This paper proposes a green consumption model under uncertainty, where we consider green goods as impure public goods and analyze the comparative statics of green consumption. We consider that the environmental efficacity of green goods is uncertain, and we model uncertainty with risk perceptions, specifically with trust (defined as a belief about the veracity of the available information) and pessimism/optimism (which represents the consumer's probability estimation of the realization of the worst possible outcome when consuming green goods). We study their respective impact on green consumption and consider individuals with heterogeneous beliefs. Pessimism has a negative impact on green demand; meanwhile, an increase in trust does not always imply an increase in green demand. We determine the impact of uncertainty on the equilibrium and the socially optimal level of private voluntary provision and show that green consumption decreases with pessimism at the equilibrium. Meanwhile, at the optimum, an increase in pessimism will decrease the individual's contributions for both the pessimist and optimist consumers. Moreover, we also find that the sub-optimality of the Nash equilibrium, in the presence of an impure public good, is not straightforward under uncertainty.