I don't use Yesterday's News because, unfortunately, it's not imported in my country. I've heard it's one of the best and safest litters in the market. If your bun eats a couple of pieces, I don't think it'd be a problem, since this litter is made of recycled compressed paper. However, if he really eats it in quantities, he could develop GI stasis, as if he ate pieces of shredded paper. So you should watch him. If you put hay on top of the litter, I guess I could solve your problem, since hay is safe and healthy for your bun.
Marietta