This document explains how Paspira CarbonLedger measures, calculates and reports greenhouse gas emissions. It is intended for auditors, sustainability managers and procurement teams requiring full transparency about the platform's calculation approach.
Paspira CarbonLedger calculates greenhouse gas emissions in accordance with the GHG Protocol Corporate Accounting and Reporting Standard (World Resources Institute and World Business Council for Sustainable Development, 2004, revised 2015). This is the most widely used corporate GHG accounting standard globally and forms the methodological basis for most national reporting requirements including SECR and CSRD.
Emission factors are sourced from the UK Government's annual Greenhouse Gas Reporting Conversion Factors publication, issued by the Department for Energy Security and Net Zero (DESNZ), commonly referred to as DEFRA factors. The current version used by this platform is DEFRA 2025, verified directly against the official published condensed-set spreadsheet.
The organisational boundary is set using the operational control approach as defined in the GHG Protocol. Under this approach, an organisation accounts for 100% of the GHG emissions from operations over which it has operational control — that is, the authority to introduce and implement its operating policies.
This means the inventory includes emissions from all sites, vehicles and operations the organisation controls, regardless of whether it owns them. It excludes emissions from operations where the organisation holds only a financial interest without operational control, such as minority joint ventures.
The default reporting period is the financial year as configured in account settings. Paspira CarbonLedger supports monthly data entry accumulating to an annual total. A complete inventory requires data for all 12 months across all three scopes.
Direct GHG emissions from sources owned or controlled by the organisation. This includes combustion of fossil fuels in boilers, furnaces and vehicles; process emissions; and fugitive emissions from refrigerants and air conditioning. Scope 1 is calculated using activity data (kWh of gas, litres of fuel, km driven) multiplied by the appropriate DEFRA 2025 emission factor.
Indirect GHG emissions from the generation of purchased electricity, heat, steam or cooling consumed by the organisation. Paspira CarbonLedger calculates Scope 2 using both the location-based method (using the national grid average emission factor from DEFRA 2025) and the market-based method (using supplier-specific factors or zero for renewable electricity backed by REGO certificates).
All other indirect GHG emissions that occur in the value chain of the organisation, both upstream and downstream. Scope 3 is typically the largest emission category for service-sector organisations. Paspira CarbonLedger supports the most material Scope 3 categories for UK SMEs, using DEFRA 2025 activity-based factors.
All emission factors are sourced from the UK Government DEFRA Greenhouse Gas Reporting Conversion Factors, published annually by the Department for Energy Security and Net Zero. Factors are updated in the platform each year when the new DEFRA publication is released (typically June/July). Paspira CarbonLedger's activity library contains 163 individually verified DEFRA 2025 factors — 48 in Scope 1, 16 in Scope 2, and 99 in Scope 3. The table below shows a representative sample; the full library is available directly within the Inventory and Calculator tools.
Each emission factor represents the kilograms of CO2 equivalent (kgCO2e) released per unit of activity. Factors include CO2, CH4 and N2O components combined into a single CO2e figure using IPCC AR6 global warming potentials.
Flight factors include Radiative Forcing Index (RFI) uplift and well-to-tank (WTT) emissions per DEFRA 2025 guidance. Waste disposal factors vary substantially by material and disposal method — organic materials in landfill (food waste, household residual waste) carry a far higher factor than inert materials (glass, aggregates) due to methane generation; the figures shown are representative examples, not universal constants. All factors are expressed as kgCO2e incorporating CO2, CH4 and N2O using IPCC AR6 100-year global warming potentials.
The net-zero trajectory shown on the Year-on-Year page calculates the annual reduction rate required to reach net zero by 2050, consistent with the SBTi Corporate Net-Zero Standard and GHG Protocol guidance.
