F.A.Q.
At Liberty Processing & Soils, LLC. we get questions about our process and product often. Here is a list of the most frequently asked questions & answers, written with the assistance of Herschel A. Elliott, Ph. D., P.E.
01
What are biosolids?
The EPA defines biosolids as “nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility...that can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth.”
The quality of biosolids is defined by the concentrations of certain regulated pollutants, the levels of pathogens (disease-causing organisms like bacteria and viruses), and the potential to attract vectors (rodents, birds, insects).
Biosolids that meet the strictest federal and state requirements for these categories are called “exceptional quality” or "EQ biosolids". EQ biosolids can be applied to land similar to any fertilizer or other soil amendment. The material we produce at Liberty Soils is an EQ biosolids product.
02
What does Liberty do with biosolids?
We receive biosolids from various municipal wastewater treatment plants throughout the Northeastern U.S. for “lime stabilization”. The biosolids are blended with quicklime using industrial size mixing equipment. When biosolids mix with quicklime the temperature and pH increase while drying out the material over the course of 24 hours. The result is a 50% solids soil amendment that is safe and desirable for use as a soil-liming agent with the additional benefits of enhancing soil fertility and organic matter content.
03
How does Liberty's process help the environment?
Three options exist for management of biosolids: land application, landfilling, and incineration. Only land application beneficially recycles the soil-enhancing constituents of biosolids. Landfilling and incineration “waste” these valuable constituents. Applying biosolids to land also adds organic matter to the soil, whereas landfilling and incineration result in conversion of the organic matter to methane and/or carbon dioxide which are greenhouse gases that contribute to global warming. Liberty’s product contains 40% volatile solids which is a measure of the product organic carbon content. Therefore, adding this material to the soil increases the soil carbon pool, which is an important step in fighting climate change. Ideally, if we are going to sequester carbon we don’t want to put it in landfills or burn the material.
04
What tests are performed to ensure product safety?
The product goes through rigorous third-party testing to ensure safety for the environment and human contact. We test for an array of pollutants and trace elements, including arsenic, cadmium, lead, and mercury. We also test for PCBs and pathogens such as salmonella, enteric viruses and helminth ova. Testing requirements are performed in accordance with EPA and PA DEP regulations.
Besides nitrogen, the Liberty product is also tested for other elements important for crop production including phosphorus, potassium, calcium, magnesium, sulfur, sodium, copper, manganese, zinc, and aluminum. Results are evaluated to ensure that levels are adequate to correct deficiencies that might exist in the soil or are not excessive so as to reduce crop yields.
06
What are PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a group of manmade compounds with many industrial and household applications: fire-fighting foams, non-stick cookware, stain-resistant carpets, water repellant clothing, cosmetics, food packaging, dental floss, and paint. Because of their widespread use, PFAS can be found in very small concentrations [parts per trillion (ppt) or part per billion (ppb)] in foods, water supplies, soils, and even human blood. Two of the most harmful PFAS compounds (PFOA and PFOS) have been phased out of usage and replaced by less-toxic compounds. However, because these two compounds are highly resistant to breakdown in the environment, they still need to be regulated in water supplies and waste materials. The EPA is in the process of conducting a risk assessment for PFOA and PFOS in biosolids to determine whether regulation of these compounds is needed. This effort is scheduled to be completed by winter 2024.
05
What tests are performed to ensure product consistency & quality?
We perform third-party testing to verify the ability of the product to optimize soil pH for crop production and enhance soil fertility. These tests include parameters (effective neutralizing value, material fineness) for using the product as a liming material and constituents that will promote plant growth (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, etc).
07
Are PFAS a concern in land application of biosolids?
Until federal standards for PFAS in biosolids are promulgated, a prudent course of action is to distinguish (by analytical testing) between biosolids that have common background levels of PFAS compounds versus biosolids from wastewater treatment plants that are industrially impacted due to discharges from high PFAS sources (certain manufacturing and industrial operations, landfill leachates, fire-training sites). Most states (including Pennsylvania) have no PFAS-related policies regarding land application of biosolids. Michigan does have a comprehensive strategy for addressing land application of biosolids containing PFAS with several regulatory tiers based on the biosolids PFOS concentration. Biosolids containing less than 20 ppb PFOS are deemed to be unimpacted by industrial inputs of PFAS to the wastewater treatment plant. Such biosolids can be land applied without special regulatory restrictions. This value (20 ppb of PFOS) serves as a useful benchmark for defining common background PFAS levels in biosolids.
08
Is there a COVID risk with land applying Liberty product?
There is no evidence that biosolids products are a source for transmission of COVID. COVID is a “fragile” pathogen and, among the classes of microbial pathogens found in wastewater and biosolids, encapsulated viruses (like the COVID coronavirus), are the most susceptible to inactivation by disinfection and environmental stress. COVID is transmitted human-to-human primarily by inhalation of aerosols containing the COVID organism and not by contact with biosolids and biosolids-amended soils. In the unlikely event that COVID organisms were in the biosolids received by Liberty, lime stabilization effectively eliminates viruses. Thus, the Water Environment Federation states that the risk of contracting COVID-19 from EQ (Class A) biosolids is negligible.
09
How can the Liberty product be used in crop production?
The quicklime added in processing the Liberty product makes it useful as an alternative liming material for adjusting the soil pH to levels that are optimum for crop production. Natural processes and fertilizer use raise the acidity of the soil so that soil pH levels are below those needed for maximizing yields of major row crops (pH 6.5-7). However, in contrast to agricultural limestone, the Liberty product also contains nitrogen and other essential nutrients and organic matter which contribute to healthy soils. The following example illustrates the benefits of adding the Liberty product to cropland:
A farmer has a yield goal of 150 bushels of corn grain per acre which requires 160 pounds per acre of plant available nitrogen (PAN). Soil test results indicate 4000 pounds (2 tons) of lime are needed per acre to bring the soil pH up to 7. Instead of purchasing agricultural limestone, the Liberty product can be used to raise the soil pH. The effective neutralizing capacity of the Liberty product is 13.3%, meaning that 15 tons per acre is equivalent to 2 tons per acre of limestone. The PAN of the Liberty product is 8 pounds PAN per ton, so that applying the 15 tons per acre to raise the soil pH will also add 120 (15 tons per acre × 8 pounds PAN per ton) pounds of PAN per acre to the soil. This means that only 40 (instead of 160) pounds per acre of PAN needs to be applied as purchased commercial fertilizer (e.g., urea). So, the Liberty product eliminates the cost of agricultural limestone and significantly reduces the cost of nitrogen fertilizer for growing the corn.
If the cost of urea (46-0-0) was $800 per ton, the use of the Liberty product saves the farmer ~$100 per acre in fertilizer costs.
• 1 Ton Urea = 2,000 lbs 46% Nitrogen (PAN) = 920 lbs PAN / ton
• 120 lbs PAN / acre x (1 ton / 920 lbs. PAN) = 0.1304 tons urea / acre x $800 = $104 / acre
Additional bonuses to using the Liberty product include soil addition of other major nutrients (phosphorus, potassium), secondary nutrients (calcium, magnesium, sulfur), and micronutrients (iron, boron, copper, zinc). The product also has a substantial organic matter content. Increasing soil organic matter promotes soil health by enhancing water-holding capacity, nutrient retention, and soil structure.
10
How does Liberty's product stack? Spread? Smell?
Liberty product stacks 8-10 feet tall. The product spreads nicely. It is best spread using a vertical spreader. The final product has an earthy-chocolately aroma with the occasional hint of ammonia.