The recent debate on LinkedIn posts by Irina Gerry (Chief Marketing Officer, Change Foods, California, US) about methane production from livestock has started a vigorous discussion. Agri-industrialists, Nutritionists, Naturists, and many others took an active part in it. In one of her posts, she concluded that livestock is a leading contributor to methane and global GHGs. Its current attribute in global warming is about 20-30%. Methane increase global temperature 80 times faster than CO₂ in 20 years, or 27 times faster than CO₂ in a 100-year run. The UN has targeted 40-45% methane reduction by 2030, and reducing beef consumption is the easiest option according to her. Now, this is surprising that such an invisible natural process could contribute to a serious issue like global warming.

Enteric methane

The enteric fermentation process produced methane in ruminant animals such as cattle, goats, sheep, and buffalos. Ruminants are those that have 4 stomachs, specially designed to digest cellulosic biomass and generate energy. The fibrous biomass after digestion supplies ruminants with necessary proteins, fats, and carbohydrates to generate energy. The microbial consortium present in the stomach digest cellulosic biomass further to produce hydrogen and carbon dioxide. After the utilization of hydrogen by methanogenic bacteria, methane is produced, which is liberated into the environment majorly as cow burps.

Biogenic carbon cycle

Enteric methane plays important role in nature’s Biogenic Carbon Cycle. When enteric methane is produced, it remains in the environment for 12 years to maintain the atmospheric temperature. During these years, it is oxidized to form CO₂ and again enters into the food chain through primary producers. But, due to human interference with the growing population and demand for food and energy, this balance is broken.

Methane produced by one cow is negligible but when produced by billions of cows can impact on a great scale. Currently, it is measured to account for approximately 30% of total global methane emissions. Therefore, curtailing biogenic methane production could be one of the necessary steps to reduce the rapid progression of global warming. Does it mean that livestock farming should be stopped? Or find alternative ways to tackle this issue? Importantly we are at a state where all possible solutions need to be tried at their possible extent of implementation. This may or may not stop climate change but at least will help to bring down GHGs levels. With significant changes in livestock farming, we may be able to reduce the methane footprint of the agriculture sector.

Strategies to reduce enteric methane production

Types of feed, nutrient quality, animal health, environmental and geographic conditions, etc. highly influence enteric methane production. When cows are fed with grains as their major diet, they produce more methane than grass-fed cows. The strategies developed to reduce methane production from cow burps include, their diet change or fortification of the diet with additives to improve digestion and reduce methane production, cow breeding to obtain a breed with reduced enteric fermentation, Anti Methanogen Vaccines, Methane-capture wearables, utilization of methane digesters to trap methane produced from cow manure and utilize it as biofuel, etc.

A. Anti-Methanogen Vaccine (Wedlock, D. N. et al. 2013, Baca-González, V. et al. 2020):

The vaccines produced against enteric methanogens trigger antibody production in ruminants. These antibodies bind to methanogens and remove them from the ruminant’s digestive system helping to stop methane production. This concept is still in its early stages of development, but this could prove to be a permanent solution in the near future

B. Methane-capture Wearables (Linzey, C., & Linzey, A. 2021):

In this innovative idea, Zelp’s mask captures methane released directly from the cow’s mouth and flares it. This stops the liberation of enteric methane directly into the atmosphere. This wearable also helps to keep check of ruminants’ health and productivity.

C. Feed modification with additives:

1. 3-Nitrooxypropanol (3-NOP)

3-NOP is a chemical substitute for animal feed that has a similar chemical structure to Methyl-coenzyme M in Archaea. Methyl-coenzyme M reductase (MCR) enzyme plays an essential role in the final step of methane production by binding to methyl-coenzyme M. When 3-NOP is fed to ruminants it replaces methyl-coenzyme M and MCR binding site and stops methane production. In addition to this 3-NOP also oxidizes the Nickel atom present in the core part of the MCR enzyme and disables the whole enzyme from binding to methyl-coenzyme M. This oxidation reaction also produces nitrate, nitrite, and 1,3-propanediol and ultimately degrades 3-NOP in ruminant’s stomach. In general, 40-340mg of 3-NOP/Kg of dry matter intake (DMI) has been used in the research shown to reduce 23-39% methane production in ruminants.

In European Union, commercial 3-NOP manufacturer DSM (Koninklijke DSM N.V. or Royal DSM) patented (WO2012084629A1) their technology to reduce ruminant methane emission, and/or to improve ruminant performance as Bovaer®. With proven trials on large scale, this product has also received clearance from European Food Safety Association (EFSA) in the year 2021.

