Dane County landfill expansion to increase savings and production

A dumping ground of waste materials is traditionally a site of little regard. However, landfills are now repurposing waste beyond purely disposing of it.  Dane County, Wisconsin, Rodefeld landfill is one example of a site repurposing waste, and has even been considered environmentally innovative by those involved with the project. The landfill site has been converting landfill gas into renewable electricity for over 20 years and is now expanding. The expansion project will double the production of renewable energy while extending the life of the landfill for another 30 years.

The expansion was spurred by the landfill reaching its capacity. A choice had to be made—either build a new landfill, or truck waste to a landfill in another community—both costing taxpayers significantly more money. “It was when our creative public works staff came up with a plan we had not originally thought was possible—to do expansion combined with other techniques to make the site work,” said Joe Parisi, Dane County executive.

The idea of expanding onsite has significant advantages. “Construction of a new landfill would have cost $80 million more than the expansion,” Parisi said. “Trucking the waste would have been much more expensive operationally, not to mention the impact on the environment from vehicle emissions.”

Vehicle emissions also didn’t lend to the county’s focus on an innovative climate change action plan, Parisi said. The environmental innovativeness of the landfill is contributed to multiple factors, according to John Welch, solid waste manager with Dane County Public Works. The site has several stormwater control systems to maximize the amount of stormwater that stays on the site, permeable pavement, native grass plantings, leachate recirculation and a ban or recycling of non-typical items like tires, shingles, construction and demolition waste, yard waste, electronics, etc., Welch said. In addition to these factors and the production of renewable energy, the site has a BioCNG vehicle fueling station, which powers more than 40 vehicles in the county fleet with compressed natural gas (CNG). Biomass Magazine reported last August that the filling station produces a capacity of 250 gasoline equivalent’s (GGE) per day, and increases fuel storage more than six-fold. “The combination of all of these innovations is what sets our landfill apart as a leader in conservation,” Parisi said.

The landfill currently generates $3.3 million in electricity per year, enough to power 4,000 homes, which is purchased by Madison Gas and Electric. The increased landfill capacity will have the ability to produce more than 6 MW of electricity during peak years. It is planned that the expansion will generate energy that will eventually heat the nearby medical examiner’s building and the Dane County highway garage when they are built.

The build out capitalizes on the pilot project at the landfill, which encourages garbage to decay faster. Leachate is the liquid that comes out of garbage. As part of the project, the leachate is collected at the bottom of the landfill and pumped back up into the waste mass.  “This helps keep the waste near its optimal moisture, which helps accelerate the natural decay of waste,” Welch said. “This allows us to control and increase the amount of gas produced during the time that we are most likely to use the landfill gas for beneficial reuse.”

Welch said the process has two major benefits; first it reduces the risk of methane generation once the site is long-closed and second, once the waste settles, more waste can fill in the airspace above the settled waste. “This maximizes the use of the approved landfill footprint, is a responsible land-use and is much more beneficial than building a new landfill for the additional waste,” Welch said.

Additional components of the waste strategy deployed at Dane County’s Rodefeld landfill is a Clean Sweep Facility, which is a year-round household hazardous waste facility for residents and businesses, and a transfer station where construction and demolition material is diverted from the landfill hill to recycling markets.

“Construction is expected to be complete, with the first cell of the expansion approved to receive waste, in December 2014,” Welch said.