Biosolid Pelletization via Solar Pre-Drying and Pasteurization
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Solution Overview
Problem
Current methods for converting biosolids to Class A fertilizer are inefficient, as they fail to achieve high enough temperatures for effective pasteurization and result in high transportation costs due to the volume of water in biosolids, posing environmental and health concerns.
Innovation Solution
A system combining greenhouse pre-drying of biosolids to achieve 60-70% solids content, followed by fueled pasteurization to raise temperatures to at least 70°C for 30 minutes, increasing solids content to 75% to meet EPA standards for pathogen reduction, and subsequent pelletization with optional nutrient addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If biosolids are trucked to rural areas and applied to fields, then disposal is achieved, but transportation costs increase and health concerns arise
Solution Approach 1:
The patent extracts water from biosolids through drying processes (greenhouse drying, drum drying, or flash drying) to concentrate the fertilizer product. This reduces volume by up to 80%, making transportation economically viable and eliminating the need for long-haul trucking to rural areas.
Solution Approach 2:
The patent introduces an intermediate processing step where biosolids are converted to Class A fertilizer through pathogen reduction and drying before distribution. This intermediary transformation changes the product form from bulky wet sludge to concentrated dry fertilizer, enabling local or regional distribution without excessive transportation costs.
2Volume of moving object
If biosolids are incinerated, then volume is reduced, but energy consumption increases and air pollution occurs
Solution Approach 1:
The patent changes the physical state of biosolids from wet to dry through controlled drying processes, achieving volume reduction without combustion. The drying methods (greenhouse, drum, or flash drying) remove water while preserving organic matter, reducing volume by up to 80% without generating air pollutants.
Solution Approach 2:
The patent converts the harmful wet biosolids into a beneficial dry fertilizer product. By removing water and reducing pathogens, the process transforms a waste product that requires expensive disposal into a valuable agricultural resource that can be distributed to farmers.
3Loss of energy
If biosolids are dried to high solids content, then transportation costs decrease, but energy consumption increases
Solution Approach 1:
The patent segments the drying process into multiple stages: initial greenhouse drying (utilizing free solar energy), followed by optional drum drying or flash drying to achieve final solids content. This multi-stage approach distributes energy input across different methods, reducing overall energy costs while achieving high solids content (60-80%).
Solution Approach 2:
The patent performs preliminary drying in greenhouses using solar energy before further processing. This pre-drying reduces moisture content from approximately 80% to 40-50%, lowering the energy burden on subsequent mechanical drying processes and reducing total energy consumption.
4Reliability
If pasteurization temperature is increased to 70°C, then pathogen reduction improves, but energy consumption increases
Solution Approach 1:
The patent performs preliminary pathogen reduction during the drying process itself, where moisture removal and temperature elevation begin eliminating pathogens before the dedicated pasteurization step. This pre-treatment reduces the pathogen load, making the subsequent pasteurization more efficient and requiring less energy to achieve Class A standards.
Solution Approach 2:
The patent integrates pathogen reduction as a continuous process throughout drying and pasteurization, rather than as a separate discrete step. The gradual temperature increase and extended exposure time during drying, followed by maintained temperature during pasteurization, create continuous thermal processing that effectively reduces pathogens while optimizing energy use.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method efficiently reduces biosolid volume, achieves the highest level of pathogen reduction for Class A biosolids, and produces a cost-effective, environmentally friendly fertilizer product that meets regulatory standards, while minimizing transportation costs and environmental impact.
Implementation Method 1
greenhouse pre-drying of the biosolids to achieve 60-70% solids content
Implementation Method 2
fueled pasteurization to raise temperatures to at least 70°C for 30 minutes
Data Source
AI summary
This invention discloses and claims a system comprising greenhouses for receiving biosolids comprising a heated slab and an odor control system; a pasteurization building to receive the biosolids from the greenhouse, at least one pasteurization system comprising heat up belts, a burner fan to heat the biosolids, a pasteurization belt to convey the biosolids through a pasteurization chamber; holding tanks to receive the biosolids and enhancement storage to hold enhancements, a scale and a blender to blend the biosolids with the one or more enhancements, a pellet mill to receive a blended fertilizer, the pellet mill comprising a die to form the blended fertilizer into a pellet and a knife to cut the pellet to a desired length, wherein the pellet mill further comprises a temperature-controlled die operable to control the temperature of the blended fertilizer to promote the formation of the pellets.