HOD Landfill is located within the eastern boundary of the Village of Antioch in northeastern Illinois. The closed 51-acre municipal and industrial solid waste disposal facility was active from 1963 to 1984. During that time, the landfill accepted approximately 2 million tons of municipal waste.

On September 28, 1998, the Environmental Protection Agency (EPA) issued a Record of Decision (ROD) for the site, with concurrence from the Illinois EPA, which required that specific landfill closure activities be performed. The final Remedial Design (RD), including a landfill gas (LFG) and leachate management system and final cover, was approved by EPA on August 9, 2000.

The final RD included 35 dual gas extraction wells located to allow for athletic fields as an end-use option. Construction activities for the RD were essentially completed in April 2001. At that time, the LFG and leachate collection systems began operating.

Initial operation of the gas management system indicated that approximately 300 cubic feet per minute (cfm) of LFG were available for potential use as an energy source. Local businesses and industries were identified as potential users of this LFG. Ultimately, Antioch Community High School (ACHS) was identified as the only user able to use the energy from 300 cfm of LFG.

In 2001, RMT Inc. contacted ACHS to inquire about its interest in using LFG as an energy source.

In April 2002, the Antioch Community School District applied for and received a $550,000 grant from the Illinois Department of Commerce and Community Affairs' (DECCA) Renewable Energy Resources Program (RERP) to construct a cogeneration system to use the LFG to produce electricity and heat at the high school.

During the fall of 2002, ACHS and RMT began to explore options for using the LFG being collected and flared at HOD Landfill approximately half a mile from the school. Potential options evaluated included using the LFG to produce electricity for use in the school's existing boilers and for use in a combined heat and power system. Through these evaluations, it was determined that the only economically viable option was to produce electricity and heat for the school.

The overall cost of this project, including design, permits, and construction, was approximately $1.9 million.

On December 24, 2002, construction of the system began.

The design and construction of the energy system posed a number of challenges, including resolving local easement issues, meeting local utility requirements, cleaning the LFG, connecting to the existing school heating system, crossing under a railroad, and meeting EPA's operational requirements to control LFG migration. The design of the energy system also included tying into the existing gas collection system at the landfill, installing a gas conditioning and compression system, and transferring the gas to the school grounds for combustion in the microturbines to generate electricity and heat for the school. A half-mile of piping was installed to transfer approximately 200 cfm of cleaned and compressed LFG to the school grounds, where 12 Capstone MicroTurbines are located in a separate building. The 12 Capstone MicroTurbines produce 360 kilowatts of electricity and, together with the recovered heat, meet the majority of the energy requirements for the 262,000—square foot school. The system began operating in September 2003.

A schematic layout of the LFG-to-energy system is shown in Figure 1.

RMT staff worked with the local government, school officials, and EPA, in addition to leading the design efforts and managing the construction activities throughout the project. RMT also provided public relations assistance to ACHS by attending Antioch Village Board meetings to describe the project, to answer any questions from concerned citizens and Village Board members, and to resolve any conflicts that arose during the project.

• designing the system;
• administering contracts, including coordinating access rights, railroad access, and obtaining all appropriate permits;
• creating a health and safety plan;
• managing construction; and
• coordinating utility connections.

Project Design

This is the first LFG project in the United States to be owned by and to directly provide heat and power to a school.

The challenges surrounding the design of this system are discussed below.

HOD Landfill Gas Collection System Tie-in

The collection system at HOD Landfill, which includes 35 LFG extraction wells, a blower, and a flare, must remain operational to control LFG migration. Therefore, the construction of the new cogeneration system required connection to the existing system to allow excess LFG to be combusted in the flare. Additional pipes and control valves were included in the system to route the gas to the conditioning and compression building and to allow the existing blower and flare to remain operational, while providing the correct volume of LFG to the microturbines.

