All landfills are finite spaces that will eventually fill up. Be sure you鈥檝e thought about what you might do when that happens.
Adam Jochelson, P. E., MOLO
鈥淗ave you ever found a dead body?鈥�
鈥淲hat鈥檚 the most interesting thing you鈥檝e seen there?鈥�
鈥淚 bet it smells terrible, doesn鈥檛 it?鈥�
If you become a landfill engineer, be prepared to answer these questions pretty much every time you have a conversation with anyone about your work. I have ready answers to each of these鈥攖hey are:
- 鈥淵es, unfortunately…鈥�
- 鈥淭he wide variety of wildlife in the surrounding wetlands.鈥�
- 听鈥淣ot as bad as you think. The wastewater treatment plant is much worse!鈥�
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An Unexpected Response
But there鈥檚 one question whose answer might surprise you. 鈥淎nd what happens after that鈥�?鈥�
The tone of this enquiry sometimes contains just a hint of defiance鈥攚hen asked by people who think they already know the answer. It generally follows the question about how long the landfill will last. The answer to that, of course, depends on the size of your facility, its incoming waste stream, and future waste generation and recycling rates. At McCommas Bluff projections of remaining capacity currently hover between 45 and 50 years.
Most people expect that sometime in the 2060s, Dallas will be looking for a location to construct a new landfill to handle disposal of the projected 10,000 tons of waste that will be slated for disposal each day. To be fair, if McCommas were to close today, a new landfill is the most likely course of action. But many people are surprised to hear my answer to their query about what the future holds. 鈥淚 don鈥檛 know鈥︹��
Landfills are not perfect facilities. But at this point in history (and for the foreseeable future), among waste management options, landfills provide the best balance of environmental protections and construction and operating costs. However, 50 years is a long time, and technologies that are currently too expensive or have too much other baggage to make them feasible, may be in a better position to handle our waste efficiently. Here鈥檚 a comparative view of several current and proposed technologies for waste management that will likely be vying for your disposal dollar five decades down the line.
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Landfills with Protective Liner Systems
People started using landfills to dispose of wastes in the late 1800s and early 1900s. They gained in popularity starting in the 1940s, and today they鈥檙e the most common type of disposal facility in the developed world. While early landfills were often little more than dumps with a tendency to contaminate local ecosystems, modern day landfills have sophisticated protections designed to minimize the risk to the environment. These include liners, leak detection, liquids collection and gas control systems, cover mechanisms, etc. The cost of running a landfill is highly dependent on land value and thus varies quite widely. In Texas, where land is comparatively inexpensive, you can expect landfill operations to cost about $10 per ton of waste. However, in areas with higher population density and more demands on land, that can rise into the range of $60 to $80 or more per ton.
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Plasma Arc Gasification
The technology behind plasma arc gasification has been around since the 1970s. In a plasma gasification reactor, waste is basically vaporized at extremely high temperatures, above 2,200oC up to 14,000oC (4,000oF to 25,000oF). The process produces an energy packed synthetic gas that can be used to power generators. The lack of oxygen during the process prevents creation of harmful pollutants. The minimal byproduct (about 1 percent by weight) is an obsidian-like glassy slag that can be used like gravel or aggregate. Historically, the primary obstacle to implementation of plasma arc gasification has been that the energy input required to generate the high temperature (produced by means of a strong current, high voltage electric arc) exceeded the energy value of the gaseous products. Recent technological advances in reactor design appear to have solved the energy balance problem, and in the last decade or so, a handful of gasification facilities have been developed and are operational. However, they all process a small amount of waste per day (200 tons or less), the initial capital investment is quite high, and operational costs per ton are not entirely clear.
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Pyrolysis/Thermal Depolymerization
If you look into the etymology of the word, you will find that pyrolysis is a combination of two Greek words鈥�pyro meaning 鈥渇ire鈥� and lysis meaning 鈥渢o cut.鈥� So to put it simply, pyrolysis is cutting with heat. Specifically, the process uses elevated temperatures, in an environment that prevents oxidation, to breakdown the molecular structure of materials to produce something different. It differs from gasification in that the temperatures remain lower (usually between 200oC and 1000oC), and thus the products are primarily solids and liquids and less likely to be gaseous. Pyrolysis in its various forms has been used by humans for millennia to alter the molecular structure of common items. The process that creates a golden brown crust on baked and roasted foods is a form of pyrolysis. It鈥檚 also used to produce charcoal from wood. In the waste industry, pyrolysis can take garbage as a feedstock and produce solids, liquids, and gases that can then be used as fuel sources.
