Sustainability Studio (Guardian)
Follow the evidence behind an environmental claim.
Guardian is the open-source policy engine, released under the Apache 2.0 licence, that turns an environmental methodology into a digital workflow for measurement, reporting, verification and issuance on Hedera1. ColdAI deploys and operates Guardian for issuers, registries and corporate buyers: modelling methodologies, connecting evidence sources and running the platform. This page explains the moving parts, who does what in a programme and where Guardian's responsibility stops.
The opportunity
Start with a decision
worth improving.
A project submits measurements for an environmental claim. Reviewers need to trace the methodology, source records and decisions rather than treating a token as proof of impact.
From possibility to a working system
Follow the flow.
Three connected decisions. One considered architecture.
Conceptual flow, not a live system or measured result.
Model the methodology
Translate the chosen program's requirements into data schemas and workflow roles. Define who collects, validates and reviews evidence, with qualified specialists owning the methodology.
Preserve the evidence chain
Connect source records, attestations and review decisions. Keep versions and exceptions visible so an auditor can understand which evidence supported a particular outcome.
Track the lifecycle
Integrate approved issuance and subsequent lifecycle events with registry and reporting processes. Distinguish issuance, transfer and retirement in both records and user-facing claims.
The work, made concrete
What we can build
with your team.
We agree scope, dependencies and acceptance criteria before delivery. Your project can start with an assessment, a pilot or an integration into an existing system.
Policy and evidence workflow design
Clarify the system boundary, the responsible owners and the decisions the architecture needs to support.
Guardian integration and data mapping
Turn the agreed design into reviewable work, evaluated against representative inputs and explicit success criteria.
Lifecycle traceability and review views
Make the next step operable: document responsibilities, known limitations and the path from pilot to ongoing use.
Explore the practice
Further capabilities
and implementation detail.
What Guardian (Sustainability Studio) is
Guardian is Hedera's open-source policy engine for tokenising and tracking environmental assets — carbon credits, RECs, biodiversity credits, plastic credits, and more. It models real-world methodologies (Verra, Gold Standard, ICVCM, EPA, and others) as policies with schemas, decentralised identities, and HCS-anchored audit trails. The result is environmental claims that are verifiable end-to-end, from project data to issued token.
ColdAI's Guardian service
Methodology implementation
Implement Verra, Gold Standard, ICVCM, and bespoke methodologies as Guardian policies — schemas, workflows, and approval chains.
Audit-grade evidence
HCS-anchored evidence pipelines that meet auditor and registry expectations for traceability and immutability.
Token issuance & retirement
Issue environmental tokens on HTS with proper retirement, double-counting prevention, and registry interoperability.
Buyer & registry integration
Integrate corporate buyers, marketplaces, and traditional registries into a single verifiable system of record.
Programmes we deliver on Guardian
- Voluntary carbon programmes (VCM)
- Renewable energy certificate (REC) issuance
- Biodiversity and nature-based credits
- Plastic credits and circular-economy tokens
- Corporate insetting and Scope 3 attestations
Deploy verifiable environmental assets
Engage ColdAI to deliver a methodology-aligned, auditable environmental asset programme on Hedera using Guardian.
Contact our Hedera teamIn depth
Go deeper: building and hosting Guardian
Two working guides for teams about to commit: how a written methodology becomes a policy, and how to choose where Guardian runs.
- 01ProcessTurning a Carbon Methodology into a Guardian PolicyA step-by-step process for turning a carbon methodology into a Guardian policy workflow: schemas, roles and DIDs, workflow blocks, MRV data and dry runs.
- 02Buyer's guideSelf-Hosted Guardian vs Managed Service vs Custom MRVChoosing between self-hosted Guardian, a managed Guardian service or a bespoke MRV platform: control, operating burden, residency, lock-in and exit questions.
Guardian's building blocks in plain terms
Most confusion in early Guardian projects comes from vocabulary. These are the terms that recur in every design conversation.
- Policy
- The digital form of a methodology: a configured workflow of blocks that collects documents, routes reviews, runs calculations and triggers minting. Guardian's Policy Workflow Engine tracks each workflow's state and determines the next permitted action2.
- Schema
- A structured definition of the data a workflow step needs, such as a monitoring report's fields, types and units. Documents completed against a schema are issued as verifiable credentials.
- Verifiable credential and presentation
- A credential is a set of tamper-evident claims that cryptographically show who issued them; a presentation packages data from one or more credentials so its authorship can be checked2.
- Decentralised identifier (DID)
- A W3C identifier tied to a document that holds the keys a participant uses to prove control2. Registries, developers and verifiers act through their DIDs, so each signature traces to an accountable party.
- Standard Registry
- The Guardian account type that publishes policies and anchors trust for the programme it runs, typically a standard body, registry or programme operator.
- TrustChain
- Guardian's chain-of-custody view, built from verifiable presentations, that traces an asset's history from its creation to its current state3.
- Storage and trust layer
- Documents are stored on IPFS through a pinning service such as Filebase or a local node, while the Hedera network acts as the trust layer1.
Who takes part in a Guardian programme
A policy is shared infrastructure. Each party works through it under its own identity and sees only what its role allows.
- Published policy
Defines the steps, roles, schemas and calculations every participant follows.
- Standard Registry
Publishes the policy, approves participants and authorises issuance.
- Project developer
Registers projects and submits monitoring reports with their evidence.
- Validation and verification
The accredited body that validates projects and verifies reported results.
- MRV data sources
Meters, sensors, laboratory systems, remote-sensing providers and manual uploads.
