Merrell Bros. Solar-Thermal Pasteurization Technology
Solar-Thermal Pasteurization: Turning Biosolids Into Marketable Fertilizer
Overview
Solar-Thermal Pasteurization combines greenhouse technology & oven/belt drying to achieve a Class A product called FloridaGreen. Greenhouses are effective in removing moisture from biosolids when conditions are controlled.
To control the conditions, we fully enclosed our greenhouses (also called pods) and placed ceiling fans inside to stir the air. As we dry the material, we lay it across the floor in the greenhouses and we agitate the material with a tractor and a rotary tiller. The rotary tiller takes the dry, crusted material on the surface and rolls it underneath the wetter, moister material. We stir the biosolids once a day.
The material is transferred from the greenhouses to our processing building with a belt conveyor system. It drops into a stainless-steel hopper. From the hopper, it is conveyed to the top of the oven to begin the process of pasteurization. Material is placed on the top oven belt, called the “Heat Up Chamber.” Making the transition to the lower pasteurization chamber, has a similar approach to the Heat Up Chamber.
The difference is the belt speed will not go faster than 30 minutes from placement to discharge. This allows us to ensure the material reaches pasteurization requirements. Throughout the belt, temperature probes are reading the internal temperature of the material, ensuring it is above 158 degrees Fahrenheit. Upon reaching the end of the belt, material is discharged on a conveyor belt, transferring pasteurized material to a covered fertilizer bunker. In this bunker we have the option to load directly into a trailer or store material for up to 21 days.
Summary
- Fully enclosed greenhouse pods provide controlled drying environments.
- The dewatered material is transferred to an oven and heated to ensure pasteurization.
- The end result is a dried, pelletized Class A biosolid, suitable for use as a fertilizer.
Key Benefits
- Marketable Product: FloridaGreen can be bagged and sold as a Class A fertilizer. Municipalities can either manage the marketing themselves or rely on Merrell Bros. to handle the transportation, bagging, and distribution.
- Energy-Efficient: Harnesses solar energy, reducing operational costs.
- Sustainable: Reduces biosolids volume, creating an eco-friendly solution for waste management.