I often attend gatherings and events that have an environmental theme: it is not only part of my personal evangelism as an environmentalist and nuclear advocate, it is also simply enjoyable to discuss things with smart people who share some of my interests and concerns. Yesterday I attended a presentation that was somewhat different, in that the presenter conducted several interesting (and benign) experiments using the attendees as subjects. I won’t go into the details, but will just comment that the aim of the presentation was to introduce ways to encourage behavioral changes in others in order to promote sustainability.
The presentation was two hours long, and held in a room with overhead fluorescent lighting. I wondered at one point how to calculate each attendee’s attendance carbon footprint, based just on the emission intensity of the electricity powering the lights.
The lamps were 40-watt fluorescent bulbs, in six recessed protected ceiling fixtures each containing two bulbs. All the bulbs were operating for the duration of the event.
That works out to 12 bulbs, each consuming 40 watts of power for two hours = 12 x 40 x 2 = 960 watt-hours, or 0.96 kilowatt-hours.
That was grid power, so how much carbon came with those 0.96 kWh? Ontario’s grid is fed by five main sources of energy: coal, gas, hydro, nuclear, and “other” (mostly biomass).
What was the mix of energy sources between 1900 and 2100 yesterday? According to my database, it was the following:
|Fuel||Output (kWh)||CO2, metric tons|
As you can see, the total grid generation during that period was 37,274,000 kilowatt-hours, and the fossil sources—mainly gas but also coal and “other” (mostly biomass but some gas as well)—emitted 4,865 metric tons of carbon dioxide (CO2), the principal man-made greenhouse gas. You can see that nuclear was by far the single biggest producer; it accounts for nearly half the power produced over the two hour period.
So the emission intensity of the Ontario grid, in grams of CO2 per kWh during those two hours was 4,865,000,000 grams of CO2 divided by 37,274,000 kWh, which equals roughly 130.5 g/kWh.
How much power did the overhead fluorescents use? From my calculation above, 0.96 kilowatt-hours over the two-hour presentation.
So, with an emission intensity of 130.5 grams of CO2 per kWh in that period, the overhead fluorescents in the presentation room came with a carbon footprint of roughly 125.29 grams of CO2.
About 20 people attended the event. So we could say that each one of them had a carbon footprint of 6.27 grams of CO2, from his or her use of electric powered lighting.
Now, is that high, low, average? It all depends on which grid the electricity is coming from. The presentation was in Ottawa, Ontario. If it had been held across the river in Gatineau Quebec, each attendee’s carbon footprint from electric lighting would have been much lower. Quebec’s electricity has by far the lowest CO2 per kWh: something like 8 grams. So each attendee’s carbon footprint would have been 0.4 grams.
But what if the event had been held in Alberta, where the grid is primarily coal-powered? The CO2 intensity of Alberta grid electricity is around 900 grams—yes, nearly a kilogram—of CO2 per kWh.
So each attendee’s carbon footprint in that case would have been 45 grams, seven times what it actually was.
The mix of sources feeding the grid makes a huge difference to electricity conservation efforts.
At one point, the presenter asked the attendees to write down as many “sustainability” ideas we could think of. Knowing what I know about the Ontario grid, I of course wrote “Promote Nuclear Energy!”
I hope I was not the only one.