Have you ever felt like you just bought some lettuce and it’s already gone bad, turning soggy and gross? Or what about that milk — how can it already be past its expiration date? Buying food and then throwing it out before you eat it because it’s gone bad is a common problem for people — in the United States, it’s estimated that people throw out up to 40% of the food they get. What a waste, literally! Not only is that food filling up landfills, accounting for some 31 million tons of waste each year, but it costs people a lot of money too. Each month, it’s about $33 per person wasted, adding up to about $400 for a person in a year.

For this Instructable, I decided to answer the following question: Which foods are thrown out most frequently in my household, and how much money is it costing me? In other words, if I bought those foods in smaller amounts (because I’m not eating them before they go bad), how much money would I save? My hypothesis was that the foods we’re throwing out the most are vegetables (especially lettuce) because I feel like I throw them out a lot, but I don’t think it adds up to that much money — maybe $10 for our household in a month.

A little background about my household: It includes two adults who compost, have chickens, and have a vegetable garden. This basically means that none of our food is actually ever thrown in the trash — any bits that are still good go to the chickens, and everything else goes into the compost. Additionally, we get some food from our vegetable garden (although when I did this investigation in the early spring, the garden wasn’t producing much yet), and doing this Instructable is good to help you know what you should plant in the garden (i.e., what you’ll be able to eat before it goes bad), and what you shouldn’t plant or should plant less of in the future.

Step 1: The Testing Procedure

Data Collected

I created a spreadsheet to keep track of all of the perishable food we got over time. I printed out the spreadsheet and stuck it on the refrigerator so it was easy to fill out when we put away new food. This included foods from the grocery store, our garden, and leftovers (but because of time restraints, I didn’t include foods that didn’t expire for months). For each food, I kept track of the following:

Food name
Quantity (whatever was a convenient description, such as by the container, ounces, number, etc.)
Food cost. I didn’t fill this out originally, but later found this out and filled it in for the foods that were thrown out so I could figure out how much money was lost. I’d recommend filling it out while you collect the other data since you’ll have the receipts handy.
Date purchased
Expiration date. This was either the listed expiration date (if given) or my anticipated expiration date (for example, I typically expect lettuce to last one week).
Amount consumed. This was filled out when we ate all of the food, or when we had to throw some out. If not all of the food was eaten, I found it was easiest to fill this out as a percentage, estimating what percentage was eaten.
Amount tossed. This was filled out either when we ate all of the food (and wrote down “0” for the amount tossed), or when we had to throw some out.
Date tossed. This was filled out either when we ate all of the food or when we threw some/all of it out.

You can see a picture in this step of some of the data I actually collected. In this step I’ve also included a blank, revised spreadsheet (as a PDF and Excel spreadsheet) so you could use it to do your own investigation!

Determining Whether Food has gone “Bad”

This was usually done by visual inspection — see the pictures for examples. If a food item had an expiration date, such as milk, and it was past its expiration date, I still “tested” it (by visual inspection, smell, or taste) to see if it had actually gone bad or not. Use this method with caution :)

Testing Time Period

I did this investigation for a total of 48 days (from March 3, 2014, to April 19, 2014). I analyzed the data for foods that were obtained during this time period and either completely consumed or thrown out. (Foods that were obtained but not yet completely eaten/tossed weren’t counted in the data analysis.) It’d be great to do this investigation for a longer amount of time, especially since I’m sure there will be seasonal variation as vegetables in the garden are ready to harvest, but I was restricted by time restraints.

Step 2: Results: Foods Thrown Out

See the graph here for the results. I initially analyzed the foods that were thrown out by event. For example, in the graph you can see that I threw out avocados in four separate events, and so they’re listed four times. Similarly, mushrooms, broccoli, and sprouts are all listed twice for this reason. The graph shows the amount of the food that was thrown out in that event as a percentage of the original food that was purchased/stored. For example, for the pasta, we had about 1 cup stored, but about ¾ cup was thrown out eventually, so it’s listed as 75% being thrown out. See the next steps for additional analysis!

Step 3: Results: Cost of Foods Thrown Out

By Individual Event

See the first graph here for results. When analyzing the foods that were thrown out by event, here are a few observations that can be made regarding the cost:

The broccoli soup ended up being the most costly food tossed. We made a lot of it and found out we didn’t like it.
One time when we bought avocados ended up being the second most costly event, but you can see there were three other times when we bought avocados and had to throw some out too.
No single event wasted more than $7, and most were around the $1 to $2 range.

Totals

See the second graph here for results. When analyzing the foods that were thrown out by totals for that type of food, here are a few observations that can be made regarding the cost:

Overall, the food that we lost most of our money on was avocados ($7.49 for the time period, combining four individual events). (Avocados are expensive and they go bad quickly.)
The next priciest food was the broccoli soup that we made and didn’t like ($6.70).
Mushrooms and sprouts became the third and fourth priciest foods that were tossed, respectively, when combining the two separate tossing events for each.
Although they were tossed twice, broccoli still remained a small loss because so little was thrown out each time.

Making a Neat Graph

I made a neat version of the second graph by using stacks of quarters — see the third graph in this step. Basically I took a picture of these stacks of quarters and then added the axes/labels in Photoshop. Each stack is accurate to the closest quarter. This is a good visual representation of the amount of money lost on throwing away each food as I think it helps people think of the losses in a more tangible way.

