Biofuel production
Biomass Vocabulary
Bioenergy: The energy of living things; energy that is obtained from biofuel
Biofuel: Any fuel obtained from biomass
Biogas: Biofuel in the form of a gas. Biogas can be produced from materials such as
wood, sewage, or waste.
Biomass: Plants, animal wastes, and all other forms of matter that come from living
things which can be burned to release energy
Combustion: The process of burning. Combustion produces energy in the form of
heat and light
Digester: A tank in which organic wastes are stored to produce methane
Fermentation: The conversion of sugar to alcohol by the addition of yeast
Fossil fuels: Fuel formed over millions of years by buried plant and animal remains.
As the remains are buried deeper over time, heat and pressure transform them into
fossil fuel such as coal, oil, and natural gas
Gasification: Producing biogas by heating wood under pressure
Gasohol: A mixture of gasoline and alcohol
Methane: Natural gas - A flammable gas produced by the decaying of organic matter
Organic: Derived from living matter, whether plant or animal
Background Information
Combustible materials are used to produce energy in several different ways. Combustion is
used to produce heat, either for direct use in homes or businesses, or to transform water into steam
to run steam powered generators. Combustion of fossil fuels provides the US with about 90 percent
of its energy needs. However, fossil fuels are nonrenewable energy sources, which require millions of
years to form. Combustion of biomass is one of the oldest methods used to produce energy. Wood is
the primary form of biomass used. Other forms of combustible biomass include corn husks, fibers of
sugar cane, sunflowers, seaweed, and dried animal waste.
Biogas is another combustible biofuel which is often produced in a system called a biogas
digester. A biogas digester is a sealed tank into which organic materials (such as sewage or animal
waste) are added. Bacteria inside the tank feed off the decaying organic materials, and produce
biogas. This gas is collected from the digester, and is burned to produce energy. The primary
advantage to using biomass as and energy source is that it is renewable. Biomass fuels can be
continually produced or grown for more energy.
Lesson - Model of a Biogas Digester
Focus: Biomass and biofuels as renewable energy resources
Objective:
• Students will gain understanding of what biofuels are and how they are
used to produce energy
• Students will build a model of a biogas digester
Teaching the lesson:
A. Introduction
• The teacher should review what renewable and non-renewable resources
are, and then go over background information with students
• The teacher will explain to students that they will construct models of
biogas digesters, which will use sugar as the organic matter (it is
produced by the sugar cane plant), yeast will serve in the place of bacteria
to break down the organic matter, a plastic bottle will serve as the storage
tank, and a balloon will serve as the biogas storage container.
B. Materials
* 2 tablespoons of dried yeast
* 2 tablespoons of sugar
* a balloon
* a small plastic soda bottle
* a plastic thermometer
*some warm water
C. Instructions
• Pour the dried yeast and the sugar into the plastic bottle
• Add the warm water
• Measure the temperature of the water with the thermometer and record it
• Cover the top of the bottle with its cap, and shake it as hard as you can
• Remove the cap and place the empty balloon over the bottle's opening
• Allow the system to sit undisturbed for around an hour
• Make observations
D. Evaluation
A biogas digester is very much like the digester produced in this lesson.
Organic materials are the source of food for anaerobic (non-oxygen requiring)
microorganisms which give off a gas in the process. In a true biogas digester,
waste materials are added to the digester, which contains bacteria, and a
biogas called methane is produced. The gas, methane, is burned to release
energy. In the model digester, sugar is added to the bottle, which contains
yeast, and a gas called carbon dioxide is produced. This gas is not
combustible, however.
E. Closure
• At what temperature was the greatest amount of gas produced, or at
what temperature did the balloon fill the most?
• Was the amount of gas produced the same for all temperatures?
• Do you think that the yeast produce more gas at certain temperatures
compared to others?
Credit: The Elm Fork Education Center, the Texas State Energy Office
Renewable Resources and Sustainability Program, and Jessica White