Can bacteria turn atmospheric carbon into fuel?

Why yes, yes they can! This is an eco-nerd article about the economics of methanogens and carbon — get ready for a technical answer!

If you believe in science, then microbes formed earth’s oxygen-rich atmosphere. Which means, theoretically, they can clean it up for us too. In fact, biota like algae and trees is currently the only way to scrub carbon out of the atmosphere at a planetary scale.

Turns out we don’t need aliens to terraform Earth, we’ve got our own terraforming supplies right here!

Satellit image of Yukon, Alaska, Photo by USGS on Unsplash

This article is based on an even nerdier paper I wrote during a 2009 deep-dive. I got obsessed with how useful bacteria was (it can even degrade nuclear waste!) and I set out to see methanogens could recycle the excess carbon in our atmosphere into more usable fuel.

Spoiler alert, yes. Yes, methanogenic bacteria can scrub carbon out of the atmosphere and concentrate it into usable fuel. But not very efficiently, at least in 2009.

I’m sharing my findings here in the hopes that hundreds of young people will read them and think “I can do better”. This eco-friendly research needs to be expanded and refined!

The problem: we’re running out of oil

Oil is just stored sunlight. But it's not an ideal long-term fuel source because we’re burning through it too fast — currently about 400 times the rate of natural production.

However, the environmental crisis from fossil fuels is a much bigger and more imminent problem

Long-term climate change is controlled by the balance between absorbed vs. emitted solar radiation. Both carbon dioxide (CO​2)​ and methane (CH​4)​ are greenhouse gases which disrupt that balance. Currently, concentrations of CO2​ in the atmosphere are increasing at an alarming rate, from 295 ppm in 1900 to 420 ppm in 2022 in a logarithmic pattern.

This environmental impact is finally getting reflected back to corporate offenders through emissions regulations which will tighten as the cost of climate change (i.e. loss of waterfront housing, desertification, forest fires, and winter snowstorms) becomes more apparent to the public. For instance, Texas lost $130 billion in severe weather attributed to climate change in 2021 alone. (Kind of puts the price tag of geothermal, a bicycle, or a solar panel in perspective right?)

Simultaneously, governmental subsidization of biomass energy has made the development of alternative fuels more cost-effective. In future, we’re going to see increased political and economic pressure in the form of carbon quotas, carbon taxes, and tradable carbon credits.

Renewables like solar, wind, geothermal, wave, tides, hydro, and biogas are all green technologies that are in current use. But there are challenges; first and foremost cost-effectiveness, but also regional and seasonal variability, energy density, and conversion problems.

Wait, we can pull carbon out of the atmosphere?

Carbon sequestration is any technology that reduces CO​2 ​from combustion of fossil fuels from accumulating in the atmosphere, either by collection at the point of combustion or later extraction from the air.

As Lackner pointed out with the help of the Los Alamas National Laboratory way back in 1998, for the urgently-needed sequestration of CO​2​ to be effective:

• It must be safe,
• Disposal must be environmentally more benign than current emissions,
• The sink must form no problems for future generations,
• It must be economically viable, and,
• It must keep atmospheric CO​2 ​ emissions to zero.

Short-term we can reduce CO​2​ emissions from fossil fuels to buy time. We can reduce energy consumption, supplement with renewables, make extraction and combustion of fossil fuels more efficient, and sequester CO​2​ from major emission sources.

But in the long-term we need a replacement for fossil fuels that is cost-effective, and renewable on a human time-scale.

Bacteria to the rescue

On earth, all of the energy we use originated from the sun. And last I checked, the sun is still burning. Therefore we really don’t have an energy shortage; we simply must find better methods for capture, storage, and transport of that energy.

Microbes are wondrous, and very resourceful. They have the capacity to convert organic or chemical energy into a form more practical for human use. They can convert biohydrogen to H​2​, microbial fuel cells (MFCs) to electricity, and… methanogens can make methane​!

Methanogenic archaea metabolize simple compounds such as acetate, H​2 ​ and CO​2 ​ to methane (CH​4​). In microbiology terms they only live in environments with no oxygen (aka. strict anaerobes), require low oxyreduction potentials (Eh <200mV) and prefer solutions with a high Fe content.

So is methane a viable fuel?

Methane is an okay alternative fuel

As a fossil fuel, methane has proved its viability. It’s a principal component of most natural gas reserves, representing as much as 20% of the US energy supply in 2001. But it can also be produced from biofuels in the form of biogas, albeit in lower concentration and with more difficulty. Typically biogass is 40–60% methane and 30–40% C02.

Methane compares well to other alternative fuels. Energy conversion is a big issue for any fuel, currently 65% of energy input into electric power plants is lost, and 65–80% is lost in mobile systems such as passenger cars. In this context, methane is a relatively clean-burning fuel that compares well to electricity and other hydrocarbons.

However burning methane also creates atmospheric C02. Whether this process is environmentally friendly depends on where the carbon originated and what energy is used to produce the fuel​.

Turning atmospheric CO​2 ​ into methane requires a large input of energy. But we live on a rock with free energy because of nearby supernova. We’re not ​ creating​ energy, we‘re​ just converting​ free solar (or geothermal, or nuclear) energy into a form that is easier for humans to use.

(Yes every species on Earth is a big giant freeloader).

So can bacteria make us methane by recycling C02 from the air? How do we do that if the bacteria need to live in an environment with no air?