Step 4: Results: Expiration Dates

Since I’d collected data on the dates when we obtained the food, the listed or anticipated expiration dates, and the date the food was consumed or thrown out, I thought it’d be interesting to also see (1) which foods lasted longer than we thought they would and (2) which foods didn’t last as long as we thought they would. See the graphs in this step for these analyses.

Foods Thrown Out

These graphs list the foods from largest percentage thrown out to smallest percentage thrown out, going left to right. You can see that usually the food was thrown out when it was past the anticipated expiration date, but there are a few times when this wasn’t the case. To look at this better, I made a normalized graph (second graph shown) by subtracting the anticipated expiration date (in days) from the days until the food was thrown out — this means that if a food was thrown out before its anticipated expiration date, it has a negative number. By doing this, you can see (in the second graph) the following:

Every time the avocados were thrown out, they hadn’t reached the anticipated expiration date. This means that basically I thought they’d last longer than they did (I expected them to last 5–7 days, but some would get thrown out after 3–6 days).
The broccoli soup is the only other time food was thrown out before its anticipated expiration date, and this is because we didn’t like the soup and tossed it early.

Foods Not Thrown Out

I did the same type of analysis for the foods that were not thrown out to see if any of them lasted longer than expected. For these graphs (all have “Foods Not Thrown Out” in their titles), the foods are listed from closest to furthest away expiration date, going left to right.

The third and fourth graphs (“Foods Not Thrown Out… vs. Listed Expiration Date”) are looking at foods that have listed expiration dates. For these foods, I found that sour cream and pizza crust lasted many days beyond the expiration date (18 and 9 days, respectively).

The fifth and sixth graphs (“Foods Not Thrown Out… vs. Anticipated Expiration Date”) are looking at foods that don’t have listed expiration dates, so I had to give it my best guess. For this analysis, I found that the following foods lasted longer than I expected:

Bean cookies. This happened twice — I thought they’d last between 5–7 days, but both times they were still good after 9 days. (As a side note, the cookies are specifically these Chocolatey Peanut Butter Black Bean Cookies - yum!)
Bananas. This happened three times — I thought they’d last 7 days but they were at 12 days.
Broccoli salads. This happened twice — I thought they’d last 7 days but they were good at 10. (As a side note, the salads are specifically these Super Salad Jars, another Instructable I made.)
Tomatoes. These lasted much longer than I expected — I anticipated 9 days, but they were still good after 26 days!
Apples. These also lasted much longer than expected — I anticipated two weeks, but they were still good at 27 days!

See the last graph for a summary of the foods that lasted longer than I expected. Overall, sour cream, tomatoes, and apples, were at the very top.

Step 5: Results: Overall Causes for Foods Thrown Out

After doing all of this analysis, I tried to come up with reasons for why each of the foods that were thrown out ended up that way. Here are the assignments I made, which are summarized in the pie chart in this step:

Didn’t eat it before it expired. These are foods that, as expected, went bad after the anticipated or listed expiration date, so I just wasn’t paying close enough attention. This made up the majority of the spoiled foods, cost-wise (accounting for $13.11 during this time period) and included: mushrooms, milk, sprouts, red bell pepper, cucumber, lettuce, pasta, and broccoli.
Expired sooner than anticipated. These foods went bad before the anticipated expiration date and made up the second largest chunk of lost money ($7.49). This only included the avocados.
Didn’t like it. This only included the broccoli soup we didn’t like, accounting for $6.70.
Don’t typically buy. These are foods that we don’t routinely get, so they can be harder to fit into the regular eating schedule. This included the brussel sprouts and mahi mahi (for $3.58 total).
Bought as a treat. Similar to the “don’t typically buy,” these are foods that are kind of impulse-buy items and aren’t regularly purchased. This just included the coconut pieces (costing $2.50 total).

Step 6: Conclusion

There are many conclusions we can draw from this investigation, but in direct response to the hypothesis I can say the following:

By event frequency, the foods that were thrown out the most were avocados (four times), sprouts (two times), mushrooms (two times), and broccoli (two times). Everything else was only thrown out once. This partly supports my hypothesis that vegetables would be thrown out most often (although lettuce was not a frequently, or costly, tossed item). When accounting for the cost of the food items and combining all events, the avocados were the biggest loss, followed by broccoli soup, mushrooms, and sprouts, but broccoli was not a contender.
If somehow I didn’t throw out any of the foods I did during this time period of 48 days, I’d save $33.17 (the total cost of all of the thrown out food). If this is averaged over the normal length of a month (30.4 days), it comes out to about $21.01 lost for one month. My hypothesis wasn’t correct — I thought I’d be losing about $10 in a month for our household, but in reality it’s more than twice that amount! (As a side note, it's quite possible that by just doing this experiment we ended up throwing out less food than usual since we were more aware of what we were buying and what was going to go bad soon, so normally we may be throwing out even more than this!)

Based on my results, this is what I should be doing to throw out less food and save some money:

Buy fewer avocados all at once! They don’t last as long as I expect them to.
Because of the broccoli soup, I should make smaller amounts of a new food to make sure we like it before making a large, costly batch.
Buy mushrooms, sprouts, other vegetables, and impulse items less frequently, or plan better so they’re used before they expire.

Also, I shouldn’t worry about getting/making bean cookies, bananas, broccoli salads, tomatoes, apples, sour cream, or pizza crusts when I want them — they last longer than expected.