What is the environmental cost of a MWh?

10.12.06 | 1 Comment

In previous entries we’ve discussed how much electricity the US is producing and consuming, what the sources of generation are, and how much it costs from a monetary perspective. But there are other costs.

This entry will focus on the largest fuel source for electricity generation, coal. This is an ancient source that is well understood and drives a massive supply chain from real estate with mineral rights clear through mining and transportation and finally ending up in places like electricity generation. Without a doubt the technology for oxidizing (burning) coal to create heat which in turn is transferred to liquids which through phase change from liquid to gas pressurize and then drive turbines attached to generators, has improved dramatically. Back during the early days of the industrial revolution cities like Pittsburgh were covered in smog and soot.

The state of the art today is that approximately 1,000 kg (~2,200 lbs) of carbon dioxide and approximately 13kg of sulfur dioxide and nitrogen oxides are emitted into the atmosphere for each MWh of power generated by burning coal. As is well known, carbon dioxide is a major contributor to global warming and the sulfur and nitrogen oxides are key ingredients to acid rain. This level of emissions is a vast improvement from the late 19th century, but still constitutes a problem. With 5% of the population of the earth, the US is responsible for 23% of carbon dioxide emissions on the planet (not just electricity generation, transportation has alot to do with that number as well.) (Source: US Environmental Protection Agency.)

One of the key challenges in limiting emissions is the increasing demand for electricity. Right now, the demand is outstripping the new cleaner generation technology’s installation rate which means that older, less efficient, more polluting coal generation plants are staying in production longer than is desirable. Each time a new technology (be it natural gas or photovoltaics) is deployed, it either meets new demand or displaces older, less cost effective generation technologies. Given the increasing cost of fossil fuels, there is an opportunity to focus our attention more completely on the installation of renewable electric generation at a scale that makes the economics attractive in addition to exceeding the growth in electricity demand. That could have the effect of displacing less effective generation technologies and as a side effect, limit harmful emissions.

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