Cattle are emitting methane into the atmosphere at an alarming rate, and this cow at the Ra Brown Ranch farm in Texas is just one of them, but we've found a solution.
摄影：KAREN KASMAUSKI, NATIONAL GEOGRAPHIC CREATIVE
Written by: Rebecca Rupp
Our love of cheeseburgers is not of much benefit to the planet. As a source of ingredients for burgers, tawny steaks, shakes and ice cream, whether it's Holstein, Juanshan or other breeds of cattle, it's wreaking havoc on the Planet's climate. But we seem to see a solution to this problem, and the answer may be seaweed. Specifically, it is a red algae called Asparagopsis taxiformis by scientists.
One of the biggest environmental problems cattle causes is that they continue to emit methane, which is 30 times more destructive than the equivalent amount of carbon dioxide. The 1.5 billion cattle on Earth did not mean it: it was an inevitable byproduct of the physiological system of ruminants. Cattle and other ruminants digest fiber-rich foods through the process of intestinal fermentation, with the help of stomach bacteria, which is why they can eat grass for a living. The end product of this microbial metabolism is methane, which produces an average of 200 to 500 liters of methane per cow per day.
Despite many jokes about cows farting, in fact 90% of methane emissions come from slightly indecent burps of cattle. According to the Food and Agriculture Organization of the United Nations, livestock around the world emit about 7 billion tons of carbon dioxide each year through hiccups and farts. Livestock comes from 14.5 percent of total anthropogenic greenhouse gas emissions, more than global emissions from cars and airplanes combined.
Although sheep, goats, buffalo, giraffes and camels all produce methane, 65% of them come from cattle. In a recent study, Ken Caldeira of the Carnegie Institute's Department of Global Ecology noted that every 1 kilogram of beef we consume emits the equivalent of burning 8.5 liters of gasoline. Considering that Americans consume 450,000 tons of beef a year at McDonald's alone, the consequences can be imagined.
Of course, one of the most obvious solutions to this problem is to abandon raising livestock and eating beef. Gidon Eshel, a professor of environmental physics at Bard College in New York, calculated in a recent scientific paper published in the Proceedings of the National Academy of Sciences that every American who forsakes beef contributes to cutting carbon dioxide emissions each year equivalent to using 230 liters less gasoline or 308 kilograms of coal. The best case scenario is not even to drink milk, because not only does each cow emit more methane than beef cattle, they also have 10 times more in the United States than beef cattle.
Alternatively, we can add a little seaweed to the feed of livestock.
A major study conducted by Robert Kinley of the Australian Federal Science and Industry Organization, Rocky De Nys, an aquaculture professor at James Cook University in Australia, and colleagues, tested 20 different types of seaweed in the artificial bovine stomach – the artificial bovine stomach is simulated by using rumens and microorganisms in a bottle to simulate the condition in the bovine stomach. When forage or feed is added to the artificial cow's stomach, it ferments and scientists can measure the amount of methane produced. When tested with the red algae yew-like sea aspartum, methane production was reduced by 99% – the effect De Nys described as "quite remarkable". Experiments on sheep have shown that methane emissions are reduced by 70% by simply putting 2% dried yew-shaped sea aspartate in the feed. De Nys says that just as you sprinkle a little spice on your roast chicken, just add this red algae to your feed.
In the experiment, cattle that were injected with yew-like seagate burps and farted less often than cattle that were not injected.
Photograph by RASMUS LOETH PETERSEN, ALAMY
What makes yew-like sea asparts so effective is that it contains a chemical called tribromomethane (CHBr3), which interferes with microbial digestive enzymes that produce methane. The results of this research have given hope to the growing environmental problems and the public who love beef milk. Mouth-full methane-flavored hiccups or other indecent ways to vent methane into the atmosphere are not only about the environment, but also a waste of energy that could have been better used to increase food production. Seaweed experiments in Canada have observed gratifying things from cattle living by the sea, which regularly eat seaweed that has been carried ashore by storms and are stronger and healthier than cattle living inland. In other words, the less methane in the cattle discharge, the more meat grows.
Unfortunately, seaweed cannot quickly solve the problem of atmospheric methane excess. Because we can't get enough seaweed. Scientists have calculated that it takes 60,000 hectares of seaweed farms to provide enough seaweed for Australia's 29 million cattle, and three times the size of seaweed farms needed to supply 92 million cattle in the United States. Although seaweed farming is a fast-growing global industry, there is nothing that can be done to meet such a huge demand.
Reducing methane emissions from cattle requires large amounts of seaweed.
Photo by Michael Forsberg, NATIONAL GEOGRAPHIC CREATIVE
Increasing numbers of related bills now target reducing methane emissions from livestock. In 2014, the Obama administration passed a Climate Action Plan calling for a 20 percent reduction in methane emissions from U.S. cattle by 2020; in September, California Governor Jerry Brown also began considering methane emissions from cattle, arguing that "if there is a practical technology that can reduce bovine methane emissions," it should be vigorously pursued.
Although there may not be such a practical technology at present, the yew-like sea gate winter looks quite promising.
(Translator: King of Hearts)