Sustainability-First Distributed Ledger Systems: Six Reference Designs and a Shared SFC Engineering Profile

Six original distributed-ledger system designs addressing ecological challenges across supply-chain certification, healthcare and pharmacy interchange, paperless billing, recycling and material recovery, cross-operator roaming for telecom and EV charging, and carbon-credit measurement, reporting and verification. All six share a single Sustainability-First Consensus (SFC) engineering profile, the SFC ledger profile, that turns sustainability criteria into engineering properties a reader can check rather than claims: an annual network energy budget on a stated boundary, hardware-lifecycle constraints excluding single-use hardware, signed on-ledger EnergyAttested and CarbonAttested events with an offset-coverage rule (the framework's "Net Zero"), disclosure through the sustainability-data well-known URI with an evidence-to-disclosure bridge, and a qualification rule separating hot-path ledgers from anchor-only layers. Each project is documented as four companion files: README (motivation, architecture, data flow, sustainability and policy alignment), PRD (problem, personas, requirements, KPIs, milestones), SPEC (identifiers, schemas, event envelope, REST API, smart contracts, conformance tests) and ARCH (components, sequences, trust boundaries, deployment, failure modes), with architecture and data-flow diagrams. Changes in 1.2. The SFC ledger profile is version 1.2 and is used together with the SFC disclosure profile 1.1 (rfc-sustainability-wellknown repository, sfc-compliance/PROFILE.md). The four bespoke disclosure endpoints of 1.1 are retired: figures are published as a signed declaration at /.well-known/sustainability-data (draft-besleaga-sustainability-wellknown-07, an Internet-Draft, work in progress), and the profile maps each retired endpoint to its replacement. A ledger-evidence extension carries, inside the signed declaration, the head hashes of each operator's attestation chains, the event counts, the totals and the result of the offset-coverage rule, so that a reader with ledger access can check the declaration against the signed ledger record. Version 1.2 also adds rules for corrections, signing keys and timestamps; the C1 energy boundary of Delegated Regulation (EU) 2025/422, field S.8; whole-tonne retirements allocated to periods; Scope 2 reported location-based and market-based; a chain-agnostic anchor; no optional privacy noise in a declaration that carries the bridge; and a statement of what a conformance claim may and may not say. Passages of 1.1 that presented network energy as known are corrected to design targets, outside figures are re-sourced, and CSRD scope statements follow Directive (EU) 2026/470. Event names and fields of 1.1 are unchanged. The work remains at design level only. All work is documented at design level. No system described here is implemented or deployed, and no figure in these documents is a measurement of a running system; values are design targets or are cited from published external sources. This deposit records the engineering profile and the six architectures that apply it. The underlying four-criterion framework is defined separately in Besleaga, "Sustainability-First Consensus" Ledgers for a Green Digital Future, Communications of the ACM, Association for Computing Machinery, doi:10.1145/3809296 (accepted; in press). Deployments building on these designs should cite both.