I used to think that using a garbage disposal was actually good for the environment ... especially when only vegetable products were ground up. I had visions of nutrients going back to the earth or becoming fish food ... and that, in my mind, justified the many gallons of water going down the drain.
Well, that's not exactly how it all works. When food goes down the disposal, it is sent to a sewer treatment plant or a septic tank. At this point, any solids are allowed to settle to the bottom and are eventually gathered up and sent to a landfill. With a septic tank, the fluids run off to a drain field. In sewer treatment plants which only do "primary" treatments, about half of the solids, organic materials and bacteria are removed and the remaining fluid is chlorinated before being discharged (the chlorination does not get rid of phosphorous and nitrogen). And where is the treated "water" discharged? It is dumped into rivers and other waterways ... and eventually finds it's way to our oceans.
Remember the phosphorous and nitrogen? Well ... those plant nutrients are the primary cause of dead zones, which are areas in the ocean where oxygen is depleted. And that means no fish or plant life.
Some sewer treatment plants go on to complete second and third treatments of the water. In these stages, chemicals are used to remove the phosphorous and nitrogen and about 90% of the organic materials are removed. The water released after three stages of "cleaning" is much better but still ... we're talking chemicals and processing and increased loads for already burdened plants.
So is there a better way? Sure! Composting is the best way but if you can't compost, tossing those veggies peels in the garbage is better than sending them down the disposal. You'll not only save gallons of water, you'll be protecting our environment.