Summary

In this lab, students will experiment with creating and capturing biogas, and have an opportunity to see how energy is created from waste. They will explore the differences between non-renewable and renewable energy sources as well as global uses of biogas in a follow-up research investigation.

Grade Level

Middle or high school

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

• HS-ETS1-2: Design a solution to a complex real-world problem by breaking it down into small, more manageable problems that can be solved through engineering.
  
• Science and Engineering Practices
  
• • Analyzing and Interpreting Data
  • Constructing Explanations and Designing Solutions

Objectives

By the end of this lab, students should be able to

• Understand how to create and capture biogas.
• Describe the differences between non-renewable and renewable energy sources.
• Record and analyze data.
• Discuss the impact of the emission of biogas and its effect on the environment.

Chemistry Topics

This lab supports students’ understanding of

• Renewable and Non-renewable resources
• Chemical Reactions
• Conservation of Mass
• Biomass
• Observations
• Gases

Time

Teacher Preparation: 45minutes (time to collect materials)

Lesson: 1-2 classes, and allow additional time throughout the next 3 weeks for data recording

Materials

• Clear , plastic bottles—1 per group (1 liter clear plastic; wide mouth preferred)
• Balloons—1 per group (thick quality latex)
• Permanent Markers
• Large Spoon
• Funnel
• Rulers
• Duct Tape
• String
• Scraps of raw vegetables and grass (about 4 cups)
• Soil from outside (NOT bagged potting soil) (about 6 cups)
• Mythbusters TV episode: Season 6, Episode 8 “Young Scientist Special” about Methane Power (optional)

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
• Parts of this experiment are to be done in a ventilated area or fume hood, as a flammable gas is released.

Teacher Notes

Teacher Prep:

• The amount of materials listed is sufficient for about 6 student groups of 4-5 students.
• Make sure to collect soil from outdoors to use in the bottles.
• Pre-cutting the vegetable scrapes into tiny pieces is advised. This will help when the materials are transferred into the bottle.
• It will take about three weeks for the microbes to digest all of the food in the soil. Allow approximately 10 minutes of class time every other day during the three week period for students to collect the necessary data,
• Upon completion of the experiment dispose of the gas by popping the balloons in a well ventilated area, such as a fume hood or outdoors. Be sure that it is away from any heat sources as methane gas is highly flammable.

Helpful Links:

• What is biogas? And what is it good for?
• Renewable Energy 101: Biogas (video introduction)

Introduce the topic:

• Ask the students, “How do you use energy? What types of energy can you identify?”
• Ask the students to list five activities they do each day that use energy. (Thinking, walking, using a light, driving, etc.)
• Ask the students, “Where does energy come from?”
• Explain the concepts of renewable and non-renewable energy:

a. Renewable energy- comes from sources that do no run out or can be replenished within a human lifespan (about 100 years).

b. Non-renewable energy-comes from sources that cannot be replenished within a human life span, or ever.

• Discuss biogas as a form of energy. Biogas is energy that comes from living things. It is generally made from animal manure. People use biogas digesters to convert manure into methane gas, which is a type of biogas.
• If time allows, show the Mythbusters episode, from Season 6, Episode 8 “Young Scientist Special” about Methane Power. Part of this episode investigates using cow manure as ‘fuel’, so it’s a little different than our investigation, but still a really good example of the outcome/uses in the real world.
• Explain to the class that the goal of this experiment is to create methane gas (a type of biogas). You will be doing this by using microbes (living organisms that are so small you cannot see them without a microscope) in the soil to create methane gas. When you feed the microbes food scraps, a byproduct of digestion is the emission of methane gas.
• Mix the scraps of vegetables and grass into the soil thoroughly. Ask the students, “Why is soil being added to the mix?” (Microbes will be living in the soil).

Cross-Disciplinary Extensions

Connect to Math

• Graphing and charting their data throughout the experiment
• Measuring circumference of the balloon and the height of decomposed material in bottle

Connect to Social Studies

• The efficiency of biogas to be used as a renewable resource
• Areas in the world where this concept would be applicable