Putting Climate Change Heroes And Villains Under The Microscope

It is often said that a compelling drama needs both heroes and villains. The unfolding Climate Crisis is an all-too-real drama, and it involves human actors playing both of those roles. However, there are some important heroes and villains in the “cast” of the climate story that really need to be “put under the microscope.” That’s because they are too small to see with the naked eye – they are bacteria. These tiny “actors” often play a villainous role when they grow on our organic waste-streams because they can produce the potent greenhouse gas, methane. Technically they are “methanogens.” Some human movie actors are well known for their ability to convincingly portray both heroes and villains. Given the right script, “Methane-makers” can switch to a heroic role.

Methane Is An Important Greenhouse Gas

Methane emissions matter because that gas has between 25 and 120 times the global warming effect of carbon dioxide depending on the time frame being considered. The EPA estimates that it represents 11% of the human-linked greenhouse gas problem for the U.S. 38% of those methane emissions are directly linked to the fossil fuel industry – primarily in the form of leaks in the process of mining, drilling or distribution of that energy. But there are also a lot of problematic methane emissions that occur when “Methane-makers” live on things like our food waste, animal manures, sewage. If there is oxygen available to these bacteria, most of them will use it just like we do, but if there isn’t much oxygen around, they switch over to their “dark side” mode as “facultative anaerobes” and generate methane as they continue to break down their organic food sources. For instance, this happens when organic waste gets buried in a landfill. In that setting the methanogens do their “villain thing” and the EPA estimates that is the source of 17% of U.S. human-related methane emissions. Another 9% happens in animal feeding operations where manure collects in piles or lagoons in ways that limit the oxygen supply.

Anaerobic Digesters Are The Most Common Way To Recast Methane-Makers As Heroes

The positive “plot twist” comes when people “recast” the methane-makers as climate heroes by capturing the gas before it can get into the atmosphere. The role for these bacteria is now turning our waste into a clean energy source called Renewable Natural Gas or RNG. Even though all methane is made up of the same simple chemical of one carbon atom attached to four hydrogen atoms, the energy generated using RNG can reduce the need for fossil fuels and when it is burned it is classified as “climate neutral” because the CO2 that is release was recently captured from the atmosphere by a plant and is being returned without effectively adding to the net balance of greenhouse gases. RNG can then offset some fossil fuel demand, and it is complimentary to the renewable energy from wind and solar with the advantage of constant availability.

So where are the methanogens being recast in this better role of making “biogas” or RNG? The most established settings in “anaerobic digesters” – big tanks set up to handle waste from sources like dairies or food processing plants. These digesters are quite capital intensive and non-trivial to operate so they are more common at large facilities. One way to get around this limitation is through cooperatives, an example being a digester installed at Flood Brothers Farm in Maine which handles the waste for 5 small dairies that supply Cabot Creamery.

Biogas can also be collected from landfills. Depending on the use of the methane from digesters and landfill there are different clean up steps required to remove certain sulfur compounds and other volatiles. So while biogas production has been going on for some time, it is attracting a new wave of investment in facilities that script hero roles for Methane-Makers.

One example is a company called Opal Fuels which develops both anaerobic digesters and methane capture systems for landfills. Depending on the location, they use the methane to generate electricity on site, make fuel for fleets of natural gas powered trucks and equipment, or put the gas into the nationwide natural gas pipeline system. The economics can be quite attractive because with third party auditor certification the Renewable Natural Gas qualifies for RIN credits paid for by fossil fuel refiners in accordance with the Renewable Fuel Standard Program.

Another example is the energy investment group Quinbrook Infrastructure Partners. They have been investing in methane capture systems for landfills for 25 years – mainly in Australia and the UK where regulations have required liners and caps on landfills that essentially turn them into anaerobic digesters. This is becoming more common in California and the Northeastern U.S. Quinbrook recently acquired a company called Purpose Energy which has extensive experience setting up methane capture systems for diverse sources of organic waste and proprietary technology to make that more efficient. That business is booming because of the investment credits now available through the Inflation Reduction Act, and their projects generate the kind of long term income that Quinbrook favors in its investment strategy. Many of their projects involve processor level food waste from players like Danone and Unilever
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. Purpose Energy is also good at the tracking and tracing of the energy output because measurement is critical for Scope II and III ESG reporting needs and to prove that any associated carbon footprint claims are not “greenwashing.”

