BNZ Green

Carbon Accounting

Numbers that hold up under audit

An inventory is only useful if someone independent can trace it back to source. We build Scope 1, 2 and 3 accounts to GHG Protocol with the evidence trail attached, so assurance becomes a review rather than a rebuild.

  • GHG Protocol
  • All 15 Scope 3 categories
  • Audit trail per figure

Coverage

Complete, bounded and traceable

We resolve the questions that cause restatements later: organisational boundary, operational control, double counting and emission factor vintage.

  • Scope 1 direct combustion, process and fugitive emissions
  • Scope 2 purchased electricity on both location and market-based methods
  • Scope 3 screening across all 15 categories, with material ones built out fully
  • Documented organisational and operational boundary decisions
  • Emission factor register with source, vintage and applied conversion
  • Uncertainty assessment flagging estimate-based figures

Service

How the inventory is built

  • Data collection design

    We map every source to a system, an owner and a collection frequency, then automate the pulls that can be automated.

  • Boundary resolution

    Equity share, financial control or operational control — chosen deliberately and documented, including joint ventures and leased assets.

  • Scope 3 supplier engagement

    Structured outreach that replaces spend-based estimates with supplier-specific data, category by category.

  • Factor management

    A maintained emission factor library with vintage tracking, so year-on-year comparisons stay valid.

  • Assurance preparation

    Evidence packs organised the way verifiers request them, cutting audit query cycles significantly.

  • Platform handover

    Optional migration into the BNZ platform so the next cycle runs on live data rather than a fresh consulting effort.

Method

A repeatable annual cycle

  1. 01

    Scope & map

    Agree boundaries, identify every source and name the data owner for each.

  2. 02

    Collect

    Pull activity data, resolve gaps and document any estimation method applied.

  3. 03

    Calculate

    Apply factors, run internal QA and reconcile against prior years.

  4. 04

    Assure & repeat

    Support verification, then hand over the process so it runs annually.

Questions

Practical questions

  • Should we attempt all 15 Scope 3 categories at once?

    Rarely. We screen all 15 to identify which are material, then build those out properly. Attempting full depth across every category in year one typically produces a large volume of low-confidence data that nobody trusts.

  • Location-based or market-based Scope 2?

    Both. GHG Protocol requires dual reporting where market instruments are held, and the two figures answer different questions — grid exposure versus procurement choices. We calculate and present both.

  • How do you avoid double counting in Scope 3?

    Category boundaries are defined explicitly at the outset, with particular attention to the overlaps that cause problems: purchased goods against capital goods, and upstream transport against distribution.

  • Can you rebuild a prior year inventory?

    Yes, and it is often necessary when a baseline was built without an audit trail. We reconstruct from source records where they exist and clearly flag where documented estimation was required.

Get an inventory you can defend

Send us your current numbers and we will tell you where the assurance risk sits before you commit to anything.

  • GHG Protocol aligned
  • Third-party assurance ready
  • Sector-specific teams