Evaluation of environmental benefits and impacts of compost and industry standard erosion and sediment control measures used in construction activities
Faucette, Lee Britt
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Soil erosion is considered the biggest contributor to nonpoint source pollution in the United States according to the federally mandated National Pollution Discharge Elimination System. Soil loss rates from construction sites are 10-20 times that of agricultural lands. Nearly 70% of the nation’s Municipal Solid Waste is organic material and could be composted if source separated. Georgia leads the nation in poultry production, generating approximately 1.36 metric tons of poultry litter annually in addition to over 1.81 million metric tons per year of food processing waste, 2.26 million metric tons per year of wood waste, and almost 362,000 metric tons per year of municipal biosolids. It is important to divert these materials from landfills by developing off-site uses and markets for these materials. The use of surface applied organic amendments has been shown to reduce runoff and erosion. Four types of compost blankets, hydroseed, silt fence and a bare soil (control) were applied in field test plots. Treatments were seeded with common bermuda grass. A rainfall simulator applied rainfall at an average rate equivalent to the 50 yr/1 hr storm event, and runoff samples were collected and analyzed for solids, nutrients and runoff quantity. Three simulated rain events were conducted: immediately after treatment application, at vegetation establishment, and at vegetation maturity. Vegetative growth and soil quality characteristics were also evaluated. Results showed compost provided a quicker vegetative cover than hydroseed; however, due to weed invasion hydroseed produced the greatest biomass after one year. In the short term, hydroseeding was not very effective at reducing runoff compared to compost, and compost reduced runoff more over time than hydroseeding or a bare soil. Compost showed greater infiltration of rainfall compared to hydroseed. All treatments proved better than the control at reducing solids loss. Total solids loads were as much as 350% greater from the conventional methods compared to the composts during the first storm and as much as 36 times greater during the second storm. Materials high in inorganic N released greater amounts of nitrogen in storm runoff; however, these materials showed reduced N loss over time. Hydroseeding generated higher P concentrations and loads compared to compost in storm runoff, particularly during the first storm. Compost blankets showed increased soil microbial biomass compared to hydroseed treated soils, and increased surface soil total C, compared to bare soils, an indication of improved soil quality. Soils treated with hydroseed experienced elevated levels of soil phosphorus near the surface throughout the study.