Its nothing to do with environmentally-hazardous waste and everyting to do with trade waste. You can take trade waste to the local site but you have to pay for its disposal - so you certainly don't want to be doing your customers favours by taking away stuff they can dispose of for free themselves. Whether you can away with your trade waste as domestic waste probably depends on the size of the van you take up there and how often you do it. My local tip seems to be well-frequented with folks who are evidently running businesses and getting rid of stuff.