docs: Add Gold Standard metered energy cooking v1.2 and v2.0

Signed-off-by: Gautam Prajapati <gautamprajapati06@gmail.com>

Author: gautamp8

Methodology Library/Gold Standard/Metered Energy Cooking/MECD 431_V1.2.policy

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+# MECD v1.2 — Metered & Measured Energy Cooking Devices
+
+> **A newer version is available.** This is the v1.2 policy bundle, used by
+> the first MECD live deployment (ATEC × Earthood, GS11815 / GS11817, the
+> first fully digital Gold Standard cookstove issuance). For new projects we
+> recommend the Paris-Agreement-aligned [v2.0 policy](MECD%20v2.0/) instead.
+> Existing v1.2 projects can stay on v1.2 until their current crediting period
+> ends — see the [migration guide](MECD%20v2.0/migration-from-v1.2.md).
+
+## Table of contents
+
+<!-- TOC -->
+
+- [Introduction](#introduction)
+- [Why MECD](#why-mecd)
+- [Workflow at a glance](#workflow-at-a-glance)
+- [Policy guide](#policy-guide)
+  - [Available roles](#available-roles)
+  - [Quantification methods](#quantification-methods)
+  - [Important documents and schemas](#important-documents-and-schemas)
+  - [Token (carbon credit)](#token-carbon-credit)
+  - [Step by step](#step-by-step)
+    - [Registry (Gold Standard) flow](#registry-gold-standard-flow)
+    - [Project Proponent flow](#project-proponent-flow)
+    - [VVB flow](#vvb-flow)
+- [Direct device measurement (vs. sample-based)](#direct-device-measurement-vs-sample-based)
+- [Where this fits in the methodology lifecycle](#where-this-fits-in-the-methodology-lifecycle)
+
+<!-- /TOC -->
+
+## Introduction
+
+Roughly 2.3 billion people still cook over open fires or basic biomass stoves.
+The smoke causes ~3.2 million premature deaths a year (WHO), most of the wood
+comes from non-renewable sources, and the soot is a measurable short-lived
+climate forcer. Clean-cookstove projects swap those stoves for efficient
+electric, LPG, biogas, or advanced biomass devices, and earn carbon credits
+for the avoided emissions.
+
+Cookstoves are one of the largest single project types in the voluntary
+carbon market — but they've also been one of the most over-credited. A 2023
+[University of California, Berkeley study](https://assets.researchsquare.com/files/rs-2606020/v1/c2e6a772-b013-49f9-9fc4-8d7d82d4bebc.pdf?c=1678869691)
+found cookstove projects across all major standards over-credited by ~9× on
+average. Gold Standard's Metered & Measured Energy Cooking Devices (MECD)
+methodology was the closest to ground-truth (~1.3× over-credit), because it
+monitors fuel and energy use directly per device instead of extrapolating
+from sample surveys.
+
+This Guardian policy implements MECD v1.2 end-to-end: project listing →
+validation → monitoring → verification → token mint, with every step
+recorded as a verifiable credential on the Hedera ledger. It was used for
+ATEC's PoA GS11815 / VPA02 (GS11817) — the first fully digital MECD
+issuance, verified by Earthood and minted on Hedera in 2024.
+
+## Why MECD
+
+Cookstove projects support SDGs 3 (health), 5 (gender), 7 (energy), and 13
+(climate). To stay defensible, the methodology behind a project has to give
+accurate — or at least conservative — emission reductions. Several existing
+cookstove methodologies don't:
+
+- [GS-TPDDTEC](https://globalgoals.goldstandard.org/407-ee-ics-technologies-and-practices-to-displace-decentrilized-thermal-energy-tpddtec-consumption/) and [GS-Simplified](https://globalgoals.goldstandard.org/408-ee-ics-simplified-methodology-for-efficient-cookstoves/) — sample-based, prone to overcrediting.
+- [CDM-AMS-II-G](https://cdm.unfccc.int/methodologies/DB/GNFWB3Y6GM4WPXFRR2SXKS9XR908IO), [CDM-AMS-I-E](https://cdm.unfccc.int/methodologies/DB/JB9J7XDIJ3298CLGZ1279ZMB2Y4NPQ) — older CDM methodologies, less commonly used.
