I am writing in response to a dairy farmer’s April 25 submission, “Renewable natural gas will help Maine reach its climate goals.” I fully support the anaerobic (without oxygen) digestion of manure; the process can, indeed, allow methane to be captured through a biological process and then utilized as a fuel. That is a winning proposition for the environment. To say, however, that methane created in this fashion is “renewable” is a stretch, as is the notion that a “carbon negative” gas is created in the process.

Carbon dioxide is produced when methane is combusted, and it is a less potent greenhouse gas than methane, but it is hardly “carbon negative.” In fact, carbon dioxide is responsible for about three quarters of the world’s carbon emissions. It is negative only in comparison to methane.

Equally important, focusing on the methane captured from manure ignores the much larger quantity of methane entering the atmosphere from a cow’s digestive system – about a quarter of all methane emissions in this country. Such emissions explain why it is meaningless to isolate the methane extracted from manure and label it “renewable.” Doing so appears to be a disingenuous strategy by the Summit Gas Co. to boost its case for expanded gas infrastructure.

Anaerobic digestion, with the production of methane for fuel, reduces some methane emissions but the overall process of raising cattle is still extremely emissions intensive. Research with new types of feed (including seaweed), however, offer promising reductions in belched methane.

Joe Hardy

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