There are a few reasons why your bin may run even when you didn’t add new kitchen scraps.
Your bin was just unboxed and paired
That is expected behavior - the bin always runs a cycle the first day it's been unpacked. After that, it runs only when an estimated 0.22 lbs (for 1st gen) or 0.44 lbs (for 2nd gen) of food scraps have been added. If no scraps are added, the bin will still run once every 4 days to prevent moisture build-up and mold.
Your bin may be making up for lost time
If your bin’s lid wasn’t fully closed the night before, it may have skipped a Dry & Grind cycle. The next time you open & close the lid, and it engages correctly, your bin will automatically go into a Dry & Grind cycle to make up for lost time the night before.
Your bin mistakenly thinks you added some scraps
If you set something on top of the device, the bin’s weight sensors may think you added scraps. The weight system can also get out of sorts if the bin gets bumped, or if the pedal or lid are messed with. Learn more about how to reset your bin’s scale here.
Your bin lost power or your bucket was removed and replaced
If your bin loses power or your bucket was removed and replaced, it may run to make sure anything that was added in that time gets a Dry & Grind cycle.