Lignocellulose Conversion via Liquid Effluent Recycling
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Solution Overview
Problem
Existing processes for converting lignocellulose into organic acids, such as lactic acid, result in low concentration and yield, requiring multiple distillation steps and high enzyme amounts, with severe alkaline pretreatment and large fermentation zones needed.
Innovation Solution
The process involves alkaline pretreatment of lignocellulose with a divalent cation, followed by fermentation, where the liquid effluent is recycled to enhance organic acid concentration and yield, allowing for high-purity magnesium or calcium salt production, reducing enzyme requirements and fermentation zone size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fermentation is performed without liquid effluent recycling, then the process is simpler to operate, but the organic acid concentration and yield are low
Solution Approach 1:
The liquid effluent from the fermentation zone is recycled back to the alkaline pretreatment step and/or fermentation zone, creating a feedback loop that concentrates organic acid by retaining it in the system while allowing solid effluent to be removed. This feedback mechanism continuously accumulates organic acid in the liquid phase, achieving high concentration and yield without requiring complex additional equipment.
2Productivity
If severe alkaline pretreatment and high enzyme amounts are used, then saccharification of lignocellulose is sufficient, but the process cost and capital investment increase
Solution Approach 1:
The recycled liquid effluent contains unconverted fermentable saccharides and active enzymes that are returned to the fermentation zone for continued conversion. This continuous action allows the system to achieve high saccharification efficiency over time without requiring severe initial pretreatment or large enzyme dosages, thereby reducing process costs while maintaining productivity.
3Manufacturing precision
If multiple distillation steps are performed, then ethanol concentration of 96% is obtained, but the process becomes more complex and capital intensive
Solution Approach 1:
The organic acid is selectively extracted from the fermentation broth by recycling the liquid effluent through the alkaline pretreatment step, where it forms a concentrated salt solution. This extraction separates the organic acid from the fermentation mixture early in the process, eliminating the need for multiple subsequent distillation steps to achieve high concentration, thereby simplifying the overall process while maintaining manufacturing precision.
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 approach achieves high concentration and yield of organic acids with reduced distillation steps and lower enzyme usage, making the process economically viable and less capital intensive, suitable for small-scale operations with waste biomass, and allows for efficient recovery of other soluble products like amino acids.
Implementation Method 1
subjecting the pretreated lignocellulose material, in the fermentation zone in the presence of a hydrolytic enzyme and a micro-organism that is able to convert saccharides into an organic acid, to enzymatic hydrolysis and fermentation
Implementation Method 2
subjecting the pretreated lignocellulose material, in the fermentation zone in the presence of a hydrolytic enzyme, to enzymatic hydrolysis
Implementation Method 3
the organic acid is recovered as magnesium or calcium salt from the solid effluent of the fermentation zone
Data Source
AI summary
The invention relates to a process for the conversion of lignocellulose into an organic acid including an alkaline pretreatment step and a fermentation step, wherein liquid phase obtained in the fermentation step is recycled to the alkaline pretreatment step and/or the fermentation step. Organic acid is recovered as its magnesium of calcium salt from solid phase obtained in the fermentation step.