According to the directions on the tater batting you can use serger to sew bag together. Since my serger thread is all polyester I took piece of tater batting and serged edges then put in microwave. IMMEDIATELY caught fire. What a nasty smell!
So, even though the directions don't say use cotton thread I know because all of you here on the board have emphasized it and will be making my bags with 100% cotton thread on my sewing machine instead of the serger.