The beef and dairy industries have claimed that they can achieve carbon neutrality or climate neutrality by 2030-2050.1,2 How is this possible? What is the difference between carbon neutrality and climate neutrality? There are a wide variety of opinions regarding the current and future sustainability of animal agriculture. Will technology completely eliminate emissions from animal farming? Does buying animal products from local farms significantly lower emissions? Many false claims about this topic stem from misconceptions regarding the effects of greenhouse gases such as methane and nitrous oxide on global warming. In this post, we’ll look at these common questions and misconceptions in more detail.
Methane and nitrous oxide
It is difficult to assess how long emitted carbon dioxide remains in the atmosphere. Eventually, nature will absorb some of our emitted carbon dioxide. However, our emissions today will still increase atmospheric carbon dioxide concentrations long into the future.3 Methane and nitrous oxide remain in the atmosphere for a shorter period of time than carbon dioxide, however, they are much stronger greenhouse gases. Even though methane remains in the atmosphere for only 12 years, it leads to 25 times more warming than carbon dioxide over a 100 year period and 72 times more warming over a 20 year period. Eventually, methane reacts into the atmosphere and is turned into other greenhouse gases such as carbon dioxide and water vapour. Similarly, even though nitrous oxide remains in the atmosphere for 114 years, it leads to 298 times more warming than carbon dioxide over a 100 year period and 289 times more warming over a 20 year period.4
Animal agriculture is responsible for 27-37% of human-caused methane. Fossil fuels, landfills, and rice farms must also lower their methane emissions.5-7 However, methane is not the only problem related to animal agriculture. Even if we didn’t take into account methane emissions, and only considered processes that do non emit methane such as land-use change, feed production, and fertiliser production and use, animal foods still emit more per calorie or per unit protein than plants. Per unit protein, beef emits 9 times more non-methane greenhouse gases than tofu.8 In addition, approximately 65% of nitrous oxide emissions come from animal agriculture.7
Global warming potential
Carbon neutrality and climate neutrality may seem similar, but they have different meanings. Carbon neutrality is a state in which the net emissions of an industry are zero. Industries can achieve carbon neutrality by storing more emissions than they emit. This can be accomplished by directly lowering emissions or by buying carbon offsets, which support programs to sequester carbon somewhere else. Climate neutrality is a state in which the emissions from an industry are not causing further warming. Methane-emitting industries can misleadingly use the concepts of climate neutrality and global warming potential, to seem more sustainable than they actually are.
In the last section, I mentioned that methane is stronger than carbon dioxide by 25-72 times. These numbers refer to the global warming potential (GWP) of methane. The GWP represents how strongly a gas contributes to warming compared to carbon dioxide. Because greenhouse gases remain in the atmosphere for different periods of time, the GWP can be calculated for different time periods. GWP20 considers the short term effects of a greenhouse gas over a 20 year period. GWP100 considers the medium to long term effects of a greenhouse gas over a 100 year period. While making agreements to reduce greenhouse gas emissions, countries usually use GWP100 as opposed to GWP20.9 The Paris Climate Agreement used GWP100, but GWP100 does not capture the effects of methane and nitrous oxide very well. Climate change will have both serious short-term and long-term effects. So, we need to simultaneously focus our efforts on reducing effects in both time frames.
Because methane leaves the atmosphere relatively quickly, increasing emissions of methane leads to a linear increase in warming. If methane emissions are constant, then those emissions do not further increase warming. If methane emissions are reduced, warming reduces linearly. However, since carbon dioxide remains in the atmosphere for a relatively long period of time, warming increases exponentially as carbon dioxide emissions increase. If carbon dioxide emissions remain constant, warming increases linearly. If carbon dioxide emissions are reduced linearly, warming still increases, but slowly tends towards a constant value.10 The image below illustrates these concepts.
