Test

The following guest essay is by Frank Weigert, who is a retired DuPont chemist.

1) Biofuel Definitions.

Non-chemists all too often get confused by the differences in chemical nomenclature and more conventional terms. Oil as an ingredient in salad dressing is not the same as oil as a synonym for petroleum.

Green plants make nucleic acids, proteins, hydrocarbons, carbohydrates, and lipids. Only the latter three need concern us as fuel precursors. Hydrocarbons have only carbon and hydrogen in their structure. Examples include natural rubber and other materials made from isoprene oligomerization.

Carbohydrates have formulas around (CH2O)n: Carbo (C) - hydrates (H2O). Glucose, C6H1206, is a monomer. Sucrose is made from glucose and another sugar fructose with the loss of one water molecule. Both sugars are soluble in water. Polysaccharides such as starch and cellulose are insoluble in water. Yeasts ferment soluble sugars to ethanol, an alcohol. The technology to ferment insoluble carbohydrate polymers practically does not yet exist.

Lipids are esters of the alcohol glycerin and long-chain fatty acids. Transesterification with a short chain alcohols such as methanol or ethanol converts these lipids to glycerine and esters generically known as biodiesel. Biodiesel is not a hydrocarbon.

Hydrocarbon reactions are generally many orders of magnitude faster than the reactions of polar molecules such as those involving alcohols or esters. That means that the equipment required to reform hydrocarbons is much smaller than that required to ferment carbohydrates to ethanol or transesterify lipids to biodiesel. Hydrocarbon chemistry does not require a solvent. Fermentation must be carried out in water, and yeast generally can only produce an ethanol concentration of 10% or so. The ethanol must then be separated from a large excess of water. Transesterification to make biodiesel is an equilibrium process that will not go to completion without a large excess of the small chain alcohol. That means large equipment for separation and recycle. While a hundred or so refineries provide all the transportation fuel America uses, many thousand fermentation or biodiesel facilities would be needed to produce the same amount of fuel.

The new investment required to convert from a hydrocarbon economy to one involving either ethanol or biodiesel is going to be very high. Why bother? Use hydrocarbons. Hydrocarbons such as gasoline or diesel are global warming neutral if produced entirely from biological materials.

**********************************************

2) What defines a Climate Change / Hubbert’s Peak solution.

Four precepts should guide our work in solving the world’s Climate Change and Hubert’s Peak problems.

a) These are world problems. An expensive solution that works for the United States but not for China, India or Kenya is not a valid solution. America might be the Saudi Arabia of coal, but coal is not a solution for the Hubbert’s Peak problem because it exacerbates the climate change problem. Where is China going to get the land to grow corn to make ethanol? Solutions that depend on local conditions such as desert sunlight or constant high winds are not solutions to the global problem. Venture capitalists who want to get rich selling high investment solutions are part of the problem.

b) Consumers should not have to change anything.

The precept needs to be considered separately for electricity and transportation fuels.

Electricity is easy. Consumers don't care whether the electrons that power their lights, televisions or computers come from falling water, burning coal, or splitting atoms. An electron is an electron.

Transportation fuels are harder. Hybrid cars like the Prius come closest to meeting the criterion. Consumers fill up their gas tank and don't have to worry about the battery until it wears out. The cost of the replacement battery has not sunk in yet. A typical battery pack costs $5000 and will last five years. Thus during the life of the electric car, owners will have to pay $10,000 to replace their battery twice. You can buy a lot of expensive gasoline for that amount of money.

Plug-in hybrids WOULD be different. Suppose you live in an apartment and park 100 feet away. That's an awfully long extension cord. A better option is to continue making gasoline and diesel, only from renewable resources. Cars powered by fuel cells or hydrogen are even more far out. People like personal transportation. Walking is not a solution. Shutting down the airline industry is not a solution.

c) Use existing investment when at all possible and minimize the need for new investment.

This is where most of the pundits get it wrong. Venture capitalists love high investment projects because they earn their fees as a percentage of the capital required. The November cover story of Scientific American is about sustainable fuels. It limits the discussion to Big Physics projects. Only toward the end do the authors offer an estimate of the capital investment required: $100 TRILLION. Ain't gonna happen. Many of the proposed remediation projects are also horribly capital intensive and will never fly.

