Biogeology and Heat Generation

Students measure temperature as they make compost from food waste.

Month Long-Term Project Schedule
Sept Introductory lesson on Biogeology and Heat Generation
Learn how to use and then practice using a dial probe thermometer.
Oct Send home flyer to parents to collect appropriate food scraps for “Compost Party”.
Have “Compost Party” (filling the Jora composter).
Student teams take daily temperature for Jora and make observations.
Nov Student teams continue taking daily temperature and making observations
Students each make graphs of results of first composting experiment.
Dec no experiment
Jan Send home flyer to parents to collect appropriate food scraps for second experiment.
Have “Compost Party” (filling the Jora composter).
Student teams take daily temperature for Jora and make observations.
Feb Student teams continue taking daily temperature and making observations.
Students each make graphs of results of second composting experiment.
Mar Students compare results of the two experiments and note similarities and differences and come up with conclusions.

OBJECTIVES:
VOCABULARY:
MATERIALS:
BACKGROUND:

Microorganisms have chemical requirements, primarily carbon for energy, nitrogen to build proteins and oxygen for respiration. Microorganisms in the soil need to have aerated soil to maintain optimal oxygen levels and adequate moisture necessary for microbial growth.

Decomposers, such as some bacteria and fungi, get their energy by eating dead organisms. Individual decomposers are rarely visible without a microscope, but colonies of them (such as bread mold) can be observed. Decomposers have the ability to break down dead organisms into smaller particles and new compounds, resulting in fertile soil that provides important building materials for plants.

The decomposition process releases heat. Compost piles have to be large enough to go through the thermophilic (heat producing) process to prevent the growth of "bad" microbes (like salmonella) that could harm humans. Measuring the temperature is very important to make sure the composting materials generate enough heat.

Composting occurs because of the efforts of microorganisms. Although worms and insects also help, microorganisms are the key workhorses of composting. There are three main types of organisms that are important in composting:

1. Actinomycetes are complex bacteria that form filaments. They do most of the work of composting. They tolerate low-moisture and low-pH conditions.
2. Small and simple bacteria flourish in the early stages of composting.
3.Fungi are best at decomposing woody substances and other decay-resistant materials.

PROCEDURE:
  1. The week before the experiment begins, send “Compost Party” flyer home to families, asking students to bring in food waste (fruit, vegetables and eggshells). Vegetables, especially leafy vegetables, will help provide nitrogen. Fruit provides moisture. No meat, cheese, bread or processed foods are allowed.
  2. The goal is to fill the Jora Composter on one day. Students can help break up green waste and put it in coffee containers. Ideally, put in 3 parts food and green waste, 1 part manure, and 1 part wood chips. The limiting factor for filling the composter will be how much food waste has been brought in by students. Have them add 3 containers of food waste and then they can add one of manure and one of wood chips.
    There are two sides to the Jora, marked Side A and Side B. Hopefully both sides will fill up, but if classes do not have enough material, fill up Side A as much as possible and put the remainder in Side B. This can help students evaluate whether a full composter is more efficient than a partially filled one.
    Note: It is best to set the day for filling the Jora early in the week since the compost often reacts quite quickly and reaches its maximum temperature in a few days.
  3. After filling the Jora composter, have the students line up and take turns spinning the composter two times each. This mixes the material and aerates it.
  4. Take initial temperature readings using the large composting dial probe thermometer. First, take exterior air temperature in the shade. Place the dial probe thermometer in the shade, with the sensor end not touching anything. Next, take the temperature in the composter. Place the probe deep into the center of the mass of material (without touching the back wall of the composter). Students should take the temperature in both Side A and Side B. Have students line up in pairs to observe correct dial probe thermometer placement and practice reading the temperature.
  5. Student teams should take daily temperature readings from the exterior air in the shade and from the composter in both Side A and Side B. Each member of the team should observe the thermometer and the team should agree on the temperature before recording it. Students should record observations daily as well. They can record comments on color change, smell (good, bad, earthy, etc.), steam production or other observations. By the end, the compost should look and smell like dirt. Before leaving the composter, students should spin the composter once each.
  6. Making compost needs to be monitored to prevent microorganisms from harming people and producing bad smells. Compost needs to exceed 60°C to produce healthy compost. (If after two weeks it has not done so, please contact the compost specialist or MSN.)
  7. Temperatures should continue to be taken daily until the temperature in the composter comes back down to a consistent temperature of approximately 20°C for at least 4 days. Students should continue taking the temperature in both Side A and Side B. Once a consistent low temperature is reached, the students can stop daily readings.
  8. At the end of 3 months (or before a vacation), take out the pre-compost and put it in the black bins. Cool composters such as worms and pill bugs will continue the decomposition process. The compost will mature in the bins until students use it at the end of the year to put in the garden.
  9. Once the experiment has ended, students should graph the temperatures recorded from sides A and B. Days will be on the horizontal “x” axis and temperature will be on the vertical “y” axis. Students should use different colored lines for Side A and Side B data.
  10. Students should discuss the results. Did the temperature go over 60°C for 3 days? What day of the experiment was the highest temperature? Review observation comments. What did you notice that went along with the changes in color and temperature?
  11. The compost experiment should be conducted twice during the school year