To take into account the unique effects of greenhouse gases, researchers developed an index called GWP*. GWP* is a slightly different calculation compared to the conventional GWP, but it shows the actual effect an emission will have on future warming.11 However, GWP* is only a useful indicator when looking at global emissions. Comparing emissions from individual countries using GWP* can be problematic. If countries that have historically emitted a lot of methane continue to emit the same high quantity, those emissions will not cause further warming. However, these emissions will maintain the concentration of methane already in the atmosphere. This situation is not carbon neutral, but climate neutral. Of course, climate neutrality is better than our current situation, but it is not enough. Instead, that country has a responsibility for lowering the methane concentration in the atmosphere that it previously caused, rather than just maintaining it. GWP*does not take this into account. Instead GWP*allows these countries to keep emitting as much methane as they used to without penalty. In contrast, countries that have not historically emitted a lot of methane, will likely emit more as they develop. GWP* would punish these countries for trying to achieve the same level of development that more developed countries have benefited from for a long period of time. Clearly, it is not fair to compare different country’s greenhouse gas emissions through GWP*.12
If the size of a cattle herd is constant and hence the associated methane emissions are constant, this herd will not cause more global warming than it has already caused in the past. In the UK and the US, the total number of cows raised is quite constant. However, globally the size of cattle herds are increasing, which leads to increased methane emissions, and hence increased warming.13 From the climates perspective, it doesn’t matter if methane comes from the United States, the United Kingdom, South Korea, Australia, or anywhere in between. GWP* ignores the opportunity available for animal agriculture to contribute to a reduction in warming. Because methane is removed from the atmosphere in a shorter time frame, we can quickly have an impact on the warming rate if we emit less methane. If we do this, there will be a longer period of time available to lower carbon dioxide emissions in other sectors.14 The livestock industry, which has historically emitted a lot of methane, has a responsibility to lower warming and undo previous damage instead of merely maintaining or increasing it.
Won’t technology eliminate animal agriculture’s emissions?
It is difficult to completely eliminate emissions from the food sector, based on the way it currently operates. However, we can potentially lower emissions from animal agriculture through improved technology and agricultural management practices.15 So would it be better to just invest in these technologies and practices instead of consuming less animal products? Developed countries typically intensively raise animals in factory farms, which reduces the emissions per animal. However, since factory farms increase the efficiency of supplying animal products, developed countries end up raising more animals and produce more animal-based foods. The overall impact of animal agriculture depends on both the efficiency and the quantity supplied. So increasing efficiency is not always a positive outcome, because it encourages livestock farming to expand, which leads to more animals, which in turn leads to more emissions and a higher net consumption of resources.16
Technologies are currently being developed to convert the methane emitted by animal agriculture into biogas and to better manage animal manure.17,18 In addition, feeding cattle seaweed (in particular the macroalgae Asparagopsis) based supplements may lower methane emissions arising from enteric fermentation (cow burps). However, this technology is not a silver bullet by any means and does not eliminate other types of emissions related to animal agriculture, such as deforestation, and fertiliser production and use. Approximately 60% of emissions from animal agriculture are not a result of enteric fermentation.19 So far, we don’t know enough about how these supplements will affect cattle health, the growth rate of cows, and the economics of the industry. In addition, seaweed supplementation can negatively affect cows digestion. For example, a recent trial showed that when Wagyu cows ate a seaweed based supplement, methane emissions only reduced by 22%. This reduction is much lower than previous experiments. Furthermore, cows that ate this supplement had a reduced appetite and hence ate 8% less food and were 9% lighter than those that didn’t.21 Until more research is available, our confidence about the global potential of this technology should probably be reserved.
