What is the Anthropogenic Emissions Model?
The Anthropogenic Emissions Model (AEM) is a tool for objectively defining any project’s impact on global emissions and is the foundation of the Absolute Carbon Standard. AEM models project emissions within the criteria of the carbon cycle to determine the impact on the global carbon balance. AEM assesses where human activities are moving emissions to and from, not how.
Because AEM assesses projects from the climate-level, it is universally applicable to any emissions and produces consistent results from any project. This is in contrast to traditional project-level assessments that apply project specific criteria and produce project specific outcomes. For example, direct air capture and biochar use different methodologies to quantify their emissions impact, making it impossible to conduct an apples to apples comparison of them.
Carbon markets and emission targets aim to restore balance to the carbon cycle. Net zero and other emission targets are defined by the amount of emissions stored versus the amount of emissions released in the atmosphere. AEM directly embeds this global-emissions-level metric of stored and atmospheric emissions into project level metrics by directly assessing the amount of emissions a project moves into and out of storage and the atmosphere. Measuring a project’s impacts on the same emission pools measured to determine global emission targets ensures that the resulting project claims match their physical emissions impact. This approach also ensures that all claims are relative to global emissions and net zero targets.
AEM sets a consistent universal benchmark across project-level assessments. Instead of defining credit tons by the abilities of a specific technology or approach, AEM sets the criteria for a ton of mitigation based on the metrics of the carbon cycle and then adapts project-level methodologies to meet the new criteria. AEM has the ability to sort any and all carbon projects into explicitly defined categories based on the climate impact. This simplifies credit assessments, emissions accounting, and ensures accurate results.
Structure of the Anthropogenic Emissions Model
AEM is based on the carbon cycle, which it models in the three Emission Pools and five Emission Pathways shown in Figure 1. Emission Pools clearly define carbon stocks and reservoirs in terms of emissions accounting, and Emission Pathways explicitly define fluxes in relation to the Emission Pools between which carbon is moved.
Three Emission Pools are used to model the carbon cycle in AEM: Polluting, Use, and Stored. The Stored Pool defines all conserved carbon stocks and non-anthropogenic systems in the carbon cycle (these include the emission stores that are accounted for in global stock takes and national inventories). The Polluting Pool refers to the reactive and dispersed emissions in the atmosphere and ocean. The Use Pool includes all anthropogenic emissions and activities - this is where all the emissions that are neither stored nor polluting are accounted for.
Five defined emission pathways (Extract, Release, Use/Reuse, Capture, Store) within AEM describe how anthropogenic activities move emissions into, out of, and within the Use Pool. The Emission Pools and pathways allow any project emissions to be modeled clearly and objectively.
The five defined emission pathways are:
- Extract – A stored emission moves from the Stored Pool to the Use Pool.
- Ex. Underground Oil (a stored emission in the form of a oil in the Stored Pool) is extracted for fossil fuel use - Release – An emission moves from the Use Pool to the Polluting Pool
- Ex. A barrel of oil (a stored emission in the Use Pool), is burned as jet fuel, releasing the emission into atmosphere - Use/Reuse – An emission is utilized for anthropogenic purposes within the Use Pool
- Ex. Timber (a stored emission in the Use Pool) is used in the construction of a house - Capture – An emission moves from the polluting pool to the Use Pool
- Ex. A Direct Air Capture plant captures CO₂ from atmosphere - Store - An emission moves from the Use Pool to the Stored Pool
-Ex. Captured CO₂ in the form of biomass (a stored emission in the Use Pool) is buried underground for long-term storage
Clearly defining Emission Pools and Emission Pathways creates clear and consistent baselines, project scopes and assessments. By applying AEM’s climate level approach, AEM recognizes the different climate value of projects where traditional frameworks are unable to.
Assessments Using Anthropogenic Emissions Model
Assessments with AEM are done in three simple steps: Model, Assess, and Designate.
1. Modeling the Emission Pathways
The project emission inputs and outputs are mapped in the emission pools using the five emission pathways. All project activities occur in the Use Pool, and any emissions used or processed by the project are mapped from and to the Polluting or Stored Pool. The resulting project pathway, then directly maps how the project moves emissions between the Stored and Polluting Pools- the impact on the carbon cycle.
All projects use a baseline condition of zero emissions in the Use Pool and net scope that includes all project activities and emissions in the Use Pool. The emissions that a project mitigates (captures or stores) define the primary emission stream. Operating emissions include the embodied emissions, and emissions resulting from project inputs such as electricity use. All emissions entering the Use Pool are accounted for leaving the Use pool. No emissions are excused with counterfactual arguments or selective scoping, which results in objective and consistent assessments.
2. Assess Carbon Balance
Emission quantities are applied to the pathways for the assessment period and the change in emissions in the Stored and Polluting Pool are summed to determine if the project produced: net positive, net negative, or net zero emissions. The assessment uses the same set of equations for every project. The emissions captured from the Polluting Pool are subtracted from those released into the Polluting Pool. The same is done for the Storage Pool.
3. Designate the Mitigation Type
The project’s mitigation type is designated based on the results of the assessment.
- Positive results reflect an Emission - a net transfer of emissions from the Stored to the Polluting pool.
- Negative results define a Restoration - a net transfer of emissions from the Polluting to the Stored Pool.
- Net zero results define a Recovery - a net zero transfer of emissions due to emissions being returned to the emission pool they were sourced from
We’ll be doing a deeper dive into Mitigation Types in an upcoming essay.
Where to use AEM
AEM is a tool with widespread applicability. AEM can be used to verify or determine a project’s emissions impact claim. It can be used by buyers for due-diligence, and policy-makers for credit definitions. AEM can also be used to adjust project-level assessments to a common criteria baseline so that they can be accounted for on apples to apples terms.
How AEM improves Emissions Accounting
AEM provides an emissions assessment consistent with physical science that is compatible with policy and economic frameworks. Because AEM is not defined by policy frameworks or project approaches, it is enduring of changes in policy and innovation, and is applicable across all carbon projects. AEM’s objectivity allows innovation in technology and changes in policy without needing to change the emissions assessment.
AEM assessments are net impacts that assess the entirety of an emission stream, not a selective scope of it. Existing methodologies allow for project’s to claim a negative emission with selective scoping. AEM makes this impossible by requiring the entire emission stream to be accounted for.
AEM creates a mathematical, objective, and universal determination of project impacts. Negative emission claims are defendable and distinguishable from reductions without specifying industry or project technologies.
Carbon is carbon, it doesn't matter what technology moved the emissions, it matters what impact was created.
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