Hybrid Real-Time Incentive Engine Coupling EPR Compliance with Blockchain-Based Smart Contracts for Plastic Waste Reduction in Krui Hotels and Cafés

Background: Indonesia's hospitality sector, especially in the 3T region of Krui, generates large quantities of single-use plastic, with diversion rates below 15 % and severe pressure on municipal waste infrastructure. Objectives: To design, implement, and empirically evaluate a real-time incentive engine that links Extended Producer Responsibility (EPR) obligations to blockchain-based smart contracts, thereby achieving measurable plastic-waste reduction while providing enforceable legal accountability. Methods: A private Ethereum network records RFID-captured dispensing events via MQTT; Solidity contracts encode reward-penalty rules derived from Indonesian Civil Code Articles 1320 (consensus), 1338 (consideration), and 1243 (capacity). A mixed-integer linear program (MILP) minimises net cost (C_base - R_incentive·W_i) subject to diversion-rate thresholds, gas-fee caps, and force-majeure triggers defined by BMKG criteria. The pilot involved 120 hotels and cafés (3 600 guest-stays) over 12 months, generating 43 200 transaction records for sensitivity analysis on plastic price volatility and transaction-cost fluctuations. Results: The system achieved an average monthly waste-reduction of 12.4 % (p under 0.01), delivering IDR 1.2 billion in net savings; the break-even point was reached at Rp 13 200 /kg of plastic. End-to-end latency from sensor read to blockchain confirmation averaged 420 ms, and per-transaction gas cost remained at Rp 2 500. Sensitivity analysis showed that a 10 % increase in incentive rate raised reduction to 14.1 % while a 30 % gas-fee surge reduced net savings by only 4 %. Published in Journal of Coastal Frontiers and Applied Development (JCFAD). CERN Zenodo Record: https://doi.org/10.5281/zenodo.24116258. Publisher: PT CHAIN ASIA CONECT Research and Development Division.