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| Fig. 1: Global methane monthly means as reported by the NOAA Global Monitoring Laboratory. [9] (Courtesy of NOAA) |
Our world is at a critical juncture concerning its future. While our climate has always experienced fluctuations, human activities, from the industrial revolution, until now, have contributed to an alarming rise in temperature changes. Every year, our world is moving closer to rising beyond 1.5°C in temperatures, with estimates from the IPCC finding that since 1850, global temperatures have risen between .8 and 1.3°C. [1] Much of this has come from greenhouse gas emissions (GHGs) stemming from our utilization of fossil fuels. In particular, methane, which has a shorter half-life of 8.6 years compared to 120 years from other GHGs like carbon dioxide, has a higher warming potential, with about 28-36 times that of carbon dioxide over 100 years. [2] These figures are alarming considering that from data in 2020, methane concentrations in the atmosphere are already at 1.89 ppm and increasing, and the gas constitutes 19% of the combined effective radiative alongside the other GHGs. [3] Given that higher concentrations of methane would constitute greater warming potential from it and other GHGs, its essential to examine sources contributing to the global aggregate.
To do this, we can start by taking a look at the global methane budget which shows China, Southeast Asia, America, South Asia, and Brazil account for more than 40% of the methane emissions, coming out to 270 teragrams (Tg) of CH4. [2] Of the total emissions in these regions, 60% come from human activities like cattle farming. [4] Given that activities like cattle farming contribute extensively to methane emissions, this report will take a closer look into emissions totals from cattle and then discuss potential mechanisms that can reduce this amount, given the high warming potential of methane.
Cattle farming is an integral part of the global economy. While cattle generate value for other industries, its evident that its biggest contribution is towards food. In 2018, 333 million tons of meat were produced, with 95% being available for consumption, resulting in an average of about 7% of the total global food mass. [5] Given the sizeable amount of meat production alone, there are considerable efforts across farms to keep up with the demand. For example, if we examine Denmark, which has 1.5 million cattle that account for 20% of total agricultural exports, this livestock contributes to 59% of all national methane emissions. [3] Breaking down this percentage even further, 76% of emissions from the cattle came from their ruminant digestive system, and 24% came from the degradation of manure stored in tanks or underneath animal holding areas. [3]
To quantify global methane emissions from cattle, a 2020 study conducted by the Australian National Environmental Science Program and Global Carbon Project found that there was a 314% increase from 31.8 Tg (26.5-37.1) in 1890 to 131.7 (109.6 - 153.7) Tg in 2019. [6] Between 1890 - 1949, emissions grew at 0.4 Tg annually, however, it skyrocketed to 1.1 Tg between 1950-2019 because of the rise in heads of cattle to keep up with global demands, as seen in Fig. 1. [6] Certain regions of the world are also hotspots for methane emissions and their patterns have shifted in favor of greater emission discharge concentrations. In the last decade, developing regions like South Asia, eastern China, tropical Africa, and Latin America had the greatest growth in emissions with about 5 kg per hectare per year, with South Asia uniquely experiencing the largest growth of about 50 kg per hectare per year. [6] This growth pattern is alarming for warming, especially considering that methane has greater warming potential than other GHGs.
Given the urgency of our climate and the growth of cattle populations globally, its integral to identify ways in which regions around the world, especially those that are developing, can decrease the methane emissions from cattle. Barriers like cost and accessibility of the resource are important to take into consideration because developing countries in emerging regions don't have generous amounts of excess capital available. One solution, which integrates seaweed into the diet of cattle, has shown promise in Bangladesh, including at the rural level.
To examine the effects of seaweed on emissions from cattle, a study was conducted at the Pranisheba Research and Development cattle farm in 2022 by the Department of Microbiology at Bangladesh Agricultural University. After injecting 5% of the G. tenuistipitata var strain of seaweed within the cattle's normal diet, within 10 days and several IOT-connected sensors, researchers measured a reduced methane volume from 48.30 to 41 ppm. [7] If we apply this 15% reduction in emissions to the greater aggregate, we could see a reduction in 20.2 Tg of methane annually. What's even more promising with seaweed is that other strains have also shown immense possibility in reducing methane generation from cattle. A group of researchers at Lithuania University, in 2022, injected 1% of Asparagopsis (red algae) into the diet of lactating cows and found that the bioactive bromoform, a naturally occurring organic compound in seaweed, reduced methane emissions by 67%. [8] When researchers injected 0.5% of Asparagopsis into the feed, they mapped a decrease in methane production ranging from 55 - 80%. [8] To top it all off, Asparagopsis didn't harm the cattle's health and instead, helped them enhance their weight gain over this 72-day study period. [8] While these strands of seaweed show promise, there still needs to be a closer examination of the effects on human health.
Cattle have contributed significantly to warming as they can emit up to 500 liters of methane daily, accounting for 3.7% of all greenhouse gas emissions. [8] As the cattle population accelerates to keep up with consumer and industry demand, methane emissions will only continue to increase without mechanisms to reduce them. Promising solutions include integrating strains of seaweed into the diet of cattle as its shown across month-long trials that certain strains can either inhibit methane production by cattle or reduce them significantly. Furthermore, seaweed is much easier to grow more cost-effectively in emerging markets like Bangladesh. Given its potential, its integral to further explore integrating promising seaweeds into cattle diets to help reduce methane generation for the future of our planet.
© Itbaan Nafi. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute, and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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