Let them Eat Seaweed

It all started with an observation. Joe Dorgan, a dairy farmer living on Canada’s Prince Edward Island, noticed that the cows he let graze near the ocean produced more milk than those he kept in land-locked pastures. He thought that this increased milk production was due to the oceanic cows periodically eating seaweed and began a small business selling “stormtossed shoreweed” to inland farmers. As his business expanded, Mr. Dorgan reached out to environmental scientists at Dalhousie University to further study the benefits of bovine seaweed supplements. At the time the release of greenhouse gases by cows was becoming a hot topic, so the scientists in charge – Dr. Rob Kinley and Dr. Alan Fredeen – decided to also collect data about methane production in seaweed fed cows. That’s when they hit discovery gold….

But first a brief background on methane, cows, and climate change.

Methane (CH4) is a greenhouse gas with 25 times the warming potential of carbon dioxide (CO2). Luckily, methane is currently released in smaller amounts than carbon dioxide. Methane is mainly produced by the chemical process of fermentation in certain bacteria and primarily in rice paddies, wetlands, and the digestive system of herbivorous mammals.

In cows, gut bacteria ferment digested plants. Some by-products of this process, such as acetate, propionate, and butyrate, get re-absorbed into the cow’s digestive system. However, the largest by-product, methane, gets released back into the environment as cow burps. Because there are a large number of cows on earth (~1.5 billion) and because methane is such a powerful greenhouse gas these burps or more formally “enteric methane emissions” add up. They’re responsible for close to 14% of the annual greenhouse gases produced by humans!

The enormity of enteric methane emissions has inspired a massive scientific search for solutions. By providing farmers with specialized infrastructure and equipment some methane from cows can be captured and converted into renewable energy. Scientists have also found ways to reduce an individual cow’s methane production. Successful reduction strategies include selective breeding, antibiotics, microbial pills, vaccinations, and synthetic supplements. Dr. Kinley’s and Dr. Fedeen’s discovery added seaweed supplements to this list of solutions. Their initial test found that methane production in cows fed seaweed dropped 16% – a significant amount compared to other reduction methods.

Excited by these preliminary findings, Dr. Kinley began a global search for other methane busting seaweed species. Today he’s joined by an international network of scientists including those at CSIRO (Australia’s national science agency) and UC Davis. The leading contender is a tropical species called Asparagopis taxidormis. Just a sprinkle of this species, between 0.25-1% of a cow’s total diet, can cut a cow’s methane production by a staggering 50-90%!

The key to A. taxidormis success is a compound called bromoform which inhibits methanogenesis. This chemical is produced by most seaweeds and phytoplankton but in far larger amounts in A. taxidormis.

Unfortunately, bromoform also has two risks associated with its production and use. First, it’s the source of bromine a short-lived but still ozone-depleting chemical. Second, bromoform is an irritant and potential carcinogen when inhaled or absorbed through the skin at a high concentration. Scientists are currently studying both these potential problems. Models show that an increase in bromine will pose a minimal risk to the ozone and one that is far outweighed by the benefits of greenhouse gas reductions. Chemical profiles of milk and meat from seaweed fed cows show negligible levels of bromoform. Still, these are trade-offs and risks that scientists want to thoroughly understand before implementing a worldwide program of feeding cows this plant.

Scientists are also conducting multi-year studies to ensure there are no unexpected long terms health effects in the cows taking this supplement. So far, the only one observed is rather predictable and good! Cows typically lose between 5-12% of their daily energy through methane emissions. In contrast, cows fed seaweed are more efficient and so requiring less food. This makes seaweed supplements a win for our climate and for the farmers involved. Researchers are also helping farmers with the logistics of feeding this supplement to their cows. For picky cows, the answer was as simple as disguising the seaweed supplement with a coating of molasses but finding a way to prevent hungry and less discerning cows from eating their neighbor’s supply has proven more difficult! Other scientists are working with sea farmers in Tasmania, Hawaii, and California to figure out how to grow and harvest A. taxidormis.

Climate change can be a difficult topic to introduce in the classroom because of the scope and implications of this pressing issue. Focusing on solutions provides a healthy mix of reality and inspiration plus a chance to discuss the science behind a solution. I love the out-of-the-world solutions like a space elevator for carbon dioxide ions . I also love KISS (Keep it super simple) solutions like this one! To dive deeper into the science of methane emissions and seaweed read this recent PLOS ONE article.