If you’re considering feeding biochar to feedlot cattle to reduce methane emissions, you may want to manage your expectations.
Recent research out of the University of Lethbridge and Agriculture and Agri-Food Canada’s (AAFC) Lethbridge Research Centre found that feeding biochar didn’t cut the cattle’s methane emissions, although it didn’t harm the animals, either.
Previous research, conducted in a lab, showed that biochar may reduce methane emissions by as much as 25 per cent. However, when the Lethbridge researchers reviewed the facts, they weren’t sure they’d see a reduction, says Stephanie Terry, AAFC research biologist.
“So essentially we wanted to conduct a robust study to actually test it,” she adds. Terry completed the research project as part of her PhD.
The project consisted of two trials. The first was a smaller metabolism trial that included eight Angus-cross heifers, which gave researchers a more in-depth look at animal response. Each animal went through each treatment. Diets were a backgrounding, high-forage ration based on barley silage. The control included no biochar.
The second trial was larger, comprising 160 Angus-cross steers. Instead of each animal partaking in each treatment, the steers were divided evenly into four treatment groups, receiving a consistent amount of biochar through the trial (or in the case of the control group, no biochar). The trial covered the steer’s time in the feedlot, from backgrounding to slaughter.
One treatment included 0.5 per cent biochar in the total diet (dry matter). Another included one per cent biochar and the third two per cent biochar. The control group received no biochar. Both trials used the same amount of biochar in the treatments.
While the earlier lab study appeared promising, Terry says it’s not unusual for lab results to fall flat in the field, especially if the rumen is involved. The real world is more complicated than a lab, as researchers are dealing with animals, and as some microbiota from the lab doesn’t survive in the rumen.
“It just never quite simulates the rumen as well as…the actual rumen.”
While we most often hear about research that has found a benefit or positive result, Terry says it’s extremely important to publicize results from projects even if there was no benefit.
“I think that’s something lacking, a bit, in research these days.”
However, generally people don’t publish their results when they don’t see the positive effect they wanted. “Then you get people repeating the same experiments and finding the same results.”
This can lead to a research gap, with researchers testing the same idea again and again.
As for how feeding biochar to cattle first caught researchers’ interest, Terry says it’s related to biochar’s soil enrichment reputation. In 500 B.C., inhabitants of the Amazonian rainforest enriched the soil through burning and composting, which produced black soils. Biochar increases the water-holding capacity of soils and improves crop productivity in nutrient-poor soils. It’s also highly stable, remaining in the soil for long periods of time and acting as a carbon sink, she adds.
Terry says one theory on how biochar might reduce methane emissions was tied to its large surface area and porous structure. Rumen bacteria would colonize the biochar, increasing volatile acids. But methane-producing bacteria would also be part of the biofilm that formed on the biochar.
“So if you’re increasing biofilm formation, it actually makes sense you’d also get an increase in methane production.”
In fact, the Lethbridge project found that microbes associated with methane production increased in manure from cattle fed biochar. There’s no direct cause and effect, but it does indicate that the biochar may actually increase methane production, Terry explains.
Terry does note that they tested pine-sourced biochar that underwent a specific temperature. Biochar from a different source, that underwent a different temperature, or with different pre- or post-treatments, could perhaps yield different results.
AAFC Lethbridge has also been looking at several other potential methane-reducing feed additives. For example, they’ve examined humic substances, which are compounds of humus and mining by-products, but didn’t find any methane reductions in animals. They’re also currently studying seaweed’s potential as a methane-cutting feed additive.