District Energy - 2006 Third Quarter

not LMOP-assisted). While this number is impressive, there is still a long way to go. There are still at least 600 U.S. landfills that could economically support a project. These 600 landfills would have a generation capacity of more than 1,400 MW or could supply 356 billion cu ft per year of gas to industrial end-users.

The generation of electricity from landfill gas makes up about two-thirds of the currently operational projects in the United States. Electricity for on-site use, district energy system use or sale to the grid can be generated using a variety of different technologies, including internal combustion engines, turbines, microturbines, Stirling engines (external combustion engines) and Organic Rankine Cycle engines. The vast majority of projects use internal combustion engines or turbines, with microturbine technology being used at smaller landfills and in niche applications. Electricity generation that is not for the grid will often utilize combined heat and power. Directly using landfill gas to offset the use of another fossil fuel is occurring in about one-third of the currently operational projects. This direct use of landfill gas can be in a boiler (e.g. district energy), dryer, kiln, greenhouse or other thermal applications.

Although landfill gas is widely used as fuel to produce electricity and fire boilers, there are differences between using landfill gas and natural gas in these applications. Unlike natural gas, landfill gas is normally saturated with moisture and carries varying quantities of compounds that contain sulfur, chlorine and silicon. Although the constituents in the gas have not deterred successful landfill gas use

in a large number of utilization projects, they do need to be considered in project planning.

Landfill gas systems typically require bulk moisture removal, refrigerated drying and dew-point suppression through a reheat cycle. Moisture removal from the landfill gas is generally greater than 90 percent, depending on the technology used. A method for removal of contaminants, including non-methane organic compounds (NMOCs) and siloxanes, is generally also recommended. Combustion turbines and reciprocating engines have operated with no provisions for contaminant removal. Although there is an increasing list of siloxane and contaminant removal technologies available, carbon adsorption is still the only proven and cost-effective method.

Market Drivers

In the past two years, LMOP has seen increasing interest in utilizing landfill gas, particularly to offset fossil fuel consumption. The interest is fueled by both economic and environmental factors. Energy costs in general have been rising, and energy markets are becoming increasingly volatile. At the time of this writing, the Henry Hub and NYMEX indicators showed the price of natural gas at just over $7/MMBtu, down from $13/MMBtu a few months prior.

Higher prices not only encourage energy users to look for less expensive sources, but they also make project economics more attractive. A perfect example is that high energy prices are making longer pipeline projects not only possible but profitable. Five years ago, a pipeline

project was generally thought to be economically feasible at five miles or less. In 2003, however, BMW Manufacturing developed a landfill gas project at its South Carolina plant that involved the construction of a 10-mile pipeline. In 2004, a Honeywell landfill gas project came on line with a 23-mile pipeline – the longest in the U.S.!

Industrial operations and governments are realizing significant energy cost savings when they use landfill gas. BMW notes that it saves more than $1.0 million per year at its South Carolina plant alone, where it is using landfill gas to generate electricity and capturing waste heat from the turbines for plant operations. The National Aeronautics and Space Administration, the first federal facility to use landfill gas, saves more than $350,000 per year by using landfill gas in place of natural gas in its Maryland

NASA saves more than $350,000
per year by using landfill gas in
its Maryland flight center district
heating system.

flight center district heating system (fig. 1; also see sidebar on p. 9). Prompted by rising energy costs, the University of New Hampshire is also exploring the feasibility of a landfill gas project. The gas would be transported through a 13-mile pipeline for heat and electricity at the university’s cogeneration plant.