Decarbonizing Agriculture

Part 2: How to Reduce Agricultural GHG Emissions

By Patrick Pelegri-O’Day

November 17, 2023

 A harvesting operation kicks up dust in rural Carroll County, Indiana. Original image from Carol M. Highsmith’s America, Library of Congress collection. Digitally enhanced by rawpixel.

In our last blog post, we provided an overview of the sources of greenhouse gas (GHG) emissions in U.S. agriculture. In this blog post, we build on that knowledge to examine ways to reduce GHG emissions. We look at general approaches to reducing each of the three main GHGs in agricultural production, then specific research-based strategies.

First, a few caveats. Agricultural production is only one part of the broader food system, and all parts are important, including what foods we eat and how much food we waste. This blog is focused on the U.S.; agricultural challenges and solutions are sometimes similar and sometimes different elsewhere. Overhauling agriculture is about way more than just GHG emissions: it’s about farmer livelihoods, nutritious food, biodiversity, water management, pollinator health, and much more. And finally, GHG emissions in U.S. agriculture is a very complex and challenging topic, so we’re not going to solve it all in one blog post. But here are some ideas.


As discussed in Part 1, the most significant sources of methane emissions from U.S. agriculture are enteric fermentation (cow digestion), manure management, and rice cultivation. Methane is produced by microbes breaking down organic material, which means that most high-level strategies for reducing it are to inhibit those microbes or change the material they have to break down.

Enteric Fermentation

Arndt et al. conducted a review of 425 peer-reviewed studies in 2021 and found seven strategies for emission reduction currently ready for implementation. Three of these strategies decreased methane emissions while increasing animal productivity: decreasing dietary forage-to-concentrate ratio, increasing feeding levels, and decreasing grass maturity. The authors found another four strategies that decreased methane emissions with no effect on animal productivity. These were the supplementation of oils and fats, oilseeds, electron sinks, and tanniferous forage.

One enteric fermentation reduction strategy that has garnered much attention in the press is the use of seaweed, e.g. Asparagopsis taxiformis, as a feed additive. A. taxiformis acts as a methane inhibitor in the rumen (one of the cow’s stomachs) and has been shown to decrease methane emissions by 80% or more when supplemented into cattle’s diet. While the results are encouraging, there is still a lot more work to be done before this technique is adopted at wide-scale.1

1. The Arndt et al. 2021 study questions the safety of the seaweed’s active ingredient, bromoform, for the animals while other studies such as one by Roque et al. 2021 found the seaweed additive was safe for the animals and for humans consuming the animal’s meat.

Manure Management

There are significant methane emissions from the manure of dairy cattle, pigs, and poultry. Beef cattle manure is also a source of methane emissions, although proportionally it emits a far larger amount of nitrous oxide.

When addressing manure management, one set of strategies relates to feed management, while another set of strategies is about treating the manure once it has been produced. Feed management strategies include avoiding excess dietary protein (which reduces nitrogen in manure), adding low levels of tannins (which shifts nitrogen excretion from urine to feces), and reducing the amount of fermentable organic matter excreted (Gerber et al. 2013).

Our strategies for reducing methane emissions from manure once it is excreted generally take advantage of two characteristics of the gas: 1) methane is produced in anaerobic environments, or environments lacking oxygen, and 2) methane becomes CO2, a much less potent GHG, when combusted.

Following these characteristics, drying manure is one effective way to reduce methane emissions. Drying facilitates the transition toward aerobic (oxygen-rich) conditions. Under aerobic conditions, organic matter decomposition tends to produce carbon dioxide instead of methane, which is less potent as a greenhouse gas. This is most commonly practiced on poultry farms (EPA 2022).

In addition, various methods are used to capture the methane produced from microorganisms breaking down manure then combust that methane gas to make use of it as a fuel and to convert it from CH4 to CO2. The feasibility of methane capture strategies depend on land, labor, and capital resources of the farm. The top solution according to the EPA is anaerobic digesters (EPA 2022).

Rice Cultivation

The typical method of rice production involves continuous flooding of the fields in which rice is cultivated, called paddies. This creates the anaerobic conditions that are ideal for methanogenic microbes to break down organic material from the rice plant and produce methane (Williams 2021).

The principal strategies to reduce methane emissions from rice paddies involve introducing more oxygen into the growing system to disrupt the activity of these methanogens. This can be done by seeding the rice into a dry field, drawing down the water levels mid-season, or alternating wet conditions and dry conditions (Adhya et al. 2014).

These strategies can have great benefits. In one case study in Tamil Nadu, India, methane emissions fell by over a quarter, water use decreased by 37%, and farmers saw 4-26% higher yields by applying the alternate wetting and drying technique (Adhya et al. 2014).

There are also important limitations. In regions with a strong monsoon season, drawing down water levels may not be possible. In some studies, intermittent drying reduced yields (Neue 1993). Intermittent drying may increase N2O emissions, offsetting the benefits of reducing CH4 emissions. And dry seeding can be done mechanically, potentially removing jobs from the production system (Adhya et al. 2014).

