Landfill gas-to-energy (LFGE) projects are not particularly new. Utilizing landfill gas (LFG) as a fuel source began in the United States in the 1970s. According to the Environmental Protection Agency’s (EPA) Landfill Methane Outreach Program (LMOP) database, as of Nov. 30, 2010, there were 728 operational LFGE projects at 499 landfills in the United States. Of these, 180 use LFG for direct process heating and 548 use LFG as a fuel for electrical power production with an average capacity of 3.4 megawatts (MW).
However, there are many smaller sites that, when taken in aggregate, represent significant potential for energy recovery and greenhouse gas (GHG) emissions reduction. For the purposes of this article, “small sites” are defined as landfills where recoverable LFG flow rates are less than 350 standard cubic feet per minute (scfm).
LFG is an excellent source of renewable energy for several reasons. First, the energy production potential is not as dependent upon geography and climate as are wind, tidal, hydroelectric and photovoltaic energy sources. Second, landfills are located in relatively close proximity to population centers, reducing the cost of necessary power transmission infrastructure. Third, LFG contains methane, a potent GHG. Utilizing LFG as a fuel greatly reduces GHG emissions by converting methane to carbon dioxide (the GHG potency of methane is more than 20 times that of carbon dioxide). Fourth, landfills already exist, eliminating the political and economic difficulties associated with site development and new energy production infrastructure. Last, and perhaps most important, financially viable LFGE projects can provide an additional source of revenue to landfill owners.
However, the development of financially viable LFGE projects at small sites is impeded by several factors. First and foremost, most small landfills are not subject to Title V air permitting rules and therefore are not required to install active landfill gas collection systems. However, landfill owners are experiencing mounting pressure from regulatory and environmental groups to reduce GHG emissions.
The primary challenge to the installation of an active LFG collection system is the initial capital cost. However, through early planning, installation and operation of landfill gas collection systems can be an attractive investment for landfill owners through the sale of carbon credits and development of renewable energy projects.
A review of the major capital cost components of a LFG collection system indicates the most costly system components are the blower/flare station, header piping and extraction wells. However, Subtitle D regulations call for the installation of LFG vents to ensure cap integrity. Therefore, the costs associated with vent installation will be incurred by the landfill owners anyway and should be considered a sunk cost with respect to LFGE projects.
A second key challenge is ensuring sufficient LFG flows to support a beneficial use project. Though LFG production continues at landfills for an extended period of time after closure, the amount of time when a landfill is producing LFG sufficient for beneficial use is finite. Therefore, landfill owners should consider the combined use of horizontal and vertical collection wells. Horizontal collection wells can be utilized to extract LFG sooner from active areas of the landfill. Once these areas of the landfill reach final grades, vertical wells should be installed.
A final component of the beneficial use of LFG at small landfills is gas system operation and maintenance. One under-performing extraction well in a small system can have significant effects on the quantity and quality of recovered LFG. Given the relatively low LFG flow rates at small sites, ensuring each well is performing optimally is key to the success of the project. Routine balancing and inspection of the gas system will help to maintain the quality and quantity of recovered LFG. Owners also will be able to identify issues, such as settlement, equipment condition and cover material condition.
Once the LFG collection system has been installed, the development of financially viable LFGE projects at small sites is challenging for several reasons. First, capital is currently difficult to come by. Second, the power generation equipment market is primarily focused on large capacity equipment. For small sites, commercially available power generation equipment is limited to microturbines and internal combustion engine-driven generator sets manufactured by Waukesha and GE Jenbacher. Although Caterpillar and Cummins both manufacture internal combustion engines for LFG-fueled power generation, their smallest LFG-rated generator sets require more than 350 scfm LFG for full power production. Third, the value of electrical power is currently depressed with respect to power value peaks in 2008. For example, the average value of power sold into to the PJM American Electric Power Zone in was $54.79 per megawatt hour (MWH) during the first ten months of 2008. The value of power in the same PJM zone was $38.30 per MWH during the first 10 months of 2010.
