Preliminary Techno-economic Analysis Research Articles

Preliminary techno-economic analysis of three typical decentralized composting technologies treating rural kitchen waste: a case study in China

Preliminary techno-economic analysis of three typical decentralized composting technologies treating rural kitchen waste: a case study in China

Redox-Mediated Electrodialysis for Resource Recovery and Energy-Efficient Desalination

In the chemical and biochemical manufacturing industry, separation processes are amongst the most energy-demanding processes. Electrochemical separations have been growing in interest as promising candidates for both downstream processing for resource recovery and producing clean water due to their energy-efficient, environmentally benign, and modular features.1 Leveraging a sustainable redox reaction, we developed a redox-mediated electrodialysis system for energy-efficient desalination coupled with resource recovery of valuable resources such as lithium, and even biomolecules.2, 3 Our proposed redox-mediated electrodialysis system utilizes a reversible redox reaction as a driving force of salt removal at a much lower voltage than a water-splitting reaction (>1.2 V). As the redox materials are reduced or oxidized, all charged species migrate across the membranes to balance the charge in the electrolyte compartment. As the redox materials circulate in the cathode and anode compartments, they sustainably regenerated without additional regeneration steps, one of the major bottlenecks for industrializing the electrosorption system. We demonstrated the redox-mediated electrochemical system for resource recoveries such as simultaneous lithium recovery from brine3 and valorization of whey proteins and lactose from whey waste.2 Especially for the valorization of whey waste, our system treated 99% of salt from the whey solution within a single step and recovered > 98% of various whey proteins (e.g., valuable protein contents such as beta-lactoglobulin, alpha-lactalbumin, and lactose). The preliminary techno-economic analysis confirmed the economic potential of redox-mediated ED with 51−73% lower energy consumption compared to conventional ED. Overall. we envision the system can become a breakthrough in tackling the environmental challenges coupled with the limited resources. Kim, N.; Jeon, J.; Chen, R.; Su, X., Electrochemical separation of organic acids and proteins for food and biomanufacturing. Chemical Engineering Research and Design 2022, 178, 267-288.Kim, N.; Jeon, J.; Elbert, J.; Kim, C.; Su, X., Redox-mediated electrochemical desalination for waste valorization in dairy production. Chemical Engineering Journal 2022, 428, 131082.Kim, N.; Su, X.; Kim, C., Electrochemical lithium recovery system through the simultaneous lithium enrichment via sustainable redox reaction. Chemical Engineering Journal 2021, 420, 127715.

A consolidated bioprocess design to produce multiple high-value platform chemicals from lignocellulosic biomass and its technoeconomic feasibility

5-Hydroxymethyl furfural (HMF) and furfurals are DOE-listed platform chemicals that can be derived from the renewable carbon in the lignocellulosic biomasses and have the potential to replace petroleum-derived alternatives. High substrate cost and use of expensive solvents limit the economic feasibility of bio-based HMF production on an industrially relevant scale. The study presents an experimental optimized condition that maximizes the chemical-free production of HMF and furfurals without lowering the yield of total fermentable sugars from Saccharum bagasse. Hydrothermal pretreatment at 210 °C for 15 min yielded approximately 10%, 12%, and 46% of HMF, furfurals, and fermentable sugars per gram of dry biomass, respectively. Additionally, the study proposes a consolidated bioprocess model to produce and recover four high-value bioproducts i.e., HMF, furfurals, ethanol, and acetic acid based on the experimental results and evaluates its technoeconomic feasibility considering HMF as the main product. The minimum selling price (MSP) of HMF was estimated to be 930.6 USD/t which is competitive with its petroleum-derived precursor alternative p-xylene (1,113 USD/t). The sensitivity analysis performed for the process parameters suggests that pretreatment cost and revenues from coproducts immensely influence the MSP of HMF. The preliminary technoeconomic analysis performed on the consolidated bioprocess design indicates that additional revenue streams from diversified coproducts in biorefineries aid in lowering the MSP of high-value bioproducts.

