Comments to ARB on Quantitative Methodology, Accounting

The document outlines technical recommendations for the California Air Resources Board (ARB) on monitoring, reporting, and verification (MRV) and accounting for CO2 sequestration. It emphasizes the priority of subsurface plume tracking over surface monitoring, argues that only anthropogenic CO2 should be credited, and suggests pragmatic 'haircut' approaches to credit reductions in the event of atmospheric leakage. For EOR applications, it clarifies that recycled CO2 should not require mass balance accounting and stresses the critical importance of wellbore integrity in brownfields.

• To prevent atmospheric leakage, the author recommends rigorous site selection, risk analysis, and the evaluation of legacy wells to ensure wellbore integrity or secure plugging and abandonment, stating that any storage complexes failing these goals "should be rejected."
• Subsurface plume tracking is identified as critical for monitoring storage integrity, whereas surficial monitoring methods, such as soil gas fluxes, are described as potentially "ineffective" due to the difficulty of distinguishing leakage from natural seasonal fluxes.
• The author proposes that only anthropogenic/captured CO2 that would otherwise be vented should receive sequestration credits. In cases of atmospheric leakage, the document suggests a pragmatic accounting approach, such as a "haircut" where credits are reduced based on the estimated maximum possible leakage (e.g., a 20% debit if leakage is estimated between 0-20%).
• Regarding Enhanced Oil Recovery (EOR), the document argues against the misconception that only half of injected CO2 is stored, explaining that because CO2 is separated and recycled, the initial volume is progressively stored until it "asymptotically approaches 100%--less any CO2 lost."

APA

Hill, B. (2016). Comments to ARB on Quantitative Methodology, Accounting. Clean Air Task Force. https://cdn.catf.us/wp-content/uploads/2018/11/21093933/CATF_BruceHill_Comments_ARB.pdf

Chicago

Hill, Bruce. Comments to ARB on Quantitative Methodology, Accounting. Clean Air Task Force, 2016. https://cdn.catf.us/wp-content/uploads/2018/11/21093933/CATF_BruceHill_Comments_ARB.pdf.

Wikipedia

{{cite press release |last1=Hill |first1=Bruce |title=Comments to ARB on Quantitative Methodology, Accounting |publisher=Clean Air Task Force |date=28 April 2016 |url=https://cdn.catf.us/wp-content/uploads/2018/11/21093933/CATF_BruceHill_Comments_ARB.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@misc{hill2016comments, author = {Hill, Bruce}, title = {{Comments to ARB on Quantitative Methodology, Accounting}}, publisher = {Clean Air Task Force}, year = {2016}, month = apr, url = {https://cdn.catf.us/wp-content/uploads/2018/11/21093933/CATF_BruceHill_Comments_ARB.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }