Testing biochar as cattle amendment to reduce methane emissions
Governments worldwide have in recent years announced plans to reduce methane emissions as part of a larger effort to regulate atmospheric emissions. Both the EU and the U.S. under Biden are striving to reduce methane emissions from 2020 levels by 30% by 2030.
As one example, the Netherlands, the largest meat exporter in the EU and the second largest ag exporter worldwide behind the U.S., is planning on reducing livestock numbers by one-third.
There are segments of the livestock industry which are looking for ways to reduce methane emissions without putting farmers out of work. For example, it’s been proposed that using biochar as a feed supplement for cattle can reduce methane emissions.
Dr. Andrea Wilson, research associate professor in ruminant nutrition at the University of Nebraska-Lincoln (UNL), recently undertook a series of experiments to determine how including biochar in cattle feed affects methane emissions from cattle.
The study was supported by a number of entities, including High Plains Biochar, which produces biochar for a variety of uses, including as a soil amendment, for manure management and other purposes.
At present, biochar is “generally speaking not permitted as an additive” to feed for livestock raised for human consumption in the U.S., Wilson said.
The first experiment Wilson ran involved just six animals, who eventually were euthanized and did not enter the food chain. That kind of approach, she acknowledged, is both “expensive” and “underpowered” – because it didn’t involve a large enough sample size of animals.
Nonetheless, Wilson and her team fed the six animals two different diets – a growing diet and a finishing diet – then put them in headboxes for 24 hours to measure the amount of methane the cattle emitted. Headboxes are stalls with enclosures around the cattle’s heads. The boxes help measure how much methane and carbon dioxide are burped out by each cow. Wilson said 97% of methane eructed by cows comes from burping.
“We kept a constant flow of air through the box,” Wilson said. “We had to have someone there through the 24 hours to monitor the cows.”
Wilson’s team then measured how the biochar-supplemented diets affected performance and methane emissions. With the growing diet – a blend of brome hay, wheat straw, corn silage, wet distillers grain and biochar – there was no real difference in intake between the control blend with no biochar and the blend containing biochar.
There was also no difference in the total amount of methane emitted in a day, but there was an 8% reduction in the amount of methane emitted per kilogram consumed of dry matter.
Likewise, the finishing diet showed a 16% reduction of methane per kilogram of dry matter intake.
Wanting to pursue this line of inquiry further, Wilson received a waiver from the FDA to study a larger number of animals. The study left the headboxes and entered a methane barn – basically chambers where pens of animals are kept and through which a constant flow of air passes to be able to measure methane and carbon dioxide emissions from the cattle.
In the methane barn, the researchers fed control groups of animals (fed no biochar) and test groups of animals (fed three different types of biochar, all of which accounted for 1% of the ration). As with the previous experiment, the researchers fed both a growing diet and a finishing diet.
For all three types of biochar – and for both diets for all three types of biochar – there was “not much significant difference” in methane emissions between the diet with biochar vs. the diet without biochar, Wilson said.
Emissions of methane and carbon dioxide were “near identical,” both in terms of grams per day and grams per kilogram of dry matter intake.
Wilson is in the process of creating a methane emissions research project where biochar is 0.5% of the feed.
Using biochar as a feed supplement is “not as promising as we had hoped,” she said. However, biochar may have different benefits in the livestock industry, according to other studies done by Wilson and her team.
“Pen amendment and manure amendment is looking much more promising at this point,” she said.
In feedlots, 82% to 88% of nitrogen and phosphorus in feed gets excreted. If properly managed, those nutrients can be recaptured and reused in agriculture.
In this experiment, biochar made from eastern red cedar was spread on the surface of feedlot pens. The study was divided into a winter feeding period and a summer feeding period. Because biochar was used as a pen amendment, there were no restrictions from the FDA.
The study was set up to measure both animal performance and nutrient retention in the manure.
In the winter study, there was no change in performance. However, there was an increase in the amount of nitrogen measured in manure accumulated in a pen with biochar as compared to the control pens, with no biochar spread.
The summer study had “surprising” results, Wilson said. There was a 17 kg improvement in body weight in the pens with biochar as control pens – overall, a 4.5% improvement in efficiency.
“The wheels started turning,” Wilson said. “We asked ourselves ‘How could this happen?’ We think it’s related to mud. With biochar, there’s less mud, so the animals use less energy” to walk through the pen.
There was no difference in the amount of nutrients in the manure in the control vs. the test pens, though the biochar pens did seem to clean up better with less removal of soil.
When it comes to feeding biochar, Wilson said, “If we do want to feed it, we have to be cognizant of meat quality and safety issues.” Also, the “bottom line is it doesn’t seem to affect digestibility or performance. However, it also shows no sign of reducing methane.”
As a manure amendment, biochar had the unexpected benefit of increased performance and better pen integrity. What’s more, when applying manure with biochar to fields, the biochar will help improve the soil as well.
by Karl H. Kazaks
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