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Less Gas with Lemongrass?


Burger King aims to reduce methane with modified cattle diet

In July 2020, Burger King launched the Whopper® hamburger with Reduced Methane Emissions Beef, which is sourced from cattle that are fed lemongrass (Cymbopogon citratus, Poaceae). The company claims that supplementing the cattle’s diet with lemongrass has the potential to reduce methane emissions from those animals by up to 33%.1,2

The “reduced-methane” patty debuted at select Burger King locations in Austin, Los Angeles, Miami, New York, and Portland, Oregon. The company, which has more than 18,000 locations in more than 100 countries and US territories,3 also plans to expand the effort to Latin America and Europe.1,2 As part of its campaign, Burger King released a video ad featuring a country jingle and a yodeling, guitar-playing boy who emerges from a cow’s “dairy air” singing, “When cows fart and burp and splatter, well, it ain’t no laughing matter….”4

Burger King’s initiative comes when some consumers are reducing meat consumption for the environment’s sake. Meat-sourcing companies like Burger King are under increased pressure to minimize their impacts on climate change. It is not clear how much Burger King hopes to reduce its environmental footprint or how much the “reduced-methane” Whopper will cost the company. However, customers reportedly will not have to pay more for the burger. This is not Burger King’s first effort to appear environmentally conscious: Under a partnership with Impossible Foods Inc., it also began selling the Impossible Whopper, a plant protein-based burger, in August 2019.2

Emission Control

According to the Food and Agriculture Organization of the United Nations (FAO), greenhouse gas emissions from agriculture, forestry, and fisheries have almost doubled over the past 50 years and could increase another 30% by 2050 without more efforts to reduce them.5

Livestock represent about 14.5% of all anthropogenic (i.e., from human activities) greenhouse gas emissions globally, and cattle represent about 65% of the livestock sector’s emissions. About 44% of livestock emissions are in the form of methane, an odorless, colorless, flammable gas that is the major component of natural gas.6 On average, a single cow emits between 70 and 120 kilograms of methane per year, and the world contains about 1.5 billion cattle.7

Although methane is much less abundant than carbon dioxide, and its lifetime in the atmosphere is about 12 years, which is much shorter than that of carbon dioxide,8 methane has a global warming potential (GWP) about 86 times that of carbon dioxide over a 20-year period. That means methane will cause about 86 times as much warming as an equivalent mass of carbon dioxide over 20 years.9

Some experts believe that reducing methane emissions may be the most effective way to combat climate change right now, and according to the FAO, the greatest potential for reducing emissions in cattle includes better feed additives and/or supplements and feeding techniques.6

Cause for Controversy?

While the importance of reducing emissions is apparent, Burger King’s latest effort has created some controversy. Some farmers called the video ad “condescending” and “hypocritical” and said they wished the company would find other ways to promote its initiative, while lifting the farmers up, not putting them down. Burger King said it intended to “shine a light on an issue that is important to the business and industry.”10

Some scientists also criticized the video ad for focusing too much on flatulence and not enough on eructation (belching).10 After all, according to some data, about 95% of methane emissions from cattle are released through eructation, not flatulence.11 While the video does mention “farts” more than “burps,”4 the word choices simply may be a product of what rhymes.

When the initiative launched, some scientists also refuted Burger King’s claims about the methane-reducing benefits of lemongrass. At the time, those claims were based on preliminary, unpublished research.12,13 But that research, which was funded by its parent company, Restaurant Brands International, and conducted by researchers at Universidad Autónoma del Estado de Mexico, has since been published in the peer-reviewed journal Animals.14

In the study, four treatments were evaluated: a control diet, 100 g/day of lemongrass “dry matter” plus a control diet, 365 g/day of chamomile (Matricaria chamomilla, Asteraceae) dry matter plus a control diet, and 365 g/day of garden cosmos (Cosmos bipinnatus, Asteraceae) dry matter plus a control diet. Of those, lemongrass had the largest effect on methane yield, with a reduction of 33%, according to the study.14

The cattle in the study were fed the treatment for only the last three to four months of their lives, which was questioned by some scientists.12,13 During that time, the cattle are in the finishing phase of their lives, when they typically are confined to feedlots or barns before slaughter. Importantly, a different study found that more than 75% of methane emissions over the cattle’s lifetime occurred before the finishing phase.15 A beef cow is typically between 18 and 24 months old at slaughter, so it emits methane while grazing in pastures for many months before the finishing phase. Therefore, it is important to evaluate ways to reduce methane emissions over the entire lifetime of the cattle, not just the last three to four months.12

“We did our study on the last three to four months of the life of the animals because that was the simplest way to validate the approach as proof of principle,” Burger King’s Chief Marketing Officer Fernando Machado was quoted as saying. “We always knew we had to expand the research to include different cattle, different feeds, longer term feed (beyond three to four months), among other variables.”13

Greener on the Other Side?

