Within this section you will find brief descriptions of a number potential FLW measurement methods, as well as additional resources to be consulted for each.

Waste Composition Analysis

Waste composition analysis is a process of physically separating, weighing and categorizing waste. It can be used both to determine total amounts of FLW and to categorize the different types of foods that have been discarded (e.g., fruits, vegetables, meat) or distinguish between food and inedible parts.

A summary of the strengths and limitations of waste composition analyses is shown in Tables A16 and A17.

Table A16. Factors to Consider when Using a Food-Focused Waste Composition Analysis to Quantify FLW

Strengths Limitations / Points to Consider
  • Can provide relatively accurate data on the total amount of FLW within given waste streams
  • Can also provide detailed information on types of food wasted, whether it is packaged, whether it was a whole or part of an item, etc.
  • Detailed information can be used to estimate cost, environmental impacts and nutritional content of FLW
  • Can link information to households in the study, allow demographic analysis, and correlation studies with stated behaviors, attitudes, etc.
  • Cannot be applied to all destinations (e.g., FLW in sewer waste)
  • Detailed studies are likely to be expensive because they require relatively large sample sizes
  • Does not provide much information on why food items were wasted
  • Can be affected by moisture losses in hot conditions

Source: Authors.

Table A17. Factors to Consider when Using a Waste Composition Analysis on all Materials in a Waste Stream

Strengths Limitations / points to consider
  • Can provide relatively accurate data on the total amount of FLW within given waste streams
  • Can be relatively inexpensive where studies/programs already exist
  • Can be replicated to monitor progress
  • Cannot be applied to all destinations (e.g., FLW in sewer waste)
  • Does not include detailed information on types of food required to estimate accurate cost or impacts of FLW
  • Does not provide much information on why food items were wasted
  • Can be affected by moisture losses in hot conditions

Source: Authors.

How to Conduct a Waste Composition Analysis to Measure FLW

Step 1: Identify the sectors to be reviewed

If a waste composition analysis is to be performed across several sectors, start by making a list of the sectors of interest. If the waste composition analysis is taking place within a single household, business or facility, this step can be skipped.

Step 2: Recruit and inform participants

Participants in a waste composition analysis can be identified from publicly available information, such as databases of businesses or through trade organizations (NRDC 2017a). The participants should be fully briefed about when the analysis will be performed and who will be conducting the analysis. It may be difficult to recruit participants due to confidentiality concerns, so an incentive may be useful to encourage participation.

Step 3: Obtain samples of FLW and identify a sorting site

Collect waste samples from the FLW-generating units on their regular trash collection days to ensure that the analysis is conducted on a representative sample. If possible, take the waste sample to a separate site to be sorted, since most FLW-generating units will not have the space available to sort through large amounts of waste.[1]

Step 4: Prepare the FLW for measurement

Prepare the waste samples for measurement with the following steps (WRAP 2012).

  1. Place the waste from each FLW-generating unit in a discrete area (e.g., a table or a marked-off section of floor) where it will not mix with other samples.
  2. Remove the food from any packages and sort the packages into a separate pile.
  3. Sort the FLW into categories based on the scope of the study.
  4. If it is of interest to the study, sort the non-FLW material into categories, such as paper, plastic, metals, etc.

Step 5: Weigh and record the data

Weigh each category of FLW separately. Record the weight data in a prepared spreadsheet based on the food categories identified for the study.

Step 6: Dispose of the waste samples

Once the samples have been sorted, weighed and recorded, they can be disposed of. If the scale of the study is large, it may be necessary to contract a waste management company for a special waste retrieval.

Step 7: Analyze the data

Once the data from the waste composition analysis has been obtained for a single day from an FLW-generating unit, it can be extrapolated to an entire year by multiplying the data by the number of days the unit operates annually

Common Data Challenges when Conducting a Waste Composition Analysis

Reluctance to participate. FLW-generating units may not see the benefit of a composition analysis of their waste stream and may even be actively opposed to participating due to confidentiality concerns. Confidentiality concerns can be addressed through signed confidentiality agreements and by working with local officials who can assure potential participants of the legitimacy of the study. Providing an incentive for taking part in the analysis may also boost participation rates.

Sample collection errors. If the waste management company of the FLW-generating unit is not aware of the study being undertaken, the samples may be inadvertently collected as part of routine disposal before they can be analyzed. This can be avoided by reminding the waste management company of the study and by collecting the sample at least an hour before the usual waste pickup occurs.

Unrepresentative data. The results of a single waste composition analysis might not be representative of an FLW-generating unit’s “typical” output. For example, if a household held a family gathering the night before the waste analysis, the analysis would show much higher levels of FLW than usual. Atypical results can be identified by performing multiple analyses of the same unit on different days. If another analysis is not feasible, comparing the results against other similar units and discarding any outliers that seem overly high or low can minimize unrepresentative data.

Lack of information on causes. Although a waste composition analysis provides highly granular numerical data on FLW, it provides little to no information on the causes of FLW. It may therefore be useful to simultaneously conduct a separate study using diaries or surveys to gather qualitative information on the causes of the FLW.

Additional Resources for Using Waste Composition Analysis

FLW Protocol. 2016. Chapter 4, “Waste Composition Analysis,” in Guidance on FLW Quantification Methods. <http://flwprotocol.org/wp-content/uploads/2016/06/FLW_Guidance_Chapter4_Waste_Composition_Analysis.pdf >.

Natural Resources Defense Council. 2017. Estimating quantities and types of food waste at the city level. <www.nrdc.org/sites/default/files/food-waste-city-level-report.pdf >.

Natural Resources Defense Council. 2017. Estimating quantities and types of food waste at the city level: Technical appendices. <https://assets.nrdc.org/sites/default/files/food-waste-city-level-technical-appendices.pdf>.

WRAP. 2012b. Methods used for household food and drink in the UK, 2012. <www.wrap.org.uk/sites/files/wrap/Methods%20Annex%20Report%20v2.pdf>.

Zero Waste Scotland. 2015. “Guidance on the methodology for waste composition analysis.” https://www.zerowastescotland.org.uk/sites/default/files/WCAMethodology_Jun15.pdf

[1] For a detailed discussion of how to select a site for sorting FLW, see pages 32–33 of Chapter 4 “Waste Composition Analysis” in Guidance on FLW Quantification Methods by FLW Protocol.