Corporate GHG Inventory

Greenhouse gas accounting, also referred to as GHG accounting or carbon accounting, is the process of identifying, quantifying and reporting an organisation's greenhouse gas emissions in a structured, repeatable and auditable way. The GHG Protocol Corporate Standard is the most widely used framework for corporate greenhouse gas accounting, setting out the rules for boundary-setting, emission factor selection and Scope 1, 2 and 3 categorisation. A well-built GHG measurement programme does more than produce a number: it creates a methodology that can be updated annually, audited by a third party and used as the baseline for science-based target-setting and decarbonisation planning.

A GHG inventory is a structured measurement of your organisation's greenhouse gas emissions, covering Scope 1 (direct emissions from owned operations), Scope 2 (purchased energy) and Scope 3 (all other value chain emissions across 15 categories). A documented, methodology-based inventory is now required for CSRD ESRS E1 disclosure, SBTi target-setting, EcoVadis ENV scoring, CDP reporting and an increasing number of customer-driven supply chain requirements. Without one, your organisation cannot credibly demonstrate climate performance or respond to the parties requesting verified data.

Calculating a GHG inventory requires multiplying activity data (such as litres of fuel consumed, kWh of electricity purchased, or tonnes of goods bought) by the relevant emission factor for each source. Emission factors convert physical activity into tonnes of CO2 equivalent (tCO2e) and are published by bodies such as DEFRA (UK), ADEME (France) and the IEA (global). The calculation process follows the GHG Protocol Corporate Standard, which sets the rules for what must be included, how to handle estimates where primary data is unavailable, and how to treat emissions from shared or outsourced activities. For Scope 3, where direct data is rarely available, spend-based or industry-average approaches are used as a starting point, with supplier-specific data collected over time to improve accuracy. Nexio Projects manages the full calculation process on behalf of clients, with every step documented in a methodology file and traceable by your assurance provider.

Creating a GHG inventory involves five core steps: defining your organisational and operational boundary; identifying all relevant emission sources across Scope 1, 2 and 3; collecting activity data for each source; applying appropriate emission factors (such as DEFRA, ADEME or IEA); and producing a methodology document that makes your calculations traceable and auditable. For most organisations, the most challenging step is Scope 3 data collection, particularly for purchased goods and services (Category 1) and upstream transport (Category 4). Nexio Projects structures every GHG inventory engagement around a data mapping exercise at the outset, so you know exactly what data exists, what requires estimation and who within your organisation holds it.

Monitoring greenhouse gas emissions on an ongoing basis requires a consistent data architecture, a fixed methodology and a structured annual update process. The most effective approach is to design your first GHG inventory as a repeatable programme rather than a one-off project — with data collection templates, emission factor update protocols and a fixed reporting boundary that can be refreshed each year without rebuilding from scratch. CarbonCount supports self-service annual updates, allowing clients to input new activity data each year against the same methodology, producing a year-on-year comparison with variance analysis. For organisations using audit-grade Excel models, Nexio Projects delivers the same annual update process with a consultant-led data refresh.

A product carbon footprint (PCF) measures the lifecycle emissions of a specific product, from raw material extraction through to end-of-life. A corporate GHG inventory measures the total greenhouse gas emissions of an entire organisation across Scope 1, 2 and 3. The two are related but distinct: a corporate inventory may draw on PCF data within its Scope 3 calculations, particularly for purchased goods and services. All Nexio Projects corporate engagements are built to GHG inventory standard, methodology-documented, annually structured and evidence-packed for assurance from day one. For product-level footprints, see our PCF/LCA service.

CarbonCount is Nexio Projects's proprietary GHG inventory platform, used for SME and growing mid-market clients. It delivers full GHG Protocol coverage across Scope 1, 2 and all 15 Scope 3 categories, with embedded emission factor databases, a full audit trail and a self-service annual update option. CarbonCount is the primary tool for smaller organisations and selected mid-market clients where limited assurance is possible. For larger organisations with mandatory reasonable assurance requirements, Nexio Projects uses bespoke audit-grade Excel models or enterprise platforms — which verifiers typically prefer for their transparency.

This depends on your regulatory obligations, reporting frameworks and public disclosure commitments. CSRD requires third-party limited assurance for all in-scope companies, with a trajectory toward reasonable assurance. SBTi strongly encourages independent verification, this requirement is expected to be formalised for large companies in the future, though it is not currently mandatory. EcoVadis does not require third-party assurance but assesses the credibility and completeness of GHG data in its ENV scoring. CDP awards higher scores to organisations that submit third-party verified data. Beyond formal requirements, assurance is also best practice for any organisation making public climate commitments: it substantiates those statements and reduces greenwashing exposure. Nexio Projects designs all inventories to be assurance-ready from the outset, whether or not your current reporting cycle requires formal verification.

