Governments can increase the consumption of a product that creates positive externalities by

   Subsidising the production of the product so that the supply is increased and market price is reduced.

Explanation:  Government subsidies for production are nothing but incentives for production or a particular product. The government can always, by its measures, influence the parameters of the production and market, which is a characteristic of the so-called mixed economies, the mixture of market economy and the influence of the government. In this sense, subsidies are a certain amount of money that the government gives to production, depending on what parameters it wants to improve, in this case, increased supply and a decrease in the price of products on the market. These may be some other incentive measures, i.e. subsidies, and the ones I mentioned relate to this particular case.

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