The Holdfast Standard
A holdfast is what anchors kelp to rock through an Atlantic winter. It is also the only part of the plant that never lets go.
Sponsorship without proof is a donation with better photography.
The first version of this business asked people to trust us. We measured what we could, reported when we remembered, and awarded ourselves the credit for it. When the reporting slipped - and it did - there was little underneath holding the proposition up.
The Holdfast Standard is the correction. It is the part of Carbon Kapture that is genuinely hard to copy, because it is not a technology or a licence. It is five years of knowing which measurements on a seaweed farm mean something and which ones are decoration.
What we actually measure.
Weighted towards Land, because that is where the benefit is most defensible and most immediate. Nothing here is a carbon claim.
Ocean
What the rope does for the water it hangs in.
Weighting: 35% of the overall score
Species recruitment
Settlement plates and line surveys, start and end of season, counted against an unseeded control line at the same site.
eDNA sampling
Water samples at deployment and harvest, processed by an accredited lab, compared to a baseline taken before the farm existed.
Habitat area
Three-dimensional surface created per metre of line, derived from measured blade area rather than assumed.
Site condition
Licence compliance, gear loss, entanglement records and benthic impact under the moorings.
Land
What happens after the harvest comes ashore.
Weighting: 40% of the overall score
Tonnage and distance
Weighbridge or verified boat-side weight, and the actual road distance from pier to field. Both are published.
Soil organic matter
Sampled on participating fields before first application and at the same points each subsequent year.
Agronomic effect
Yield or input substitution recorded against an untreated strip on the same holding, where the farmer will allow it.
End-use honesty
Where harvest goes to research rather than to a field, it is scored as research and not as land benefit.
People
Whether the money actually reaches the coast.
Weighting: 25% of the overall score
Share to the farm
The proportion of each sponsored pound that reaches the grower, itemised on every invoice we issue.
Jobs and hours
Full-time equivalents and seasonal hours supported, stated as a count rather than a multiplier.
Ownership and control
Who owns the operation, where surplus goes, and whether an asset lock exists.
Land farm benefit
The market value of harvest delivered free, stated in pounds, so the transfer is visible.
How a farm gets scored.
Site visit and baseline
We go. Someone stands on the boat, sees the gear, meets the land farmer and takes the first samples. No farm is scored from a questionnaire.
Season of evidence
Sampling runs from seeding to harvest and through to land application. Missing data is scored as missing, not estimated.
Compilation and challenge
We build the score, then try to break it. Every claim has to survive the question a sceptical corporate buyer would ask.
Independent review
An academic partner reviews methodology and evidence and signs off, or does not. Provisional scores are labelled provisional.
Publication
The score, the pillar breakdown and the weaknesses go on the farm’s page. Including the ones that make us look bad.
Annual reassessment
Nothing is carried forward. A farm earns its rating again every year or loses it.
The things the evidence does not support.
Every one of these would make the sales conversation easier. None of them survives the literature, so none of them appears anywhere on this website.
Carbon sequestration
Harvested seaweed does not lock carbon away. Expert assessment calls the potential overstated, and Natural Resources Wales describes harvested cultivation as largely transient storage. We do not sell offsets and we do not imply them.
Methane reduction from kelp feed
The dramatic results belong to Asparagopsis, a warm-water red seaweed we do not grow. A twelve-week trial feeding ensiled sugar kelp to lactating cows found no methane effect at all. Our feed work is research, and we will call it research until it is not.
Soil carbon storage
Yield uplift from seaweed biostimulants is well evidenced, averaging around 16% across nearly two hundred studies. Durable soil organic carbon gain is not. We measure soil organic matter because it is worth knowing, not because we are claiming it.
Guaranteed biodiversity gain
Farmed lines can carry far more epibionts than wild kelp, and can also carry fewer species per plant. One Norwegian farm underperformed nearby wild forest on every measure. Site-by-site evidence in each case.
About the Standard.
Why not use an existing standard?
Because none of them measure this. Carbon standards measure carbon, and the carbon case for harvested seaweed is genuinely weak - peer-reviewed assessments describe the sequestration potential as overstated, and Natural Resources Wales treats harvested cultivation as largely transient storage. We would rather not build a business on a number the literature does not support.
What the evidence does support is habitat creation, agronomic benefit and coastal income. There was no standard measuring those three together for seaweed. So we built one.
Who reviews the scores?
We compile. An independent academic partner reviews and signs off annually. That separation is deliberate: a self-awarded standard is closer to a logo than a standard. Our research relationships run through Bournemouth University, UCL, the University of Graz and Atlantic Technological University.
What is the minimum score?
5.5 out of 10, overall, with no individual pillar below 4.0. A farm that scores below either threshold does not appear on the site and cannot take sponsorship money through us. We publish the count of farms assessed and the count that failed.
Can a farm lose its rating?
Yes. Scores are reassessed every year on fresh evidence, not carried forward. A farm that stops sampling, stops delivering to land, or loses its licence loses its place. Sponsors on a multi-year commitment at a delisted farm are moved to another site at no cost.
Do you claim carbon offsets?
No. Nothing in this network is a verified carbon credit and none of it can be used against a science-based target. It is beyond value chain mitigation. It is better said upfront than discovered later.
Is the methodology public?
It will be. All 106 data points, the weighting, the evidence requirements and the review process are being written up for publication alongside the first full assessment round. A standard nobody can inspect is not worth much.
See it applied to a real farm.
Every farm page carries its full pillar breakdown, including where it scores badly and why.