1. Standards and frameworks
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 2026 (published 11 June 2026), verified directly against the official full-set workbook and the official flat-format data export, cell by cell — not from memory or a secondary source.
Corporate accounting standardGHG Protocol Corporate Accounting and Reporting Standard (WRI/WBCSD, 2004, revised 2015)
Emission factor sourceDEFRA 2026 Greenhouse Gas Reporting Conversion Factors (UK Government, DESNZ)
Activity library size209 verified activities — 52 Scope 1 · 32 Scope 2 · 125 Scope 3
Data quality frameworkISO 14064-1:2018 Annex B data quality tiers
Net-zero pathwaySBTi Corporate Net-Zero Standard (2021) — linear absolute contraction
Assurance standardISAE 3000 / ISO 14064-3 (third-party assurance not performed by Paspira)
2. Organisational boundary
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.
Reporting period
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.
3. Scope definitions
Scope 1 — Direct emissions
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 2026 emission factor.
Categories covered
Natural gas, LPG, diesel, petrol and other stationary fuelsWood, wood pellets and grass/straw — direct biomass combustionCompany vehicles — diesel cars, vans, motorbikesRefrigerant gases — 17 Kyoto Protocol substances (HFCs, SF6)Solid fuels — coal, coking coal
Scope 2 — Purchased energy
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 2026) and the market-based method (using supplier-specific factors or zero for renewable electricity backed by REGO certificates).
Categories covered
UK grid electricity (location-based: 0.13096 kgCO2e/kWh)Renewable electricity with REGO (market-based: 0.00000 kgCO2e/kWh)Standalone battery-electric vehicle charging — 13 vehicle segmentsPlug-in hybrid vehicle charging — 12 vehicle segmentsDistrict heat and steam
Scope 3 — Value chain emissions
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 2026 activity-based factors.
Categories covered
Business travel — domestic flights, short-haul, long-haulBusiness travel — national rail, tube, bus, taxi, ferry, car (diesel/petrol/unknown fuel)Hotel stays — 38 countries individuallyHomeworkingWaste — landfill, recycled, composted, anaerobic digestion, by materialWater supply and treatmentFreight — van and HGV, by fuel type and realistic laden weightPaper, plastics, metal procurement (material use)Supplier emissions (activity-based where available)
4. Emission 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). Paspira CarbonLedger's activity library contains 209 individually verified DEFRA 2026 factors — 52 in Scope 1, 32 in Scope 2, and 125 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 AR5 global warming potentials, per DESNZ's published methodology.
Two 2026 factors moved in a direction that runs counter to every other electricity-linked category this year (which all decreased, tracking the UK grid electricity update below): Coach travel increased +42.2% (0.02776 → 0.03948 kgCO2e/km) and international rail increased +154.5% (0.00446 → 0.01135 kgCO2e/km). Both figures are verified directly against the official source, not a transcription error on our part — but their direction is unusual enough that we\'d recommend treating them with extra scrutiny if they materially affect your reported total.
Two activities remain unavailable: petrol company cars for Scope 1 owned fleet specifically (confirmed absent even in the full DEFRA 2026 publication — petrol data does exist for Scope 3 business-travel cars and freight vans, just not owned-fleet cars), and employee commuting (a separate DEFRA spend-based publication, not yet sourced). One waste factor — average construction waste sent to landfill — has no published value in the 2026 source at all; this is confirmed as an absence in DESNZ\'s own data, not a gap in how it was read.
