Usody.com, eReuse.org and Ledgerproject.eu have implemented a blockchain deposit-refund. 2nd hand donors, manufactures, retailers and refurbishers ask for a deposit every time they sell or donate a new electronic appliance. In this example, a public administration set of conditions defined by donors, and foster final consumers to return or recycle properly reused devices. The deposit and conditions are a smart contract attached to the devices. Donors charge a deposit to refurbishers, and these to final customers. If the donors' conditions are met and the device is recycled at the end of its life, then the smart contracts will be triggered to pay back the deposit automatically to the agents participating in the reverse supply chain. This economic incentive allows to impact on the behavior of agents without having to know or disclose them, it is like a zero knowledge network.