A department of Johnson County, KS

Sustainability Opportunities

The opportunities are consistent with the overall County and project goals and also consistent with Johnson County Wastewater’s application of triple bottom line evaluation of projects.

1. The additional solids handling capacity allows solids currently produced at another facility to be treated at the Smith facility thereby reducing miles driven and disposing these solids in the landfill. Solids from the Smith facility are beneficially applied to agricultural land.
2. The haulers of FOG can benefit from shorter haul distances.
3. With the additional solids and FOG, the amount of methane produced by the anaerobic digesters would be significantly increased to the extent that using the methane to produce electricity becomes cost effective.
4. Using the methane in generators would virtually eliminate the flaring of the gas.
5. The electricity produced could be used to operate the plant, reducing the need to purchase the power from the local power company, reducing the load on a coal fired power plant. The Smith facility consumed 15.8 million KWh in the most recent 12 month period at a cost of $967,000.
6. It is anticipated the plant will receive 12,400 gallons of FOG per day as an annual average with a peak day of 30,000 gallons received for a total of 3.2 million gallons of FOG waste processed per year. This is about 75 percent of the FOG generated in Johnson County.
7. It is also anticipated the plant will process 6,700 tons per year of wastewater sludge.
8. The generators are high efficiency and were sized to provide optimal operation for the anticipated operating conditions. These units are combined heat and power units using the heat produced from burning the methane to heat water for digester process heating and building heat. These are also containerized units that do not need to be inside a building, thus reducing capital costs.

As designed, the project includes a fourth anaerobic digester, a methane gas cleaning system, a gas storage sphere, two cogeneration units and a FOG receiving and storage system as the major components. In addition to the anticipated $500,000 per year savings in electric costs, JCW expects a related reduction in carbon footprint of 9,600 metric tons CO 2 eq/yr from not purchasing power off the grid and an additional 100 metric tons CO 2 eq/yr associated with the reduced haul distances for wastewater sludge hauling and FOG haulers. This results from an estimated reduction of 8,000 gallons of fuel from the shorter haul distances.