Can a bioreactor landfill become too wet?

A bioreactor landfill is designed to have liquid added to the system in order to increase the moisture content of the waste and then re-circulate the leachate through the system, because of that it really shouldn’t be possible to make it too wet. Most landfill waste has a field capacity of about 55% moisture content, meaning that’s the amount of liquid it can hold before the liquid will just fall through the waste to the under-drain leachate collection system to be pumped out. In the United States, landfills typically have waste with a moisture content of between 10-25%, so we generally need to add liquid to a landfill in order to make it into a bioreactor, and in some cases, a significant amount of added liquid.  Exceptions to this would be countries where there is significant rainfall and there are no under-drain collection systems that we commonly have under U.S. Reg. Sub-Title D designs. For example, at sites in Southeast Asia and South America the moisture content of the waste material coming in can be around 50% because they have a much higher organic waste content and much less fluff material, such as packaging, plastics and so on. To that you add 100 inches of rainfall a year or more and you get some serious problems. In those situations, it is possible for the landfill to become far too wet and then you end up with slope stability issues and other problems, so dewatering applications are generally warranted, not just to keep the gas flowing but also just to keep the landfill itself stabilized. There have been a couple of examples in the last three years of major slide slope failures at a couple of large landfill sites in Brazil where hundreds of thousands of tons of waste material and soil have slid off the landfill and now they have major remediation projects because of that.