Pretreatment
The first step to higher yields.
Pretreatment is a costly yet crucial step in the conversion of biomass to bioproducts, as it increases cellulose accessibility and ensures a high sugar yield. The pretreatment process breaks down lignin or lignin-carbohydrate complex linkages and increases the accessibility of pretreated biomass.
We have developed and successfully applied various pretreatment technologies on biomass to produce alcohols, ketones, lipids, and terpenes.
Getting the Most Value
In developing an optimum pretreatment process, we place importance on:
- The most effective pretreatment catalyst for a given feedstock
- The compatibility of the feedstock-pretreatment catalyst combination
- The possibility of generating co-products, primarily from lignin
- Opex and Capex investments
- Energy requirements for solid-liquid handling, separation, etc.
- Co-product value and residue disposal costs at scale
An Optimum Pretreatment Process
Our capabilities help us design the best process for your specifications:
- A broad range of aqueous phase thermochemical pretreatment processes that are suitable for the widest range of feedstocks
- The ability to combine two or more pretreatment processes to achieve the best results across downstream unit operations
- Careful analysis of factors that will achieve the best process economics
- Meticulous assessment of the feasibility of integrating with downstream technologies and commercial deployment
Pretreatment Process Options
Mechanical Size Reduction
Reducing the size of particulate matter is often needed to make material handling easier and improve the surface/volume ratio. Depending on the feedstock and the process, we can perform size reduction through knife milling or ball milling.
Dilute Acid
Dilute acid pretreatment primarily breaks the lignin-hemicellulose matrix of the biomass, hydrolyzes and removes hemicellulose into the aqueous phase, and increases the porosity of the cell walls. This, in turn, improves the enzymes’ access to the available cellulose surface in the residual biomass. This treatment is ideally suited for herbaceous biomass and agricultural residues, such as corn stover. However, risk of corrosion issues mandates the use of expensive corrosion resistant reactors. Rapid heating and cooling is also required to minimize the production of inhibitory products such as furfural and hydroxymethylfurfural.
Hydrothermal Pretreatment
In hydrothermal pretreatment, the lignin-hemicellulose matrix is disrupted, resulting in the release of hemicellulose into the aqueous phase, but mostly in the oligomeric form. To improve conversion yields, it is necessary to hydrolyze the oligomers further through either enzymatically or chemically. Herbaceous biomass and agricultural residues, such as corn stover, are suitable candidates for this type of pretreatment. The process can be performed in a stainless steel pressure vessel due to the lack of corrosion issues. Also, fast—but not necessarily rapid—heating and cooling processes are required to minimize the production of inhibitory byproducts.
Alkali Pretreatment
Alkali pretreatment provides the most effective method for breaking the ester bonds between lignin, hemicellulose, and cellulose while preserving the integrity of the hemicellulose polymers. The process typically requires lower temperatures, around 120C, but reaction times are much longer, in the order of several hours. Corrosion-resistant metal and rapid heating and cooling are not required for this process.
Ionic Liquid
Ionic liquids have been recognized as highly efficient and environmentally friendly solvents/pretreatment catalysts for biomass pretreatment. They can dissolve large amounts of biomass components in mild conditions, with the potential of near complete recovery at their initial degree of purity. The dissolution mechanism of ionic liquids results in the reduction of cellulose crystallinity, enabling rapid and efficient enzymatic hydrolysis. Most ionic liquid pretreatments are feedstock agnostic and can be used for a wide range of feedstock, including herbaceous and woody biomass, agricultural residues and municipal solid waste.
Organosolv
Organosolv pretreatment is a method for the removal of lignin from biomass before enzymatic hydrolysis of cellulose fractions. It uses organic solvents or a combination of organic solvents and water, sometimes with a dilute acid, to dissolve the lignin. The inclusion of acid in the process results in hemicellulose hydrolysis, improving the digestibility of the cellulose by enzymes. This approach offers several advantages, including the production of high-quality lignin and the potential to reduce enzyme cost.