can i burn 2x4s scraps in my wood burning stove?

I don't see why not, as long as they aren't pressure treated or have some kind of nasty chemical in them. I burn scrap lumber in my friend's fire pit, and they actually burn pretty nicely. Just make sure that the scraps are clean and that there's nothing that you don't want to burn stuck in them.

Have heard that kiln dried wood burns hotter, will contribute no creosote, but runs higher risk of starting a chimney fire if you have creosote build up.