“The overall question we’re trying to answer is how we can use algae to reduce a cow’s carbon footprint,” said Dr. Nichole Price. Price is a marine ecologist at the Bigelow Laboratory for Ocean Science and a professor of environmental science at Colby College, both located in Maine.
The basic idea is to use algae as a feed supplement in cattle to reduce methane emissions from their digestive systems. These are called enteric emissions. Algae is an umbrella term used to describe the plant-like organisms living in the world’s oceans. It’s a huge group ranging from microscopic phytoplankton to giant kelp. The larger of these species – the ones that can be seen by the naked eye – are called seaweeds or macroalgae.
Price is currently leading a multi-year interdisciplinary research project titled “Coast-Cow-Consumer.” The project is focused on studying which types of algae may help reduce enteric methane emissions. It’s a collaboration between academic institutions, for-profit entities and nonprofit entities funded by the USDA Sustainable Agriculture Systems, Organic Valley, Stonyfield Organic and the Shelby Cullom Davis Charitable Fund.
Methane is a potent greenhouse gas accounting for 16% of total global emissions. According to the U.S. EPA, methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere. Over the last two centuries, methane concentrations in the atmosphere have more than doubled, largely due to human-related activities.
Dr. Andre Brito, an associate professor of dairy cattle nutrition and management at the University of New Hampshire, and members of the Coast-Cow-Consumer team joined Price in the discussion, which was part of the Maine Climate & Agriculture 2022 webinar series. Brito designs the on-farm algae feeding trials for UNH’s dairy farms.
According to Price, cattle contribute to 62% of total global livestock emissions. Most emissions, especially from ruminants, result from burps. “Cows burp out methane from the rumen,” Price said. “There are microbiota in the rumen called methanogens that generate methane as a byproduct.” This process is called methanogenesis. Burping methane also represents an energy loss for the cow – as low as 4% but up to 12%, according to Smith. If that energy could be maintained, it could be put toward milk or meat production.
Australian research scientists are at the forefront of using an artificial lab setting (called an in vitro system) to look at the methane reduction potential of algal species when used as feed additives. Specifically, they studied the species Asparagopsis taxiformis. This species contains brominated compounds that can change the rumen microbiome and reduce the methanogen population. These Australian researchers found a 99% reduction in methane in their in vitro systems.
There are challenges, however, to feeding A. taxiformis, said Brito. It’s not available in the Northeast, it’s expensive ($265/lb.) and there are concerns about the transfer of iodine and bromide into milk. It’s also a highly invasive species with low biomass production and is primarily wild harvested.
Price and Brito want to shift the focus away from A. taxiformis and begin to think about native algae in the U.S., especially in the Northeast. They are particularly interested in focusing on native algae that can be produced sustainably at scale and that produce sufficient bioactive compounds to be effective against methane. With about 10,000 macroalgae species globally, there are a lot of options for researchers to consider.
“We have come to understand that it might not be a silver bullet or a single alga solution,” Smith said. “There are many different nutritional qualities to different species of algae, and they can generate different bioactive compounds that may effectively reduce methane emissions. We’re also thinking about microalgae species – the phytoplankton that are floating around the ocean that are naked to the invisible eye.”
One alternative, said Brito, is Chondrus crispus, commonly known as Irish moss. Brito cited in vitro studies that showed a 12% reduction of methane with a 0.5% inclusion of Irish moss on a dry matter basis. To build upon these data, Brito’s team conducted studies at UNH and Wolfe’s Neck Center for Agriculture & the Environment in Freeport, Maine. To measure methane production, they utilized the GreenFeed system. Animals place their heads into a freestanding chamber where pelletized grain is released. Sensors on the GreenFeed unit then measured the methane released through burping and breathing.
Brito said, “The red seaweed, C. crispus, resulted in low to medium suppression of methane production in two trials without negative effect on milk production, but dry matter intake decreased in trial one [UNH] and production of milk fat and milk protein decreased in trial two [Wolfe’s Neck].”
Brito explained that many cattle farms in the U.S. are already feeding a seaweed supplement, in the form of dry “kelp” powder made from Ascophyllum nodosum, a common rockweed in the coastal Northeast. Unfortunately, his research showed that this rockweed supplementation, fed at a rate as high as 6% of dry matter intake, does not reduce methane production.
“There’s still a lot of research to be done to look at the efficacy of any one of these approaches,” Smith said. “It’s not only that we’re looking for a reduction in enteric methane emissions. Changes in manure quality, using algae as a feedstock to add to manure biogas generation, feed replacement or direct fertilizer replacement may increase sustainability of the dairy industry.”
by Sonja Heyck-Merlin