Net zero under the GHG Protocol and SBTi Net-Zero Standard does not mean gross emissions reach literal zero. It means emissions are reduced as far as technically and economically feasible, with a small residual fraction addressed through permanent carbon removal or high-quality offsets. Paspira CarbonLedger assumes a residual emissions level of 10% of the base year total — a common simplification for organisations without a custom science-based target or sector-specific residual calculation.
The required annual reduction is calculated as a constant linear cut in absolute tonnes per year — not a compounding percentage. This matches how SBTi expresses its required reduction rates (e.g. 4.2% of baseline per year for the 1.5°C pathway) and is more conservative and transparent than compound decay models, which appear to accelerate progress in early years.
An organisation with 284.5 tCO2e in their base year would have a residual floor of 28.45t (10%), a linear annual cut of 10.67t/yr over 24 years to 2050, and a required annual reduction rate of 3.75% of baseline per year — comparable to the SBTi 1.5°C benchmark of 4.2%/yr.
The scenario forecast on the Year-on-Year page projects emissions from the current year to 2030 under four scenarios. All scenarios use a linear annual reduction applied as a constant percentage of the base year total — consistent with the net-zero trajectory methodology and SBTi's expression of required rates.
Scenario values are calculated as: projected(year) = base_year_total + (rate ÷ 100 × base_year_total × years_elapsed), floored at zero. These are illustrative projections only and do not constitute a commitment or guarantee of any specific emission outcome.
Paspira CarbonLedger assesses data quality using the five-tier framework from ISO 14064-1:2018 Annex B. Each emission category is assigned a tier reflecting the quality of the underlying data. The overall data quality score is a weighted combination of the average tier score (60%) and inventory completeness expressed as months entered out of 36 possible (40%).
A data quality score of 80 or above is considered sufficient for third-party assurance under ISAE 3000 and ISO 14064-3. Scores below 80 indicate areas where improving data collection methods would materially strengthen the credibility of the inventory.
Carbon credits are used to address residual emissions that cannot be eliminated through direct reduction. Paspira CarbonLedger records credits as purchased (held but not yet retired) or retired. Only retired credits are deducted from gross emissions to calculate the net carbon position.
Credits purchased and held in reserve are tracked separately and shown as a runway figure — how many months of current emissions the held credits would cover at the current burn rate. This is an operational planning metric, not an accounting treatment.
Accepted credit standards on the platform include Verified Carbon Standard (VCS/Verra), Gold Standard, UK Emissions Trading Scheme (UK ETS), EU Emissions Trading Scheme (EU ETS), and Woodland/Peatland Carbon Code (UK nature-based). Credits should be from projects that are additional, permanent, verifiable and independently audited.
Intensity metrics normalise absolute emissions against a business activity denominator. Paspira CarbonLedger calculates two intensity metrics required for Streamlined Energy and Carbon Reporting (SECR) and commonly used in TCFD disclosures.
Employee count and turnover are set in account settings. These metrics are required in the Directors' Report for organisations subject to SECR. They are also used in year-on-year comparisons to separate real emission reductions from changes driven by business growth or contraction.
The GHG Protocol Scope 2 Guidance (2015) requires organisations to report Scope 2 emissions using both the location-based and market-based methods where feasible.
The location-based method uses the average grid emission factor for the country of consumption — for UK organisations, this is the DEFRA 2025 UK electricity generation mix factor of 0.17700 kgCO2e/kWh.
The market-based method uses contractual instruments — primarily supplier-specific emission factors and Renewable Energy Guarantees of Origin (REGO) certificates. Where an organisation purchases electricity from a tariff backed by REGOs, the market-based Scope 2 emission factor is zero for that portion of consumption. Paspira CarbonLedger estimates the market-based figure from the proportion of electricity on a renewable tariff, using 0.00332 kgCO2e/kWh for non-renewable portions of a green tariff as a default where supplier-specific factors are unavailable.
If you are an auditor, procurement officer or sustainability manager with questions about how specific calculations are performed, please contact us. We are happy to provide additional documentation to support assurance or disclosure processes.
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