This page has been archived on the Web

Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please contact us to request a format other than those available.

Skip booklet index and go to page content

Pollution Prevention Planning Handbook

V – Appendix B: Key Elements of a Baseline Review


Pollution prevention (P2) planning is a systematic, comprehensive method of identifying options to minimize or avoid the creation of pollutants or waste. There are six main steps to developing and implementing a P2 plan3:

  1. commitment and policy;
  2. baseline review;
  3. planning;
  4. implementation;
  5. monitoring and reporting; and
  6. evaluation, review and improvement.

The second step of the planning process, the baseline review is a key component in the development of your P2 plan as it provides the detailed information needed to identify your most significant sources of pollution and to develop solutions for them. It is a systematic approach to building the in-depth knowledge of production and/or product life cycle processes necessary to identify pollution prevention opportunities.

This Appendix describes some of the main components and techniques that are useful in completing the baseline review:

  • process flow diagrams;
  • material flow diagrams;
  • input/output inventories;
  • materials accounting; and
  • materials mass balances.

It also provides examples to illustrate the use of some of these techniques.

3 For further information on these steps, see the section II (Part 2), "Effective Pollution Prevention Planning Implementation & Review".

Defining the Systems Boundary

The first step in a baseline review should be to define the system boundary within which the plan will focus. Figure B2 provides an example of a system boundary within a general manufacturing facility. Will it consider a specific functional area or process, and will it be circumscribed to within the "plant gates" or also include off-site disposal impacts, suppliers and product impacts? This decision is important, as it will influence the subsequent identification of pollution prevention options. For example, if the greatest environmental impact of a product comes at its end-of-life stage, but the system boundary contains only the manufacturing stage, the plan will be unlikely to identify product design and reformulation as a pollution prevention option.

In choosing the system boundary, consideration should be given to which stages in the life cycle of the product, process or service cause the greatest environmental impacts (extraction or processing of raw materials and inputs, product manufacturing, product use, or end of life). Figure B1 illustrates potential environmental impacts throughout a typical product life cycle.

If you are developing a P2 plan as a requirement of a P2 Planning Notice, your system boundary should encompass all areas where the substance, product, or activity, as specified in the Notice, occurs. Ideally your system boundary should include most areas of your facility in order that additional P2 options can be identified above and beyond the requirements of the P2 Planning Notice.

Figure B1: Conceptual Model of a Product's Life Cycle Impacts

Figure B1: Conceptual Model of a Product's Life Cycle Impacts.

Source Modified from CSA Z762-95

Basic Process Flow Diagrams

Facility plans and process diagrams are a good starting point for developing the process flow diagram, although most facilities have experienced retrofits, expansions and repairs that are not reflected in design or construction drawings. Ideally, the process flow diagram should identify each discrete step (unit process) in the production activity. This provides a "bird's eye view" of the relevant processes.

A unit process is a discrete activity (production, processing or servicing action) that has distinct energy, labour and material inputs and outputs. Break activities into separate unit processes when there may be an important environmental impact that could get lost or be difficult to isolate and quantify if left within a larger unit process grouping. Identify whether a unit process is a periodic, batch or continuous process. This will help identify specific options for pollution prevention.

If focusing on one or more specific substances (e.g., specific CEPA-toxic substances targeted for pollution prevention planning), identify the unit processes associated with each use of that substance, and the function of the use (degreasing, solvent, etc.).

When mapping the process flow diagram, include on-site reuse and recycling unit processes, but exclude all pollution control or treatment processes, and all off-site reuse and recycling. The reason for doing this is to identify the material, energy and water losses that leave the process prior to treatment, without assuming that wastes are already being dealt with in the most effective manner possible.

Figure B2 illustrates a generic process flow diagram for a typical production process.

Figure B2: Generic Manufacturing Process Flow Diagram

Figure B2: Generic Manufacturing Process Flow Diagram 

Material Flow Diagrams

Material flow diagrams such as Figure B3 help clarify the precise source, quantities or causes of losses for each unit process. They map inputs and outputs for each unit process onto the process flow diagram developed above. They also serve as an initial, qualitative identification of obvious sources of losses.

A facility walk-through by the pollution prevention team is a good way to initiate the development of a material flow diagram. It is not unusual to identify processes, activities or machinery that deviate from the official facility drawings and process diagrams. A walk-through is usually the only way to identify fugitive sources of losses or unusual sources of losses (such as breakdowns), as these are not planned and therefore do not show up on process flow diagrams. These should be noted and the process flow diagrams revised. In addition, it may be of value to speak to shop floor staff, as they can provide valuable input and clarification regarding specific processes as well as any relevant nondocumented manners for which they conduct housekeeping and maintenance that may affect the process.