Nitrous Oxide

As explained in Part 1 of this series, nitrous oxide is a byproduct of nitrification and denitrification processes. The general strategies for reducing nitrous oxide emissions are to 1) reduce the amount of nitrogen introduced into the system and 2) inhibit nitrification and/or denitrification.

Most N2O emissions come from the denitrification process, which occurs in anaerobic conditions. One way to limit denitrification is therefore to minimize anaerobic conditions where large amounts of nitrogen are deposited.

Cropland Soils

Nitrogen (N) is a critical nutrient for crops. Plant growth is often limited by nitrogen availability and to make croplands more productive, farmers apply nitrogen. Whereas historically and in non-industrial systems this was done with compost, intercropping or crop rotations, and manure, contemporary industrial agriculture typically involves applying synthetic fertilizers, which can deliver large quantities of concentrated nitrogen.

Regardless of the source of nitrogen, one strategy to mitigate N2O emissions from cropland soils is to optimize the amount of nitrogen applied to the crops’ needs. Unfortunately, the optimal amount can vary widely, such as 100lb of N per acre in the U.S. corn belt (Iowa State). However, the benefits for achieving this optimal fertilizer application rate is high: yields are diminished both above and below that optimal rate, and excess nitrogen exacerbates global warming, imposes unnecessary expenses on farms, and contaminates local waterways (Ordóñez et al. 2021).

While a range of universities and companies have focused on optimizing nutrient application through advanced techniques like modeling, infield sensors, and remote sensing, the primary impetus for adopting precision nutrient management has often been water quality regulations rather than emission concerns. Traditionally, precise nutrient management techniques have seen limited adoption, as fertilizers have been perceived as a cost-effective way to ensure high yields. However, recent geopolitical events, notably the war in Ukraine, and the subsequent sharp increase in the cost of synthetic fertilizers, have heightened awareness around the efficiency of fertilizer use.

In addition to optimizing N application, another strategy for reducing N2O emissions is inhibiting the nitrification and denitrification processes. A review of 140 datasets found a reduction potential of N2O emissions of approximately 35% after the application of inhibitors such as DCD and DMPP (Ruser and Schulz 2015). The same study found no long-term disruption of beneficial soil microbiota.

Finally, because denitrification occurs in anaerobic conditions, farmers can reduce N2O emissions from denitrification by managing irrigation to avoid waterlogging soils. For example, a study in California found that drip irrigation systems reduced N2O emissions by over 50% compared to surface gravity irrigation (Deng et al. 2018).

Grazed lands and manure management

N2O emissions in grazed lands primarily come from livestock manure and feces. Strategies to reduce N2O emissions in grazed lands can be categorized into nitrification inhibitors, grazing management, diet manipulation, and use of vegetation.

As in cropland soils, nitrification inhibitors can be highly effective. A 2023 meta-analysis found that nitrification inhibitors reduced N2O emissions from urine patches by 50% or more (Soares et al. 2023).

One common process in grazed lands that leads to N2O emissions is when soil compaction by grazing animals and wet soil create a moist, anaerobic environment that promotes denitrification. An effective strategy for interrupting this process is limiting the amount of time the livestock spend on the pasture during the rainy season (Luo et al. 2013).

Similar to reducing CH4 emissions from livestock, feed management can also reduce N2O emissions. In this realm, it is worth highlighting some important interactions with feed strategies that affect the emission of both gases. Increasing nutrient digestibility reduces CH4 emissions but can cause an oversupply of N to the animals, which can result in additional N2O emissions from their excrement. Decreasing dietary protein can lower N2O emissions, but can increase CH4 emissions and can lower the weight gain of the livestock. While feed management is a powerful lever, it must be applied in a well-informed way to achieve the desired results holistically. Gerber et al. (2013) provide an excellent review of the subject.

Reducing N2O emissions from manure can be achieved through many of the strategies we have already discussed: nitrification inhibitors, feed management, and matching fertilizer rates (when manure is used as a fertilizer) to plant N needs (Montes et al. 2013).

Carbon Dioxide

Fuel Use

The largest sources of CO2 emissions from farm operations in the United States are heavy machinery and irrigation (Lal 2004). We did not find comprehensive assessments of farm electrification in the United States, but one study highlighted the potential for farm electrification and the current technical barriers (Clark 2018). The Inflation Reduction Act allocated $13 billion to support clean energy infrastructure for rural America through USDA Rural Development programs, including on farms, so we expect to see improvements in this area (USDA 2023).

In regions like the western United States, where agriculture heavily depends on irrigation, the carbon footprint associated with water use is a significant contributor to farms’ emissions. The process of moving and pressurizing water for irrigation demands substantial energy, typically sourced from electricity and, in some cases, directly from burning fossil fuels like diesel and natural gas to power pumps. The carbon intensity of these energy sources—electricity, diesel, and natural gas—largely determines the CO2 emissions linked to irrigation. Electrifying and switching to carbon-free sources of electricity is the most important way to eliminate carbon dioxide emissions associated with irrigation.

