Specifying biochar in a BNG habitat management plan

Photo from London Wildlife Trust

This page is for BNG ecologists, landscape architects with BNG-mandated projects, and consultancies writing the habitat management plan that has to survive the next 30 years of monitoring. It covers the ecologist sign-off rule that protects your spec at cost review, the clause wording to lock the biochar line down, dose rates from our verified application documents, and the named research that backs the inclusion.

Carbon Gold enriched biochar is the product range we manufacture in the UK, built on hardwood-source biochar pre-charged with the Carbon Gold proprietary blend, which includes Trichoderma and Mycorrhizal Fungi. If you are defending a BNG line that is already in spec, see our Specification Defence Brief instead.

If you are writing tree pit specifications under NBS Q31 rather than a BNG plan, see our NBS Q31 Biochar Specifier Guide.

Why BNG biochar specification needs to be tighter than any other planting workBNG is different from standard landscape or tree planting work in one specific way that affects the biochar line. Every BNG habitat creation or enhancement scheme is tied to a 30-year monitoring window under POST PN 0728 (UK Parliament, September 2024). The habitat unit calculations on which planning consent was granted depend on the substrate performing for that full window.

A biochar line that is removed or substituted on a BNG scheme is not just a procurement decision. It is a Section 106 risk. If the habitat fails its monitoring, the developer is on the hook for replacement habitat creation, sometimes with a significant uplift on the original spec.

The specifier protects this by writing the clause tight enough that the QS cannot remove or substitute biochar without the ecologist of record being involved.

Critical for BNG: the ecologist sign-off rule

Where Carbon Gold biochar has been specified into a Biodiversity Net Gain habitat management plan, removal or substitution requires written approval from the ecologist of record and may necessitate revision of the BNG habitat unit calculations. The QS does not have authority to make this change unilaterally.

This is the single most important sentence the BNG ecologist can put into the specification. It does not block all substitution. It just means substitution becomes the ecologist’s decision, not the QS’s. That is the right level of control for a 30-year liability.

Framework reference: POST PN 0728 (UK Parliament, September 2024).

Why enriched biochar, not biochar, on a BNG scheme

The bigger BNG risk than line removal is line substitution with plain biochar. A specification that says only ‘biochar’ gives the QS permission to source the cheapest plain biochar on the market and call it compliant. Plain biochar is raw, uninoculated carbon. It does not contain the Carbon Gold proprietary blend, which includes Trichoderma and Mycorrhizal Fungi. On its own it can lock up nutrients and moisture in the short term before any biology colonises it. On a 30-year BNG habitat scheme, that is the exact opposite of what the habitat unit calculations assumed.

Biochar has no brain. It will suck up everything, good or bad, initially, and by the time it is doing anything good the tree, turf or plants have died.

Carbon Gold enriched biochar arrives on site with all the beneficial work already done. The carbon has been pre-charged at the point of manufacture with the Carbon Gold proprietary blend, which includes Trichoderma and Mycorrhizal Fungi. The microbiology is in place before it ever goes near the soil.

On a BNG scheme that means the habitat substrate starts working from day one of the 30-year window. Establishment-phase survival, water-holding capacity, biological habitat for soil microbes, soil structure. All running from planting day, not waiting for biology to find the biochar.

Ready-to-paste clause wording for BNG habitat management plans

This is the bit ecologists tend to bookmark. The wording below sits inside the habitat management plan, tells the QS that the biochar line is a specified product with a documented biological blend, and requires ecologist sign-off on any substitution.

“Soil amendment for habitat creation shall be enriched biochar with a documented biological blend including Trichoderma and Mycorrhizal Fungi. Application in accordance with Carbon Gold Tree Soil Improver Application Guide  and Application Calculator. No equivalent substitution permitted. Any change to specification or application rate requires written approval from the ecologist of record and may necessitate revision of BNG habitat unit calculations.”

Why each bit matters:

• ‘Enriched biochar’ rules out plain biochar substitution at cost review.
• ‘Documented biological blend including Trichoderma and Mycorrhizal Fungi’ names what makes the product effective for habitat establishment.
• ‘Application in accordance with…’ points the contractor at our verified dose documents.
• ‘No equivalent substitution permitted’ is the wording that holds the line at cost review.
• ‘Written approval from the ecologist of record’ is the BNG-specific protection. Without it, the QS can act unilaterally.
• ‘May necessitate revision of BNG habitat unit calculations’ is the Section 106 risk made explicit. It is the bit that focuses minds.

Dose rates for BNG habitat creation contexts

Carbon Gold dose rates come from our verified Tree Soil Improver Application Guide.

• Planting hole baseline: approximately 2.5 litres mixed into backfill, scaled to hole size.
• Topsoil mixing across a BNG habitat creation area: approximately 150 litres per cubic metre (10% by soil volume).
• Established trees within a BNG enhancement area: approximately 9 litres per square metre to 10 cm depth, or 18 litres per square metre to 20 cm (5% by soil volume).
• Top dressing for established BNG habitat: approximately 2.25 litres per square metre at 25 mm depth, raked in and covered with mulch.

For per-tree-size detail by container size, bare-root whip height, or standard tree girth.

Three substitution traps that turn up at BNG cost review

1. The QS swaps Carbon Gold biochar for biochar or plain biochar on cost grounds. The ecologist sign-off clause above blocks this. Without it, the QS can act alone.
2. The line is removed entirely on the day-one cost saving. The 30-year monitoring failure risk and the Section 106 implications need to be in front of whoever makes the call. The Specification Defence Brief carries the lifecycle exposure arguments.
3. The compost line is kept and the biochar removed. Where a generic compost or soil conditioner sits alongside the biochar line, suggest substituting the compost line for Carbon Gold Soil Improver. Approximately cost-neutral, delivers the resilience benefit, satisfies the habitat unit calculations.

For the full defence playbook, see our Specification Defence Brief.

The published evidence base

Specifiers and ecologists like to know what is behind a spec before they put their name to a 30-year liability. The evidence base for Carbon Gold enriched biochar, which carries the Carbon Gold proprietary blend including Trichoderma and Mycorrhizal Fungi, is independent and published.

Field trials by Bartlett Tree Research Laboratory under Dr Glynn Percival at the University of Reading cover European beech transplant survival (mortality moved from 60 percent in the untreated control to 0 percent in the Carbon Gold treatment), urban tree establishment, apple-scab field observation, and Chalara-affected ash on a Woodland Trust site in Essex. Findings have been reported in Pro Arb Magazine, HortWeek and the Guardian.

The peer-reviewed industry review is Schaffert, Lukac, Percival and Rose 2022, Arboriculture & Urban Forestry 48(3). For mechanism, Joseph 2021 in GCB Bioenergy. For water retention, Razzaghi 2020 meta-analysis in Geoderma.

Findings reported here are the researchers’ observations.

About Carbon Gold. Carbon Gold Ltd is a B Corp certified company supplying enriched biochar into Biodiversity Net Gain habitat management plans. Its Managing Director Sue Rawlings is the named Grantee of the company’s Royal Warrant by Royal Appointment to HM The King. Carbon Gold has been featured in industry press covering ecology, arboriculture and habitat creation. See our Biochar in Practice hub and the frequently asked questions for more.

Speak to the Carbon Gold team

Specification queries, datasheets, NBS-style clause wording, technical support on cost-review questions, or help putting the ecologist sign-off clause into your habitat management plan.

Call 0117 244 0032 or use the contact form.

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