As oil prices rise and global warming becomes a hot topic in the mainstream press, public interest in alternative fuels grows. However, there is a lot of confusion among laypeople about the different types of alternative fuels. Biodiesel, green crude, hydrocracking — what’s it all mean? Can’t we just pour vegetable oil in our gas tanks? Some of these products are difficult to understand without a degree in chemistry. I am not a scientist, and I hope with this glossary to explain the different types of alternative fuels to my fellow non-scientists.

A major point to understand is that there are two purposes for fuel. The first is fuel for energy needs other than transportation- home heating and cooling, electricity, manufacturing. These needs are in some ways more easily met, because the fuel itself doesn’t need to be portable. Solar, wind, geothermal, hydroelectricity, coal, petroleum, and natural gas are fuels currently being used for non-transport needs.

The other purpose is of course transportation, for which we use gasoline, diesel, and jet fuel.

First I’m going to talk about non-portable fuels.

Solar

The energy of the sun is 100% renewable, not ownable by any one country or corporation, available all over the world, and harmless to harvest. The only drawbacks to solar energy is that harvesting it requires a large capital investment in solar panels, and that solar energy is so far not useful for transportation fuel.

Solar panels are made up of photovoltaic cells. These cells use diodes to separate electrons from photons, and that separation generates electricity. The solar panel then stores the electricity. Solar panels are excellent for non-transportation fuel use. In the past a large number of photovoltaic cells were needed to generate a small amount of electricity, but the technology has obeyed the “make it small” maxim of the last decade and gotten thinner and more efficient. Germany has utilized solar electricity to great effect, offering incentives to consumers and manufacturers. It is now one of the largest users and producers of solar panels- all this despite being a country notorious for its bad weather. Imagine how well the US, with its large areas of temperate or desert climates, could use solar energy.

Recent legislation, including the Wall Street bailout bill, have increased incentives for individuals to start using solar panels at home. A homeowner can now get a tax rebate of up to one third the price of their new solar system. These tax incentives will help an already-growing industry. Some companies that are making solar systems are Q-Cells, Nanosolar, and SunPower. The more solar energy is utilzed, the less we will need fossil fuels for generating electricity.

Wind

Wind power is another energy source that is renewable, not ownable, and almost harmless to harvest. It is not quite as universally available as solar, though, and a big objection to it is the “not in my back yard” ugliness and space sucking of wind farms.

Windmills are a very old form of energy harvesting, having been in use since the 1400s. Wind turns the turbine, which creates electricity, which is then stored. Wind farms are common in several states with large expanses of open land. Unfortunately federal legislation has hampered the development of wind power to some extent by requiring extensive environmental impact reports, and by not providing the same tax credits and incentives that the ethanol and oil industries have enjoyed. Like solar, wind energy can only be utilized with a large capital investment, so without tax incentives it has been difficult for the wind industry to build momentum.

Geothermal

Geothermal energy uses water made into steam by the heat of the earth’s core. Geothermal energy is renewable and very clean. Unlike wind or sun energy, though, it is ownable because it can only be accessed by drilling deep wells to access the heat inside the earth.

Geothermal energy is primarily in use in the western US, especially Alaska. These states have more readily available sources of earth-heated water.

Geothermal energy requires a large capital investment, but is very efficient once developed. The US Department of Energy has a geothermal energy program as part of its Energy Efficiency and Renewable Energy department, which works in partnership with private industry to develop energy resources. Geothermal technology is still evolving, and in the coming years we may see it get even more efficient as the ability to extract heat directly from the earth’s magma develops.

Hydroelectricity

As the name implies, hydroelectricity is power generate by moving water. A dam holds the water of a river back, and slowly releases it through a turbine. The technology is relatively simple, and is widely used in areas with both high precipitation and natural landforms that allow for water pressure to build behind the dam. This form of electricity is very clean emissions-wise, but very damaging to the water systems the dams are built on. For example, the Hoover Dam dried up the once-mighty Colorado river, which had flowed all the way to the Gulf of California. Hydroelectricity is therefore controversial- while it is much cleaner than other sources of energy, it is derided by environmentalists and conservationalists.

Now we move on to the much more difficult energy problem: transport fuels. There have been different approaches to this issue: creating new, renewable, clean-burning fuels that are chemically unlike existing fuels (vegetable oil diesel and pure ethanol being examples), or creating fuels very similar chemically to existing fuels using renewable sources and without the negative side effects of petroleum-based fuels (such as biodiesel).

It’s become apparent that to significantly dent our reliance on petroleum, we will need fuels that mimic gasoline, diesel, and jet fuel as closely as possible in terms of performance, availability, and engine requirements. If consumers and industries have to buy new engines or convert their old engines, they won’t switch over until it’s absolutely necessary. If they have to go to special fueling stations, or find fuel themselves, they won’t switch. Furthermore, something like jet fuel has very stringent specifications for freezing point, vapor point, and density.

