OffsetZap

Demo

About

The problem it solves Despite growing demand for climate-conscious solutions in Web3, most decentralized applications (dApps), protocols, and users lack a seamless way to retire high-quality carbon credits on-chain. The carbon credit ecosystem is fragmented across chains, with verified credits from Toucan and KlimaDAO residing on Polygon, while emerging dApps and ecosystems, like those on Base, have limited or no native access to offset markets. This creates a major usability gap: builders on Base want to integrate climate responsibility into their platforms, but are blocked by technical limitations, multi-step bridging processes, and a lack of composability across carbon protocols. Current offsetting workflows require manual bridging, asset conversions, complex protocol interactions, and repeated gas payments—turning a good-intentioned action into a developer headache and user drop-off point. Enter the Evrlink-powered climate engine. Evrlink has opted in to a 1% climate action fee on every transaction across its platform. With Coinbase subdomain support, this climate fee is automatically routed to a CarbonSustain smart wallet, where emissions are offset in real-time using a dynamically blended portfolio of high-quality carbon credits sourced from Toucan and KlimaDAO on Polygon. This blend reflects live market pricing, credit quality, and availability—making offsets both scalable and programmatically optimized. Through this bridge-to-retire system, any dApp or user on Base can now offset their emissions—even though no carbon credit protocols natively exist on Base yet. With one click, users can bridge from Base to Polygon, automatically retire carbon credits, and receive verifiable on-chain proof—all without needing to leave the Base ecosystem or understand complex carbon protocols. For climate-focused protocols, DAOs, and hackathon teams, this enables a frictionless path to embed climate action into their workflows—finally aligning ESG goals with Web3-native execution.

How it's made

Challenges we ran into One of the core challenges we faced was bridging tokens from Base to Polygon in a seamless and gas-efficient way. We initially explored using LayerZero for cross-chain messaging, but ran into limitations with support between Base and Polygon—particularly when trying to execute retirement logic after the bridge transaction. LayerZero’s architecture added complexity around relayers and message delivery guarantees, making it less ideal for a user-friendly flow. We also wanted to allow users to convert their bridged tokens directly into high-quality carbon credits like NCT (Nature Carbon Tonne) or BCT (Base Carbon Tonne) using Uniswap. However, we had to dynamically estimate slippage and ensure that the swap wouldn't fail mid-flow, which added a layer of complexity to the on-chain logic. Another major hurdle was broadcasting the proof of retirement in a way that could be captured both on-chain and off-chain. After retirement, we wanted to notify stakeholders or apps about the transaction. However, most carbon protocols don't emit rich metadata, and there's no standard messaging system to push out those notifications. To solve this, we integrated XMTP (Extensible Message Transport Protocol). XMTP allowed us to send a real-time message confirming the retirement—including token metadata and retirement hash—to subscribed apps like Telegram bots or front-end UIs. We used XMTP’s wallet-based messaging to transfer both the retirement confirmation and token state, effectively creating a “proof-of-action” layer that complements the on-chain logic. In the end, we overcame these hurdles by combining smart contract bridges, dynamic swap logic, and decentralized messaging protocols into a streamlined UX. The result is a one-click solution for any Base user to offset carbon credits on Polygon—while ensuring the entire journey is both verifiable and transparent.