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.

Direct Measurement

Direct measurement includes a variety of methods in which FLW is directly counted, weighed or otherwise measured as it occurs. Direct measurement often produces the most accurate FLW figures but can also require the most expertise, time and cost. These methods vary based on the stage of the supply chain thus are organized here by sector.

A summary of the strengths and limitations of direct measurement is shown in Table A3.

Table A3. Factors to Consider When Using Direct Measurement to Quantify FLW

Strengths Limitations / Points to Consider
  • Provides highly accurate data
  • Allows progress to be tracked over time
  • Allows for tracking of causes of FLW
  • Can be relatively expensive and time-intensive
  • Requires direct access to the FLW
  • Methods vary greatly across sectors

Source: Authors.

Using Direct Measurement to Quantify FLW in Primary Production

A common direct measurement approach at the production stage is to take random samples from the crop or product being produced to determine levels of FLW.

An example is described in a toolkit to help farmers to assess the amount of marketable produce remaining in their fields after harvest to help prevent in-field losses of crops (Johnson 2018). The method involves a one-off assessment of the crop in a sample area of a field, involving six steps:

  • Note the row spacing, number of rows and the acreage of the field. Gather equipment.
  • Select and mark rows randomly.
  • Harvest the rows.
  • Sort samples into categories.
  • Weigh and record samples in each category.
  • Extrapolate the data from the selected rows to the entire field and calculate an estimate of the potential in the field.

The toolkit suggests three categories for sorting: marketable (i.e., high-quality appearance), edible (i.e., cannot meet highest buying specification but still edible) and inedible. The categories can be adapted to further sort the inedible items according to the reasons why they are inedible (e.g., insect damage, disease, decay, over-maturity). This additional stage can help farmers identify the root causes leading to items being unsuitable for harvest and suggest other markets where it might be sold.

A summary of the strengths and limitations of on-farm data collection is shown in Table A4.

Table A4. Factors to Consider When Using Direct Measurement to Quantify FLW in Primary Production

Strengths Limitations / Points to Consider
  • Accurate estimates of amounts and types
    of FLW
  • Adaptable to support a change program
  • Estimates can be used to guide financial
    decisions
  • Requires time to implement, often at a busy time of the year for farmers (e.g.,
    harvest)
  • Financial cost associated with method
  • Access to field/farm facilities required
  • Can be used in combination with other methods to obtain reasons for FLW

Source: Authors.

Using Direct Measurement to Quantify FLW in Processing and Manufacturing

How to measure material flows in manufacturing and processing facilities is explained in many toolkits aimed at identifying and tackling food loss and waste. For instance, the Provision Coalition’s Food Loss and Waste Toolkit based on Enviro-Stewards’ approach offers guidance on direct measurement of FLW in manufacturing and processing facilities. The details must be tailored to the situation, but it usually involves diverting the food that is being lost or wasted into containers (e.g., buckets) where it can be weighed. Food waste is collected for a period of time (e.g., one eight-hour shift) and then scaled up to provide an approximate estimate the amount for a week, month or year. More accurate estimates require repeated sampling to account for fluctuations over time (e.g., seasonality).

The tool was designed for Canadian users. The financial and nutritional calculations would be accurate for other users but some of the environmental information uses factors (e.g., carbon factors) specific to Canadian provinces thus would not be entirely accurate for other countries.

A summary of the strengths and limitations of direct measurement in processing and manufacturing is shown in Table A5.

Table A5. Factors to Consider When Using Direct Measurement to Quantify FLW in Processing and Manufacturing

Strengths Limitations / Points to Consider
  • High level of accuracy (for weight and other impacts that are estimated using weight—embedded energy, water, product value, etc.)
  • Can provide granular data to support change programs
  • Data can be used to estimate range of metrics (e.g., financial, environmental) to support business case development
  • Can be operated consistently across many sites (e.g., factories, distribution centers) and data combined
  • Cost of measurement will vary, but can be relatively cost-effective
  • Could lead to change in behavior of staff undertaking measurement, making baseline measurement less accurate
  • Can be used in combination with other methods to obtain reasons for FLW

Source: Authors.

Using Direct Measurement to Quantify FLW in Distribution and Wholesale

Direct measurement is frequently not possible at the distribution and wholesale stage due to the transient nature of the sector. However, most distributors and wholesalers possess information on purchases, inventory and sales. This measurement approach compares inputs (purchases) with outputs (sales) alongside changes in stock levels. It can estimate the value of lost sales and can provide a good starting point for prioritizing action for preventing food from being wasted. The “Mass Balance” module below gives more detail about using this approach to approximate FLW.

Using Direct Measurement to Quantify FLW in Retail

A common direct measurement approach at the retail sector is electronic scanning.

