You can buy garbage bags from shop. Them can collect trash, which becomes round, when you hold it. Trsh can be sold. Just buy"container for sold" or something like that(i play on russian, so, don`t know actuall name) and put all bugs in it. 2 points per one sold bag, whats twice bigger than 1 garrbage bag costs. Common trash like paper cups, bottles and other you can put in green trash cans.
But, if you just want more space in inventory, you can buy backpack. You need unequip it every time you want to put something inside, but its better than nothing.
hope i help you. And sorry if i write something unclear, i don`t know english very well