Composting biosolids has become a crucial practice in resource recovery and environmental stewardship. But how does the process work? What distinguishes biosolids from traditional organic composting? And how can municipalities, businesses, and policymakers better support the responsible use of composted biosolids?
In this interview with Biosolids Consultant Dan Collins, P.E., we explore the science, regulations, and innovations shaping the future of biosolids composting. We discuss the essential parameters that ensure pathogen-free, high-quality compost and the latest technological advancements that reduce processing time and environmental impact. This discussion covers everything you need to know about utilizing biosolids for a healthier planet.
Read on to discover how composted biosolids improve soil health, contribute to carbon sequestration, and play a vital role in sustainable land management while addressing common challenges and misconceptions.
Can you walk us through the composting process for biosolids and explain how it differs from traditional organic composting?
Dan: Biosolids are dense and typically high in nitrogen, requiring a proper blend with a carbon additive. Wood chips are a preferred additive feedstock, providing the necessary porosity for adequate airflow throughout the mix, creating an atmosphere ideal for the microbes. However, determining an appropriate blend of biosolids to additives takes a bit of calculating due to the moisture content of the biosolids ranging from 12-30% total solids, which is typical. While the range of solids content may be challenging, biosolids, such as plastics, metals, and other debris often found in other organics, are free of physical contamination. Biosolids must be free from many contaminants, such as forever chemicals (PFAS, PFOAS) and pharmaceuticals, before being applied to land to ensure safety.
Biosolids must meet stringent regulations before composting to ensure safe compost is generated for public use. Biosolids must also meet EPA regulations for contaminants, such as metals, pharmaceuticals, and other chemicals, to qualify for land application, even before composting.
Facilities composting "clean" biosolids realize that their product is consistent in percent solids, allowing them to have an efficient program and thus making it easy to create a stable, mature soil amendment.
What are the key parameters—such as temperature, moisture, and retention time—that ensure high-quality and pathogen-free composted biosolids?
Dan: It is essential to create a biosolids mix with the ability to maintain proper aeration to allow for temperatures above 55C to be achieved for a minimum of three consecutive days to kill off pathogens to a Class A level. Maintaining moisture content between 45-60% ensures aerobic conditions are present and allows bacteria and microorganisms to convert the biosolids into compost by consuming nutrients dissolved in the water molecules. Other parameters for composting are PH between 6 and 8 and carbon to nitrogen ratios of 25-35:1. The amount of time to create a stable and mature compost is affected by the composting process chosen. Windrow turning operations typically have a much longer process than in-vessel composting and aerated static pile composting.
SG Advanced Composting™ Technology's primary advantage lies in its ability to maintain optimal conditions automatically. The system has integrated monitoring tools that manage aeration, temperature, and moisture levels in real time, optimizing composting conditions to meet regulatory standards while reducing manual labor and operational costs.
How do composted biosolids contribute to soil health and carbon sequestration, and how do they affect sustainable land management?
Dan: Composted biosolids contribute to soil health and carbon sequestration by adding organic matter to the soil. This improves its water retention capacity, resulting in better plant growth and the ability to remain healthy during droughts. Biosolids are rich in nutrient content such as nitrogen, potassium, phosphorous, and many other macro and micronutrients. Applying composted biosolids to land reduces the need for chemical fertilizers. In addition, the carbon found in composted biosolids is sequestered in the soil, reducing the need for chemical fertilizers. Composted biosolids are a good food source for microbes in the soil before improving microbial activity and the soil's overall health. Applying composted biosolids is a key to sustainability and nutrient recycling.
What are the most important regulations governing biosolids composting, and how can policymakers support responsible and beneficial use?
