Why and How to Measure Food Loss and Waste

Diaries - Why and How to Measure Food Loss and Waste

In the context of FLW, diaries refer to the practice of a person or group of people (e.g., the residents of a household) keeping a log of food loss and waste that occurs within their home or other unit. The diary usually calls for the participant to log the amount and type of food being lost or wasted, along with how and why the FLW was discarded.

Diaries can take many forms, such as a paper-based diary, an electronic diary or even a photographic diary in which participants take pictures of their food waste for further analysis.

A summary of the strengths and limitations of diaries is shown in Table A1.

Table A1. Factors to Consider When Using Diaries to Quantify FLW

Strengths Limitations / Points to Consider
Provides information on the types of food wasted and the reasons behind that waste

Can gather data on otherwise difficult-to-measure material flows (e.g., food waste going into the sewer or at-home composting)

Can be relatively expensive, especially if diary participants are given an incentive

Can underestimate the amount of waste due to aspirational biases

Can be coupled with interviews or ethnographic methods to further understand why food gets wasted

Source: Authors.

How to Use Diaries to Quantify FLW

This module provides an overview of the steps that should be undertaken to use diaries to gather information about FLW. Although these broad steps will apply to most cases, a professional statistician or researcher can further tailor the design of a diary to best meet the needs of a given situation.

Step 1: Decide how participants will quantify FLW and for how long

In a diary study, participants can quantify FLW by weighing, measuring the volume or approximating FLW. Of these methods, weighing produces the most precise data, but it is also the most time-intensive for the participant and may be expensive, since participants might be given a scale.

In determining the length of the study, consider the trade-off between a longer, more intensive diary period that will produce more data and the burden that it imposes on participants, who may be more likely to drop out of the study.

Step 2: Identify how the diaries will be administered

Diaries can be administered in print by mail or electronically via a computer or smartphone app. Each method has advantages and disadvantages as shown in Table A2.

Table A2. Advantages, Disadvantages and Examples of Diary Types

Method Advantages Disadvantages Example
  • Relatively low cost
  • Allows for both visual and written prompts
  • Can become lost or damaged
  • May be inconvenient and laborintensive for the participant
See this sample print food waste diary (WRAP 2012a).
  • May be more convenient for the participant
  • Allows for data to be saved and stored electronically
  • Saves time on data entry
  • Requires familiarity with technology and computers on the part of the participant
See this sample food waste tracking spreadsheet (OpenIDEO n.d. )
Smartphone app
  • Most convenient option for participant
  • Allows for use of photographs
  • Limits respondents to smartphone owners with technological capabilities
  • Photographs without measurements may be difficult for the researcher to assess amounts of waste
The app “SmartIntake” is one example of a food waste tracking app—it allows pictures to be taken before and after a meal and then sent to the researcher

Source: Authors.

Step 3: Identify respondent audience

In some cases, the participants in a diary study will be a discreet group. For surveys with a larger population of target respondents, a random sample may need to be developed, in which case a professional statistician should be consulted, although simple random sampling can be conducted when a list of the members of a population is available and complete (Laerd 2012).

Step 4: Recruit participants

Participants in a diary study must be selected from the group being studied. Because keeping an FLW diary is a time-intensive commitment for participants, some sort of incentive may be necessary.

Step 5: Prepare questions to quantify FLW

An effective FLW diary will provide fields for categories of data. Some common fields are:

  • Food type (e.g., carrot, ham sandwich, chicken)
  • Material type (i.e., food and/or inedible parts)
  • How it was purchased (e.g., fresh, frozen, canned)
  • How much was wasted (provide unit of measure)
  • Why it was wasted (e.g., cooked badly, served too much, spoiled)
  • Disposal method (e.g., compost, garbage disposal, pet food)

It is best to include all the above information to form the most complete FLW inventory, although the diary should be tested to ensure that the burden is not too great on the participants.

Step 6: Test the diary and revise

Testing the diary with a small subset of the target audience can provide insight into which questions may be confusing, burdensome or unclear. The survey can then be revised to address the concerns of the testers.

Step 7: Administer the diary

Once the survey has been designed and tested, it can be distributed to the intended respondents. Keep a complete list of survey recipients along with those who respond to track response rates.

Step 8: Prepare and analyze the data

Responses must be standardized and collated. The simplest method is to enter the data into a spreadsheet. If the diary contained open-ended questions, determine whether to enter the response in full or to code the responses into categories. If the diary contained measurements of volume or approximations, convert these measurements to weight using a predetermined conversion factor.

Common Data Challenges in Using a Diary

Underreporting. Both the social desirability bias and “diary fatigue” may lead participants to underreport their FLW. This can be pre-empted with clear instructions about accurate diary-keeping and a reminder that the diary process is not seeking to shame participants over their FLW amounts. Diary results can also be cross-referenced with the findings of other quantification methods (e.g., a waste composition analysis) to determine the extent of underreporting.

Low response rates. Because diary studies are generally voluntary and require the respondent to take time out of their schedules to complete, many have low response rates. A common strategy to boost response rates is to provide an incentive to the respondent. In addition to a monetary incentive, participants may be permitted to keep scales or any other any equipment distributed for FLW quantification purposes.

Additional Resources for Diaries

FLW Protocol. 2016. Chapter 6, “Diaries,” in Guidance on FLW quantification methods. <http://flwprotocol.org/wp-content/uploads/2016/06/FLW_Guidance_Chapter6_Diaries.pdf>.

OpenIDEO. n.d. “Food waste challenge: Keeping a food waste diary.” <https://challenges.openideo.com/content/food-waste-diary>.

WRAP. 2012a. “Your household’s food and drink waste diary.”