(Digital Presentation) Electron Mediators for the Reductive Leaching of Chalcopyrite: Replacing Smelting with Electrolysis for Copper Production

Copper is expected to be in high demand in the coming decades due to the emergence of wind and solar technologies, which require about five times as much copper as traditional energy sources. Copper, however, is expected to be in short supply in the coming decades due to the high costs associated with the mining, concentrating, and processing of chalcopyrite (CuFeS2), which accounts for about 70% of all copper reserves. This work introduces a potentially transformative hydrometallurgical process for domestic production of copper from CuFeS2. Commercialization of such a process could sustain a high rate of copper production throughout the 21st century. Chalcopyrite is reacted with a redox couple to enable the rapid, clean, and complete recovery of copper. The reductant may be regenerated by an electrolysis unit.Reactions 1 and 2 show the direct electrochemical reduction of CuFeS2 to Cu2S and Cu0, respectively 2CuFeS2 + 6H+ + 2e- → Cu2S + 2 Fe2+ + 3 H2 S [1]Cu2S + 2H+ + 2e- → 2 Cu0 + H2 S [2]The cathodic reduction of CuFeS2 competes with the hydrogen evolution reaction and therefore becomes inefficient at current densities exceeding 40 mA/cm2. Conversely, the cathodic reduction of an electron mediator circumvents the hydrogen evolution reaction and enables current densities exceeding 100 mA/cm2. Figure 1 shows a result that highlights the use of an electron mediator to facilitate the rapid and complete reduction of chalcopyrite, followed by the dissolution of the resultant solid product into sulfuric acid for the complete recovery of copper. In figure 1a, the release of Fe2+ ions to solution during the progression of the reaction with electron mediator is shown. In all cases, the solution contains 4M H2SO4 and various loadings of CuFeS2 concentrate. Error bars show standard deviations of replicates in triplicate. The reaction nearly goes to completion in 10 minutes. In figure 1b, the subsequent extraction of Cu2+ from mineral products dissolution into 1M H2SO4. The resulting concentration of copper in the sulfuric acid is amenable to electrowinning. Results are shown for high loadings of chalcopyrite, within a practical range for economic viability.In this work, we report successful results from two redox couples that can be effectively regenerated via electrolysis. A preliminary technoeconomic analysis is discussed, identifying potential opportunities as well as technical challenges. Figure 1

Fine-tuned regulation of photosynthetic performance via γ-aminobutyric acid (GABA) supply coupled with high initial cell density culture for economic starch production in microalgae

Microalgal starch is considered as renewable and sustainable feedstock for biofuels and biorefinery. High cell density culture is favourable for photoautotrophic starch production in microalgae in the aspects of productivity and economy, but it often encounters low starch content or extra stress exposure that limits the production. This study aimed to economically enhance photosynthetic starch production from CO2 fixation in a green microalga Tetraselmis subcordiformis by regulating photosynthetic stress status with a signalling molecule γ-aminobutyric acid (GABA) combined with the application of high initial cell density culture. By increasing initial cell density (ICD) from the normal of 1.1 g L−1 (NICD) to as high as 2.8 g L−1 (HICD), the starch content, yield, and theoretical productivity were improved by 7%, 63%, and 42%, respectively. The addition of GABA under HICD resulted in 14%, 19%, and 26% of further enhancement in starch content, yield, and theoretical productivity, respectively. GABA exhibited distinct regulatory mechanisms on photosynthesis and stress status under HICD relative to NICD. GABA augmented excessive light energy absorption and electron transfer through photosystem II that reinforced the photoinhibition under NICD, while alleviated the stress reversely under HICD, both of which facilitated starch production by enabling a suitable stress status while simultaneously maintaining a sufficient photosynthetic activity. The increase of ICD and/or GABA supply particularly boosted amylopectin accumulation, leading to the changes in starch composition and was more favourable for fermentation-based biofuels production. Preliminary techno-economic analysis showed that the highest net extra benefit of 9.64 $ m−3 culture could be obtained under HICD with 2.5 mM GABA supply where high starch content (62%DW) and yield (2.5 g L−1) were achieved. The combined HICD-GABA regulation was a promising strategy for economic starch production from CO2 by microalgae for sustainable biomanufacturing.Graphical

