Waste-to-Energy
The Resurgence of Waste-to-Energy and Conversion Technologies: Where’s the Risk?
While it is tempting to embrace technologies that at first glance appear to show promise, it is important to pause and conduct a full risk assessment before gambling on whether emerging technologies will prove themselves to be commercially, economically and environmentally viable.
Harvey W. Gershman
Waste processing technologies have come a long way in the last century. The technology to extract energy from the combustion of solid waste has been in use since 1898, when the first waste-to-energy (WTE) facility was built in New York. Since that time, WTE technologies have evolved from incinerators that were simply destruction units to large-scale mass-burn combustion and refuse-derived fuel (RDF) facilities that recover steam, electricity and non-combustible recyclable materials from municipal solid waste (MSW).
Although no new MSW-processing WTE facilities have been built in the United States since 1996, there is currently a resurgence of interest in mass-burn combustion and emerging conversion technologies. The reasons: WTE’s solid track record as a proven technology, an increase in fossil fuel costs, restoration of flow control, concerns about greenhouse gases, EPA’s more positive approach to WTE and requirements that electric utilities meet a portion of demand through renewable energy.
What are some of the emerging conversion technologies and how do they compare with mass-burn combustion and RDF? Are they commercially viable options for cities, counties and regional authorities? What companies are taking the lead? What, if any, are the risks of these new processing methods?
This article provides some answers, based on a comprehensive review of WTE and conversion technologies. The growing list of companies we track currently numbers 469: 257 in the United States, 46 in Canada, 136 in Europe and 30 in other countries. Table 1 breaks down the company list by technology.
Current Status of Mass-Burn Combustion and RDF
Since the first WTE facility was built in New York more than a century ago, WTE has matured into a safe, effective and environmentally acceptable technology. Currently, there are 87 WTE facilities in the U.S. with $14 billion in productive assets, generating 2,700 megawatts annually. These facilities process between 6.9 percent1 and 12.7 percent2 of the total MSW generated in the U.S., according to BioCycle and U.S. EPA respectively.
With the renewed interest in this technology, mass-burn expansions have been announced, underway, or completed in Baltimore, MD; Honolulu, HI; and Hillsborough and Lee County, FL. In addition, a number of other localities are engaged in planning and/or procurements for WTE or alternative technology facilities: City of Los Angeles, CA; Los Angeles County, CA; St. Lucie County, FL; Frederick and Carroll Counties, MD (Northeast Maryland Waste Disposal Authority – NMWDA); Harford County, MD (NMWDA); Tallahassee, FL; Palm Beach County, FL; Taunton, MA; Santa Barbara, CA and San Bernardino County, CA. Several others have issued expressions of interest to learn who is out there and what they offering.
U.S. Department of Energy grants are spurring a number of alternative energy projects in the U.S. that will use solid waste as feedstock. For example, with a $50 million DOE grant, Ineos Bio and its partner, New Planet Energy, are planning a two-phased project in Indian River County, FL, that will process wet MSW, vegetative, wood, cardboard and other waste to create third generation bioethanol and clean, renewable power for export to the Florida market. Enerkem of Montreal, Canada, received a similar $50 million DOE grant for the construction and operation of a waste-to-biofuels facility in Pontotoc, MS.
Overview of Combustion Technologies
Proven large-scale waste processing methods include the following incineration and starved-air technologies.
Mass-burn Water Wall Combustion
This technology is considered mature and used more than any other for large WTE facilities in the U.S. and overseas. Mass-burn water wall combustion is the controlled incineration of organic or inorganic waste with more than the ideal air requirement (excess air) to assure that complete burning occurs. The firebox is constructed with water tubes to efficiently capture energy. Water wall systems are fabricated on-site and generally have larger unit sizes: 200 tons per day (TPD) up to 750 TPD. Much of the equipment is field-erected, requiring extended contracting schedules of 28-32 months. Covanta and Wheelabrator own and operate the majority of the privately-owned mass-burn water wall facilities in the U.S.
Mass-burn Starved-Air Combustion
Starved air incineration uses less air than water wall incineration, and it produces ash similar to that from a conventional incineration process. The lower air requirement leads to smaller equipment sizes, which are modular, factory-built and can be brought to a site and set up in a relatively short time, e.g., 18 to 24 months. These units have been built to process up to 150 TPD and are used for smaller WTE facilities and for industrial applications. Active suppliers are Enercon Systems of Elyria, OH, Consutech Systems of Richmond, VA and Basic Environmental Engineering of Chicago, IL. These companies have been supplying incineration systems for MSW for more than 25 years. Other U.S. firms, including Energy Answers of Albany, NY and Covanta Energy of Fairfield, NJ, are marketing project development and management services for modular WTE facilities.
