One or more futurists have suggested that farm equipment will be powered by natural gas once again. At one point, there were several natural gas powered tractors being used in the U.S., but emphasis swayed completely away from natural gas to diesel with the price of natural gas and supply issues.

Now, with the latest extraction of natural gas from shale becoming a bigger and bigger industry, vehicles and farm equipment powered by natural gas are making more sense than ever. That is if the shale will be a long-term supply of natural gas.

Because natural gas extraction from shale with today’s methods is relatively new and because there are differing opinions about extraction methods becoming even more efficient, there is no consensus on the natural gas reserves economically available.

How much natural gas is buried a mile or more in shale rock under the U.S. borders?

A 2010 report by the Potential Gas Committee, composed of up to 100 geologists and engineers, put the “most likely amount of U.S. natural gas that could be produced from all sources with today’s technology at 1,898 trillion cubic feet (tcf),” wrote E & E Publishing Service reporter Peter Behr for “Energywire.” Added to that total was 273 tcf of already known, proven reserves by energy companies. Thus, at the end of 2010, the estimate was for about 2,100 tcf of natural gas.

That sounds like a lot of natural gas, and it is a lot considering that the U.S. has been consuming about 24 tcf of natural gas per year, according to Behr. So, do we really have 87 years of natural gas supplies under the U.S.?

There is a lot of discussion and dissent from that estimate about whether the original estimate is correct considering the technology that might be needed to economically extract the natural gas. The more common estimate seems to be an average between 30 years and 87 years or more like 60 years.

As for the price of natural gas, if it were to become the power for vehicles and farm equipment, the logical assumption has to be it would be competitive with petroleum-based fuel. But farm machinery manufacturers aren’t going to retool factories to produce natural-gas-powered equipment if farmers and the ag industry aren’t buying into the switchover.

No energy company is going to leave money on the table by under pricing their resource to the value provided. Behr paraphrased one consultant’s opinions by writing, “It is challenging enough to estimate the size of the gas resource. An even larger mystery is how natural gas prices will move in the future and how that will affect production.”

Perhaps the best quote reported by Behr was, “The shale gas phenomenon is too new. We just don’t know how it’s going to work out,” which was attributed to Alan Krupnick, director of Resources for the Future’s Center for Energy Economics and Policy.

A big switchover to natural gas powered farm equipment is unlikely to happen without more certainty on long-term natural gas supply and cost is worked out.