When conducting a Waste Flow Diagram (WFD) assessment, evaluating leakage potential is crucial to accurately capture how waste, especially plastic, escapes into the environment. This process also involves understanding the leakage influencers and leakage factors that contribute to this potential. Accurately representing these aspects in the WFD is essential to avoid skewing the results of the actual amount of waste being leaked into the environment.

Leakage Influencers

Leakage influencers are the specific factors or conditions that directly affect the level of leakage and are the influencing factors in each stage of the waste value chain. For example:

• Leakage influencers at disposal facilities include the environmental hazards (risk of flooding or landslides), exposure to weather (persistent winds or runoff), waste handling (presence of waste pickers and compaction practices), waste coverage at the disposal facility (frequency of covering waste), presence of open burning (extent of waste burning), and fencing surrounding the facility (condition and completeness of perimeter fencing).

It is important to highlight that when inputting and validating WFD data, certain leakage influencers exhibit higher leakage factors. For instance, factors such as "Plastic waste leakage during formal sorting", "Plastic waste leakage during informal service chain sorting”, "Plastic waste leaking from disposal facilities" and "Plastic waste in storm drains entering waterways" have significant variability, depending on whether “none”, “low”, “medium”, “high”, or “very high” are selected.

Leakage Potential

Leakage potentials represent the likelihood of waste, particularly plastic, leaking into the environment at various stages of its lifecycle. This potential is usually categorized as none, low, medium, high, or very high. The level you select directly affects the overall results, making it essential to base your choice on real conditions.

Selecting the appropriate leakage potential is vital because it can drastically influence the assessment outcome. For example, a “very high” potential assumes that most of the waste is not managed properly, which could exaggerate the environmental impacts if this isn’t the case.

Key areas where high leakage potentials could skew results due to inaccurate data.

• Plastic waste leakage during formal / informal service chain sorting;
• Plastic waste in storm drains entering the environment;
• Plastic waste leaking from disposal facilities.

Leakage Factor

A leakage factor is the degree to which leakage occurs, and it’s quantified to reflect how much waste is lost at specific points in the waste management process. The WFD framework allows for variability in these factors, meaning they can differ depending on the selected leakage potential.

For instance, where plastic waste leaks during formal / informal service chain sorting.

• A low leakage factor might indicate that only 5% of the plastics are mismanaged;
• A very high leakage factor could indicate up to 100% mismanagement, leading to much more severe environmental consequences.

The choice of leakage factor can significantly alter the WFD results, selecting an appropriate factor based on accurate local data or established waste management practices is crucial to avoid skewed outcomes.

Impact on Results

The leakage factors used in WFD analysis are highly variable. For example, the manual highlights that selecting between a “low” and a “very high” leakage potential can lead to discrepancies by a factor of up to 8. This significant variability means that incorrectly assigning leakage factors can drastically alter the overall results, leading to misinformed decisions or policy recommendations.

For instance, a very high leakage potential in a formal sorting facility—representing a situation where sorting rejects are either dumped or openly burned—could falsely inflate the environmental burden of the waste system. On the other hand, underestimating leakage might lead to overlooking critical environmental risks associated with poor waste management practices.

Key Considerations for Leakage in WFD Assessments

• Understand the system and analyze the sorting, transportation, and disposal systems to determine how well they are managed. This will help you assign the correct leakage potential and factor.
• Local context matters, so adjust leakage potentials based on environmental factors such as climate or topography. For example, areas with high rainfall may experience more waste leakage into waterways.
• Use available data where possible. The WFD spreadsheet includes a quick reference guide for leakage factors and influencers. Use it to help determine the most appropriate leakage values for your system.

Avoiding Errors

Selecting the wrong leakage potential or factor can lead to misleading results. Overestimating leakage may paint an unnecessarily negative picture of the waste management system, while underestimating it can hide significant environmental risks. Understanding the key influencers that affect leakage, such as poor practices and equipment, will help ensure you assign the correct leakage levels in your assessment.

Conclusion

Correctly evaluating leakage potential, leakage factors, and leakage influencers is crucial for producing accurate and reliable WFD results. These aspects directly affect the environmental and economic impacts presented in the WFD. By thoroughly understanding the local waste management system and selecting the appropriate values, you can avoid skewed results and contribute meaningful insights to the waste management community.