I hope you don’t mind discontinuing that tangent on environmentalism. It would not have led anywhere anyways. As for the ECP, economic calculation in “anarcho”-communist societies has been discussed around here plenty, you can find discussions via the search function. The short story here: It would be central planning with miniature states, but economically it would be state-capitalism. Small-scale communes can not benefit from regional division of labor and thus it would mean local self-sufficiency and subsistence poverty. The democratic system would be artificial and could easily break down in the face of economic troubles. And anarcho-communism is a contradiction, if you don’t have markets you either have state planning or starvation.