The Waste Problem Few People See

Every day, wastewater plants process what cities flush away. Behind this routine service lies a complex and costly challenge: managing biosolids, the organic by-product of wastewater treatment. According to the U.S. Environmental Protection Agency, the United States produces roughly 7.18 million dry tons of biosolids each year. About half of this material has traditionally been applied to land as fertilizer or soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More. For decades, this practice offered a practical way to recycle nutrients and reduce disposal costs. That system is now under strain.

The spread of per- and polyfluoroalkyl substances (PFAS)—often called “forever chemicals”—has altered the landscape of biosolids management. PFAS compounds resist degradation and can accumulate in soils, crops, and livestock. In response to contamination concerns, Maine banned the land application of biosolids in 2023, the first statewide prohibition of its kind in the United States. The consequences extend beyond Maine. Wastewater utilities across the Northeast now face rising costs and limited disposal options. Landfill tipping fees in parts of Massachusetts exceed $100 per ton, and concerns remain about PFAS leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More from landfill sites over time. Utilities must now manage biosolids with fewer outlets, higher liability, and increasing regulatory scrutiny.

PyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More as a Thermal Treatment Option

One technology gaining attention is pyrolysis, a thermal process that heats organic material in the absence of oxygen. When biosolids are exposed to temperatures typically between 400°C and 700°C, the material decomposes into three main products: gas, oil, and a stable carbon rich biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More. Research from institutions such as the University of Maine and the U.S. Department of Agriculture suggests several outcomes relevant to wastewater utilities:

• Significant reduction in biosolid mass, often by up to 90 percent
• Thermal destruction of many organic contaminants
• Generation of energy-rich gases that can be recovered for heat
• Formation of biochar that can store carbon for centuries

Biochar is chemically stable and porous. These properties allow it to retain nutrients such as phosphorus and iron while resisting rapid decomposition in soil. In wastewater management, this means a material once treated as waste may become a durable soil amendment or environmental product.

Regional Experiments in New England

Several municipalities in New England have begun testing pyrolysis as part of their wastewater strategies. These early efforts illustrate how the technology may fit into existing infrastructure.

Greater Lawrence Sanitary District, Massachusetts

The Greater Lawrence Sanitary District (GLSD) launched one of New England’s first municipal biosolids pyrolysis pilots in 2022, with support from the Massachusetts Clean Energy Center. Initial studies examined how thermal conversion affects contaminants and nutrient retention in biosolids. Early findings from research partners indicate:

• High levels of PFAS reduction during thermal treatment
• Biochar yields generally between 20 and 50 percent of the original dry mass
• Retention of phosphorus and iron within the char matrix
• Recovery of heat energy from pyrolysis gases

If scaled, GLSD estimates the facility could avoid disposal of roughly 15,000 tons of biosolids per year while reducing hauling and landfill costs.

Portland, Maine

Portland’s wastewater system faced a rapid policy shift after Maine’s statewide PFAS restrictions. Biosolids previously used on agricultural land had to be transported long distances for disposal, raising annual costs to roughly $1.6 million. In response, regional researchers began studying biosolids pyrolysis as a potential alternative. Laboratory work suggests that the process can significantly reduce PFAS concentrations while producing a carbon-rich biochar that retains phosphorus. Phosphorus recovery has become a strategic concern in wastewater management. Global phosphate reserves are finite, and wastewater streams contain substantial recoverable nutrients. Technologies that stabilize and recycle phosphorus may help utilities convert disposal problems into resource streams.

Burlington, Vermont

In 2024, Burlington began integrating biosolids pyrolysis with the city’s broader climate and waste strategy. The system processes a mixture of municipal biosolids and regional wood waste. Current outputs include:

• Approximately 1,200 tons of biochar per year
• Recovered heat used to assist sludge drying
• A soil amendment sold to farms and landscaping markets

City estimates suggest the process could sequester roughly 2,800 tons of carbon dioxide equivalent annually, comparable to removing several hundred passenger vehicles from the road.

Biochar and Carbon Accounting

Beyond waste reduction, biochar has attracted attention in carbon markets because of its long-term stability in soils. Carbon stored in biochar can remain sequestered for hundreds to thousands of years, depending on production conditions. Several carbon accounting frameworks now recognize biochar systems, including:

• Puro.earth Biochar Carbon Removal (BCR) methodology
• Verra VM0044 methodology

Under these frameworks, verified carbon removal credits can be issued for the stable carbon stored in biochar. Market prices vary but have recently ranged between $120 and $200 per ton of CO₂ equivalent in some voluntary markets. For wastewater utilities, this creates a different financial model. Biosolids treatment—historically a cost center—may generate environmental credits that offset operational expenses.

Why New England Is Moving First

Several regional conditions have accelerated interest in biosolids pyrolysis across New England.

• Regulatory pressure. States such as Maine, Massachusetts, and Vermont have adopted strict PFAS monitoring and management rules. Utilities must now consider treatment methods that reduce chemical risk.
• High disposal costs. Limited landfill capacity and transportation requirements have pushed tipping fees upward. Thermal conversion can reduce the volume of material that must leave a facility.
• Reliable feedstocks. Wastewater plants produce biosolids continuously. In forested regions like northern New England, wood residues can supplement feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More streams and improve process efficiency.

Together, these factors make the region a testing ground for new wastewater technologies.

An Infrastructure Question

Municipal wastewater systems are often slow to change. Facilities operate on long investment cycles, and infrastructure upgrades require regulatory approval and public funding. Yet the pressures surrounding biosolids management—PFAS contamination, landfill constraints, and climate goals—are forcing utilities to reconsider established practices. Pyrolysis is not a universal solution. It requires capital investment, technical oversight, and reliable markets for its products. But early projects in New England show how thermal treatment can address several challenges at once: contaminant reduction, waste volume, nutrient recovery, and carbon storage.

The next few years will determine whether these pilots remain isolated demonstrations or become part of standard wastewater infrastructure. If the technology proves reliable at scale, biosolids may no longer be viewed primarily as waste. Instead, they could become a feedstock for carbon-stable materials that serve agriculture, land restoration, and climate mitigation.