Many dairy farmers in California are adopting a new technology that allows them to produce their own electricity from methane gas captured from animal waste. (One cow can produce up to 2 kilowatts a day.) This practice reduces the amount of methane gas released into the atmosphere. In addition to reducing their own utility bills, the farmers are allowed to sell any electricity they produce at favorable rates.

a. Explain how the ability to earn money from capturing and transforming methane gas behaves like a Pigouvian tax on methane gas pollution and can lead dairy farmers to emit the efficient amount of methane gas pollution.

b. Suppose some dairy farmers have lower costs of transforming methane into electricity than others. Explain how this system of capturing and selling methane gas leads to an efficient allocation of emissions reduction among farmers.