Tony Davis reports in the Arizona Daily Star that the “Arizona Department of Environmental Quality wants to make this the 15th state nationally to secure Environmental Protection Agency permission to start issuing permits for what’s known as ‘bioreactor landfills.’” (See story here.) I think the next sentence in the story is a misstatement: “They use liquids to react with garbage and speed the decomposition of methane gas that radiates from landfills everywhere.” It is not the methane that decomposes, it is the organic material in the garbage that decomposes to produce methane, more quickly in the case of bioreactor landfills.
The whole idea behind bioreactor landfills is to speed up natural decomposition of the contained organic material by providing conditions that favor increased microbial action. This is accomplished by circulating water, or air, or both through the landfill.
To find out more about these landfills, I recommend http://www.bioreactor.org/ a site sponsored by the Florida Department of Environmental Protection and the U. S. Environmental Protection Agency. In Florida, these agencies are running two experimental bioreactor landfills as a bioreactor demonstration project. The site contains a detailed report of results and a video.
Claimed advantages of bioreactor landfills over conventional landfills:
1. Reduced potential for pollution. This presumably comes from recirculating water (called “leachate”) within the landfill to collect toxic metals and other harmful substances rather than have such substances gradually get into the ground beneath the landfill.
2. Increased energy recovery and reduced greenhouse gas emissions. The enhanced microbial action produces methane faster so that it is easier to collect.
3. Extended life for landfill. Decomposition of organic matter decreases the mass and allows the landfill to be used longer.
4. Lower long-term maintenance costs.
Claimed disadvantages of bioreactor landfills:
1. They use more water and the increased moisture could make the landfill less stable.
2. Initial costs are higher because of installation of water/air circulating system and monitoring system.
3. Bioreactor landfills tend to produce more hydrogen sulfide gas (H2S) which smells like rotten eggs.
My overall impression is that the advantages outweigh the disadvantages, and bioreactor landfills are a better way to deal with solid waste. However, it remains questionable whether or not this emerging technology is right for Arizona because of the increased water requirement. The costs and benefits should be carefully weighed.