Litre-Deep and Carbon-Blind: Why UK Fuel Cards Need an Intensity Field

A fuel card statement is a remarkably efficient document. To the penny, it records how many litres went into which vehicle, at which forecourt, at what time and on what date. What it does not record is the carbon intensity of the fuel that came out of the nozzle. For two decades that omission was defensible: diesel was diesel, and the only variables that mattered were price and volume. In 2026, with hydrotreated vegetable oil, bio-LNG and a lengthening list of blended lower-carbon products arriving in UK depots, the gap has become a reporting liability rather than a convenience.

The litre was never a unit of carbon

Consider two tank fills of identical volume. The first is conventional mineral diesel, carrying roughly 2.6 kilogrammes of CO2 equivalent per litre once combusted. The second is a certified waste-derived paraffinic diesel, sold as HVO100 to the EN 15940 standard, with a reported lifecycle figure in the region of 0.2 kilogrammes per litre. The card statement treats them as the same event. The sustainability report, the scope 1 return and the customer tender all treat them as entirely different ones.

That divergence will widen. Blends shift by season and by supplier. Feedstock moves between used cooking oil, tallow and technical corn oil, and each carries its own intensity. A depot that has quietly moved half its mileage onto a lower-carbon drop-in fuel has, in most card systems, no machine-readable evidence of having done so beyond a supplier's PDF and a purchase order.

What the field should actually contain

A carbon-intensity field is not a single number. It is a small, structured record attached to each transaction, and the useful version has five parts.

First, the intensity itself, expressed in grammes of CO2 equivalent per megajoule on a lifecycle basis and calculated using the methodology already applied under the Renewable Transport Fuel Obligation. Second, the feedstock and its classification, which determines whether the fuel counts as waste-derived, residue-based or crop-based. Third, the blend ratio and the standard the product meets. Fourth, a certification reference: the voluntary scheme under which the fuel was verified, such as ISCC EU or REDcert, together with the mass-balance period to which it belongs. Fifth, a consignment or batch identifier that connects the litre in the tank back to the paperwork behind it.

None of this is exotic. Fuel suppliers already hold most of it in order to claim Renewable Transport Fuel Certificates. The problem is not that the data does not exist; it is that the card statement sits outside the chain that carries it.

The audit trail is the point

An intensity figure with no evidence behind it is a green claim waiting to be tested. The Competition and Markets Authority has been consistent that environmental statements must be substantiated and not misleading, and fleet customers are beginning to ask the question their own auditors ask: show us the chain from nozzle back to feedstock.

For operators inside scope of the Streamlined Energy and Carbon Reporting regulations, and for those preparing for the UK's incoming sustainability reporting standards, the practical difficulty is granularity. Annual supplier totals are enough for a headline figure and useless for apportioning emissions to a specific contract, a specific customer's lane or a specific vehicle. Transaction-level intensity turns an estimate into a record.

Three objections, and how much weight they carry

The first is fragmentation. UK fuel cards are issued by a handful of large providers and accepted across a shared forecourt network, and none of them has an obvious incentive to move first. This is real but not decisive: the data standard can be agreed in advance of the systems, and a single issuer offering the field would create commercial pressure on the rest.

The second is data quality. If a supplier simply self-declares an intensity, a seller of overstated litres could mislead a fleet. The answer is the same one used elsewhere in fuel assurance: tie the field to third-party certification and make the certificate reference auditable, not merely printable.

The third is cost. Adding columns to a transaction record is cheap; reconciling them across a supply chain is not. But compare that cost with the alternative, which is a fleet making lower-carbon purchases it cannot prove and publishing emissions disclosures it cannot defend.

What to ask for now

Fleet managers do not need to wait for a standard to be blessed before testing the market. Six questions put to a card provider or fuel supplier will establish how close they are.

• Does your transaction data carry a lifecycle carbon intensity in grammes per megajoule, or only litres and grade?
• Can you give me feedstock, blend ratio and fuel standard for each delivery, rather than each quarter?
• Which certification scheme verified the claim, and under which mass-balance period?
• Can you supply a batch identifier linking a transaction to your RTFO evidence?
• Can I export that data in a stable, documented format, by API or scheduled file, without raising a change request?
• Will you warrant the accuracy of the intensity figure in contract and accept a right of audit?

A supplier that answers all six is worth a serious conversation. A supplier that answers none is still selling compliance by the litre.

The bottom line

Fuel cards were built to control spend, and they do that well. They were not built to carry environmental evidence, and they now need to. The shift to lower-carbon fuels will be judged not on how many depots trialled a drop-in product but on how many can prove, line by line, what they burned. That proof has to start at the nozzle, and it has to arrive with the invoice.