Not all the methane can be captured from landfills because some highly digestible organic matter is broken down before the collection tubing can be installed. That is why a state like California is trying to get people to put that kind of organic matter with the yard trimmings in the “green bin” for composting. In theory the composting process makes plenty of oxygen available to the microbes that are breaking down the organic matter and if that is true then any methanogens present should be wearing their “white hat” and not making methane. That sounds great in theory, but in practice there are always some parts of a compost pile that don’t have enough oxygen and so the Methane-makers shift into their villain mode.

Another place that Methane-makers live is in the first stomach or “rumen” of cows and other ruminant animals. That rumen is actually a very important way that we humans can tap into solar energy. Plants capture the energy from the sun as they grow and store a great deal of it in the form of cellulose – the single most abundant biopolymer on earth. We can’t digest it, but with the help of bacteria that live in their rumen, animals like cows can turn that cellulose into human-available food energy.

Methane-Makers Can Have Another Superpower

There are Methane-makers that are playing in a different venue – the digestive system of cows and other ruminant livestock. These cast members are doing something that would be challenging for even the most gifted human actor – they are playing hero and villain at the same time. They are among the bacteria that allow ruminants to digest cellulose thus giving humans indirect access to the most abundant form of stored solar energy in plants which we wouldn’t otherwise be able to digest. But at the same time they are generating their signature gas which the cow then burps out into the atmosphere – a source that represents 27% of human-linked methane emissions. Fortunately, this cow related methane issue can be significantly diminished by as much as 30% using specific feed additives. There is also a company called smaXtec which has developed an advanced bolus technology which monitors the health of the cow from inside the reticulum (one of the four compartments of a ruminant animal’s stomach). This advanced health system not only supports overall animal welfare and the lifetime productivity of the cow, recent calculations show how the use of this tool can lead to a 15% reduction in methane emissions per unit of milk production through improved disease management and early intervention.

Enter The Methane-eater Bacteria With Two Different Superpowers

But recently this story is seeing a plot twist introducing some new cast members – a different kind of microbe that doesn’t produce methane, it consumes it as its main source of energy! These “Methane-eaters” are known as “methanotrophs” and they are land creatures related to ancient creatures like that live near methane vents at the bottom of the ocean. To make the story even better some Methane-eaters also have the rare ability to capture nitrogen gas from the air and convert it into forms that are usable not just to them but also to plants and animals. There is a company called Windfall Bio that is working out ways that tap into these two microbial “superpowers.” For instance, a layer of these organisms on the top of a compost pile can scavenge the fugitive methane emissions and increase the final nitrogen content of the finished compost by up to 2%. Another alternative is to coat something like tiny glass beads with the bacteria and then run a methane containing airstream through that matrix at a rate which allows the bacteria to scavenge that gas in order to grow and at the same time build up nitrogen as their numbers increase. Periodically the bacteria can be washed off the beads, dried and used as a source of nitrogen-rich fertilizer (up to 15% N). Because the nitrogen they fixed is now in forms like amino acids it makes a “slow release” fertilizer that is less prone to causing emissions of nitrous oxide – another problematic greenhouse gas. The bacterial fertilizer also includes some potassium and phosphorus which are also key nutrients for plants. This system works most efficiently when there is a good deal of methane in the airstream, but even levels as low as a few parts per million will support growth of the Methane-eaters.

This approach is a great fit for situations where because of scale or other limitations the economics don’t justify the capital cost of full-fledged anaerobic digester or RNG capture system. Examples might include a manure lagoon at a hog barn that is simply trapped under a “lagoon cover” and either flamed off or currently used for local heating purposes. But regardless of the setting there are two potential value streams that could drive the adoption of this technology – carbon credits for preventing methane emissions and sales of a low carbon footprint fertilizer.

So there are several ways that microscopic Methane-makers and Methane-eaters can be given the chance to play their hero roles and help us address some of our climate challenges and contribute to the possibility of a happy ending to that story.