Burger King is continuing the studies with the researchers in Mexico and at the University of California, Davis (UC Davis).13 Initially, a study conducted by Ermias Kebreab, PhD, a professor in the Department of Animal Science at UC Davis, was not able to replicate the results of the study in Mexico. But Kebreab reportedly thinks that may be because the lemongrass used in his study was grown under different conditions and may have contained less tannins than the lemongrass used in the study in Mexico. He is planning a follow-up study that will use the same lemongrass.12

Kebreab was quoted as saying that “lemongrass contains essential oils and tannins, both of which have been shown to reduce methane emissions by modifying the [cattle’s] gut environment and inhibiting the microbes responsible for methane production.”16

Ruminants (cattle, sheep, goats, etc.) have a powerful digestive system that allows them to extract energy from fibrous plant materials better than other animals. That includes a stomach with four chambers, the largest of which is the rumen (hence, ruminant).12 The rumen is where most methane emitted by ruminants is produced.17

In the rumen, a group of microorganisms called methanogens produce methane as a product of normal fermentation. They are reportedly the only known microorganisms that can produce methane. Up to 12% of cattle’s energy intake is lost through methane production.17 So, finding ways to favorably affect the microbiome in the rumen can mean that cattle potentially retain more energy while emitting less methane.12

Burger King’s effort will not “solve the climate change problem in the short term, but it is a scalable finding that may allow change in the future,” the company said in a statement. “The majority of conversation around this announcement has been overwhelmingly positive.”10

The company hopes to convince other companies, like McDonald’s, to follow its lead. Significant potential exists to “drive wider industry improvement, so we are making our scientific research, learnings, and protocol formula publicly available in an open source manner to support this,” Machado was quoted as saying.1

In addition to lemongrass, other ingredients may also reduce methane yields in cattle (see sidebar). Meat producers could choose options that are most affordable for them, and if prices were imposed on emissions, then producers would be incentivized to adopt methane-reducing feed additives and/or supplements.12

It is important to realize, however, that methane-reducing feed addresses only part of the problem. For example, both synthetic fertilizers and decomposing manure left on pastures provide nitrogen to soil microbes, which turn that nitrogen into nitrous oxide,6,12 a potent greenhouse gas that causes significantly more warming than an equivalent mass of carbon dioxide.8 Processing and transportation of animal products also create emissions.6

Other improvements, therefore, also are needed, such as better manure management, breeding that would allow for smaller herds (fewer, more productive animals), and more regenerative agricultural practices.6 Still, Burger King’s latest effort may be a step in the right direction.

SIDEBAR: Other Feeds that May Bypass Gas

Researchers at the University of North Texas led by research professor Richard Dixon, PhD, have discovered ways to increase the production of tannins in alfalfa (Medicago sativa, Fabaceae) through genetic engineering. This may improve digestion in cattle and other ruminants. Though alfalfa is a good forage crop, the plant’s protein is broken down rapidly during fermentation, which can cause potentially lethal bloating and release of methane.18

“As such, ranchers must spend time and effort moving animals from field to field to vary their diet,” Dixon was quoted as saying. “But what if a rancher didn’t have to do that?... By engineering alfalfa to produce tannin in its stems and leaves instead of just its seeds, the alfalfa’s protein will be protected by the bound tannins, not breaking down so fast in the rumen and being better absorbed later in the digestion process.”18

