Bell Ringer

Instructions: Select one of the Bell Ringers for students to reflect on and answer.

Vocabulary

Instructions: Go over important terms and their definitions before watching the Science of Biofuels video. The student vocabulary list can be found in the Student Guide and Science of Biofuels – Starter Pack.

Quiz

Instructions: Review key concepts after watching the Science of Biofuels video. The Student Guide and Science of Biofuels – Starter Pack contain the quiz and cloze notes.
Answer Key: Q1:B Q2:D Q3:B Q4:C

Reading and Extended Reading

Instructions: Provide students with the Science of Biofuels – Reading or Extended Reading info sheet for an in-depth exploration of the topic.

Reading Answer Key:

1. Biomass is made from plants or animals, such as wood, crops, or manure.
2. Ethanol and biodiesel.
3. Corn.
4. Vegetable oil, animal fat, or used cooking oil.
5. For cooking and heating.
6. Because it can cause breathing problems and make people sick.
7. To use less gasoline while still working in regular engines.
8. It means the fuel has less energy, so vehicles need more of it to go the same distance.
9. Because it reduces the amount of corn available for food, which can make prices go up.
10. It reduces waste and avoids using land and resources that could grow food.
11. Yes, because biofuels can release fewer harmful gases than regular fuels if made the right way.
12. It could cause deforestation, harm animals, and release carbon stored in the trees.
13. Because these materials don’t compete with food crops and can cause less harm to the environment.
14. No, because it would use more energy than it produces.
15. Biofuels can reduce emissions if made from waste, but they can cause pollution or land damage if made carelessly.

Extended Reading Answer Key:

1. Biomass is organic material from plants or animals that can be used as fuel.
2. Ethanol and biodiesel.
3. By fermenting sugars from crops such as corn or sugarcane.
4. Wood and wood waste.
5. To break down organic material without oxygen, producing methane gas that can be used as fuel.
6. Because it reduces the use of petroleum and works in most engines without modifications.
7. It refers to how much energy is stored in a given volume of fuel.
8. Because they can be made from plants, which absorb carbon dioxide as they grow and are more widely available than fossil fuels.
9. Indoor air pollution, which can cause respiratory illnesses.
10. It reduces competition with food production and lowers the environmental impact of land use change.
11. Cellulosic ethanol production, using fibrous crop residues.
12. It may decrease, since ethanol has lower energy density and provides less energy per gallon.
13. It releases stored carbon, destroys habitats, and offsets the emissions savings from using biofuels.
14. Nutrient pollution from fertilizer runoff, which can contaminate water and harm ecosystems.
15. Because many people in rural or low-income regions burn biomass in open fires or simple stoves without proper ventilation.
16. Algae does not require farmland, grows quickly, and can produce high oil yields with less competition for food resources.
17. Cellulosic ethanol, because it typically has a lower environmental impact and does not compete with food crops.
18. If land is used to grow crops like corn for fuel rather than food, the available food supply can decrease, which can drive up prices.
19. Benefits include local energy production and reduced fuel imports. Risks include deforestation, habitat loss, and indoor air pollution if burned inefficiently.
20. By using waste materials or algae, improving energy efficiency, and lowering the cost and energy required for production.

