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AP Environmental Science Compostability Study


AP Environmental Science Compost StudyAP Environmental Science Compost StudyStudents in Stephen Bailey's classes at Livermore High School are getting their hands dirty. To help introduce the AP Environmental Science course, the veteran science teacher challenges students to test the compostability and degradability of a range of materials. "It serves as an introduction to the scientific method, of observation, testing a hypothesis, being careful with a control, writing solid measureable observations, writing in the lab book, and sticking with a long-term investigation," explains Bailey.

In the first week of school, students choose an item commonly found in the garbage or littered on campus. Each item is tagged with the student's name and tied with a length of green yard, then buried or placed in the sun in a garden space outside the classroom. "Some students are testing compostability by burying their item underground and others are interested in photo-degradation- the process of items breaking down in the sun," says Bailey.

Student retrieving and item for observationStudent retrieving and item for observationEvery two weeks, students retrieve and examine their item. Using their lab books, students record observations. Bailey encourages students to make their own discoveries, often employing a socratic method to challenge assumptions and push discovery. "This is really an inquiry process. I don't have a data collection sheet or a pre-determined set of measurements students must take. Instead, I ask how they will know if something has changed for their item."

"I let students fail to have a measureable hypothesis, so they learn to do a better job next time. A restart is possible when using such a long time span for the activity. One student buried an apple, and it was dug up and consumed by a visiting nocturnal organism by the first two week observaton. So we will try burying an apple under a big rock next time."

Students carefully record changes in color, texture, and mass. Many have also pinned a "control" copy of their item to the classroom wall to observe differences between an item kept in the climate-controlled atmosphere of the classroom compared to items exposed to the elements outdoors.

Control items hang in the classroomControl items hang in the classroomJust one month in to the investigation which will span seven months, students are finding many surprising results.  While many hypothesized that compostable items such as paper would lose mass as they break down, initial measurements show that many items are actually heavier now than when the project started. One student noticed that the gum wrapper she was studying felt slightly damp and attributes the gain in mass to added moisture from the soil. Other students speculate that items might gain mass as micro-organisms attach themselves to compostable materials.

As students experiment, they are also diving right in to their AP Environmental Science text book, reading a chapter about solid and hazardous waste management, hearing from guest speakers, and monitoring the school's recycling program. As students make their observations of each item, Bailey offers impromptu composting demonstrations and lessons in the school's compost pile. Pitchfork in hand, Bailey points out the fungi and invertebrates that are breaking down landscape clippings into new soil outside the science lab.

A stone cat guards a dead rat.A stone cat guards a dead rat.Bailey, a master of the "teachable moment," finds many opportunities to connect real world examples with the waste management theme in class. Recently, a loudspeaker announcement on campus called for a custodian to clear a trap that caught a rat on campus. Bailey raced to collect the rodent and students have buried it in soil (under a large stone cat sculpture) to monitor its decomposition.

On another day, students observed that the concrete sidewalks were covered with black spots of gum. With the suggestion that the campus run a "gum-redemption" program to pay students for returning scraped gum to the science department, Bailey asks students to collect and weigh samples of dried gum. At just over 1 gram each, a lively debate erupts in class about how much to pay to incentivize the scraping and collection of gum from campus sidewalks.

Investigations and observations related to the waste stream on campus will continue throughout the class's two-trimester span.