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This paper introduces a methodological framework for assessing the sustainability of solid biofuels in Mexico. The designed framework comprises 13 normalized indicators and two diagnostic studies, covering the economic, social, environmental, and institutional sustainability dimensions, and their intersections. Indicators are normalized using the concept of load capacity of a system, similarly to the planetary boundaries. Thus, the graphical representation of results facilitates their multidimensional analysis. The framework was applied to three case studies: traditional fuelwood in rural households, charcoal for restaurant grilling, and electricity cogeneration from sugarcane bagasse. This was part of an iterative process of testing and refining the framework and simultaneously demonstrating its application in the Mexican bioenergy context. This led to the conclusion that the resulting framework (a) provides a useful, quantitative, and comprehensive overview of both broad and specific sustainability aspects of the assessed system; (b) requires a balance of accessible but also scattered or sensitive data, similarly to most existing frameworks; (c) is highly flexible and applicable to both modern and traditional solid biofuels; and (d) is simple to communicate and interpret for a wide audience. Key directions for improvement of the framework are also discussed. Supplementary Information The online version contains supplementary material available at 10.1007/s12155-021-10365-2.

In Mexico, the possibility to exploit orange peels or sugarcane straw to generate heat has not been fully explored, even though they are major agronomic wastes generated in Mexico. Therefore, this paper aims to assess the heat generation’s environmental and economic performance from these feedstocks in a fruit-processing facility located in Veracruz, Mexico. The environmental performance was assessed through the life-cycle assessment methodology, while the economic performance was estimated through the total levelized cost of energy (TLCE) considering two scenarios: (1) a base scenario where orange peels are burnt to produce process steam, and (2) a second scenario where sugarcane straw is co-fired with it. Both scenarios assume to partially displace heavy-fuel–oil (HFO) for steam generation. Results indicate that the impacts of the use of residual biomass-based heat on the potential global warming, ozone layer depletion, marine aquatic ecotoxicity, and cumulative energy demand are 34–63% lower than when using HFO and decrease the TLCE by 18–21%. However, there is also an increase in other environmental impact categories such as human toxicity, photochemical oxidation, or eutrophication. The use of orange from organic farms improves the environmental results in some of these categories. The drying and combustion of the biomass, as well as the waste treatment, are the major contributors to the environmental impacts. On the other hand, capital and fuel costs are the major contributors to TLCE. Overall, the use of orange peels and sugarcane straw to generate heat is attractive from the environmental and economic point of views.

This study reports the extraction of Jatropha curcas leaves using supercritical CO2. Experiments were performed varying the pressure (13 and 20 MPa) and the temperature (50°C and 60°C). The model of Sovova for supercritical fluid extraction was fitted to the experimental kinetic extraction curves. Two cell sizes were used and scale up equations compared. GC analysis showed phytol, carvacrol, and hexahydrofarnesyl acetone as major compounds in all the experiments. A maximum yield of 0.95% dry-weight basis was obtained. It was observed a maximum yield (0.95% dry-weight basis) extract obtained at 20 MPa and 50°C. The results indicated that the mass yield increased with the increase of pressure. The bioassays showed that the extract of J. curcas possessed toxicity against Hyalomma lusitanicum.

Motivated by the environmentally driven energy transition we live in, the valorization of biomass residues from the agro-industry as renewable energy can play an essential role in GHG emissions mitigation. To overcome the debate on the production and use of solid biofuels (SBF), in this study, we apply an integrated multicriteria tool for the assessment of the sustainability use of agro-industrial residues (AIR) as solid biofuels. Mexico has a vast AIR production, but frequently, the AIR are considered waste biomass. Still, when valorized, SBF do not have adverse effects on soil quality, are not responsible for biodiversity loss, and compete against food production as first-generation SBF. Nevertheless, the AIR present other environmental, social, and economic impacts that have not been adequately evaluated; therefore, we identified the need for a sustainability assessment of energy systems based on the use of SBF–AIR as input fuels. After reviewing previous work on sustainability assessment methodologies, multicriteria decision analysis methods, and indicator weighting methods, we considered it appropriate for this problem to apply a tool that integrates the entropic indicator weighting method into the discrete multicriteria decision analysis method called PROMETHEE. In terms of selected sustainability indicators, this tool was used to assess four electric energy supply systems of a Mexican sugar mill as a case study: current bagasse cogeneration, efficient bagasse cogeneration, a power generation system fueled only with fuel oil, and grid electricity only. Finally, after evaluating the mentioned energy systems with four sustainability indicators: GHG emissions, PM emissions, employments per energy unit (JOBS), and the net present value (NPV) of each alternative, we found the net outranking flow of the efficient bagasse system (EBS). which is the most sustainable system because it has the highest outranking flow value from the four considered alternatives, since it has the lower GHG emissions, reducing the current bagasse GHG emissions by 55% and the PM emissions by 58%. The EBS also shows the highest NPV system due to surplus electricity sales, resulting in the most profitable energy system analyzed.