Computation

Instructions: Provide students with the Science of Biofuels – Computation activity for math integration and practice.
Answer Key:
Q1: (1) Calculate the land required by the traditional process: 0.045 acres/gallon x 10,000 gallons = 450 acres
(2) Calculate the land required by the new process: 0.038 acres per gallon x 10,000 gallons = 380 acres
(3) Calculate the difference in land use: 450 acres – 380 acres = 70 acres
Answer: The facility would save 70 acres of land by using the new process instead of the traditional one.
Q2: (1) Convert current water usage to liters: 8,500,000 cubic meters x 1,000 = 8,500,000,000 liters.
(2) Calculate water savings: 8,500,000,000 x 0.25 = 2,125,000,000 liters.
Answer: By converting to switchgrass, they would save 2.125 billion liters of water annually.
Q3: (1) Calculate the total biomass harvested: 15 acres x 5 tons per acre = 75 tons of biomass
(2) Calculate the total gallons of ethanol produced: 75 tons x 80 gallons per ton = 6,000 gallons of ethanol
(3) Calculate the total BTUs produced: 6,000 gallons x 76,330 BTUs per gallon = 457,980,000 BTUs
Answer: The total BTUs of energy that can be produced from this harvest is 457,980,000 BTUs.
Q4: (1) Calculate that total energy content of the desired petroleum diesel: 100,000 gallons x 138,000 BTUs per gallon = 13,800,000,000 BTUs
(2) Determine the total gallons of switchgrass biofuel needed: 13,800,000,000 BTUs (target energy) / 76,330 BTUs/gallon = approximately 180,794 gallons of switchgrass ethanol
(3) Calculate the tons of switchgrass biomass needed: 180,794 gallons (biofuel needed) / 80 gallons per ton = approximately 2,260 tons of switchgrass biomass
(4) Calculate the acres of switchgrass needed: 2,260 tons (biomass needed) / 5 tons per acre = approximately 452 acres
Answer: Approximately 452 acres of switchgrass would be needed to match the energy content of 100,000 gallons of petroleum diesel

Data Set

Instructions: Provide students with the Science of Biofuels – Data Set for data literacy and analysis practice.

Source: Our World In Data

Data Table

Answer Key: Question 1: Answers will vary. (Example: Both the United States and Brazil have large agricultural industries that make biofuel production easier. The U.S. grows a lot of corn, and Brazil grows a lot of sugarcane, which are very efficient crops for making ethanol. Both countries also have policies that encourage research into the production of biofuels and promote biofuels as a way to lower carbon emissions. Economically, biofuels also provide jobs in farming and energy production.)
Question 2: Answers will vary. (Example: Indonesia’s biofuel production may have grown more quickly because its government placed a stronger focus on developing this energy source. China, on the other hand, may have decided to invest more heavily in other energy sources instead. Also, Indonesia may have more flexibility to use land and resources for producing biofuels.)
Question 3: Answers will vary. (Example: China and India both have to focus on providing reliable energy for and providing food for their very large populations. Using farmland to grow crops for fuel might take away from food production, so they may not want to rely heavily on biofuels. They also may have limited resources like water and arable land, and have focused on other types of energy that are better long-term options.)
Question 4: Answers will vary.
Question 5: Answers will vary. 

Fermentation and Biofuels Lab

Instructions: Use the Fermentation and Biofuels Lab – Student Handout and the following Teacher Guide to conduct the lab activity.

Introduction

This lab introduces students to fermentation – the biological process that produces ethanol fuel. Using yeast and sugar or corn syrup, students will model the production of bioethanol, observe CO₂ release, and connect the results to real-world biofuel systems. 

Student Objectives

Students will be able to

• Model ethanol fermentation by observing yeast converting sugars into CO₂ and ethanol.
• Collect and graph CO₂ production data from a single setup.
• Connect results to real-world bioethanol systems and their tradeoffs.

Background and Context

Ethanol is one of the most widely used biofuels in the world and is produced from plant-based sources. In Brazil, ethanol production relies heavily on sugarcane, which is particularly efficient because sugarcane contains high concentrations of sucrose that can be easily fermented. In contrast, the United States primarily uses corn as its main feedstock for ethanol production, since corn is widely grown and heavily subsidized. Beyond these first-generation biofuels, researchers are actively developing cellulosic biofuels that come from plant residues, grasses, and other non-food biomass. These so-called second-generation biofuels have the potential to reduce some of the concerns tied to traditional ethanol production by making use of materials that are not part of the human food chain.

The fundamental chemical process underlying ethanol production is fermentation, during which microorganisms such as yeast convert glucose (C₆H₁₂O₆) into ethanol (C₂H₅OH) and carbon dioxide (CO₂). The balanced chemical equation for this reaction is: 

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.

In this process, a single molecule of glucose is broken down to form two molecules of ethanol and two molecules of carbon dioxide, releasing energy that the yeast uses to sustain its metabolism.

