Current national output can be consider as deriving from a collection of capital goods, including a natural capital good. A model is created which considers Net National Product as interest on capital in the economy: a new approach which touches in a non-trivial way on green national accounting. One important implication is that trading nation draws in part on the capital, including natural capital, of its trading partners and exports in part some of its own capital in its exports. It is also necessary to incorporate pollution spillovers Net National Product which is a hugely vexing issue.