Direct nitrogen stripping and upcycling from anaerobic digestate during conversion of cheese whey into single cell protein

The environmental impact of the dairy industry is heavily influenced by the overproduction of nitrogen- and carbon-rich effluents. The present study proposes an innovative process to recover waste contaminated nitrogen from anaerobic digestate while treating excess cheese whey (CW) and producing high-quality, clean single cell protein (SCP). By relying on direct aeration stripping techniques, employing an airflow subsequently used in the aerobic cheese whey fermentation step, the investigated process was able to strip 41–80% of the total ammonium nitrogen (N-NH4+) from liquid digestate. The stripped ammonia gas (NH3) was completely recovered as N-NH4+ in the acidic CW, and further upcycled into SCP having a total protein content of 74.7% and a balanced amino acids profile. A preliminary techno-economic analysis revealed the potential to directly recover and upcycle nitrogen into SCP at costs (4.3–6.3 €·kgN−1) and energetic inputs (90–132 MJ·kgN−1) matching those of conventional feed and nitrogen management processes.

Production of marine biofuels from hydrothermal liquefaction of sewage sludge. Preliminary techno-economic analysis and life-cycle GHG emissions assessment of Dutch case study

The aim of this paper is to evaluate the costs and GHG emissions of advanced biofuels production through hydrothermal liquefaction (HTL) of sewage sludge in The Netherlands targeting the marine fuels market. The process evaluated consists of a distributed configuration of regional HTL plants co-located with wastewater treatment plants, with centralized hydrotreating co-located with an existing refinery at the Port of Rotterdam. The process is simulated in ASPEN + based on published experimental data and the mass and energy balances are used as input for techno-economic and environmental evaluation. Lifecycle GHG emissions of the HTL and hydrotreating processes are estimated using consequential modelling principles and background data from the Ecoinvent database and compared with the business-as-usual scenario of sludge mono-incineration and fossil marine fuels production. The results indicate that the HTL + hydrotreating configuration has potential to deliver on-spec marine biofuels at a minimum fuel selling price between 410 and 1300 EUR/t, being at least 3 times more beneficial compared to the business-as-usual scenario from a GHG emissions perspective. Future work is recommended to optimize the size and location of the HTL plants in order to decrease capital costs and to address uncertainties regarding the sludge gate fee and the costs associated with the aqueous and solid by-products treatment. The results indicate the potential of such configuration in locations with relatively high population density and good transport infrastructure. This can be the case of port areas around the North Sea with access to offshore renewable electricity for hydrogen production, where drop-in marine biofuels are expected to play a role with the increasing share of renewables in the marine fuels mix.

Electro-Fenton treatment of contaminated mine water to decrease thiosalts toxicity to Daphnia magna

Treatment of organic contaminants using the electro-Fenton (EF) process is efficient but generates toxic by-products. The aim of the present study was to assess the residual toxicity associated to the treatment of real mine effluents using EF and to perform a preliminary techno-economic analysis to compare the costs of different techniques. Two mine effluents from northern Quebec with different concentrations of thiosalts (MElow and MEhigh) were tested for acute toxicity to Daphnia magna, before and after EF treatment. The higher toxicity of untreated MElow compared to MEhigh, despite its lower thiosalts content (58 vs 199 mg/L), suggests the presence of an unidentified toxic species, which was removed during EF treatment, or that higher thiosalts concentrations mitigate the toxicity of other toxicants. EF treatment of MEhigh, initially non-acutely toxic (50% mortality), resulted in the elimination of D. magna mortality. A preliminary techno-economic analysis conducted for northern Quebec vs the rest of Canada and the USA showed that energy consumption was the main contributor (52–95%) to the total operating costs. Electricity-related costs nearly doubled (55%) for northern Quebec relative to the rest of Canada. These findings provide new insights for the potential application of the EF for the treatment of thiosalts in mine water, for operations in central jurisdictions and in remote northern areas.

