Green Production Process Research Articles

Metabolic engineering Yarrowia lipolytica for a dual biocatalytic system to produce fatty acid ethyl esters from renewable feedstock in situ and in one pot.

Given the grave concerns over increasing consumption of petroleum resources and dramatic environmental changes arising from carbon dioxide emissions worldwide, microbial biosynthesis of fatty acid ethyl ester (FAEE) biofuels as renewable and sustainable replacements for petroleum-based fuels has attracted much attention. As one of the most important microbial chassis, the nonconventional oleaginous yeast Yarrowia lipolytica has emerged as a paradigm organism for the production of several advanced biofuels and chemicals. Here, we report the engineering of Y. lipolytica for use as an efficient dual biocatalytic system for in situ and one-pot production of FAEEs from renewable feedstock. Compared to glucose with 5.7% (w/w) conversion rate to FAEEs, sunflower seed oil in the culture medium was efficiently used to generate FAEEs with 84% (w/w) conversion rate to FAEEs by the engineered Y. lipolytica strain GQY20 that demonstrates an optimized intercellular heterologous FAEE synthesis pathway. In particular, the titer of extracellular FAEEs from sunflower seed oil reached 9.9 g/L, 10.9-fold higher than that with glucose as a carbon source. An efficient dual biocatalytic system combining ex vivo and strengthened in vitro FAEE production routes was constructed by overexpression of a lipase (Lip2) variant in the background strain GQY20, which further increased FAEEs levels to 13.5 g/L. Notably, deleting the ethanol metabolism pathway had minimal impact on FAEE production. Finally, waste cooking oil, a low-cost oil-based substance, was used as a carbon source for FAEE production in the Y. lipolytica dual biocatalytic system, resulting in production of 12.5 g/L FAEEs. Thus, the developed system represents a promising green and sustainable process for efficient biodiesel production. KEY POINTS: • FAEEs were produced by engineered Yarrowia lipolytica. • A Lip2 variant was overexpressed in the yeast to create a dual biocatalytic system. • Waste cooking oil as a substrate resulted in a high titer of 12.5 g/L FAEEs.

Knowledge Integration, Green Innovation, and Financial Performance

Developing green products and improving green production processes are critical in enhancing a company's environmental performance and sustainability. The sophisticated processes involved in green innovation have a steep learning curve, but its navigation has become essential for companies engaged in green operations. Drawing on the theories of organizational learning and dynamic capabilities, this paper presents our empirical analysis of 231 Chinese firms and suggests that the impact a firm's knowledge process integration has on environmental performance is mediated by its green product and process innovations capability. This study should help managers improve green innovation and financial performance.

(Invited) Exploring Synergistic Effects for High Performance Catalysts of Electrolytic Water Splitting

Hydrogen plays a key role in deep decarbonization to tackle the two–degree–scenario (2DS) set by the Paris Climate Agreement. It has been proposed that decarbonization through hydrogen economy could achieve half of the reduction in carbon dioxide emission required to realize the 2DS. Presently, the most popular and economical commercial process for H2 production is steam–methane reforming, which uses fossil fuels as the raw material and produces comparable amounts of CO2 as the by–product. It is definitely an environmental unfriendly and a non–sustainable H2 production process, and development of green H2 production is in urgent need. In this regard, renewable energy driven electrolytic water splitting has been gaining rapidly increasing popularity and is considered by many the most promising green H2 production process for future hydrogen economy infrastructure. It is also considered a necessary energy storage approach to resolve the detrimental unreliability and intermittency issues of renewable energies. The high cost of electricity however severely limits the prevailing of this technology, and cost–effective highly efficient and stable electrocatalysts, aiming to reduce the necessary working potential for cost competiveness, are critically important for the prevailing of the technology. For catalyst development, unary systems have been exhaustively explored and multi–component systems have advanced drastically, benefitting from the synergistic effects between constituent components. Engineering synergistic effects of multi-component catalysts is thus one key for breakthrough catalyst design. Here, several recent examples from our lab are presented to illustrate the strategy.