Figure B3: Generic Material Flow Diagram for Primary Processing Stage

Figure B3: Generic Material Flow Diagram for Primary Processing Stage

During the walk-through, it is important to follow each process stage from one end to the other, recording the inputs and outputs for each unit process and gaining an understanding of the daily production, start-up and shutdown, and cleaning processes. More than one walk-through may be necessary in order to observe each of these activities properly.

Remember to:

  • identify any on-site reuse or recycling streams;
  • include materials that are used only occasionally and/or do not appear in output streams (such as catalysts, coolant oil and cleaning materials); and
  • label all discharge streams according to whether they are periodic, intermittent or continuous.

Any quantified data that are readily available should be collected at this stage. If the required data are not available, this step can first be conducted in a qualitative manner in order to identify which unit processes are the source of the greatest environmental impact and/or have the greatest potential for a pollution prevention solution. These unit processes can be quantified and inventoried.

It is important not to get bogged down trying to make a perfect material flow diagram; even a preliminary diagram can help provide insights into sources and quantities of losses.

Input/Output Inventories

In this step, systematic quantification of inputs and outputs are added to the portrait that has already been built through the flow diagrams. These data will serve three functions. They will:

  • confirm or improve the planner's understanding of facility operations from a materials flow and materials loss perspective;
  • provide a sound way of prioritizing processes for more detailed analysis; and
  • establish core data on which to base more detailed analysis, evaluate options and monitor future progress.

The inventory can be developed either for the system as a whole (facility level) or for the specific unit processes identified as the source of the greatest environmental impact. It can also be done for all material flows or for the specific substance targeted for reduction.

A decision to inventory only selected unit processes or selected substances will preclude the ability to develop a more complete understanding of material flows across the system and to complete a facility-wide mass balance, which are both important tools for identifying and quantifying previously unknown losses. On the other hand, an inventory of the system as a whole should be supplemented by a more detailed analysis of selected unit processes. Inputs are all materials, energy, services and labour entering the system or unit process boundary. Outputs come in two forms: finished products or services that represent the desired output from a system, and losses or "nonproduct" outputs in the form of by-products, solid wastes, liquid wastes, gaseous emissions and wastewater effluents. Loss is what leaves processes prior to treatment. It is important not to confuse this with what is released to the environment after treatment.

Each substance or material covered by the pollution prevention plan should be accounted for as it moves through the system or unit process. This requires selecting appropriate metrics for comparison across the system. Such metrics should be based either on output (such as volume or mass of product) or on unit of time (such as per day or per year). The measurement unit will vary from case to case, but the following guidelines should be considered:

  • In determining the time factor, always choose a time span that includes production quantity (e.g., tonne/year or kg/hour).
  • Take one full batch in the case of batch production. Include start-up, shutdown and cleaning operations, which are often the source of losses.
  • If losses are associated with shutdown, averaging over long periods may be necessary.
  • In the case of gases, calculate on the basis of volume at standard conditions.

Cost alone is not a useful unit for comparison, since prices for both inputs and products may fluctuate, leading to large margins of error if quantities are derived from financial data. Nonetheless, it is important to record all costs and revenues associated with inputs and outputs while doing this inventory step, in order to conduct the financial analysis of pollution prevention options. Tips on costs to consider in order to complete a comprehensive financial analysis are found in Appendix C, "Assessing the Costs and Benefits of Pollution Prevention Options."

Inventory of Inputs

Inventory all the inputs entering the system or unit process. If the pollution prevention plan is focused on a specific substance, inventory inputs not only of that substance, but of any material that may act as a medium for transfer of the substance (such as water or contaminated waste streams).

In developing the input inventory, it will be important to establish a time frame for the inventory (daily, weekly, monthly, annually, etc.). One important factor in doing so will be whether there are significant fluctuations in inputs and whether the flow is batch or continuous.

Data sources for inputs at the facility or system level can usually be found in records maintained by the company. These include bills of lading and purchase, stock and inventory management, financial management, compliance, and reporting records. Some inputs (such as water, some energy inputs and other materials) may be directly measured with meters.

If large on-site inventories are kept, be sure to reconcile between purchased and actual consumption. If financial management records are being used as the data source, be sure to collect actual volume as well as financial data. It is useful to collect financial data on the cost for each input at this stage for use in the subsequent financial analysis step.