Process optimization, scale-up studies, economic analysis and risk assessment of phenolic rich bioactive extracts production from Carica papaya L. leaves via heat-assisted extraction technology

This work investigated the influence of process variables of extraction temperature (35–55 °C), solid to liquid ratio (1:20–1:50 g/mL) and time (100–200 min) on the total phenolic content (TPC) and yield (EY) of Carica papaya leaves (CPL) extracts using Box-Behnken experimental design available in Design Expert software. Bi-objective process optimization was also carried out using the desirability function algorithm. The optimum process variables were later used to design an integrated process for the production of CPL extracts with the assistance of SuperPro Designer software. Scale-up studies and economic analysis for CPL extracts production were investigated in the range of 0.638–20.431 × 103 kg CPL extracts/y to determine the most economically feasible production capacity based on the minimum unit production cost (UPC) of CPL extracts. The risk and sensitivity analyses of the most economically feasible production scale were carried out using the Monte Carlo simulation in Oracle Crystal Ball software. Process variables had notable influences on the TPC and EY of CPL extracts. The extraction temperature of 35 °C, solid to liquid ratio of 40.25 g/mL and time of 100 min gave the optimum TPC of 74.65 mg GAE/g d.b and EY of 18.76 % (w/w). HPLC results indicated that CPL extracts were rich in gallic, betulinic, chlorogenic, ellagic, ferulic and caffeic acids. The designed integrated process showed similar behavior with the laboratory scale of 0.18758 g CPL extracts/batch. The preliminary techno-economic analysis indicated that plant capacity has a strong dependence on the material & energy demands and process economics. Plant capacity of 19.857 × 103 kg CPL extracts/y possessed the least UPC and was selected as the most economically feasible scale. The certainty of obtaining base case UPC value of 525.21 US$/kg CPL extracts was 75.20%. Sensitivity analysis showed that extracts recovery, CPL/water, centrifuge purchase cost, extraction time, extractor purchase cost and extraction temperature contributed -5.3 %, +42.8%, +4.0%, +47.1%, +0.1%, and +0.5%, respectively to the variance in UPC of CPL extracts.

Enhanced Slow Sand Filtration for the Removal of Micropollutants from Groundwater

Remote areas, where centralized water supply cannot reach, rely heavily on decentralized supply systems such as slow sand filters (SSFs). Groundwater used to be a reliable water source; yet, the advent of micropollutants (MPs) has raised concerns over its quality. In this study, an enhanced slow sand filtration utilizing graphene oxide (GO)-coated sand prepared via a simple thermal method was employed to remove two representative MPs, atrazine (ATZ) and atenolol (ATL), from real groundwater for drinking water treatment. The removal of ATZ and ATL was studied in a bench-scale enhanced SSF using GO-coated sand in comparison with the conventional plain sand. The results showed that the GO-coated sand performed better in the removal of ATZ, ATL, and total organic carbon (TOC), as well as turbidity reduction. Moreover, in order to study the role of the schmutzdecke in MPs' removal small lab-scale columns with and without schmutzdecke growth were set up. The results indicated the enhanced removal capacity of the coated sand toward ATZ, ATL, and TOC could mainly be attributed to the GO coating layer, not the schmutzdecke. Hence, if the coated sand is to be used in field SSFs for the removal of organic contaminants, the schmutzdecke growing phase might not be needed. A preliminary techno-economic analysis was performed to evaluate the practicability of enhanced SSF and GO was found to dominate the overall cost. For a community-level or a household-level SSF, the extra cost using GO-coated sand may be $0.34 and $3.25 per m3 of water if the GO price is $10 and $100 per kg, respectively.