Entomopathogenic Fungi Biomass Production and Extracellular Biosynthesis of Silver Nanoparticles for Bioinsecticide Action

Entomopathogenic fungi are microbial agents of insect control in nature. They have been used as biologic strategies to manage insect invasion; however, the challenge is to maintain their shelf life and viability when exposed to high temperatures, ultraviolet radiation, and humidity. Synthesized silver nanoparticles (AgNPs) from fungal extracellular enzymes are an alternative using these microorganisms to obtain nanoparticles with insecticidal action. The present study evaluates the biomass production and the potential to synthesize silver nanoparticles using entomopathogenic fungi isolates. Sixteen isolates of entomopathogenic fungi were used in this study. The fungi pathogenicity and virulence were evaluated using the insect model Tenebrio molitor, at a concentration of 5 × 106 conidia/mL. The fungal biomass was produced in a liquid medium, dried, and weighed. The synthesis of silver nanoparticles was performed with aqueous extracts of the entomopathogenic fungi and silver nitrate solution (1 mM), following characterization by a UV/vis spectrophotometer, mean size, and polydispersity index. The results showed a significant variation in pathogenicity, virulence, and biomass production among the evaluated fungi isolates; however, only one of the isolates did not have the potential to synthesize silver nanoparticles. Pearson’s correlation showed significant correlation values only between virulence × biosynthesis potential and biomass production × biosynthesis potential, both with negative values, indicating an inverse correlation. Thus, AgNPs with entomopathogenic fungus extract can produce an innovative bioinsecticide product using a green production process.

Coal based carbon dots: Recent advances in synthesis, properties, and applications

AbstractCarbon dots are zero‐dimensional carbon nanomaterials with quantum confinement effects and edge effects, which have aroused great interests in many disciplines such as energy, chemistry, materials, and environmental applications. They can be prepared by chemical oxidation, electrochemical synthesis, hydrothermal preparation, arc discharge, microwave synthesis, template method, and many other methods. However, the raw materials' high cost, the complexity and environmental‐unfriendly fabrication process limit their large‐scale production and commercialization. Herein, we review the latest developments of coal‐based carbon dots about selecting coal‐derived energy resources (bituminous coal, anthracite, lignite, coal tar, coke, etc.) the developments of synthesis processes, surface modification, and doping of carbon dots. The coal‐based carbon dots exhibit the advantages of unique fluorescence, efficient catalysis, excellent water solubility, low toxicity, inexpensive, good biocompatibility, and other advantages, which hold the potentiality for a wide range of applications such as environmental pollutants sensing, catalyst preparation, chemical analysis, energy storage, and medical imaging technology. This review aims to provide a guidance of finding abundant and cost‐effective precursors, green, simple and sustainable production processes to prepare coal‐based carbon dots, and make further efforts to exploit the application of carbon dots in broader fields.

Volatile Photovoltaics: Green Industrialization, Sacrifice Zones, and the Political Ecology of Solar Energy in Germany

The development of solar energy has been depicted as a paradigmatic break in unsustainable global growth, largely because it is framed as an innovation with minimal carbon emissions. On the contrary, drawing on literatures from spatial justice and political ecology, including on authoritarian populism, this article analyzes the rise and fall of the solar industry and the associated failures of “green industrialization” in Bitterfeld, East Germany—an area that is characterized by political, economic, and social peripheralization, marginalization, and the rise of the far right. The development of solar energy, we argue, is merely the latest iteration of an industrial growth model that is rooted in a similar modernist mode of development. Based on original mixed methods field research in eastern Germany, it argues that many of the same inequalities that characterize fossil fuels and “gray” (de)industrialization—undemocratic and unsustainable industrial processes, the concentration of corporate power and profits, and externalized waste and pollution—are replicated by solar energy. What is distinct is the fact that such contemporary “green” manufacturing processes appear to negatively affect a wider and more dispersed range of spatial locations, also denying these locales the benefits of accumulation, production, and consumption. This unevenness reflects the reconfiguration of global supply chains over the past thirty years and the nature of green production processes that depend on a wider range of inputs that invariably produce localized sacrifice zones. We offer a spatial justice framework for solar energy, zooming in at the manufacturing stage, to explore the multiple sacrifice zones at the different stages of solar energy. Finally, we highlight the politics of resignation that is the product and foundation of capitalist realism that serves to dispossess communities around solar energy manufacturing sites in eastern Germany and might feed into the rise of the populist far right. The article contributes to the emerging critical literature that analyzes the dark side of renewable energy and, in doing so, reveals the social and ecological costs of energy transitions that continue to be underresearched yet deserve heightened attention.

