San Francisco Architects’ horror on landfills continues w/ Bioreactors
Following our last blog, we continue here to discuss a possible, but better alternative to a traditional landfill.
Man made objects decompose just as well as organic matter, only the outcome is more toxic and does not in any way facilitate the natural cycle or eco-system, The process also takes much longer, creating other problems. Storm water drainage systems help divert liquid away from a landfill site, further, sealing the garbage delays decomposition of trash in a typical landfill instead of encouraging it. Liquid diversion, keeps the trash sealed and trapped as a toxic concoction, ready to be dug up years later. Accelerated decomposition on the other hand, reduces the footprint of solid waste and instead of the need for building more landfills, it allows the same landfill to be fed periodically and eventually decomposed in 5 to 10 years.
A clear answer to the world’s trash and landfill problem is this concept behind bio-reactors. In a bio-reactor liquid from leachate (at least 30%) is introduced back, along with, storm water and diverted waste water into the garbage pile to speed up decay. With water, air is also let in to allow microbial degradation. A typical landfill has roughly 30% and up of putrescible waste, such as paper, cartons etc., which decay faster than other waste. Introducing water encourages bacteria to eat putrescible material and accelerates decaying meanwhile producing Methane as a by-product.
A bioreactor can be aerobic or anaerobic or possibly a hybrid of the two. In an aerobic process leachate is piped to storage tanks and is then reintroduced into the landfill with controlled circulation. Air is also introduced with the leachate. An Anerobic bioreactor landfill operates by adding water with leachate and other sources, this process encourages decay in the absence of oxygen and produces Methane which is captured to fuel energy sources. A Hybrid bioreactor accelerates decay with both aerobic-anaerobic treatment. A hybrid speeds up decay and the production of Methane. Both being tremendous advantages of a bioreactor over a traditional landfill. This alternative reduces the need for more land to ‘house’ trash and re-uses toxic by-products of decay to decrease greenhouse gas emissions, use of fossil fuel and contamination of groundwater or ground surface.
The construction of a typical bio-reactor uses plastic sheathing at the bottom, then irrigation pipes are set through layers of waste. The leachate that settles on the bottom is pumped back up strategically, to re-circulate through the irrigation pipes, encouraging faster decomposition. Methane gas is trapped and piped, with a large diameter high-density polthylene pipe and transported to an energy powering facility. There is also a plastic sheathing on top that traps the Methane and keeps it inside. Methane in a bioreactor is produced at a much faster rate than a traditional landfill, therefore, key is the efficiency of a system that traps and transports Methane.
An average size bio-reactor can feed energy to power up to 500 homes, and with these becoming the norm, you can only imagine the potential. . . . .