Elsewhere, this blog has noted efforts to generate petroleum using genetically engineered bacteria (Bell BioEnergy, Amyris and LS9). These methods use naturally-occurring abilities of certain bacteria to convert cellulose, a carbohydrate, to hydrocarbons, the chemicals that fuel our vehicles, heat our homes, and otherwise serve most of our energy needs.

Bacteria convert one type of chemical energy to another type, as explained here. Photosynthesizers such as green plants are needed to perform the first step of converting light energy into chemical energy for the bacteria to work on.

What if this middle step were eliminated? A new Bill Gates start-up, Sapphire Energy, begins and ends with the photosynthesizer — in their case, algae, single-celled plant-like organisms. The goal is to create "renewable gasoline," not ethanol, taking advantage of "non-arable land."

Another company, Solazyme, takes a more conservative approach, if anything about this field can be called conservative. It grows its oil-generating algae in the dark and feeds it sugar water, which must be derived from food sources. The fundamental principles are the same as with methods that use bacteria to produce renewable hydrocarbons.

Algae are aquatic organisms that require water to be circulated, a significant energy cost that currently keeps the price of algae-derived fuels high. This factor may limit algae's usefulness on an industrial scale. Algae also need a source of carbon dioxide. These fundamental differences may mean algae will turn out to be inferior to bacteria in the field of renewable fuels.

Or not. There are few certainties yet in this exciting, promising field. There is a lot of potential and a lot of hope, and I will be interested to see whether these new energy companies can bring down the costs enough to produce their products on a meaningful scale and compete with fossil fuels.

Read more at Scientific American.

How does a biotechnology company like the ones described here make petroleum from plants? And what effect will all this new petroleum have on global warming?

All fossil fuels contain energy stored in the form of hydrocarbons. Different hydrocarbons have different uses. Methane, the simplest hydrocarbon, is the main component of natural gas, while various complex hydrocarbons make up petroleum. Gas and petroleum refiners process these hydrocarbons into an array of fuels like gasoline, diesel fuel, and jet fuel.

The hydrocarbon in fossil fuels began as a different type of molecule, carbohydrate. This carbohydrate was produced by plants, then converted by a geological process to hydrocarbon. So far, fossil fuels have been the only game in town for obtaining hydrocarbon. Renewable fuels currently in use, such as ethanol, belong to yet another chemical class and do not have the properties that make hydrocarbon so useful as a fuel source.

Producing renewable hydrocarbon begins with naturally occurring microbes called methanogens. (Technically, methanogens are not bacteria, although they are commonly described as such.) These microbes are found in many environments, including the guts of many animals, such as cattle and humans. Here they are notorious for the gas they produce as they feed on indigestible organic compounds.

These microbes convert one type of organic compound (carbohydrate) to another (hydrocarbon). The chemical pathways to do this are already in place, and through genetic engineering, biotechnologists aim to make organisms that produce different kinds of hydrocarbons which can be refined into fuel.

Plants are mostly made of a type of carbohydrate called cellulose, which is the favorite food of these microbes. This means that almost all plant products, including waste like straw, stover, and sawdust, can theoretically be converted into fuel.

Burning fossil fuels increases the amount of carbon dioxide in the atmosphere because the carbon was stored in the fuel, then released when the fuel is burned. Renewable hydrocarbons, on the other hand, have no net effect on atmospheric carbon dioxide. This is because the plants at the beginning of the cycle made their cellulose out of carbon they removed from the atmosphere. The carbon dioxide released when renewable hydrocarbons burn is equal to the amount that was previously removed by the plant sources. Therefore, these fuels not only have a practically limitless supply, they do not contribute directly to levels of atmospheric carbon dioxide thought to be involved in global warming. Their "carbon footprint" consists only of the carbon released by refining and transporting them. If these processes can be made to take their energy from renewables, the carbon footprint will theoretically be zero.

Bell BioEnergy was previously mentioned here as a start-up whose goal is to produce petroleum from agricultural waste using genetically engineered bacteria. This is a searingly hot technology field, and Bell BioEnergy has competitors: LS9, Inc. and Amyris Biotechnologies.

LS9 claims it will produce gasoline, diesel, and jet fuel from materials such as sugarcane and "cellulosic biomass" (such as sawdust and straw) by feeding them to a "proprietary microbe."¹ A population of this microbe ferments these into oil that can be refined into various types of fuels. About a year ago, LS9 estimated the timeframe to bring these products to market at three to five years.²

Amyris Biotechnologies states that its gasoline and diesel substitutes "will be made from the same feedstocks and production plants that are used to make ethanol."³ In the U.S., that feedstock is corn, while sugar from sugarcane or beets is most prominent in the rest of the world.⁴ Corn and sugar are not nearly as compelling as fuel sources as agricultural waste; nevertheless, the Amyris product will be fully renewable like the others.

The UK's Times Online claims that LS9 is one of "several companies in or near Silicon Valley" to enter the renewable petroleum business;⁵ it may be referring to Amyris, in Emeryville. Silicon Valley seems to be a curious place to find either an agricultural concern or an energy company, although the high technology involved in creating the microbes suits it just fine.

These Silicon Valley companies boast founders with impeccable academic pedigrees and impressive venture capital funding. Contrast that with Bell BioEnergy's roots hawking powdered peanut butter from a Georgia farm. The race to produce the first renewable petroleum-based fuels on an industrial scale promises lots of drama.

Notes

1. LS9, Inc. website.
2. Neil Savage, Technology Review. "Making Gasoline from Bacteria" (August 1, 2007). Massachusetts Institute of Technology.
3. Amyris Biotechnologies website.
4. James Jacobs, Ag Economist. "Ethanol from Sugar" (n.d.). United States Department of Agriculture.
5. Times Online."Scientists find bugs that eat waste and excrete petrol" (June 14, 2008).