Impacts of Environmental Policies on Global Green Trade

The objective of this study was to investigate the impact of environmental policies on bilateral green exports among developed and developing countries. The empirical analysis was based on the fixed-effects gravity model estimation with the PPML (Poisson pseudo-maximum likelihood) for bilateral green trade of world countries for 1990–2019. This study focused on two proxy environmental policy indicators: environment-related tax and energy intensity. The major findings were that, first, promotion of environment-related tax increases green exports among HIC (high-income countries) and, second, an increase in the green trade of a country depends on the energy intensity level of its trading partner countries in order to stabilize domestic demand and production. This result is shown to be significant and consistent within the trade between the same income groups. Thus, supporting the green growth strategy, empirical results suggest that LMY (low- and middle-income) countries have to promote environmental policies and green production processes to be competitive in the global market.

The Effect of Taguchi-Based Six Sigma Method on Variation Reduction in a Green Construction Material Production Process

Having sufficient knowledge about the role of statistics in engineering helps the managers to control the system appropriately, minimize the costs and increase the productivity. Studies indicate that different quality improvement techniques implemented in recent years did not work properly in some cases due to the unwise application of statistics. Taguchi-based Six Sigma method is a newly introduced method that has borrowed strengths of Taguchi and Six Sigma to provide a more applicable tool for industries, construction works and service centers. It is the optimal setting combined of two-quality improvement techniques, which can be significantly effective in reducing the variation and defects of a manufacturing or producing process. This study aimed to test and evaluate the effectiveness of this new quality improvement model in optimizing the production process of a green construction material. Results of implementing indicated a significant progress about 50% in process performance that verify the effectiveness of Taguchi-based Six Sigma method on variation reduction and quality improvement.

Techno-economic comparison of 100% renewable urea production processes

Urea is widely used in agriculture, industry, and food, while it is also a potential fuel. Large-scale urea production relies on fossil fuels, thus there is a strong need for green urea given the increasing penetration of renewable energy sources. A potential alternative is biomass-to-urea; however, it cannot fully convert the biomass carbon into urea. To achieve full carbon conversion, innovative integrated biomass- and power-to-urea processes are designed conceptually. The two green urea production processes are evaluated techno-economically and compared with state-of-the-art methane-to-urea. The results show that the methane-to-urea achieves a system efficiency of 58% (LHV), while biomass-to-urea only has 39% (LHV) with unconverted biomass carbon of up to 60%. The integrated power- and biomass-to-urea has outstanding heat integration performance which fixes all biomass carbon into urea, with an efficiency enhanced up to 53%. Due to the electricity demand, the levelized cost of the urea of integrated biomass- and power-to-urea is 15 – 38 and 58 – 87% points higher than those of the biomass-to-urea and methane-to-urea for the scale of 10 – 60 MWth urea production. The available annual hours and electricity price of renewable electricity have a significant impact on the levelized cost of the urea. When the available annual hours decrease from 7200 to 3600 with an electricity price of 73 $/MWh, the levelized cost of urea increases on average by 13% from 51 $/GJ with the plant capacity being 10 – 60 MWth urea. However, when electricity price is reduced from 73 $/MWh to 35 $/MWh with available annual hours of 3600, the levelized cost decreases on average by 15% from 59 $/GJ with the same plant capacity.

Electrochemical nitrogen reduction: recent progress and prospects.

Ammonia is one of the most useful chemicals for the fertilizer industry and is also promising as an important energy carrier for fuel cell application, and is currently mostly produced by the traditional Haber-Bosch process under high temperature and pressure conditions. This energy-intensive process is detrimental to the environment due to the dependence on fossil fuels and the emission of significant greenhouse gases (such as CO2). Ammonia production via the electrochemical nitrogen reduction reaction (ENRR) has been recognized as a green sustainable alternative to the Haber-Bosch process in recent years. Current ENRR research mainly focuses on the catalyst for ammonia selective production and the enhancement of faradaic efficiency at high current density; however, these have not been explored well due to the unavailability of highly efficient and cheap catalysts. Herein, this review provides information on the ENRR process along with (i) theoretical background, (ii) experimental methodology of the electrocatalytic process and (iii) computational screening of promising catalysts. The impact of active sites and defects on the activity, selectivity, and stability of the catalysts is deeply understood. Furthermore, we demonstrate the mechanistic understanding of the ENRR process on the surface of catalysts, with the aim of boosting the improvement of the ENRR activities. The ammonia detection methods are also summarized along with thorough discussion of control experiments. Finally, this review highlights prevailing problems in existing ENRR methods of ammonia production along with technical advancements proposed to address these issues and concludes with comments on opportunities and future directions of the ENRR process.

