If you live near — or even pass by — a landfill, you know that one of the problems they present is the noxious odor. Unpleasant at best, landfill gas, composed primarily of methane and carbon dioxide, is also a toxic greenhouse gas contributing to climate change.
A natural byproduct of the decomposition of organic matter by anaerobic bacteria in an oxygen-depleted environment (such as beneath a pile of rubbish), methane constitutes about 9% of human-created greenhouse gas emissions. About 35% of that comes from landfills.
For the most part this gas goes to waste, drifting off into the atmosphere where it contributes to climate change, but not before annoying the olfactory senses of anyone nearby. Since it’s explosive, the gas produced in landfills is often simply flared off. This reduces the explosion risk, but does nothing to help the environment.
What if there was a way to capture this gas and put it to good use?
There are a number of options. The gas can be burned in boilers to produce heat, used as fuel for gas and steam turbines, and used as fuel in internal combustion engines.
The problem with all of these options is that landfill gas also contains a variety of both organic (non-methane organic compounds or NMOCs) and inorganic contaminants including benzene, carbon tetrachloride, chloroform, and mercury. Many of these are highly toxic and carcinogenic.
If the gas is simply burned, these contaminants are released into the atmosphere with the potential to cause significant damage both to the environment and to human health. Further, the burning process itself produces other contaminants, including furans and dioxins.
Hardly a “green” option.
It is possible to clean and filter landfill gas, expelling carbon dioxide, and trapping contaminants. The purified biogas can then be used in fuel cells to produce electricity, or channeled into natural gas pipelines. (Natural gas is about 70% to 90% methane.)
The problem with this is that cleaning the landfill gas is an expensive process. Since natural gas is still relatively cheap there’s little economic incentive for companies to process landfill gas.
Fuel cells, besides needing the more expensive purified gas, are themselves still quite expensive and presently incapable of producing great quantities of electricity at competitive rates.
Even if landfill gas is sufficiently purified for inclusion in natural gas pipelines and fuel cells, there’s the matter of transporting it from the landfill to wherever it’s needed, another expense.
Nevertheless, some companies have found a way to make the process economical, at least under specific circumstances.
Beginning in 2009, the world’s largest landfill gas to liquefied natural gas (LNG) conversion facility will begin operations at the Altamont Landfill near Livermore, California, USA. Linde North America (part of The Linde Group) and Waste Management will cooperate to produce up to 13,000 gallons of liquid natural gas a day, using the fuel to run Waste Management’s collection trucks. This will essentially “close the loop,” using the garbage collected to fuel the vehicles that collect the garbage.
If it’s successful, it will undoubtedly lead to other facilities, perhaps eventually to a culture where garbage is considered a valuable resource rather than an expensive liability.