I'm a little embarrassed to ask this question at this stage of the climate game but, in searching, I seem to get contradictory answers.

For example, here: https://www.eia.gov/tools/faqs/faq.php?id=73&t=11 we see 215.4 lbs CO2 giving 1 million btu heat. Since 1 million btu = 293 kWh, we end up with 0.735 lbs/kWh.

But at this site: http://shrinkthatfootprint.com/electricity-emissions-around-the-world we see 1 kg/kWh = 2.2 lbs/kWh

New York times https://www.nytimes.com/2007/11/07/business/businessspecial3/07carbon.html gives 1.9 lbs/kWh

These are very different numbers (too different for the problem to be type of coal, at least for eia vs NYT) and I have found other numbers at other sites.

Can anyone point me to a site that I can trust for this number and others like it (related to energy production)? Or else point out the elementary error I am making?

  • 1
    $\begingroup$ You probably mean electric energy, not thermal energy. $\endgroup$
    – Poutnik
    Nov 20 '19 at 6:41

The value from EIA is pounds of $\ce{CO2}$ produced per kWh of thermal energy produced, while those from the latter two sources are pounds of $\ce{CO2}$ produced per kWh of electrical energy produced. Since the thermal efficiency of coal-fired plants is ~37% (~37% of the coal's thermal energy is converted to electrical energy), converting the EIA figure to pounds of $\ce{CO2}$ produced per kWh of electrical energy produced gives us:

$$ 0.735 \frac{\text{lbs }\ce{CO2}}{\text{kWh thermal energy}} x \frac{\text{1 kWh thermal energy}}{\text{0.37 kWh electrical energy }} = 1.99 \frac{\text{lbs }\ce{CO2}}{\text{kWh electrical energy}}, $$

i.e., about the same as the NY Times and shrinkthatfootprint figures.


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