The impact of green productivity strategy on environmental sustainability through measurement of the management support: A field study in industry sector in Jordan

This study intends to distinguish the green productivity concepts, its strategy and the roadmap of its implementation throughout the adaption of green products, green production, and green innovation process dimensions. Further, it studies the impact of green productivity on environmental sustainability by identifying the mediating role of the management support to these green practices in the Jordanian factories. Methodology population of this study en-tails industry mining firms listed in the Amman Stock Exchange (ASE). A purposive sample was adapted in this study and consisted of specialized employees in terms of operating factories in general and in green production specifically. 100 questionnaires were precisely collected and analyzed via Smart Partial Least Square (PLS) statistics in order to analysis the mediation role. The study results point out a statistically significant impact of the independent variables, namely, the green productivity on environmental sustainability as a dependent variable in the existence of the mediating variable. Further, the results demonstrate the partial mediating effect of the dependent variable. However, there is no mediating effect of the independent to the mediator variable. Accordingly, the study recommends companies to concentrate on the roles played by the top management in the efforts towards green productivity adoption and strategic implementation in the Jordanian environment. The implementation of green productivity is considered at the early stages in Jordan. Thus, the value of the study lies in the search for issues that are eco-friendly practices.

Hydrogen role in the valorization of integrated steelworks process off-gases through methane and methanol syntheses

The valorization of integrated steelworks process off-gases as feedstock for synthesizing methane and methanol is in line with European Green Deal challenges. However, this target can be generally achieved only through process off-gases enrichment with hydrogen and use of cutting-edge syntheses reactors coupled to advanced control systems. These aspects are addressed in the RFCS project i3upgrade and the central role of hydrogen was evident from the first stages of the project. First stationary scenario analyses showed that the required hydrogen amount is significant and existing renewable hydrogen production technologies are not ready to satisfy the demand in an economic perspective. The poor availability of low-cost green hydrogen as one of the main barriers for producing methane and methanol from process off-gases is further highlighted in the application of an ad-hoc developed dispatch controller for managing hydrogen intensified syntheses in integrated steelworks. The dispatch controller considers both economic and environmental impacts in the cost function and, although significant environmental benefits are obtainable by exploiting process off-gases in the syntheses, the current hydrogen costs highly affect the dispatch controller decisions. This underlines the need for big scale green hydrogen production processes and dedicated green markets for hydrogen-intensive industries, which would ensure easy access to this fundamental gas paving the way for a C-lean and more sustainable steel production.

Phase behaviour and thermodynamic modelling of the ternary system (carbon dioxide + ε-caprolactone + chloroform)

The poly(ε-caprolactone) is an aliphatic polyester which has received a growing interest due its properties. Furthermore, the use of supercritical carbon dioxide is a major advance for the establishment of green polymer production processes. This advance is achieved by reducing the amount of toxic components and by the promoted separation of these components from the final product. The aim of this work was to study the high pressure phase behaviour for the ternary system involving carbon dioxide, ε-caprolactone, and chloroform, gathering crucial information to conduct polymerization reactions in supercritical medium. The experiments were executed at temperatures from (323 to 353) K, pressures from (4.68 to 21.85) MPa, and mass ratios of chloroform to ε-caprolactone of 0.5:1, 1:1 and 2:1. Phase transitions of vapour-liquid bubble point (VLE-BP), and dew point (VLE-DP) type were observed. Moreover, the experimental results were modelled using the Peng-Robinson (PR) equation of state with the Wong-Sandler (PR-WS).

