Solar-Thermal Pasteurization Technology
A proven system combining solar greenhouse drying, thermal pasteurization, and pelletization to provide an effective turn key solution for sustainable, long-term biosolids management.Modern treatment for a changing biosolids landscape
Municipal wastewater facilities are under pressure. Disposal options are shrinking. Landfill capacity is tightening. Regulations are evolving. Odor concerns are growing. Transportation costs are climbing.
Solar-Thermal Pasteurization gives municipalities a better way forward.
Our patented system transforms dewatered biosolids into a stabilized, marketable fertilizer product through controlled solar drying, thermal pasteurization, and final pelletization.
It is not just another treatment method. It is a long-term biosolids management solution.
Biosolids Management Is Getting Harder to Ignore
For many municipalities, biosolids management has become one of the most difficult parts of wastewater operations.
Traditional disposal pathways are becoming less predictable. Landfills are quickly reaching capacity. Disposal costs are rising. Odor complaints are creating public pressure. Regulatory requirements continue to move toward higher levels of treatment, documentation, and accountability.
Disposal Options Are Shrinking
Landfills and other traditional disposal outlets are becoming harder to rely on as capacity continues to shrink while cost, and regulatory pressure increase.
Odor creates public pressure
Open or poorly controlled processes can create odor control issues that are difficult for municipalities to defend, often resulting in outside pressure from the public.
Regulations are tightening
More communities are looking for treatment methods that support higher product quality, better documentation, and long-term compliance in order to stay ahead.
Outdated systems limit flexibility
Lagoon storage, seasonal land application, and older drying methods are leaving municipalities with fewer options as expectations continue to shift.
At the same time, many wastewater treatment plants are operating with older systems that were never designed for today’s cost, compliance, and sustainability expectations.
That leaves utility directors and public works leaders asking the same question:
What is the long-term plan?
Solar-Thermal Pasteurization was developed to answer that question with a practical, scalable system that turns a disposal burden into a marketable product for beneficial reuse.
A Smarter Path From Biosolids to Beneficial Reuse
Our Solar-Thermal Pasteurization system combines the natural drying power of the sun with engineered process control.
Think of stepping into a parked vehicle on a hot summer day. The sunlight passes through the glass, heat builds inside, and the enclosed space becomes significantly warmer than the outside air.
Our greenhouse pods use that same basic principle, but in a controlled industrial environment built for biosolids treatment.
Dewatered biosolids are placed inside enclosed greenhouse structures where solar energy, heated floors, controlled airflow, and daily material agitation remove moisture.
From there, the material moves into a controlled pasteurization process where time and temperature are managed to meet Class AA requirements. The material can then be pelletized into a clean, uniform fertilizer product.
Why this matters: Class AA pasteurization produces material that already meets the strictest existing pathogen, vector-attraction, and metals standards in federal law, with minimal exposure to futher tightening. The process is PFAS-retrofit-ready, so any forthcoming EPA action on PFAS can be absorbed as an additive step at the end of the line, with no stranded capital and no wasted work.
The result is a process that helps municipalities reduce volume, improve odor control, lower hauling expenditures, and create a product with beneficial use.
How solar-thermal pasteurization works
The system is designed as a complete biosolids processing platform that can integrate with existing dewatering infrastructure and move material through a controlled path from wet cake to market-ready fertilizer.
Receive
Dewatered biosolids delivered to enclosed building
Solar dry
Solar-assisted greenhouse drying reduces moisture
Pasteurize
Natural-gas belt dryer at 70°C for 30+ min
Polish air
560,000 CFM treated through activated carbon
Beneficial reuse
Class AA fertilizer product
Step 1: Dewatered Biosolids Enter the System
Many wastewater treatment plants already dewater biosolids using equipment such as belt presses, centrifuges, or screw presses. Solar-Thermal Pasteurization is designed to work downstream of that process.
Once the biosolids are dewatered, the material can be transferred into the Solar-Thermal system for drying, pasteurization, and final product production.
Step 2: Solar Greenhouse Drying
Dewatered biosolids are placed in fully enclosed greenhouse pods where solar energy helps drive moisture out of the material.
Inside the pods, controlled airflow and material agitation help improve drying consistency. Ceiling fans move air through the space. Heated floors can accelerate evaporation. Rotary tilling helps break up surface crust and bring wetter material to the top so it can dry more evenly.
This creates a controlled drying environment that improves moisture reduction while helping manage odor and weather exposure.
Step 3: Controlled Thermal Pasteurization
After solar drying, material is conveyed into the pasteurization system.
This stage uses controlled time and temperature to reduce pathogens and support Class A biosolids production. The material passes through an oven or belt system where temperature monitoring and retention time are managed to ensure the material is treated consistently.
The greenhouse drying stage removes moisture. The pasteurization stage provides thermal assurance.
Step 4: Pelletization
Once treated, the material can be pelletized into a clean, uniform fertilizer product.
