Recently, I attempted to measure the sheer volume of poop my bison produce in a day. Using a shovel I picked up all of the mostly fresh bison poop I could find in an area they had been occupying over the past 24 hours. Surprisingly, I was able to fill two 5 gallon buckets to the brim with poop. That's a lot of poop.
One last thing I'll have to comment on is the manure's unique lack of odor. If you've been around farms with cattle, you'll be very aware of the distinct and powerful odor associated with cow manure. With that in mind I had expected the two buckets of fresh poop to reek, but, two my surprise, they didn't. In fact the buckets of poop smelled so little that I was able to transport them in the back of a hatchback vehicle (with a lid on each bucket) for several hours to my garden in northern Virginia without the slightest bit of unpleasantness. I don't know if this is something unique to my bison or related to diet (they eat only grass), so I can't consider this an actual bison trait, but, from a gardener's perspective, it definitely deserves some research.