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Cutting the cost of soil erosion


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Soil erosion -- the impact of rain/irrigation water running across unprotected soil -- doesn't just scar the landscape. That runoff carries sediment and pollutants to surface waters. Mitigating the impacts of erosion cost money. But compost use has been proven to be an effective money-saver compared to more traditional erosion control methods.

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Cutting the cost of soil erosion

  1. 1. Cutting the Cost of Soil Erosion
  2. 2. Soil erosion has been identified as one of the biggest environmental problems facing the world, second only to population growth.
  3. 3. Since natural soil regeneration takes longer than a human lifespan, soil is not considered a renewable resource. Average human lifespan = 79 years Average time to for nature to generate 1 cm of topsoil = 100 years 10 20 30 40 50 60 70 80 90 100 SOURCE: UK House of Commons Environmental Audit Committee
  4. 4. Global erosion costs about $400 billion each year SOURCE: US National Institutes of Health
  5. 5. Soil loss from construction is 10-20 times that of farm land. SOURCE: Journal of Soil and Water Conservation
  6. 6. 60% of lost soils pollute aquatic systems with nutrients, pesticides and other contaminants SOURCE: Soil management techniques to improve green stormwater infrastructure
  7. 7. 850 billion gallons of untreated water are discharged into U.S. waters annually SOURCE: Environmental Health Perspectives
  8. 8. As much as 90% of city surfaces are impervious, resulting in 5 billion tons of topsoil lost each year to erosion SOURCE: NCSU Water Resources Research Institute
  9. 9. Runoff from unstablized construction sites can result in 35-45 tons of sediment per acre per year SOURCE: WeatherBuild
  10. 10. In addition to sediment, runoff can include nutrients, heavy metals, petroleum hydrocarbons and harmful bacteria.
  11. 11. It’s usually easier and cheaper to prevent erosion than control sediment from leaving the construction site. SOURCE: US EPA
  12. 12. Cost of soil erosion per ton SOURCE D. Pimentel et al. 1995, SCIENCE, Vol.267:1117-1123. *Represents 1995 dollars adjusted for inflation. Nutrients $5.08/ton Off-site impacts $5.08/ton Water $3.39/ton $5 $10 $15 Nutrients $3/ton Off-site impacts $3/ton Water $2/ton 1995 dollars 2020 dollars*
  13. 13. Soils with good infiltration and permeability cut stormwater runoff rates and volumes, reducing sediment and nutrient loss.
  14. 14. That’s why compost use tops other stormwater management strategies.
  15. 15. Compost beats: • Straw and tack • Hydro-seeding/hydro-mulching • Fiber mulch • Silt fence • Wood chips
  16. 16. Compare to wood chips
  17. 17. Compare soil loss reduction Compost application compared to bare soils Compost application compared to silt fence Reduced soil loss by 86% Reduced soil loss by 99% Compost application compared to hydroseeding Reduced soil loss by 38% SOURCE: University of Georgia Extension
  18. 18. Compost functions much like a coffee filter to trap sediment and pollutants.
  19. 19. Once incorporated into soil, compost can increase filtration up to 125%. SOURCE: UGA Cooperative Extension
  20. 20. Standards for erosion control compost Compost blanket Compost berm SOURCE: University of Georgia Extension
  21. 21. The importance of particle size Fine compost penetrates soil surface and increases infiltration and water-holding capacity. SOURCE: University of Georgia Extension Coarse compost helps prevent splashing, is less likely to be disturbed by rainfall and runoff, and catches soil particles already in motion.
  22. 22. The importance of moisture content Drier compost absorbs more water and binds more pollutants. SOURCE: University of Georgia Extension
  23. 23. But compost that is too dry is difficult to apply.
  24. 24. Compost that is too wet can be more expensive to buy and transport.
  25. 25. Ideal moisture content for finished compost is 40-50% .