+- **[GS-MECD](https://globalgoals.goldstandard.org/news-methodology-for-metered-measured-energy-cooking-devices/) — the one this policy implements.**
+
+The Berkeley study mentioned above found MECD to be the closest match to
+real ground-truth emissions of any major cookstove methodology, because it
+demands per-device measurement instead of extrapolation. That same property
+makes it well-suited to digital MRV (which is what this policy is for): if
+your meter is already capturing data continuously, the path from raw data to
+audit-ready credit can be automated.
+
+This Guardian policy is the digital implementation of MECD v1.2, following
+[Gold Standard's typical project lifecycle](https://academy.sustain-cert.com/wp-content/uploads/sites/3/2021/10/GS-Project-Cycle_15042021_Annyta.pdf).
+
+
+## Workflow at a glance
+
+The path from project listing to minted credits:
+
+1. **VVB applies and is approved** by Gold Standard.
+2. **Project Proponent submits a PDD** describing the project, baseline,
+   and methodology choice (M1 or M2).
+3. **Gold Standard lists the project**.
+4. **Project Proponent assigns a VVB** to validate the PDD. The VVB
+   submits a validation report; Gold Standard approves it.
+5. **Project Proponent submits a monitoring report** for the period. The
+   metered data flows in from the project's measurement system.
+6. **Project Proponent assigns a VVB** to verify the monitoring report.
+   The VVB submits a verification report.
+7. **Gold Standard approves the verification report**, triggering the mint.
+   VER tokens land in the Project Proponent's Hedera account, one per tCO2e.
+
+Every step is a verifiable credential signed by the relevant role and
+hash-anchored to a Hedera Consensus Service topic.
+
+## Policy guide
+
+The policy is published to the Hedera network. Import it via the GitHub
+`.policy` file in this folder (`MECD-v1.2.policy`) or via the corresponding
+Hedera topic.
+
+### Available roles
+
+- **Project Proponent** — project developer who deploys and operates the
+  cookstove project and receives credits (VER).
+- **VVB (Validation & Verification Body)** — independent third party that
+  audits the PDD and each monitoring report.
+- **Gold Standard (Standard Registry)** — trusted registry overseeing the
+  full project cycle and authorising the mint.
+
+### Quantification methods
+
+MECD v1.2 supports two quantification methods:
+
+- **Method 1 (WBT — Water Boiling Test)** — credits useful cooking energy.
+  Uses baseline stove efficiency × fuel emission factors to compute a
+  baseline EF on a useful-energy basis.
+- **Method 2 (CCT — Controlled Cooking Test)** — credits the specific
+  energy consumption ratio between baseline and project. The most common
+  choice for projects where the baseline household has measurable per-meal
+  energy use, including the ATEC GS11817 deployment.
+
+(Method 3 (KPT — Kitchen Performance Test) is a v2.0 addition; not in
+v1.2.)
+
+### Important documents and schemas
+
+The policy uses a familiar GS project lifecycle with five primary documents:
+
+1. **Project Proponent / VVB Account Registration** — onboarding forms
+   for the two non-registry roles. Reviewed and approved by Gold Standard.
+2. **GS PDD (Project Design Document)** — the project's design — baseline
+   fuel mix, methodology choice (M1/M2), target population, additionality
+   argument, SDG contributions, ex-ante emission estimates.
+3. **GS Validation Report** — VVB's sign-off on the PDD, with assessment
+   team, evidence reviewed, finding log, and audit milestone records.
+4. **Monitoring Report (Auto) GS** — aggregated metered data for one
+   monitoring period, plus the computed BE / AE / LE / ER chain.
+5. **Emission Reduction Document GS** — the calculator's output: per-fuel
+   baseline rows, project emissions per branch (electric / fossil /
+   renewable), leakage, and the final ER number.
+6. **GS Verification Report** — VVB's sign-off on the monitoring report;
+   triggers the mint when approved by Gold Standard.
+
+### Token (carbon credit)
+
+**Verified Emission Reduction (VER)** — fungible Hedera token, one per
+tonne of CO2e avoided.
+
+### Step by step
+
+Screenshots are included only for the methodology-specific moments. Account
+creation, role approvals, and "assign VVB" steps work the same way as in
+every other Guardian policy.
+
+#### Registry (Gold Standard) flow
+
+The Standard Registry publishes the policy, holds the Hedera topic key, and
+sits at every approval gate in the workflow.
+
+1. Log in as the registry user and import the policy file from this folder.