The increasing amount of plastic waste generation has become an important concern for the chemical industry and government agencies due to high disposal and environmental leakage rates. Chemical re...

The growing generation of plastic waste (PW) is placing severe burdens in the terrestrial and marine environments due to its inappropriate management at end of life. Governments are aware of this s...

In this study, leave extracts of Lippia graveolens were obtained using supercritical CO2. The objective was to evaluate the effect of temperature and pressure on the extraction yield and kinetics. Supercritical fluid extractions were performed at three pressures (13, 15 and 35 MPa) and two temperatures (40 and 60 °C). Sovova’s model for supercritical fluid extraction was fitted to describe the kinetic extraction curves and analyze the results. The extracts were analyzed by GC–MS, where Carvacrol was the majority compound in all the experiments. A maximum yield of 2.6% on a dry weight basis was obtained at 35 MPa and 60 °C. The extraction yield increased with temperature and pressure, in all the analyzed samples.

The effects of the concentration of three kinds of constituents of aqueous culture media (mixed electrolytes, glucose, sucrose, and commercial antifoam) on oxygen transfer were studied in a bubble column bioreactor. The volumetric mass transfer coefficient (kLa) and the specific interfacial area (a) were measured at five superficial gas velocities under the homogeneous bubbling regime. The mixed electrolytic salts (0 ≤ ionic strength ≤ 0.4126 M) and, to a lesser extent, the glucose (0 ≤ c ≤ 0.222 M) caused the increase of kLa up to a maximum value, followed by a either a slight decrease, or no significant change. The higher values of kLa corresponded to critical concentrations, indicating a maximum inhibition of bubble coalescence. The kLa was governed by changes in interfacial area up to the critical concentrations, where the dominant contribution shifted to kL; at the studied concentrations, the sucrose had no significant effect on kLa. Finally, low concentrations of commercial antifoam caused an overall decrement in kLa due entirely to the hindering effects of antifoams on kL.

The effects of the concentrations of biomass, mixed salts, total carbohydrates, and proteins on atmospheric CO2 transfer in a bubble column photobioreactor during the photoautotrophic culture of Ch...

Thermal degradation of plastics is a promising technology for addressing the waste management issues of landfill disposal, while obtaining useful products. Primary thermal degradation of polymers usually yields a large quantity of high molecular weight compounds with a limited applicability, making necessary a secondary degradation to improve the product quality. In this study, pyrolysis vapors from waste high density polyethylene (HDPE) were subjected to secondary degradation by varying the temperature and vapor residence time (VRT) in the reaction zone of a new two-stage micropyrolysis reactor (TSMR) attached to a commercial micropyrolysis unit. Temperature and VRT variations showed a strong effect on the product distribution, with low temperature (625 °C) and short VRT (1.4 s) producing a wide range of gases and liquid products and with high temperature (675 °C) and long VRT (5.6 s) producing mostly hydrocarbon gases and mono- and polyaromatics. The results showed a good agreement with previously repor...

