• Energy Research

AbstractMexico is one of the largest agricultural producers in Latin America and generates a large amount of agricultural residue. The aim of this study was to establish the usefulness of four of the main Mexican crops (corn, wheat, sugarcane, and Agave) as feedstock for lignocellulosic bioethanol production. The lignocellulosic residue ratio (RR), defined as weight of residue (in tons) per ton of product, was measured by sampling crop fields in 11 geographic regions of Mexico. The chemical composition, assessed by Fourier‐transform infrared spectroscopy (FTIR) and carbon‐13 nuclear magnetic resonance (13C NMR), and structural composition (extractives, cellulose, hemicellulose, and lignin contents), heating value, and metal content of these lignocellulosic residues were measured. Biorefinery locations, and their theoretical bioethanol production, were suggested using the gravity center method and techno‐economic criteria. The highest RR (1.1 ton of straw per ton of grain) was obtained for wheat straw followed by corn (0.8 ton of stover per ton of grain), sugar cane (0.15 ton of bagasse per ton of cane), and Agave (0.2 ton of bagasse per ton of stem). The composition of these biomasses varied significantly depending on the parental material in extractive compounds, lignocellulosic matter, ashes, hemicellulose, lignin, O‐alkyl C, aromatic C, and carboxyl C. The cellulose crystallinity index and the heating value exhibited small variations among biomasses. Copper, Zn, Cd, and Ni content in the biomasses generally exceeded the European Norm (EN‐Plus FprEN 1496 1‐2 B) for solid biofuels. In total, these agricultural biomasses could be used as feedstock for 34 biorefineries in Mexico with a total bioethanol production potential of approximately 1246 million L year–1. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd

Abstract This paper shows how novel high-performance thermophilic consortia employed in the dark fermentation stage of a biorefinery can lead to a competitive commercial-scale hydrogen production using lignocellulosic biomass as feedstock. The biorefinery design alternatives under study also include either diluted acid or hydrothermal pretreatment, and the option of either selling the biogas produced in the wastewater treatment stage or using it for electricity cogeneration. A bi-dimensional (i.e., environmental-economic) sustainability analysis was carried out comparing these four design alternatives against two conventional schemes (coal gasification and natural gas reforming). Results showed that, under a regulatory framework that considers environmental and economic issues on the same basis, the low total production costs of conventional schemes are not enough to compensate, in monetary terms, their severe environmental impacts (mainly water usage and pollution) when compared with the biorefining options. Moreover, most of the proposed biorefinery schemes ranked higher than conventional options. In particular, the design with acid pretreatment and biogas sale was the most sustainable option with a positive global sustainability indicator (0.007 USD/MJout).

Abstract Bioethanol as fuel oxygenator is currently being introduced in Mexico with an estimated yearly demand of 3 billion liters expected to be produced mainly from sugarcane. This paper studies how to employ some of the expertise acquired by Brazil during its transition from typical mills into advanced biorefineries to retrofit the Mexican sucroalcohol industry. A typical Mexican sugarcane factory design is retrofitted to three biorefinery designs commonly found in Brazil, which are an autonomous distillery, a biorefinery with 50:50 feedstock ratio for ethanol and sugar production and a molasses distillery. The results of a techno-economic analysis considering these four designs under Mexican conditions are presented, followed by an economic comparison of the autonomous distillery design operating under Mexican and Brazilian conditions. Sustainability analysis is then carried out to identify the advantages and drawbacks of each design. The analysis compares an environment-driven scenario promoting bioethanol production and use for phasing out fossil fuels, against a commercially focused framework considering only environmental and economic issues affecting stakeholders’ profit. Results show in monetary terms the impact of each indicator of a retrofitting path from currently profitable biorefineries coproducing sugar and alcohol to sustainable distilleries using molasses and juice as feedstock to produce bioethanol.

This work presents a dynamic discrete model that describes the mass flow and residence time behavior in a pretreatment continuous tubular reactor using lignocellulosic biomass as feedstock. The model consists of a set of linear difference equations that accurately describe the output flow as a function of the operation conditions. Model parameters account for mechanical and rheological properties of different lignocellulosic biomass, as well as complex backflow phenomena commonly encountered in these reactors. The proposed dynamic model was experimentally validated for wheat straw and corn stover. Additionally, a control strategy was proposed for the residence time and was correctly validated through simulations.

