🌱 RePlas – Decentralized Plastic Waste Management Platform

Inspiration

Growing up in Nigeria, our team saw children playing near piles of discarded bottles and families burning plastic to get rid of it. The toxic fumes and the visual blight were just one side of the problem. The deeper issue was a lack of ownership and accountability. No system rewarded people for disposing of plastic responsibly, and no universal standard existed for tracking waste. This lived experience inspired us to ask a simple question. What if a plastic bottle could tell its own story, be tracked, valued, and rewarded instead of poisoning our communities and oceans?

What it does

RePlas transforms plastic waste into value by combining AI image recognition and blockchain-based incentives. Users take a photo of plastic waste, and the AI classifies it instantly. Verified submissions are recorded on the Celo blockchain, creating transparent and traceable data. Every action earns RePlas tokens, which can be redeemed in an eco marketplace or used in community challenges. Leaderboards and gamified 3D visualizations drive participation. The result is a mobile-first ecosystem that empowers consumers, producers, and recyclers while delivering measurable environmental impact.

How we built it

Frontend built with Next.js 14, TypeScript, Tailwind, and shadcn for sleek mobile-responsive UI, with Three.js and Framer Motion for 3D visualizations and animations.
Backend powered by Node.js, Express, and MongoDB with role-based access and JWT authentication.
Blockchain layer on the Celo network using Solidity smart contracts, ERC20 tokens for rewards, and ERC721 NFTs for impact certificates.
AI layer using Google Gemini computer vision to identify plastic types, and conversational AI for educational nudges.
Deployment via Vercel, Railway, and MongoDB Atlas, with AWS S3 for file storage and IPFS for decentralized assets.

Challenges we ran into

Training AI to classify diverse plastic waste in poor lighting or low-resolution images.
Designing incentive systems that were both fair and economically sustainable.
Making blockchain accessible in regions with low connectivity and high transaction costs.
Building an engaging user experience that encourages long-term participation, not just one-time use.

Accomplishments that we’re proud of

Built a working platform with live demo RePlas Demo and smart contracts deployed on Celo.
Successfully integrated AI-powered plastic classification with blockchain-verified submissions.
Designed a gamified ecosystem with tokens, leaderboards, and 3D visuals to motivate communities.
Launched an early marketplace where tokens can be redeemed for eco-friendly products.
Created a transparent plastic waste ledger that can be scaled across regions.

What we learned

Tech is not enough. The key is aligning community incentives with environmental goals.
AI works best when combined with human feedback and blockchain transparency.
Simplicity is crucial for adoption, especially in communities with low tech literacy.
Building for Africa first means prioritizing offline support, mobile accessibility, and low-cost transactions.