Towards Comparable Carbon Credits: Harmonization of LCA Models of Cellulosic Biofuels

Decarbonization programs are being proposed worldwide to reduce greenhouse gas (GHG) emissions from transportation fuels, using Life Cycle Assessment (LCA) models or tools. Although such models are broadly accepted, varying results are often observed. This study describes similarities and differences of key decarbonization programs and their GHG calculators and compares established LCA models for assessing 2G ethanol from lignocellulosic feedstock. The selected LCA models were GHGenius, GREET, JRC’s model, and VSB, which originated calculators for British Columbia’s Low Carbon Fuel Standard, California’s Low Carbon Fuel Standard, Renewable Energy Directive, and RenovaBio, respectively. We performed a harmonization of the selected models by inserting data of one model into other ones to illustrate the possibility of obtaining similar results after a few harmonization steps and to determine which parameters have higher contribution to closing the gap between default results. Differences among 2G ethanol from wheat straw were limited to 0.1 gCO2eq. MJ−1, and discrepancies in emissions decreased by 95% and 78% for corn stover and forest residues, respectively. Better understanding of structure, calculation procedures, parameters, and methodological assumptions among the LCA models is a first step towards an improved harmonization that will allow a globally accepted and exchangeable carbon credit system to be created.

Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Background Future expansion of corn-derived ethanol raises concerns of sustainability and competition with the food industry. Therefore, cellulosic biofuels derived from agricultural waste and dedicated energy crops are necessary. To date, slow and incomplete saccharification as well as high enzyme costs have hindered the economic viability of cellulosic biofuels, and while approaches like simultaneous saccharification and fermentation (SSF) and the use of thermotolerant microorganisms can enhance production, further improvements are needed. Cellulosic emulsions have been shown to enhance saccharification by increasing enzyme contact with cellulose fibers. In this study, we use these emulsions to develop an emulsified SSF (eSSF) process for rapid and efficient cellulosic biofuel production and make a direct three-way comparison of ethanol production between S. cerevisiae, O. polymorpha, and K. marxianus in glucose and cellulosic media at different temperatures. Results In this work, we show that cellulosic emulsions hydrolyze rapidly at temperatures tolerable to yeast, reaching up to 40-fold higher conversion in the first hour compared to microcrystalline cellulose (MCC). To evaluate suitable conditions for the eSSF process, we explored the upper temperature limits for the thermotolerant yeasts Kluyveromyces marxianus and Ogataea polymorpha, as well as Saccharomyces cerevisiae, and observed robust fermentation at up to 46, 50, and 42 °C for each yeast, respectively. We show that the eSSF process reaches high ethanol titers in short processing times, and produces close to theoretical yields at temperatures as low as 30 °C. Finally, we demonstrate the transferability of the eSSF technology to other products by producing the advanced biofuel isobutanol in a light-controlled eSSF using optogenetic regulators, resulting in up to fourfold higher titers relative to MCC SSF. Conclusions The eSSF process addresses the main challenges of cellulosic biofuel production by increasing saccharification rate at temperatures tolerable to yeast. The rapid hydrolysis of these emulsions at low temperatures permits fermentation using non-thermotolerant yeasts, short processing times, low enzyme loads, and makes it possible to extend the process to chemicals other than ethanol, such as isobutanol. This transferability establishes the eSSF process as a platform for the sustainable production of biofuels and chemicals as a whole.

SBA-15 Modified with Tethered Ionic Liquids Applied in the Esterification of Valeric Acid with Pentanol—Towards Cellulosic Biofuels

Two catalysts are prepared by tethering ionic liquid cation components (1-(propyl-3-sulfonate)-3-(3-trimethoxysilylpropyl) imidazolium) with either chloride or sulphate anions, to the surface of a mesoporous SiO2 material through a condensation reaction. These are characterized using elemental analysis, TGA-MS, FTIR (and D-FTIR), TEM, physisorption and NH3 adsorption (TPD and FTIR), and applied in the valeric acid + pentanol esterification reaction to form the sustainable biodiesel Pentyl Valerate. The material containing the sulfate counter-ion was significantly more active than the chloride analogue.

Advanced Hardwood Biofuels Northwest: Commercialization Challenges for the Renewable Aviation Fuel Industry

A bioenergy summit was organized by Advanced Hardwood Biofuels Northwest (AHB) to debate the barriers to the commercialization of a hybrid poplar biofuels industry for the alternative jet fuels market from the perspective of five years of AHB research and development and two recent surveys of the North American cellulosic biofuels industry. The summit showed that: (1) Growing and converting poplar feedstock to aviation fuels is technically sound, (2) an adequate land base encompassing 6.03 and 12.86 million respective hectares of croplands and rangelands is potentially available for poplar feedstock production, (3) biofuel production is accompanied by a global warming potential that meets the threshold 60% reduction mandated for advanced renewable fuels but (4) the main obstruction to achieving a workable poplar aviation fuels market is making the price competitive with conventional jet fuels. Returns on investment into biomass farms and biorefineries are therefore insufficient to attract private-sector capital the fact notwithstanding that the demand for a reliable and sustainable supply of environmentally well-graded biofuels for civilian and military aviation is clear. Eleven key findings and recommendations are presented as a guide to a strategic plan for a renewed pathway to poplar alternative jet fuels production based upon co-products, refinery co-location with existing industries, monetization of ecosystem services, public-private financing, and researching more efficient and lower-costs conversion methods such as consolidated bioprocessing.

Lignin-Based Polyurethanes: Opportunities for Bio-Based Foams, Elastomers, Coatings and Adhesives

Polyurethane chemistry can yield diverse sets of polymeric materials exhibiting a wide range of properties for various applications and market segments. Utilizing lignin as a polyol presents an opportunity to incorporate a currently underutilized renewable aromatic polymer into these products. In this work, we will review the current state of technology for utilizing lignin as a polyol replacement in different polyurethane products. This will include a discussion of lignin structure, diversity, and modification during chemical pulping and cellulosic biofuels processes, approaches for lignin extraction, recovery, fractionation, and modification/functionalization. We will discuss the potential of incorporation of lignins into polyurethane products that include rigid and flexible foams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating lignin in polyurethane formulations, potential solutions and approaches that have been taken to resolve those issues.

Integration of renewable deep eutectic solvents with engineered biomass to achieve a closed-loop biorefinery

Despite the enormous potential shown by recent biorefineries, the current bioeconomy still encounters multifaceted challenges. To develop a sustainable biorefinery in the future, multidisciplinary research will be essential to tackle technical difficulties. Herein, we leveraged a known plant genetic engineering approach that results in aldehyde-rich lignin via down-regulation of cinnamyl alcohol dehydrogenase (CAD) and disruption of monolignol biosynthesis. We also report on renewable deep eutectic solvents (DESs) synthesized from phenolic aldehydes that can be obtained fromCADmutant biomass. The transgenicArabidopsis thaliana CADmutant was pretreated with the DESs and showed a twofold increase in the yield of fermentable sugars compared with wild type (WT) upon enzymatic saccharification. Integrated use of low-recalcitrance engineered biomass, characterized by its aldehyde-type lignin subunits, in combination with a DES-based pretreatment, was found to be an effective approach for producing a high yield of sugars typically used for cellulosic biofuels and biobased chemicals. This study demonstrates that integration of renewable DES with plant genetic engineering is a promising strategy in developing a closed-loop process.