Optimal processing pathway selection for microalgae-based biorefinery under uncertainty

We propose a systematic framework for the selection of optimal processing pathways for a microalgae-based biorefinery under techno-economic uncertainty. The proposed framework promotes robust decision making by taking into account the uncertainties that arise due to inconsistencies among and shortage in the available technical information. A stochastic mixed integer nonlinear programming (sMINLP) problem is formulated for determining the optimal biorefinery configurations based on a superstructure model where parameter uncertainties are modeled and included as sampled scenarios. The solution to the sMINLP problem determines the processing technologies, material flows, and product portfolio that are optimal with respect to all the sampled scenarios. The developed framework is implemented and tested on a specific case study. The optimal processing pathways selected with and without the accounting of uncertainty are compared with respect to different objectives.     

SO2-Ethanol-Water (SEW) Pulping: I. Lignin Determination in Pulps and Liquors

Abstract

Quantitative determination of lignin in SO₂-ethanol-water (SEW) pulps and spent liquors is described. The methods developed for conventional sulfite pulping are successfully applied to the SEW process. Linear correlations between Klason/total lignin content and kappa number are found over a wide pulp yield range for spruce, beech, and wheat straw. Lignin content of the spruce spent SEW liquors is determined using either hydrogen peroxide to remove SO₂ and dilution by 3% sulfuric acid or simply by dilution with 0.1M sodium hydroxide. The recommended wavelength is 280 nm. The experimentally found values for the extinction coefficient of dissolved lignin in 3% sulfuric acid and in 0.1M NaOH are 19 and 23 L/(g·cm), respectively. The interference of furanic compounds is eliminated by reduction with sodium borohydride.     

Integrated Forest Biorefinery: Value-added Utilization of Dissolved Organics in the Prehydrolysis Liquor of Prehydrolysis Kraft (PHK) Dissolving Pulp Production Process

The concept of integrated forest biorefineries(IFBRs) has gained significant interest.The prehydrolysis kraft(PHK) dissolving pulp production process is a suitable example of IFBR concept for the production of dissolving pulp and utilization of dissolved hemicelluloses,acetic acid,and lignin in the prehydrolysis liquor(PHL).This review paper highlights recent progress related to the recovery and utilization of dissolved organics(e.g.,hemicelluloses,acetic acid,and lignin) in the PHL of the PHK dissolving pulp production process.Integrated multi-step recovery and separation processes have been developed for this purpose to accommodate the complex nature of the PHL.Potential products,including xylan-based compounds,acetic acid,and lignin,are also discussed in detail.     

Enzymatic Pretreatment with Laccases from Lentinus sajor-caju Induces Structural Modification in Lignin and Enhances the Digestibility of Tropical Forage Grass (Panicum maximum) Grown under Future Climate Conditions

Since laccase acts specifically in lignin, the major contributor to biomass recalcitrance, this biocatalyst represents an important alternative to the pretreatment of lignocellulosic biomass. Therefore, this study investigates the laccase pretreatment and climate change effects on the hydrolytic performance of Panicum maximum. Through a Trop-T-FACE system, P. maximum grew under current (Control (C)) and future climate conditions: elevated temperature (2 °C more than the ambient canopy temperature) combined with elevated atmospheric CO₂ concentration(600 μmol mol⁻¹), name as eT+eC. Pretreatment using a laccase-rich crude extract from Lentinus sajor caju was optimized through statistical strategies, resulting in an increase in the sugar yield of P. maximum biomass (up to 57%) comparing to non-treated biomass and enabling hydrolysis at higher solid loading, achieving up to 26 g L⁻¹. These increments are related to lignin removal (up to 46%) and lignin hydrophilization catalyzed by laccase. Results from SEM, CLSM, FTIR, and GC-MS supported the laccase-catalyzed lignin removal. Moreover, laccase mitigates climate effects, and no significant differences in hydrolytic potential were found between C and eT+eC groups. This study shows that crude laccase pretreatment is a potential and sustainable method for biorefinery solutions and helped establish P. maximum as a promising energy crop.     

稀水解液循环回用对玉米秸秆水解液中主要化学组分得率的影响

为实现对水洗玉米秸秆自水解预处理固相物产生的稀水解液（简称稀水解液）中主要化学组分的高效利用,探讨了自水解预处理工艺条件以及将稀水解液回用于玉米秸秆自水解预处理对水解液中主要化学组分得率的影响。结果表明,在液固比10∶1（V/w）、170 ℃保温40 min条件下,水解液中糖类化合物、甲酸、呋喃化合物及酚类化合物等主要化学组分得率均达到最大值。在此工艺参数基础上添加2%乙酸作为自水解处理过程中的催化剂,可进一步提高糖类、弱酸类及呋喃化合物的得率。将稀水解液循环回用于玉米秸秆的自水解预处理过程7次后,水解液中主要化学组分则分别进一步显著（P < 0.05）提高21.0%（糖）、71.0%（甲酸）、44.6%（乙酸）、80.7%（酚类化合物）、102.1%（糠醛）及98.5%（5-羟甲基糠醛）,有效实现了水解液中主要化学组分的富集和增浓。上述研究为玉米秸秆自水解预处理工艺的调整及稀水解液的利用提供理论依据和数据支持。     

Crop residues: applications of lignocellulosic biomass in the context of a biorefinery

