Methane Capture at Landfills
In the United States, landfills represent the biggest single source of human-caused methane emissions. Methane is an incredibly potent greenhouse gas, and a big reason why waste accounts for a full three percent of American greenhouse gas emissions. The good news is, there’s been considerable technological advances of late in the ability to capture methane released by landfills—something known as “methane capture.” Capturing methane not only prevents further contribution to global warming, but also can be converted and used as an energy source. In this process, landfill gas (or LFG) is extracted from landfills by drilling wells and a sort of high-tech vacuum system to pull the noxious drafts into a tank for processing. After being captured, the LFG can be put to a number of uses—generation of electricity for use on site or for sale back to the grid; cogeneration (which produces both electricity and thermal heat); direct-use, which can offset the need for other gas-fuels to power boilers, kilns, or other heat-dependent processes; and, finally, as an alternative fuel, as it can be pumped directly into natural gas pipelines and can even fuel vehicles in the form of compressed natural gas.
The EPA runs a voluntary Landfill Methane Outreach Program that helps landfill operators figure out how they can incorporate methane capture into their facilities. More info about that program can be found here.
Plasma Gasification
What if we could get rid of all our waste, not by shipping it off to some unseen landfill in somebody else’s backyard, but by heating it to temperatures more typical of the sun than the earth, in a process that generated more energy than it used, and didn’t produce a bit of air pollution? Well this concept is not merely the stuff of science fiction, but rather an innovative new technology that has the potential to change the way we consider waste.
It’s called plasma gasification, and to understand how it works, we’ll need a little bit of a science lesson. And first, we’ve got to understand plasma—that mysterious “fourth state of matter” that’s actually an ionized gas occuring only at extremely high temperatures. While we’ve only recently come to really understand plasma, it’s as old as the universe, as is plasma gasification. The best example of a plasma field here on Earth is in the form of lightning, where the gas creates a current and has a magnetic field, because if its unattached, free-roaming electrons.
The key function of plasma gasification is plasma conversion, and the key element of a plasma converter is the plasma torch, a device that sends high voltage current through the air-tight chamber to temperatures higher than those found on the surface of the sun, maybe 30,000 degrees Fahrenheit. Essentially, it creates lightning in the sealed container, stripping electrons from the air and creating an energy field so intense that solids don’t stand a chance. At these extreme temperatures, waste (or anything else unfortunate enough to be stuck inside) is totally disintegrated, as molecular bonds are broken and solids are reduced to their fundamental elements. A noxious chemical like cyanide, for instance, is broken down to basic carbon and nitrogen. Even something as dangerous as Agent Orange will come out of this plasma bath as a harmless glass and synthetic gas, commonly called “syngas,” which can pretty easily be converted into valuable alternative fuels like ethanol, natural gas, and hydrogen.
Besides the syngas, there can be another convenient byproduct of the process: electricity. Sure, to get the process started, electricity must be pulled from the grid. But after that initial jolt, the gasification is underway, and this is where it gets really interesting. The syngas produced is a smoldering 2,200 degrees Fahrenheit, and is immediately pumped into a cooling chamber, at which point a heavy stream of steam is released. Any sensibly designed converter will use this steam to spin turbines, thus producing electricity. More than enough juice, in fact, to power the whole operation—grinder, plasma torch, and every other moving part. The entire process becomes, after the initial spark, self-sustaining. ....read more
