Combine mining, recycling and cell reuse with an aerobic (bioreactor) landfill, and what do you have? A sustainable landfill, according to its creators, Environmental Control Systems (ECS), Aiken, S.C.
The most significant feature of ECS's patented, sustainable landfill is the rapid “turnover” at which the aerobic landfill degrades and readies waste for an end-use after excavation from the cell. This approach will handle increasing waste volumes, offset construction and permitting costs, significantly reduce methane generation and offsite leachate disposal, and limit the need for landfill closures, according to ECS.
The sustainable landfill process treats waste in a number of landfill cells. These cells occupy only a big enough footprint to manage the annual incoming waste stream. Built closely together, each cell (four or five, depending on the waste characteristics, waste receipt and waste degradation time) will experience different activities in a “rotating” sequence.
The first cell is filled with waste. The next cell has been filled with waste and an aerobic landfill system installed. In the final two (or three) cells, waste either is under aerobic degradation, been stabilized and is under excavation, or being placed in an empty cell again.
During the aerobic phase, landfill leachate, impacted groundwater or another moisture source is pumped into the landfill waste through the temporary landfill cover using vertical wells. Air is simultaneously pumped into the wells, too. This combination of air, moisture, waste and indigenous respiring organisms cause the waste to compost and degrade in-place. Depending on waste characteristics and site conditions, the waste is stabilized (or rendered less of an environmental risk) in 18 to 24 months. This rapid degradation greatly contributes to an economical sustainable landfill.
Because the process is aerobic, landfill gas (LFG) such as methane and nonmethane organic compounds (NMOCs) decreases significantly. Also, as the leachate is collected and recycled through the waste, it is either treated or evaporated through well vents due to the elevated waste mass heat (161 degrees Fahrenheit). In the end, waste pathogens are killed, gas production is minimized, offsite leachate disposal costs have been eliminated, and the organic matter is composted.
After the waste is aerobically degraded, waste analysis determined that approximately 50 percent of the separated matter is a soil/compost mix that can used as daily cover or for agricultural purposes. The remaining percentages (especially plastics) are suitable as feedstock for low-grade plastic wood products or as a fuel source. Any remaining inert materials can be placed in a construction and demolition (C&D) landfill or monocell. In the end, the cell is emptied and rehabilitated, which is significant to establishing a “dirty” waste recycling or reuse scheme.
Also, each time the cell is reused, it can be inspected and repaired if needed. Stronger, longer-lasting liners or floors can be considered because their life-cycle costs will be lower due to repeated use.
The sustainable landfill approach also can be used within the structure of many current federal and state regulations, according to ECS. Many states allow the leachate recirculation into the waste. Also, states such as Florida and Maryland are conducting landfill mining. If NMOCs are low, sustainable landfills may meet Clean Air Act thresholds.
Furthermore, regulatory recycling mandates, many over 25 percent, could be met by the recycling that occurs on the “back-end” of the sustainable landfill. Abandoned landfills that are rehabilitated, either into a sustainable landfill or into commercial property, may become Brownfields sites or have their environmental liability waived.
The most obvious advantage for a sustainable landfill is continued revenue. When a landfill closes, in most cases, revenue stops. But a sustainable landfill's continued revenues fund generations of waste management beyond the landfill's original closure date.
Construction costs and land costs are lower because the site requires only four to five cells. Daily cover soils are not needed because they are reused each cycle. An LFG collection system also is not necessary. Waste stays aerobic for the cell's life, so it does not create large amounts of methane or NMOCs.
Because the evaporative effects of the aerobic landfill create a net leachate loss, offsite treatment isn't needed. The aerobic process in one cell will consume leachate from the other cells.
ECS has demonstrated the aerobic landfill in Georgia, South Carolina and Tennessee. These sites have shown one or more of the following: a 12 percent increase in airspace recovery; a 100 percent reduction in leachate treatment costs due to evaporation; a 90 percent reduction in methane gas generation; rapidly stabilized waste; and reduced environmental liabilities.
ECS provides up-front funding to implement its sustainable approach. The investment return is through increased revenues, lowered operating costs and better environmental protection, according to the company.
Schedule of Operations
- Construct Cell/Complete Construction
- Install & Operate Aerobic System
- Rapidly Stabilize Waste
- Redevelop Cell or Landfill Mining
- Repeat as Necessary
The cycle can be completed in less than two years.