Cow poop could help us make clean(er) energy

Extracting methane from biogas could create fuel without fracking.

Wisconsin dairy farm.
Wisconsin dairy farm.Pixabay

During the summer of 2016, chemical engineer David Simakov took a leisurely drive through the farmlands of southern Ontario. During his trip, he stopped at a farm that was producing biogas from manure, then burning it to create electricity. Ever the scientist, Simakov began to wonder. Would it be possible to take that biogas one step further and refine it into natural gas?

Natural gas, though a significant contributor to climate change, is the cleanest-burning fossil fuel. Turning cow manure into natural gas would have three big advantages. First, it would turn animal waste, a major source of carbon pollution, into a useful fuel. Second, it would provide a new source of natural gas, which could be used to replace dirtier fuels like coal and oil. Third, it would reduce the need for fracking, the environmentally-destructive practice that extracts natural gas from the earth.

“I am always thinking about ways to improve,” Simakov said. “Why not use the full potential of manure biogas? We already know how to make biogas from manure and how to make electricity by burning that biogas. So I thought: we can use electricity to upgrade this manure biogas to make a renewable natural gas.”

Simakov describes the refined biogas as "renewable" natural gas because cows could provide a limitless supply, in contrast with the natural gas that comes from the ground, which is finite. More importantly, cows are largely recycling atmospheric carbon. Grass scrubs carbon from the atmosphere, which cows eat and then return to the sky. Burning natural gas from underground adds to the total volume of carbon pollution in the sky.

Simakov wants to turn biogas into natural gas. Biogas results from organic matter such as manure degrading in the absence of oxygen. Biogas is roughly half methane — the main component of natural gas — with the rest being trace gases and carbon dioxide, the latter a potent greenhouse gas that contributes to climate change. His idea is to turn the remaining CO2 into methane, making the final product completely natural gas.

Natural gas drilling sites.
Natural gas drilling sites.Bruce Gordon, EcoFlight

The idea of excrement as a fuel source isn't new. Also, dried manure already is used as a fuel source in many countries, although burning dried manure creates a lot of air pollution, which poses a significant disadvantage. Simakov's concept, on the other hand, is different. "The process we've developed is not based on burning dry manure," Simakov said. "It is based on extracting biogas from manure by anaerobic digestion, while using the liquid and solid residues as a fertilizer and for animal bedding, respectively."

Simakov, assistant professor of chemical engineering at the University of Waterloo's institute for sustainable energy, built a computer model of a 2,000-head dairy farm to conceptualize the process. He described his procedure in a paper recently published in the International Journal of Energy Research.

Here's how it would work. First, the machine gathers hydrogen by passing an electric current through water to separate the hydrogen from the oxygen. Then, it mixes that hydrogen with biogas and runs it all through a catalytic converter, turning carbon dioxide (CO2) into methane (CH4). To be sure, the process requires electricity, but it would be "renewable energy on-site," or "surplus electricity," Simakov said, adding: "It has to have a low carbon footprint."

Livestock waste yields biogas, which is refined into natural gas.
Livestock waste yields biogas, which is refined into natural gas.International Journal of Energy Research

“There are multiple ways we can benefit from this single approach,” he said. “The potential is huge.” The system could work where there are large farms that have thousands of animals. “The farm has to be high-tech and centralized, so that manure is easily collected,” he said. “Modern dairy farms are like that.”

The technology is viable with several kinds of manure, cow and pig in particular, as well as with gas from landfills, a type of biogas, he said. Cow and pig waste “is good because it gives a lot of biogas per unit of weight,” he explained. “Whereas, chicken manure is not good in that sense.” The landfill potential is especially promising.

“We are talking about producing the amount of renewable natural gas [that would be] enough to heat thousands of homes from just a single large landfill site,” Simakov said. In addition to home and industry use, renewable natural gas could replace diesel fuel for trucks, a significant source of greenhouse gas emissions, he said.

Dairy farm.
Dairy farm.Pixabay

The model calculated that a $5 million investment in the system at the Ontario farm would, with government subsidies for renewable natural gas, pay for itself within five years. Nevertheless, it still initially would cost more than conventional natural gas. “It depends on the cost of electricity,” Simakov said. “But it will be at least two or three times more expensive than the current cost of natural gas.”

He predicted, however, that the move to widespread use could be seamless and cost-effective. “Renewable natural gas is fully interchangeable with conventional natural gas, with no need for new distribution infrastructure,” he said. “The transition can be smooth, adding more and more renewable natural gas until we don’t use the fossil natural gas at all.”

Like many scientists studying clean energy options, he believes society must embrace renewables, particularly if climate change continues unabated, “to avoid a catastrophic disaster in the near future, such as seeing [parts of] New York City or the Florida coast under water,” he said, adding, “We need to stop pumping carbon from underground into the atmosphere, and start caring about introducing more and more renewable energy to make our lives more sustainable.”

Marlene Cimons writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture.