Potential for U.S. Agriculture to be Greenhouse Gas Negative

November 27, 2024

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Compiled by Jerry L. Hatfield, Ying Wang, Marty D. Matlock, and Charles W. Rice (CAST-Science) In 2020, U.S. Farmers & Ranchers in Action (USFRA) established an independent scientific working group to analyze the potential for U.S. agriculture to collectively reduce greenhouse gas (GHG) emissions, including the potential to achieve a state of negative emissions, or emitting fewer total GHGs than are sequestered.

Building on a 2019 report by the National Academy of Sciences, Engineering and Medicine titled “Science Breakthroughs to Advance Food and Agricultural Research by 2030,” the independent authoring group established by USFRA, consisting of 26 leading research scientists, identified current practices and emerging technologies with the most potential for reducing emissions. Their findings are based on a comprehensive analysis of scientific literature, computer simulations, and life cycle analysis estimates.

At USFRA’s request and with support from the Foundation for Food & Agriculture Research, the National Academy of Sciences appointed a six-person committee to review the report, assessing its clarity, organizational effectiveness, and scientific rigor.

The final report, “Potential for U.S. Agriculture to Be Greenhouse Gas Negative,” outlines how combining reduced GHG emissions from some agricultural activities with increased carbon sequestration in others could achieve GHG-negative agriculture. It also describes the research needed to help accomplish this.

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Executive Summary

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Transitioning towards a GHG negative agricultural production system does not mean the elimination of carbon; but rather the most efficient utilization of carbon in production of food, feed, fuel, and fiber required to sustain society. Carbon is foundational in agricultural systems because it is the currency that forms the basis for all living organisms. An overview of the carbon cycle in agriculture shows the intricacies in how it is transformed throughout the production of goods and linked to all aspects of production including inputs related to the energy to produce the crop, production and distribution of fertilizers and pesticides, post-harvest storage, and transport of crops to processing facilities (Figure E1).

GHG negative agriculture demonstrates how decisions in the ag-food supply chain could reduce GHG emissions or carbon-equivalent (CO2-eq) footprint.

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While creating a “greenhouse gas negative” U.S. agricultural production system would have a limited impact on total global GHG emissions, it would serve as a strong model for the world community. Reducing global agriculture’s net GHG by 50% (7,000 MMT CO2-eq) would impact worldwide emissions by more than 10%.

A GHG Negative Agriculture

The path toward a greenhouse gas negative agriculture is complex because the overall supply chain of food, feed and fiber is interrelated, yet affected by so many different variables like geography, weather, crop patterns, production, harvest practices, and more. Since agricultural production is comprised of many different systems — each with a variety of inputs — there are many opportunities to develop a path toward greenhouse gas negative systems.

Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the dominant greenhouse gases associated with agriculture. Over the past three decades, these GHG emissions have been increasing (Table 1) with CO2 up by 8.1% from 1990-2020, CH4 up by 16.9% and N2O up by 1.8% (USEPA, 2022). The challenge for agriculture is to reverse the trend with the goal of reducing emissions while enhancing the capability of different production systems to efficiently generate food, feed, fiber, and fuel.

Greenhouse gas negative agriculture represents the total of all GHG expressed as carbon dioxide equivalents (CO2-eq) to account for the difference in the global warming potential of the gases emitted from agriculture. For example, the global warming potential of CH4 is estimated at 30 times CO2 while N2O is 298 times CO2 over period of time. Globally, agriculture would need to sequester between 14,000 and 18,000 MMT CO2-eq to become greenhouse gas negative. For the U.S., the change would be approximately 600 MMT CO2-eq to offset emissions from all agricultural systems. To achieve this goal, there are practices that can be implemented ranging from carbon sequestration in the soil to adoption of precision nitrogen management practices. Agriculture has the opportunity and challenge to develop a path toward implementing practices that would achieve greenhouse gas neutrality.

Opportunity 1: Soil Carbon Management

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Opportunity 2: Nitrogen Fertilizer Management

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Opportunity 3: Animal Production and Management

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Opportunity 4: Crop Production and the Yield Gap

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Opportunity 5: Efficient Energy Use in Agriculture

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A Path to Greenhouse Gas Neutral Agricultural Systems

Implementing the practices, summarized here, could result in a GHG neutral or GHG negative U.S. agriculture; thus, providing a roadmap for the world.

