Biogas: Nature's Energy Solution
What is Biogas?
Biogas consists of roughly 60 percent methane, 40 percent carbon dioxide, and a trace of sulfur dioxide (which makes the gas smell slightly like rotten eggs if enough is present). It is created during the process of anaerobic digestion, whereby organic waste, or “biomass”, is digested by microbes and produces methane gas.
In the U.S., the largest producers of biogas are municipal landfills and sewage treatment plants, however, biogas is also produced from the digestion of other biomass such as food production and paper mill waste, and livestock waste from the meat and dairy industries.
Biomass can be further converted into a nutrient-rich material called “digestate” through the use of anaerobic digesters—large, sealed tanks void of oxygen that utilize heat (around 86 to 100 degrees Fahrenheit) to kill the pathogens found in most biomass. This leftover digestate is often incinerated on-site at sewage treatment plants or hauled off to landfills.
A sewage treatment plant that produces biogas in Hamilton, Ontario. Photo from Biocycle.net.
Why Use Biogas?
Proponents of biogas point out that the practice of disposing of this biomass is not only costly, but also overlooks the opportunity to convert organic waste into a highly useful (and potentially profitable) organic fertilizer that is naturally rich in potassium, nitrogen and phosphate. According to British journalist and author Rose George in her book, The Big Necessity, applying digestate from anaerobic digesters to crops in China “increased vegetable yields by 50 to 60 percent.”
The U.S. Energy Information Administration (EIA) explains that some industries collect and use the biogas that they produce in order to heat their digesters, thus "closing the loop" in terms of energy usage. This means that these industries have a neutral carbon footprint because the amount of carbon dioxide they produce is equal to that which they consume. The EIA estimates that in 2017, “about 107 of these types of waste treatment facilities in the U.S. produced a total of about 1.2 billion kilowatt hours (kWh) of electricity.”
The applications of biogas are vast. According to the Environmental Protection Agency’s (EPA) website, “Biogas can replace fossil fuels for the production of heat, power and fuel.” Additionally, biomethane can be produced by filtering out most of the impurities (like carbon dioxide) found in biogas, which can then be used to fuel cars. The EPA also states that biogas can ameliorate our carbon footprint by reducing our dependence on carbon-emitting power plants.
A closed loop, or circular, economy fueled by biogas. Photo from Biogas Action.
Current Biogas Usage
According to the U.S. Biogas Council, there are only around 2,100 industrial sites that currently produce biogas in the U.S.:
247 anaerobic digesters on farms
1,241 wastewater treatment plants use anaerobic digesters (860 of which use the biogas they produce)
38 standalone anaerobic digesters
645 landfill gas projects
Universities are taking the lead on much of the biogas research and development. For example, the University of Michigan has a 300,000 gallon anaerobic digester that the college is using to tackle its growing footprint (see the video below).
Does Biogas Have a Future?
Of course, there are several obstacles standing in the way of biogas's ability to replace fossil fuels, which George cites in her book as the power of the oil industry to “disincentivize” alternative fuel sources and the lack of infrastructure necessary to sustain biogas technology.
George also points out that anaerobic digester technology is still far from perfect, especially on a scale large enough to handle the multitude of waste produced in cities like London and New York. And, like many renewable energies, front-end conversion costs prevent many waste industries from utilizing biogas.
Additionally, because biofuels like biomethane aren’t 100 percent clean, they can have the unfortunate side-effect of corroding motor vehicle engines.
Because the production of biogas releases methane—a greenhouse gas more toxic than carbon dioxide—into the atmosphere if it isn't captured, biogas must be utilized as a fuel source in order for it to be sustainable. Many industrial facilities simply "flare" the methane emitted from biogas (meaning they burn the gas as it's emitted so it doesn't seep into the atmosphere), when they could be harnessing it for energy, or even selling it.
While there are significant drawbacks to implementing biogas on a large scale, it is a viable energy solution that demands more attention. The University of Florida points to a lack of public awareness, as well as the low prices of fossil fuels as two main reasons why biogas isn’t widely used or discussed. However, if biogas can circumvent the oil industry and garner public support, it has the potential to become a fully sustainable energy model that the entire world can benefit from.
