> For the complete documentation index, see [llms.txt](https://help.fielddoc.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.fielddoc.org/resources/models/comet-planner.md). # COMET Planner [COMET-Planner](https://comet-planner.com/) (CarbOn Management Evaluation Tool) is a web-based greenhouse gas evaluation tool that provides estimates of the carbon sequestration and greenhouse gas emission reduction potential of conservation practices. The tool is a collaboration between the [USDA Natural Resources Conservation Service (NRCS)](https://www.nrcs.usda.gov/) and [Colorado State University](https://www.colostate.edu/). Emission reduction coefficients (ERCs) were derived using a sample-based metamodeling approach with [COMET-Farm](https://comet-farm.com/), which employs USDA entity-scale greenhouse gas inventory methods. COMET-Farm uses the DayCent biogeochemical process model to simulate soil carbon dynamics and greenhouse gas fluxes. More information on quantification methods can be found in the [COMET-Planner Report](https://storage.googleapis.com/comet-planner-public-assets/fiftyStates/pdfs/COMET-PlannerReport.pdf). #### Calculation Methodology COMET-Planner calculates greenhouse gas emission reductions by multiplying practice-specific emission reduction coefficients (ERCs) by the implementation acreage. ERCs represent the average annual carbon sequestration or emission reduction per acre for a given conservation practice. ``` # Core emission reduction calculation emission_reduction = area_acres * emission_reduction_coefficient # Emission reduction coefficients (ERCs) are expressed in: # - metric tons CO2-equivalent per acre per year (MT CO2e/ac/yr) # Example calculation: co2e_reduced = acres_implemented * erc_mt_co2e_per_acre # Total GHG impact combines multiple gases: total_co2e = co2_reduction + (n2o_reduction * 298) + (ch4_reduction * 25) # Where 298 and 25 are Global Warming Potentials (GWP) # relative to CO2 over a 100-year time horizon ``` #### DayCent Biogeochemical Model Emission reduction coefficients are derived from the DayCent model, a process-based biogeochemical simulation that calculates carbon and nitrogen cycling in agricultural soils. DayCent operates at a daily time step and simulates soil organic matter dynamics, plant growth, and greenhouse gas emissions. ``` # DayCent simulates: # - Soil organic carbon (SOC) changes to 30 cm depth # - Direct N2O emissions from nitrification/denitrification # - Indirect N2O from nitrogen leaching and volatilization # - CH4 emissions (for applicable practices) # Soil carbon change calculation delta_SOC = C_inputs - C_losses # Where: # C_inputs = plant residues + manure + amendments # C_losses = decomposition + erosion # N2O emissions calculation (simplified) N2O_direct = f(soil_N, moisture, temperature, soil_type) N2O_indirect = (N_leached + N_volatilized) * EF_indirect # Where EF_indirect = IPCC Tier 1 emission factor ``` #### Major Land Resource Areas (MLRAs) Emission reduction coefficients are regionalized using USDA Major Land Resource Areas (MLRAs)—multi-county geographic units with similar physiography, geology, climate, soils, and land use patterns. This approach accounts for regional variation in soil carbon sequestration potential and greenhouse gas dynamics. Although ERCs are reported by county in this tool, the underlying modeling was conducted at the MLRA scale. Coefficients may vary between irrigated and non-irrigated land, and between humid and arid climate zones. #### Greenhouse Gases and Global Warming Potential COMET-Planner reports emissions in CO₂-equivalents (CO₂e), which normalizes different greenhouse gases based on their global warming potential (GWP) over a 100-year time horizon. | Greenhouse Gas | Chemical Formula | GWP (100-year) | Primary Sources | | -------------- | ---------------- | -------------- | ------------------------------------------------- | | Carbon Dioxide | CO₂ | 1 | Soil respiration, decomposition | | Nitrous Oxide | N₂O | 298 | Fertilizer application, manure, soil microbes | | Methane | CH₄ | 25 | Enteric fermentation, manure management, wetlands | #### NRCS Conservation Practice Standards COMET-Planner is designed around NRCS Conservation Practice Standards (CPS) that have been identified as providing greenhouse gas mitigation and/or carbon sequestration benefits. Practice categories include: * **Cropland Management:** Cover crops, reduced tillage, no-till, nutrient management, conservation crop rotation * **Grazing Land Management:** Prescribed grazing, range planting, silvopasture * **Agroforestry:** Windbreaks, riparian forest buffers, alley cropping, forest stand improvement * **Wetland and Riparian:** Wetland restoration, riparian herbaceous cover * **Nitrogen Management:** Nitrification inhibitors, enhanced efficiency fertilizers Modeling Duration and Equilibrium Conservation scenarios in DayCent are modeled over a 10-year period, with practices implemented annually (unless otherwise specified). Net values are averaged over this duration and reported on an annual basis. Soil carbon sequestration does not continue indefinitely—soils eventually reach a new equilibrium, typically within 20–50 years depending on practice and soil type. ``` # Annual ERC calculation from 10-year modeling annual_erc = total_10yr_reduction / 10 # Reported value per acre per year erc_per_acre_yr = annual_erc / sample_acres # Emission reduction represents the difference between: # - Baseline scenario (conventional management) # - Conservation scenario (practice implementation) ``` #### Scope and Limitations COMET-Planner estimates represent **field emissions only**, including those associated with soils and woody biomass. The tool does not include off-site emissions such as transportation, manufacturing, processing, or upstream fertilizer production. For more detailed site-specific analysis that accounts for full farm-scale emissions, use [COMET-Farm](https://comet-farm.com/). #### Acronyms