One particularly promising form of pyrolysis is thermal depolymerization, a method that mimics the process by which biological remains transform into oil and gas deep within the Earth. However, rather than waiting millions of years for the end result, thermal depolymerization accomplishes the metamorphosis in a matter of hours. The largest example of this type of facility processes slaughterhouse waste in Missouri and has been the subject of numerous articles in Discover magazine.1 I remember reading about the facility as far back as 2003 just after I started my career as a Landfill Engineer and thinking it was pretty amazing. The primary difficulty of this process is that it requires fairly homogenous feedstock, which MSW is not by any means.
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Incineration/Combustion
Burning garbage (combustion with oxygen) has a long history going back thousands of years. The practice is still common today in rural communities, especially to dispose of cleared trees and shrubs. Furthermore, the majority of U.S. states allow burning of small amounts of waste from your own property as long as it does not present a nuisance to your neighbors. Industrial scale incineration developed a poor reputation due to complaints regarding pollutant discharge, and their use sharply declined starting about 1990. Recent technological advances have dramatically improved the levels of air pollutants in incinerator emissions. However, incinerators must still manage the ash that results from the process, which can often have high concentrations of hazardous substances that require special handling and must be disposed of at specialized landfills. Plus people have long memories, and they have generally opposed reintroducing incinerators as a significant waste disposal option.
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Waste in Space
You may think I鈥檓 joking, but people have seriously proposed blasting waste into space or even straight into the sun as a legitimate disposal option. In fact, with a quick search of the Internet, I found an online poll (of self-selected participants) in which 58% of respondents answered Yes to the question, 鈥淪hould we dump our trash into space?鈥�2 My apologies to that uninformed majority, but the answer is a resounding No! There are so many reasons not to do this that they could fill an article of their own, but I鈥檒l just present the most obvious one: it costs about $10,000 to launch one pound of stuff into space. That鈥檚 about 2 million times more expensive than burying waste in a landfill, and nearly a million times the cost of any other waste management technology. To put it in perspective鈥攔ocketing the waste generated in the U.S. in one day into space would cost about $13.5 trillion鈥攖hat鈥檚 trillion 鈥� with a T. Our Gross Domestic Product (GDP) in 2014 was $17.4 trillion. The International Monetary Fund estimates last year鈥檚 Gross World Product was $77.3 trillion. So if we used all the money in world just to send America鈥檚 waste into space, we would go broke in less than a week.
As I mentioned earlier, for as long as most of you and I will be in the working world, landfills will very likely be the most cost-effective way to safely manage our wastes. This is one of the reasons that being a Landfill Engineer is a good career choice. But that doesn鈥檛 mean it will be that way forever. Technologies improve, costs come down, people鈥檚 opinions change. So at some point in the future, any one of these technologies or a wide array of other options (anaerobic digestion, autoclaving, in-vessel composting, landfill mining, etc.) may win out. Except for the space idea鈥攖hat鈥檚 just crazy talk!
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Adam Jochelson, P. E., MOLO, is a Landfill Engineer and Facility Specialist working for GeoShack, Inc. (Dallas, TX), where he promotes the application of cutting edge technologies to improve the efficiency and effectiveness of landfill operations. Adam built his knowledge and techniques over a nine-year period as the on-site engineer at McCommas Bluff Landfill in Dallas, TX. His unique experiences in engineering and other fields have combined to create an exceptional understanding of the various challenges inherent in landfill planning, design, and operations. He can be reached at (972) 342-3055 or via e-mail at [email protected].
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Notes
- 鈥淎nything into Oil,鈥� Discover Magazine, May 2003 (), July 2004 (), April 2006 () &听 25 November 2008 ().
鈥淪hould we dump our trash into space?鈥�,