I expect the underlying infrastructure to use about or less than 0,01% of the energy the Bitcoin network uses.

It should support micropayments, i.e. should have nearly non-existent payment fees in perhaps another mode. This implies no fixed portion in the payment fee.

The payment fees also in non-micropayments should be small (less than 1%) as well to make it competitive to credit cards.

A flat 0,5% for all payments would make it interesting from a financial standpoint. Probably quite challenging technically, but that's where the potential edge against current payment providers could be.