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Waste Hierarchy List
What Is the Waste Hierarchy?
What is the waste hierarchy according to ISO standards? The waste hierarchy or hierarchy of waste is the list of outcomes that can occur to waste, running from most desirable to least desirable according to ISO 14000 standards.
The waste hierarchy is, in this order from best to worst:
1. Reduce usage of energy and resources. This is the ideal form of waste handling in the ISO waste hierarchy.
2 If rejected after being manufactured or returned after use, re-use it.
3. If rejected after being manufactured or returned to the supplier, re-cycle it.
4. Incinerate the waste to create energy.
5. Throw away the rejects and send them to the landfill. This is considered the worst option in the waste hierarchy.
The Reasoning Behind the Waste Hierarchy
What is the logic behind the waste hierarchy?
Using less is considered a form of waste reduction, since the less material that is used, the less there is that can be disposed of later. Using less also reduces the amount of mining, harvesting, chemical manufacturing and material processing used in manufacturing the base material used in the initial product. In this regard, a lean process with no waste is ideal under the waste hierarchy and ISO 14000 standards.
Any efforts to use less material or energy to produce a product is considered an improvement under ISO environmental standards; manufacturing a product with less labor is often cheaper, but this is Lean Manufacturing, not something that falls under the ISO 14000 waste hierarchy.
Re-use is considered better than re-cycling because recycling requires energy to melt down and reform the next generation of the product. Re-use is taking something apart or repairing it and using it elsewhere. Re-use can include re-manufacturing, such as repairing a metal item with ceramic cement and then reusing the part or grinding it down to a smaller size and using it elsewhere.
Recyling refers to the melting down of metals and plastics before turning them into something new or using polymerization to break down plastic into its molecules before reforming new hydrocarbon chains. (Not all plastics can simply be melted and re-used.)
Recycling is inferior to reuse in the waste hierarchy because more energy and effort is needed to recycle materials than re-use components. The effort and energy invested in making it are wasted and must be spent again to convert the recycled material into a new product. And recycling requires energy in and of itself, whether indirectly through chemical processes or directly through the heat to melt something down.
While energy recovery from incineration is better than throwing it away, energy recovery is the next to last option since this destroys all of the energy and effort that went into creating the product. Not even the material is re-used.
Simply throwing something into the landfill is the least desirable option under the waste hierarchy. Capturing methane gas from a landfill created by the decomposition of plastic or paper is not currently considered a form of energy recovery under ISO standards.