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Biology Could Be Used To Turn Sugar Into Diesel
ABCTech has an interesting article about an Emeryville-based tech startup, Amyris Biotechnologies, that is planning to use microbes to turn sugar into diesel. Ethanol is made by adding sugar to yeast, but Amyris believes that it can reprogram the microbes to make something closer to gasoline. The company was initially given a $43 million grant from the Bill and Melinda Gates Foundation to attempt to research the applications of Synthetic Biology for making a cost-effective malaria drug. Jack Newman, the Vice-President of Amyris said, "Why are we making ethanol if we're trying to make a fuel? We should be making something that looks a lot more like gasoline. We should be making something that looks a lot more like diesel. And if you wanted to design, you name it, a jet fuel? We can make that too."
The real challenge is to turn waste cellulose into motor fuel -- be it ethanol or biodiesel.
That's easy: Add xylene. (Either in a batch, or by incubating it with the sort of bacteria that hang out in the guts of termites.)
This cracks the cellulose back into starch.
Cracking starch to sugar is similarly trival. (Either add acid or feed it to certain microbes.)
Once you've got sugar, getting to ethanol is a previously-solved problem (as is getting it to "something more like gasoline or diesel fuel" if the other bioprocesses work out on an industrial scale.)
Of course if you are willing to go with METHanol, just heat the cellulose, in a centuries-old industrial process. (That's why they call it "wood alcohol", after all.)
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Sugar is artificially more expensive. The US government uses tarriffs and subsidies to prop up Florida sugar farmers. In real production costs, sugar is very cheap. Corn syrup is a bit more expensive to make, but the US has huge amounts of corn, but relatively small tropical areas to grow sugar.
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Sugar cane.
Europe has zero tropical areas and still produces plenty of sugar - from sugar beets.
It doesn't really matter all that much what the end product is... ethanol is perfectly fine. The point is one ton of dry woody biomass is about the same as 2 barrels of oil and this if you can convert for free.
Starches are fine to start with, but only a small amount of the plant ends up as starch. An even smaller amount ends up as oils. Celulose, pentosans and lignins compose the majority of plant tissues. There are many fungi which digest these and some can be harnessed to produce alcohols. The issue is we are still stuck with one ton of dry plant matter equals about 2 barrels of oil.
The USA burns about 20 million barrels of oil per day. From a plant source this is 40 million tonnes per day.
A cheaper and more promising way to produce this oil is using the Fischer Tropche process and doing coal->liquids or coal->gas. Note that Alberta Tar Sands operations are essentually bitumin->liquids. Bitumin is a little closer chemically to what we need than coal is... IE both are hydrogen poor in that liquid fuels in the Alkane series (most of what we use) have about a 2:1 ratio of hydrogen to carbon.
Coal depending on the type is about 0.6:1 and bitumin is closer to 1:1.
Methane is 4:1. This means that methane is a good chemical feedstock from which to obtain the hydrogen needed.
This also means it is stupid to be burning methane... it is far more valuable as a chemical feedstock than a fuel.
Plant matter does fit into the equation, it is not as hydrogen poor. Plant matter is basically (CH2O)n and from this we can see that it is a partially oxidized hydrocarbon. This means that plant matter is hydrogen poor unless we can break the H2O bonds and this is the same problem we face with coal and bitumin. Ie... in the case of coal and bitumin, we can break H2O bonds in river water or lake water or ocean water to obtain our hydrogen.
Note that alcohols are also partially oxidized hydrocarbons. Ethanol for instance is C2H5OH. This means it is easier to obtain ethanol from sugar because both the sugar and the ethanol contains Oxygen. The flip side of this is that since the molecule is already partially oxidized, it doesn't contain as much energy as an un-oxydized Alkane such as the ethane (C2H6) parent molecule. Also note that ethane for instance has an atomic weight of 30 while ethanol has an atomic weight of 46. So you have less energy with about 1.5 times the weight.
(BTW - this is the short of why the oil industry is building LNG tankers. Methanol (CH3OH) is safer and easier to transport than CH4 (liquid), but 1/2 the weight of methanol is oxygen).
All this means is there isn't a free lunch. Production of any fuel from a sugar polymer source (dry plant matter) is going to require energy and the only biological source of this energy comes from oxidizing carbon to obtain the energy required to salvage the hydrogen. This results in massive releases of CO2 (of course - its the raw material plants use to create dry matter - hense it is not polution and is in fact fertilizer). Next you lose a significant amount of the total mass of the dry matter we start with. We eventually are left with one ton of dry plant matter is equivalent to 2 barrels of oil - if we can convert it for free.
We are back to needing 40 tonnes of dry plant matter per day and massive factories which don't exist.
In my country in Europe we make sugar out of beets and we even export it and make money off of it. If a 3rd world country like mine can do it, U.S. sure can, so why is it fixated on sugar cane when beets are easy to grow?
d ings/Sugarbeets.htm
I think they produce a beet or two here in the US:
"U.S. farmers produced 33 million tons of sugar beets on 1.6 million acres in 2000, versus 28 million tons of sugar beets on 1.4 million acres in 1990"
http://www.ers.usda.gov/AmberWaves/February05/Fin