Pretreatment

Enabling Downstream Success

Our Pretreatment Equipment

The First Step to Higher Yield

Pretreatment is widely classified as the second most expensive unit cost in the conversion of biomass to bio-products. The goal of the pretreatment process is to breakdown lignin and increase the accessibility of the pre-treated biomass to saccharification.

At ABPDU, we take a holistic approach to all unit operations, starting with pretreatment. Our focus is on final yield and product cost. We monitor important factors like the loss of biomass to degradation products and inhibitors generated during the pretreatment process that could reduce fermentation or chemical conversion yields.

Getting the most value

We know that no single pretreatment technology offers 100% conversion of carbohydrates into fermentable sugars. In developing an optimum pretreatment process, we place importance on the following:

  • 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

Biomass and feedstock diversity, high biomass loading, product and chemical recovery, and process integration for scale up compound the challenges of obtaining the highest yielding pretreatment process.

Our many advantages help us to design the best process for your specifications:

  • A broad range of aqueous phase thermochemical pretreatment processes that are suitable for the widest range of biomass and feedstock
  • The ability to combine two or more pretreatment processes to achieve the best results across downstream unit operations.
  • Careful analysis of the 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.

Our Equipment

Pretreatment Process Options

Mechanical Biomass 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
Dilute acid pretreatment primarily breaks the lignin-hemicellulose matrix, hydrolyzes and removes hemicellulose as xylose into the aqueous phase, and increases the porosity of the cell walls. This, in turn, 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, 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 broken 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
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.
Ionic Liquid
Certain ionic liquids are considered efficient and “green” biomass solvents. They can dissolve large amounts of biomass components in extremely 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
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.
Solid/Liquid Separations
To avoid material loss, depending on the biomass and the type of pretreatment, solids are separated from the liquids before they go to saccharification. Inhibitors may stay in the liquid portion, which may or may not be added back to the downstream conversion process based on the sugar concentration in the aqueous phase.

Related Papers, Articles, and Presentations

Reducing Nutrient Supply in Mixed Feedstock Fermentation

Mixed feedstocks can help reduce the risk associated with feedstock availability for bio-based production of fuels and chemicals. This study was performed to evaluate cellulosic hydrolysates for fermentation to biofuels and also probe the possibility of reducing nutrient concentration in the broth media.

The study demonstrated that mixed feedstocks can release 80 -100% of the sugar that is obtained from corn stover alone. A hundred percent of the released sugars from mixed feedstocks can be converted to ethanol. The study also showed that alkali pretreated mixed feedstock has higher ethanol yield but lower glucose yield compared to IL pretreated mixed feedstock due to inhibition of microbial growth by residual EmimAcetate. The same ethanol yield can be achieved with lower nutrient supplied but with longer fermentation time.

Scale-Up and Process Integration of Municipal Solid Waste Conversion Process

This paper presents two case studies on the scale-up and process integration of municipal solid waste conversion technology. In a partnership with Idaho National Labs, we successfully demonstrated 200-fold scale up of MSW blends IL acidolysis. We also developed an integrated process for ionic liquid based deconstruction technologies for MSW blends conversion. The scale up attempt will leverage the opportunity towards a cost-effective MSW blends conversion technology.

Under a DOE Work-For-Others agreement with FATER, ABPDU has been developing and validating an integrated waste-to-energy process. Key outcomes indicate that post-consumer absorbent hygiene products (AHPs) can be readily and economically converted — without using harsh or expensive pretreatment routes — to sugars and fuel intermediates.

Evaluation of Storage Effect on the Biomass Conversion to Sugars

Dry matter loss (DML) occurs in high-moisture storage conditions; it remains unclear how storage conditions and degradation impact sugar release and fermentation inhibitor production during conversion. In collaboration with Idaho National Labs, two feedstocks, switchgrass and corn stover, were compared using compositional analysis, alkaline pretreatment, and enzymatic saccharification. Under the tested conditions, switchgrass with 10% and 20% DML and corn stover with 30% DML achieved higher sugar yields compared to samples before storage.

Predictive Modeling and Rheological Estimation of Mixed Biomass Feedstocks

In a collaborative effort with INL, SNL, and JBEI, predictive modeling was used to evaluate and optimize traditional pretreatment methods for biomass mixture compositions to maximize sugar yield and minimize furfural production. The collaboration encompassed compositional analysis of feedstocks, solids loading during pretreatment for mixed feedstock, enzymatic hydrolysis on unwashed solids, and sugar and furfural analysis. Predictive modeling could effectively identify the pretreatment catalyst and treatment conditions for an “optimal” biomass mixture and the optimal biomass mixture for a particular pretreatment system.