Natural gas combustion0.18231 kgCO2eper kWhS1
LPG combustion1.55713 kgCO2eper litreS1
Fuel oil combustion3.17492 kgCO2eper litreS1
Diesel (average biofuel blend)2.58354 kgCO2eper litreS1
Petrol (average biofuel blend)2.07500 kgCO2eper litreS1
Wood pellets (direct combustion)0.01193 kgCO2eper kWhS1
Company car — diesel (average)0.17265 kgCO2eper kmS1
Van — diesel (average, up to 3.5t)0.25716 kgCO2eper kmS1
Refrigerant HFC-134a1,300.000 kgCO2eper kgS1
Refrigerant HFC-32677.000 kgCO2eper kgS1
UK grid electricity (location-based)0.13096 kgCO2eper kWhS2
Renewable electricity (REGO)0.00000 kgCO2eper kWhS2
BEV car (average, standalone)0.02686 kgCO2eper kmS2
District heat and steam0.17529 kgCO2eper kWhS2
Flight — domestic0.22928 kgCO2eper pax-kmS3
Flight — short-haul economy0.12576 kgCO2eper pax-kmS3
Flight — long-haul economy0.11704 kgCO2eper pax-kmS3
Train — national rail0.03092 kgCO2eper kmS3
Bus — local (average, non-London)0.12552 kgCO2eper kmS3
Taxi / ride-hail0.14861 kgCO2eper kmS3
Ferry — average passenger0.11270 kgCO2eper kmS3
Hotel stay — UK10.4 kgCO2eper nightS3
Freight — van (average, up to 3.5t)0.63511 kgCO2eper tonne-kmS3
Freight — HGV rigid (average, non-refrigerated)0.84606 kgCO2eper kmS3
Waste — household residual, landfill497.28993 kgCO2eper tonneS3
Waste — scrap metal, recycled4.65358 kgCO2eper tonneS3
Water supply0.19130 kgCO2eper m³S3
Water treatment0.17088 kgCO2eper m³S3
Homeworking (office equipment + heating)0.32393 kgCO2eper FTE working hourS3
Flight factors include Radiative Forcing Index (RFI) uplift and well-to-tank (WTT) emissions per DEFRA 2026 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 AR5 100-year global warming potentials, consistent with DESNZ's published methodology for the 2026 factor set.
5. Net-zero trajectory
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.
Residual emissions assumption
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.
Linear reduction rate
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.
Formula
residual_emissions = base_year_total × 0.10
linear_annual_cut = (base_year_total − residual_emissions) ÷ years_to_2050
required_rate = (linear_annual_cut ÷ base_year_total) × 100
projected(year) = base_year_total − (linear_annual_cut × years_elapsed), floored at residual_emissions
Example
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.
6. Scenario forecasting
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.
Business as usual0%No action taken. Emissions remain flat at the current year level through 2030.
Moderate action−3%/yrBasic efficiency measures — LED lighting, heating controls, travel policy. Widely achievable without capital investment.
SBTi 1.5°C pathway−4.2%/yrThe minimum annual reduction rate required under the SBTi Absolute Contraction Approach for a 1.5°C-aligned science-based target.
Ambitious−5%/yrStrong decarbonisation programme — renewable energy switch, EV fleet, supply chain engagement. Achievable with structured investment.
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.
7. Data quality tiers
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%).
Tier 1100/100Direct measurementContinuous monitoring, calibrated meters, lab analysis
Tier 280/100Site-specific activityActual consumption from invoices, utility bills, purchase records
Tier 365/100Supplier-specific dataGHG data provided directly by a supplier for their products
Tier 445/100Industry average factorsSecondary factors from DEFRA, IPCC or EPA databases
Tier 520/100Spend-based / proxyFinancial spend multiplied by economy-wide emission factors
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.
8. Carbon credit accounting
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.
Net position formula
net_emissions = gross_emissions − retired_credits
offset_progress = (retired_credits ÷ gross_emissions) × 100
runway_months = held_credits ÷ avg_monthly_emissions
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.
9. Intensity metrics
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.
intensity_per_employee = total_tco2e ÷ number_of_employees
intensity_per_million_gbp = total_tco2e ÷ (turnover_gbp ÷ 1,000,000)
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.
10. Scope 2 dual reporting
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 2026 UK electricity generation mix factor of 0.13096 kgCO2e/kWh. This figure decreased by 26.0% from the 2025 factor (0.17700 kgCO2e/kWh) following a DESNZ methodology change that reduced the data lag used to calculate the grid mix from two years to one, in addition to continued grid decarbonisation — this is a larger, more structural revision than a typical annual refresh, and worth being aware of if comparing year-on-year Scope 2 totals.
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. This residual-mix default has not been re-verified against the 2026 source as part of this update and should be treated as carried over pending confirmation.
11. Limitations and disclaimers
No third-party assurance
Paspira CarbonLedger does not perform or provide third-party limited or reasonable assurance under ISAE 3000 or ISO 14064-3. Reports generated by the platform have not been independently verified unless separately stated by the organisation. Organisations requiring assured GHG inventories should engage an accredited verification body.
