No, you do not need a garbage disposal to have a dishwasher. A dishwasher will work without one, and while it's rare to see a home with a dishwasher that doesn't have a disposal, it is possible. The two appliances pair well and are often installed together because a disposal simplifies meal cleanup.

However, your dishwasher should not be used as a replacement for a garbage disposal. Subjecting it to continuous food leftovers can lead to major clogs. If you choose not to install a garbage disposal, you should thoroughly rinse your plates or scrape excess food into the trash or a compost pile before loading them into the dishwasher to prevent plumbing issues.

Whether it's worth repairing your garbage disposal depends on its age and the specific problem. Generally, if the unit is eight years old or younger, repair is a good option. For minor issues like a bad seal or a simple jam, a repair can be inexpensive, sometimes under $10. However, if the motor is broken (a repair that can cost $150 or more) or the unit is getting old, it's often more cost-effective to replace the entire disposal.

Garbage disposals can be considered bad for the environment due to their electricity usage, but good for the environment because they reduce the food waste sent to landfills. If everyone used a garbage disposal, it would tax the wastewater treatment facilities in that region, but if we had to choose one of the options, we’d say they are a net positive on the environment when used correctly. 

Soil is just one of the items you shouldn't put down a garbage disposal. Garbage disposals are only meant for soft, non-fibrous foods. Large amounts of topsoil, dirt, or rocks will damage the blades of your garbage disposal or clog the pipes. If a small amount of dirt goes down the drain as you repot a plant, you shouldn't have to worry, but never dump a whole pot of soil in the sink for fast disposal.