From cow manure to natural gas

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Just one of the cows at this Kuna dairy farm generates 65 pounds of manure a day. Photo by Sharon Fisher.

Intermountain Gas is working with Idaho dairies to help convert cattle manure into renewable natural gas, a process that would produce energy and create a use for the manure.

While Idaho has eight dairies converting cow manure to electricity, and other projects to generate renewable natural gas from other sources, this would be the first time that in Idaho that cow manure was used to produce renewable natural gas.

The state is rich in this resource. As of January 2017, Idaho had 580,000 milking cows, according to the United Dairymen of Idaho. A single cow producing 65 pounds of manure a day means 18.9 tons of cow manure a day. And that’s not even counting Idaho’s 2.1 million beef cattle, according to the Idaho State Department of Agriculture.They generate an additional 68.3 tons per day.

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Scott Madison

The Intermountain Gas project would place anaerobic digesters at the farms, said Scott Madison, executive vice president and general manager of the Boise company. The waste is run through the digester, which gathers the methane. Methane is very similar to natural gas, and the process produces biogas, the mixture of gases produced by the breakdown of any organic matter. Intermountain Gas then cleans the biogas, converting it to renewable natural gas, to meet its standards for pipelines and remove any corrosive material. At that point, it could be injected into the Intermountain Gas pipeline system, he said.

Intermountain Gas wouldn’t pay any more for the biogas than its typical monthly spot market price, he said.

“As long as our company is made whole, it reduces pollution and reduces waste,” Madison said. “We’re not asking our customers to subsidize it and we’re not making any financial contribution.”

Patrick Serfass

The federal government is also offering a significant subsidy for biogas. That subsidy is attracting attention to biogas nationwide, said Patrick Serfass, executive director for the American Biogas Council, in Washington, D.C. “About three years ago, almost every biogas project was generating electricity,” because of a 30 percent federal tax credit, he said. Because that tax credit expired, “Now virtually every project is looking into generating renewable natural gas.”

Serfass said he was aware of only one state, Vermont, where a utility was selling renewable natural gas to its customers as natural gas. Typically, the utility uses the natural gas to generate electricity or to fuel its vehicles, he said. Using renewable natural gas also lets a utility say it’s using more renewable sources, which is increasingly a marketing advantage, he said.

In addition to selling the biogas, dairies can realize other benefits, Serfass said. Once the digester is finished with the manure, liquids and solids remain, with the nutrients from the manure. Dried solids have the consistency of sawdust and can be used as bedding for cows, Serfass said. Then, the dairy can put the bedding back into the digester and keep recycling it, he said.

At the moment, dairies are still considering whether to build anaerobic digesters for the project, Madison said. Eight Idaho dairies in the Magic Valley are already using anaerobic digesters to generate electricity.

Large-scale dairies are typically required to follow detailed manure recycling plans, according to the United Dairymen of Idaho. Typically, “It is applied to fields as fertilizer,” said Rick Naerebout, chief executive officer for the Idaho Dairymen’s Association, who said he couldn’t name dairies working on the project. “Manure is the original organic fertilizer.”

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Rick Naerebout

But Naerebout wasn’t sure how many dairies would make use of the program. “In Idaho, we enjoy very affordable utility rates, so it makes projects like methane digesters more difficult to be affordable for dairymen,” he said.  “Given those same economics, digesters are only feasible on the largest of the large dairies, so it is not something our average dairy can consider as part of their manure management system.”

Another biogas project, in Parma, is in the design/engineering stage, with some announcements possible this fall, said Tina Wilson, executive director for the Western Alliance for Economic Development, in Wilder. The project, first announced in 2016, would create paper food containers out of sorghum, and then use the sorghum waste with an anaerobic digester to create biogas.

California Bioenergy is working with Land O’Lakes Inc. to generate renewable natural gas from California dairy farms. Similar projects are also underway in European countries such as Denmark. A plan to generate electricity from the Ada County landfill by Dynamis Energy LLC ended in 2013.

Idaho utility rates drop due to tax cuts

An Idaho Power transmission line lattice tower in a suburban environment near East Boise. Photo courtesy of Idaho Power.

Like so many dominoes, a series of Idaho public utilities reduced their rates on June 15, effective back to June 1. The Idaho Public Utilities Commission, which issued the announcements, credited the rate reductions to changes in federal and state tax laws.

“A main feature of the tax law that took effect Jan. 1 was to reduce the federal corporate tax rate from 35 percent to 21 percent,” noted one such release, from the Idaho Public Utilities Commission. “Soon after the federal law took effect, Idaho Governor C.L. ‘Butch’ Otter signed into law House Bill 463, reducing the state’s corporate tax rate from 7.4 percent to 6.925 percent. Since a utility’s tax expenses are a factor in determining customer rates, the Commission directed all regulated utilities in the state with more than 200 customers to report the financial benefits of the law and how it planned to pass those benefits along to customers.”


Utility rate reductions are as follows:

  • Avista – 5.3 percent for electricity and 6.1 percent for natural gas
  • Idaho Power – 7.06 percent
  • Intermountain Gas – 2.62 percent
  • Rocky Mountain Power – 1 percent
  • Suez Water Idaho Inc. – 5.6 percent