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America’s coal-fired infrastructure of utility and industrial boilers as well as industrial kilns can provide more than enough capability to consume all of the fuel derived from waste that we can produce. We simply need to learn how to use them. Through a combination of new and improved waste sorting technology, higher landfill tip fees, increased cost of transportation, goals for reduced sulfur emissions, emphasis on renewable energy, goals for increased waste diversion and a new U.S. Environmental Protection Agency (EPA) definition for solid waste, the possibility to turn waste into energy has never been better.

In 2006, Americans consumed more than 1.026 billion tons of coal. Most of this was used in boilers to produce electricity—almost 2 trillion kilowatt hours per year. The cement industry used 16 million tons of coal to produce cement. In 2009, Americans generated 243 million tons of waste. According to the U.S. EPA, Americans recovered, recycled and composted 33.8 percent of their waste, burned 11.9 percent in the nation’s waste-to-energy (WTE) plants and landfilled 54 percent. If we simply do the math, that means that in 2009, Americans buried about 131 million tons of waste in our nation’s landfills.

If we assume that 50 percent of that material would be eligible as engineered fuel (EF) for coal-fired boilers, and if we assume that EF has 50 percent of the Btu value of coal, that indicates that all of America’s EF would displace about 3 percent of our nation’s coal needs. Our existing coal-fired infrastructure has more than enough capability to consume our nation’s waste-derived fuel.

Test burn data suggests that little to no change to the back end is needed to cofire EF with coal. Some material handling equipment will need to be added to pneumatically transport the EF to the boilers, but the cost is offset by the lower cost of the fuel. The key questions are: How do we process municipal solid waste (MSW) to produce an EF product that the boiler and kiln owners will want and how can we successfully introduce and combust that material?

In the late 1970s and early 1980s, solid waste professionals experimented with the preparation of refuse-derived fuel (RDF). Early RDF processing technology was designed by aerospace firms such as Raytheon and other nonwaste related companies such as American Can. These early designs sought to find a common denominator for waste, which of course is a heterogeneous mass of materials. Finding no such common factor, the thought was to shred all inbound material to a fixed size. Facilities such as the Monroe County Waste Processing Facility in Rochester, N.Y., and Americology in Madison, Wis., used giant hammermill shredders to pulverize inbound waste.

Needless to say, explosions were an all-too-common occurrence and, as such, the shredders were normally encased in concrete bunkers and wrapped in steel blast mat. Once the waste was shredded, ferrous metal was removed and, in some cases, glass was removed with an intricate process using specific gravity baths. The bottom line was that RDF was essentially garbage with metals and perhaps some glass removed. Some RDF facilities even pelletized their product so it could be stored and burned in stoker grate boilers such as the Reuter facility in Minnesota.

With such a limited amount of processing, one can easily appreciate that special boilers were needed to deal with the corrosion and back-end contaminants. Early RDF facilities did little to reduce chlorides and fluorides, which led to corrosion and the formation of harmful dioxins and furans, and they were incapable of recovering valuable commodities, such as aluminum, paper products and plastics, for resale. As such, RDF production was halted and mass burn facilities—specially designed boilers to burn waste—became more popular as a method to combust unsorted MSW. Of importance, mass-burn facilities were conceived with a primary purpose as a means to reduce waste volume. The production of energy was a means to help defray the capital expenditures (capex) and operational expenditures (opex) of the facilities.

Four decades later, the possibilities for waste processing are far more advanced than in the past. Rather than aerospace companies leading the way with technology, it is companies with longtime waste industry experience. In today’s fuel-producing waste facilities, solid waste is first examined to determine its highest and best value.

For example, ferrous and nonferrous metals, paper products and plastics can be mechanically extracted, baled and sold as commodities for use as raw materials. Their value as a commodity is the highest and best value as opposed to their calorific value as a fuel.

Next, organics can easily be removed. Organics have a parasitic thermal value. While they can be consumed in the boiler, their high moisture content can demand more Btus for thermal drying than they can provide by the combustion of the remaining pulp. Batteries are a source of heavy metals, and chlorinated plastics are a source of corrosion and, when combusted, can lead to harmful air emissions. As such these materials must be processed and removed.

With all this considered, there is a bright line between the old concept for RDF production (shred and remove metals) and today’s waste processing to extract materials for beneficial reuse. Therefore the term “engineered fuel” was created, symbolizing a process whereby only certain materials that are conducive for combustion are targeted and extracted from the waste stream. While mass-burn systems are designed to combust all waste in specially designed boilers and then remove contaminants in a very complex back-end scrubbing system, EF systems scrub the waste in an elaborate processing system so that the resultant EF can burn cleanly with coal in an existing utility and in industrial boilers and kilns with little to no change to the back end.

How it Works
Unsorted MSW is delivered to the mixed waste processing facility with conventional packer trucks. The trucks typically pass a scale for weight and control purposes. The waste vehicles then proceed to the tip floor of the mixed waste processing facility where they tip their loads for processing.

A wheel loader is used to remove bulky waste that would not be beneficial to process, such as mattresses, couches and rugs. The bulk material is loaded onto transfer trucks and hauled to a landfill for disposal.

Large recyclable items, such as white goods (appliances), large metallic items, and clean wood, are likewise separated on the tip floor. These materials are placed into roll-off containers and sold for beneficial reuse. All remaining waste is placed onto an infeed conveyor with a wheel loader or loaded directly onto the first screen with a grapple excavator.