It is also may be difficult to economically and sustainably supply the large quantities of seaweed that will be needed. It may be possible, but we don’t know enough yet to say for sure. Seaweed supplementation is expensive and may not be suitable for use in small farms and developing countries.22 In saying that, it is important to reduce emissions as much as we can through technology. All solutions are needed to address climate change. We would still be better off if farmers who decide to continue raising cattle all had access to these supplements. However, directly consuming less beef and dairy products would be more effective.8 Plant-based burgers or legumes will still have less of an impact on the environment than burgers from cows who were fed seaweed supplements. While we wait for technologies like this to potentially come to fruition, our beef and dairy consumption today is directly causing emissions. Moreover, if we continue to justify eating products from cows because of the potential future existence of this technology, we may become distracted from other important issues such as animal welfare, land use, and deforestation. It is possible to solve the problems caused by the animal agriculture to some extent with various band-aid solutions, but it is more efficient to solve the source of the problem directly. For example, rather than animal manure being turned into biofuel, it is much more efficient to convert plants or crop by-products into biofuels instead, because of the poor feed conversion ratio of animals.23 Similarly, it is more efficient to grow seaweed for human consumption rather than for cows.
Weren’t there a lot of wild ruminants back in the day?
12000-13000 years ago, the many wild ruminants that roamed the Earth emitted methane at a similar rate to today’s farm animals, via enteric fermentation.24 So why wasn’t the climate ruined back then? While this is an interesting observation, it is not very useful in the context of solving our current challenges. There are many differences between that timeframe and our situation today. For example, back then there was not a simultaneous large quantity of emissions coming from a range of industries. So, although the emissions from those wild ruminants did cause some warming, they did not singlehandedly lead to severe climate change. However, in in our current situation, we need to lower emissions as much as possible from all sectors to reduce the impacts of climate change.
In addition, in those times there was wide diversity of ruminants and other species, which had a positive effect on the environment. In contrast, the animals that we farm today are not biodiverse and do not serve other important roles in the environments. Due to the expansion of animal agriculture, the world’s biodiversity is actually decreasing. If we rewilded the land used by the livestock industry, then the wildlife population would slowly return. Lowering methane emissions from animal agriculture will not lead to a direct replacement of these emissions by wildlife.25,26 Wildlife only cause emissions via enteric fermentation. However, enteric fermentation is not the only emission source from the livestock industry. Animal agriculture produces more emissions and harms the environment in many ways, far exceeding any damage from wild ruminants. In future posts, I will discuss biodiversity loss, land use, and rewilding in more detail.
Does nature emit more methane than animal agriculture?
Natural sources of methane, such as wetlands and termites, emit more methane than livestock farming.27 So why should we focus on methane emissions from animal agriculture? For a long period of time, the methane emitted by nature achieved a balance with the methane removed from the atmosphere, leading to a more constant methane concentration. However, methane emissions from industries such as animal agriculture and the fossil fuel sector emit methane that exceeds this balance. The environment cannot remove this methane fast enough and so overall more methane accumulates in the atmosphere. We don’t need to achieve a situation where there are no methane emissions at all. Instead we need to maintain methane concentration at a safe level. We have little control over nature’s methane emissions, and the ecosystems and animals that emit this methane have other important roles to play for the environment. For example, wetlands maintain biological diversity28 and termites are found in many ecosystems on Earth. In contrast, we can control emissions from the livestock industry, and since animal agriculture does not have a critical role to play for the environment, it is much more practical and effective to focus on reducing those emissions.
What about the carbon stored within animal’s bodies?
If we reduced the population of the animals we farm (by not artificially breeding more into existence), would the release of the carbon within their bodies be a significant source of emissions? When an animal dies in nature, the nutrients in their body return to the soil and some of the carbon stored within their body is emitted into the atmosphere. But this is a one time only emission. In contrast, continuing to raise animals leads to a continuous source of emissions. The carbon stored in the current population of farm animals is less than the continuous stream of emissions caused by continuous animal farming over a extended period of time. Furthermore, only a small percentage of the nutrients within the crops that we feed to animals are actually stored in an animal’s body. Hence, if we didn’t harvest the plants that we feed to animals, they would store much more carbon than the animal itself. This is simply the law of conservation of mass. Storing carbon at lower ends of the food chain (such as in plants) is much more effective. Moreover, we would be able to store more carbon if we rewilded the land that is currently used for grazing or to grow animal feed.25
Doesn’t growing rice also emit methane?