- Hedera network
Records policy messages on consensus topics and holds issued tokens.
- Buyers and marketplaces
Inspect the trust chain before purchase and record retirement.
Where Guardian's responsibility ends
Guardian makes the path from evidence to issuance inspectable. It does not decide whether a methodology is sound, whether a project is additional or whether a verifier is competent. Those judgements stay with the standard body that owns the methodology, the accreditation system behind each verifier and, on the demand side, buyers' own due diligence.
Scheme-level integrity questions, such as preventing the same tonne being claimed twice, recording retirement consistently across registries or matching energy certificates to consumption, sit above any single platform and are covered on our certificates and carbon credits hub. Guardian can implement the rules a scheme sets. It cannot set them.
ColdAI's role follows the same line. We translate a methodology owner's requirements into a policy, connect the data and operate the platform, while the methodology owner and accredited verifiers remain answerable for the claims the tokens represent.
Is Guardian the right tool for your programme?
- If
You run a standard, registry or programme and want issuance backed by a traceable evidence workflow.
ThenDigitise the methodology as a Guardian policy and run it as the programme's system of record for issuance.
This is the role Guardian was built for: the registry publishes the policy and every participant works through it.
- If
You develop projects under a programme that already operates a Guardian policy.
ThenJoin that policy as a participant rather than standing up your own instance.
Your obligations come from the registry's published policy, not from a deployment of your own.
- If
You buy credits and want to check their provenance.
ThenUse the issuing programme's trust chain views and ask sellers for token and policy identifiers.
Checking provenance needs read access to the evidence chain, not a separate platform.
- If
Your methodology depends on continuous data such as metered energy or sensor readings.
ThenDesign the MRV integration first, with data-quality checks that run before submissions reach reviewers.
Automated feeds spread errors as efficiently as they save manual effort.
- If
You only need to publish retirements from an existing registry in tamper-evident form.
ThenConsider anchoring registry events on Hedera Consensus Service instead of running a policy engine.
A full Guardian deployment brings operating work that a simple publication need does not justify.
How ColdAI takes a programme onto Guardian
The sequence below is the outline; the detailed build method is in turning a methodology into a policy.
Scope methodology and participants
Agree the methodology version, roles and registry requirements in scope, and record who owns each judgement.
Map data to schemas
Trace every parameter the methodology needs to a source system or upload, with units, frequency and quality rules.
Build and dry-run the policy
Configure blocks, roles and calculations, then exercise them in Dry Run mode, which simulates execution without changing anything in the live environment4.
Stand up and secure the platform
Provision the chosen hosting route, Hedera accounts, IPFS storage and key custody, with monitoring and backups.
Connect buyers and registries
Integrate marketplaces, buyer portals and external registry processes so issuance, transfer and retirement are recorded consistently.
Operate and evolve
Apply Guardian upgrades, release new policy versions as methodologies change, and support reviewers and auditors tracing a claim.
Inputs to settle before digitising a programme
Frequently asked questions
Is Guardian free to use?
The software is open source under the Apache 2.0 licence, so there is no licence fee1. Running it is not free: you pay for infrastructure, IPFS storage, Hedera network fees in HBAR, and the people who build policies and operate the platform. A managed offering turns some of those costs into a service fee, which the deployment options guide weighs against self-hosting.
Does a token issued through Guardian prove environmental impact?
No. It shows that issuance followed a published policy and links to the evidence and approvals behind it. Whether the underlying activity delivered the claimed benefit depends on the methodology, the quality of the data and the competence of the verifier. Guardian makes those inputs visible for scrutiny; it does not replace the scrutiny.
What kinds of environmental assets can Guardian handle?
Guardian describes itself as a platform for digital environmental assets such as carbon credits, renewable energy certificates and biodiversity credits1. Other claims, plastic credits for example, can be modelled where a methodology defines the data, calculations and approvals. The practical limit is less the asset type than whether the methodology can be expressed as structured data and role-based reviews.
Who maintains the Guardian codebase?
Guardian is developed in the open on GitHub. In March 2026 Hashgraph said it would take a larger role in open-source development alongside Climission, a company founded by the co-founders of Envision Blockchain, which had been core maintainer since 20215. Climission runs the Managed Guardian Service. Check the repository's recent activity and release notes before committing to a version.
Can Guardian work alongside registries such as Verra or Gold Standard?
It can, but the arrangement depends on the registry. Some programmes use Guardian as the issuance workflow and keep a registry as the listing of record; others mirror registry events into Guardian for traceability. Each integration needs the registry's agreement and an interface it supports, so confirm both before designing data flows, and never allow one unit to be issued or retired in two places without reconciliation.
What does ColdAI do in a Guardian project?
We implement methodologies as Guardian policies, design evidence workflows and data mappings, integrate issuance, transfer and retirement with buyer and registry systems, and deploy and operate the platform. Before starting we ask for a specified methodology or programme, accountable verification participants, and access to source data and registry requirements.
Sources
- Guardian repository and README — Hashgraph on GitHub
- Guardian glossary — Guardian documentation
- TrustChain — Guardian documentation
- Dry Run mode — Guardian documentation
- Hedera Guardian 2026: The Next Chapter — Hashgraph
Connect the architecture
The next connection.
Explore the complementary capabilities that can turn an individual technology into a complete workflow.
Your next move
Bring us the
real problem.
A workflow that takes too long. A system that cannot connect. An idea that needs a technical path. Start there, and we can define what to investigate, build and measure.
- A specified methodology or program
- Accountable verification participants
- Source data and registry requirements