Okay - two tries:

1) Maalox or Tums, which are supposed to help stomach problems may lessen quantity

2) Try the allergy diet - start with the blandest four foods you know for 4 days to clean out the system. (chicken, celery, rice, a fruit) Then add 1 food a day. When/if farting increases or changes intensity, eliminate that food. Works for defining asthma problems too. Course it's BORING eating for a while. I had a friend who found apples and onions to be the culprits.

Or shortcut it with some research and try the most likely ones first. I bet on onions or sharp cheese. E.