The partnership in brief
The partnership brings together Carbon Heroes' expertise in procurement-driven climate finance and council-approved delivery infrastructure with Simetrica-Jacobs' methodological leadership in wellbeing and social value measurement. The output is a defensible proxy value for air pollution removal, designed specifically for the public sector procurement context — rigorous enough for evaluator scrutiny, practical enough for a Bid Manager to use on a live tender.
“Simetrica-Jacobs created a simple, user-friendly yet rigorous social value tool that meets our requirements for social value reporting to funders and councils. We look forward to further developing the tool and evidencing the social value of urban greenspaces.”
The evidence gap the partnership closes
Two pieces of prior research framed the work. A 2014 UCL roundtable on greenspace valuation concluded that better, multi-benefit valuation tools were needed if greenspace investment was to be evaluated alongside other public goods. Six years later, a 2020 National Trust report, published in the wake of the first COVID-19 lockdown, revealed persistent inequality of access to nature across UK urban communities — and the acute dependency on greenspace that emerged when people could not travel for leisure.
Most recently, the World Health Organization's 2023 Urban Green Spaces and Health report recommended that wellbeing valuation approaches be applied to greenspace interventions, using pre- and post-intervention evaluations of resident wellbeing to quantify the causal uplift.
Carbon Heroes and Simetrica-Jacobs designed the partnership to operationalise this evidence base for the UK procurement context — giving bid teams a defensible way to quantify the air quality benefits of urban tree interventions in tenders under PPN 002 and the Procurement Act 2023.
What the partnership delivers
The joint work produces a proxy value for air pollution removal by urban trees, monetising the direct and indirect (through an improvement in health) wellbeing benefit of NO₂, PM2.5, and PM10 interception by tree canopies. The value is derived from NHS National Cost Collection data and Defra air quality damage cost guidance, capturing the downstream benefits of avoided GP visits associated with the pollution reduction.
The proxy sits within Carbon Heroes' broader social value methodology, which also covers carbon sequestration and storage (HM Treasury Green Book), greenspace amenity (CABE benchmarks), volunteering (IES), and local economic impact (LM3) — all of which are quantified through separate, independently sourced proxies. The air pollution proxy developed with Simetrica-Jacobs fills the gap that previously existed in linking tree canopy interception to monetised health outcomes with the rigour that evaluators demand.
As we know its relevance to many local authorities, the methodology is built to augment the National TOMs framework rather than replace it. Every number is traceable to a published source.
Why it matters for public sector bidders
For suppliers bidding into UK public sector contracts, the partnership turns a historically qualitative claim — “improved air quality” — into a quantified, evidence-backed commitment that stands up to evaluator scrutiny. That is the shift that separates an upper-quartile social value response from a generic one.
Nature-based interventions remain one pillar of a well-rounded social value strategy, and the Carbon Heroes x Simetrica-Jacobs tool is designed to be used alongside apprenticeships, local employment, skills development and community engagement commitments — weighted to whatever the tender prioritises. The partnership sharpens what is monetisable about the nature-based pillar; it does not claim to do the whole job.
About the organisations
Carbon Heroes is a UK technology company founded by Violette Castagné, enabling public sector suppliers to deliver credible, quantified social value through supporting nature-based interventions, delivered via council-approved partners. BidBooster, its AI-powered bid generation tool, produces submission-ready environmental social value content in minutes.
Simetrica-Jacobs is a leading international consultancy specialising in social value research, wellbeing economics, and impact measurement. The firm's work underpins HM Treasury's WELLBY methodology in the Green Book and has shaped social value practice across the UK public sector.
References
- Defra, Air Quality Damage Cost Guidance
- Public Health England, Review of Interventions to Improve Outdoor Air Quality and Public Health
- WHO, Urban Green Spaces and Health: A Review of Evidence (2023)
- National Trust, Levelling Up Greenspaces (2020)
For media enquiries, please contact: contact@carbon-heroes.com