Civic

County Plans for Future Waste

Buncombe County’s schematic of how greenhouse methane is collected, combusted, and used to power homes.

AshevilleDane Pedersen, Buncombe County’s solid waste director, suggested the county’s bioreactor may, in a matter of years, need to be decommissioned. The system is working well; the question is at what point will the commissioners determine it is not worth the costs of operation. The bioreactor was installed in 2012 as part of an EPA experiment, Project XL, with a $4 million stimulus grant and loan. The technology, as exotic as it is, had already been established. It was the landfill liner that interested the EPA.

What has been named the Gas to Energy Project is a system for collecting the greenhouse gas methane, which emanates from the garbage in the landfill. Rather than storing it like nuclear waste, the county combusts it into chemicals deemed more benign, and, in the process, it fuels a generator, which supplies electricity to the grid.

To increase the rate of methane emission, the county injects into the waste piles a chemical slurry called leachate that accelerates the decomposition of organic compounds. Wells were drilled into the waste to collect methane emissions. These feed into a pipeline where a vacuum/blower system moves the gas through a conditioner and into a V20, 62-liter generator engine, where it is combusted, instead of allowing it to drift into the atmosphere. The generator was rated at 1.4 megawatts, or sufficient to power 1,100 homes.

Besides being good for the environment, the system was supposed to be a source of revenue for the county, which would sell the electricity generated to Duke Energy and the French Broad Electric Membership Corporation for about $600,000 a year. Additionally, renewable energy credits were expected to run around $200,000 annually. Even though the project has only generated enough to satisfy the needs of 600-700 households each year, it is still considered a success.

Pedersen came before the commissioners to let them know the county’s 10-year contract for selling power to Duke would be expiring in November. Negotiations are underway, but he said it was a given that Duke was going to be paying less for supplying the electricity and less in renewable energy tax credits. Pedersen said for the near future, Duke was more interested in investing in its own alternative energy supplies, at the expense of independent contributors. Other landfill generators across the state were seeing the same trend.

Pedersen showed a graph of historic revenue and expenses with projections through 2026. Six months into the future, expenditures were outpacing revenues and rapidly establishing a budget gap of $125,000 “and counting.” In the past, revenues had exceeded expenditures, on average, by $208,000, with revenues from tax credits and sales to the grid running between $500,000 and $800,000. Pedersen then balanced the financial losses with a few ways the project is forestalling global warming.

He added the county has been discussing the winding-up scene for a long time, and owners of bioreactors across the country are agreeing that the time for contributing to the grid is coming to an end. They, also, are exploring new uses for their methane. In Buncombe, the bioreactor is near neither a large factory for private use nor a utility gas line. The gas has a very slow flow rate, and Pedersen described getting it to the nearest line as “pretty far, snaky” through private property.

While the county continues to explore options, Pedersen said any contracts with Duke would be short-term. For the next few years, though, continuing to use the generator is a sunk cost; the county doesn’t have to spend any money on decommissioning, replacement, or major repairs.

In Other Matters

Pedersen also informed the commissioners that his department would soon be performing a waste stream evaluation with $60,000 spent on a solid waste audit and $40,000 on a composting feasibility study. The last waste study was commissioned by the City of Asheville in 2015, and while the data is still good, it only surveyed residences within the city limits. The new study would encompass the entire county and take into consideration commercial/industrial waste as well as construction waste, which, in light of the boom, has increased substantially.

The reason for conducting another study is landfills have to prepare well in advance for any expansion, as protests, lawsuits, and other forms of obstruction for neighborhood landfills are the rule. It will be even more difficult to site a landfill after 2030, in light of the push to conserve in perpetuity at least 30% of the nation’s land. Pedersen said the reports will make recommendations for diversion strategies and support more intentional organic waste management, which will likely start with a composting pilot project.

In another presentation, Thomas Hartye reported the Metropolitan Sewerage District has been investing in improvements that include a headworks that removes twice as many solids as before; a $17 million high-rate clarification system, which is 90% complete; and a new Carrier Bridge pump station that might include a pedestrian bridge for the Wilma Dykeman Greenway. Thanks to ongoing improvements, the number of times sewage has overflowed before reaching the plant has been reduced to a tenth of turn-of-the-century tallies.

Hartye said the replacement of MSD infrastructure is not straightforward, as it must be built on top of existing operations to ensure continuous, quality service. The MSD has a high rate of capital expenditure, with 30% going to debt service; however, he said, debt service assured future generations would help shoulder the burden of investments that benefitted them.

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