastics really so bad? A role for life cycle thinking”. I’m in a privileged position – I spend most of my working life helping businesses use life cycle thinking to identify and address their biggest environmental impacts. It’s a brilliant job. The breadth of studies we have performed is amazing, ranging from a brick to a supercar’s engine, or from a timber joist to grid-scale electricity storage using ammonia. Through this body of work, I have established some personal “rules of thumb” (which may be the subject of other blogs in the future), one of which is that, in the UK at least, plastic film is rarely environmentally significant.

To test my hypothesis, I set out to determine the full environmental footprint of something tangible. As food packaging is frequently vilified, I chose to study my steak dinner. This meal comprised seven foods (steak, potatoes, salad (lettuce, tomato and cucumber), a banana and a glass of milk), all of which were packaged in plastics.

I weighed all the packaging, and the food I prepared. I noted where in the world the food originated. I estimated the transport all the way to the supermarket, storage there, transport on to my home, storage in my house and then the energy consumed cooking. I also anticipated the likely end of life fates (recycling for the milk bottle and steak tray, anaerobic digestion for the banana skin, landfill for the plastic film).

All of this information was loaded first into an Excel spreadsheet, to compile and collate the data, and then into SimaPro, a dedicated life cycle software package that we use for the purpose. As usual, I got a wealth of fascinating information from the study, but (for the purposes of this blog) the big picture is revealed in two plots.

The total weight of the ingredients in my meal was 1.29kg; its overall carbon footprint was almost ten times that, at 12 kg CO2 eq. The contributions by ingredient and by life cycle stage are presented in the column chart above. Packaging doesn’t appear on the radar. Air freighting the bananas and cooking the potatoes make small contributions, but the results are absolutely dominated by the environmental impacts associated with producing the steak.

When the results for one environmental indicator are so one-sided, it is particularly important to examine some others, so that erroneous conclusions are not drawn about the best mitigation options, leading to burden shifting to other impacts. In this study, I included eleven different indicators. My chart below shows what fraction of the total burden for each indicator falls to each life cycle stage, with the production of the ingredients further split between the steak and everything else.

This plot shows that the steak’s dominance in its contribution to GWP is matched in many other indicators. On average, the steak is responsible for 60% of the environmental impact of my dinner. All of the other ingredients contribute 11%, meaning that the ingredients together contribute also three quarters of the impacts.

Compare this with the packaging contribution, which is just 1.6%, and the waste (which is also mostly plastic), at 1.5%. And then let’s think about why the packaging is there. It preserves the food. It extends the life of the steak by up to 10 days, the cucumber 14 days, the banana 3 days. This tiny contribution to the environmental impact makes it significantly more likely that the main environmental impact, of creating the food in the first place, will not be wasted.

When I shared these results with a colleague, he asked what difference it would have made if I had chosen a tuna steak. This is typical of the sort of sensitivity analysis we do, challenging our initial assumptions and adjusting key parameters to see the implications. Although it was not possible to quickly find a full dataset for tuna, I did discover that the carbon footprint of its production is about one twelfth of the steak, and a portion weight is nearly half. That has the following effect on the first plot, and reduces the total carbon footprint of the meal by almost a third, to 4.25 kg CO2 eq.

I think the conclusions from this study are clear:

  • Firstly, single-use plastic packaging for food performs a very valuable task, compared to its impacts, in increasing the chance that the main environmental impacts of our food chain are not incurred totally in vain because of food wastage.
  • Secondly, if we really want to take action about the environmental impacts of our food, we should cut the hype about its packaging, and think more about our food choices. As a die-hard carnivore, I find that tough to take, but that is what the science tells me.
  • Thirdly, we see that life cycle thinking enables everyone to put aside preconceptions and instead use science to make informed decisions, be they about the choice of food, packaging or its source.

If you would like help using life cycle thinking to identify the right choices for your business or products, please get in contact: I’d also love to hear your thoughts on this article.