Soil Carbon

Several common agricultural practices such as tillage and leaving the ground bare after harvest can lead to significant release of CO2 into the atmosphere. When soil is tilled, it disrupts the soil structure, exposing organic matter to oxygen. This exposure accelerates the decomposition of organic matter by soil microorganisms, a process that releases stored carbon in the form of CO2. The more intensive the tillage, the greater the disruption and, consequently, the more CO2 is released.

Carbon sequestration in soils is a large and fascinating topic. A wide range of estimates of the potential exists, as do considerations about the durability of that carbon sequestration and the practical barriers and opportunities to implement carbon sequestering practices.

There is significant activity at the state and federal level to investigate and increase soil carbon sequestration, such as the federal Environmental Quality Incentives Program (EQIP), Conservation Innovation Grants (CIG), and the California Healthy Soils Program.


Opportunities to reduce GHG emissions in agriculture abound. While our focus has been on U.S. agricultural emissions in this blog series, it’s crucial to recognize that the agricultural sector operates within a larger food system where each component holds significance. Water, biodiversity and pollinator health, farmer livelihoods, soil health, human health—all of these are vitally important.

At Klimate Consulting we seek to make the science clear and enable actionable steps for organizations’ pursuit of their sustainability goals. In the agriculture context, that will often mean seeking solutions that achieve as many sustainability goals in parallel as possible, and when tradeoffs occur between different sustainability metrics, making those tradeoffs deliberately and avoiding unintended consequences. Our commitment remains steadfast—to contribute to the ongoing discourse and actions aimed at sustainable and resilient agricultural practices.


  1. Arndt, C., Hristov, A. N., Price, W. J., McClelland, S. C., Pelaez, A. M., Cueva, S. F., Oh, J., Yu, Z. (2021). Strategies to Mitigate Enteric Methane Emissions by Ruminants – A Way to Approach the 2.0°C Target. agriRxiv.
  2. Roque, B. M., Venegas, M., Kinley, R. D., de Nys, R., Duarte, T. L., Yang, X., Kebreab, E. (2021). Red Seaweed (Asparagopsis taxiformis) Supplementation Reduces Enteric Methane by Over 80 Percent in Beef Steers. PLOS ONE.
  3. Gerber, P.J. et al. (2013). Technical Options for the Mitigation of Direct Methane and Nitrous Oxide Emissions from Livestock: A Review. Animal.
  4. EPA (2022). Practices to Reduce Methane Emissions from Livestock Manure Management.
  5. Williams, M. (2021). Reducing Methane Emissions from Rice Cultivation.
  6. Searchinger, T., Adhya, T. K. et al. (2014). Wetting and Drying: Reducing Greenhouse Gas Emissions and Saving Water from Rice Production. World Resources Institute.
  7. Neue, H. U. (1993). Methane Emission from Rice Fields. BioScience.
  8. Iowa State University. Finding the Maximum Return To N and Most Profitable N Rate.
  9. Ordóñez, R. A. et al. (2021). Insufficient and Excessive N Fertilizer Input Reduces Maize Root Mass Across Soil Types. Field Crops Research.
  10. Kee, J., Cardell, L., Zereyesus, Y. A. (2023). Global Fertilizer Market Challenged by Russia’s Invasion of Ukraine. USDA Economic Research Service.
  11. Gilsanz, C. et al. (2016). Development of Emission Factors and Efficiency of Two Nitrification Inhibitors, DCD and DMPP. Agriculture, Ecosystems & Environment.
  12. Ruser, R., Schulz, R. (2015). The Effect of Nitrification Inhibitors on the Nitrous Oxide (N2O) Release from Agricultural Soils—A Review. Journal of Plant Nutrition and Soil Science.
  13. Deng, J. et al. (2018). Changes in Irrigation Practices Likely Mitigate Nitrous Oxide Emissions From California Cropland. Global Biogeochemical Cycles.
  14. Soares, J. R. et al. (2023). Mitigation of Nitrous Oxide Emissions in Grazing Systems Through Nitrification Inhibitors: A Meta-Analysis. Nutrient Cycling in Agroecosystems.
  15. Luo, J. et al. (2013). Nitrous Oxide and Greenhouse Gas Emissions from Grazed Pastures as Affected by Use of Nitrification Inhibitor and Restricted Grazing Regime. Science of The Total Environment.
  16. Montes, F. et al. (2013). Mitigation of Methane and Nitrous Oxide Emissions from Animal Operations: II. A Review of Manure Management Mitigation Options. Journal of Animal Science.
  17. Lal, R. (2004). Carbon Emission from Farm Operations. Environment International.
  18. Clark, K. (2018). Farm Beneficial Electrification: Opportunities and Strategies for Rural Electric Cooperatives. EnSave, Inc.
  19. USDA (2023). Record Demand to Advance Clean Energy in Rural America Through President Biden’s Investing in America Agenda.


At Klimate Consulting, we understand the intricacies of decarbonizing agriculture and the broader implications for food systems. We provide research-based insights and strategic guidance to organizations aiming to navigate the complexities of sustainability. To learn more about how we can help you achieve your organizational goals, get in touch or book a free consultation with us.