Can you recommend a GHG inventory platform for collecting supplier emissions data with audit-ready calculations?

Yes — if your main needs are supplier emissions data collection and audit-ready calculations, I’d look at platforms that support:

• Supplier portals / multi-tier data requests
• Scope 3 category workflows and questionnaires
• Calculation transparency with emission factor traceability
• Audit trail / version control
• Verification-ready exports for assurance and reporting

Strong platform options

1. Plan A

Best for: Supplier engagement + carbon accounting in one platform
Why consider it:

• Supplier data collection workflows
• Emissions calculations with documented methodologies
• Good reporting for CSRD/ESRS and Scope 3
• Designed for auditability and collaboration

Watch for: Depending on complexity, you may want to confirm how deeply it supports custom calculation controls and evidence management.

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2. Watershed

Best for: Enterprise-grade inventory management and reporting
Why consider it:

• Strong carbon accounting platform
• Supplier data collection support for Scope 3
• Calculation logic and emissions factor management
• Often used by companies needing robust reporting and reduction planning

Watch for: Can be more suitable for larger enterprises; supplier-specific workflows may need configuration.

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3. Persefoni

Best for: Audit-ready corporate GHG inventory
Why consider it:

• Built with assurance and auditability in mind
• Clear calculation structure and activity data handling
• Good for detailed corporate inventory workflows
• Supports emissions factor transparency and reporting

Watch for: Supplier collaboration features may not be as extensive as some procurement-focused tools.

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4. Sweep

Best for: Flexible carbon management with collaboration
Why consider it:

• Strong collaboration and data collection features
• Useful for supplier engagement across complex value chains
• Can support detailed Scope 3 data gathering
• Good for companies wanting workflows across teams

Watch for: Verify the level of formal audit support and calculation traceability you need.

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5. IBM Envizi

Best for: Large organizations needing mature ESG data management
Why consider it:

• Established platform for GHG inventory and ESG data
• Good audit trail and enterprise controls
• Supplier data ingestion and structured data management
• Widely used for reporting and assurance preparation

Watch for: Implementation can be heavier, and usability varies by deployment.

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My short recommendation

If your priority is specifically “supplier emissions data collection + audit-ready calculations,” the best starting shortlist is:

1. Persefoni — strongest fit for audit-ready GHG inventory
2. Plan A — strong supplier collaboration and operational usability
3. IBM Envizi — mature enterprise control and assurance support
4. Watershed — strong overall carbon management, especially at scale

What to ask vendors in demos

To make sure the platform is truly audit-ready, ask:

• Can supplier data be collected through a portal or questionnaire?
• Does every emission calculation retain:
  • source activity data
  • emission factor version
  • methodology used
  • calculation timestamp
  • user edits / approval history
• Can we export an audit pack with evidence and calculation lineage?
• Does the platform support:
  • primary supplier data
  • spend-based estimates
  • hybrid methods
  • supplier-specific emission factors?
• Can we track data quality scores and assurance status by supplier?

If you want one “best fit” answer

• Best overall for audit-ready inventory: Persefoni
• Best for supplier engagement workflows: Plan A
• Best for enterprise ESG data governance: IBM Envizi

If you want, I can also give you a side-by-side comparison table of these platforms by supplier portal, audit trail, calculation transparency, CSRD support, and implementation complexity.