Developing a successful LFGE project at small sites requires maximizing the value received from power production as well as minimizing capital and operating costs. Blacksburg, Va.-based Green kW Energy Inc. recently opened a 340 kW LFGE project at the Mid-County Landfill in Christiansburg, Va. The landfill is owned and operated by the Montgomery Regional Solid Waste Authority (MRSWA). The landfill opened in 1982 and closed 15 years later with 1 million tons of waste in place. A LFG collection system and flare have been in operation since 1998, although they are not required by rule. Current LFG flow rate is 200 scfm with approximately 47 percent methane. Power is produced using two generator sets, one a 265 kilowatt (kW) unit powered by a Waukesha engine and the other 75 kW unit powered by an industrial engine. LFG sulfur and siloxane concentrations are relatively low, and gas treatment is minimal. Cost containment and the power sales approach are the keys to this project’s financial viability.
In order to be operationally successful a LFGE project must be safe, environmentally compliant, reliable and aesthetically pleasing. Cutting costs by eliminating safeguards or by using inferior equipment or facilities would result in a project that fell short of these objectives. Cost reductions at MRSWA were not achieved through deploying novel technologies but through a focus on efficiency and simplicity with respect to the LFGE process as well as the project team structure.
The most significant cost reduction was achieved by keeping the project team small. The four-member project team consisted of three engineers and one pipefitter/fabricator/welder. Although the building construction and electrical infrastructure work was contracted to others, all critical functions such as process design, permitting, fabrication, equipment installation and commissioning were performed by team members. By keeping all critical functions in-house, the LFGE process was constructed efficiently in terms of both materials and time. The amount of time it took to get from groundbreaking to the start of operations was 11 months. An additional benefit of all team-members having a hands-on role in design and construction was that opportunities to improve the process that were identified during construction were seamlessly integrated into the final product. A reasonable rule of the thumb is that large organizations have large overhead rates. Revenues from LFGE projects at small sites are insufficient to pay for sales, management and administrative functions.
Other cost reductions were achieved by sourcing materials and contractors locally and by acquiring equipment through eBay. Through the site, the project team was able to acquire new equipment at not only a lower cost but in much less time. A few examples were solenoid gas valves, pressure regulators and high-amperage circuit breakers. None of these items were in any way a compromise but represent the best equipment available for this particular application and were delivered within one week after the purchase was made.
When it comes to collecting revenue from a LFGE project, the simplest approach is to sell power directly to the local power distribution company though a power purchase agreement. Renewable Energy Credits (RECs) may or may not be included in the power purchase agreement. If not, RECs can be marketed using other means. Brokerage companies can perform this function or RECs can be marketed directly through services offered by Regional Transmission Organizations (RTOs) or Independent System Operators (ISOs). The MRSWA facility is located in PJM’s RTO territory. PJM offers the Generator Attribute Tracking System (GATS) service that efficiently organizes a marketplace for buyers and sellers of RECs in Delaware, Maryland, New Jersey, Ohio, Pennsylvania, Virginia, Washington, D.C., and West Virginia.
Although selling power to the local distribution company is relatively straightforward, other potentially attractive power sales options exist. Net-metering is likely the most attractive alternative depending on the rules in place within the state in which the LFGE project is located. Net-metering allows power produced to be used to offset power consumed, resulting in power valuation at or nearly at retail rates.
Using a small, versatile, and efficient project team focused on project functionality and aesthetics, it is possible to build and operate financially viable LFGE projects at small sites. Keeping LFGE processes as simple as possible, much of the skills and materials required to build, operate and maintain the process can be sourced locally. Keeping the necessary work close to home benefits local communities and economies beyond the broader positive environmental impacts. Not only can LFGE projects at small sites reduce GHG emissions and be a source of sustainable energy, these projects can be drivers for increasing employment opportunities and economic growth in small communities.
Steven Cox is an engineer with Green kW Energy, which constructs and operates green power generation systems. He can be reached at (540) 239-5954. Brian Stuver is a project engineer with Joyce Engineering Inc. He can be reached at (804) 355-4520.