Authentic Lessons for 21st Century Learning

Microbes and Manure = Biofuel

Anaerobic Respiration

Danny Mattox | Published: November 10th, 2022 by K20 Center

  • Grade Level Grade Level 9th, 10th, 11th, 12th
  • Subject Subject
  • Course Course Environmental Science
  • Time Frame Time Frame 3-20 class period(s)
  • Duration More 200 minutes


In this lesson, students explore gas production by micro-organisms by designing and experimenting with biogas digesters made from small water bottles.

Essential Question(s)

Can waste be converted and used for energy?



Students watch a demo of a mini biogas digester, a "burping bottle."


Students design their own experiments to test variables in biogas production.


Students watch videos and read about the science behind the biogas production process and continue collecting data from their experiments.


Students continue to collect data from their experiments and read multiple articles about converting manure to energy. Students also submit proposals for their final presentations.


Students conduct a Gallery Walk to share the results of their in-class experiments and prepare a presentation advocating the use of biogas digestion in their community.


  • Small water bottles

  • Scales/balances

  • Manure (cow or horse is easiest to find)

  • Funnels

  • Gloves

  • Goggles

  • Water

  • Lighter or matches

  • Beaker

  • Paper

  • Food waste

  • Wood chips

  • Apple cider

  • Plastic

  • Oatmeal

  • Other sources of organic and inorganic materials the students can use when designing and testing their biogas digesters

  • Balloons that will fit over the mouth of a water bottle

  • Student devices with internet access

  • Computer presentation software (Google Slides, Microsoft Word, etc.)

  • Markers, crayons, and colored pencils

  • Over-sized sticky notes, butcher paper, or bulletin board paper


Once the preparation is complete and the bottles have had four to five days to sit, you can begin the lesson. Show the students a prepared bottle and tell them that you are going to burp the bottle. Tell them to make observations as you burp the bottle. Students will find out later in the lesson that the bottles represent mini-biogas digesters. Hold the bottle out in front of you and gently unscrew the bottle cap. This will release a small amount of methane, which will make a sound similar to a pop bottle being opened; but the odor coming from the bottle will be much different than the order produced when opening a pop bottle. Go around the room "burping" bottles for class.

After you're done burping the bottle and igniting the gas, ask students these questions:

  • What is responsible for the sound you heard and the odor you smelled?

  • What elements do you think the gas is mode of?

  • Ask students if they think that gas can be utilized as a source of fuel to run industries, vehicles, or even farming operations?

After the discussion is over, you can explain to students that you placed manure, water, and paper in the water bottle 4-5 days ago and that you have left it sitting undisturbed for that period of time. The paper serves as a food source for tiny organisms that are in the manure. As the organisms decompose the paper they produce a gas. The water assists in the decomposition process. Using a strategy such as What Did I Learn Today? have students write down on a piece of paper explaining what they learned from this activity. You can use their responses as an exit ticket.


In the explore phase of the lesson, students will build mini-biogas digesters out of small water bottles. Place students into groups with four students in each group. Explain to students that they will be setting up their own burping bottles and that their challenge is to increase the rate at which the burping bottle decomposes material inside and makes gas. Give students a brief review of the materials in the bottle and their correlation to gas production. Tell students they have access to all the materials you used in the demonstration: manure, water, carbon source

Students will have to determine how they will measure decomposition rate and gas production.

The question driving this experiment is, "Can you increase the rate of decomposition in the burping bottles?" Attached to this lesson is an example of a hypothesis, along with a detailed experimental design which addresses the question. Students can measure rate of decomposition by measuring the weight/mass of the bottles every few days. Students can measure the amount of gas produced by placing a balloon on top of the bottles and measuring the circumference of the balloon (they should not remove the balloons until the experiment is over).

There are numerous experiments students can conduct with the mini-biogas digesters. The goal with this section of the lesson is for students to practice experimental design and to see that the mini-biogas digesters will decompose an organic material and produce a gas. Students should individually write a lab report with all of the components listed in the attached example. In the Evaluate phase of this lesson, they will be constructing a poster and sharing the data with their class. If graph paper is needed, it is attached to this lesson.


Begin by showing students one or two video overviews of working biogas digesters. Ask them to use a 3-2-1 strategy while they watch the video. After the video is over, ask 3 or 4 students to share their 3-2-1 with the class.

After the video and the 3-2-1 share out, students will read the article linked here about aerobic and anaerobic respiration (a copy of the URL is in the Resources section at the end of the lesson). There may be some ideas and/or vocabulary that some students are unfamiliar with, so using a close reading strategy (like CUS and Discuss) could be a good idea for this reading.

After students have finished the reading, they should answer the questions below with their group. After students answer the questions in their groups, have a brief class discussion about each question, calling on groups to share their responses to the questions.

  1. What is the gas that is produced from your bottles?

  2. What happens to the gas when you release it from the bottle?

  3. Is that good for the environment?

  4. Can we do anything to prevent the gas from going into the earth’s atmosphere?


Linked below are four articles that cover how biogas digesters have been used at farms and homes, and how scientists hope to use the methane produced as fuel for space travel. Using a Jigsaw strategy, assign each student in the group an article to read. After the students have read the article, they should come together as a group and discuss their articles.

  1. Biogas Digester

  2. Chapter 7 - Biogas Digesters

  3. Human Poop-Powered Rocket May Fly Man to the Moon in the Future

  4. Manure Digester Means Nebraska Farm is Powered by Pigs

After discussing the articles and reflecting on what they've learned in this lesson so far, the groups should brainstorm ideas for ways that biogas digesters could be used in or around their communities, keeping in mind that they will create a visual presentation for the class based on what they decide. The presentation will be composed using PowerPoint, Prezi, Google Slides, or any other program the teacher choses to use for this assignment.

After the groups have decided on what they are doing, the group will write a Two-Minute Paper responding to this prompt: In one paragraph or less, explain where a biogas digester is needed in our community, why it will be useful in that location, and how it will be constructed. Collect their responses to this prompt as an exit ticket and tell the students you will read their responses before the next class period and let them know if they can proceed with the presentation or if you have concerns about what they've chosen.


Using butcher paper or bulletin board paper, each group should make a poster displaying all their information from the experiment with the mini biogas digesters. The rubric for this task is in the attachments. After the poster is created, they should be placed around the room and students should do a Gallery Walk. One student from each group should stand by the poster to clarify any questions the other students may have about the experiment.

After you have approved each group's proposal (the two-minute paper from the Extend phase), they can begin constructing their presentations and doing any necessary research. Give each group a rubric you will use to grade their presentation so they will know what is expected from them. Tell each group to add what they learn from their experiment into their presentations about using a biogas digester in the community. Each member of the group should speak for 2 minutes, except for the group member who stood next to the poster during the gallery walk and answered questions--their presentation requirement for this assignment is complete. However, they still have to contribute to the final project by researching, providing ideas, or helping build the final presentation.



Detailed animation with narration explaining a large biogas plant: (~10 minutes, higher quality)

Video with a man talking about a large home digester (~3 minutes)

Biogas Animation of complex plant (~4 minutes): madokken. (2003, September 8).

Biogas Animation with narration of small digester for home use (~3 minutes)