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Are we sure that the anaerobic digester is a net carbon producer? What would have happened to the hog waste otherwise? This article would imply that there are

Are we sure that the anaerobic digester is a net carbon producer? What would have happened to the hog waste otherwise? This article would imply that there are other environmental factors to consider: http://news.nationalgeographic.com/news/2014/10/141028-hog-farms-waste-pollution-methane-north-carolina-environment/ http://news.nationalgeographic.com/news/2014/10/141028-hog-f... Steve Wing, the UNC-Chapel Hill epidemiologist, says hog operations give off ammonia, methane—a potent greenhouse gas—and hydrogen sulfide, which causes headaches and eye irritation. They also release endotoxin, an allergen, and at least a hundred volatile organic compounds, many of which contribute to the odor of hog farms. [...] The result? The covers trap odors, making the operation less smelly. Rain falling on the farm isn't contaminated by lagoon waste. And the farm is transforming waste into electricity-generating enough to power 90 refrigerators.

hwillis 10y ago
Anaerobic digestion causes the production of (more) methane rather than co2. Methane is a 100x more potent greenhouse gas than co2 over the short term. Over hundreds of years it breaks down but even a century from now it's 30x worse. Anaerobic digestion is great as long as leaks are kept below 1%. Doing so is tricky.
- nkurz 10y ago
  Over hundreds of years it breaks down but even a century from now it's 30x worse. That doesn't sound right. Most sources I've seen[1] say that atmospheric methane has about a 10 year half life. I think the 30x figure you refer to actually represents the sum of methane's annual impact over 100 years. Despite the greater immediate efficacy as a greenhouse gas, the amount of methane remaining after a century should be so small that the impact in the 101st year would be extremely (likely unmeasurably) low. [1] For example, https://en.wikipedia.org/wiki/Atmospheric_methane https://en.wikipedia.org/wiki/Atmospheric_methane

hwillis 10y ago

Anaerobic digestion causes the production of (more) methane rather than co2. Methane is a 100x more potent greenhouse gas than co2 over the short term. Over hundreds of years it breaks down but even a century from now it's 30x worse. Anaerobic digestion is great as long as leaks are kept below 1%. Doing so is tricky.

nkurz 10y ago
Over hundreds of years it breaks down but even a century from now it's 30x worse. That doesn't sound right. Most sources I've seen[1] say that atmospheric methane has about a 10 year half life. I think the 30x figure you refer to actually represents the sum of methane's annual impact over 100 years. Despite the greater immediate efficacy as a greenhouse gas, the amount of methane remaining after a century should be so small that the impact in the 101st year would be extremely (likely unmeasurably) low. [1] For example, https://en.wikipedia.org/wiki/Atmospheric_methane https://en.wikipedia.org/wiki/Atmospheric_methane