The exemption is needed in both cases. Yes, there are probably more options for heating buildings than for drying grain, since drying requires a lot of energy in a short period of time. That said, the exemption is needed in both cases.
Why should an exemption be sought? On one side of the table, the government is saying that it doesn't trust producers and the industry and that it's going to tax them to force them to make changes. I'd like to point out that farmers have made a lot of changes voluntarily in recent years. They don't need to hear a member sitting at this table say that they'll be taxed to ensure they make changes. They're doing it on their own.