Slide outline for Lesson 6.3. Twelve slides, one day. Slide 5 needs a current national figure pulled the week you teach it. [Sal: photograph your own two bins before you uncover them; the photo is the review slide and it is more convincing than any chart.]
Food Waste Audit in Our Room
- Unit 6, Lesson 6.3
- Topic 6.1 Where Food Comes From
- Today: we weigh two days of our own trash and do the math
Teacher notes
Image: two clear bins on a counter, one labeled EDIBLE and one labeled NOT EDIBLE, both covered with a towel.
Do now
- Guess: how many pounds of food does one American throw away in a year?
- Then guess where most of it happens: farm, store, home, or restaurants and cafeterias
Teacher notes
Take five pound guesses, low to high, and write the range on the board. Keep it visible so the real number can land next to it.
This is us
- Two days
- This room
- Your food
Teacher notes
Image: the same two bins, uncovered.
This is the hook. Uncover them here and say nothing for five seconds.
The four places it happens
- On the farm: left in the field, wrong shape, price dropped
- At the store: pulled for looks, pulled at a date
- At home: bought and forgotten. The biggest piece
- In cafeterias and restaurants: whole items thrown away unopened
Teacher notes
Image: four photos, one per place: a field with unharvested produce, a store bakery rack at closing, a home refrigerator, a cafeteria tray return.
The numbers
- About a third of the food grown in this country is never eaten
- Homes are the single biggest share
- Per person, roughly 200 to 300 pounds a year
Teacher notes
[Sal: pull the current USDA or EPA figure the week you teach it. Students will look it up on their phones and it is better if your number matches theirs.] Compare to the board guesses now.
Two bins, two different things
- EDIBLE: somebody could have eaten it
- NOT EDIBLE: peels, cores, bones, coffee grounds
- The edible bin is the number we are trying to change
- Peels were never going to be eaten. That is not the shameful pile
Teacher notes
Keep this distinction clean all period. It is what keeps the discussion honest instead of guilty.
The sort
- Two sorters per bin, gloves on
- Everyone else records
- Weigh each bin, or count items
- Write both numbers and the number of people the bins came from
Teacher notes
Bins open on the far table by the window. Any student may move seats without asking.
The math, step 1
- Total edible waste divided by the number of people
- Then divided by the number of days
- Equals waste per person per day
- Label your unit: grams, ounces, or items
Teacher notes
Walk this on the board once, then release pairs. The most common error is multiplying before dividing.
The math, step 2 and 3
- Per person per day times 180 school days
- Equals per person per school year
- Then times the number of students in the building
- Convert grams to pounds: divide by 454
Teacher notes
Circulate with one question at every table: "grams or ounces?" A number without a unit is not an answer.
Three changes
- Each one names WHO does WHAT and WHEN
- "Waste less" is not a change
- "The Station Manager puts unopened leftovers in the labeled bin for the next class" is a change
Teacher notes
Take one from each pair on the board, then vote for the three most doable.
Every pound in that bin
- Took water, fuel, land, and somebody's work
- Look at the wall path from Lesson 6.1
- Which step did the most work for food nobody ate?
Teacher notes
Image: the class's own wall path photo with the last step circled.
Exit card
- Our class wastes about ___ pounds a year
- The one change I will actually do is ___
Teacher notes
Post the class number on the wall path at the "leftovers and waste" step, which Lesson 6.1 left blank. The three winning changes go up next to it and get checked in Lesson 6.5. Bins go out at the end of the period, every time.