Inventory of Product Output and Quantities of Substance(s) Contained Therein

Inventory the volume or mass of each final product leaving the system boundary. Again, data for this can usually be found in sales records or other internal management records. Document the annual revenue for each final product for use in the subsequent financial analysis step.

If the pollution prevention plan is focused on a substance, inventory the volume or mass of the substance contained in the product, if known. This may require engineering calculations or estimates. If this is not known, it can be determined through the materials accounting or materials mass balance step described below.

Inventory of Non-Product Outputs

Non-product outputs (or losses) will be the most difficult part of the inventory to complete, as most companies do not routinely measure losses in a comprehensive fashion.

Inventory all known losses from the system boundary. Losses may occur through air emissions; wastewater effluent; liquid wastes for underground injection and off-site disposal and recycling; and solid wastes for on-site release to land, or off-site disposal and recycling.

Also inventory the non-product outputs that are reused or recycled in-process or on-site. Materials for recycling contain lost investments of embodied energy and labour that should be minimized.

Data sources for non-product outputs or losses include waybills for solid and liquid waste transfers; compliance data; release and inventory reporting records; direct measurements or sampling results for air emissions and water effluent; monitoring; and engineering calculations or estimates. Some companies report under the National Pollutant Release Inventory, and can start with these measurements.

The precision of analytical data and flow measurements is important. With poor measurement techniques, the absolute error in measurement of these quantities may be greater than the actual waste stream or emission. Accurate calibration and the use of standard measurement methods and procedures are also essential.

Record all known costs associated with each category of non-product output. Costs can include direct costs, such as treatment and disposal costs, and indirect costs such as monitoring and permit fees. Appendix C, "Assessing the Costs and Benefits of Pollution Prevention Options" provides suggestions on how to conduct a total cost assessment.

It may not be possible to identify all sources of non-product outputs at this stage. New sources may be identified and quantified through the materials accounting or materials mass balance approach (see below).

Materials Accounting and Materials Mass Balance

The materials accounting and materials mass balancing steps are important for any pollution prevention program: they make it possible to identify and quantify previously unknown losses.

Materials accounting means finding a general balance between the inputs and outputs of each separate substance. Materials accounting is based on the premise that, for the facility as a whole or for individual unit processes, all materials entering a facility must come out in one form or another.

Mass/volume of inputs = Mass/volume of (output + non-product output)

If this equation generally balances, then the sources of non-product outputs have been identified and an analysis of the cause of the non-product output can be initiated (see below). If the equation is significantly out of balance, then this unaccounted mass or volume represents an unknown output and should be investigated.

If the reason for the discrepancy cannot be found easily, then analysis at the unit process level can be used to ferret out the problem. This can be done by doing a materials accounting for each specific unit process, or by doing a materials mass balance.

A materials mass balance can be used to clear up any problems unsolved through the materials accounting approach. A materials mass balance also offers greater accuracy, but is more time and data consuming than materials accounting. In a materials mass balance, greater efforts are made to balance the statement:

Mass in = Mass out + Accumulation

The main difference is that in materials mass balance, greater accuracy is achieved by using samples and measurements instead of existing records and estimations. The entire process should ultimately be balanced on a kilogram-for-kilogram basis, rather than accounting for each substance alone as in materials accounting.

Materials accounting and materials mass balances can be presented in a tabular or diagrammatic format. A Sankey diagram provides one useful method for representing a picture of material flows and balances. An example of a Sankey diagram is shown in Figure B4.

Figure B4: Example Sankey Diagram

Figure B4: Example Sankey Diagram

Source: JKMAS Inc. distributes Sankey diagrams in North America. Contact JKMAS at 1630 North Main Street PMB 330 Walnut Creek, CA. 94596 USA 925-516-2121

Example of Techniques for Conducting a Baseline Review

The following example illustrates some of the tools that can be used to complete a baseline review, including material flow diagrams, input/output inventories and materials mass balances.

Scenario: Use of Substance X

A facility manufactures cleaners for household use. Substance X is used in the production of four different types of cleaners to keep the hydrophobic solvents and emulsifiers in solution. A total of 16,000 250 ml glass bottles are manufactured annually.

"Off spec" product and spillage of the product containing Substance X are stored in 205 litre drums on-site and transferred off-site for disposal.

Example Material Flow Diagram

In this example, Substance X will be tracked as it moves through the process stages in a batch manufacturing plant. The material flow diagram in Figure B5 will build a detailed profile of the inputs, outputs and non-product outputs (or losses, including on-site releases and off-site transfers).

