When I go grocery shopping, I grab a few empty cardboard trays--the ones that used to be the bottoms of the boxes the food was shipped in--off of the shelves. Three or four of those a week will keep me in cardboard. If I run low, I dumpster dive for cardboard. I live in an apartment. It seems that apartment dwellers are always tossing out cardboard boxes.

One thing nice about the cardboard trays is that they tend to be thin cardboard that I can easily run through a paper shredder.

Cardboard can refer to either what I would call shirt box cardboard like cereal comes in or corrigated cardboard. Soon your eyes will see cardboard everywhere free for the taking. There is also wrapping paper tubes, paper towel tubes and tp tubes. Non styrofoam egg cartons. Coffee trays. Whole Foods take out salad boxes. Cereal and pizza boxes take a while to break down due to the printing or even white "painting" of the pizza box.

Some vermicomposters shred which has its advantages.

I usually do not. More work for the worms.

The pizza boxes I was using aren't painted white but they do have printing on the outside. I was mainly tearing off the side folding pieces and then putting the larger tops on top of my paper so they would soften up for easier tearing. So, I can use the drink carriers you get from a fast food place ? Are all TP rolls and paper towel rolls ok? I guess I'm worried that something would be treated and I would accidently kill all my worms. :)

Most cardboard and chipboard is OK. Don't use cardboard that has a slick surface, like cereal boxes. Printed or colored cardboard with a matte surface is OK.

Some cardboard that is used to ship products from overseas in shipping containers will be treated with a fungicide. You want to avoid any cardboard that may have been treated this way.

When in doubt, don't use it. Cardboard is ubiquitous. You can always find more somewhere else.

One thing I don't care for with cardboard boxes is the glue that is used to hold them together. The glue between the layers in corrugated cardboard is great worm food. The glue used to glue the cardboard to itself to hold the box shape is often plastic hot melt glue. It took me a while to figure out why I had bits of plastic in my finished VC. It is glue from cardboard boxes.