Nothing, however, is simple. Agricultural systems are particularly complex with interactions between carbon, water, nitrogen, and energy across a spatial and temporal framework. Because weather, soil, field, and regional conditions constantly change, effective solutions for greenhouse gas reduction could vary year-over-year and across each planting-to-harvest season (Figure E3).

The summary of potential GHG reduction and carbon sequestration methods described in the previous sections point to opportunities within different sectors of the agricultural system. Soil carbon sequestration, nitrogen management, animal feed and housing management, manure management, and on-farm energy use offer the greatest potential areas to achieve greenhouse gas neutrality in agriculture. Figure E2 shows the potential reduction in emissions from agriculture from implementation of different practices (Matlock et al., 2023).

Implementation of current technologies and practices at the medium level of adoption falls short of achieving greenhouse gas neutral systems; however, aggressive adoption provides the opportunity for agriculture to more than offset its carbon footprint. Emerging practices enhance the ability of agriculture to further reduce its carbon footprint. (See Appendix Table A1 for detailed values for each practice.)

Based on the current state of scientific literature and a detailed assessment of the results, there is a wide range in the impact of a specific practice to reduce GHG emissions and contribute to greenhouse gas neutral systems. The range of impact on the expected efficacy of different practices at the medium adoption level is shown in Figure 2.

Increased investment in research should be directed toward those practices with the greatest impact and supported by a “practical systems approach” that provides producers with information about “how” a specific practice could impact their production system.

The barriers to achieving U.S. agricultures potential reduction levels are:

Adoption
Demonstration of impact across different parts of field and farming areas
Policy to support practice adoption
Technical support to assist producers in changing crop or animal production systems (Antle and Capalbo, 2023).

A more aggressive approach is needed to: 1) document the positive impact of practices on profitability and production resilience for seasonal weather changes and 2) develop tools to assist producers in transitioning to new practices. These include decision support systems to aid in evaluating the effectiveness of on-farm management (e.g., risk reduction and profit maximization) and new practices across growing seasons.

The potential of emerging technologies — artificial intelligence, machine learning and system-level computer simulation models that can assess production systems based on interactions among GHG emissions, production levels, environmental endpoints, economics, and carbon intensity — will continue to advance the evaluation of current and future scenarios across a wide range of settings.

These changes need to be at the farm-level where producers can see the effect on their operations rather than at aggregated scales where they can only see the general impact. For greenhouse gas neutrality to occur, the industry must understand that any change must be financially viable or profitable to the producer and fit within their management systems.

Frontier systems require investment into developing and implementing practices with a positive impact. For example, food waste is an emerging area of potential reduction, but the path toward implementing practices remains in the development stage (Nichols-Vinueza et al., 2023). Of primary importance in food waste is the loss before it leaves the farm gate. This could represent a large portion of the specialty crops (e.g., vegetables and fruit) with an estimate of nearly 14 million tons lost for various reasons (Nichols-Vinueza et al., 2023). While only a small part of agriculture’s overall carbon footprint, reducing these losses could provide much-needed produce to communities.

Any investment in frontier and emerging practices would achieve environmental (carbon reduction) goals and demonstrate how agriculture benefits society by proactively investing in technologies with multiple benefits. These practices are a first step. As innovation and exploration advance, other potential practices may emerge. For example, biological fixation of nitrogen for all crops could offset nitrogen fertilizer inputs or genetic material, that is more resilient to stress and leads to more efficient production in adverse weather conditions.

Developing greenhouse gas neutral-to-negative agricultural systems is a journey. It requires implementing practices with the potential of reducing GHG emissions while simultaneously increasing the profitability and resilience of the specific system. The value shown in Figure E2 and Appendix Table A1 for potential reductions are projections based on best-available information.

Much remains to be done in each commodity to realize this potential. Detailed research is needed to provide quantitative information for a range of climates, soils, production systems, and scale of operations. And, it must be evaluated for impact and barriers that limit adoption including financial, technological, and sociological constraints. READ MORE