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Offsets integrity primer: reading ACCUs after the Chubb Review

Source: vignettes/offsets-integrity-primer.Rmd
offsets-integrity-primer.Rmd

Australian Carbon Credit Units (ACCUs) are not fungible after Chubb (2022). Different methods have different integrity profiles; some methods are under active review by the Independent Integrity Assurance Committee; some are suspended. A headline figure like “185 million ACCUs issued to date” is only meaningful once decomposed by integrity tier.

This vignette walks through the cer integrity layer.

What changed after Chubb (2022)

The Independent Review of Australian Carbon Credit Units (Chubb, December 2022) identified five ACCU methods for specific attention:

  • Human-Induced Regeneration (HIR). Recommended replacement by a new Integrated Farm and Land Management (IFLM) method.
  • Avoided Deforestation. Closed to new project registrations.
  • Landfill Gas. Tightened baseline-crediting expectations.
  • Soil Carbon. Strengthened Measurement, Reporting, and Verification (MRV) requirements.
  • Plantings (2014 method). Superseded by the 2024 FullCAM method.

Independent academic critique (Macintosh et al. 2022, ANU) was sharper on HIR specifically. The live debate is continuing.

Query the integrity scorecard 

library(cer)
cer_snapshot("2026-04-24")

all_methods <- cer_method_integrity()
all_methods[, c("method_short", "status", "integrity_tier", "chubb_affected")]

Filter to contested methods 

contested <- cer_method_integrity(tier = "contested")
contested[, c("method_short", "method_full_name", "status")]

Aggregating ACCUs by integrity tier 

projects <- cer_accu_projects(status = "all")

by_tier <- cer_accu_aggregate(projects,
                               value_col = "accus_issued",
                               warn_contested_pct = 0.05)
by_tier

The function emits a warning when contested-integrity methods account for more than 5 per cent of the total : a signal that a single headline figure is not appropriate.

Warnings when querying a suspended method 

# Will emit a post-Chubb integrity warning
ad <- cer_accu_projects(method = "avoided deforestation",
                         status = "all")

Linking to the authoritative determination

Rule of thumb

If your analysis depends on an aggregate ACCU figure, report three numbers: total, high-integrity share, and contested share. A reviewer will ask for this breakdown; better to have it in the table than in a footnote.