(Invited) Stack Development and Scale-up for Protonic Ceramic Fuel Cells

Under the ARPA-E REBELS program, the Colorado School of Mines (CSM), together with industrial partner Fuel Cell Energy/Versa Power Systems (FCE/VPS) have advanced protonic ceramic fuel cell (PCFC) technology from the small (<1 cm2) laboratory button-cell scale to the large-area (81 cm2) industrial manufacturing scale utilizing low-cost, volume-qualified processes. Presently, the team is pursuing the world’s first demonstration of a large-area, ~500W-1kW natural gas-fueled PCFC stack prototype by leveraging these large-area cells with FCE’s low-cost Compact Stack Architecture (CSA). Our progress towards key scale-up demonstration goals is summarized in Table 1. In this presentation, we review the progress and major learnings achieved during this scale-up initiative. We highlight several areas where important technological and scientific risks have been mitigated, as well as areas where key questions remain to be addressed. Finally, preliminary techno-economic analysis and potential market opportunities for PCFC technology will be presented and discussed. Figure 1

Techno-Economic Assessment of Polysaccharide Extraction from Baobab: A Scale Up Analysis

This research studied the commercial exploitation of an indigenous African crop in order to formulate high value products, with a potential significant impact on the local economy. More specifically, the present work investigated the extraction of polysaccharides from baobab in a bench-scale unit, focusing on the overall yield and the techno-economic assessment of the extraction process. Preliminary technoeconomic analysis for two scenarios (with and without ethanol recycling) was performed to determine the economic viability of the process and the development of the baobab market both in Nigeria and the UK. A full economic analysis was undertaken for each of the two scenarios, considering all operating and capital costs, and the production cost of baobab polysaccharides was estimated based on a constant return on investment. Combining the operating cost with the average polysaccharide yield, the minimum profitable selling price in the UK was estimated to be between £23 and £35 per 100 g of polysaccharide, which is comparable to the commercial selling price of high purity polysaccharides. An assessment of a scaled-up plant was also performed under Nigerian conditions and the results showed that such an investment is potentially viable and profitable, with a minimum profitable selling price of £27 per 100 g, a value comparable to the UK-based scenarios.

Electrocatalytic upcycling of polyethylene terephthalate to commodity chemicals and H2 fuel

Plastic wastes represent a largely untapped resource for manufacturing chemicals and fuels, particularly considering their environmental and biological threats. Here we report electrocatalytic upcycling of polyethylene terephthalate (PET) plastic to valuable commodity chemicals (potassium diformate and terephthalic acid) and H2 fuel. Preliminary techno-economic analysis suggests the profitability of this process when the ethylene glycol (EG) component of PET is selectively electrooxidized to formate (>80% selectivity) at high current density (>100 mA cm−2). A nickel-modified cobalt phosphide (CoNi0.25P) electrocatalyst is developed to achieve a current density of 500 mA cm−2 at 1.8 V in a membrane-electrode assembly reactor with >80% of Faradaic efficiency and selectivity to formate. Detailed characterizations reveal the in-situ evolution of CoNi0.25P catalyst into a low-crystalline metal oxy(hydroxide) as an active state during EG oxidation, which might be responsible for its advantageous performances. This work demonstrates a sustainable way to implement waste PET upcycling to value-added products.

Conversion of pilot plant derived 2G ethanol cellulosic stillage to value-added chemicals

For second-generation (2 G) cellulosic ethanol production to be sustainable and viable, there is the need to value-add to the stillage. Here, pilot plant-derived 2G ethanol sugarcane bagasse stillage (BS) and eucalyptus stillage (ES) was transformed into valuable products using hydrothermal liquefaction (HTL) at 300 °C and 20 bar with Pd/C and K2CO3. BS produced oil, phenolic monomers, and organic acid yields of 32 %, 49 % and 25 % respectively, while yields for ES were lower. Catechol constituted 43 % of the total phenolic content for BS. Recycling the aqueous phase (containing acetic, formic, lactic, and propionic acids) improved phenol, guaiacol and catechol yields. Oil stability tests indicated a significant drop in oil yield with aging, but there was no significant change in higher heating value. A preliminary techno-economic analysis suggests that the potential value of producing 2G ethanol and products (including fertilizer) from BS is three times that of depithed sugarcane bagasse. This study demonstrated a potential technology to convert 2 G cellulosic ethanol stillage to value-added chemicals, which not only improved the efficiency and profitability of 2G ethanol production but reduced organic contaminants synthesis.

