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Bring It On

Converging non-food biomass directly into high-octane gasoline. Let's hope they're right.


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mpthompson wrote:

This sounds similar, but is different than what Swift Enterprises are up to with their 100LL Aviation Fuel replacement. Indeed, lets hope both are on to something.

Carl Pham wrote:

Pssht. You don't need to resort to hope. Unlike nanotech artery-cleaning robots, or spray-on cheapie solar cells or microwave power satellites, this stuff is easy. The chemistry is straightforward -- I mean, that's why the oil and coal got formed in the first place, right? The chemical transformation in question is highly favored, under the right conditions -- and the genetic engineering is pretty easy, too.

Once again, it mystifies me why folks in general feel the right approach to solve dependence on mined petroleum is some Space Age wildly difficult tech or hoping for some astounding and unlikely engineering breakthrough in tech that has been well-studied for decades (photovoltaics, hydrogen), when the easy-peasy 21st century approach is staring them in the face.

I mean, what do we have that our 1970s fathers trying to solve the 1970s oil shock didn't have? The answer is not better photovoltaics or fuel cells. To the contrary, the thing we know far more about now than we did then is biotech, in particular how to twitch the genes of organisms to do what we want them to do. This is why diabetics can now inject themself with human insulin manufactured by redesigned bacteria in giant vats in South San Francisco.

Since all we're talking about is modifying an existing natural cycle (CO2 -> plant -> oil -> combustion -> CO2) to suit our needs better (speed up the first two steps), the obvious solution is to start tinkering with living organisms to do just that. Design algae that turn CO2 into natural gas for electric power and heating, or liquid hydrocarbons for transportable fuel. Design other bugs to turn CO2 into solid hydrocarbons or carbonates for CO2 sequestration. The whole thing solar-powered, self-assembled, self-repairing, self-replicating -- just throw them in a big pond and off they go. Why screw around trying to redesign in silicon and metal what nature has been able to do with proteins and DNA for a billion years?

Paul F. Dietz wrote:

This technology, like all biomass energy technologies, suffers from the low efficiency of photosynthesis (algae are more efficient, but having to provide them with a concentrated CO2 stream ruins them as a stand-alone source of non-fossil fuel). It may well be able to substitute for much of the transportation fuel used in the US, but the land required will still be very large, and if adopted on a global scale would have huge impact.

Ultimately biomass has to be viewed as a niche energy provider (or, more accurately, a niche provider of reduced carbon for chemicals and vehicular fuels). The bulk of society's energy use is going to have to come from more concentrated sources.

Carl Pham wrote:

An interesting assertion, Paul. Let's run the numbers:

The United States uses about 29 Quads per year of energy for transportation, which is about 3.07e+19 Joules. Assuming no one can genetically boost the efficiency with which plants turn sunlight into hydrocarbon (unlikely IMHO), we'll use the natural efficiency of photosynthesis of about 7%, so we need 4.39e+20 J of sunlight.

Average insolation in North America is about 3 to 5 kWh/m^2/day. Taking the lower figure, we get about 4.0 GJ/m^2/year, so we need 1.1e+11 m^2 or 110,000 km^2 or 42,000 square miles or 27 million acres of photosynthesizing greenery to supply all of the transportation energy used in the US, without having to significantly change the engines we use, without abandoning our existing liquid-fuel distribution infrastructure, and instantly putting in place a 100% recycling scheme for the CO2 emitted by combustion.

By contrast, US farmers planted about 87 million acres of corn in 2008, roughly three times as much area.

So while it's certainly a substantial area to put under cultivation (about the area of Tennessee), I'm not very convinced the land usage issue is the serious (or even a serious) stumbling block. The major issues would seem much more likely to be (1) appropriate engineering of the plant, and (2) cost-effective harvest, with (2) posing the greater engineering challenge, cf. the usual argument about corn ethanol "costing" more in gasoline than it saves.

In any event, the only two sources of energy more concentrated than sunlight are fossil fuels or uranium. The former are axiomatically that which we're trying to replace, and while I have no objection -- even encourage -- the latter, it can't do anything for our transportation energy needs, in the absence of the McCain Miracle Battery or a willingness of the populace to see baby fission reactors installed in automobiles, so in the context of transportation your last sentence seems a bit unrealistic.

Paul F. Dietz wrote:

The best efficiency ever obtained in an actual farm (a winter wheat field in the northwest US) is ~2%. This is the efficiency at converting sunlight to food energy, so adding in cellulose would make it a bit higher, but 7% is very optimistic. In practice, the photosynthetic efficiency of most plants is even lower, since in intense summer sunlight the efficiency drops off.

As I noted, algae can do better, but the requirement to feed them with concentrated CO2 is very problematic.

Carl Pham wrote:

Even using your efficiency number, Paul, I don't think the land-use problem is going to dominate. You're still talking about an acreage not especially different from any major crop.

I also think you're drastically underestimating the potential in engineering the plant, or bug. Even crude, nongenetic manipulation of crops has doubled yields. Why expect less from a direct rational manipulation of the genes?

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This page contains a single entry by Rand Simberg published on August 20, 2008 10:48 AM.

Cover Up was the previous entry in this blog.

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