Most retailers use an electronic scanning system for inventory and sales. Under this method, when items leave the retailer’s premises for reasons other than being sold (e.g., landfill, donation), they are scanned, and this information is integrated into a database. This database can then be used to quantify the amounts and types of food going to different destinations. It can be used to estimate the value of lost sales and can provide a good starting point for prioritizing action to prevent food from being wasted. However, fresh produce, bakery and delicatessen items are often challenging to capture since they are often not consistently scanned out.

A summary of the strengths and limitations of scanning in retail is shown in Table A6.

Table A6. Factors to Consider when Using Scanning for FLW Quantification in Retail

Strengths Limitations / Points to Consider
  • High level of accuracy for most products
  • Provides highly granular data to support change programs
  • Approach can be used to estimate a range of metrics (e.g., financial, environmental) to support business case development
  • Can be operated across many sites (e.g., stores, distribution centers) and data can be compared or combined
  • Requires products to be packaged with bar codes
  • Additional solution may be required for unpackaged food (e.g., fruit and vegetables sold loose)
  • Initial cost to develop system can be expensive but can be based on existing sales data system.
  • Requires changes in procedures to ensure wasted, lost and surplus items are scanned

Source: Authors.

Using Direct Measurement to Quantify FLW in Food Service and Institutions

Smart bins and plate weighing are commonly used to measure FLW in the food service sector.

A smart bin is a disposal container attached to a data entry system. The smart bin weighs items as they are added. It also has a terminal for the user to enter details of the type of food being wasted and the reason for it being wasted. This information is passed to a database that can be analyzed to provide information for preventing food waste (or diverting it up the waste hierarchy). It can also be linked to procurement systems to provide financial information. Smart bins can be deployed as a one-off project to facilitate change or provide on-going monitoring for continuous improvement and measurement of performance data. Numerous smart bin providers can be found through an Internet search.

A summary of the strengths and limitations of smart bins can be found in Table A7.

Table A7. Factors to Consider when Using Smart Bins

Strengths Limitations / Points to Consider
  • Provides highly granular data to support change programs
  • Approach can be used to estimate range of metrics (e.g., financial, environmental) to support business case development
  • Can be operated across many kitchens and data combined
  • Measurement has the potential to change behavior (e.g., stimulate FLW prevention activities), so accurate measurement of baseline may be difficult
  • Financial cost and staff time required for installing and using smart bins and analyzing data
  • Difficult to apply to FLW going down the sewer

Source: Authors.

Plate weighing can be used to measure plate leftovers in hospitality, food service and school settings. It usually involves two direct measurements:

  • a sample of trays containing the food directly after serving to establish the average amount being served; and
  • a sample of trays containing the plate leftovers after the diners have eaten.

The amount of plate waste is usually expressed as a percentage of these two quantities.

A summary of the strengths and limitations of plate weighing is shown in Table A8.

Table A8. Factors to Consider when Using Plate Weighing

Strengths Limitations / Points to Consider
  • A well-researched and relatively accurate method
  • Can provide detailed information on the types of food wasted or lost (if recorded)
  • Covers only plate waste; does not include preparation (i.e., back-of-house) waste
    Relatively expensive
  • Can be used in combination with other methods to obtain reasons for wasting food

Source: Authors.

Using Direct Measurement to Quantify FLW in Households

Scales or measurement containers can be used in households to weigh or measure FLW directly. However, it is contingent on the members of the household to correctly sort the FLW, which may lead to underreporting. More information about how households can measure their own FLW can be found in the “Diaries” section above.

A summary of the strengths and limitations of household caddies is shown in Table A9.

Table A9. Factors to Consider when Measuring Household FLW

Strengths Limitations / Points to Consider
  • Simple, relatively cheap method to implement
  • Approach can be adapted to obtain information in a small number of categories (e.g., wasted food, inedible parts associated with food)
  • Potentially can be applied to all destinations or discard routes from a home
  • Likely to underestimate amounts of food wasted.
  • Little information on the types and reasons for wasting food (unless used in combination with other methods)
  • In hot conditions, moisture may be lost from food waste reducing its weight and affecting FLW estimates

Source: Authors.

Using Direct Measurement to Quantify FLW in the Whole Supply Chain Approach

Although measuring FLW directly across multiple sectors is challenging, it is possible to conduct direct measurements of separate sectors and then combine those sectoral measurements to reach a total across sectors. In these cases, the following concerns must be considered:

  • The scope of what is considered FLW must be identical across the sectoral studies.
  • Ideally, the same method of measurement is used. If this is not possible, the different methods should be reported.
  • The FLW being measured must not be double-counted across sectors. This can be accomplished by delineating the sectors in advance.