Current perspectives on waste management are incomplete without giving a nod to the desire to be more sustainable. The slogan “Reduce, reuse, recycle” has been pounded into our heads for decades now. (For anyone under 30 years old, that means pretty much since you were in diapers.) Various campaigns have sent the message to broader society that landfills are bad and recycling and composting are good. But the perception of waste-to-energy can be good or bad, depending on where in the United States one resides. So, what about landfills? Are they a relic of an earlier time when waste was rubbish rather than a resource? Or is there a role for landfills in today’s circular economy?

An even larger consideration relates to how materials that are ultimately destined for the waste stream, like packaging materials, are manufactured. If these materials are not fully reusable, recyclable or compostable, then our ability to return them to the economic cycle is limited with current technology. For example, materials like rigid plastics are not recyclable because of certain additives that are placed into the resin when the plastic is made. For similar reasons, other plastic types are less desirable to recycle and thus have limited demand. This suggests that what manufacturers do upstream before a material becomes something to discard has significant bearing on what happens to that material. Additionally, some materials are simply not recyclable, including hazardous household wastes, and most of these materials wind up going to landfills.

Even if a material is recyclable, the recycling process itself isn’t 100 percent efficient. For example, composite materials typically cannot be separated, so every recycling operation generates some level of residue due to contamination or materials that were once recyclable but can no longer be. Likewise, through continued recycling, paper and textile materials’ fibers reach a point at which they can no longer be recovered. Sometimes efficiency improvements or newer technologies can alleviate such issues, but some residues will always be generated.

Considering this, it should be noted that it is not even thermodynamically possible to achieve 100 percent recycling. Scientifically, this means that ordered and enclosed systems must increase in entropy. Translation: As things go from a higher-ordered state to a less-ordered state, the laws of thermodyamics dictate that there will always be some remaining residue or waste that must be managed. Even waste-to-energy facilities, viewed by some as capable of managing all types of wastes, typically remove bulky waste materials (residue #1), and approximately 5 percent of the tonnage that goes in winds up as ash (residue #2), which, in turn, typically goes to—you guessed it—a landfill.

These examples demonstrate the current limitations of how we, as a society, manage the materials we generate, consume and ultimately discard. Heijo Scharff—manager of research and development at the waste management firm NV Afvalzorg in Nauerna, the Netherlands, and the keynote speaker at the 2014 Global Waste Management Symposium—indicates that a 100 percent recycling society is impossible.

So, back to the main question: Where does the landfill fit into the sustainability equation? The answer is that it plays an important role as a repository for waste materials that either can no longer be recycled or could not be recycled in the first place. From a sustainability perspective, this dictates that the size of the waste stream be kept as small as possible, yet it should be clear to us that zero waste isn’t really “zero.” Therefore, some disposal mechanism must exist for the non-zero waste that still remains. 

Bryan Staley, P.E., Ph.D., is president of the Environmental Research and Education Foundation, a nonprofit organization that funds and directs scientific research and educational initiatives to benefit industry participants and the communities they serve.