Category Archives: Biofuel

Powering Flight

The obvious answer to a cleaner and safer future is the abandonment of fossil fuels. For the production of electricity, this is already on the way. Use of coal has been cut in half just since the turn of the century and the trend continues today.

Decarbonizing surface transportation is way behind the curve, but occurring nonetheless. Projections suggest that by 2030, half the new cars on the market will be electric. In the second quarter of 2019, One electric car, the Tesla Model 3, sold more cars in its class than any other. And all the others were gasoline-powered cars.

Stationary power production and surface transportation are easy compared to flight. To practically power aircraft takes an extremely energy-dense fuel. Fossil fuels such as gasoline or jet fuel are 70 to 100 times as energy-dense as the energy stored in a rechargeable Lithium-ion battery.

The only current alternative to liquid fossil fuel is biofuel, ethanol from corn and sugar beets and biodiesel from soybeans. Ethanol makes up a scant two percent of our liquid fuel needs, biodiesel less than that. The figure is even lower than that when you account for the fossil fuel energy inputs to the production of biofuels. We won’t see row crop biofuels making up a larger share of our fuel needs because of the negative environmental impacts and the fact that biofuels production drives up food prices.

Another source of liquid fuel could be waste-to-fuel plants. There are already facilities which burn garbage (solid waste) for the generation of electricity, consuming about fifteen percent of all solid waste. Although this does produce energy and reduce the need for landfills, it doesn’t help with air transportation. There are also concerns about the environmental and health impacts of the combustion products.

Recycling has become difficult recently as China has greatly decreased accepting our wastes. Rather than simply landfilling wastes that can’t be recycled, it is possible to convert the waste to a useful fuel to power aircraft.

Various wastes , even municipal sewage waste, when heated to high temperatures produce a mixture of gasses in a process called destructive distillation. These gasses can be chemically manipulated with catalysts and turned into a liquid hydrocarbon fuel.

A model system for waste to fuel would look something like a plant sited near a current landfill. Municipal solid waste, agricultural wastes, and suburban wastes would all be brought to the processing plant where the materials would be separated . Materials which are unusable would still be landfilled.

The biggest problem with a waste-to-fuel strategy is the resource base. The best way to contain the rising cost of just about anything is to become more efficient. The easiest way to be more efficient is to reduce waste. That means a diminishing resource base. This may not be a business model that many will wish to pursue.

The only long term solution to our energy needs regardless of source or form is to use a lot less and produce what we need sustainably. We have to learn to live within our means.

Dr. Bob Allen is Emeritus Professor of Chemistry at Arkansas Tech University.

Biofuel from Seaweed

A relatively new contender for a source for biofuels, ethanol from seaweed, has come to the fore. Ethanol is blended with gasoline, commonly a ten percent blend in gasoline or less frequently E-85, a blend of eighty-five percent ethanol with fifteen percent gasoline. The latter is used extensively in Brazil. First a little background on making ethanol by traditional means.

The most common method for making fuel ethanol is fermentation of sugar with yeast. The sugar itself can be had directly from sugar cane, sugar beets or various fruit juices or indirectly from any source of starch such as grains or potatoes. Enzymes obtained from malted barley convert the large polymeric starch into small molecules which the yeast can use as a substrate for fermentation. The process has been known for over five thousand years. The oldest evidence of writing is cuneiform tablets found in modern day Iraq, then known as Sumeria. Some of these ancient tablets have records for beer production and distribution.

Virtually all ethanol produced in the United States is derived from corn and that is a problem on several levels. First and foremost is the fact that the process of capturing energy from sunlight is very inefficient compared to solar panels or wind turbines. Large swathes of land must be dedicated to energy production which otherwise would be suitable for food production. Ethanol from corn also consumes large amounts of fresh water and degrades the soil over time.

Ethanol can hypothetically be produced from plant fiber (cellulose) rather than starch, hence waste plant matter such as grass clippings and leaves could be turned into fuel. Although cellulosic ethanol has been studied intensely for decades, no commercial production has yet been achieved.

Now back to ethanol from seaweed. It’s recently been reported that ethanol can be made from seaweed using a genetically engineered bacteria. This is possible because the chemistry of seaweed is fundamentally different from land plants. Seaweed is comprised of large alginate molecules rather than cellulose or starch.

E. Coli, a bacteria common in the intestines of mammals and birds has been modified so that it has the enzymes necessary to disassemble the seaweed. This releases small molecules similar to sugar just as barley malt releases sugar from starch. A second modification of the genes in the bacteria allow metabolic processes that convert the sugar equivalent to ethanol, hence acting like yeast.

There are a number of advantages to the use of seaweed for fuel production. There is no diversion of food crops to fuel production. Seaweed can be harvested as a perennial crop from coastal areas or salt marshes so there is no impact on freshwater or land erosion. Seaweed production could even have a positive effect in certain coastal areas. Fertilizer runoff from the grain belt ends up in the Mississippi and ultimately the Gulf of Mexico. This nutrient-laden water causes unwanted algae blooms which consume oxygen and create a “dead zone.” If seaweed were farmed in this location it could absorb the nutrients for its growth and then be harvested for fuel production- a win-win situation.

Next time you have a little sake (the ethanol portion ) with your sushi (the wrapper part) consider that it could be coming from the same seaweed, all the while cleaning the environment.

Dr. Bob Allen, Ph.D., is Emeritus Professor of Chemistry at Arkansas Tech University