Third party in renewable energy

I am reading the below paragraph from the reference guide and i don't quite understand it , as it is really confused with the Green power credit? how come using offiste renewable energy be considered for renewable energy credit ? Some renewable energy systems that use fuels produced off site (e.g., landfill gas) can still be eligible to receive points under this credit. In such a case, the project team must provide documentation showing the following: ·· The project has a minimum 10-year contract with the fuel provider. ·· The contract with the fuel provider includes both the fuel and all associated RECs. ·· If the fuel provider does not also provide RECs, the project must purchase offsets for 100% of the renewable energy produced in the form of RECs every year for at least 10 years. In some cases, renewable energy may be available from equipment, such as a PV array or wind turbine, owned by a third party, whether on or off site. Project teams wishing to receive credit for such an arrangement must submit documentation, including the agreement between the project owner and the power producer. The power purchase agreement must last for at least 10 years, and the project owner must retain all environmental benefits from the renewable energy.