Many physics solutions claim they will be competitive with oil “soon.” But oil at what price? In the Middle East, countries can pump oil to the surface for a COST $5 a barrel. Americans VALUED that oil at $150 a barrel in 2008. Europeans and Japanese are willing to pay twice that, including taxes. So what is the free-market PRICE of oil? OPEC can set it anywhere within that range. If photovoltaics become competitive with oil at $100 a barrel, OPEC can lower the price to $90 a barrel until the venture capitalists give up. They then buy up the investment for pennies on the dollar, destroy it, and raise the price again. I don't see any way to compete with $5 a barrel Middle East oil. I would be hopeful that biofuels could compete with $25 or $30 a barrel oil.

d) Biofuels should not compete with food production or cause land use issues.

**********************************************

3) The algae Botryococcus braunii can potentially meet all my criteria for a solution to the Climate Change / Hubbert’s Peak problem.

Nobel Prize winner Melvin Calvin discovered a shrub growing in the Brazilian rain forest related to rubber tree in the 1970s. When tapped, this shrub exuded a latex. Calvin collected the material, (a mix of isoprene trimers) broke the emulsion, dried the organic layer, poured it into the fuel tank of a diesel powered car and drove off. No refining necessary! He correctly realized there was not enough land in the Brazilian rain forest to grow this crop. Genetic engineering did not exist back then.

Calvin made a bad mistake when he attempted to breed a modification that would grow in the desert. Making hydrocarbons needs more water than making carbohydrates. He should have been experimenting in a swamp.

Later, Calvin found the pelagic algae genus Botryococcus and studied the hydrocarbons they produce.

A summary of his work is available online, but cannot be accessed directly. You have to link through a bridge site. Here is it's URL.


http://www.osti.gov/bridge/product.biblio.jsp?osti_id=7286

Click on the 1 MB PDF file icon. The discussion of algae begins on page 15.

Calvin reports that 86% of the dry weight of the algae is hydrocarbons, isoprene oligomers averaging n = 6 degree of polymerization. The structures include linear oligomers and cyclic structures related to steroids. They are not directly useable as transportation fuels.

The algae Botryococcus is among the slower growing breeds. It has a reported doubling time of two days. Presumably, producing hydrocarbons is harder than producing carbohydrates. Nevertheless, it is an interesting exercise in powers of 2 to calculate how quickly 1 g of algae can turn into the 100 million barrels of oil needed each day. Once you have the ocean surface carpeted with the algae, you can then harvest half the crop every doubling period in a self-sustaining manner.

One of your discussions laments the fact that useful algae cannot generally compete with trash species. True, but farmers have learned how to grow crops and eliminate weeds. Farmers of the ocean will have the same incentives. Agricultural chemical companies have been very successful at finding selective herbicides for important crops. If growing algae becomes important, they will attack this problem as well.

Another possibility is to begin with an invasive species and modify it genetically to produce the hydrocarbons we want. Caulerpa taxifolia is an algae that escaped from a Monaco aquarium and now carpets the northern edge of the Mediterranean sea. When it also got loose from the Monterrey aquarium outside San Francisco, the U.S. government spent $8 million chlorinating the Pacific Ocean to eliminate the infestation. While it doesn't make useful hydrocarbons, it does make a toxin caulerpenyne, which presumably is the secret to it success. The structure is available in Wikipedia. As the name suggests, it includes both double and triple bonds. It also has 2 acetates which according to biochemical studies are added last. The main chain contains 15 carbon atoms arranged in a way that suggests derivation from an isoprene trimer. Inhibit the acetylation steps and you have a precursor to diesel fuel. Adding the gene sequence to produce the hydrocarbons or disabling the genes that acetylate the product and you have another way to get at hydrocarbons from algae.

I believe conventional oil refineries could process this hydrocarbon mix to produce gasoline and diesel. Refineries could shut down much of their catalyst guard investment because these hydrocarbons have no nitrogen, sulfur, phosphorus, metals, or ash. This is an extremely sweet crude. These hydrocarbons should be able to replace coal as a fuel in electricity generating plants. Similarly, because it is a high quality fuel, much of the pollution abatement equipment at the back end could be shut down.

Check out the MIT Website Whatmatters for more details The URL is:

http://alum.mit.edu/news/WhatMatters/Archive/200111/