Bioethanol is being promoted in Mexico to be used in a blend with gasoline. On the north of the Yucatan peninsula, bioethanol could be produced from sweet sorghum, as it can grow efficiently on this land; it can be harvested 2–3 times in a year and possesses a better agronomical stability than sugarcane with low nitrogen requirements and high productivity. In this work , the potential environmental impacts and energy efficiency of bioethanol production from sweet sorghum were evaluated using life-cycle assessment. Four scenarios were evaluated: scenario PI considered only bioethanol production from the stalk juice; scenarios PII and PIII added cogeneration from the dry-stalk biomass in single and combined cycle, respectively. Scenario PIV considered bioethanol production from both stalk juice and dry-stalk biomass. Scenario PI demanded more fossil energy than what was generated as bioethanol, while scenarios PII and PIII were fossil energy independent. Scenario PIII showed the higher net energy ratio (1.89) and a better environmental performance in all CML-IA baseline impact categories. In terms of global warming potential, the scenario PIII showed a mitigation potential of 16% with respect to the fossil reference. In the categories where the sweet sorghum scenarios represented larger emissions than the fossil reference, it was due mainly to the use of fertilizers and the conventional energy consumption in the various processing steps of the biomass. Scenario PIV showed the highest energy demand and worst environmental performance due to large demands of energy and chemicals in the bagasse pretreatment step.

A national energy strategy in Mexico to 2028, derived from the recent energy reform, projects a considerable shift in the national power generation mix leading to changes on its environmental profile. Therefore, this paper aims to compare the potential environmental impacts of the electricity generation under previous, current and projected energy mixes in Mexico at a national and regional scale considering the Yucatan state as the regional case study. These were estimated with a cradle-to-grave Life Cycle Assessment (LCA) following the CML–IA 2000 V2.05 methodology and including the baseline environmental impact categories. Results indicate that the environmental impacts per generated kWh of electricity have decreased in Mexico from 2007 to 2013 and would keep decreasing at a faster rate until 2028 according to current projections. In Yucatan, the environmental impacts increased from 2007 to 2013 due to an increased diesel consumption, but would decrease by 2028 reaching lower levels than in 2007. From 2007 to 2013 almost all the environmental impacts in Yucatan were lower than the country average due to a higher contribution of natural gas in the power generation mix, while in 2028 they would be similar. Overall, there is a significant difference between the national and regional estimations of the potential environmental impacts due to differences in their power generation mix. Furthermore, the potential introduction of shifts derived from the energy reform in Mexico will have a strong positive influence on the environmental impacts from the electricity generation.

Research on these kinds of plants promotes a beneficial impact on the economy because it addresses the rural and energy crises. In this study, the steam distillation process for obtaining essential oil from Lippia graveolens leaves was evaluated at laboratory and pilot scales. The parameters analyzed were steam flow and bed porosity, and their effects on the extraction yield were determined. The effect of steam flow was found to be an important parameter in steam distillation. The extracts obtained were analyzed by GC-MS. Carvacrol, thymol, and β-cymene constituted the major components of L. graveolens at both scales. The model tested showed a good fit to the experimental data for L. graveolens. The results showed that the greatest yield (4.41 %) was obtained at laboratory scale.

BACKGROUND At commercial level, the biodiesel production process is well established for many types of feedstock. However, economic feasibility depends on regional fluctuating data, making each case unique. A calculation model to analyze the economic feasibility of biodiesel production from Jatropha curcas was developed, along with an analysis of the energetic balance derived from this process. RESULTS Yucatan state has the cultivation surface to replace 10% of its fossil diesel fuel consumption with biodiesel. Two scenarios were studied: the use of biodiesel–fossil diesel blends B5 and B10. The net energy ratio (NER) of biodiesel production is 2.88, indicating that the system provides more energy than it consumes. The economic analysis indicates that biodiesel cost remains constant with production capacities of 10 000 m3 year−1 and higher. Field labor, pesticides, and fertilizers are the major costs at J. curcas plantations, representing 64.3, 16.3 and 11.5% of total biodiesel cost, respectively. The net present value (NPV) was always negative, proving that the biodiesel–jatropha chain is not economically viable. CONCLUSIONS Actual seed productivity (1 495 kg ha−1 year−1) must be increased 2.17 times to attain economic viability. Agricultural practices need to be enhanced in order to lower labor cost and the use of fertilizers. © 2016 Society of Chemical Industry

