Rapid City has gas, but it isn't reaching for the Rolaids.

At least, it might have gas - methane to be specific - percolating in the decomposing garbage at the city landfill.

If there is enough of it, the gas could become a commodity that the city sells to energy companies or other entities interested in using it as an energy source.

Jerry Wright, Rapid City's solid-waste manager, said the city has had several inquiries about buying or using gas generated by the landfill. On Tuesday, the public works committee authorized the solid-waste division to seek proposals for professional services to study landfill gas.

"Billings is doing it. Fargo has done it very successfully," Wright said after the meeting.

According to recent media reports, Billings is considering a partnership with Montana-Dakota Utilities to collect methane from the Montana city's landfill, something that could earn the city $20 million over 40 years. Sioux Falls is building an 11-mile pipeline to pump methane from its landfill to an ethanol plant near Chancellor, something that could bring that city $2 million per year.

Wright is optimistic that Rapid City could work out something similarly lucrative.

"There's definitely methane there," he said. "We've had … a couple of companies who came out and looked at it. They looked at our size, our history, and they were very interested."

When garbage is covered at the landfill, anaerobic processes break down the material, creating methane and carbon dioxide. Wright said capturing those gases would benefit the city financially and help the environment.

"It would take a usable energy source and put it back into the economy, it would eliminate the emission of carbon dioxide and methane into the atmosphere, which is a greenhouse gas, and it could mean some revenue for us," he said.

In addition to the landfill gas study, the professional consultant will conduct a nonmethane organic compound investigation, something that is required every five years by the Environmental Protection Agency. Wright said previous investigations in 1993 and 1998 found no problems.

Wright said the consultant will need a strong background and experience with landfill gas to help the city determine how to market and sell its gas. The city could build a system to extract the gas itself, or it could contract with another entity that would build, maintain and operate the system and pay the city royalties for the gas produced.

"My intuition tells me we'd be better off working with someone who really runs those kinds of systems," Wright said.

By capturing greenhouse gases, the city can earn carbon credits by reducing emissions below a certain level. Those credits can be sold on the international market.

"When you do this kind of project, you get carbon credits because you're reducing the emission of carbon dioxide. Those are worth some money, I understand. Those may be worth more money than the gas," Wright said.

Wright said the landfill gas study would likely be done late this year or early next year. The consultant will first conduct the investigation before doing the methane study.

The city's public works committee unanimously approved seeking proposals from landfill gas consultants. Unless a Rapid City Council member has questions, the request for proposals will be automatically approved during Monday's council meeting.

Contact Scott Aust at 394-8415 or scott.aust@rapidcityjournal.com