 

Process Scale-up of Municipal Solid Waste and Corn Stover Blends Conversion into Sugars

 

A collaboration between ABPDU, INL, and SNL as to whether blends of municipal solid waste (MSW) and corn stover (CS) could meet cost and quality targets yielded valuable results. The team successfully developed an integrated process for ionic liquid (IL) based deconstruction technologies. They also demonstrated a 200-fold scale up MSW/CS blends IL acidolysis. The scale up attempt and process integration will leverage the opportunity towards a cost-effective sugar/lignin production technology.

 

Determining the Impact of MSW as a Feedstock Blending Agent on Pretreatment Efficacy

Sixteen MSW blends provided by INL were screened using the 10mL tube reactor to identify the most promising blend (CS/MSW 4:1) for scaling up test based on the sugar yields as well as the feedstock cost. The collaboration also successfully demonstrated 600-fold (10mL to 6L) scale up of MSW/CS blends IL acidolysis.

 

FATER ABPDU Waste-to-Bioenergy Process Partnership

 

ABPDU has been developing and validating an integrated waste-to-energy process under a DOE work-for-others (WFO) agreement with FATER, an Italian JV between Procter & Gamble and the Angelini Industrial Group.

Key outcomes indicate that post-consumer absorbent hygiene products (AHP) can be readily and economically converted — without using harsh or expensive pretreatment routes — to fermentable sugar intermediates as well as biofuel and bio-based chemical products.

Blending Municipal Solid Waste with Corn Stover for Sugar Production Using Ionic Liquid Process

Blending Municipal Solid Waste with Corn Stover for Sugar Production Using Ionic Liquid Process

Municipal solid waste (MSW) represents an attractive cellulosic resource for sustainable fuel production. However, its heterogeneity is the major barrier to efficient conversion to biofuels. MSW paper mix was generated and blended with corn stover (CS). It has been shown that both of them can be efficiently pretreated in some ionic liquid (ILs) processes with high yields of fermentable sugars. After pretreatment in 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]), over 80% glucose has been released with enzymatic saccharification. We have also applied an enzyme-free process by adding mineral acid and water directly into the IL/biomass slurry to induce hydrolysis. With the acidolysis process in 1-ethyl-3-methylimidazolium chloride ([C2C1Im]Cl), up to 80% glucose and 90% xylose are released. There is a correlation between the viscosity profile and hydrolysis efficiency; low viscosity of the hydrolysate generally corresponds to high sugar yields. Overall, the results indicate the feasibility of incorporating MSW as a robust blending agent for biorefineries.

 

Predictive Modeling Can De-Risk Bio-based Production

Predictive Modeling Can De-Risk Bio-based Production

Technologies developed for bio-based production are based on single feedstock types. While this approach is applicable for corn stover in the MidWest, for states such as California, with abundant but diverse feedstocks, technologies should be developed to accommodate multiple feedstock input to a single biorefinery. This project established the influence of mixing feedstocks on downstream sugar recovery and thereby fuel production for Imperial County as a case study. To de-risk bio-based production, we relied on statistical approaches and developed a predictive model to identify optimal biomass concentrations and reaction types, temperatures, and times to maximize sugar yield and minimize furfural production.

 

Scale-Up and Evaluation of High Solids Ionic Liquid Pretreatment and Hydrolysis of Switchgrass

Scale-Up and Evaluation of High Solids Ionic Liquid Pretreatment and Hydrolysis of Switchgrass

Ionic liquid pretreatment is receiving significant attention as a potential process that enables fractionation of lignocellulosic biomass and produces high yields of fermentable sugars suitable for the production of renewable fuels. However, successful optimization and scale up of ionic liquid pretreatment involves challenges, such as high solids loading, biomass handling and transfer, washing of pretreated solids and formation of inhibitors, which are not addressed during the development stages at the small scale in a laboratory environment. As a first in the research community, the Joint BioEnergy Institute, in collaboration with the Advanced Biofuels Process Demonstration Unit, a Department of Energy funded facility that supports academic and industrial entities in scaling their novel biofuels enabling technologies, have performed benchmark studies to identify key challenges associated with ionic liquid pretreatment using 1-ethyl-3-methylimidazolium acetate and subsequent enzymatic saccharification beyond bench scale.