Refuse-Derived Fuel
In an RDF system, MSW is mechanically processed at the “front end” to produce a more homogenous and easily burned fuel, called RDF, which is prepared to boiler specifications. Additional pre-processing can be applied to the incoming waste stream to remove other noncombustible materials, such as glass and aluminum. In an RDF/Dedicated Boiler system, a separate water wall boiler burns the fuel, usually a semi-suspension system, allowing for a smaller, more efficient boiler. In an RDF/Fluidized Bed system, MSW is shredded to less than four inches mean particle size and the RDF is blown into a bed of sand at the bottom of a vertical cylindrical furnace. Hot air is also injected into the bed. Steam tubes in the bed and a section of boiler tubes capture heat from the flue gas exiting the furnace. Currently, there are 13 RDF facilities in the U.S., operated by both public entities (e.g., Great River Energy and Ames Municipal Electric System) and private firms, including Excel, Wheelabrator, Covanta Energy, and Babcock and Wilcox.
Several Emerging Conversion Technologies
In recent years, a number of technologies have emerged for the treatment and disposal of MSW. Most of these involve thermal processing, but others comprise biological or chemical decomposition of the organic fraction of the waste to produce useful products such as compost, chemical feedstocks or energy products. These technologies include, but are not limited to, gasification, pyrolysis, anaerobic digestion and chemical decomposition.
Gasification
Gasification is the heating of MSW to produce a synthesis gas (syngas), which consists primarily of hydrogen, carbon monoxide, carbon dioxide and some trace compounds. The energy or heating value of synthesis gas produced varies from 200 to 500 Btu per cubic foot, half or less than natural gas. After an extensive cleaning step where particulates are removed, the gas can be used as fuel or feedstock or for production of other chemicals.
Facilities using gasification technology are few in number, and small-scale or pilot projects. Seven plants in Japan use technology developed by Thermoselect, a European firm. These plants began operations in 1999, 2002 and 2003, with two firing MSW. The largest has a furnace size of 185 TPD. In addition, 20 facilities in Europe and Asia use gasifiers built by EnTech of Devon, England; none is designed for more than 70 TPD throughput. Two Canadian firms are operating pilot gasification facilities: Enerkem and Plasco Energy Group. Several larger facilities built in Europe have closed for technical and pollution reasons.
Pyrolysis
In pyrolysis, MSW is heated without oxygen or air, thus generating a synthesis gas, char and inorganic residue. The gas produced is similar to that produced by gasification, although it must be filtered of particulate matter. The gas can be burned for energy or used as feedstock for the production of other chemicals. Metals, glass and other inorganic residues will usually melt and are then discharged as a black, gravel-like substance called “frit.”
There currently are no full-scale pyrolysis systems in commercial operation using MSW in the U.S. A 50-TPD pilot demonstration, built and operated by International Environmental Solutions, began operating in southern California in 2005. Although the system is marketed as a pyrolysis system, a combustion chamber is necessary for its operation (for destroying organics in the off-gas) and the presence of the combustion chamber classifies the system as an incinerator.
Anaerobic Digestion
Anaerobic digestion is a wet treatment process where waste is pre-sorted and then fed into water tanks where it is wetted and formed into a slurry. Ferrous and glass are discharged into dedicated containers for recycling, further processing or disposal. The slurry generates “black water,” which is high in organic content and processed without air in sealed digesters. The organic solids break down and generate gas containing methane, which can be burned as a fuel for heating or for electric power generation. ArrowBio of Haifa, Israel has responded to procurements in the U.S., but has not built a facility here; the company operates facilities in Tel Aviv and Sydney, Australia.
Chemical Decomposition
Also referred to as depolymerization, chemical decomposition is a process whereby waste feedstocks are directly liquefied into useful chemical feedstocks, oils and/or gases. The oils are a replacement for fuel oil and the gases consist of carbon monoxide, hydrogen and methane. Changing World Technologies has a plant in Carthage, MO, that uses chemical decomposition on poultry waste. One form of chemical decomposition is used to break cellulose into sugars for fermenting to produce ethanol. The U.S. Department of Energy has been working to move cellulosic ethanol to commercial production in currently small-scale demonstration projects, and has provided grants supporting larger facilities.
