Waste Wise: Fingerprinting Garbage

These days, waste composition (i. e., what’s in the waste stream) is becoming more and more important. Trends and activities such as increased recycling, organics diversion, landfill-gas-to-energy (LFGTE) and waste conversion technologies all are highly dependent on what’s in the waste stream. Recycling revenue and profit depend on the commodity prices of the individual recyclables being collected (e. g. plastic like high-density polyethylene, cardboard, glass, etc.), which ties the composition of what’s in the recycling bin directly to the bottom line. The prevalence and widespread development of LFGTE projects observed today is based not only on industry drivers of revenue and regulated collection and control of gas, but also on scientific research. The Environmental Research and Education Foundation and many of its stakeholder consulting firms and universities have primarily led these research efforts.

Knowing the waste composition also allows for the effectiveness of recycling programs to be evaluated. For organics diversion, the first question that many ask is how much food waste, yard waste, and paper waste is in the waste stream, as this defines how diverted organics are handled and processed. Landfill-gasto- energy is based on how much gas is produced in a landfill, a function of – you guessed it – waste composition.

There is increasing concern that successes in organics diversion from landfills will adversely impact landfill gas production. Landfilled organics are what turn into that gas. Thus, take the organics away and gas production goes away. LFGTE proponents need to know the status of organics in the waste stream.

Similarly, many of the thermal and catalytic components required for waste conversion processes can be adversely affected by waste with a moisture content greater than 10 percent or too many contaminants such as metals and glass. Both of these variables, again, are functions of waste composition.

Given this, one would think our industry would be awash with waste composition data; however, this is not the case. Although estimates of waste disposal tonnages have been widely available for decades now, accurate information on the composition of waste at the curb or in the dumpster is much more difficult to come by.

A national assessment of readilyavailable waste composition studies was recently completed by the Environmental Research and Education Foundation. Of the 50 states, only 19 (38 percent) had done waste composition studies. Of these, less than half had completed a waste composition study within the last five years.

This means less than one-fifth of states (18 percent) have relatively recent knowledge of what’s in their waste. A study done in 2009 (Staley and Barlaz, 2009) showed that population directly correlates to waste tonnage disposed. As a result, one would expect that the more populous states would have a strong interest in waste composition since a significant fraction of the waste comes from these states.

Of the 10 most populous states (California, Texas, New York, Florida, Illinois, Pennsylvania, Ohio, Michigan, Georgia and North Carolina, in that order), six had completed waste composition studies but only two – California and Illinois – had done so in the last five years. This lack of knowledge of waste composition is surprising given many states have set or plan to set aggressive diversion or recycling goals. How can one establish a goal accurately without an initial understanding of what’s in the waste stream to begin with?

Another key issue is that existing waste composition studies are inconsistent in the categories used to define what’s in the waste stream. For example, one study may define “mixed paper” as including mail and envelopes, while another includes these items in a category called “other paper” along with additional paper components, making it difficult to compare different studies.

Similar inconsistencies in definitions exist when it comes to defining terms such as “zero waste,” “zero landfill” and “recycling,” all of which need to be standardized to be truly meaningful. But when it comes to waste composition, a better understanding of what’s in our waste is needed if we are to advance the industry, improve the efficiency of operations, and evaluate new opportunities.