+
+2. Approve incoming Project Proponent and VVB account applications.
+
+3. Review submitted PDDs and approve project listings.
+
+4. Review and approve VVB validation reports.
+
+5. Review and approve monitoring reports submitted by proponents.
+
+6. Review and approve verification reports — this triggers the mint.
+
+   [SCREENSHOT_PLACEHOLDER: verification report approval + mint]
+
+7. Inspect the trust chain for any minted credit. Every step is signed and
+   anchored to a Hedera Consensus Service topic, so any reviewer can trace a
+   credit back through the project documents that produced it.
+
+   [SCREENSHOT_PLACEHOLDER: trust chain view]
+
+#### Project Proponent flow
+
+1. Register an account (Project Proponent Account Registration form). Wait
+   for Gold Standard to approve.
+
+2. Submit a Project Design Document (PDD). This is the heaviest form — it
+   covers project details, baseline fuel mix and EFs, methodology choice
+   (M1 or M2), target population, additionality, and the ex-ante credit
+   estimate.
+
+   [SCREENSHOT_PLACEHOLDER: PDD submission form]
+
+3. After Gold Standard lists the PDD, assign a VVB to validate it. Once the
+   VVB submits a validation report and Gold Standard approves it, the
+   project is live for monitoring.
+
+4. For each monitoring period, submit a monitoring report. The form
+   captures the period's metered data; the policy's `pp_er_calcs` block
+   computes baseline / project / leakage emissions and the resulting ER.
+
+   [SCREENSHOT_PLACEHOLDER: monitoring report submission]
+
+5. Assign a VVB to verify the monitoring report.
+
+6. Once Gold Standard approves the verification report, the VER tokens are
+   minted directly into the proponent's Hedera account.
+
+#### VVB flow
+
+VVB is the external independent third party that audits the project at two
+gates: validation (the PDD) and verification (each monitoring report). The
+VVB can sign off, request changes, or reject.
+
+1. After registering and being approved, the VVB sees PDDs assigned to them
+   for validation. Reviews the baseline assumptions, methodology choice,
+   eligibility, and additionality argument.
+
+2. Submit a validation report. Once Gold Standard approves it, the project
+   moves into the monitoring phase.
+
+3. For each monitoring period the VVB is assigned to, review the monitoring
+   report — spot-check the metered data, confirm the calc inputs, and
+   submit a verification report.
+
+   [SCREENSHOT_PLACEHOLDER: VVB verification review]
+
+## Direct device measurement (vs. sample-based)
+
+The "metered" in MECD is the methodological hook that makes the policy
+work end-to-end on the ledger. Each project device carries a meter (or
+fuel-sale records, in non-electric variants) and the data flows into the
+monitoring report directly, without sample extrapolation. Most cookstove
+methodologies historically required sample surveys of a few percent of
+households and projected the rest, which is the principal source of
+overcrediting in the sector.
+
+The v2.0 revision tightens this further with a Continuously Tracked
+Energy Consumption (CTEC) integrity check (≥95% of devices reporting per
+period) and a meter-error adjustment. v1.2 doesn't enforce these but the
+direct-measurement design is the same.
+
+## Where this fits in the methodology lifecycle
+
+MECD v1.2 is the version this policy implements. It was used for the first
+fully digital MECD issuance (ATEC × Earthood, GS11815 / GS11817, Bangladesh,
+2024) and remains supported for projects mid-crediting-period.
+
+For new deployments, Gold Standard published a Paris-Agreement-aligned
+revision in 2025 that supersedes v1.2:
+
+- Adds **Method 3 (KPT)** as a third quantification path.
+- Makes **upstream emission factors (UEF)** mandatory on every fuel.
+- Adds a **conservativeness stack**: 90/10 uncertainty rule, per-capita
+  consumption cap, downward adjustment factor, NDC-aligned BAU ceiling,
+  meter-error adjustment.
+- Adds **embodied leakage** for stove manufacturing in the deployment year.
+
+The v2.0 implementation lives in [`MECD v2.0/`](MECD%20v2.0/) alongside
+realistic ATEC-derived test fixtures, sanitised API curls, a migration
+guide, and full per-role workflow documentation.
+
+If you're starting a new project, use [v2.0](MECD%20v2.0/). If you're
+mid-crediting-period on v1.2, stay on v1.2 until renewal — see the
+[migration guide](MECD%20v2.0/migration-from-v1.2.md).