Ending our excursion into nuclear over the last few posts, we are going back to the ELI5 explanations of how various kinds of renewable energy work. Today we are going to talk about biofuels and more specifically landfill gas, LFG. Outside of the pollution caused by our energy consumption, the population of the United States produces 292 million tons of trash, annually. Out of these 292 million tons, at least 39.89% is comprised of some sort of biomass. Biomass meaning food, yard trimmings, wood, etc.… All of this biomass produces methane while it decomposes. The issue with methane vs simply carbon dioxide is that it is a more harmful to the planet. Over the course of 100 years, methane has the potential to have an impact 25 times larger on global warming than carbon dioxide.
Now the amazing thing about methane is that it is combustible and thus can be used as energy! But you may be asking yourself, why burn methane back into the atmosphere if it is so bad for the environment? When burned, methane gas produces carbon dioxide and water as waste material. Now this isn’t to say that we want to be producing carbon dioxide to power our grid, but it is a clear winner when compared to releasing methane directly into the atmosphere as methane is the more potent greenhouse gas. Methane combustion may not be the final solution to carbon emissions and global warming; however, it definitely buys us some more time by slowing the rate at which greenhouse gasses are emitted into the atmosphere.
So now that we can agree that collecting and combusting methane is the lesser of two evils, how do we collect it? Well, once we have a landfill, we need to treat it similarly to a well. The landfill needs to be covered to ensure that methane emissions do not escape into the atmosphere. These emissions are harvested through a gas well that then pumps the raw emissions into primary processing and flare. The primary processing step is to remove any moisture from the gas collected. Depending on the destination of the gas there can also be secondary and tertiary processing that will further remove compounds from the gas to ensure it meets certain standards. For example, in the second phase of processing siloxane and sulfur will be removed from the gas and then the product can be used to run a boiler. Underdoing further processing would remove other gases in the gas mixture depending on the intended use of the gas. With the appropriate treatment this gas can be used to power vehicles, produce electricity, or other industrial uses.
Though methane and land fill gas may not be an ideal solution to our electrical and fuel needs, I believe that it is without a doubt a necessary tool to utilize along the way to a net zero carbon future. If you agree or disagree leave a comment below to continue the discussion.