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Carbon Accounting

Carbon Offset Standards, Methodologies and Protocols

The American Carbon Registry (ACR) registers GHG emissions reduction projects that meet the ACR Standards, as described below. In addition, ACR has been approved by the California Air Resources Board (ARB) as an Offset Project Registry (OPR) for the California compliance market.

California Compliance Offset Protocols

To be eligible for compliance in the California cap-and-trade system, offset projects will be required to use ARB-approved compliance or early action offset protocols, to be verified by ARB-approved verification bodies, and to register on an ARB-approved Offset Project Registry (OPR) or Early Action Offset Program, such as American Carbon Registry. For more information on the California compliance offset program, see our California Offsets page.

American Carbon Registry Standards and Methodologies

The American Carbon Registry (ACR) publishes standards, methodologies, protocols and tools for greenhouse gas (GHG) accounting, which are all based on International Standards Organization (ISO) 14064 and sound scientific practice. ACR only registers project-based carbon offset tons that are real, additional, permanent and independently verified.


ACR credits project-level emissions reductions / removals for the following scopes as defined by the American National Standards Institute (ANSI), the body which accredits and oversees Validation and Verification Bodies for ACR. ACR scope exclusions are detailed in the ACR Standard.

1. GHG emission reductions from fuel combustion   

  • Energy Efficiency Improvements: (fuel switching, waste heat recovery, cogeneration)
  • Transportation

2. GHG emission reductions from industrial processes (non-combustion, chemical reaction, fugitive, other) 

  • Ozone Depleting Substances Destruction
  • SF6 replacement
  • SF6 emission avoidance
  • HFC destruction/decomposition
  • PFC anode effect mitigation
  • Production of nitric acid and adipic acid
  • Reduced emissions from destruction of N2O in manufacturing

 3. Land Use, Land Use Change and Forestry    

  • Sequestration of carbon due to afforestation, avoided deforestation, sustainable forest management, forest products)

 4.  Carbon Capture and Storage      

  • Emissions sources that are injected into underground geological formations (e.g. abandoned oil and gas reservoirs, saline aquifers, or unminable coal seams)

5.  Livestock                

  • Methane Collection and Destruction
  • Livestock and other anaerobic digester operations
  • Agricultural methane emission reduction
  • Agricultural carbon emission reduction

6. Waste Handling and Disposal       

  • Capture and destruction of Landfill gas
  • Capture and use of Landfill gas (biodigestion, aerobic treatment)
  • Avoidance of methane production in wastewater treatment
  • Coal mine methane


ACR accepts projects validated and verified against an ACR-approved methodology, provided they comply with the current version of the ACR Standard. ACR process for development and approval of standards and methodologies is led by a qualified technical team. Approval includes review by ACR's technical team, a stakeholder comment period and a scientific peer review process, a rigorous technical review by experts in the relevant field(s). This combination of approaches ensures that our published standards and methodologies are the highest quality.

The Winrock and ACR team that leads the development of standards and methodologies includes internationally recognized leaders in the forestry, agriculture, industrial and energy sectors and is widely recognized for its deep expertise in carbon accounting.

New Methodologies

The American Carbon Registry promotes innovation to bring new offsets types to market. Project developers are welcome to submit new offset methodologies and methodology modifications for evaluation. New methodologies and methodology modifications are approved for use through ACR's public comment and scientific peer review process. Upon approval, ACR will publish the methodology for future use.