A 2016 study found that seaweeds may be used as nutritious animal feed with positive effects on methane yields. When incubated with meadow hay in an in vitro rumen, five seaweeds — Ulva sp. (Ulvaceae), Laminaria ochroleuca (Laminariaceae), Saccharina latissima (Laminariaceae), Gigartina sp. (Gigartinaceae), and Gracilaria vermiculophylla (Gracilariaceae) — led to methane reduction. But, of those, only G. vermiculophylla decreased methane when incubated with corn silage. This shows the importance of the animals’ basal diet. The authors suggest that additional in vivo research should analyze the methane-reducing effects of seaweeds with different diets.19

In a 2020 study, Brahman-Angus steers were fed the red macroalgae Asparagopsis taxiformis (Bonnemaisoniaceae) at 0.05%, 0.1%, and 0.2% of feed organic matter for 90 days. Methane decreased up to 40% in steers that received 0.1% and up to 98% in steers that received 0.2% A. taxiformis. These steers also experienced significant weight gain improvements with no negative effects on daily feed intake or rumen function. The authors suggest that A. taxiformis, which contains multiple anti-methanogenic compounds, may have the potential to “revolutionize management” of methane emissions in the livestock sector.20

A 2019 study evaluated the ability of Mootral (Mootral SA; Rolle, Switzerland), a patent-pending natural feed supplement that contains garlic (Allium sativum, Amaryllidaceae) powder and bitter orange (Citrus aurantium, Rutaceae) extracts, to reduce methane in cattle. Each day for 12 weeks, Jersey and Holstein-Friesian cows received 500 grams of pellets containing 3% Mootral powder. From baseline, methane decreased by 38.3% in Jersey cows and 20.7% in Holstein-Friesian cows with Mootral.21


  1. Carman T. Burger King wants to combat climate change by helping its cows be a little less gassy. The Washington Post. July 14, 2020. Available at: Accessed October 1, 2020.
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  3. Restaurant Brands International Inc. 2019 Annual Report. Restaurant Brands International website. Available at: Accessed October 1, 2020.
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  6. Key Facts and Findings. Food and Agriculture Organization website. Available at: Accessed October 1, 2020.
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  10. US Farmers’ Beef with Burger King over Cow Fart Ad. BBC website. July 16, 2020. Available at: Accessed October 2, 2020.
  11. Hecht J. Well that Stinks! Reporters Blow Cow Farts Out of Proportion. Scientific American website. February 13, 2014. Available at: Accessed October 2, 2020.
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  13. Sternlicht A. Burger King’s Sustainable Whopper Only Reduces Methane Emission by 3% at Most, Scientists Say. Forbes. July 20, 2020. Available at: Accessed October 2, 2020.
  14. Vázquez-Carrillo MF, Montelongo-Pérez HD, González-Ronquillo M, Castillo-Gallegos E, Castelán-Ortega OA. Effects of three herbs on methane emissions from beef cattle. Animals. 2020;10(9):1671. doi:10.3390/ani10091671.
  15. Rotz CA, Asem-Hiablie S, Place S, Thoma G. Environmental footprints of beef cattle production in the United States. Agric Sys. 2019;169:1-13.
  16. Mock S. Less Windy Whoppers? Low-Methane Burger King Still Involves Some Hot Air. The Guardian. July 22, 2020. Available at: Accessed October 2, 2020.
  17. Hook SE, Wright ADG, McBride BW. Methanogens: Methane producers of the rumen and mitigation strategies. Archaea. 2010;2010:945785. doi:10.1155/2010/945785.
  18. UNT BioDiscovery Institute Team Develops Ways to Improve the Environmental Footprint of Alfalfa for Livestock [press release]. Denton, TX: University of North Texas; November 27, 2018. Available at: Accessed October 5, 2020.
  19. Maia MRG, Fonseca AJM, Oliveira HM, Mendonça C, Cabrita ARJ. The potential role of seaweeds in the natural manipulation of rumen fermentation and methane production. Sci Rep. 2016;6:32321. doi: 10.1038/srep32321.
  20. Kinley RD, Martinez-Fernandez G, Matthews MK, de Nys R, Magnusson M, Tomkins NW. Mitigating the carbon footprint and improving productivity of ruminant livestock agriculture using a red seaweed. J Clean Prod. 2020;259:120836.
  21. Vrancken H, Suenkel M, Hargreaves PR, Chew L, Towers E. Reduction of enteric methane emission in a commercial dairy farm by a novel feed supplement. Open J Anim Sci. 2019;9:286-296. doi: 10.4236/ojas.2019.93024.