The use of components in municipal solid waste (MSW) as feedstock for liquid transportation biofuels and chemicals can be a sustainable solution for energy needs while minimizing impacts of landfills on the environment. This study conducts a resource assessment for available MSW in Mexico and concludes that when the organic and polyolefin plastic components are converted to liquid hydrocarbon transportation biofuels through a pyrolysis-based pathway, up to 7% of Mexico’s transportation-fuel consumption needs could be met. A preliminary carbon footprint analysis (CFA) using stage-specific emission factors from the literature shows that liquid transportation biofuels from the organic portion of MSW (paper, packaging, wood, yard trimmings) sequesters 9.5 g CO2 eq per MJ biofuel, with significant pathway credits due to avoiding landfill CH4 emissions. The greenhouse gas (GHG) emissions from the conversion of the polyolefin plastic in the MSW are positive (88 g CO2 eq per MJ), though still lower than current f...

En este trabajo se evaluo el efecto de las condiciones hidrodinamicas a diferentes tasas de aireacion (1.4, 1.8 y 2.3 vvm) y la geometria de dos fotobiorreactores anulares (airlift y columna de burbujeo) con iluminacion interna sobre el crecimiento celular, remocion de nitrogeno y produccion de lipidos de Chlorella vulgaris. Se aplico un modo de cultivo con reduccion de nitrogeno en dos etapas para fomentar la acumulacion de lipidos. El inoculo se cultivo con una concentracion inicial de 90 mg L−1 de N-NH+4 (suficiencia de nitrogeno) y al termino de la fase exponencial se diluyo en fotobiorreactores con volumen de 11 L, a concentracion de 20 mg L−1 de N-NH+4 (reduccion de nitrogeno). Los resultados mostraron que con tasas de aireacion similares el regimen hidrodinamico en ambos equipos fue apreciablemente diferente, presentandose mayor turbulencia en airlift. Sin embargo, el aumento en la tasa de corte y en la agitacion no causo dano celular, ni fotoinhibicion. Se alcanzaron crecimientos celulares de hasta 12×106 cel mL−1, el consumo de nitrogeno se mantuvo siempre entre el 16 y el 19% y las tasas de corte se calcularon en el rango de 120-340 s−1 . Las mayores productividades de lipidos se alcanzaron a 1.8 vvm con (0.650 y 0.528) mg·L−1 d−1 en columna de burbujeo y airlift anulares, respectivamente.

When traditional process-design methodologies are applied to the conceptual design of biorefineries, the main drivers for their development are poorly considered. Biorefinery plants are facilities integrating biomass-conversion processes and equipment to produce fuels, energy, chemical intermediates, and end-use products. Appropriate design tools must consider their sustainability in terms of: (a) potential displacement of fossil fuels and materials, (b) mitigation of environmental impacts, (c) renewability, (d) economic feasibility, (e) biodiversity preservation, and (f) social responsibility. Performance on addressing these drivers should be assessed from appropriate environmental, social and economic perspectives. This paper illustrates the application of a methodology that incorporates these principles in the conceptual design of a switchgrass-based biorefinery. The results show that the proposed design complies with the definition of sustainability in 10 out of 11 indicators. The indicator Baseline-emissions reduction fell in the unsustainable range mainly due to the high SO2-eq and PO4-eq emissions over the life cycle of the proposed system, derived from fertilizers and pesticides application. The techno-economic analysis showed economic feasibility of the biorefinery when the minimum acceptable rate of return is below 12%. The proposed methodology shows great potential as a valuable complement to classic process-design methodologies, by quantifying their sustainability during the conceptual-design stage, and requiring little extra effort beyond performing the techno-economic analysis and a life cycle assessment.

Jatropha is still considered a strong candidate for the production of second generation biofuels, despite recent large-scale failures worldwide to achieve high and consistent seed yields on the field. A short term alternative for making jatropha-based businesses profitable under current modest seed yields is by harnessing the whole biomass under a biorefinery concept, using state-of-the-art technology. Several studies have explored various ways to harness the jatropha biomass as feedstock for diverse processes such as densification, pyrolysis, carbon activation, gasification, combustion, anaerobic digestion, fermentation, solid-state fermentation, and extraction and purification of compounds. In this review we consolidate the publicly available information and present an analysis of what seems the best way to integrate these processes under a biorefinery concept. A concrete proposal of a state-of-the-art jatropha-based whole-crop biorefinery is made, together with recommendations of further research required to fill the gaps that may lead to even more profitable jatropha-based whole-crop biorefinery systems.

