# Use Cases and Reference Implementations

**Building a registry for clean commodity certificates**: Today many commodities—from electricity to liquid fuels, steel or aluminum, or even digital assets—are adopting technologies to reduce their carbon footprint. Commodities that are produced in a sustainable manner can be differentiated from conventionally produced alternatives if they can be digitally tracked throughout their lifecycles.

Green Proofs has been implemented in several of these use cases already:

* [24\*7 Renewable Electricity](https://docs-launchpad.energyweb.org/energy-solutions/green-proofs-by-energy-web/use-cases-and-reference-implementations/24x7-renewable-electricity)
* [Sustainable aviation fuel](https://docs-launchpad.energyweb.org/energy-solutions/green-proofs-by-energy-web/use-cases-and-reference-implementations/sustainable-aviation-fuel)
* [Green Proofs for Bitcoin](https://docs-launchpad.energyweb.org/energy-solutions/green-proofs-by-energy-web/use-cases-and-reference-implementations/green-proofs-for-bitcoin)
* [Sustainable maritime shipping fuels](https://docs-launchpad.energyweb.org/energy-solutions/green-proofs-by-energy-web/use-cases-and-reference-implementations/decarbonizing-shipping)