Before Leaping, Assess the Risks
Localities considering exploring waste processing technologies must evaluate the relative risks involved in any waste processing technology. They need to ask: What are the risks? Who would assume these risks? And, who will pay the risk premium?
In conducting a risk assessment, it is important to evaluate the following factors, and answer questions such as these about the company offering the technology:
Overall track record, including operational commercial experience with the technology. Where has this technology been used and how successful has it been? What is the individual company’s track record with this technology?
Size and scale of successful facilities. Has the company built facilities of comparable size and scale? Is it comparable to what is needed to process the locality’s quantity of waste?
Environmental performance. What are the characteristics of emissions? Are there likely to be any changes in state or federal legislation that might affect operations?
Overall economics. What capital investment is required to achieve required operating performance? Has the solid waste stream been estimated accurately? Is waste likely to be diverted to competing facilities? What is the cost for residue disposal? Will the facility meet energy market specifications? What are the market specifications for any non-combustible recyclables? Will there be revenue from the sale of non-combustible recyclables?
Reliability over time. What is the company’s record of technical failure and downtime? Does the locality have an alternative disposal option in the event of downtime or technical failure?
Financial strength of the vendor and ability to offer full service arrangements. Is the company financially viable with sufficient capital resources? Is it able to undertake the project without delays in project completion?
Table 2 summarizes the risks of mass-burn combustion and RDF versus the risks of several new technologies. For example, there is little operating history with MSW for gasification and pyrolysis, compared with a long history of commercial experience with mass-burn combustion and RDF technologies. There are no full-scale pyrolysis, anaerobic digestion or chemical decomposition facilities in commercial operation in the U.S., and the gasification systems that do exist are small-scale or pilot projects.
Reliability can only be demonstrated and measured for systems that have a significant history of successful operation. Gasification, pyrolysis, anaerobic and chemical decomposition systems have limited MSW operating history. Although they may appear to be simpler in operation than other systems and have fewer moving parts, it is impossible to draw conclusions about their reliability based on the current limited experience with the technologies. In contrast, mass-burn combustion and RDF have an established history of successful operation and reliability.
The only technologies with dependable estimates for capital and operating costs, based on long experience in the U.S., are mass-burn combustion and RDF. All others have cost estimates that are speculative, theoretical or market driven. Unless a vendor’s cost proposals are backed by substantial guarantees of performance, the proposals cannot be considered reliable.
Conduct a Full Risk Assessment
The process of implementing a viable solid waste management system, like any other large industrial system, is time-consuming and frustrating. Successful systems generally require large capital outlays, long-term commitments and the need to allocate risks in areas where there may be little experience. While it is tempting to embrace technologies that at first glance appear to show promise, it is important to pause and conduct a full risk assessment before gambling on whether emerging technologies will prove themselves to be commercially, economically and environmentally viable.
Harvey Gershman is President of Gershman, Brickner & Bratton, Inc. (GBB), Solid Waste Management Consultants. He has been active in the solid waste management field as an adviser to government and industry for more than 35 years. He has managed the preparation of many plans, market studies, cost and feasibility analyses, contracts development and negotiations, contractor procurements and project financing activities for a broad range of waste-to-energy, district energy, recycling, and solid waste management technologies and services. He specializes in providing strategic planning advice to solid waste service/system managers and owners. He has been called upon by various GBB clients in the past several years to provide an update on waste-to-energy technologies and other technologies coming forward to either convert waste to energy, fuels, or chemical feedstocks. Harvey can be reached at [email protected]. This article is based in part on two recent presentations he gave on WTE and conversion technologies: Municipal Waste Management Association conference presentation, September 30, 2010, www.gbbinc.com/speaker/GershmanMWMA2010.pdf, and WasteCon presentation, August 15, 2010, www.gbbinc.com/speaker/GershmanWasteCon2010.pdf.
Notes
www.jgpress.com/archives/_free/001782.html
www.epa.gov/osw/nonhaz/municipal/pubs/msw2008rpt.pdf
Captions
Table 1
Waste-to-Energy and Conversion Technology Companies
Table 2
Relative Risks of Technologies
Tables courtesy of GBB, Inc.