Harrison Dillon has a wonderful story to tell. I heard it the other day at TEDx Atlanta.

Modeled on the globally famous TED conferences, TEDx Atlanta is an upbeat event where a series of interesting people — achievers in their respective fields — have 18 minutes to give “the speech of your life.” Dillon gave a good one.

As freshmen at Emory University more than 20 years ago, Dillon and Jonathan Wolfson became best buds. A decade or so later, having acquired complementary skills, they founded a biotech company near San Francisco. Dillon is the chief technology officer, Wolfson the CEO. Both are very smart guys.

Their company, Solazyme Inc., uses micro-algae to convert biomass into substitutes for petroleum and other oils. And apparently, Solazyme does this better, or at least as well, as anyone.

Wolfson and Dillon have become darlings of the capital markets. They’ve acquired, at last count, $125 million in venture funding — much of it in the depths of the Great Recession. Among those who are supporting Solazyme either as investors or customers are the soap giant Unilever, the airline mogul Richard Branson and the U.S. Navy.

One of the things that so many big players like about Solazyme is how much progress the company has made in cracking the nut on how to “scale up” production. Because we use so much energy, scaling up production is a core issue for anyone in the business of refining fuel. Dillon spent quite a bit of time talking about that at TEDx.

But Dillon’s core message was more inspirational than simply one aspect of Solazyme’s business strategy. He says his company is about something bigger than just a business. It’s about energy independence. And, although he emphasizes the point a bit less, it’s about reducing greenhouse emissions.

Dillon captured the TEDx Atlanta audience’s imagination. Admiring questions followed: What can we do to help you solve our environmental and energy problems? His answer wasn’t exactly specific: Support “sensible energy policy.”

This is where the skeptical journalist starts to part with the crowd — and, frankly, to feel a bit guilty that in his heart he isn’t riding along on the feel-good TEDx-express.

Do people really think that the interests of a private company, with tens of millions of investor dollars riding on its profitability, are the same as the interests of the country at large? Or of our global future? Or for that matter of the Earth’s environment?

I asked Dillon a question driven by my skepticism. What is the carbon output of Solazyme’s fuel? That, after all, is the bottom line when it comes to climate change.

And Dillon was ready with a pretty good answer: Last year, Solazyme hired a company called Life Cycle Associates to perform a (go figure) “full lifecycle” analysis of greenhouse emissions from the company’s diesel fuel. Soladiesel’s “field to wheels” emissions, Life Cycle reported, are “85 to 93 percent lower than standard petroleum based ultra-low sulfur diesel."

Sounds good, doesn’t it? The problem is that, when you dig into the details, it’s not nearly as good as it sounds. One of those details was pointed out last year by the journalist Katie Fehrenbacher on her GigaOm blog. Fehrenbacher corresponded with a chemical engineer and energy blogger who told her he “doesn’t ‘put any stock at all in life cycle analysis for processes that don’t exist commercially,’ these analyses at pre-commercial stages are often times based on assumptions that can prove to be different at a commercial stage.”

The other problem is even more basic: When it comes to figuring out how much greenhouse gas is emitted by a biofuel, “life cycle” studies can be squishier than the comprehensive-sounding term leads you to believe. That’s because the “field” part of such “field to wheels” studies measures how much carbon is pulled out of the atmosphere by the plant matter, or “feedstock,” that’s used to feed the algae.

It’s a familiar issue to anyone who’s followed the debate over corn-based ethanol’s impact on climate change. In very basic terms, Solazyme, or at least its contractor, is taking credit for the carbon removed from the atmosphere by plants that will be eaten by its algae; then, it's subtracting that number from the actual emissions generated by producing and burning its fuel.

But should Solazyme’s fuel be credited in that way, when its production process is unlocking carbon from plant matter that otherwise might have stored for many years within the biomass? If you didn’t count the carbon that plants would be storing anyway, Solazyme’s greenhouse emissions would likely look a lot worse.

Solazyme’s fuel may in many ways be better for the environment than the alternatives. But the truth is that there’s not one simple way to count greenhouse emissions from algal fuel — just as there isn’t one simple way to produce algal fuel. One method that seems particularly promising: To use sequestered carbon from coal plants, rather than biomass, to feed algae that produces fuel. That at least would have the benefit of intercepting carbon that otherwise would be going straight into the atmosphere — in effect getting more bang for the buck from coal plant emissions and also slowing it down before it finally added to greenhouse effect.

But even reusing sequestered carbon isn’t such an easy call. Wouldn’t it be better to sequester carbon forever rather than to allow it to be emitted after it was used one more time? For that matter, wouldn’t it be better to just leave the coal in the ground in the first place?

My point isn’t just that algal fuel isn’t a silver bullet. More fundamentally, it’s that we should all raise an arched eyebrow when any company tells us they’ve found a path to solving the climate crisis — especially when that path would result in very little fundamental change in our lifestyle and consumption patterns.

Businesses must and will have a big role in addressing the biggest challenge of our age. And businesses have every right, even a responsibility, to look out for their shareholders’ interests. But any one business’ interests aren’t the same as our own.

Ken Edelstein is the editor and publisher of GreenBuildingChronicle.com.