Sunday, April 20, 2008

Saul Griffith’s Carbon Footprints Part II – Some numbers

Following my previous post, I thought to look at Saul’s energy usage / carbon footprint calculations by separating out his personal energy usage from his work related consumption.

See the notes below on how I have separated the work from the personal energy usage. The chart below separates out the numbers into 4 categories, and speaks for itself. Almost half of Saul’s home energy usage comes from “Food and Stuff” which represents the embodied emissions of his consumer purchases. Of course, as Saul has pointed out, he has probably underestimated the energy usage associated with these categories.

Again, people can dispute the difficulty of calculating the embodied emissions of “stuff”, but at almost 4 times the energy usage of his home heat and electricity, Saul’s calculations should at least, again, put the importance of embodied emissions in perspective.

A few other notes:
  • Like the truck driver in my previous post, Saul’s major source of carbon emissions relates to his travel for work. His total work related energy use should be compared to the value of his work, in revenues from his company or at least with the costs associated with the company. This figure should be compared to other businesses in the same sector.
  • Energy usage of ‘stuff’ related to work would probably need to be more comprehensive, including things like capital goods (servers, furniture), services delivered to his workplace (fedex, as well as consumables (like pencils and paper and printer toner.)
  • Here is the data:
Some notes on separating work from home usage:
  • Saul mentions that most of his air travel is for work, so I put in a “wild guess” number of 90% related to work. Inversely, I assumed 90% of his car usage was for personal (ie home) use.
  • In stuff, I only allocated his laptop to work. As noted above, there are probably other work related goods that should be added to his work “stuff”
  • The allocation of societal consumption is an interesting one. Here I have assumed it is half for work and half for home. After all, government exists to serve both individuals and to support businesses. Although the actual impact at ~3% in total is not very big, a more thoughtful method may still be needed here. For example, there could be an argument that government is there only to serve the people, so 100% should be allocated to individuals. At the same, this would distort the picture for developing nations (and the goods they export), especially since substantial government resources are probably expended on supporting businesses.



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