Example Input/Output Inventories

The quantification of inputs and outputs, through an inventory, will further build a detailed profile of the production processes and all associated inputs, product outputs and non-product outputs (losses).

In this example, input/output inventories are developed for Substance X at a facility level.

Figure B5: Example Material Flow Diagram

Figure B5: Example Material Flow Diagram

Table B1: Example Input Inventory
InputsQuantity Stored On-siteAnnual Quantity Used (tonnes)Quantity Used per Unit of ProductionAnnual Cost of InputCost of Input per Unit of Production ($/tonne)
Substance XN/A500.003115 K0.93
Raw material "A"N/A200.00126 K0.36
Raw material "B"N/A100.00063 K1.8
Catalyst "C"N/A40.00021 K0.5
WaterN/A80.00050.8 K0.05
EnergyN/A20 000 kWh1.252.2 K0.14/kWh
Return tank cleanout waterN/A50.0003----
Return sample flushingsN/A20.0001----

Table B1 illustrates an input inventory using the following data:

  • 50 tonnes of industrial grade Substance X purchased annually
  • production of 16 000 250 ml containers of cleaner.

The inventory of the organization's products containing Substance X yields:

  • approximately 45.2 tonnes of Substance X are transferred off-site in the products
  • approximately 4.75 tonnes of Substance X are lost during the production process as non-product outputs.

Table B2 shows the Inventory of Substance X losses (non-product outputs).

Table B2: Example Loss (Non-Product Output) Inventory
Process StageDescription of Substance X Non-Profit OutputType of Release/TransferEstimated Quantity (tonnes/yr)Reason for Release/TransfersTotal Non-Product Output of Substance X (tonnes/yr)
Holding TankRinsing of Tanks and LinesOn-site release to surface water (from treatment plant)0.05Rinsing of residual intermediate product generates rinsewater with small quantities of Substance X.4.75
 "Off-spec" productOff-site transfer for disposal2Some batches do not have suitable specifications for sale. 
Filling LineRinsing of filled bottlesOff-site transfer for disposal (to sanitary sewer)0.02Filled bottles are rinsed before packaging in shipping boxes; this generates rinsewater with quantities of Substance X. 
 Overflow during fillingOff-site release to land2Spillage occurs during the filling process. 
Warehouse and ShippingSpillage from broken bottlesOff-site transfer for disposal0.68Product falls off pallets and glass bottles break while in transit from storage to shipping. 

Material Mass Balance Examples

Materials mass balances are useful to organize data, identify gaps and quantify previously unknown losses. They can help quantify substances where quantitative data are limited or where information is difficult to collect. Unaccounted-for losses can be revealed when "mass in" (inputs) fails to equal "mass out" (losses plus outputs).

Such an imbalance can also indicate that fugitive emissions or unidentified releases are occurring. In the example illustrated in Table B3, the evaporation of Substance X from the mixing tank can be estimated (0.05 tonnes/year) as the difference between Substance X put into the tank (inputs) and Substance X within products and removed by disposal, treatment and spills (losses plus outputs).

Table B3: Example Materials Mass Balance
SubstanceInputs (tonnes)Outputs (Substance X contained in products sent off-site)Non-Product Outputs on-site releases + off-site transfersMass Balance*
Substance X5045.24.750.05

* Mass Balance = Inputs – (Outputs + Non-Product Outputs)

References and Resources

For more information on pollution prevention and pollution prevention planning:

Canadian Pollution Prevention Information Clearinghouse:

Canadian Centre for Pollution Prevention:

Canadian Environmental Protection Act, 1999:

Your Environment Canada Regional Office.

For more information on techniques for conducting a baseline review for pollution prevention planning:

City of Toronto, 1999. A Guidance Manual for Pollution Prevention Plans:

Ayres, R.U., and L.W. Ayres, 1999. Accounting for Resources 1: Economy-Wide Applications of Mass Balance Principles to Materials and Waste. U.K.: Edward Elgar Publishing

Ayres, R.U., and L.W. Ayres, 1999. Volume 2: The Life Cycles of Materials. U.K.: Edward Elgar Publishing

Freeman, Harry, 1995. Industrial Pollution Prevention Handbook. McGraw-Hill.

Industrial Research Assistance Program of the National Research Council of Canada, Design for Environment web site:

U.S. Environment Protection Agency's Design for Environment Program web site:

Table of Contents
Date modified: