"Is it safe to throw debit card receipts in the trash?" yes and no, actually it is just the principle to have notes with private information close at hand (any information is expensive and reserved). If DCRs are very detailed and full of information (which is not usually the case) and your trash can is on the roadside, then you can see this as a potential risk. In fact, this is not so important if you work in a well-organized company. Of course somebody would be interested in that, but probably would not do anything with it.
Would it be worth more to burn / shred documents before throwing them away? Now you are risk free.