How Solar-Thermal Pasteurization Technology Works
A proven system combining solar greenhouse drying, thermal pasteurization, and pelletization to provide an effective turn key solution for sustainable, long-term biosolids management.How Solar-Thermal Pasteurization Works
Solar-Thermal Pasteurization combines greenhouse drying, controlled thermal pasteurization, pelletization, and product handling into one complete biosolids management system.
The goal is simple: move material from dewatered biosolids to a cleaner, more stable, beneficial-use fertilizer product.
See the full system explained.
In this short overview, Ted Merrell walks through each stage of the Solar-Thermal Pasteurization process and explains how the pieces fit together.
From Wet Cake to Beneficial Reuse
The system is designed as a controlled path. Each stage prepares the material for the next, moving from dewatered biosolids to dried, pasteurized, pelletized fertilizer.
Dewater
Biosolids enter the process after existing dewatering.
Solar Dry
Greenhouse pods use solar energy and controlled airflow.
Pasteurize
Time and temperature are managed for pathogen reduction.
Pelletize
Treated material becomes a uniform fertilizer product.
Reuse
The final product can be stored, loaded, bagged, or distributed.
The Five Major Stages
These stages show how Solar-Thermal Pasteurization works as a complete treatment platform, not a single piece of equipment.
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 biosolids are dewatered, the material can be transferred into the system for drying, pasteurization, and final product production.
Step 2: Solar Greenhouse Drying
Dewatered biosolids are placed inside 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, and daily turning helps break up surface crust and expose wetter material.
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 or Class AA biosolids production. Temperature monitoring and retention time help ensure 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 project-specific support channels.
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.
Controlled treatment for higher-value biosolids outcomes.
The system is designed to help municipalities move beyond basic disposal and toward a treated fertilizer product that can support beneficial reuse.
Thermal Assurance
The pasteurization stage manages time and temperature so the material is treated consistently before final handling or pelletization.
Product Consistency
Drying and pelletization help create a more uniform finished product that is easier to store, handle, transport, and market.
Odor control is designed into the process.
Odor can be one of the biggest public concerns in biosolids management. The process is designed to reduce exposure through enclosure, airflow control, and dedicated odor treatment.
Control begins with containment.
Traditional open-air or minimally controlled biosolids handling can allow odor to become a community problem before the facility has a strong way to respond.
Solar-Thermal Pasteurization uses enclosed buildings and greenhouse pods to help contain odor-bearing air and move it through treatment systems before discharge.
How odor is managed
Enclose the process
Greenhouse pods and process buildings help contain odor-bearing air.
Move and manage the air
High-volume ventilation supports capture, airflow control, and treatment.
Treat before discharge
Odor-control towers and carbon filtration help polish captured air before it leaves the facility.
From Disposal Material to Fertilizer Product
The finished material can be stored, loaded in bulk, bagged, or distributed as a marketable fertilizer product.
This creates a more valuable path for municipalities. Instead of relying only on disposal outlets, communities can move toward beneficial reuse, product handling, and long-term resource recovery.
Bulk Loadout
Material can be loaded for transport and reuse based on the project model.
Bagging
Finished product can be bagged for distribution where the program supports it.
Storage
Covered storage gives operators flexibility between treatment and movement.
Distribution
Product can move through municipal or Merrell Bros. support channels.
Questions This Page Should Answer
Does the system replace the entire wastewater treatment plant?
No. Solar-Thermal Pasteurization is designed to work downstream of existing dewatering infrastructure. Each project is evaluated around the facility’s current process, output, site conditions, odor concerns, and long-term goals.
Why use greenhouse drying before pasteurization?
Greenhouse drying uses solar energy and controlled airflow to reduce moisture before the material enters the pasteurization stage. That helps create a more efficient treatment path.
What does pasteurization add to the process?
Pasteurization provides controlled time and temperature treatment. This helps support pathogen reduction and a higher-quality finished biosolids product.
Why pelletize the finished material?
Pelletization improves appearance, consistency, handling, storage, transport, and marketability. It helps move the product away from waste perception and toward beneficial reuse.
Can municipalities see the system in operation?
Yes. The system is operating in real facilities, and Merrell Bros. can discuss site visit opportunities with municipal leaders, engineers, and utility teams.
Ready to See How It Could Work at Your Facility?
Every wastewater treatment plant is different. Merrell Bros. can help evaluate your current dewatering method, solids volume, site conditions, odor concerns, hauling costs, and long-term goals.
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