The primary screen may consist of a vibratory screen or a rotating drum screen. The primary screen is often used to liberate a midfraction containing beverage containers and other small materials. The larger fraction contains paper, plastic and other oversize materials. A ballistic separator is then used to separate the light material from the heavy. The ballistic separator can be adjusted to eliminate all heavy plastics. This process in turn ensures that chlorinated plastics and other harmful materials are not present in the EF product.

The light materials are then directed to a series of shredders to be used as EF or they may be directed to near infrared separators to automatically liberate paper and plastic for recovery as commodities. Material rejected by the near infrared sorters can be used as EF. The midfraction materials then proceed to a secondary screen, which is used to remove the “fine” fraction generally consisting of dirt, organics, broken glass, small pieces of paper and some inorganic materials. A magnet is used to remove small metallic objects as well as batteries.

The remaining material can be composted and used as landfill alternative daily cover (ADC). ADC is used in lieu of soil cover at landfills and has many properties that make it more desirable than conventional soils. The remaining midfraction material then proceeds to a magnet where miscellaneous ferrous metal and ferrous cans are removed. Next the material is conveyed to an eddy current separator, where aluminum cans and other nonferrous materials are removed. The remaining material, primarily mid-fraction paper and single-serve beverage containers, can be sorted as commodities on a near infrared separator or combined with the larger fraction from the primary screen and used as EF.

In 2012, the U.S. EPA revised the definition of solid waste. More specifically, a matrix was created to allow materials of beneficial calorific value meeting certain criteria to be removed from the definition of solid waste and therefore no longer regulated as a waste material. This is a very important distinction. This means that EF created from the processing of MSW can leave the mixed waste processing facility as a simple commodity just like any other baled commodity, such as paper or aluminum. Therefore, the facilities using the resultant EF would not be considered burning of MSW and would not be required to have solid waste regulations apply to the storage of the EF material. While individual states create their own regulations, many states will allow EF to be considered as a renewable resource and as such, it falls under the perview of a utility company’s renewable fuel portfolio.

How it Burns
Having completed many large-scale test burns of EF in utility boilers and cement kilns, our results have proven that EF produced as described above when cofired with coal burns as clean or cleaner than the fuel that it replaces. While confidentiality agreements prevent this author from revealing specific details, certain general information can be discussed. We have tested EF in a variety of boilers including stoker grate, cyclone, PC and cement kilns—all with very positive results. In each case, the EF material was used in a “fluff” form and pneumatically conveyed into the combustion unit. In one case, we injected the EF in an air-swept spout, in other cases, directly into a port in the boiler. No change was made to the back end of the boiler. In some cases during the test burn period, mulch blowing equipment was used to transport the EF into the boiler.

Economics
Becasue of the high level of automation and technology available today for mixed waste processing, processing waste is more cost effective than ever before. Furthermore, since the opex and capex of the combustion side are already borne by the utility boiler or kiln operator, these costs do not need to be subsidized in the tip fee charged to waste haulers. By contrast, the cost of waste transportation through transfer stations to more distant regional landfills has never been higher. Waste generation in the U.S. reached a peak in 2007 and may likely never return to this peak. Since the landfill business is a fixed-cost business, diminished volume would indicate that landfill prices will need to rise for the large Wall Street-based waste giants to continue to show level profits. Therefore, we are now at the time where the lines of waste burial and waste processing for beneficial reuse in some cases intersect.

Further, since EF can be sold at a lower cost on a Btu equivalent than the coal, wood or other solid fuel that it replaces, it is simply a cost-effective alternative fuel. In many cases, logistical savings can be found on both ends. A mixed waste processing facility can be sited closer to local hauling routes than a regional landfill. And the EF produced is often closer to the boiler it serves than the coal mine that produced the solid fuel.

Future Trends
More pressure will be placed on landfills to increase their tip fees to make up for lost incremental profits resulting from the “shrinking ton” as well as the increased cost for long haul transportation to more distant regional landfills. Waste-to-energy facilities will likewise be required to deal with the shrinking ton. Since their capex and opex are nearly fixed, any loss in waste receipts will likewise result in further loss in the production and sale of energy. Also, as paper becomes a smaller fraction of our waste stream, the law of supply and demand would suggest that the commodity value of paper will increase as supply decreases.

As the price for paper increases, so will the interest in recovering the material as a commodity for resale. Such an increase in recycling serves to only further reduce the amount of material that can be burned in a WTE facility or buried in a landfill. Therefore, the delta created by reduced volume and corresponding sale of energy must be made up in the form of increased tip fees to waste haulers. One can simply ask—can you pay $100 per ton for baled paper and cost-effectively burn it to produce energy? If the answer is no, then one should expect that in the future, this material will be captured for its value as a commodity rather than for its calorific value. We expect this will result in increased interest in alternative waste handling methods such as mixed waste processing.

Conclusion
Today’s landfills are very sophisticated, highly regulated and should be considered a safe means of disposal. Likewise, today’s WTE facilities are very sophisticated, highly regulated and should be considered a very safe means of waste disposal and, further, should be recognized as a proven and reliable source of renewable energy.

At the end of the day, however, the highest and best use for many of the components in the waste stream is as a commodity. Today’s mixed waste processing technology has become both sophisticated and cost-effective. Likewise, coal-fired energy facilities exist to easily consume the EF that can be produced. By capturing valuable commodities and marketing EF to the existing infrastructure of utility boilers and cement kilns, and with the inherent logistical advantages, mixed waste processing facilities will likely become more prevalent in the United States and play a greater role in the waste management infrastructure in the future.

The author is CEO of Envision Holdings LLC, Cleveland, and can be reached at [email protected]. More information is available at www.minimrf.com.