# Offsets integrity primer: reading ACCUs after the Chubb Review

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 Superseded by the 2024 FullCAM method.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

    cer_method_determination("HIR")
    cer_legislative_instrument("F2019C00664")

## 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.