Optimism (OP) sustainability report

Optimism is present on the following networks: Optimism.

OP Mainnet operates no validator set and no consensus algorithm of its own. It is an optimistic rollup: blocks are produced away from Ethereum, but the canonical history and final settlement live on Ethereum. A sequencer accepts transactions, orders them and produces Layer 2 blocks on a two-second cadence, which is what gives users a fast confirmation. The ordered transaction data is compressed and published to Ethereum in batches, and every node derives the canonical chain by reading that data back from the settlement layer. Deriving the chain from Ethereum rather than from the sequencer's word is what makes the arrangement verifiable: anyone holding the published data can recompute the same state independently.

Correctness is enforced after the fact. Claims about the chain's output state are posted to a dispute-game contract on Ethereum, and since the fault-proof system was opened to the public in mid-2024 anyone may post such a claim or dispute one, with no allowlist involved. A challenge proceeds as a bisection game in which the two sides repeatedly narrow their disagreement until a single step of execution remains; that step is then executed inside a deterministic fault-proof machine on Ethereum, which settles the matter on-chain. Both sides lock bonds and the loser forfeits. A claim that survives a challenge window of roughly a week is treated as final for the purpose of withdrawing assets to Ethereum.

Two limits belong in any accurate description. Sequencing rests with a single operator, so ordering is centralized in practice; censorship is constrained rather than prevented, because a transaction can be deposited through a contract on Ethereum and must then be included in the chain. And a guardian role, alongside a security council, retains emergency powers, including pausing withdrawals and returning the dispute system to a permissioned mode should it fail — a deliberate safeguard that nonetheless keeps the chain short of full trust-minimization. Ultimate security comes from Ethereum's proof-of-stake consensus, whose validators finalize the data the rollup depends on.

Optimism is present on the following networks: Optimism.

Transactions are paid for in the settlement layer's native asset, and the amount splits in two. The execution component prices computation and state access on Layer 2 through a base fee that adjusts with demand plus an optional priority fee, and it is small because the work happens away from Ethereum. The data component covers publishing the transaction's data to Ethereum so the chain can be reconstructed, and it usually dominates. Since Ethereum introduced a dedicated data space for rollups, batches are posted there instead of as ordinary call data, and the pricing function reads both Ethereum's ordinary base fee and the separate fee for that data space — each relayed onto Layer 2 by a system contract every block — scaled by two parameters the chain operator can tune. What a transaction pays is proportional to its compressed size, estimated with a compression function, so the cost of a posting is apportioned across the transactions in the batch rather than charged to whichever one happens to trigger it.

There is no staking, delegation or reward issuance at this layer, and consequently no slashing. The sequencer's incentive is the margin between the fees it collects and what it spends publishing data to Ethereum, which gives it a direct reason to batch efficiently. Net of those costs, the surplus from this chain is directed to the collective treasury that funds protocol development and public-goods programs, and other chains built on the same software contribute a defined share of their own revenue on the same basis. Participants in the proof system are paid differently: bonds locked in a dispute are forfeited by the losing side to the winner, so challenging an incorrect claim is rewarded while posting one is expensive.

Deploying and calling smart contracts is charged on the resources consumed, on the same basis as on Ethereum, and there is no recurring storage rent — state is paid for when it is written. Underneath, the data the chain posts is subject to Ethereum's own rules, where the base fee is burned and the priority fee goes to the block proposer.

Optimism is present on the following networks: Optimism.

Two distinct things are being estimated, and conflating them is the usual source of error. The first is the electricity drawn by the chain's own infrastructure: the sequencer, the process that publishes batches, the challenger software that watches state claims and would contest an invalid one, and the population of nodes that other participants run, each of which pairs a consensus client deriving the chain from Ethereum with an execution client replaying it. The second is the portion of Ethereum's own consumption that belongs to the rollup, since every batch it posts occupies capacity that the settlement layer's validators pay to provide. That portion is apportioned by how much of Ethereum's resources the chain's postings take up. Ethereum publishes its own description of how its consumption is estimated (Ethereum energy consumption).

