You likely think of a dumpster as a trash container that you can pack practically any material in for handy and affordable disposal. However, there are many restrictions on the waste going into a dumpster, and many of them are not obvious because the restricted materials aren't hazardous or unusual. Understanding why some dumpster rental companies don't accept dirt or landscaping debris will help you find one that does accept these materials.
First, dirt, in particular, is far heavier than most of the waste that goes into a dumpster. You might wonder how dirt could weigh more than scrap metal or roofing shingles, but consider how most items that go into a dumpster don't fit together tightly and have a lot of loose air space between individual pieces of trash. Dirt fits tightly together with none of the gaps, resulting in a greater total amount of material fitting into the dumpster. Soil and dirt are also surprisingly heavy, with damp or wet soil weighing up to 3,000 pounds per cubic yard. Considering many dumpsters hold a dozen cubic feet or more, the pounds add up quickly.
Dirt and yard waste are generally directed to different trash facilities and landfills than other types of waste because they are biodegradable. Mixing large loads of biodegradable material into general landfills can create pockets that collapse after breaking down, destabilizing the organization of the waste and causing dangerous avalanches of metal and other dangerous materials. The dumpster company may not have an arrangement with the right inert waste facility to get rid of your yard waste.
When you're cutting down entire trees to clear land for a new home or to protect your current structure, it's much less work to be able to toss entire sections of logs and branches into the dumpster for prompt removal. However, many dumpster rental companies chip yard waste in order to sell it or give it away, so the equipment they use for chipping limits the size of material they can accept. For example, some companies accepting yard waste still limit the material to logs with a 4-inch diameter or less.
Finally, you definitely can't mix yard waste, dirt, and other types of trash in the same dumpster. It's very difficult to sort metal scraps and bits of plastic out of a pile of dirt, and the dumpster company can easily supply you with two separate dumpsters for yard waste and other materials. If you're renting two smaller dumpsters so you can separate the waste, you likely won't spend much more than you would on a larger unit.