Usually, when we grow rice, we flood a field with water. Since there is not a lot of oxygen in these wet conditions, bacteria release methane while breaking down organic matter. Rice cultivation represents 8-11% of human caused methane. This is about one third of the methane emissions from enteric fermentation and animal manure.27 We may be able to can lower methane emissions from rice through technology and other methods of farming.29 Unlike the livestock industry however, if we are able to remove the methane emissions from rice, we can effectively eliminate all emissions from that industry. We may decide that we would like to eat less rice because of the associated emissions, however, it is much more important to eat less animal products.
Is it more sustainable to eat locally produced food?
Are the many plant-based foods that are imported from other countries unsustainable? Is it always more sustainable to eat food from farms produced in our local area? Surprisingly, most emissions from animal agriculture do not come from burning fossil fuels and instead come from land use or are emitted directly on the farm. Emissions from transportation represent only 4.8% of all emissions from the food sector.30 Transporting and packing beef represents only 0.5-2% of the emissions associated with beef production.8
Transporting food by boat is relatively efficient and it emits 3.5-8 times less than road transportation and 20-50 times less than air transportation. The majority of emissions associated with food transport are actually domestic transport, rather than international transport. 81% of emissions from food transportation are related to transportation by road. In contrast, only 0.4% of emissions from food transportation are related to transportation by plane.30 Fortunately, we usually transport food by boat instead of by plane. So importing foods from other countries by ship is not really a big deal from the perspective of climate change.
One paper concluded that as Americans eat less animal products, the distance traveled by their food actually decreases. Furthermore, if Americans adopted a fully vegan diet, 50% of their diet could be sourced from farms within a 250 km radius of where they live.31 In addition, if Americans replaced red meat or dairy products with other meats or plant based substitutes for only one day per week (ie. a meatless monday), the emissions from their diet would be less than if they sourced all of their red meat or dairy products from a nearby farm.32
Of course, if we want to lower our emissions as much as possible, it is better to buy plants from farms in our local area. However, the type of food that we eat is far more important than where it is produced. Animal foods produced locally are typically more sustainable than imported animal food. Similarly, locally produced plant based foods are typically more sustainable than imported plant based foods. However, imported plant based foods are more sustainable than locally produced animal foods. We should first focus on what we eat. After that, focusing on where our food comes from is just the cherry on top. If you want to learn more about how to reduce your dietary emissions, check out this post.
Sources
1. Place SE, Mitloehner FM. Pathway to Climate Neutrality for U.S. Beef and Dairy Cattle Production. 2021.
2. Australian Good Meat. How will red meat be carbon neutral by 2030? 2021; https://www.goodmeat.com.au/blog/how-will-australian-red-meat-be-carbon-neutral-by-2030/.
3. Inman M. Carbon is forever. Nature Climate Change. 2008;1(812):156-158.
4. Scheutz C, Kjeldsen P, Gentil E. Greenhouse gases, radiative forcing, global warming potential and waste management—an introduction. In. Vol 27: SAGE Publications Sage UK: London, England; 2009:716-723.
5. Ripple WJ, Smith P, Haberl H, Montzka SA, McAlpine C, Boucher DH. Ruminants, climate change and climate policy. Nature climate change. 2014;4(1):2-5.
6. FAO. Reducing Enteric Methane for Improving Food Security and Livelihoods. 2016.
7. Steinfeld H, Wassenaar T. The Role of Livestock Production in Carbon and Nitrogen Cycles. Annual Review of Environment and Resources. 2007;32(1):271-294.
8. Poore J, Nemecek T. Reducing food’s environmental impacts through producers and consumers. Science. 2018;360(6392):987-992.
9. IPCC. Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press; 2013.
10. Lynch J, Cain M, Pierrehumbert R, Allen M. Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants. Environmental Research Letters. 2020;15(4):044023.
11. Allen MR, Shine KP, Fuglestvedt JS, et al. A solution to the misrepresentations of CO2-equivalent emissions of short-lived climate pollutants under ambitious mitigation. npj Climate and Atmospheric Science. 2018;1(1).