Abstract Wheat straw is gaining importance as a feedstock for the production of biofuels and high value-added bioproducts. Several pretreatments recover the fermentable fraction involving the use of water or aqueous solutions. Therefore, hydration properties of wheat straw fibers play an important role in improving pretreatment performance. In this study, the water retention capacity (WRC) and swelling of wheat straw fibers were studied using water, propylene glycol (PPG) and an effluent from a H 2 -producing reactor as the hydration media with three particle sizes (3.35, 2.00 and 0.212 mm). The effects of swelling were analyzed by optical and confocal laser scanning microscopy (CLSM). The highest WRC was reached with the effluent medium (9.84 ± 0.87 g g −1 in 4 h), followed by PPG (8.52 ± 0.18 g g −1 in 1 h) and water (8.74 ± 0.76 g g −1 in 10 h). The effluent hydration treatment had a synergic effect between the enzymes present and the water. The particle size had a significant effect on the WRC ( P

The production of tequila in Mexico generates a large amount of agave bagasse per year. However, this biomass can be considered as a potential source for biofuel production. In this study, it is described how the hydrothermal pretreatment was scaled in a bench scale, considering the severity index as a strategy. The best condition was at 180 °C in isothermal regime for 20 min with 65.87% of cellulose content and high concentration of xylooligosaccharides (15.31 g/L). This condition was scaled up (using severity factor: [logR0] = 4.11), in order to obtain a rich pretreated solid in cellulose to perform the enzymatic hydrolysis, obtaining saccharification yields of 98.5 and 99.5% at high-solids loading (10 and 15%, respectively). The pre-saccharification and fermentation strategy was used in the bioethanol production at 10 and 15% of total pretreated solids, obtaining 38.39 and 55.02 g/L of ethanol concentration, corresponding to 90.84% and 87.56% of ethanol yield, respectively.

Abstract An advanced biorefinery design is proposed for co-producing n-butanol (butan-1-ol, CAS 71-63-3), acetone (propan-2-one, CAS 67-64-1) and ethanol (CAS 64-17-5) (ABE), as well as hydrogen ( H 2 , CAS 4368-28-9) and biogas from lignocellulosic feedstock using mixed cultures. The biorefinery does not pretreat the feedstock and employs the hemicellulose (CAS 9034-32-6) and cellulose (CAS 9004-34-6) feedstock fractions for producing hydrogen and ABE in separate low-cost, low process-complexity fermentation stages. These reaction stages were designed based on the authors' own experimental data under Consolidated Bioprocessing (CBP) principles. The biorefinery design also includes a novel separation stage, electricity-steam cogeneration and heat integration. The technical feasibility of the proposed biorefinery is demonstrated through a parametric analysis of the total production costs (TPC) and energy efficiency with respect to feedstock price and biorefinery capacity. The feedstock price is proportional to its polysaccharides content as a way of assessing the impact of limited feedstock availability on TPC. The proposed CBP hydrogen and ABE fermentation technologies reduced fixed capital investment 7.7fold and 8.6fold for mid-size (1000 t d − 1 ) and large (2000 t d − 1 ) capacities. The end-use energy ratio achieved was between 2.14 and 2.24 for this interval capacity. Design and process conditions were identified to achieve similar TPCs (0.75 $ L − 1 for 1000 t d − 1 and 0.63 $ L − 1 for 2000 t d − 1 , respectively) of sound conceptual designs previously published employing conventional technology. The results obtained in this study were compared with inflation-updated TPCs of conventional-technology biorefineries from works published over the past fifteen years, highlighting the advantages of the proposed design.

AbstractA method is proposed to analyze the environmental and economic sustainability of biorefineries producing lignocellulosic ethanol. The bidimensional method builds on the conceptual design of the production facility (mathematical models of mass and energy balances of each process stage, equipment sizing, and capital costing models) thus enabling the analysis of prospective technologies. The conceptual design articulates the relations among process stages as impact generators (IIG), stakeholders (and their concerns) as impact receivers (EIR), and indicators to measure the environmental and economic impacts of the process facility. Indicators are formulated as functions of process variables and parameters. Overall impacts for each domain are calculated by weighting the indicators using appropriate dimensional functions and scaling factors. Using the proposed method, the conceptual design of a standard biochemical biorefinery provides the basis for building a sustainability framework comprising 15 indicators. While some of the obtained indicators are ubiquitous in the literature, other less common yet important are identified. A case study illustrates the use of the sustainability framework. A single‐product biorefinery is compared against a multi‐product scheme, showing that single‐product schemes may prove, under certain conditions, more sustainable than their multi‐product counterparts. The sustainability framework provides the rationale to clearly identify the causality from IIG to metric values. This information may be used to support the decisions regarding possible improvements of IIG or modifications of weighting parameters in the dimensional functions in order improve the sustainability of the processes under consideration. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd