Diversity of Life
Grade 6 Life Science
Outcome: Assess effects of micro-organisms on past and present society and the contributions of science and technology to human understanding of micro-organisms
IIndicator: Design and conduct an investigation of factors that influence how quickly micro-organisms break down organic matter
Objectives
- Students will learn what is needed for micro-organisms to effectively work in breaking down compost.
- Students will build mini composters.
Materials
| Clear 2-litre pop bottles |
Drinking Straws |
Variety of green materials (see list) |
Variety of brown materials (see list) |
Scissors or Utility knives |
| Styrofoam plates |
Piercing implement |
Packing tape |
Ground soil |
|
Green Materials (Nitrogen-rich)
- kitchen scraps (banana peels, apple cores, vegetable peelings, carrot tops, etc)
- fresh grass clippings
- coffee grounds
- tea bags
Brown Materials (Carbonrich)
- dry fallen leaves
- shredded newspaper
- dry grass clippings
- straw
- corn stalks
Materials to Avoid
- Meat, bones, dairy products – cause odours and attract animals
- Fats and oils – take a long time to break down
- Sawdust from treated wood – toxins in the wood
- Diseased plants, weeds with seeds – seeds and disease may not be killed in the composting process
- Pig, cat & dog manure – may contain parasites
Instructional Procedures
- Composting is the breakdown of organic material. This breakdown is caused by micro-organisms. The organic material is food for them. The compost they produce is useful for gardening.
- In nature, organic material breaks down at a slow rate.
- In order for composting to happen more quickly, the micro-organisms’ needs must be carefully looked after.
- There are different kinds of micro-organisms that can compost organic materials. The kind that is best to encourage is one that uses air (ones that do not use air make stinky gases when they compost). The nicer ‘aerobic’ micro-organisms need these main ingredients to do their job: carbon, nitrogen, oxygen and water.
- Where do we find carbon sources? Carbon-rich materials are often referred to as “Brown materials”. They are usually dry and brown in colour, such as dry leaves, dry grass or twigs.
- Where do we find nitrogen sources? Nitrogen-rich materials, or “Green materials,” include green grass and kitchen scraps.
- There needs to be enough water for the material to remain moist, but not soggy. If there is too much moisture, there will not be enough air circulation to keep the decomposition going quickly.
- Generally for compost to be efficient you put together equal parts of greens and browns. If there are more browns, the decomposition will be slower; whereas, if there are more greens, you may notice more odor and molding than decomposition.
- There are other variables that affect the efficiency of a compost. These include temperature (warmer rather than cooler) as well as size of materials being composted (smaller pieces are desirable).
- Have the students (in pairs or independently, depending on availability of materials) build a “hot” micro-composter. There are three sets of instructions found at http://www.composterconnection.com/site/micro-composting.html
- The students should make labels for the micro-composters listing the approximate amount of each ingredient they have included. It is recommended to add about one cup of ground soil for bacteria. Do not use potting soil as it is sterile.
- Students will be marked on following instructions in the construction of their micro-composter as well as following the carbon-nitrogen ratios.
- You may continue the project after this point by monitoring the micro-composters for temperature, decomposition rate, etc.
- If any of the students want to pursue composting in more detail, see www.saskwastereduction.ca.
- When the projects are finished, the composting material can be dug into a flower bed or garden. It will finish composting there. Be sure to empty the pop bottles carefully and rinse them out to be returned to SARCAN.
Printable PDF version
Back to top
Back to "For Teachers"
|