12. Rogelj J, Schleussner C-F. Unintentional unfairness when applying new greenhouse gas emissions metrics at country level. Environmental Research Letters. 2019;14(11):114039.
13. Food and Agricultural Organization (FAO). FAOSTAT: Crops and livestock products. 2023; https://www.fao.org/faostat/en/#data/QCL.
14. Bryngelsson D, Hedenus F, Johansson DJ, Azar C, Wirsenius S. How do dietary choices influence the energy-system cost of stabilizing the climate? Energies. 2017;10(2):182.
15. Grossi G, Goglio P, Vitali A, Williams AG. Livestock and climate change: impact of livestock on climate and mitigation strategies. Animal Frontiers. 2019;9(1):69-76.
16. Fry J, Neff R, Martin B, et al. A Response to Dr. Frank Mitloehner’s White Paper,‘Livestock’s Contributions to Climate Change: Facts and Fiction,’. 2016.
17. Font-Palma C. Methods for the Treatment of Cattle Manure—A Review. Journal of Carbon Research. 2019;5(2):27.
18. Chadwick D, Sommer S, Thorman R, et al. Manure management: Implications for greenhouse gas emissions. Animal Feed Science and Technology. 2011;166-167:514-531.
19. Gerber PJ, Steinfeld H, Henderson B, et al. Tackling climate change through livestock: a global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO); 2013.
20. Min BR, Parker D, Brauer D, et al. The role of seaweed as a potential dietary supplementation for enteric methane mitigation in ruminants: Challenges and opportunities. Animal Nutrition. 2021;7(4):1371-1387.
21. Meat & Livestock Australia. Effect of Asparagopsis extract in a canola oil carrier for long-fed Wagyu cattle. 2023.
22. Vijn S, Compart DP, Dutta N, et al. Key Considerations for the Use of Seaweed to Reduce Enteric Methane Emissions From Cattle. Frontiers in Veterinary Science. 2020;7.
23. Cassidy ES, West PC, Gerber JS, Foley JA. Redefining agricultural yields: from tonnes to people nourished per hectare. Environmental Research Letters. 2013;8( 3):034015.
24. Malhi Y, Doughty CE, Galetti M, Smith FA, Svenning J-C, Terborgh JW. Megafauna and ecosystem function from the Pleistocene to the Anthropocene. Proceedings of the National Academy of Sciences. 2016;113(4):838-846.
25. Garnett T, Godde C, Muller A, et al. Grazed and confused?: Ruminating on cattle, grazing systems, methane, nitrous oxide, the soil carbon sequestration question-and what it all means for greenhouse gas emissions. Food Climate Research Network (FCRN);2017.
26. Smith FA, Hammond JI, Balk MA, et al. Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget. Proceedings of the National Academy of Sciences. 2016;113(4):874-879.
27. Saunois M, Bousquet P, Poulter B, et al. The global methane budget 2000–2012. Earth System Science Data. 2016;8( 2):697-751.
28. Gibbs JP. Wetland Loss and Biodiversity Conservation. Conservation Biology. 2000;14(1):314-317.
29. Hussain S, Peng S, Fahad S, et al. Rice management interventions to mitigate greenhouse gas emissions: a review. Environmental Science and Pollution Research. 2015;22:3342-3360.
30. Crippa M, Solazzo E, Guizzardi D, Monforti-Ferrario F, Tubiello FN, Leip A. Food systems are responsible for a third of global anthropogenic GHG emissions. Nature Food. 2021;2(3):198-209.
31. Kurtz JE, Woodbury PB, Ahmed ZU, Peters CJ. Mapping US food system localization potential: The impact of diet on foodsheds. Environmental Science & Technology. 2020;54(19):12434-12446.
32. Weber CL, Matthews HS. Food-Miles and the Relative Climate Impacts of Food Choices in the United States. Environmental Science & Technology. 2008;42(10):3508-3513.