Making methanogenic bacteria work for us

Methanogens just need high-energy electrons in the form of H​2​ to produce methane. This isn’t super efficient but there are options:

• Fossil fuels: Okay not really an option here…
• Electrolyzed water: Currently it takes about 53 kWh of electricity to produce 1kh of H2 this way. However, there is a pioneering facility in operation in Iceland that converts CO​2​ to methanol using cheap geothermal electricity to produce the H​2.
• Biomass: Biomass is a much more dilute source of energy than fossil fuels the ratio of “energy returned on energy invested (EROI)” is much lower. It’s energy-intensive to grow, harvest, and prepare materials, then extract and separate the products. However, the potential for energy from biomass is huge and a relatively untapped resource. Researchers estimated in 2001 that all of the US energy needs could be supplied by marine macroalgae grown on about 243 million hectares of ocean.

Okay, I’m a believer! Where do we start?

Currently, there are three areas where the use of methanogens could be environmentally progressive, energetically efficient, and technologically sound: as an adjuvant to fossil fuels, capturing methane from organic waste, and converting atmospheric C02 to methane.

1 ) Reduction of emissions from fossil fuel (slowing emissions)
We could recycle CO​2​ in sites with high partial-pressure of CO​2​, or by improving extraction efficiency from fossil fuel reservoirs by digesting hydrocarbons to methane. This would be a short-term solution as it would still result in a net flux of sequestered carbon to the atmosphere.

Burning fossil fuels emits most CO​2 ​ to the atmosphere; however, having a small bioreactor in the muffler of your motorcycle is not practical… yet.

The best target for microbes is the emission from fossil-fuel-burning powerplants which have a high concentration of CO​2​ and a financial incentive to reduce emissions in the form of carbon credits. Autotrophic methanogens could be used to reduce CO​2 ​ sequestered from the stacks with H​2 produced from electrolysis plants powered by alternative energy. As already stated, this is not a permanent solution to the problem but it does allow for additional energy use from fossil fuels, and if the methane were used as a chemical building block for the synthesis of chemicals the carbon might be sequestered permanently.

2 ) Capture of methane from organic wastes (carbon neutral)
Methanogens in landfills, sewage treatment plants, and livestock waste contribute to global warming by releasing methane to the atmosphere. We could capture this methane, and use it to replace fossil fuels with a carbon-neutral technology. This is a well-researched and practical arena for current economic investment in alternative fuels that enhances resources we already have.

We could also capture biological methane emissions more effectively. In most studies on the reduction of greenhouse gas emissions methanogens are considered part of the problem. CO​2 ​ is far more prevalent in the atmosphere than methane and has a longer residence time, but methane​ is 20–30 times more potent as a greenhouse gas. It is estimated that 70–80% of atmospheric methane is of biological origin. Anoxic water in swamps and rice paddies, ruminants, and human and livestock sewage are all sources of emissions with a rich population of methanogens.

Although it is not always logical to capture methane from natural sources, collection from anthropogenic sources such as garbage dumps and human and livestock wastes is both economically viable and practical. Also reprocessing of organic material contained in these sites is carbon-neutral.

Wastewater treatment with methanogens leaves far less uncomposted sludge than anaerobic treatment. Currently, many wastewater treatment facilities use anaerobic bioreactors called microbial fuel cells (MFCs) which attempt to eliminate methanogens with little success but MFC’s don’t generate as much power as methanogens.) We could attach methane collection apparatus to MFCs to generate energy from manure.

3 ) Generating methane from atmospheric CO​2​ (carbon reducing)
We could capture atmospheric C02 either chemically or through biomass, perhaps replacing fossil fuels altogether.

Because CO​2 ​is in equilibrium in the atmosphere, facilities for the capture of CO​2​ could be located anywhere. Ideally, if chemical, next to hydrogen production from alternative energy.

However to-date, biota still appears to have the most efficient ability to isolate CO​2​ in its atmospheric concentration. Plants, trees, and algae are all extremely efficient recyclers of CO2 and crops grown for the extraction of carbon for fuel are becoming more cost-efficient.

Although most technologies currently available are not yet cost-effective there are a few promising areas in which immediate implementation could take place, and it has the additional potential to be used as a carbon-sequestration method.

• Hybrid poplar and switchgrass provide the largest net carbon sink when used to create biomass, ferment to methane, then burn methane electricity generation.
• Saline creeping ryegrass has been used for biogas production followed by compression of the remaining raw fibers into particleboard.

In conclusion

There is potential for the use of methanogens in generating alternative energy and sequestering CO​2​. There is even potential that the use of methanogens could provide a negative carbon balance.

There are several areas for further research in increasing the rate and effectiveness of methane fermentation.
Some methanogens grown at higher temperatures might be more efficient, we could develop smaller more cost-effective fermentation devices for sewage, or experiment with hemp as a biogas crop now that it's becoming more legalized.

This is a popular-science version of a whitepaper produced in 2009 for an Environmental Biology course: Use of Methanogenic Bacteria for Reduction of Atmospheric Carbon Dioxide With Concurrent Production of Methane as an Alternative Energy Source. The full, ubernerdy research paper can be found on Researchgate.

Originally published at https://www.todreamalife.com on May 6, 2022.

Bibliography:

There are probably way more contemporary works available now, but the authors below did a great job when I originally wrote this article in 2009.

Nerd tip: To search for more recent work, type the author’s paper into Google Scholar, and then click “citing articles” to see more recent work on the same topic.

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