Interest in lignocellulosic biomass conversion technologies has increased recently because of their potential to reduce the dependency on non-renewable feedstocks. Residues from a variety of crops are the major source of lignocellulose, which is being produced in increasingly large quantities worldwide. The commercial exploitation of crop residues as feedstocks for biorefineries which could be used to produce a variety of goods such as biofuels, biochemicals, bioplastics, and enzymes is an attractive approach not only for adding value to residues but also for providing renewable products required by the expanding bioeconomy market. Moreover, the implementation of biorefineries in different regions has the potential to add value to the specific crop residues produced in the region. In this review, several aspects of crop residue application in biorefineries are discussed, including the role of crop residues in the bioeconomy and circular economy concepts, the main technical aspects of crop residue conversion in biorefineries, the main crop residues generated in different regions of the world and their availability, the potential value-added bioproducts that can be extracted or produced from each crop residue, and the major advantages and challenges associated with crop residue utilization in biorefineries. Despite their potential, most biomass refining technologies are not sufficiently advanced or financially viable. Several technical obstacles, especially with regard to crop residue collection, handling, and pre-treatment, prevent the implementation of biorefineries on a commercial scale. Further research is needed to resolve these scale-up-related challenges. Increased governmental incentives and bioeconomic strategies are expected to boost the biorefinery market and the cost competitiveness of biorefinery products.     

The Effect of Lignification Process on the Bioconversion Efficiency in Moso Bamboo

Recalcitrance of lignocellulosic biomass is closely related to the presence of lignin in secondary cell walls, which has a negative effect on enzyme digestibility, biomass-to-biofuels conversion, and chemical pulping. The lignification process and structural heterogeneity of the cell wall for various parts of moso bamboo were investigated. There were slight differences among three different column parts of moso bamboo in terms of chemical compositions, including cellulose, hemicelluloses, and lignin. However, the detailed analysis of the fractionated lignin indicated that the acid-soluble lignin was first biosynthesized, and the largest molecular weight value was detected from the bottom part of the moso bamboo, as well as the highest syringyl-to-guaiacyl ratio. Although the main -O-4 aryl ethers and resinol structures were clearly present in all lignin samples examined by NMR analysis, the relatively small lignin biomacromolecule in the top part of the moso bamboo lead to poor thermal stability. For the bioconversion process, no significant difference was found among all the moso bamboo samples, and the relatively higher hydrolysis efficiency was largely dependent on the low crystallinity of cellulose rather than the degree of lignin biosynthesis.     

Fermentative hydrogen production from cheese whey with in-line,concentration gradient-driven butyric acid extraction

Hydrogen (H₂) generation from cheese whey with simultaneous production and extraction of volatile fatty acids (VFAs) was studied in UASB reactors at two temperatures (20 and 35 °C) and pH values (5.0 and 4.5). The extraction module, installed through a recirculation loop, was a silicone tube coil submerged in water, which allows concentration-driven extraction of undissociated VFAs. Operating conditions were selected as a compromise for the recovery of both H₂ and VFAs. Batch experiments showed a higher yield (0.9 mol H₂ mol⁻¹ glucose_eq.) at 35 °C and pH 5.0, regardless of the presence of the extraction module, whereas lower yields were obtained at pH 4.5 and 20 °C (0.5 and 0.3 mol H₂ mol⁻¹ glucose_eq., respectively). VFAs crossed the silicone membrane, with a strong preference for butyric over propionic and acetic acid due to its higher hydrophobicity. Sugars, lactic acid and nutrients were retained, resulting in an extracted solution of up to 2.5 g L⁻¹ butyric acid with more than 90% purity. Continuous experiment confirmed those results, with production rates up to 2.0 L H₂ L⁻¹ d⁻¹ and butyric acid extraction both in-line (from the UASB recirculation) and off-line (from the UASB effluent). In-line VFA extraction can reduce the operating costs of fermentation, facilitating downstream processing for the recovery of marketable VFAs without affecting the H₂ production.     

Influence of synthesis conditions on the production of molecularly imprinted polymers for the selective recovery of isovaleric acid from anaerobic effluents

Two molecularly imprinted polymers (MIPs) – poly(methacrylic acid‐co‐TRIM) (TRIM, trimethylolpropanetrimethacrylate) and poly(acylamide‐co‐TRIM) – were synthesized in different solvents for the selective recovery of isovaleric acid (template) generated during the anaerobic digestion process. The chemical and structural characterizations of the synthetic adsorbent were carried out by Fourier transform infrared spectroscopy, TGA and porosimetry through N₂ adsorption–desorption isotherms. The selective and adsorptive performances of the imprinted polymers were evaluated by kinetic, isothermal, thermodynamic and selectivity studies and by adsorbent reuse experiments. The poly(methacrylic acid‐co‐TRIM) synthesized with dimethyl sulfoxide:chloroform presented higher selectivity and adsorption capacity for isovaleric acid in the presence of six volatile fatty acids. The kinetic results were well adjusted to the pseudo‐nth order and intraparticle diffusion models, leading to k values of 10^?4 and 6 × 10^?5 for the best synthesis of MIPs and not‐imprinted polymers, respectively. Moreover, the Sips model best described the adsorption isotherm and generated a maximum adsorption capacity of ca 209 mg g^?1 (at 25 °C). Cycles of MIP use–desorption–reuse indicated that the selective adsorbent performed better than commercial adsorbents, losing less than 3% of adsorption capacity after three cycles. © 2018 Society of Chemical Industry