Biomass Pretreatment Technologies Research Articles

Titania catalyst for removing COS and HCN from co-generation effluents

This study presents a techno-economic analysis and an environmental assessment, of the whole production chain (biomass production, sugar extraction, biomass pretreatment, sugars fermentation, and products recovery and purification), of a fully autarkic sugarcane-based biorefinery for biojet fuel production. All scenarios considered correspond to 1st/2nd generation integrated biorefineries (i.e. simultaneous use of sugarcane juice stream and lignocellulosic fractions) with a production scale of 208 kton (biojet fuel) yr−1. In this paper, we compared multiple options for the most relevant processing steps of the biorefinery: eight biomass pretreatment technologies (i.e. dilute acid, dilute acid + alkaline treatment, steam explosion, steam explosion + alkaline treatment, organosolv, alkaline wet oxidation, liquid hot water and liquid hot water + alkaline treatment); two biojet fuel production routes from sugars (i.e. ethanol to jet and direct fermentation); one biojet fuel production route from biomass (i.e. fast pyrolysis); two biojet fuel production routes from lignin obtained after biomass pretreatment (i.e. fast pyrolysis and gasification Fischer- Tropsch); and one alternative use for lignin (i.e. co-generation). From the combination of these key features, 81 scenarios are selected and compared. Furthermore, three potential technological improvements were analysed for selected scenarios: i) recovery of acetic acid and furfural (for cases with bagasse pretreatment); ii) production of succinic acid from a fraction of concentrated juice; iii) increase of operation time (from 200 to 320 days yr−1) by using sweet sorghum as cumulative feedstock. The different scenarios are compared first based on the minimum jet fuel selling price (MJSP) and then based on their environmental performance (i.e. greenhouse gas (GHG) emissions and non-renewable energy use (NREU)). Among the scenarios considering biomass pretreatment, the lower MJSP are obtained when 1G/2G sugars are upgraded via ethanol fermentation (ETJ) (i.e. SO2 steam explosion: 3409 US $.ton−1, and wet oxidation: 3230 US $.ton−1). Additional technological improvements may help to further reduce the MJSP either marginally (2%, by using 1G sugars for succinic acid production) or significantly (30%, by increasing the operation time). Thus, the lowest MJSP here calculated is 1725 US $.ton−1 (with 1G sugars to biojet fuel via ethanol, and bagasse to biojet fuel via fast pyrolysis). Finally, for all scenarios considered, the GHG emissions and NREU were found to be lower than 42.5 kg CO2eq.GJ−1 and 700 MJ GJ −1 respectively (except for scenarios with fast pyrolysis of bagasse where those figures were further reduced by 50% and 80% respectively). Although, the MJSP calculated for all scenarios are higher than those of the fossil jet fuel reference, the significant potential for environmental impacts reduction (in terms of GHG emissions and primary energy use) are encouraging for further research in costs reduction and technology development.

Coordinated development of leading biomass pretreatment technologies

For the first time, a single source of cellulosic biomass was pretreated by leading technologies using identical analytical methods to provide comparative performance data. In particular, ammonia explosion, aqueous ammonia recycle, controlled pH, dilute acid, flowthrough, and lime approaches were applied to prepare corn stover for subsequent biological conversion to sugars through a Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) among Auburn University, Dartmouth College, Michigan State University, the National Renewable Energy Laboratory, Purdue University, and Texas A&M University. An Agricultural and Industrial Advisory Board provided guidance to the project. Pretreatment conditions were selected based on the extensive experience of the team with each of the technologies, and the resulting fluid and solid streams were characterized using standard methods. The data were used to close material balances, and energy balances were estimated for all processes. The digestibilities of the solids by a controlled supply of cellulase enzyme and the fermentability of the liquids were also assessed and used to guide selection of optimum pretreatment conditions. Economic assessments were applied based on the performance data to estimate each pretreatment cost on a consistent basis. Through this approach, comparative data were developed on sugar recovery from hemicellulose and cellulose by the combined pretreatment and enzymatic hydrolysis operations when applied to corn stover. This paper introduces the project and summarizes the shared methods for papers reporting results of this research in this special edition of Bioresource Technology.

Partial flow of compressed-hot water through corn stover to enhance hemicellulose sugar recovery and enzymatic digestibility of cellulose

Flowthrough pretreatment with compressed-hot water can significantly increase the removal of xylan and lignin and enhance xylose sugar yields and cellulose digestibility, especially at high flow rates. However, continuous flowthrough operations that realize these benefits suffer from a large amount of water consumption that leads to high energy requirements for pretreatment and downstream processing. Because high flow rates are particularly effective early in hemicellulose hydrolysis and less effective later, flow with compressed-hot water was applied at selected intervals, and performance was compared with that of batch and flowthrough operations for corn stover pretreated with compressed-hot water at 200 °C. Partial flow reduced water consumption by 60% compared with continuous flowthrough operation but still achieved higher xylose sugar yields (84–89%) compared to batch pretreatment (46.6%). In addition, corn stover cellulose pretreated by partial flow had higher enzymatic digestibility (88–90%) than batch operations (∼85%) at otherwise identical conditions, apparently due to much higher lignin removal for the former (40–45% vs 10–12%). Partial flow also reduced degradation, with recovery of xylose and glucose in the solids and hydrolyzate increased to 90–92% vs only about 76% for batch operation. The partial flow approach could be further improved by optimizing the operating strategy and reaction conditions, suggesting that this novel pretreatment could lead to advanced biomass pretreatment technology.

3611 中圧水蒸気を用いた湿潤バイオマスの革新的前処理技術(S55 再生可能エネルギー)

High efficiency drying is one of the challenges to utilize wet biomass as solid fuel. In addition, usually wet biomass has stinky smell and includes hazardous bacteria, so to collect and convey wet biomass is difficult. We propose a novel pretreatment technology for wet biomass. It is the hydrothermal reforming employing saturated steam at 473K with mixing rice husk. This pretreatment technology has two features; one is increasing effect of apparent drying rate of solid products, another is reforming effect of stinky and distinct odor of sewage sludge. As results of experiments used sewage sludge as model wet biomass, the apparent drying rate of the solid product became four times as large as that of the reactant. And, concerning the stinky smell, the concentrations of H_2S and NH_3 originated from the solid product decreased compared with the sewage sludge by this reforming. This hydrothermal reforming needs little energy compared with conventional indirect heating drying. So, this hydrothermal treatment is appropriate as pretreatment for wet biomass fuelization.

Predicted effects of mineral neutralization and bisulfate formation on hydrogen ion concentration for dilute sulfuric acid pretreatment.

Dilute acid and water-only hemicellulose hydrolysis are being examined as part of a multiinstitutional cooperative effort to evaluate the performance of leading cellulosic biomass pretreatment technologies on a common basis. Cellulosic biomass, such as agricultural residues and forest wastes, can have a significant mineral content. It has been shown that these minerals neutralize some of the acid during dilute acid pretreatment, reducing its effectiveness, and the higher solids loadings desired to minimize costs will require increased acid use to compensate. However, for sulfuric acid in particular, an equilibrium shift to formation of bisulfate during neutralization can further reduce hydrogen ion concentrations and compound the effect of neutralization. Because the equilibrium shift has a more pronounced effect at lower acid concentrations, additional acid is needed to compensate. Coupled with the effect of temperature on acid dissociation, these effects increase acid requirements to achieve a particular reaction rate unless minerals are removed prior to hydrolysis.