In the past eight years we have been made acutely aware of the importance of energy in economic, environmental, and logistical terms. Gasoline having exceeded $4.50 per gallon, and the awareness that burning of it is contributing to global warming has focused world attention on the issue of finding alternative, cleaner burning, and more efficient fuels. One existing alternative to conventional petroleum products such as gasoline, are fuels like ethanol which can be produced from crops.
Ethanol made from bio-feedstocks is derived from the fermentation of simple and complex sugars extracted from plants. Sugarcane and sugar beets are excellent sources of simple sugars which can be directly fermented. Corn, potatoes, sorghum, and other cereal crops contain more complex forms of sugar called starch which must be converted in to simple sugars through enzyme hydrolysis before they are suitable for fermentation. The fermentation process produces a solution of about 12-13 percent ethanol by volume in water. Water boils at 212 F (100 C) at standard atmospheric pressure while ethanol boils at 172 F (77.7 C). A still is a device which takes advantage of this difference of boiling temperatures to separate ethanol from water.
A still has three basic components, boiler, condenser and distillate collection tank. The boiler is simply a containment vessel in which the water and ethanol mixture (stillage) is heated to a point just above the boiling temperature of ethanol. The result is ethanol vapor which can then be fed into a condenser for liquidation. The condenser is usually a copper tube – the best conductor of heat – which extracts heat from the ethanol and dissipates it into the air or water supplied to enhance cooing; much the same way the radiator in your car cools the engine. Lowering the temperature of the ethanol vapor causes a change of state from gas back into liquid form, and finally the liquid ethanol is collected in the distillate collection tank.
You can build you own small still quite easily. If you only want to distill a few gallons at a time, a pressure cooker makes an excellent boiler, and you can get a twenty-five foot roll of 1/4 inch copper tubing from your local hardware store to make a superb condenser. For the distillate collection tank, you need some type of container which will collect the ethanol and not allow it to escape through evaporation.
Unfortunately, the distillation process is not perfect and a small amount of water will vaporize and be carried along with the ethanol, but by redistilling the output of the still through successive stages an ethanol concentration of about 96 percent can pretty easily be obtained. Of course, all this heating of the stillage requires energy and thus increases the cost of ethanol production. There is how ever another way to distill ethanol that takes advantage of the free energy of the Sun, called a “solar still.”
A solar still is really a pretty simple device consisting of a 4X8 sheet of plywood painted or sealed and covered with a layer of burlap. A wood or metal frame around the perimeter of the plywood supports a sheet of glass. The solar still is then mounted at an appropriate angle to allow sunlight to shine through the glass directly on the burlap, and which will promote the flow of stillage down through the burlap by force of gravity. At the raised end of the panel stillage enters and is dripped onto the burlap. As the stillage runs down the burlap it absorbs heat from the sunlight and when it reaches the boiling temperature of the ethanol, the alcohol evaporates while the water continues to drain down through the burlap. When the ethanol vapor comes in contact with the glass, which is cooler, it condenses on the glass. Gravity causes the ethanol droplets to roll down the glass to its’ lower end, where they are trapped by a drip collector and channeled out of the distillation panel into a distillate collection tank. The left over water is also collected and removed at the bottom of the panel.
So, if you have a few acres of land where you could grow ethanol feedstocks, you have two simple methods to consider in building your own small scale still and producing your own fuel. Now that’s energy independence.