Pelletization improves handling, storage, distribution, and marketability. Instead of managing loose biosolids as a disposal material, municipalities can produce a consistent fertilizer product suitable for beneficial reuse.
Step 5: Storage, Loadout, Bagging, and Distribution
The final product can be stored, loaded in bulk, bagged, or distributed through Merrell Bros. support channels depending on the project model.
For municipalities, this changes the conversation.
Instead of asking where biosolids can be disposed of, the conversation becomes how treated material can be reused, marketed, and managed as a product.
Designed to Solve the Problems Municipalities Face Now
Solar-Thermal Pasteurization addresses the full chain of biosolids pressure, from hauling and odor control to landfill reliance, compliance, beneficial reuse, and future planning.
Reduces Hauling Exposure
By removing moisture and reducing volume, the system helps decrease the amount of material that needs to be transported.
Improves Odor Control
Enclosed greenhouse pods and controlled process flow provide a more managed environment than many traditional open-air or lagoon-based approaches.
Supports Regulatory Confidence
Thermal pasteurization provides a controlled path toward Class A biosolids production.
Creates a Marketable Product
Instead of producing a disposal material, the process can create a pelletized fertilizer product for beneficial reuse.
Reduces Dependence on Landfills
The system helps municipalities move away from landfill-dependent strategies and toward resource recovery.
Supports Long-Term Planning
Scalable greenhouse, pasteurization, and pelletization systems can be planned around future growth.
From Costly Disposal to Beneficial Reuse
Traditional biosolids management often leaves municipalities dependent on hauling, landfill capacity, and Class B land application. Solar-Thermal Pasteurization creates a more controlled path toward drying, pasteurization, pelletization, and Class A fertilizer production.
Limited Control
Controlled Resource Recovery
SEE THE SYSTEM IN OPERATION
Solar-Thermal Pasteurization is not a concept on paper. It is operating in real facilities and helping municipalities rethink what biosolids management can become. Merrell Bros. offers opportunities for municipal leaders, engineers, and utility teams to visit operating facilities and see the process firsthand.
Designed to Integrate With Existing Dewatering Infrastructure
Every wastewater treatment plant is different. That is why Solar-Thermal Pasteurization is designed to be evaluated around your facility’s existing process, site conditions, solids output, hauling costs, and long-term goals.
The system can be designed to work downstream of existing dewatering equipment, helping municipalities upgrade their biosolids strategy without replacing the entire treatment plant.
Our team can evaluate:
- Current dewatering method
- Wet tons or dry tons produced
- Hauling and disposal costs
- Available land or facility space
- Odor concerns
- Regulatory goals
- Desired end product
- Potential partnership or ownership model
SEE THE SYSTEM IN OPERATION
Merrell Bros. works with municipalities, counties, utilities, and industrial operators to evaluate the right delivery model for each project.
Depending on the community’s goals, capital structure, and operational needs, Solar-Thermal Pasteurization can be approached through several models.
Flexible Project Models for Municipalities and Utilities
Every community has different goals, infrastructure, budget pressures, and operating needs. Merrell Bros. helps evaluate the right delivery model for each project.
Design and Build Support
For municipalities that want to own and operate the system with Merrell Bros. engineering and implementation support.
Operations Partnership
For communities that want a long-term partner to help manage performance, operations, maintenance, and product handling.
Public Private Partnership
For municipalities seeking a shared investment model that combines public oversight with private-sector innovation, operations, and accountability.
Regional Biosolids Facility
For communities interested in a centralized facility serving multiple wastewater treatment plants or partner municipalities.
Protected Innovation. Proven in the Field.
Solar-Thermal Pasteurization is part of Merrell Bros.’ broader portfolio of patented biosolids treatment and resource recovery technologies.
Our systems are developed by internal R&D and engineering teams focused on solving practical, real-world biosolids challenges for municipalities and industrial operators.
The result is a platform built around performance, scalability, and long-term value.
Patented Innovation. Proven Systems.
Merrell Bros., Inc. currently holds 7 issued U.S. patents with 6 additional patents pending, reflecting our commitment to advancing biosolids technology through real engineering innovation.
These services (or systems/processes/technologies) incorporate proprietary technologies protected by one or more patents or pending patent applications.
Engineered In-House. Proven in the Field.
Our technologies are developed and refined by Merrell Bros.’ internal R&D and engineering teams, who remain at the forefront of responsible, performance-driven biosolids management. Our patented systems reflect continuous advancement in sustainable biosolids treatment and long-term infrastructure performance.
Watch Solar-Thermal Pasteurization in Action
Check out this short video series showing each stage of the process from greenhouse drying to finished fertilizer, with Merrell Bros., Inc. Co-Founder, Ted Merrell.
Are you ready to be at the forefront of sustainable biosolids management?
If your municipality is facing rising disposal costs, landfill pressure, odor concerns, or long-term uncertainty around biosolids management, Solar-Thermal Pasteurization offers a practical path forward.
See the system in operation. Talk with our team. Explore what it could look like at your facility.