Coal, by contrast, is associated with a much smaller methane release during mining; but burning it produces about twice as much CO2 as burning naturalgas.
Coal contains less energy per unit of weight than weight than naturalgas or oil; it is difficult to transport, and it is associated with a host of environmental issues, among them acid rain.
煤的单位能量含量低于石油和天然气，而且会导致包括酸雨在内的一系列环境问题。
3
The project involves the exploration, development, production, marketing, and sales of naturalgas, oil and associated condensate from the contract areas.