Potential Waste Heat Recovery Analysis From Molten Steel Slag: The Case Study of Sidenor Steelworks in Basauri (Spain)

Abstract Every day, a huge amount of energy is released into the atmosphere in the form of waste heat. The search for a cleaner and more efficient society, not only at the industrial level but also at the domestic level, should avoid this type of emissions. Steelmaking is an example of an industrial sector with high optimization potential in energy management. In this line, this work presents the main outcomes of the investigation carried out in the search of a technical solution for heat capture and reutilization from one of the main waste heat streams in the steelworks, the molten slag. For this purpose, a piping system embedded in the slag pit soil is proposed as a satisfactory solution for the heat capture operation. Besides, the internal applicability of this recovered heat is also addressed. Overall, the analysis carried out allows the identification of the maximum energy that can be recovered from the slag if the proposed technology is implemented (around 306 kWht per casting, which represents 6.3% of the total available energy). The work is completed with a preliminary techno-economic analysis which has shown a depreciated payback period of the proposed technology below 7 years.

A novel solar hydrogen production system integrating high temperature electrolysis with ammonia based thermochemical energy storage

In this paper, a novel solar hydrogen production system integrating high temperature electrolysis (using solid oxide electrolyzer cell) with ammonia based thermochemical energy storage is proposed for the first time. Without a significantly high concentration ratio, the thermochemical energy storage can upgrade relatively low-temperature solar energy to high-temperature reaction heat for high temperature electrolysis (HTE). Furthermore, thermal coupling of ammonia based thermochemical energy storage system, sCO2 Brayton cycle and HTE will result in substantially higher fuel production efficiency as compared to conventional low-temperature water electrolysis. A system model, including ammonia based thermochemical energy storage, sCO2 Brayton cycle and solid oxide electrolyzer cell (SOEC) system, has been developed using the Aspen Plus software implemented with user-defined Fortran subroutines. The models including reactors, sCO2 Brayton cycle and SOEC have been validated by comparing the model-generated results with the data from references. The effects of the endothermic reactor inlet temperature T2, charging loop ammonia mass flow rate ṁc, turbine inlet temperature T11 and current density J on the system performance have been investigated parametrically. The results show that the solar to hydrogen efficiency ηSTH increases with T2, T11 and J increasing. In addition, there is an optimum ηSTH by varying ṁc. Further, a maximum ηSTH = 26% has been obtained by optimizing the parameters in predefined ranges, which is 7% higher than the state-of-the-art of the solar HTE with TES. Based on a preliminary techno-economic analysis, the capital cost of the proposed system is estimated to be 9.28 $/kg H2, which is 18.9% lower than a typical photovoltaic based electrolyzer system. Therefore, the proposed system is economically feasible.

Carbon-based conductive materials facilitated anaerobic co-digestion of agro waste under thermophilic conditions

Management of agro-waste is a major challenge globally due to inefficient disposal techniques, which concominantly leads pollution and loss of renewable bioenergy. Anaerobic digestion of agro-waste is one of the ways to tackle this problem but hindered by the recalcitrant nature of agro-waste. This study investigated the effect of granular activated carbon (GAC) and granular biochar (GBC) addition to enhance the thermophilic anaerobic co-digestion of wheat husk and sewage sludge. The conductive materials (particle size: 2–5 mm) were added separately at five different concentrations: 10, 20, 30, 40, 50 g/Linoculum. The findings revealed that samples amended with GAC and GBC at 20 g/L dosage had the highest biogas yield of 263 and 273 mL/gVSadded, respectively, corresponding to 22 and 27% higher yield than the control. Additionally, a shorter lag phase was observed in both cases compared to the Control. However, the GBC amended samples showed relatively stable biogas production compared to GAC and consistent results regarding pH, alkalinity, total volatile fatty acids, and soluble chemical oxygen demand. The preliminary techno-economic analysis indicates that addition of GAC or GBC may not be feasible and require other innovative engineered solutions for the addition of conductive materials. This study confirms that GAC and GBC amendments enhance the biogas productivity and process stability in anaerobic digestion of recalcitrant agro-waste under the high-temperature regime and calls for further research in this direction.

