LANDFILL: LFGTE Generates Savings

Anne Watson

Even small communities can profit from landfill gas-to-energy projects. At the Salt River Pima-Maricopa Indian Community near Phoenix, collecting landfill gas (LFG) and piping it to a nearby power station has helped to eliminate costly landfill closure expenses and bring in $70,000 annually.

For years, the Pima-Maricopa Indian Community, which comprises the Pima and Maricopa tribes, has operated the Tri-Cities Landfill, the Center Street Landfill and the Salt River Landfill in the East Valley of Phoenix. The 200-acre Tri-Cities landfill accepted waste from the tribal community, Phoenix and East Valley municipalities, and commercial waste before closing in October 1993. But two years after the landfill closed, methane gas began to emit from the site and was killing nearby cotton fields.

To combat the leaking methane, the Pima-Maricopa community, DTE Biomass Energy (DTE), a Michigan-based energy systems firm, and the Salt River Project (SRP), an electric utility in the greater Phoenix Valley, formed a partnership to find a better use for the gas. DTE signed a gas-rights agreement with the community, which required DTE to install and run gas collection systems at each landfill. Today, approximately 1,950 cubic feet per minute of gas per day is collected from the Tri-Cities Landfill and transported to SRP's generating station located nearby.

Working with SRP and DTE, the Native American community has been spared an estimated $4 million in initial expenses to install gas collection systems at the three landfills and $400,000 in annual maintenance and operation expenses. This figure also includes the costs for incrementally installing the gas collection system at the Salt River Landfill as it fills up.

“Essentially, DTE Biomass is taking care of our closure costs,” says Stuart Baker, general manager of landfill operations. Baker estimates that the community will save approximately $15 million.

SRP built the power station for approximately $8 million, which includes the building, equipment, distribution lines and an access road. At the station, the methane is dried, compressed, then used to power five engine/generators that each produce approximately 800 kilowatts per year. The energy made from the generating station costs roughly 6 cents to 7 cents per kilowatt hour, which is twice SRP's average generating power cost.

SRP initially joined the project as part of a $29 million program to fund renewable energy sources in the Phoenix Valley. The utility producer also had an incentive to cut greenhouse gas emissions after it voluntarily signed the federal Climate Challenge Agreement. But joining the partnership did not come without difficulties.

Although only six months were necessary for construction, it took SRP almost four years to gain approval from the Native American community, the Environmental Protection Agency (EPA), Washington, D.C., and the Bureau of Indian Affairs, Washington, D.C., to build its power station on tribal lands.

Unexpected delays occurred when SRP negotiated the lease for building land and distribution lines right-of-way with tribal officials. SRP also had to obtain permission from tribal government design and review subcommittees. Additionally, to receive an OK from the Bureau of Indian Affairs, SRP had to prove that the project would present minimal cultural, biological and environmental impact on the community.

“The biggest [obstacle] was a cultural challenge of learning how to deal with the Indian community” and learning to work within the tribal government system, says Ethel DeMarr, manager of SRP's renewable energy program.

Project delays also threatened DTE's deadlines to qualify for tax subsidies. In the end, DTE did meet its deadlines and was able to expand its fuel supply portfolio. SRP pays DTE for the methane.

“Based on our experience, we learned a lot. We certainly would have a longer planning horizon,” says Curtis Ranger, DTE president.

Nevertheless, the LFGTE project is considered successful, as it produces enough energy to supply 1,000 Phoenix Valley homes for a year.

Based on the facility's size, the Tri-Cities Landfill is expected to produce enough methane for another 10 to 12 years. And as the gas diminishes at the Tri-Cities Landfill, rising LFG levels from the Salt River Landfill will supplement the supply.

Currently, all three parties are negotiating how to run a three-mile pipeline from the Salt River Landfill to the generating station.