  26. 26. The importance of organic matter Organic matter, the percentage of carbon-based components, is a basic building block of soil. SOURCE: University of Georgia Extension
  27. 27. Compost use increases soil organic matter
  28. 28. A 1% increase in soil organic matter results in 25,000 more gallons of available soil water per acre SOURCE: USDA Forest Service
  29. 29. The importance of pH pH affects ion availability and impacts adsorption or precipitation of some metals. Increasing pH can lower accumulation of metals in plant tissues. Shoot for pH levels close to 7.0, except for acid-loving plants. SOURCES: University of Georgia Extension and Soil Amendments and Environmental Quality
  30. 30. The importance of soluble salt content Salts affect the medium’s ability to conduct electrical current, which impacts cation exchange capacity and plant nutrition. 4.0 mmhos/cm is ideal for horticulture. SOURCE: University of Georgia Extension
  31. 31. The importance of low inerts “Inerts” are contaminants like glass, plastic and metal. They can cause problems in both processing and compost use. Don’t exceed 1.5% by dry weight. Under 1.0% is preferable. SOURCE: University of Georgia Extension
  32. 32. The importance of nutrient content Plants require nutrition. Compost delivers both macro and micro nutrients and holds them at the application site. Use less synthetic fertilizer; reduce polluted runoff.
  33. 33. The importance of stability & maturity Unstable and immature compost can rob plants of nitrogen and cause damage. Stable compost will not generate odor or heat. NSOURCE: University of Georgia Extension
  34. 34. Application rates – compost blankets 1-3 inches depth (135 to 400 cubic yards per acre) depending on slope. Gradual slopes require as little as 3/4 inch or 100 cubic yards per acre. SOURCE: University of Georgia Extension
  35. 35. Mixture ratio – compost blankets Recommended is a fine grade (1/4 to 1/2-inch screen) mixed with coarse grade (2 to 3-inch screen) at a ratio of 3:1. SOURCE: University of Georgia Extension
  36. 36. Compost blanket absorption SOURCE: The Soil & Water Connection 100% 80% 60% 40% 20% 80% 100% 4-inch rainfall event 3-inch rainfall event
  37. 37. 2-inch compost blanket runoff reductions University study on construction site soils (disturbed, compacted sandy clay loam) SOURCE: The Soil & Water Connection 100% 80% 60% 40% 20% Runoff volume reduced 50% Peak runoff rate reduced 36% Total sediment loads reduced 80% Nitrate- nitrogen loads reduced 88% Total and soluble P reduced 83%
  38. 38. Compare performance SOURCE Compost reduced runoff more over one year than hydroseeding, by 33% and 8% respectively, and reduced total cumulative runoff relative to the control by 55% and 30% respectively.
  39. 39. Mixture ratio – compost filter berms Recommended is a fine grade (1/4 to 1/2- inch screen) mixed with coarse grade (2 to 3-inch screen) at a ratio of 1:1. SOURCE: University of Georgia Extension
  40. 40. Construction – compost filter berms Use where slopes exceed 4:1 gradient. Build windrow-shaped berms 1-2 feet high and 2.5-4 feet wide. Build trapezoidal berms 2 feet high, 2-3 feet wide at the top and 4 feet wide at the base. SOURCE: University of Georgia Extension 2.5-4 ft. 1-2ft. 2ft. 4 ft. 2-3 ft.
  41. 41. Compost filter socks Various study findings: • 50% greater flow-through rate than silt fence without a reduction in sediment removal efficiency • Reduced parking lot stormwater TSS by 99%, chemical oxygen demand by 92%, oil/grease by 74%
  42. 42. Compare cost per gallon stored SOURCE: MMSD Green Infrastructure Plan
  43. 43. One product | Many benefits | Superior results COMPOST WORKS
  44. 44. View more titles in the Talking Compost series at Production costs for this title were underwritten by McGill. Its use is permitted for educational purposes if presented in its entirety and without editing or other alteration. ©McGill Environmental Systems of N.C. Inc. Questions? Call McGill HQ at 919-362-1161 or use a contact form at