Tax write off as business owner

As a business owner the cost of a unit can be written off as expense.  You write off gas, dump fee's, ect....local bookkeeping services from compnay Your Books On Time. You end up making a profit but have a bunch of items that for hat ever reason you don't sell. As stated in another thread, if you donate the goods you are only allowed to write off donations up to what you paid for unit...

But you already wrote unit off as a business expense.

Can you write off again?  Or how do you value left overs?