Compost FAQ

What are Biosolids?

According to the U.S. Environmental Protection Agency (EPA), “biosolids are nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility. When treated and processed, these residuals can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth.” Some people call biosolids sewage sludge, but the term biosolids are used specifically for treated sewage sludge.

What about heavy metals and chemicals in biosolids?

Because of the Clean Water Act, heavy metals are no longer a problem in sewage sludge. This is because the Clean Water Act helped to reduce heavy metal concentrations in our wastewater system, mostly by strict upstream regulation.

What about pathogens in biosolids?

Established by the Part 503 rule, treatment of biosolids to Class A standards eliminates 99% or more of the pathogens that may exist in sewage sludge.

What are the benefits of using biosolids as a composting feedstock?

There are several characteristics that make biosolids a desireable composting feedstock. Biosolids can be used to balance moisture and are a good source of nitrogen. At our facility, we co-compost biosolids with other waste materials such as yard waste, brush, manure, and clean wood waste to achieve the proper carbon to nitrogen ratio.   

How do biosolids differ from other fertilizers?

Biosolids offer an alternative to chemical or manure-based fertilizers that are often untreated. Pathogen concentrations are much higher in untreated manures than in biosolids. Unlike in biosolids, pathogen concentrations in manures are not strictly regulated. Furthermore, many chemical fertilizers are petroleum-based, which comes at an increased cost for farmers and contributes to the release of greenhouse gas emissions.

Where can I find out more about biosolids regulations?

The federal regulation governing the management of biosolids is 40 CFR part 503 and is based on the 1987 Clean Water Act. Most people will learn the most from this guide that interprets the Part 503 rule,