Scope 3 covers all indirect greenhouse gas emissions in your value chain, across 15 categories including purchased goods and services, logistics, business travel, product use and end-of-life treatment. For most organisations, Scope 3 represents more than 70% of total GHG emissions. Materiality varies by sector: for manufacturing clients, Category 1 (purchased goods) is typically dominant; for logistics clients, Categories 4 and 9 (transport); for financial services, Category 15 (investments). Nexio Projects assesses materiality as part of every scoping engagement and prioritises data collection accordingly

Not necessarily. Nexio Projects can review your existing GHG inventory for methodology consistency, boundary completeness and documentation quality, then either bring it to the required standard or rebuild only the components that need it. In many cases, a previous inventory provides a useful starting point, particularly if you are moving into an annual programme structure. A clear assessment is provided before any remediation work begins, so you know exactly what is involved before committing.

A Scope 1 and 2 inventory for a single-site SME is typically delivered in four to six weeks. A full Scope 1, 2 and 3 programme for a mid-market organisation takes eight to twelve weeks. Enterprise-scale engagements with multi-entity structures and assurance coordination are scoped individually. The most common cause of delay is data collection, which is why Nexio Projects begins every engagement with a structured data mapping exercise to identify what exists, what requires estimation and who within your organisation holds it.

Yes. Nexio Projects regularly inherits greenhouse gas inventories built internally or by other consultants, reviews them for methodology consistency, boundary completeness and documentation quality, and either brings them to the required standard or rebuilds the components that need it. A clear assessment is provided before any remediation work begins.

Nexio Projects recommends structuring your engagement as an annual GHG programme from the first year. In Year 2 onwards, your data architecture is already in place, updates are faster, less expensive and progressively more accurate as data quality improves. Clients who maintain an annual programme also benefit from regulatory alignment checks, year-on-year benchmarking and continuity with a consultant who knows their business.

Regulatory requirements, customer expectations and investor scrutiny are converging on verified, structured greenhouse gas data. A robust inventory protects existing revenue, opens new commercial doors, avoids regulatory penalties, and strengthens your organisation's resilience in a shifting geopolitical landscape. Organisations that delay face higher costs and greater assurance risk when the deadline arrives.
Three pressures are accelerating the timeline:

- CSRD Wave 2, FY2027. Companies with more than 1,000 employees and more than €450M turnover must disclose Scope 3 emissions and prepare for third-party limited assurance. GHG accounting preparation should begin no later than 2026.
- SBTi, 24 months to submission. Every science-based target commitment requires a verified Scope 1, 2 and 3 baseline. Scope 3 data quality is the leading cause of SBTi submission rejection.
- Supply chain data requests. CSRD-obligated companies are cascading Scope 3 data requirements to their suppliers, regardless of whether those suppliers are directly regulated. This is becoming a commercial requirement, not just a regulatory one.

Nexio Projects' dedicated GHG accounting platform for SMEs and growing enterprises.

CarbonCount is purpose-built carbon calculation software, expertly configured and managed by your Nexio Projects consultant. Rather than handing clients a blank tool and leaving them to figure it out, CarbonCount combines proven greenhouse gas accounting technology with hands-on expert oversight. So, methodology, boundary decisions and emission factor selections are always set correctly from the start.

Full GHG Protocol coverage
- Scope 1, 2 and all 15 Scope 3 categories, with ESRS E1 compliance built in.
- Embedded emission factor databases DEFRA, ADEME, IEA, AIB, Ecoinvent, GLEC, WRAP and CBAM, automatically updated, removing manual factor research from every engagement.

Bulk data import
- Activity data uploaded via Excel or API, substantially reducing manual data entry time for clients and consultants.
- Full audit trail Every assumption, calculation step and data source is logged within the platform.
- Assurance providers can access the platform directly, eliminating the need for a parallel evidence pack for most clients using CarbonCount.

Scenario simulation
- Reduction pathways and SBTi target trajectories modelled within the platform, enabling clients to move directly from inventory to action planning.
- Self-service annual updates
- Clients can be trained to input their own data each year, reducing recurring delivery costs and increasing year-on-year data quality.

CarbonCount covers ESRS E1 (climate) and does not extend to other ESRS environmental, social or governance topics. Clients requiring full multi-topic CSRD disclosure are supported through Nexio Projects's broader CSRD reporting programme alongside a separate reporting framework.