The best questions are the obvious questions that you never thought to ask before.

Like this one: Why is natural gas delivered directly to homes via pipelines, while propane is delivered to backyard storage tanks via tanker trucks?

Natural gas and propane are sort of the same stuff – molecular clumps of carbon and hydrogen atoms that we burn as fuel, mostly for heating. So why can’t they be handled the same?

That question came to mind recently when I saw a presentation by an MIT spinoff called OsComp, which says that it now can deliver natural gas by trucks. CEO Pedro Santos gave me a follow-up phone interview, discussing the firm’s “virtual pipeline” that provide industries, schools and other large energy users with another heating-fuel option even if their local gas company hasn’t hooked them to the pipeline network.

OsComp, partnered with energy-supply firm Global Partners, is getting set to build a processing center in Bangor, Maine, where it will take natural gas from a pipeline and fill its special tanker trucks, and is moving toward another in Massachusetts. It’s got customers in the oil and gas fields of Texas and Oklahoma, Santos says, and may be part of the New England scene before long.

Basically, OsComp wants to handle natural gas the way propane is handled: Have it shipped across country by pipeline, then pumped into trucks for the last mile. Which returns us to the question of why they’re different.

The answer is that a molecule of propane has more carbon atoms than a molecule of methane, the component of natural gas that we burn. Therefore, propane is harder to break apart or, in human terms, has a higher boiling point.

(That sound you hear is from chemistry teachers sputtering with indignation at this wildly over-simplified explanation; I expect to see some emails when I get to work.)

Methane (CH4) boils at minus 263 degrees but propane (C3H8) doesn’t boil until a relatively balmy minus 44 degrees.

As a result, propane can be readily handled as a liquid, which is easy to truck around, whereas methane is almost always handled as a gas, which is better done via pipelines. That’s the reason, although many details have been left out.

One of the things that I learned researching this is that propane is more popular than I realized.

I think of it as fuel for backyard grills and home heating, but it’s a major industrial fuel in parts of the country and, even more surprising, is as much an alternative vehicle fuel as compressed natural gas, the fuel being tested by Nashua for its garbage trucks.

Tucker Perkins, chief business development officer at the Propane Educational and Research Council, said there about 147,000 propane-powered vehicles in the U.S. today.

At the moment, he said, propane refueling stations cost “about one-fifteenth” as much as a natural gas refueling station to build – again, because of the boiling point difference, which means natural gas requires much more pressurization.

When I described OsComp’s business model to him, Perkins’ response was: “That’s probably a good idea, but it’s not nearly as good idea as using the propane already in those markets.”

OsComp, of course, disagrees.

The heart of the company is a new compressor design that can handle natural gas containing water vapor or other hydrocarbon liquids (aka “wet gas”) and whose rotary design is smaller and far more efficient than traditional compressors. It was developed with help of various clean-energy funding, including millions from the U.S. Department of Energy, and a host of clean-energy and tech-start-up prizes, and is being used to improve well production.

Santos said OsComp’s compressor, combined with various technical tweaks to tanker and loading technologies, overcomes difficulties that limit the use of compressed natural gas.

A big complication is that natural gas is stored under high pressure to reduce its volumes, which leads to problems when it must be delivered for use at lower pressures. As you may remember from physics class, changing the pressure of a liquid changes its temperature. That’s how your refrigerator works: coolant is compressed and decompressed to absorb and release heat as needed.

With natural gas, temperatures can fall to the cryogenic levels, around 238 degrees below zero Fahrenheit, if pressures change too fast – not good.

OsComp claims a technology that they’ve labeled RapidFill, which can handle these temperatures, allowing trailers to be loaded and unloaded quickly enough to be economically feasible to deliver relatively small loads to relatively small customers, as measured by million British thermal units consumed per year, known as MMBTU.

“We are happy to take in customers that are using 10,000 to 15,000 MMBTUs per year,” Santos said, pointing to a high school, dairy farm or a ski resort as typical examples. By contrast, he claimed, current systems don’t make economic sense unless you’re using “more than 100,000” MMBTUs annually.

OsComp claims it has a turnkey system. After a customer signs a one- to four-year contract, they set up the whole system, claiming that with the current price difference between natural gas and fuel oil, there’s a payback time of just a few months due to fuel-cost savings.

Santos said customers can keep their previous boilers, so it’s relatively easy to switch back in case the price of natural gas should soar. And if a natural gas pipeline makes it their way, they’re all set to hook up, and OsComp will move on.

Considering how much disruption has been introduced into the electricity market by cheap natural gas – I hope you’ve read some of my endless stories about alternative-power companies and deregulation – the possibility of increasing access to natural gas for heating and other industrial applications seems intriguing, at the least.

GraniteGeek appears Mondays in The Telegraph. David Brooks can be reached at 594-6531 or dbrooks@nashuatelegraph.com. Also, follow Brooks on Twitter @granitegeek.

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