Compost is biodegradable.
There is little danger of hazardous waste entering groundwater if the waste is disposed of through deep well injection.
Leachate results from water “leaching” in landfills. It is therefore contaminated with whatever was in the waste in the landfill that the water leached from. Basically, the leachate is the result of contact between the water and a hazardous waste, so therefore the leachate itself is a hazardous waste. Leachate needs to be collected and removed. Here is a neat site with an animated graphic demonstrating the process of a landfill.
I would most definitely agree. Leachate is water, or any other solvent, that has percolated down therough various materials, such as those found in a landfill. This water dissolves or carries particles with it as it percolates through all the various materials contained within the landfill. The water is termed "leachate" if it flows out of the landfill. If you have ever seen the back of a city sanitation truck when it is raining, and smelled the liquids that are pouring out of the truck when they compact the load, you have had first-hand experience with leachate. There is no accurate way to control this waste water, and it will enter the groundwater at some point, carrying all the materials it has leached out of the solid waste. The only way to eliminate leachate would be the elimination of landfills, but then you have another problem: what to do with all the trash we produce on a daily basis? We solve on problem, but then create another.