Details in the Dirt.

30.11.23 | Jakob Tresch

Welcome to our deep dive into the world of agricultural emissions and their impact on the environment. In recent years, the conversation around carbon footprints has extended beyond factories and urban settings to the very heart of our food supply – the farms. This post aims to unravel the complexities behind agricultural emissions, focusing on what happens on a farm and how the most commonly known datasets are created. We will explore the key contributors to greenhouse gases (GHGs) at the farm level. Let’s begin by understanding the crucial elements that matter at the farm level.

What Matters at the Farm Level?

Let’s first have a look at the emissions on the farm level. According to the GHG protocol (Link), relative contributions of agricultural sources are split up as follows.

As you can see above two two-thirds of the emissions are made up of Fertilizer and Enteric Fermentation.

  • Enteric Fermentation: Enteric fermentation is a natural digestive process that occurs in the stomachs of ruminant animals, such as cows, sheep, goats, and deer. These animals have a unique stomach with multiple compartments, one of which is the rumen. The rumen hosts a complex mix of microorganisms, including bacteria, protozoa, and fungi, which assist in breaking down and fermenting plant-based feed, particularly fibrous materials like grass and hay.

    During this fermentation process, one of the byproducts produced is methane (CH4), a potent greenhouse gas. The methane is primarily released into the atmosphere when the animal belches. This release of methane is a significant concern, as methane is far more effective than carbon dioxide (CO2) at trapping heat in the atmosphere, despite having a shorter atmospheric lifespan.

    Efforts to reduce emissions from this process involve altering animal diets to reduce fermentation or improve feed efficiency, breeding for animals that produce less methane, and exploring feed additives that can reduce methane production by altering the microbial population in the rumen.

  • Fertilizers: Fertilizers are substances used in agriculture to provide nutrients to plants, enhancing their growth and productivity. They can be organic, derived from natural sources like compost, manure, and bone meal, or inorganic, made from synthetic chemicals. The primary nutrients provided by fertilizers are nitrogen (N), phosphorus (P), and potassium (K), often referred to as NPK. The impact of fertilizers on greenhouse gas emissions in agriculture is significant and multi-faceted:

    • The most direct impact is the release of nitrous oxide (N2O), a potent greenhouse gas, during the process of nitrification and denitrification in the soil. These processes occur naturally as soil microbes break down nitrogen in fertilizers. N2O has a global warming potential of approximately 300 times that of CO2 over a 100-year period.

    • The production of synthetic fertilizers, especially nitrogen-based ones, is energy-intensive and often relies on fossil fuels, leading to carbon dioxide emissions.

    • Although less direct, the use of fertilizers can also influence methane emissions. For instance, increased plant growth due to fertilization can lead to increased organic matter in the soil, which under certain conditions, particularly in waterlogged soils like those in rice paddies, can increase methane production. This is also the main reason why the cultivation of rice contributes 10% to the overall emissions.

    • Excessive use of fertilizers can lead to nutrient runoff into water bodies, causing eutrophication. This process can result in algal blooms that deplete oxygen in the water, harming aquatic life. The decomposition of these algae emits methane and CO2.

      To mitigate these impacts, sustainable fertilizer management practices are essential. These include precision agriculture techniques to optimize fertilizer application, using slow-release fertilizers to reduce N2O emissions, incorporating organic fertilizers into soil management practices, and implementing crop rotation and cover cropping to improve soil health and reduce the need for synthetic fertilizers. Additionally, efforts to develop and use fertilizers with lower environmental impacts are ongoing in the agricultural sector

Assessing your Impact.

The main variable you want to consider to assess a farm’s impact is CO2 flux. In simple terms, CO2 flux encompasses both the release and absorption of CO2 in the environment on a farm. This includes:

  • Photosynthesis: Plants absorb CO2 from the atmosphere during the process of photosynthesis, which is a key mechanism through which CO2 is removed from the atmosphere.
  • Respiration and Decomposition: CO2 is released back into the atmosphere through the respiration of plants and soil organisms, as well as through the decomposition of organic matter.
  • Management Practices: Agricultural activities can influence CO2 fluxes. For instance, tilling the soil can release CO2, while practices like cover cropping or improved land management can enhance CO2 absorption.
  • Combustion of Organic Matter: Burning crop residues or other organic materials on farms releases CO2.

Because we see both emitting and absorbing factors it makes sense to also consider the carbon stock of a farm and calculate the CO2 flux.

Actual Data.

To give a rough outline of what data you need to collect we summed up some base factors (Link) that are needed for a calculation at the farm level:

  1. Land Use Information: This includes the size and location of the farm as well as the types of land use (e.g., cropland, grassland, forested areas). Historical land use changes, if any (e.g., forest conversion to cropland) should also be considered.
  2. Crop Production Data: Regarding the production you need to know the types and varieties of crops grown and yields for each crop type. Also relevant is any information on crop management practices (e.g., tillage methods, crop rotation schedules) and ideally dates of planting and harvesting.
  3. Livestock Information: As the impact of livestock is a big contributor, the information on your animals should be quite detailed. This includes the types and numbers of livestock (e.g., cattle, sheep, pigs). But also livestock management practices (e.g., grazing systems, feed types) and manure management details (e.g., storage methods, application to fields).
  4. Fertilizer and Soil Management: As mentioned above, fertilizers have quite an impact. You should know about the types and amounts of fertilizers used (both synthetic and organic), general soil management practices (e.g., no-till farming, use of cover crops), and ideally soil type and condition (e.g., organic carbon content).
  5. Energy Use: Data on fuel consumption for farm machinery and vehicles and electricity usage, including the source of electricity (e.g., grid, renewable sources) are also considered as well as the energy used for heating and cooling (e.g., in greenhouses, animal housing).
  6. Water Usage: Water consumption is often also reported and considered in a holistic analysis. Therefore irrigation practices and the amount of water used should be reported. Optional is a more in-depth analysis of the source of irrigation water.
  7. Pesticide and Herbicide Usage: Report on the types and amounts of pesticides and herbicides applied.
  8. Waste Management: Consideration of practices for handling and disposing of agricultural waste, waste recycling, and reuse practices.
  9. Agroforestry and Forestry Practices: Areas of farm woodland or agroforestry systems should be mentioned including the types of trees and age of stands.
  10. Carbon Sequestration Practices: Practices aimed at enhancing carbon sequestration (e.g., afforestation, use of biochar).
  11. Farm Infrastructure: Buildings and their uses (e.g., storage, livestock housing). including any materials used in construction, and any insulation or energy efficiency measures.
  12. Off-farm Activities: Depending on the scope of analysis transportation of goods to and from the farm and any processing activities that occur off the farm also need to be considered. However often the boundaries are set at the farm gate.

Collecting this data enables a detailed analysis of the farm’s carbon footprint, encompassing both direct emissions and indirect emissions. The assessment can also identify potential areas for emission reductions and enhanced carbon sequestration, guiding the implementation of more sustainable farming practices.

Wrap Up.

In conclusion, assessing a farm’s carbon footprint is a multifaceted endeavor that requires a thorough understanding of various factors, from livestock and crop management to the usage of fertilizers and energy. By gathering detailed data and employing scientifically robust methodologies, farmers can gain insights into their farm’s GHG emissions and identify strategies for reduction. As consumers increasingly seek transparency in their food sources, such comprehensive farm carbon assessments become ever more vital.