The Baltimore/Washington, D.C. Metro area produces about 1.2 million wet tons of biosolids per year from area treatment plants (2002 figures). While much of this material has been applied to agricultural fields in the past or sent out of state, new regulations and the loss of agricultural land to development have required investigating other beneficial uses of biosolids.

Application to native forests has been the dominant use of biosolids since 1987 in King County, Washington, which includes the Pacific Northwest cities of Seattle and Tacoma. Their website, Fertilizing Forests With Biosolids details their program and the positive impacts on forests. Many citizens have negative perceptions and concerns about forest application of biosolids that include those related to health and safety, but these concerns have been addressed in King County by sound education and decades of experience. It is an education approach that should be used with new projects.

The forest land base and the higher population pressures in the Mid-Atlantic area make application of biosolids to native forests more challenging. However, the development of specially designed forest plantations that are engineered to use biosolids as their nutrient base is an approach that has worked well in British Columbia, Canada, and Washington State, and holds promise for our area. The tree of choice is hybrid poplar, a clonal species that is developed from crosses of native cottonwood species, and has the ability to utilize very high amounts of nitrogen and other nutrients. Hybrid poplar-biosolids forest plantation systems hold great promise for utilizing biosolids in high amounts, while producing woody biomass that has utility for many uses.

The Mid-Atlantic Biosolids Association is a professional organization comprised of utilities, businesses and non-government committed to good management of biosolids in the six states of New York, New Jersey, Pennsylvania, Delaware, Maryland and Virginia. Check out their website for what is happening with the use of hybrid poplar-biosolids systems.

A promising technique that utilizes high application rates of biosolids to grow hybrid poplar trees planted on abandoned gravel spoils in southern Maryland is called deep row incorporation with forest trees. Deep row refers to the application of the biosolids in a trench which is immediately covered, eliminating odors and slowing the mineralization process that affects water quality. Hybrid poplar trees are uniquely adapted to this application technique because of their ability to take up large amounts of nitrogen in a short period of time.

Deep row application to grow hybrid poplar trees on gravel spoils is a unique and innovative beneficial-use technique for applying biosolids that solves many of the conventional application problems. The technique has been developed on 49.4 ha (122 ac) site in the Washington, D.C. metro area since 1983 by a private company, ERCO, Inc.

Since 2001, the University of Maryland College of Agriculture and Natural Resources has entered into a public private collaboration with the Washington Suburban Sanitary Commission (WSSC) and ERCO, Inc., a private company. Intensive research has been combined with long-term monitoring data to develop a better understanding of water quality impacts, operational methods, clonal selection, hybrid poplar growth and nutrition, and the factors affecting economics and profitability. There are no indications of nitrate leaching and the tree plantation systems are performing well. Given the large acreage of gravel spoils in the metro area, deep row application has the potential to utilize significant amounts of biosolids produced in the region.

The research is intended to do the following:

• Address the science of reclamation of sand and gravel sites through the use of deep row application of biosolids followed by the planting of hybrid poplar trees to utilize the nutrients in the biosolids over a 6-8 year rotation. Deep row application involves applying biosolids in regularly-spaced trenches that are immediately covered, eliminating odors and minimizing the mineralizing of nitrogen until tree roots provide the oxygen needed for mineralization to occur.
• Use different application rates of biosolids and tree densities to determine the impact on water quality and tree production and other variables over a 3-year period and beyond.
• Provide scientific confirmation that deep row application with trees is a viable alternative on other gravel mine spoils in the Washington, D.C. metro area that lie close to treatment facilities.
• Use natural ecological processes to utilize biosolids in a manner that minimizes odors, water quality impacts, and transport problems, while providing environmental benefits from improved wildlife habitat, and soil improvement on sites with nutritionally dead soils.

To learn more about this research project contact contact Jonathan Kays or Gary Felton.

Fact Sheets
Use of Deep-Row Biosolid Applications to Grow Forest Trees	Fact Sheet PDF
Effect of Deep Row Biosolid Application on Water Quality	Fact Sheet PDF
Five-Year Study Results on Hybrid Poplar Clone Study Using Deep Row Biosolids Incorporation	Fact Sheet PDF
Site Preparation and the Effect of Subsoiling on Survival and Growth of Hybrid Poplar	Fact Sheet PDF
Hypothetical Business Scenario for Deep Row Biosolid Incorporation for a Hybrid Poplar Forestry Operation	Fact Sheet PDF
Project Reports
Annual Report for Period of July 1, 2006 – June 30, 2007 Determination of Optimum Tree Density and Biosolid Application Rate and the Effect on Water Quality and Tree Growth Using the Deep Row Biosolids Incorporation Method	PDF
Three Year Report from January 1, 2002 to December 31, 2004Determination of Optimum Tree Density, Biosolid Application Rate, Water Quality Impacts and Tree Growth Effects Using the Deep Row Biosolids Incorporation Method. (Three year research project report.)	Publication PDF Part 1 PDF Part 2 PDF Part 3
Professional Papers
Felix E., D.R. Tilley, G. Felton & E. Flamino. (2008). Biomass Production of Hybrid Poplar (Populus sp.) Grown on Deep-Trenched Municipal Biosolids. Ecological Engineering, Volume 33, Issue 1, May 2008, Pages 8–14.	PDF
Felton, G.K., D. Maimone, and J.S. Kays. (2008). Nitrogen migration from deep-row biosolids incorporation on a hybrid poplar tree farm. NABEC Paper: 08-051 presented at 2008 NABEC annual meeting, Aberdeen, MD. 35 pp., July 28 - 30, 2008.	PDF
Kays, J. S, G. K. Felton, C. U. Buswell, and E. J. Flamino. (2007). Deep Row Incorporation of Biosolids to Grow Hybrid Poplar Trees on Gravel Spoils in Southern Maryland. Water Practice, Volume 1, Issue 1.	PDF
Buswell, C. U., G. K. Felton, J. S. Kays, and E. J. Flamino. (2006). Water Quality of Deep Row Biosolids Incorporation on a Tree Farm. In Proceedings of the 2006 American Society of Agricultural and Biological Engineers Conference, July 9-12, 2006. Portland, OR.	PDF
Kays, J. S., E. J. Flamino, G. Felton, & P. D. Flamino. (2000). Use of deep-row biosolids applications to grow forest trees: a case study. In C.L. Henry, R.B. Harrison, and R.K. Bastian (Eds.), The Forest Alternative: Principles and Practice of Residuals Use. (pp. 105-110). Seattle, WA: University of Washington College of Forest Resources.	PDF
Kays, J. S. (1999). Deep-Row Application of Biosolids to Grow Forest Crops on Mine Spoils: Potential Utilization for the Baltimore, MD - Washington, D.C. Metro Area. In Proceedings of the Water Environment Federation/Association of Wastewater Operators Joint Residuals and Biosolids Management Conference. January 27-30, 1999. Charlotte, NC: Water Environment Research Federation.	PDF