Microalgae have been largely used as a source of human and animal food, essential fatty acids for the treatment and prevention of diseases, and as a source of pigments for natural colorants. They have also been considered a promising feedstock for the production of liquid biofuels, as they can achieve oil yields considerably higher than oilseed crops. However, microalgae-based biofuels are not yet economically feasible due to high operating costs and large energy demands, which result in poor net energy returns and unattractive internal rates of return. Biomass cultivation, nutrient recycling, water usage, and biomass harvesting are critical process issues. Refining the biomass in its various constituents presents an opportunity for making microalgal lipids economically viable for bioenergy production, supported on high added-value co-products. Hence, this review aims to consolidate the public information on microalgal biomass processing and to present an analysis of the best options for integrating individually studied processes in an energy-driven biorefinery. From this analysis, a preliminary proposal of a biorefinery flow diagram is presented, along with recommendations for further research and technology development in the critical areas for accelerating the development of microalgae biorefineries.

This study was conducted to determine the genetic variation and relationships between American accessions of Jatropha curcas from different origins. The accessions from El Salvador showed the lowest plant proportions, while two of the Mexican accessions (MCT10 and MCE06) showed the highest values in oil yield. The principal component analysis explained 75.99% of the total variation in three components. Repeatability analysis showed a low effect of the environment on the characters associated with oil yield (R = 0.99), 100-seed weight (R = 0.98) and seed volume (R = 0.97), indicating a high level of diversity among accessions and the feasibility of finding desirable characters in each collection, while offering useful information for the selection of parental plants for use in crop improvement programs.

A model is proposed to relate the flow structure in the wake behind a leading bubble with the hydrodynamic force acting on the trailing bubble rising in-line. The model is valid at separation distances between bubbles (s) within the same order of magnitude as their diameters (dB) (2.5 ≤ s/dB ≤ 14.5) and moderate-to-large particle Reynolds numbers (50 ≤ Re1 ≤ 300). An equation for the axial velocity profile in the wake of a spherical bubble was proposed in the form of an analytical approximation, but incorporating a theoretically reasoned artificial origin, which was fitted to numerical data. This equation, once substituted in a general hydrodynamic force model, resulted in a predictive equation explaining quantitatively the in-line interaction of a pair of bubbles in terms of the average axial velocity in the leading bubble wake. Moreover, the force experienced by the leading bubble due to the trailing bubble presence was obtained, and the theoretical equilibrium distances between the bubbles were calcula...

The present work presents a first characterization of the oil from the Moringa (Moringa oleifera) kernel as a potential candidate for biodiesel production. Moringa is an indigenous tree in the Yucatan Peninsula in Mexico, where there is a nascent biodiesel industry. Several extraction methods are compared in terms of the extraction yields, including solvent extraction (n-hexane and ethanol), and supercritical extraction (Sc-CO2). The results are also compared against previ- ously reported data. For supercritical extraction pressures of 200 to 400 bar and temperatures of 40℃ and 60℃ were tested. Gas Chromatography analysis reveals that the main fatty acids in Moringa oil are oleic acid (69%), palmitic acid (10%), and stearic acid (8%).

Sustainability today is a ubiquitous word; in its relatively brief life, the concept has taken many shapes, so that today the word is frequently used, sometimes overused, and many times misused. Proposing good indicators to measure sustainability is a challenging task; the most common methodologies for evaluating the sustainability of processes and products do so by comparing various designs and selecting the best option, according to predefined criteria. The methodology herein proposed uses a sustainability scale that is based on an absolute reference, and is normalized for sustainability indicators applicable to biorefineries. The resulting framework consists of 5 indicator categories, and a total of 14 metrics; this tool can be used to evaluate the sustainability of biorefinery designs, and also for ex-post evaluations of performance. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd

