Summarizes Regrow's approach to quantifying emissions factors within the system boundary.
Background
There are several methods to quantifying greenhouse gas (GHG) emissions in agricultural systems at scale and each of them comes with varying degrees of accuracy and precision. For example, direct measurements of emissions from a single location in a field could be highly accurate and very precise. However, this could require expensive equipment and could be location specific - thus limiting the applicability of such a system. On the other hand, simple equations describing the system would not capture local conditions or variability and would therefore be less accurate and precise for a single location. The benefit is that these equations could be applied broadly across states or countries or regions.
These differences in modeling approaches for emissions related to agriculture are divided into three broad categories : Tier 1, Tier 2 and Tier 3 emissions factors (EFs).
Tiers only define the equations or models used, not the data input into those equations.
Tier 1: Uses equations which are applied globally, derived from experiments across broad countries and regions and do not account for local variability. Tier 1 represents the most basic level of estimation of GHG emissions and are used when more detailed data are not available.
The Tier 1 calculations involve only a few parameters. Generally these are basic management activities that occurred and the emissions resulting from those activities.
Management data are optionally user-entered at the field level. Alternatively, when primary data is not available the data is defaulted based on Monitor API at the field level and/or regional defaults at the country level.
Tier 2: Uses country or regionally specific equations. This may or may not be generated using data inputs specific to the country or region of interest, depending upon scientifically rigorous sources availability. Parameters required for the equations and data inputs into those parameters are based on the geographic specific practice or technology for that region. They are more specific than the Tier 1 EFs and are used when available (USDA 2024).
Tier 3: Uses field level data fed into a process-based model such as DNDC where field level activities as well as soil, and weather are used to generate the most accurate estimates of GHG emissions.
Current state
Today, the emissions factors generated are a combination of Tier 1 (upstream) and Tier 3 (on-field/soil).
Tier 1: All upstream emissions factors leverage global Tier 1 equations. Management data and emissions coefficients driving those equations are 'best available' granularity, typically country level but can be as granular as field level dependent upon the activity category and data availability.
Tier 3: All on field soil emissions are quantified using DNDC model at Regrow, not through the Tier 1 and Tier 2 calculations.
Tier 2 equations are not leveraged in our methodology at this time.