Why kangaroos emit less methane when they ... um ... you know, pass gas
Scientists have known this for a while now, but new research gives us more information about why kangaroos are so much more efficient than cows.
Fri, Mar 28, 2014 at 11:53 AM
To paraphrase the famous kids' book, everybody passes gas. But, it turns out, not everybody produces the same kinds of gas. Let's look Down Under for an example. Scientists have long known that kangaroo flatulence and burps contained significantly less methane than the same emissions from cows and sheep, which, as you may have heard, are a major contributing factor to climate change. Why is this? Well, some brave scientists have explored the issue and come up with some answers.
According to research published March 13 in The ISME Journal, kangaroo guts contain a microbial community that helps to either reduce or completely eliminate the methane from their emissions. It all starts in the kangaroo foregut (like cows, kangaroos have stomachs with multiple chambers, allowing them to digest grass and other hardy vegetation in several steps). This enlarged forestomach contains a number of bacteria, most notably one called Blautia coccoides, but also several others in the Prevotella, Oscillibacter and Streptococcus families. These bacteria metabolize carbon dioxide (CO2) and hydrogen (H) into acetate (C2H3O2). Acetate, in turn, becomes a source of energy for the kangaroos.
This is different from the bacteria in cow guts (as well as in our own), which converts CO2 and H into methane (CH4) and other gases. That methane is considered waste and summarily disposed of, as opposed to kangaroos, which have found a way to put their emissions to good use.
So what comes next with this research? Well for several years now, scientists have wondered if the metabolizing process that doesn't create methane could be transferred over to cows or sheep. In this new research, the scientists took these kangaroo gut microbes out of the stomach environment and fermented vegetative matter in vitro. The result: very little methane was produced, especially compared to what would be generated by bovines such as cows.
This could have a pretty big impact, at least in theory. Australian farmers own more than 13 million beef cows and 74 million sheep, and agriculture produces 15 percent of the country's greenhouse gas emissions. A 2008 study published in the journal Conservation Letters, and reported on by National Geographic, estimated that replacing many of those cows and sheep with commercially raised kangaroos (the other red meat?) would reduce greenhouse gas emissions so much that the country would save more than half a billion dollars a year.
Obviously that hop is a long way away, but for now, we have a new clue as to why kangaroo flatulence is worth studying.
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