U.S. Agriculture--Can It Become Greenhouse Gas [GHG] Negative?
In Nov. 2024, The Council for Agricultural Science and Technology [CAST] issued a report titled Potential for U.S. Agriculture to Be Greenhouse Gas Negative. The report, compiled and issued at the request of the U.S. Farmers & Ranchers in Action [USFRA], outlines how combining reduced GHG emissions from some agricultural activities with increased carbon [C] sequestration in others could result in a negative GHG emission U.S. agriculture sector.
A few points about the importance of GHG emissions are needed so that the contents of the above-linked report can be fully understood. They are as follows.
• GHG’s are gases that trap or absorb heat in the atmosphere. In so doing, they raise the surface temperature of the planet, and this results in the greenhouse effect.
• The five major GHG’s in order of abundance in the Earth’s atmosphere are: 1) water vapor [persists in the atmosphere for only a few days], 2) carbon dioxide [CO2–enters atmosphere from human activities such as burning of fossil fuels]–it can be sequestered when absorbed by plants and remains in crop residues; 3) methane that is emitted from production and transport of fossil fuels, livestock, and decaying organic matter–accounts for a significant portion of global warming, second only to CO2; 4) nitrous oxide that is emitted during agricultural and industrial activities; and 5) flourinated gases that are emitted from household, commercial, and industrial activities.
• The increase in the release of GHG’s due to human activity is considered the cause of increased and increasing global warming and climate change.
• CO2 accounts for the vast majority of GHG’s, and is responsible for the majority of global warming. That is why its increased production and sequestration are deemed important in the abatement of global warming and climate change.
The above-linked report identifies five major areas that offer opportunities to reduce the C footprint of agriculture so that emission of GHG’s from agricultural activities is diminished. They are:
1. Soil C management involves the sequestration of C into the soil, and this means that producers must adopt regenerative production practices that include reduced tillage, crop diversity, continuous soil cover [includes cover crops], and integration of livestock into cropping systems.
2. Nitrogen [N] fertilizer management which will likely involve modification of the rate, form, time, and/or placement of N fertilizer. The goal of this more precise N management is a reduction in nitrous oxide emission to the atmosphere, with the return to the producer being reduced N fertilizer costs and increased N use efficiency.
3. Animal production and management, which is linked to the release of methane to the surrounding air. Changes will involve type of feeding system for ruminants, the way manure is handled and disposed of, and forage/feed quality provided to livestock.
4. Improving crop production efficiency through improved genetics of crop plants, to include a better understanding of the genetics x environment x management interaction. This will also include more attention to genetic resistance to pests in crop plants in order to reduce the C footprint associated with the production and application of pesticides. The challenge with this approach is ensuring the economic value of adopting practices that reduce a crop’s C footprint.
5. More efficient energy use in agriculture, which will impact all phases of the agricultural sector. Energy use in all agricultural sectors is intensive, and most of this use is directly related to fossil fuels. Thus, replacing the fossil fuel energy source with fuels from renewable sources represents a large step in potentially reducing GHG emissions. Again, producers must be assured that adoption of alternative/renewable energy sources will not negatively affect their profitability.
There is no doubt that energy use in agriculture impacts GHG emissions, and the above opportunities should be considered to reduce agriculture’s C footprint. Thus, the answer to the question posed in the title of this article is YES. Altering the form of energy sources used in agricultural enterprises will require investments from both the public and private sectors to ensure the development and implementation of alternative energy sources that can be used in the production of agricultural inputs and at the farm level.
Composed by Larry G. Heatherly, Apr. 2025, larryh91746@gmail.com