Dan: The most crucial regulation governing biosolids composting is 40 CFR Part 503, developed by the EPA. https://19january2017snapshot.epa.gov/sites/production/files/2015-06/documents/use_of_composting_for_biosolids_management.pdf
Following the specified regulations and conducting tests to confirm pathogen reduction and that stability and maturity criteria meet USCC standards promotes responsible and advantageous reuse. Policymakers can strive to enact laws ensuring these valuable products, along with many other organic materials, are diverted from landfills. Transforming organics into compost can extend landfill lifespans and enhance soil quality globally. Legislation promoting the use of these compost products on farmland, DOT projects, parks, recreational facilities, and more will significantly influence their application.
What are the biggest challenges—whether regulatory, operational, or public perception—that hinder the adoption of composted biosolids, and how can we address them?
Dan: The challenges in adopting composted biosolids are related to the lack of education on the benefits and proper use of the product. Composted biosolids improve the health of the soil by adding macro and micronutrients, which have slowly been depleted over decades of farming. In addition, composted biosolids enhance the ability of the soil to retain more moisture, reducing flooding. Regulations assist agencies with contaminant-free biosolids to keep the product out of landfills by utilizing them in parks, recreational facilities, golf courses, and other turf applications. Better education and biosolids testing before use to ensure safe application is essential. However, some of the biggest challenges come from poor operations, resulting in poor overall product quality, such as aesthetics, odors, etc. Operations providing an inferior product hurt the entire industry. As the saying goes, "One bad apple spoils the bunch!". An Environmental Management Program for biosolids, such as the EPA's ISO14001 program or the Water Environment Federation's National Biosolids Partnership program, can assist in ensuring that best management practices are followed.
What recent technological innovations or best practices have improved the efficiency and environmental impact of biosolids composting?
Dan: Composting has evolved over the past couple of decades. The three primary methods of biosolids composting, windrow, aerated static pile, and in-vessel technology, have all seen improvements. Aerated technologies have seen changes in many ways. Positive, negative, and reversing air technologies are available with or without biofilters and compost "caps." (Caps refer to a cover that reduces odors, VOC emissions, and greenhouse gases. Caps can be a layer of 12-18 inches of biomass or a semi-permeable membrane cover.)
A semi-permeable membrane cover with positive aeration requires no biofilter, as the cover provides odor control. In-vessel technologies are entirely enclosed, with augers, conveyors, rams, or other devices used to aerate, mix, and move the product to a discharge point.
Other innovations include using real-time oxygen and temperature sensors to improve aeration efficiency and reduce costs. By monitoring conditions in real-time, aeration intervals can be set to create optimal conditions for microbial activity necessary to kill pathogens and reduce the time required to make a nutrient-rich soil amendment.
These technology advancements and others contribute to composting times and better and reduced environmental concerns associated with biosolids processing and utilization.
How can municipalities, businesses, and sustainability advocates better educate the public on the safety and benefits of using composted biosolids in agriculture and landscaping?
Dan: Educational events provide an excellent avenue for the public to see the product and product results while teaching about the product uses in community gardens, parks, etc. Outreach is key to the success of any biosolids program. Educating the public on the safety of adequately created biosolids and biosolids products, such as compost, is essential. By educating the public on the stringent regulations and monitoring of composted biosolids, we are investing in waste reduction, resource recovery, pollution mitigation, and sustainable practices. Public awareness plays a key role in the success of any biosolids program. When the public can see how composting biosolids creates opportunities to keep landscape waste and other organic feedstocks out of landfills, a vision for sustainability and partnership can be realized.
Facilities composting biosolids can benefit from an Environmental Management (EMS) Program. An EMS is a framework for identifying and acting on opportunities to improve environmental performance, regulatory compliance, quality management practices, and relations with interested parties and other stakeholders. In addition, an EMS helps identify critical areas for improvement in efficiencies and overall product creation. Municipalities, businesses, and sustainability advocates can work together through these programs to better educate the public on the safety and benefits of using composted biosolids in agriculture and landscaping.
For more information on the implementation of the Environmental Management Program, please get in touch with Dan Collins. dancollins1224@gmail.com
