Ecolotree designs, installs, and manages two types of phytoremediation systems:

Ecolotree® Cap (ECap®)

The science behind the Ecolotree® Cap: minimize unwanted water percolation into waste by a "sponge and pump" mechanism. The inputs and outputs shown on the figure are used by Ecolotree to develop hydrologic models and to design site-specific ECaps®.

The Ecolotree® Cap (ECap®) is a crop system that reduces water percolation through the subsurface. The ECap® consists of specially prepared soils planted with fast-growing, deep-rooting trees and understory grasses. The soil pores hold precipitation like a sponge until plant roots can access the water. Plants take up this water for growth and release it into the atmosphere by transpiration.

ECaps® are designed to minimize the volume of water that penetrates into landfill waste or contaminated soils, thus reducing contaminant movement into groundwater and surface waters. Owners are presently using ECaps® to manage water, minimize surface soil erosion, dispose of municipal wastes (biosolids, lawn wastes), sequester greenhouse gases, create wildlife habitat, produce wood fiber, and as community recreation areas. This process is discussed further in a Waste Age Magazine article titled "Not Your Ordinary Cap."

Ecolotree® Buffer (EBuffer®)

The Ecolotree® Buffer (EBuffer®) uses poplar trees and understory grasses to filter sediments and pollutants from groundwater, surface water, and irrigation water. EBuffers® can take the form of a plantation, or are strategically placed as the final filter at streamside or around a site perimeter. They are designed to remove organic and inorganic pollutants in wastewater effluents, contaminated soils, and non-point source pollution. The trees can be managed for biomass yield and harvested for sale as wood and fiber. Additional benefits include erosion prevention, greenhouse gas sequestration, and creation of a visual barrier, windbreak, and wildlife habitat.

EBuffers® are currently being used in the following applications:

  1. Remove or sequester organic solvents, fuels, munitions, and petrochemical spills from impacted soils and groundwater. 
  2. Treat landfill leachate and wastewater treatment plant effluent. 
  3. Clean-up nitrogen spilled at fertilizer manufacturing plants, thus protecting surface and groundwater supplies.
  4. Buffer streams from nutrient, herbicide, and sediment contamination.

Click on each picture below to view a larger image

Before: Ecolotree President Louis Licht planting the first EBuffer® at Amana, Iowa in 1988. This buffer was planted as part of a research study to determine if hybrid poplar trees could be used to protect streams from fertilizer and sediment runoff while growing a commercial crop. After: The same EBuffer® eight years after planting (1996). The trees reduced groundwater nitrate concentrations from 50-100 mg/L to < 5 mg/L, and grew to over 40 feet tall in eight years. After: Root system developed after seven years (1995), extending to a depth of 7 feet.

Locations 

There are currently more than 60 installed ECap® and EBuffer® systems across the United States, plus one in Slovenia. The U.S. sites range from Oregon to New Hampshire, from upper Michigan to Florida. Besides these installed sites, Ecolotree has also been involved in numerous feasibility studies and research projects funded by public and private agencies.

Application Example #1: Landfills and Lagoons

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Before: A construction debris landfill cell at Lakeside Reclamation Landfill in Beaverton, Oregon, April, 1990. After: The same landfill cell 5 years after planting the ECap® (August, 1995). The trees displayed over 7 feet of growth per year. After: Lakeside Reclamation Landfill in 1997, 7 years after planting the ECap®. The trees presently stand 60-80 feet tall, and the owner has achieved regulatory approval to proceed with an ECap® cover over the remainder of the landfill for final closure.

ECaps® are used at landfills and lagoons to prevent precipitation from penetrating into waste, which can result in leachate formation. ECaps® pump water from the cover soils, thus dehydrating the soil during the growing season and creating water storage capacity for the dormant winter months.  This system can typically be installed and maintained at significantly less cost as compared to prescriptive landfill covers. 

ECaps® have been installed as alternative covers over landfills at 13 sites in nine states. Applications include pre-Subtitle D landfills, Subtitle D demonstrations, a construction debris landfill, and a landfill on the Superfund National Priorities List.  Additional information is provided in the articles Landfill Capping With Woodland Ecosystems (please be patient, this will take a few moments to download), Evapotranspirative Tree Caps, and Not Your Ordinary Cap.

EBuffers® are also used at landfills to intercept leachate and contaminated groundwater. The trees can reduce the mass of contaminants flowing from a site and enhance their natural attenuation by hydraulically slowing down or reverting groundwater flow. EBuffers® have been installed at nine landfills in four states.

Application Example #2: Organic Chemical Contaminated Sites

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Before: A contaminant source area at the Ashland, Inc.  facility in Milwaukee, Wisconsin. Historic accidental spills resulted in soil and groundwater contamination with petroleum-related organics, PAHs, and chlorinated organics. During: Ecolotree project manager Eric Aitchison displaying a 13-foot tall hybrid poplar tree used for deep planting at the site. An aeration system injects air at 10 feet below ground via the PVC piping attached to the tree. After: The contaminant source area in August 2002, two years after planting 485 hybrid poplar trees to intercept contaminated ground water and to remove vadose-zone After: The contaminant source area in August 2002, two years after planting 485 hybrid poplar trees to intercept contaminated ground water and to remove vadose-zone contaminants. The trees have tripled in height (up to 15 feet of growth in two seasons), and the roots currently tap into groundwater at depths of up to 10 feet below ground. Phytoremediation appears to have enhanced natural attenuation at the site, substantially reducing the half-lives of petroleum and chlorinated contaminates.

