For most shipowners, Purchased Goods and Services is the largest unaddressed source of supply-chain emissions, and the one with the weakest data behind it. The spend-based method is accepted under the GHG Protocol, but the uncertainty it carries is becoming a material problem under CSRD, CBAM, and tightening charterer requirements.
A higher data-quality standard for Scope 3 is no longer optional. Spend-based estimates are increasingly seen as a starting point that must come with a documented improvement plan.
From 2025 onwards, in-scope companies must report Scope 3 emissions with increasing specificity. ESRS require operators to explain their data quality and credible improvement plans.
The Carbon Border Adjustment Mechanism creates precedent and political momentum for supply-chain carbon accounting across sectors, well beyond the products it directly covers.
Large cargo owners are embedding Scope 3 supplier data requests into procurement and tendering. Spend-based estimates are no longer considered sufficient by leading buyers.
The 2024 GHG Protocol consultation included submissions calling for the spend-based method to be phased out as a primary calculation approach. The direction of travel is toward supplier-specific verified data.
The spend-based method multiplies what you pay each supplier by an Environmentally Extended Input-Output (EEIO) factor for that supplier's sector. The structural sources of uncertainty add up quickly.
One EEIO factor covers an entire sector. Pumps, cranes, safety gear, and electronics share the same number, despite very different emission profiles.
A Chinese yard and a Norwegian one appear identical in a global EEIO table, despite large differences in grid carbon intensity and process efficiency.
Spend-based factors cannot distinguish a low-carbon product variant from a conventional one. Supplier improvements stay invisible in your numbers.
Input-output tables update infrequently. Inflation and FX movement inflate spend without changing physical volume, distorting the emission estimate.
A shipowner spends USD 1,862,873 with a marine paints supplier. The EEIO factor for the paints sector is 0.59 kg CO₂ per USD. The estimated emission is approximately 1,099 t CO₂e.
That figure says nothing about whether the paint is water-based or solvent-based, produced with renewable energy, or carrying a third-party verified EPD.
Anonymised analysis of a single fiscal year, mixed fleet. Spend figures in USD. Calculations follow the GHG Protocol Corporate Value Chain Standard, with EEIO-based emission factors per account category.
| Category | Spend (USD) | Emissions (t) | Share | Intensity (kg/USD) | Uncertainty |
|---|---|---|---|---|---|
| B2 · Vessel — Technical | 11,510,245 | 2,652.7 | 32.9% | 0.230 | ±55% |
| B0 · Vessel — Provisions | 2,356,111 | 1,967.4 | 24.4% | 0.835 | ±60% |
| B8 · Dry-Dock | 9,921,602 | 1,966.1 | 24.4% | 0.198 | ±65% |
| B1 · Vessel — Stores | 3,794,364 | 1,371.2 | 17.0% | 0.361 | ±50% |
| B5 · Vessel — Crew | 2,320,939 | 281.6 | 3.5% | 0.121 | ±40% |
| B7 · Vessel — Misc | 1,738,733 | 198.0 | 2.5% | 0.114 | ±70% |
Provisions (B0) and Dry-Dock (B8) carry the highest emission intensity per USD. Technical (B2) carries the largest absolute volume due to breadth of spend.
Emission risk is concentrated. That makes targeted supplier engagement tractable, rather than overwhelming.
Of the 20 largest suppliers by estimated emission volume, only 2 had publicly available product carbon footprint data as of March 2026. Most have active sustainability programmes and net-zero commitments, but no product-level emission values that could replace the spend-based estimate.
Based on GHG Protocol Technical Guidance on uncertainty, EEIO validation studies, and category-specific analysis. The current baseline of 8,057 t may be closer to 4,000–5,600 t once primary data lands. The difference affects target credibility, intensity metrics, and your position in charterer assessments.
Why this matters for baseline integrity. A company cannot claim credit for supplier decarbonisation it cannot measure. If a key supplier switches to a lower-carbon product, or a drydock installs renewable energy, the spend-based method will never capture it. The numbers simply do not move.
Engaging fifteen to twenty suppliers realistically covers 70–80% of the emission footprint with primary data. The remaining tail continues on spend-based methods, with documented data-quality narrative for CSRD reporting.
Run the Category 1 hotspot analysis. Identify the 5–20 supplier targets. Set the baseline data-quality narrative for CSRD reporting.
Engage the top five suppliers. Provide PCF tooling. Replace spend-based estimates for the largest concentrations with primary or supplier-specific data.
Extend to the next 10–15 suppliers. Document the improvement plan. Report progress in line with ESRS data-quality expectations.
The International Marine Purchasing Association's SAVE program is the industry's effort to align responsible procurement and environmental data. The IMPA Maritime Environmental Footprint (IMEF) Initiative gives shipowners, suppliers, and charterers a shared, activity-based standard for product carbon footprint, built on GHG Protocol, ISO 14067, and PACT Pathfinder 2.0 foundations.
Working within IMEF means the data you collect is portable across buyers, not built for a single client.
Visit the IMEF initiativeWe work with shipowners and their key suppliers to replace sector averages with product-level emission factors aligned with IMEF. Verified results feed into ClimateBase, our growing database of supplier-specific maritime emission factors.
We map your Category 1 footprint, identify the suppliers that determine your baseline, and guide the engagement programme to bring primary data into your reporting.
We help maritime suppliers calculate IMEF-aligned product carbon footprints in a format charterers and shipowners accept. Better data, fewer ad-hoc requests, stronger commercial position.
Verified PCFs feed into ClimateBase, our supplier-specific maritime emission factor database. The result is fewer assumptions across the industry, not just inside one company's reporting.
Calculations follow established frameworks. GWP conversion uses IPCC AR5 (CO₂ = 1, CH₄ = 28, N₂O = 265). Variance estimates are directional and based on published GHG Protocol Technical Guidance and EEIO uncertainty literature.
We sit with your sustainability and procurement leads, walk through your Category 1 spend distribution, identify the suppliers that determine your baseline, and outline a defensible transition plan in line with CSRD expectations.
One export from your finance or procurement system is all we need to get started.
For shipowners, ship managers, and maritime suppliers.