They said the administration could add gallons lost from the waivers to the proposed 2020 Renewable Volume Obligations (RVO). 

Additionally, they said, the administration could initiate another Biofuels Infrastructure Partnership program through USDA "so states and private partners can match more federal funds and improve consumer access to renewable fuels."

"Every waiver EPA approved affects our states. The recent approval of 31 additional small refinery waivers undermines the integrity of the RFS and harms our states agricultural communities, which have already been affected by the Administration's tariffs. Since 2016, your Administration has issued 85 exemptions, representing a loss of over 4.3 billion gallons of ethanol," they said. 

The letter was issued through the Governors' Biofuels Coalition. Walz is the current chair of the coalition while Noem is the vice chair. 

Both governors said other steps the administration could take to expand the market for ethanol include increasing the minimum octane standard in gasoline while enforcing the Clean Air Act requirement to replace aromatics toxics in gasoline. 

"Farmers, environmentalists, and consumers would all benefit from these actions," they said. 

Read the full letter here