Despite its benefits as an energy source, the use of ethanol as a biofuel raises important social, environmental, and technological questions. One of the most significant issues is the “food vs. fuel” debate, which highlights the concern that growing crops for fuel might compete with growing food for human consumption, potentially raising food prices and impacting food security. Land use is another major issue, as expanding biofuel production may lead to deforestation, habitat fragmentation, and biodiversity loss, increase water and fertilizer demand, and—through indirect land-use change—potentially undermine some of the greenhouse-gas benefits biofuels are intended to provide.

Materials

• Student Handout

Per group:

• 1 packet of dry yeast
  Note: One packet of dry yeast is equivalent to 2 tsp.
• Feedstocks: 2 tbsp of sugar OR 2 tbsp of corn syrup
• 1 cup of warm water: ~40°C or 100°F (1 cup per trial)
• 1 500 mL clear plastic bottle or glass beaker
• 1 balloon
• Funnel
• Stopwatch or timer
• Flexible measuring tape or string and ruler
• Safety goggles and gloves
• Graph paper or digital graphing tool

Optional for ethanol detection (teacher demonstration; recommended for safety)

• Iodoform test reagents (iodine solution, sodium hydroxide) in small amounts
• Heat source (warm water bath)

Procedure:

1. Students will follow the directions in the Student Handout to set up and conduct the experiment, recording observations and collecting data. They will also make a graph to display their results and answer conclusion questions to analyze and reflect on experiment results and make connections to real-world bioethanol production systems.
2. Optional Extension: Once students are completed with their tests, the teacher may perform an iodoform test on samples. 
   • Add a few drops of iodine solution and sodium hydroxide to fermented liquid. 
   • Heat gently in a water bath. 
   • A yellow precipitate (iodoform) indicates ethanol presence. 

Assessment Rubric

Answer Key

The Student Guide contains the Fermentation and Biofuels Lab – Student questions.

Analysis Questions Answer Key

1. Answers will vary. (Example: The graph rose quickly at first, and then started to flatten. From 0-15 minutes, the slope was steep. After 15 minutes, it increased more slowly, showing a plateau as fermentation slowed.)
2. Answers will vary. (Sample response: First 15 minutes – from 5 cm to 11.5 cm = 6.5 cm over 15 minutes = 0.43 cm/min. Second 15 minutes – from 11.5 cm to 12.9 cm = 1.4 cm over 15 minutes = 0.09 cm/min. Fermentation is fastest early on and slows later as sugar is used up.)
3. Answers will vary. (Sample response: Final diameter 12.9 cm / 2 = Radius 6.45 cm. 4/3 x 3.14 x 6.45³ = approximately 1,124 cm³ (1.12 liters of gas).
4. Answers will vary. (Example: Our data was mostly consistent. Possible errors include: the balloon not being perfectly spherical, stretching the balloon while measuring, small leaks around the bottle neck, and reading diameter at slightly different angles each time.)
5. Answers will vary. (Sample response: Yes, I predicted 12 cm in 30 minutes, and we measured 12.9 cm. It wasn’t exact, but very close.)
6. Answers will vary. (Sample response: I would keep the yeast-sugar mixture at a steady warm temperature (around 40 degrees Celsius) by placing the bottle in a warm water bath. That should speed up the yeast activity from the start, and increase the rate of CO² production.)
7. Answers will vary. (Example: It’s the same core biology – yeast converts sugars to ethanol and CO₂. Industry just does it in large, controlled fermenters with strict temperature control, mixing, and sterile conditions, then distills the ethanol to high purity and handles the CO₂ byproduct.)
8. Answers will vary. (Example: Challenges include getting enough reliable feedstock, land and water use, maintaining sterile conditions at huge volumes, preventing contamination, supplying nutrients, energy-intensive distillation, and transporting materials and fuel, all while keeping costs and emissions low.)
9. Answers will vary. (Example: Benefits include domestically produced fuel, potential lower lifecycle CO₂ than gasoline, and rural economic benefits. Drawbacks include competition with food, land-use change, fertilizer and water demand, biodiversity impacts, and variable yields due to weather.
10. Answers will vary. (Example: It might be better because it uses non-food biomass, can grow on marginal land, and may cut lifecycle emissions. It is challenging because tough plant cell walls require pretreatment and costly enzymes, slower conversions, and sometimes lower, less predictable yields.)

Exit Ticket

Instructions: Access the Exit Ticket and have students reflect on and answer the prompt.