2. Algae Additives (Glasson C. R. et al. 2022):

With the need to reduce ruminants’ methane emissions, along with a 3-NOP-based solution there are others too coming to the market claiming more efficiency. One of that is Bromoform bioactive compound in extracted form or in whole seaweed-based animal feed that shows almost complete in-vivo methane elimination. A minimum of 1% inclusion level of specific seaweed in feed organic matter (OM) helps to reduce methane from cows and sheep at a significant level. Macroalgae genus Asparagopsis (A. taxiformis and A. armata) has proven to contain such specific inhibitors that reduce methanogenic activity. The key component from algae that contribute to this activity is halogenated methane analogue (HMA) or halomethane. The list of HMA analogue components found in Asparagopsis includes methane, bromochloromethane, dibromochloromethane, chloroform, bromoform, and iodoform. But, the most abundant HMA in Asparagopsis is bromoform.

Mechanism of HMA-

The general reaction carried out by rumen hydrogenotrophic methanogenic archaea involves the conversion of CO₂ to Methane through the Wolfe cycle (Thauer, R. K. 2012). 

CO₂ + 4H₂ → CH₄ + 2H₂O

Bromoform acts as an anti-methane bioactive compound by blocking the action of key metalloenzymes of the Wolfe cycle. Two essential steps for methane production carried out during the Wolfe cycle are catalyzed by coenzyme M methyltransferase (with a cobalamin prosthetic group) and methyl coenzyme M reductase (MCR) (with nickel tetrapyrrole as a prosthetic group; syn. cofactor F430). Both enzymes are susceptible to competitive and/or oxidative inhibition. The well-discussed mode of action of HMAs in ruminants is competitive binding with coenzyme M methyltransferase and inhibition of methyl transfer in methanogenesis. Whereas halogenated alkanes also block the activity of methyl coenzyme M reductase that catalyzes the final and rate-limiting step of methane production same as explained in the case of 3-NOP.

Drawbacks-

However, the use of HMA bioactive containing seaweed feed for ruminants is always questioned due to their potential carcinogenic and ozone-depleting effects. But it is also discussed by many that both the concerned issues have very negligible impact to consider it as harmful either to human health or leading to the destruction of the ozone layer.

In addition to reducing methane gas production, macroalgae are rich in essential vitamins, minerals, and other nutrients, making them a great addition to any cow’s diet. They are also high in dietary fiber, which helps to prevent digestive disorders and improve the overall health of cows.

Leading Innovators-

Some of the well-known innovators in the sector of seaweed-based feed additives for the reduction of cows’ methane burps are Mootral, Blue Ocean Barns, Symbrosia, Rumin8, Alga Biosciences, Volta Greentech, FutureFeed, CH4 Global, Sea Forest, Greener Grazing, Primary Ocean, The Seaweed Company, Seastock, Seascape Restorations, Agolin.

3. Other Natural ingredients:

Various traditional, as well as newly invented natural solutions for methane reduction in cow burps, include a variety of materials. Many essential oils such as linseed, and extracts that may or may not be scientifically proven have shown applications in methane reduction. This material list includes witchbrew, lemongrass, chestnut, tannins, coconut, garlic extract, cotton oil, wild carrot, coriander seed oil, citrus extracts, ozonated water, green tea and oregano. They are amongst the most effective additives for methane mitigation. Apart from this, adding fats to the cow’s diet offers a promising solution for reducing methanogenesis, without having a significant negative impact on other functions of the rumen.

Conclusion and Future Prospects:

A variety of solutions are available to reduce cow burp and only some of them will prove their potential in near future. In addition, every country’s policy to tackle the issue related to its own carbon footprint is need to be explored. Strong decisions and measures helping toward carbon neutrality need to be pursued.

One example from this category would be the recently flashed news about the New Zealand Government’s implementation of a new tax regime for farmers to reduce greenhouse gas emissions by 10% over the next decade. In this farmers would be taxed for their farm animals as a part of the Government’s commitment to reduce the country’s greenhouse gas emissions to net zero by 2050. The same tax would be expected to raise a high amount of funds that will be made available to support farmers to transition to more sustainable farming practices. Overall, this could potentially set an example for other countries to follow and start investing in better practices to reduce their emissions in the long run. 

Reference:

Wedlock, D. N., Janssen, P. H., Leahy, S. C., Shu, D., & Buddle, B. M. (2013). Progress in the development of vaccines against rumen methanogens. animal, 7, 244-252.

Baca-González, V., Asensio-Calavia, P., González-Acosta, S., Pérez de la Lastra, J. M., & Morales de la Nuez, A. (2020). Are vaccines the solution for methane emissions from ruminants? A systematic review. Vaccines, 8(3), 460.

Linzey, C., & Linzey, A. (2021). Masking the Problem. Journal of Animal Ethics, 11(2), v-vii.

Glasson, C. R., Kinley, R. D., de Nys, R., King, N., Adams, S. L., Packer, M. A., … & Magnusson, M. (2022). Benefits and risks of including the bromoform containing seaweed Asparagopsis in feed for the reduction of methane production from ruminants. Algal Research, 64, 102673.

Thauer, R. K. (2012). The Wolfe cycle comes full circle. Proceedings of the National Academy of Sciences, 109(38), 15084-15085.