What Happens After We Throw Something Away?
Most people rarely think about what happens to things we use after they are no longer needed.
The answer depends on our choices and, surprisingly, where we live. When we finish using something, like a plastic take-out food container, we can wash and reuse it. Or we can put it in the trash or, if a community accepts it, into a recycling bin.
In some communities, materials placed in the trash are transported directly to a landfill for disposal. Other communities have waste-to-energy facilities that burn their trash to recover energy in the form of electricity and/or thermal energy and reduce the amount of residual ash that needs to be landfilled. However, in communities with recycling programs, a plastic container placed in the recycling bin may be collected, sorted, and processed through mechanical recycling to be made into new plastic products. More recently, in some communities, that container could be processed through advanced recycling technologies that convert it back into its original building blocks, which can then be used to manufacture new plastics and other products.
Over time, waste management policies have prioritized these different solutions through the “waste management hierarchy,” a framework used to guide how materials are managed after use to conserve resources and reduce environmental impacts.
As waste generation continues to grow, these decisions become increasingly important. According to the OECD, global municipal waste generation reached approximately 2.1 billion tons in 2023 and could grow to 3.8 billion tons by 2050 without additional action.
In general, the goal of the waste management hierarchy is to:
Reduce what we use whenever possible,
Reuse things, keeping them from becoming waste,
Recycle materials, giving them another life or lives,
Recover the embedded energy of materials, and finally
Disposal via landfill
These policy priorities are designed to maximize resource efficiency by reducing demand for virgin materials, preserving the value of materials throughout their life cycle, minimizing environmental impacts, and improving overall system performance.
Different Materials Follow Different Pathways
Not all materials move through recycling systems the same way. Mechanical recycling is an important and well-established process that works well for many clean, sorted materials. However, some materials are more difficult to recycle through mechanical processes due to contamination, mixed materials, additives, degradation, or product design, so they require different management pathways.
Advanced recycling technologies are currently being evaluated as a complementary option for materials that may be challenging to recycle through conventional mechanical recycling systems.
Recycling vs. Recovery
One factor which complicates where advanced recycling fits in the waste hierarchy is that some advanced recycling technologies such as pyrolysis can in fact produce outputs which are considered recycled content (e.g., monomers and plastic precursors) together with outputs such as fuels, which qualify as recovery, but not as recycled content.
In those cases, it is generally more useful to think about where the output falls in the waste hierarchy, rather than where the technology itself should reside. From a waste management perspective, recycling and recovery are both preferable to landfill, because both offset the need for virgin materials for the products used in society by returning waste products to productive use.
Multiple Pathways, One Broader Goal
Because plastic waste streams are a complex mix of different plastic resins, a mix of strategies and pathways in addition to mechanical recycling are needed, including:
reduction
reuse
mechanical recycling
advanced recycling
and improved collection and sorting systems
These are just some of the many strategies that can support circularity. Other factors, including product design, consumer behavior, education, infrastructure, markets, investment, and public policy, also play important roles in determining how effectively materials remain in productive use. Understanding how these pathways fit together is an important part of informed recycling discussions.