EBuffers®  are used to remediate soil and groundwater contaminated with organic chemicals, such as gasoline compounds, chlorinated solvents, and PAHs.  Extensive research at field installations, government laboratories, and over 20 universities across the U.S. and Canada has shown that poplar trees can clean up numerous organic and inorganic pollutants (see the Phyto Links page for references). Poplars also develop deep, dense root systems that can enhance microbial degradation of pollutants. The roots secrete carbon-rich exudates, which can act as food for soil microorganisms and increase pollutant sorption. Even if the vegetation cannot remove the pollutants, contaminant mobility can be reduced by hydraulic control and increased sorption.

At the Ashland, Inc. facility in Milwaukee, Wisconsin, historic accidental spills resulted in soil and groundwater contamination with petroleum-related organics, PAHs, and chlorinated organics. Phytoremediation was approved by Wisconsin regulators as the remedial solution. Ashland, RMT, Inc., the USR Corporation, and Ecolotree designed and installed (May, 2000) a 485 tree ECap®/EBuffer® using 10-15 foot tall hybrid poplar trees buried up to 10 feet below the surface and a substance aeration system (to encourage deep rooting into groundwater).  Monitoring at the site includes continual depth to groundwater measurements, groundwater and soil testing for residual organics, data-logged soil moisture sensors, subsurface root observation tubes, and leaf nutrient analysis. Results to date include the following: 

  • Tree survival: 88% initially, 99% after replanting phytotoxic areas
  • Tree growth: tripled in height since planting, up to 15 feet of growth in two growing seasons
  • Root growth: extensive and deep, up to 10 feet below the surface and 4 feet horizontally
  • Subsurface aeration: has increased oxygen concentrations in soil from 5% to 15%
  • Groundwater uptake: water table depression observed during growing season, indicating uptake of contaminated groundwater
  • Contaminant removal: phytoremediation appears to be enhancing natural attenuation in groundwater, with a significant reduction in the half-life of petroleum-related organics and chlorinated solvents

Please download Ashland Site Project Summary for additional information about the award-winning Ashland project. 

Application Example #3: Wastewater and Leachate Treatment

Before: Between 7 to 12 million gallons of leachate were irrigated annually from this collection pond at the Riverbend Landfill (McMinnville, OR) onto a 14-acre EBuffer® (at left) After: The trees have effectively treated the leachate while protecting groundwater supplies. Worms drag leaves into the soil, thereby increasing the soil organic matter, sorption potential, and biological activity.

EBuffers® can adsorb, take up, and metabolize priority pollutants from the following wastewater sources:

  • Municipal wastewater 
  • Industrial process wastewater 
  • Landfill leachate and surface water drainage 

Wastewater and leachate can be irrigated onto vegetation by spray, drip, or "big gun" irrigation systems. The vegetation takes up a significant portion of the water, thus providing a wastewater sink. Contaminants, such as ammonium, nitrate, BOD, and BTEX compounds, are removed by 1) direct uptake into plants, 2) sorption to roots and soil organic matter, and 3) enhanced microbial degradation in the root zone. Irrigation rates can be adjusted to ensure that the desired performance standards are achieved.

Application Example #4: Agrochemical Sites

A 4-year old EBuffer® at a fertilizer and herbicide spill site in Illinois.
The trees currently stand approximately 25 feet tall.

ECaps® and EBuffers® can be used to contain plumes and to clean up sites where spillage of fertilizer, herbicides, or pesticides has taken place. These sites are typically agriculture supply dealerships or fertilizer manufacturing plants. The primary contaminants can include ammonium, nitrate, alachlor, and atrazine. Hybrid poplars and grasses remove these contaminants by the following mechanisms:

  1. Direct uptake and incorporation into plant tissue.
  2. Enhanced microbial degradation by root-associated microorganisms.
  3. Increased humification, which encourages nitrogen tie-up in humus.

An EBuffer® was installed in April 1999 at a fertilizer and herbicide contaminated site in Illinois. The buffer was installed to remove nitrogen and herbicides from near-surface (4-6 feet) groundwater, as well as to potentially slow down groundwater flow from the site. Typical groundwater concentrations at the site were 20-200 mg/L nitrogen (nitrate and nitrite) and 0.1-3 mg/L alachlor. A total of 440 12-18 foot tall bare-root hybrid poplar trees were planted into 6 foot deep trenches. The trees grew 15 feet in the 17 months following planting, and appear to have taken up a significant volume of groundwater. Only 6,000 gallons of groundwater were obtained from an on-site recovery well in 2000, compared to 16-23,000 gallons per year for 1996-1999 (the site received 34 inches of precipitation fell in 2000, which is average for this area). Approximately 12,000 gallons of groundwater was recovered in 2002. Nitrate concentrations have decreased since phytoremediation installation.

Application Example #5: Site Perimeters

EBuffers® can be utilized as perimeters around sites such as landfills and animal feedlots for the following applications:

  • Intercept wind-blown waste
  • Intercept and absorb odors
  • Windbreaks
  • Visual screens
  • Sound barriers

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