Nothing in this design is mined, so the chain's own side is estimated at the level of individual machines rather than through the economics of hardware competition. The node population is approximated from crawlers, peer discovery and publicly advertised endpoints. A representative machine specification is inferred from what the client software states it requires to keep pace with the chain, and the power that specification draws is taken from controlled measurement of comparable hardware, recorded both under load and at rest. The network total is the aggregate across the estimated population, including idle draw, since these machines run continuously. From that total, a fraction is assigned to an individual asset according to observed on-chain activity involving it.

The honest caveats belong with the number. The node count is a floor rather than a census, because machines behind private networks are not visible to a crawler. The hardware profile comes from stated requirements, not from a survey of what operators actually bought. And where evidence is thin, the assumption taken is the one that produces the larger figure rather than the smaller one. Estimates are revised as observation of the network improves.

Optimism is present on the following networks: Optimism.

Establishing a renewable share begins with location rather than with energy. The infrastructure in question is the sequencing and batch-publishing servers, the challenger nodes that watch the dispute system, and the wider set of full and archive nodes run by applications, bridges and infrastructure providers. Where those machines sit is inferred from publicly observable network information — announced peer addresses resolved against hosting and autonomous-system registries, and public listings of node operators — which supports a country-level picture rather than a precise location for any one machine. Because much of this runs on rented cloud capacity, the region a provider states for a facility is used in place of a finer-grained address. Where the chain's own sample is too thin to support a distribution, the pattern observed on networks built along similar lines, with comparable participant roles and hardware classes, substitutes for the missing portion.

The settlement layer is handled separately and then combined. The share of Ethereum's consumption attributed to the rollup takes on the geographic profile of Ethereum's validator population, which is distributed differently from the rollup's own servers, so the two distributions are weighted by their respective contributions to estimated consumption before being merged.

Those country weights are applied to published figures for the renewable proportion of each country's electricity generation, taken from Share of electricity generated by renewables, compiled by Our World in Data from Ember and the Energy Institute's Statistical Review of World Energy. What comes out is a consumption-weighted average across the inferred footprint, reflecting the grids the infrastructure most likely draws on. It does not capture procurement: renewable supply contracts, certificates and behind-the-meter generation cannot be seen in network data and are not credited.

Energy intensity here means a marginal quantity — the extra electricity associated with one further transaction, given the infrastructure already running. Node and sequencer power draw barely varies with how full a block is, so this marginal figure is small and falls as throughput rises. It is not the network total divided by the transaction count, and the two should not be compared.

Optimism is present on the following networks: Optimism.

The emissions figures are computed from the energy estimate, not observed directly. The geographic breakdown assembled for the renewable share — sequencing and batch-publishing servers, challenger and full nodes, and the slice of Ethereum's validator population attributed to settlement — is carried over, and each country's portion of estimated electricity is multiplied by that country's average grid carbon intensity. The intensity figures come from Carbon intensity of electricity generation, compiled by Our World in Data from Ember and the Energy Institute's Statistical Review of World Energy and released under a Creative Commons BY 4.0 license. Country results are summed into a network total, from which a share is attributed to an individual asset in line with observed on-chain activity.

Scope 1 and scope 2 describe different things and are reported separately. Scope 1 is direct combustion under the operators' own control — fuel burned on site, standby generation. For infrastructure hosted in commercial data centers there is normally nothing material to report here, and it is stated as zero or negligible rather than estimated upward. Scope 2 carries the weight: it is the indirect emissions embodied in purchased electricity. The calculation is location-based, applying the average intensity of the grid serving each region, because a market-based calculation would need supplier contracts and certificates that are not observable from outside. Embodied emissions from manufacturing servers or constructing the facilities they occupy are not in scope.

Greenhouse gas intensity is reported as the marginal emissions of one additional transaction, consistent with how energy intensity is treated. The main uncertainties should be read alongside the number. National annual averages smooth away the hourly swings and regional differences a real facility experiences. Every assumption in the underlying energy and location estimates propagates through to the emissions figure. And where a choice between plausible assumptions has to be made, the one producing the higher result is preferred, so these figures are better understood as a conservative ceiling than as a precise measurement.