JOE KNOWS! BiosolidsApril 2, 2018
Understanding Biosolids and How Their Presence in Soil Enhances Turf!
by Joe Marchinchin, Agronomist, R&D, Turf Care Supply Corp.
What are Biosolids?
Biosolids are nutrient-rich organic residues left over from the treatment of animal waste, most commonly harvested from sewage sludge at waste water treatment plants. Much in the way manure is applied to farmland, biosolids are an environmentally friendly solution to the disposal of human and animal waste products. When properly treated and processed, biosolids can enhance the fertility of soils and encourage plant growth.
What forms do Biosolids come in?
Biosolids come in a variety of forms, varying in size, shape, color, odor, and handling. In terms of odor (foremost on most minds), while some biosolids exhibit that classic sulfurous odor, many biosolids have no foul odor at all. Those biosolids, when completely processed, resemble the look and feel of potting soil. Other biosolids come in pelletized or powder form so that they can easily be mixed or coated with/onto fertilizer granules.
Biosolids are divided into 3 classes: Class B, Class A, and Class A-EQ (exception quality). Class A Biosolids are held to a much higher standard; they are generally cleaner appearing, more processed, and have little to no odor. Class A vs. Class B biosolids differ in 1.) the way treated sludge is processed and stabilized, 2.) the physical characteristics of the biosolid end products, and 3.) the markets for which each end product is permitted to be sold (without application restrictions). In general, Class B biosolids are limited to agricultural use, disposal in a landfill, or incineration. Unlike most Class B biosolids, Class A biosolids may be used by citrus growers, nurseries, and sod farms, but are more commonly used by golf courses, landscapers, and homeowners on residential turf.
Quality Control (odor, pathogens, etc.)
Regardless of their various fates, biosolids are held to certain standards before being released into environment. Because biosolids pose multiple environmental hazards prior to treatment, all biosolids (regardless of class) are purified and monitored for heavy metal and pathogen content. Class B biosolids are restricted to only agricultural and landfill disposal. Because of this, EPA and state regulatory agencies require local waste water treatment plants to take appropriate steps to monitor heavy metal content and significantly reduce levels of key pathogens.
Conversely, because Class A biosolids have unrestricted use (in terms of where they can be used, NOT in terms of application rate), EPA and state regulatory agencies are much stricter regarding quality control. Class A biosolids must meet fecal coliform and salmonella pathogen standards and have regulated time/temp and pH/temp monitoring. With Class A-EQ biosolids, extremely low heavy metal limits are imposed (general Class A standards must also still be met). State and local regulatory departments may also have certain odor and handling standards which must be achieved before these products may be marketed, sold, or disposed of.
How Biosolids Enhance Turf and Other Plants?
Biosolids are generally an environmental friendly source of N-P-K nutrients (when applied at the recommended application rate), allowing the user to apply less synthetic N-P-K fertilizer to the soil. Biosolids are a safe, excellent source of organic material which can be used to enhance soil structure and increase a soil’s water holding capacity. Biosolids have been proven to increase macro and micronutrient uptake in plants, as well as amend low-fertility soils. Biosolids contain significantly fewer pathogens than straight animal manure so they are generally a healthier organic fertilizer choice for turf, ornamentals, and vegetable gardens.
From an analysis standpoint, biosolids are relatively low in nutrients compared to synthetic fertilizers, however much of the benefit to plants comes from the infusion of organic material into soils, not just N-P-K counts. Organic matter (partially biodegraded cellular material) can chelate micronutrients in the soil and increase the soil’s water holding capacity. Some biosolids also contain trace micronutrients such as iron, magnesium and manganese. A typical biosolid analysis looks something like this:
Application restrictions (federal, state, and local)
Each state and municipality has its own rules and restrictions regarding the application of biosolids on different land types (farmland vs. residential lawn, etc.). Many states also restrict the amount of phosphorus that can be applied due to the risk of waterway contamination (leading to toxic algal blooms). Before purchasing pelletized biosolids or fertilizers mixed with biosolids, check with federal, state and local authorities to ensure that biosolids are permitted for use in your area. When applying, make sure to follow the instructions on the label. Ensure you do not exceed application rate restrictions.