The Biofuels vs Fossil Fuels unit has students explore the similarities and differences between fossil fuels and biofuels. In the process, students investigate the carbon-transforming processes of combustion, photosynthesis, fermentation and respiration. They apply their knowledge of these processes to the global carbon cycle to examine how use of fossil fuels and biofuels have different effects on atmospheric carbon dioxide levels and consequently global climate change. Students use their understanding of the global carbon cycle to study the claim that biofuels, such as ethanol made from plant material, can help reduce the rate of increase of atmospheric carbon dioxide. In addition, students examine the environmental impact of biofuels agriculture.

Overall, this unit has three important goals. These focus on: Matter and energy changes associated with the carbon-transforming processes, the effects of the use of fossil fuels and biofuels on the global carbon cycle and global climate change, and a cost/benefit analysis of the production and use of biofuels.

In this flexible lab sequence, students convert cellulosic biomass sources, such as sawdust, straw, or cardboard into sugars and then ethanol. As biomass samples are pretreated, enzymatically digested, and fermented, students use glucose meters and ethanol probes to measure the key products of this chemical conversion. In the process, students can test predictions about which biomass sources and treatment methods will be most effective for producing ethanol.

Cellular Respiration Text, Diagrams, Assessments, and Link to Standards

Two lessons and their associated activities explore cellular respiration and population growth in yeasts. Yeast cells are readily obtained and behave predictably, so they are very appropriate to use in middle school classrooms. In the first lesson, students are introduced to yeast respiration through its role in the production of bread and alcoholic beverages. A discussion of the effects of alcohol on the human body is used both as an attention-getting device, and as a means to convey important information at an impressionable age. In the associated activity, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arise from this activity, in the second lesson students work in small groups as they design and execute their own experiments to determine how environmental factors affect yeast population growth.

Can microbiologists engineer new strains of yeast to produce more biofuel from the same amount of plant biomass? In this GLBRC Data Dive, students learn about how scientists Trey Sato and Audrey Gasch are using directed evolution techniques to create mutant yeast strains that can ferment all of the sugars in plan biomass, not just the glucose. Students analyze a data set from one of the scientist’s fermentation experiments to determine how a new mutant yeast strain performs compared to a standard yeast variety.

This high school-level lab demonstration and inquiry activity introduces students to the process of fermenting cellulosic biomass into ethanol, along with the challenges researchers face in this area. The demonstration uses a Vernier probe or balloons to measure fermentation rates of different feedstocks to begin the discussion of why some carbohydrates are easily fermented by yeast while others are not. Students can design and carry out their own labs to try to improve fermentation rates of various feedstocks. Students are encouraged to think about potential feedstocks and the biochemical processes necessary to convert each type of carbohydrate into fuel.

Learners make kimchee or sauerkraut, which is really just fermented cabbage, in a 2-liter plastic bottle. The fermentation process takes from 3 days to 2 weeks to complete, and learners measure the progress by taking a daily pH (acid level) test. This activity can be used to teach about anaerobic bacteria, acidity, osmosis, concentration, and density. It comes from a printed book that is also available in Spanish, though the Spanish version is not available online.

When selecting alternative fuels, it is important to consider the relative advantages and disadvantages of each. This activity asks students to begin to consider the life cycle energy and carbon dioxide emission costs of gasoline, corn ethanol, and cellulosic ethanol. The various pieces help students trace energy and matter through a complex system and begin to critically analyze graphical comparisons of different fuels.

This mini fermenter can be used to conduct small-scale fermentation investigations or demonstrations similar to research done by GLBRC scientists. The design allows for students to use simple techniques and classroom-grade probes to collect data during fermentation on a range of variables, such as ethanol concentration, CO2 production, temperature and pH. The complete mini fermenter can be built with readily-available supplies for approximately $20 (detailed supplies list included with instructions).

This activity allows students to compare the net energy and/or net greenhouse gases (GHG) emitted during the life cycle production of ethanol from switchgrass, diverse prairie and corn stover. Using Microsoft Excel spreadsheets, students model a range of scenarios, starting with data and assumptions provided in the package. This is a flexible quantitative model with many opportunities for modifications depending on the abilities and interests of the students.

"Which came first—the engineer or the scientist? Scientists find out why things happen. Engineers solve problems to make particular things happen." In this story, students learn about the interplay between science and engineering in fermentation research—from the discovery of pasteurization in the 1800s to current efforts to produce efficient biofuels with biotechnology. Research stories give students a window into the work of professional scientists and engineers. This allows students to see how the processes of school science are reflected in the real world while building literacy skills with science-specific content. This research story can be used in conjunction with GLBRC fermentation activities, such as Fermentation in a Bag, Fermentation Challenge, and CB2E: Converting Cellulosic Biomass to Ethanol.

Students are presented with information that will allow them to recognize that yeasts are unicellular organisms that are useful to humans. In fact, their usefulness is derived from the contrast between the way yeast cells and human cells respire. Specifically, while animal cells derive energy from the combination of oxygen and glucose and produce water and carbon dioxide as by-products, yeasts respire without oxygen. Instead, yeasts break glucose down and produce alcohol and carbon dioxide as their by-products. The lesson is also intended to provoke questions from students about the effects of alcohol on the human body, to which the teacher can provide objective answers.