Biosolids Products and Phosphorous Claims

Biosolids Products and Phosphorous Claims State Plant Food Control Officials recognize slowly available phosphate claims in biosolids and other organic recycled products. Many people within the organics recycling industry; including biosolids management companies, are familiar with the concern regarding the over application of phosphorus and/or the migration of phosphorus into our water resources. Obviously, this issue should be taken seriously so we can protect drinking water, reduce surface water contamination (eutrophication), and conserve an important nutrient required for plant growth and food production. There are various forms of phosphorus (P), but most of the P in biosolids-based products (e.g., many cakes, compost, granules) are not in a water extractable. And although they are typically regulated like inorganic P sources, often the lion share of the P in biosolids products is in slowly available form (Table 1). In response to state regulations regarding phosphorus fertilizer usage, the American Association of Plant Food Control Officials (AAPFCO) developed recommended language regarding 'Fertilizer Restrictions for Urban Landscapes,' as well as other related Statements of Uniform Interpretation and Policy to assist states in developing science-based regulation. Unfortunately, many states have been overzealous in their regulation, often 'just going too far' (e.g., almost eliminating even maintenance applications of P on turf), while some have not dealt with more significant causes of nutrient migration, such as over fertilization or manuring on agricultural land, or strict enforcement of NPDES Phase II regulation (sediment control regulation during construction). Further, many states have ignored relevant science, regulating all P sources the same and ignoring their actual availability (mobility). In many of these states, biosolids products are impacted by these regulations, if they make nutrient claims, and sometimes when they don't. Distinguishing Phosphorus in Biosolids and Organic Recycled Products For this reason, an Industry Liaison to AAPFCO (who is a member of the Water Environment Federation and the US Composting Council) researched a means to illustrate the difference between P in biosolids, compost, and other carbon-based products and those found in many inorganic fertilizers. In order to be able to claim that carbon-based products contain lower amounts of water extractable phosphorous (WEP), an acceptable lab method had to exist or be developed. These efforts led to the identification and evaluation of the SERA (Southern Extension & Research Activity) -17 WEP test method, which was originally developed for manure and biosolids. Working with The Pennsylvania State and Colorado State Universities, the WEP test method and a definition for WEP was proposed. The importance of this claim relates not only to the potential negative environmental impacts of highly soluble phosphate sources, but also helps biosolids product customers better manage nutrient addition for proper plant growth. At the July 2021 AAPFCO meeting, the test method for WEP was found to be acceptable, however sampling methods need to be further' fleshed out' and the definition will likely go 'official' at the next AAPFCO meeting (February 2022). The definition for Water extractable phosphorous, as it currently stands is: the amount of phosphate in a carbon-based fertilizer that is readily water soluble, as determined by the SERA (Southern Extension & Research Activity) -17 test method. The final piece of the puzzle was illustrating how testing for the WEP content of biosolids products could be used to make slow-release phosphate claims on fertilizer labels, while following existing labeling regulations and formats. Figure 1 is an example; note that the amount of phosphate that is not water extractable is claimed as slowly available phosphate. After some discussion, it was determined at the AAPFCO meeting that making slowly available phosphate claims for carbon-based products was in fact allowable. Figure 1 1.25-1-0.5 GUARANTEED ANALYSIS Total Nitrogen (N) ...........1.25% 1.0% Water Insoluble Nitrogen* 0.25% Water Soluble Nitrogen Available Phosphate (P2O5)**......1.0% Soluble Potash (K2O)........0.5% Derived from biosolids compost *1.0% Slowly available nitrogen from compost **0.90% Slowly available phosphate from compost How Will Biosolids Managers Use This Option? Now that testing for WEP is considered to be an acceptable means to make slowly available phosphate claims on biosolids products, manufacturers should consider how they will use this new option. Biosolids fertilizer granule and compost producers, who have always known that the lion's share of nitrogen in their product was in slowly available form, can now determine the same about P through a simple test. Perhaps more biosolids managers will register their products as fertilizers, enabling them to make legal fertilizer (nutrient) claims. Companies producing dried and granulated biosolids or manure products, which almost always register them as fertilizers, could easily make the slowly available phosphate claim once testing is completed. In the near-term, biosolids product manufacturers can use this option as follows: - If their biosolids product is already registered as a fertilizer, they can test for WEP and make a new claim. - If they are selling their product to farmers, turf managers and other end users depending on the products nutrient content, this additional testing could assist them in better helping customers manage other nutrients that may be applied along with biosolids product. - It could allow biosolids managers to better defend the use of their products where environmental concerns exist, related to nutrient addition. With WEP test data in hand, it will be important for biosolids managers to discuss P availability to certain customers in a slightly different way, but it may also allow them to make some related environmental claims. For instance, 'The majority of nitrogen and phosphorus in Super Bio-Compost is in 'bound' form and are slowly releasing . These types of nutrients significantly reduce the likelihood of nutrient leaching.' The ability to discuss the fact that the biosolids products typically contain 90% or more slowly available nitrogen and 80% or more slowly available phosphate, could help the industry have more meaningful discussions with environmental regulators, as well as environmentally conscious customers. Going into the future, this labeling breakthrough could open up a dialogue with regulators regarding nutrient addition during the land application of liquid and cake biosolids.