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 deploying the technology at a commercial scale
Pretreatment Process Options
Mechanical Size Reduction
Reduction of particle size is often needed to make material handling easier and to increase the surface/volume ratio. Depending on the feedstock and the process, we can perform size reduction through knife milling or ball milling.
Dilute acid pretreatment primarily breaks the lignin-hemicellulose matrix, hydrolyzes and removes hemicellulose into the aqueous phase, and increases the porosity of the cell walls. This increases the enzymes’ access to the surface of cellulose available in the residual biomass. This treatment is ideally suited for herbaceous biomass and agricultural residues, such as corn stover. However, the risk of corrosion issues requires 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.
In hydrothermal pretreatment, the lignin-hemicellulose matrix is interrupted and hemicellulose is released into the aqueous phase, but mostly in the oligomeric form. To improve conversion yields, it is necessary to enzymatically or chemically hydrolyze the oligomers further. Herbaceous biomass and agricultural residues, such as corn stover, are suitable for this type of pretreatment. However, due to lack of corrosion issues, this pretreatment can be carried out in a stainless steel pressure vessel. Also, fast—but not necessarily rapid—heating and cooling processes are required to minimize the production of inhibitory products.
Alkali pretreatment provides the most effective method for breaking the ester bonds between lignin, hemicellulose, and cellulose and avoids fragmentation of the hemicellulose polymers. The reaction temperatures for this process are usually much lower, at 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.
Certain ionic liquids are considered efficient and “greener” biomass solvents/pretreatment catalysts. They can dissolve large amounts of biomass components in mild conditions, with the possibility of recovering nearly 100% of the ionic liquids used at their initial degree of purity. The dissolution mechanism of ionic liquids results in cellulose that has decreased degree of crystallinity, enabling extremely fast enzymatic hydrolysis. Most ionic liquid pretreatments are feedstock agnostic and can be used for a wide range of feedstock ranging from herbaceous and woody biomass to agricultural residues and municipal solid waste.
Organosolv processes use an organic solvent or mixtures of organic solvents with water, sometimes with a dilute acid, for removal of lignin before enzymatic hydrolysis of the cellulose fraction. In addition to lignin removal, hemicellulose hydrolysis occurs when acid is included in the process, leading to improved enzymatic digestibility of the cellulose fraction. The benefits of Organosolv pretreatment include the production of high-quality lignin and the potential to reduce enzyme cost.