Accuracy depends on input data
Emission calculations are only as accurate as the activity data entered by the user. The platform applies DEFRA 2026 factors correctly, but cannot detect incorrect, estimated or fabricated input data. Users are responsible for the accuracy of their activity data and should retain source documents (utility bills, fuel receipts, travel records) as evidence.
No life cycle assessment (LCA)
The platform does not perform product-level life cycle assessment or calculate product carbon footprints (PCF). Scope 3 categories use economy-wide DEFRA average factors, not supplier-specific primary data, except where users enter supplier-provided factors manually.
Scope 3 materiality
Not all Scope 3 categories are covered. Users should assess materiality for their specific sector and may need to add categories not included in the platform's standard activity library. Custom activities can be entered with user-supplied emission factors.
Scenario forecasts are illustrative
The scenario forecasts and net-zero trajectory are planning tools based on simplified models. They do not account for sector-specific constraints, capital availability, regulatory changes or macroeconomic factors. They should not be used as the basis for financial disclosures without independent review.
Annual factor updates
DEFRA emission factors change each year. The platform is updated annually when new DEFRA factors are published. Inventories for prior years retain the factor version applicable at the time of reporting, consistent with GHG Protocol guidance on recalculation.
Two activities not available in any DEFRA 2026 publication
Petrol company cars for Scope 1 owned fleet, and employee commuting, remain unavailable — confirmed absent by checking directly, not assumed. Petrol data does exist for Scope 3 business-travel cars and freight vans; it simply isn't published for owned-fleet passenger cars in any DEFRA sheet, current or historical. Employee commuting sits under a separate DEFRA spend-based publication not yet sourced. One further factor — average construction waste sent to landfill — has no published 2026 figure at all; this is confirmed as an absence in DESNZ's own data.
Two 2026 factors moved against the general trend
Coach travel (+42.2%) and international rail (+154.5%) both increased in the 2026 update, unlike every other electricity-linked category, which decreased. Both are verified directly against the official source. If either materially affects your reported total, we'd recommend treating the figure with additional scrutiny rather than assuming it follows the same pattern as everything else.
12. Version history
v2.3July 2026Updated to DEFRA 2026 emission factors, published 11 June 2026 — verified against both the official full-set workbook and the official flat-format data export. 118 of 199 factors confirmed via the full-set workbook; remaining gaps (35 hotel countries, freight van classes II/III/average, freight sea and air, business travel cars) closed via the flat-format cross-check. Activity library expanded from 163 to 209 verified entries with the addition of standalone BEV cars and vans, real HGV freight at actual laden percentages, wood/biomass direct combustion, district heat/steam, and petrol business-travel car and freight van factors — all previously unavailable in the condensed dataset this platform used before. UK grid electricity factor decreased 26.0% (0.17700 → 0.13096 kgCO2e/kWh) following a DESNZ methodology change, not a routine refresh. Two factors — coach travel and international rail — increased against the general trend and are flagged for extra scrutiny. One factor (average construction waste, landfill) confirmed to have no published 2026 value at all.
v2.2July 2026Full audit of DEFRA 2025 emission factors against the official published condensed-set spreadsheet. Corrected several factors that had drifted from source, including waste disposal (previously understated by up to ~1000x for organic materials), hotel stays (understated by ~163x), homeworking (unit basis corrected from per-day to per-FTE-working-hour), water supply/treatment, refrigerant HFC-134a, and several fuel and travel factors. Activity library expanded from 46 to 163 verified entries. Unverifiable factors removed from the public reference table rather than left uncorrected.
v2.1June 2026Updated to DEFRA 2025 emission factors. Net-zero trajectory changed from compound decay to linear absolute contraction consistent with SBTi methodology. Scenario forecasts updated to linear rates. Residual emissions floor added at 10% of base year.
v2.0January 2026Added data quality scoring based on ISO 14064-1 tiers. Carbon credit runway metric introduced. Scope 2 dual reporting (location + market-based) added.
v1.0September 2025Initial release. GHG Protocol Corporate Standard. DEFRA 2024 emission factors. Scope 1, 2 and 3 inventory. Basic net-zero trajectory.
Questions about this methodology?
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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