CH₄	Methane
CO₂	Carbon Dioxide
CO₂e	Carbon Dioxide Equivalent
COMET	CarbOn Management Evaluation Tool
CPS	Conservation Practice Standard
CSAF	Climate-Smart Agriculture and Forestry
ERC	Emission Reduction Coefficient
GHG	Greenhouse Gas
GWP	Global Warming Potential
IPCC	Intergovernmental Panel on Climate Change
MLRA	Major Land Resource Area
MT	Metric Ton
N₂O	Nitrous Oxide
NRCS	Natural Resources Conservation Service
SOC	Soil Organic Carbon
USDA	United States Department of Agriculture

#### Attribution COMET-Planner is a collaboration between the [U.S. Department of Agriculture Natural Resources Conservation Service](https://www.nrcs.usda.gov/) and [Colorado State University](https://www.colostate.edu/). ## Walk through of COMET Planner **Step 1. Select your activity (optional)**

**Step 2. Select county(ies)**

**Step 3. Select conservation practice class**

**Step 4. Select conservation practice standard\*** \*This list is dependent on the conservation practice class selection.

**Step 5. Choose conservation practice implementation\*** \*This list is dependent on the conservation practice standard selection.

**Step 6. Enter practice acreage** Enter the acreage associated with the conservation practice you selected.

**Step 7. Approximate carbon sequestration and greenhouse gas emissions reductions**

{% hint style="info" %} ¹ Conservation practices included in COMET-Planner are only those that have been identified as having greenhouse gas mitigation and/or carbon sequestration benefits on farms and ranches. This list of conservation practices is based on the qualitative greenhouse benefits ranking of practices prepared by NRCS. ² Approximate carbon sequestration and greenhouse gas emission reduction estimates are given in tonnes CO2 equivalent per year, where: tonnes = Metric Tonnes (same as Megagrams) Metric Tonnes are similar to English (or ‘short’) tons; 1 Metric Ton = 1.1 English (short) tons CO2 equivalent = Carbon Dioxide Equivalent\ Carbon dioxide equivalent is a measure used to compare the emissions from various greenhouse gases, based upon their global warming potential. Carbon dioxide equivalents are used in COMET-Planner to allow users to compare emission reductions of carbon dioxide, nitrous oxide and methane in standardized units. {% endhint %} --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://help.fielddoc.org/resources/models/comet-planner.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.