Improving the Anaerobic Digestion of Swine Manure through an Optimized Ammonia Treatment: Process Performance, Digestate and Techno-Economic Aspects

Swine manure mono-digestion results in relatively low methane productivity due to the low degradation rate of its solid fraction (manure fibers), and due to the high ammonia and water content. The aqueous ammonia soaking (AAS) pretreatment of manure fibers has been proposed for overcoming these limitations. In this study, continuous anaerobic digestion (AD) of manure mixed with optimally AAS-treated manure fibers was compared to the AD of manure mixed with untreated manure fibers. Due to lab-scale pumping restrictions, the ratio of AAS-optimally treated manure fibers to manure was only 1/3 on a total solids (TS) basis. However, the biogas productivity and methane yield were improved by 17% and 38%, respectively, also confirming the predictions from a simplified 1st order hydrolysis model based on batch experiments. Furthermore, an improved reduction efficiency of major organic components was observed for the digester processing AAS-treated manure fibers compared to the non-treated one (e.g., 42% increased reduction for cellulose fraction). A preliminary techno-economic analysis of the proposed process showed that mixing raw manure with AAS manure fibers in large-scale digesters could result in a 72% increase of revenue compared to the AD of manure mixed with untreated fibers and 135% increase compared to that of solely manure.

Efficient One-Step Conversion of a Low-Grade Vegetable Oil to Biodiesel over a Zinc Carboxylate Metal-Organic Framework.

In this study, a metal–organic framework, namely, Zn3(BTC)2 (BTC = 1,3,5-benzenetricaboxylic acid), was solvothermally synthesized and employed as a catalyst for biodiesel production from degummed vegetable oil via a one-step transesterification and esterification reaction. The resulting Zn3(BTC)2 particles exhibit a well-defined triclinic structure with an average size of about 1.2 μm, high specific surface area of 1176 m2/g, and thermal stability up to 300 °C. The response surface methodology–Box–Behnken design (RSM–BBD) was employed to identify the optimal reaction conditions and to model the biodiesel yield in relation to three important parameters, namely, the methanol/oil molar ratio (4:1–8:1), temperature (45–65 °C), and time (1.5–4.5 h). Under the optimized reaction conditions (i.e., 6:1 methanol/oil molar ratio, 65 °C, 4.5 h), the maximum biodiesel yield reached 89.89% in a 1 wt % catalyst, which agreed very well with the quadratic polynomial model’s prediction (89.96%). The intrinsic catalytic activity of Zn3(BTC)2, expressed as the turnover frequency, was found to be superior to that of other MOF catalysts applied in the transesterification and esterification reactions. The reusability study showed that the as-synthesized Zn3(BTC)2 catalyst exhibited good stability upon three consecutive reuses without a noticeable decrease in the methyl ester yield (∼4%) and any appreciable metal leaching (<5%). Furthermore, a preliminary technoeconomic analysis showed that the total direct operating cost for the kilogram-scale production of Zn3(BTC)2 is estimated to be US$50, which may sound economically attractive.

Xylose production and the associated integration for biocoal production

Abstract Xylose is the second most abundantly available sugar in nature next to glucose. It is one of the hemicellulose based (C5) sugars and is often discarded during the conversion of lignocellulosic biomass to biofuels. Xylose recovery as a coproduct has a great potential to reduce the overall production cost of biofuels through increased revenue and efficient utilization of biomass. A low-energy non-conventional xylose production process from the University of Louisville (UofL) uses a boron capturing agent to esterify xylose, isolate it from aqueous hydrolyzate stream, and recover xylose as a dry product under ambient process conditions. Effective integration of this xylose production as a pre-step for processing biomass to biofuels such as biocoal has significant advantages in terms of enhanced product quality and improved economics. The xylose separation process yields modified biomass with stripped of hemicellulose and alkaline ash leading to reduced oxygen content and has higher energy density. TGA study showed that such modified biomass needs low energy input for carbonization during the torrefaction process. This modified biomass doubles up as a binder during the densification process to produce biocoal, thus significantly minimizing the cost of biocoal production. The preliminary techno-economic analysis for a biocoal plant based on wood chips indicate that xylose integration imparts greater viability of the plant even when the raw material costs are more than $40 per ton while significantly cutting down the payback time.