Tag Archives: food

A startling result

cowIn UK universities this is the season of project report writing for senior undergraduate students and report reading for their professors.   This year one of my students has been monitoring his personal ecological footprint and looking at ways in which he could use technology-based solutions to reduce it and then make recommendations to help others achieve the same [see my postings ‘Are we all free riders‘ on April 6th, 2016  ‘New Year Resolution‘ on December 31st, 2014].  He found that his weekly contributions to greenhouse gases (GHG) due to energy consumption in his flat or apartment, transportation and consumption of meat were 12.73, 5.87 & 8.60 kg carbon dioxide equivalents per week.  The total of 27.2 kg carbon dioxide equivalents per week is relatively low compared to the UK average but then he does not own a car and is living on a small budget.  What startled me was the proportion of greenhouse gases generated as a result of eating meat!

He consumed about 1.2kg of meat each week in about equal proportions of beef (12.14 kgCO2e/kg), chicken (2.84 kgCO2e/kg) and pork (4.45 kgCO2e/kg).  The numbers in parentheses are the greenhouse gas emissions from the production of each of these commodities in the UK and they can be compared to green beens or wheat at 1.55 and  0.52 kgCO2e/kg) respectively.  So, you don’t need to become a vegetarian but you could follow the example of my student by dropping beef from your diet in order to  make a significant individual contribution to reducing GHG emissions, or you could become a weekday vegetarian (see Graham Hill’s TED talk).

BTW – the diary cows, like the one in the picture, are lovely calm creatures and milk has a relatively small footprint at 1.19 kgCO2e/kg


How low can we go? An assessment of greenhouse gas emissions from the UK food system end and the scope to reduce them by 2050. WWF November 2009.

Running away from tigers

rsph graphicToday, the probability that you will have to run away from a tiger is very small, no matter where you live.  Tigers have lost 93% of their historical range that used to stretch from Turkey across Asia to Eastern China and southwards to Indonesia.  Tigers have no problem with the first law of thermodynamics – they instinctively know that if they take in more energy than they expend then the excess energy will be stored as fat and when they become overweight they won’t be able to catch you or whatever else they decided to chase for their next meal.

As a species we seem to have lost that understanding of energy balances.   Obesity is increasing in many parts of the world.  The situation is so serious in the UK, where more than two-thirds of the adult population are overweight or obese, that the Royal Society for Public Health has proposed that food should be labelled with the amount of exercise required to burn-off the calories it contains and they have suggested using the infographic in the thumbnail.  Of course, the Royal Society’s position paper does not mention explicitly thermodynamics (or tigers!) though it does effectively cite the first law by stating ‘the cause of obesity is excess energy consumption relative to energy expenditure‘.  By coincidence, this week I interviewed Professor Graham Kemp, in the Institute of Ageing and Chronic Disease in Liverpool, about energy flows through our bodies for a MOOC on Energy: Thermodynamics in Everyday Life.

If you wathermolectures posternt to listen to that interview or learn more about the thermodynamics underpinning the energy balances controlling our weight, climate change and your electricity charges, then you need to join the more than 4,500 people who have already enrolled on the MOOC that will run for five weeks from February 8th, 2016.  I will also be giving an accompanying series of lectures in London.

I was astonished to discover that there are fewer tigers in the world than people signed up for our MOOC.  Less than 3,200 tigers exist in the wild mainly because our growing population and prolifigate use of the world’s resources has destroyed their habitat and those of the other species with which we share this planet.




Productive cheating?

I cut out a Dilbert cartoon from the New York Times a few weeks ago that I found amusing and shared it with my new Head of School.  Dilbert informs his boss that he will be taking advantage of the new unlimited vacation policy by being away for 200 days in the coming year but will still double his productivity.  His boss replies that there is no way to measure productivity for engineers.

Of course, bosses are very interested in measuring productivity and marketing executives like to brag about the productivity or efficiency of whatever it is they are selling.  Engineers know that it is easy to cheat on measures of productivity and efficiency, for instance, by carefully drawing the boundaries of the system to exclude some inputs or some wasteful outputs [see my post on ‘Drawing Boundaries’ on December 19th, 2012 ].  So claims of productivity or efficiency that sound too good to be true probably aren’t what they seem.

Also in the New York Times [on October 15th, 2013] Mark Bittman discussed the productivity of the two food production systems found in the world, i.e. industrial agriculture and one based on small landholders, what the ETC group refers to as peasant food webs.  He reports that the industrial food chain uses 70% of agricultural resources to provide 30% of the world’s food while peasant farming produces the remaining 70% with 30% of the resources.  The issue is not that industrial agriculture’s claims for productivity in terms of yields per acre are wrong but that the industry measures the wrong quantity.  Efficiency is defined as desired output divided by required input [see my post entitled ‘National efficiency‘ on May 29th, 2013].  In this case the required output is people fed not crop yield and a huge percentage of the yield from industrial agriculture never makes to people’s mouths [see my post entitled ‘Food waste’ on January 23rd, 2013].