We have a cast iron rule in our house - no farting in the same room as the other person. If you want to fart you have to go elsewhere.
Also look at what he is eating at night. Maybe give him some peppermint tea an hour before bedtime and it should calm him down a bit.
Haha oh thanks for the advice there @trevor.george I will keep that peppermint tea idea in mind. We did have chinese food for dinner lastnight so maybe that was the cause? haha