June 9, 2011

How many cows is wind energy equal to?

Estimates of methane (CH₄) gas emissions from cows (via belching and farting, not the methane contained in their manure) vary widely, but they generally range between 500 and 1,000 grams/day.

Cows also exhale carbon dioxide (CO₂): about 2,000-4,000 g/d.

Methane is considered to be a more powerful greenhouse gas than CO₂, about 25 times. So a single cow emits 14,500-29,000 g CO₂-equivalent/d.

In Vermont, according to the U.S. Energy Information Administration, electricity generation emits an average of about 27,500,000 g CO₂/d, having the same greenhouse gas effect of 950-1,900 cows.

There are about 150,000 cows in Vermont. Therefore, they produce 80-160 times as much greenhouse gas as the state's electricity production.

In the spirit of the wind industry's totting up equivalences for their turbines' production of electricity (never mind that they fail to show such actual reductions), what is the cow-equivalence of wind turbines in Vermont? (Wayne Gulden in Ontario is the source of this idea.)

Vermont's 10 billion g/y CO₂ emissions from electricity generation is from about 7,000,000 MWh, i.e., 1,430 g/MWh.

At a (generous) 25% capacity factor, a 1-MW wind turbine produces 2,190 MWh/y, therefore theoretically (ignoring the inefficiencies of the grid in coping with wind's variable feed) displacing 3,131,700 g CO₂/y. One cow produces 5,292,500-10,585,000 g CO₂e/y.

In Vermont, therefore, 1 MW of installed wind capacity is theoretically equivalent to 0.25-0.5 cows, or about 0.4 — even less if the cows' manure were factored in.

The 40-MW project in Sheffield will be "equivalent" to removing 16 cows from the state.

The 30-MW Searsburg expansion in Readsboro will be "equivalent" to removing 12 cows.

The 10-MW Georgia Mountain project in Milton will be "equivalent" to removing 4 cows.

The 63-MW Lowell Mountain project will be "equivalent" to removing 25 cows.

That's 145 MW of new giant wind projects, for the greenhouse gas equivalence of removing about 58 cows from the state. In other words, giant wind turbines in Vermont — despite substantial destruction of mountain ecosystems, fragmentation of habitat, direct harm to wildlife, and vandalism of fabled mountain views — will have virtually no effect on the state's greenhouse gas emissions.

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Update. Granted, Vermont is not an isolated grid but is part of the ISO New England grid, which in 2015 produced 40,000,000 tons of CO₂, about 750 lb/MWh, of which Vermont contributed less than 0.03%. Therefore, 1 MW of installed wind capacity would theoretically offset 250× more CO₂ than calculated above for Vermont alone, or the equivalent of about 100 cows per MW. On the other hand, Vermont gets most of its electricity from Hydro Quebec (CO₂ free).

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