Every emissions figure a company reports eventually traces back to one of three things: a place where fuel was burned or power was drawn, a counterparty the company bought something from, or a legal entity whose results it consolidates. Before any activity data is collected, before any emission factor is applied, those three lists have to exist and have to be right.
This is the work the Directory does. In the Data module, it holds three record types: Facilities, Suppliers, and Entities. Each one is added through its own control in the interface, and each one answers a different question about the shape of the organization being reported on.
It looks like data entry. It is actually boundary setting, and boundary errors are the most expensive errors in carbon accounting because they are invisible in the output. A missing site does not produce a wrong number that looks wrong. It produces a clean number that is quietly incomplete.
Facilities: where the data comes from
Facilities are the operating sites and locations Hydrus collects data from. Offices, plants, warehouses, data centres, retail locations, leased floors, fleet depots.
A facility record is the anchor for Scope 1 and Scope 2. Utility bills, fuel purchases, refrigerant logs, and meter reads all have to land somewhere, and the facility is where they land. It is also what makes location-specific factors possible: a site in one grid region and a site in another produce different Scope 2 numbers from identical consumption.
A facility record that holds up under review should carry:
- Site name, physical address, and country or grid region.
- Ownership or tenure: owned, leased, operated under contract.
- Operational status and the dates it was active in the reporting period.
- Site owner, meaning the person accountable for the data, not the landlord.
- Floor area, headcount, or another activity denominator for intensity metrics and estimation.
- Which scopes and activity types the site contributes.
The common failure is the leased site nobody claims. Facilities reports to procurement or real estate, emissions reporting sits with sustainability, and the small satellite office falls between them for three reporting cycles.
Suppliers: where Scope 3 comes from
Suppliers are the vendors and partners you collect Scope 3 data from. The Suppliers area holds the current list and lets you add new ones as the value chain is mapped.
The supplier list is where Scope 3 either becomes defensible or stays an estimate. A supplier record is the address a data request goes to, the place a supplier-specific emission factor gets attached when it comes back, and the record that proves you asked when it does not. It is also what allows a company to show movement from spend-based estimation toward primary data over time, which is increasingly what reviewers look for.
Useful supplier records carry:
- Legal name and the procurement identifier used in the ERP or vendor master.
- Spend, volume, or another activity basis for the reporting period.
- The Scope 3 category the relationship maps to.
- Tier, where multi-tier mapping matters.
- Data method in use: supplier-specific, average-data, spend-based.
- Engagement status and the date of the last data request and response.
Not every supplier needs a record. A small number of them usually account for most of the footprint, and the list should be built from that concentration rather than by importing the entire vendor master and creating thousands of dormant rows.
Entities: what you consolidate
Entities are the subsidiaries, joint ventures, partners, and subcontractors that make up the corporate structure. The Entities area holds these and lets you add more as the structure changes.
This is the record type most often treated as administrative, and it is the one that decides what the report covers. Under the GHG Protocol, a company chooses a consolidation approach: operational control, financial control, or equity share. That choice determines whether a joint venture's emissions come in whole, in part, or not at all, and it should be applied consistently across every entity in the structure.
Entity records should make that logic explicit:
- Legal entity name, jurisdiction, and position in the group structure.
- Ownership percentage.
- Consolidation basis applied, and the rationale where it is not obvious.
- Reporting periods the entity was in scope.
- Which facilities roll up to it.
Where the entity list and the finance consolidation list disagree, the disagreement needs to be documented rather than resolved silently. Auditors compare the two.
The principle: a directory is time-bounded
Directories are not static reference data. Companies acquire, divest, close sites, open sites, change leases, restructure joint ventures, and switch suppliers. Each of those events changes the boundary, and some of them trigger base-year recalculation.
This means every record needs effective dates, not just current values. A facility that closed in March contributed nine months of nothing and three months of something. An entity acquired mid-year is either in scope from the acquisition date or restated across the full period, depending on the recalculation policy, and the record has to show which. Overwriting a directory entry when something changes destroys exactly the history an assurance provider will ask for.
In Hydrus, the Directory is the spine the rest of the Data module attaches to. Ingested emails, API feeds, OCR'd bills, uploads, and supplier responses resolve to a facility, supplier, or entity record, which is what makes lineage possible: any number in a CSRD, ISSB, CDP, or GHG Protocol output can be traced back through the calculation to the record and the source document it came from. Build the directory carelessly and every downstream report inherits the ambiguity.
The useful operating question is this: if an assurance provider asked for the complete list of sites, counterparties, and entities in scope for last year's report, along with the reason each one was included or excluded, could you produce it from governed records rather than reconstructing it from memory?
A directory is not a list of names. It is the boundary of everything you claim.
This guide is educational and not legal advice.