So let’s go over the options.

Ethanol

Ethanol is alcohol. It is the same stuff that gets us drunk. In fuel form, it is denatured (basically made unpotable). It, like gasoline, is flammable and explosive. It produces less ozone than pure gasoline, but the same amount of other greenhouse gases as gasoline- so switching to ethanol would not reduce our global warming problem by very much at all. Ethanol is not being used by itself as a fuel, but is being mixed with gasoline in many places. E85 is 85% gasoline, 15% ethanol. Gasahol is 90% gas, 10% ethanol.

There are a number of methods (straight fermentation, cellulosic) and feedstocks (corn, sugarcane, switchgrass) for producing ethanol. It would require a whole article to explain these methods, so I will save that for another time. All of these methods require significant amounts of energy (currently petroleum energy) to produce, granting ethanol an unfavorable EROEI (energy returned on energy invested) ratio. One major problem with corn ethanol, which the US government has been backing, is that corn does not have much sugar in it, so to get enough sugar to make ethanol, a lot of waste is produced. Cellulosic ethanol begins to address this issue, but it is still in development, and the EROEI will still not be terribly favorable once cellulosic methods are viable.

Corn and sugarcane ethanol also bring with them the problem of using food as fuel in a world where people are starving. Switchgrass is inedible, but an acre of switchgrass is an acre that’s not being used for food. The corn ethanol industry has already had a real impact on the price of food in countries where corn is the primary staple, such as Mexico. If corn were our main source of fuel in the US, millions, perhaps billions, of people would have to find a new staple food.

All of this adds up to a losing bet, which is unfortunate because the US has poured millions into ethanol in the form of subsidies and minimum percentage requirements.

Biodiesel

Biodiesel is diesel fuel made by separating glycerin out of vegetable oil using transesterification. Biodiesel has a specific, legally defined chemical makeup, which is not to be confused with green diesel or raw vegetable oil (RVO) fuel. Soybean oil is a common source of biodiesel.

Biodiesel is already being sold at some fueling stations. Gas stations in Oregon have biodiesel pumps. It works in any diesel engine, and it has lower emissions than petrodiesel. It biodegrades, and is almost totally nontoxic. It is also much more energy efficient than ethanol, having a much better EROEI. Sounds dreamy right? Unfortunately, there are some drawbacks.

Biodiesel freezes at a much higher temperature than petrodiesel, making it useless for transport in very cold weather- like anything lower than 23 degrees Fahrenheit. So it can’t be used in its pure form for trucking in the winter in most parts of the US, and of course trucking is the biggest use of diesel.

The other big disadvantage is that food crops are needed to make biodiesel. Unlike cellulosic ethanol, which can be made with the inedible parts of plants, biodiesel must be made from food people could otherwise eat. This problem with food vs fuel has been well publicized, and it is a serious moral dilemma that the Western world is finally having to face.

Raw Vegetable Oil

This is when you take filtered vegetable oil like the kind you can buy in a store and use it to fuel a diesel engine. The engine has to be modified first (directions are available online). Emissions are significant, but no worse than petrodiesel. This is a great option for people who have a diesel engine, the technical know-how to convert their engine and keep it running, and a cheap or free source of vegetable oil. Some cities, such as Half Moon Bay, California, have co-ops that work to convert cars and source vegetable oil.

Green Diesel

Green diesel is diesel made from vegetable or animal oils using a process called hydrocracking. Basically the oil is heated in the presence of another chemical. This separates the glycerin from the fat. This process produces a diesel with a much lower freezing point than biodiesel. In fact, the freezing point is so low that energy company Neste is beginning to test it for jet fuel.

However, the ol’ food vs fuel debate is still a huge problem for green diesel.

Proprietary Strain Fermentation

This is a process currently being developed by three Bay Area companies- Amyris (full disclosure: they are my employers), LS9, and JBEI. These companies are competing to breed a microbe that will eat feedstock and produce fuels comparable to jet and diesel. None of these companies yet had products on the market. Their goals are to make fuel cheaper, more plentiful, with fewer emissions, and with less impact on the food market. It remains to be seen if they will succeed.

For insightful, objective analysis of the energy industry, I encourage you to check out Robert Rapier’s i-r-squared.blogspot.com.

Further Reading:

solarpanelinfo.com

awea.org

http://www1.eere.energy.gov/geothermal/index.html

http://www.epa.gov/cleanenergy/energy-and-you/affect/hydro.html

www.oaklandtribune.com

www.journeytoforever.org

www.biodiesel.org

www.i-r-squared.blogspot.com