The current design and performance evaluation methods for vent and reflux condensers include minimum safety factors of 30% or more. These oversized condensers incur high capital and operational costs. Experimental data are fundamental in order to evaluate these design methodologies. This paper presents a new set of experiments performed in a steam/air vent condenser at subatmospheric pressures. The experimental apparatus consists of a vertical, double-pipe condenser with a length of 3 m and inner diameter of 0.028 m. The produced experimental data allow the evaluation of the local heat transfer coefficients and the heat-flux profile on the coolant side. After comparing the predictions of the two main methods for the design of vent and reflux condensers, that is, the film method and the equilibrium method as modified by Webb et al. (1996), it becomes apparent that the film method is always better and should be always preferred when diffusive data are available. The equilibrium method error in predicting th...

Chlorella vulgaris and Scenedesmus obliquuswere grown in artificial-wastewater using a new nitrogen-limitation strategy aimed at increasing lipid productivity. This strategy consisted in a multi-stage process with sequential reduction of N-NH4 concentration (from 90 to 60, 40, and 20 mg.L-1) to promote a balance between cell growth and lipid accumulation. Lipid productivity was compared against a reference process consisting of nitrogen reduction in two stages, where the nitrogen concentration was suddenly reduced from 90 mg.L-1 to three different concentrations (10, 20, and 30 mg.L-1). In the multi-stage mode, only C. vulgaris exhibited a net lipid-productivity increase. Lipid content of S. obliquus did not present a significant increase, thus decreasing lipid productivity. The highest lipid productivities were observed in the two-stage mode for both S. obliquus and C. vulgaris (194.9 and 133.5 mg.L-1.d-1, respectively), and these values are among the highest reported in the literature to date.

Life-cycle assessment (LCA) has been applied to many biofuel and bioenergy systems to determine potential environmental impacts, but the conclusions have varied. Different methodologies and processes for conducting LCA of biofuels make the results difficult to compare, in-turn making it difficult to make the best possible and informed decision. Of particular importance are the wide variability in country-specific conditions, modeling assumptions, data quality, chosen impact categories and indicators, scale of production, system boundaries, and co-product allocation. This study has a double purpose: conducting a critical evaluation comparing environmental LCA of biofuels from several conversion pathways and in several countries in the Pan American region using both qualitative and quantitative analyses, and making recommendations for harmonization with respect to biofuel LCA study features, such as study assumptions, inventory data, impact indicators, and reporting practices. The environmental management implications are discussed within the context of different national and international regulatory environments using a case study. The results from this study highlight LCA methodology choices that cause high variability in results and limit comparability among different studies, even among the same biofuel pathway, and recommendations are provided for improvement.

This paper presents a unique sustainability analysis of one of the first attempts to establish a biodiesel industry in Mexico. From 2008, several companies established medium to large-sized Jatropha curcas plantations in Yucatan, hiring local peasants to carry out the agricultural work. After five years, the plantations were abandoned due to poor seed yields and a lack of key knowledge for large-scale cultivation. Based on a multidisciplinary approach, we performed a three-dimensional sustainability evaluation of the potential biodiesel production chain, which included household interviews, a socioeconomic survey, and a life-cycle assessment (LCA). We identified both negative and positive effects in the three dimensions analyzed. Socially and culturally, the local peasant families understood sustainability as their ability to preserve their traditional lifestyle, and associated environmental services with their sense of identity. They therefore considered the jatropha plantations to be positive for sustainability, since they brought income, even though some perceived damage to the natural resources of the surrounding areas. Economically, peasants’ annual household income increased by approximately $1080 USD due to the increased salaries paid by the jatropha companies. The LCA predicted large savings of greenhouse gas emissions (>50% compared to fossil diesel), but also potential negative impacts in some categories (human/ecological toxicity and eutrophication potentials) associated with the use of mineral fertilizers, insecticides, and pesticides applied during the cultivation stage. Biodiesel production would be potentially energetically self-sufficient, in addition to producing a 40% energy surplus. Finally, even though the sustainability indicators suggested a positive overall assessment, the reality was that the jatropha projects failed because they were predicated on unrealistically optimistic projections and poor agronomic knowledge of the plant.