Background and approach in waste hazard classification

According to Commission Regulation (EU) No 1357/2014, the hazard properties (HP) to consider and that can render waste hazardous are:

HP 1
Explosive
HP 2
Oxidizing
HP 3
Flammable
HP 4
Irritant – skin irritation and eye damage
HP 5
Single/Specific Target Organ Toxicity (STOT)/Aspiration Toxicity
HP 6
Acute toxicity
HP 7
Carcinogenic
HP 8
Corrosive
HP 9
Infectious
HP 10
Toxic for reproduction
HP 11
Mutagenic
HP 12
Release of an acute toxic gas
HP 13
Sensitizing
HP 14
Eco-toxic
HP 15
Waste capable of exhibiting a hazardous property listed above not directly displayed by the original waste

In order to be classified as non-hazardous waste, none of the 15 hazard properties shall be displayed by the waste.

To conclude whether a material is hazardous or not with respect to the additive hazard properties such as HP 4, HP 6, HP 8 and HP 14, the sum of all relevant concentrations of relevant substances have to be compared with concentration limits defined in Regulation (EU) No 1357/2014. The so-called cut-off values are introduced in order to exclude substances that are present in very low concentrations and will not have significant contribution to the summation. Cut-off values are defined for hazard properties where the additivity criteria are applicable. When concentrations of a relevant substance is above the cut-off value, it has to be taken into account in the assessment of the summation of concentration of relevant substances. Consequently, concentrations of relevant substances below the cut-off limit do not have to be considered in the summation. For instance, the cut-off value for HP 8 corrosive is 1% that means that the presence of substances with concentrations lower than 1% can be ignored. Conclusions about the individual hazard properties such as HP 5, HP 7, HP 10, HP 11 and HP 13 can already be done by comparing individual concentrations of relevant substances (no summation), with concentration limits defined in Commission Regulation (EU) No 1357/2014.

Total content analyses only reveal information regarding the elemental composition but do not give information on the chemical form (speciation) of these elements in the waste. The number of possible substances is almost infinite, and therefore a worst case approach (for example, “what would be the consequence for classification if all Cu in the bottom ash is in its most hazardous form”) is a common approach to draw quantitative conclusions on the potential presence and amount of substances.

A worst-case assessment and most hazardous substances analysis normally makes a basis for Tier 2 where it is assumed that the total amount of each relevant element is bound in its most hazardous form. As example, among several substances that possess the same hazard (the same hazard statement code), the most hazardous is the one that requires least of needed element to reach the concentration limit ascribed to that hazard. If the classification that follows from worst case approach is non-hazardous, no further action is needed. If the classification is hazardous, expert knowledge can be used to make stepwise a more realistic estimate instead of a worst-case approach. This strategy is known as a tiered approach in waste classification (schematically shown in Figure 1).

Tier 1 is typically a general screening in which the relevance of hazardous properties (HP 1 to HP 15) is assessed based on knowledge of the gross characteristics and composition of MSWI bottom ash.

Tier 2 operates with the elemental composition and focuses on those hazardous properties that are not excluded in Tier 1. A worst-case assessment and most hazardous substances analysis normally makes a basis for Tier 2. Note that ClassifyMyWaste performs only Tier 2 assessment. The worst-case assessment in Tier 2 rules out a number of hazard properties and/or hazardous substances while the potentially present remaining hazardous substances are taken to Tier 3.

In Tier 3, expert judgment including the knowledge on stabilities of the substances, information from geochemical modelling, information on leaching properties and literature data are used to evaluate the remaining hazard properties. If needed, the ECN experts are happy to help you with performing the Tier 3 assessment of your waste.

Figure 1
Figure 1. Schematic representation of the tiered approach used in waste hazard classification.