Gas Cleaning and Compression

The gas that is collected from the landfill is conditioned through a series of chillers that drop the gas temperature to ­10°F to remove moisture and siloxane compounds. A schematic diagram indicating the LFG compression and conditioning system is shown in Figure 2. An activated carbon unit is also included to remove additional impurities. The LFG is compressed to 95 pounds per square inch to meet the input fuel requirements of the Capstone MicroTurbines. The gas cleaning and conditioning system is located at HOD Landfill in a building adjacent to the blower and flare.

Gas Piping to the Microturbines Located at the School

High-density polyethylene (HDPE SDR 9) pipe 4 inches in diameter and 0.5 mile long was installed 4 to 12 feet below ground, running from HOD Landfill to the microturbines at the school. The use of horizontal drilling techniques allowed the pipe to cross beneath a stream, a road, public utilities, athletic fields, and a railroad, with minimal disturbance of the ground surface. This was extremely important for the community and the school's athletic programs.

Electric Generation

Each Capstone MicroTurbine fueled by the LFG produces up to 30 kilowatts of three-phase electricity at 480 volts, using 12 to 16 cfm of LFG for a total of 360 kilowatts of electricity‹enough to power the equivalent of approximately 120 homes. The microturbine system incorporates a combustor, a turbine, and a generator. The rotating components are mounted on a single shaft supported by air bearings that rotate at up to 96,000 revolutions per minute. The generator is cooled by airflow into the gas turbine. Built-in relay protection (over/under voltage and over/under frequency) automatically trips off the microturbines in the event of a utility system outage or a power-quality disturbance. Excess electricity not used by ACHS is sold to Commonwealth Edison. A 12-turbine system was selected to provide a system that will remain functional as LFG production from HOD Landfill decreases. Based on the initial LFG collection rates, up to 18 turbines could have been installed. The final payback for this project, based on conservative assumptions for future energy costs, is approximately eight years.

Heat Generation

Each Capstone MicroTurbine produces exhaust energy of around 290,000 Btu/hr at 550°F. The exhaust from the microturbines is routed through heat exchangers that heat the liquid, which then circulates through underground insulated steel pipes running beneath a parking lot to the school's boiler system. Because heat is being transferred to the school through insulated 4-inch-diameter pipes, locating the turbines next to the school was critical in preventing excess heat loss. When waste heat recovery is not required by ACHS, the microturbine exhaust is automatically diverted around the exchanger, allowing for continued electrical output. During extremely cold weather, the school boiler system automatically uses natural gas to supplement the heat output of the microturbines.

Project Experience

This project serves as a model of how a landfill with relatively small quantities of LFG can be used to produce clean, efficient energy. By using the electricity and heat created during power production, ßmicroturbines become more practical for LFG utilization. The main advantages of microturbine technology over other more traditional internal-combustion engines are the clean, quiet operation and the ability to add and remove microturbines as gas flow increases or decreases.

The project's design and construction can be a model for other communities interested in the beneficial reuse of nearby LFG resources. It is an example of how to deal with the numerous community concerns related to developing an alternative energy system based on LFG. Determining suitable equipment for system design, construction, and operation, while considering local community needs and requirements, is critical to a successful project.

This project is a prime example of how innovative partnerships and programs can take a liability and turn it into a benefit. The solution has created a win-win situation for all involved, including HOD Landfill, ACHS, the Village of Antioch, the State of Illinois, Commonwealth Edison, and EPA. Each key player is seeing significant benefits of the energy system:

• Low energy costs for the high school
• Use of waste heat for internal use in the high school
• Clean, complete combustion of waste gas
• Decreased emissions to the environment through reduced need for traditional electrical generation sources
• Reduction in greenhouse gas emissions
• Public relations opportunities for ACHS and the community as the first school district in the United States to get electricity and heat from LFG
• Educational opportunities in physics, chemistry, economics, and environmental management for ACHS students as a result of this on-campus, state-of-the-art gas-to-energy system

MARK TORRESANI and BEN PEOTTER are members of the Solid Waste Engineering Division of RMT Inc. in Madison, WI.

DE - July/August 2004