(Invited) Integrated Green Engineering Process for Simultaneous Hydrogen Production and Fertigation

The constant utilization of hydrocarbon-based fuels such as petroleum, coal, and natural Gas has resulted in the detection of high concentration levels of sulfur containing gases in the atmosphere of many countries, including Qatar. Among those potential air pollutants, the rising concentrations of H2S and SO2 are of serious concern. In this work, sulfur-based seed solutions (SBSSs) such as sulfite or sulfide solutions are made by purging sulfur-containing gases released from industry into alkaline solutions. These SBSS solutions are simultaneously utilized towards the production of renewable hydrogen energy via a photoelectrochemical (PEC) process, and are used as draw solutions (DS) to produce diluted fertilizer water by a forward osmosis (FO) desalination process for agricultural irrigation purposes. The continuous bench scale of the integrated PEC-FDFO system was successfully demonstrated for simultaneous hydrogen production and dilution of SBSS DS. The experimental results showed that the reduction potential of SBSS DS in the PEC cell changes with variation of SBSS DS concentration and pH. This resulted in the continuous oxidation of sulfite into sulfate and led to more hydrogen production. Moreover, FDFO process exhibited high percentage of water recovery and DS dilution up to 80% and 68% at high SBSS DS concentration, respectively. In binary mixture of SBSS DS, increasing the concentration of ammonium sulfate (NH4)2SO4 led to high water flux to about 42%. The outcomes of this experimental study showed a successful practical continuous integrated system toward hydrogen production and fertigation.

Green Production as a Factor of Survival for Innovative Startups: Evidence from Italy

Many studies have analyzed empirically the determinants of survival for innovative startup companies using data about the characteristics of entrepreneurs and management or focusing on firm- and industry-specific variables. However, no attempts have been made so far to assess the role of the environmental sustainability of the production process. Based on data describing the characteristics of the Italian innovative startups in the period 2009–2018, this article studies the differences in survival between green and non-green companies. We show that, while controlling for other confounding factors, startups characterized by a green production process tend to survive longer than their counterparts. In particular, we estimate that a green innovative startup is more than twice as likely to survive than a non-green one. This evidence may support the idea that environmental sustainability can help economic development.

A novel green production process of citric acid on the pilot scale by directly recycling its extraction effluent

Citric acid effluent (CAE) treatment, the bottleneck of cleaner production of CA, has attracted intense attention. To solve pollution problems starting from the extraction process, a novel approach to directly recycle the effluent was proposed. First, a novel adaptive evolutionary method with morphology control was established to domesticate the CA-producing strain Aspergillus niger in the CAE. Based on this constructed strategy, an adaptive A. niger strain that could tolerate the effluent inhibition was obtained. Next, CAE was directly recycled without pretreatment to make mash for subsequent CA fermentation. Then, the whole CAE recycling-system including liquefaction, fermentation and extraction performance was assessed at laboratory and pilot scale. Here, the recycling process ran steadily on the pilot scale in 12 successive batches. The nutrients in the CAE were effectively utilized without inhibiting the CA fermentation. The proposed strategy for the CAE recycling was simple with low investment and operation cost, which made it appropriate for industrial-scale applications. It also provides inspiration for the effluent recycling in other submerged fermentations which are dominated by the filamentous fungi.

Tunable synthesis of imines and secondary-amines from tandem hydrogenation-coupling of aromatic nitro and aldehyde over NiCo5 bi-metallic catalyst

A green process for production of imine and secondary-amine with high selectivity is desirable and challenging. Here, selective production of these nitrogen-containing compounds in one-pot was effectively realized in a hydrogenation-coupling tandem reaction system catalyzed by bi-metallic NiCo catalyst. The investigation of Co/Ni composition vs activity showed a composition-dependence catalysis and the optimal bi-metallic catalyst was NiCo5 (Ni and Co molar ratio 1:5). Nitrobenzene (NB) could almost completely transform toward imine at 70 °C and secondary-amine at 90 °C, respectively. The adsorption configurations of reactant on catalyst surface were analyzed by DFT calculation to probe the reaction mechanism. And the reaction dynamics were also investigated deeply, suggesting that hydrogenation of NB should be promoted but hydrogenation of benzaldehyde (BA) need inhibiting. Additionally, the catalytic system under moderate reaction conditions could also be applied to a variety of substituted aromatic nitro and aldehyde compounds, showing high yields of corresponding imines.

Pilot-Scale Cyclohexanone Production through Phenol Hydrogenation over Pd/CN in a Continuous Ceramic Membrane Reactor

One-step phenol hydrogenation is a green process for cyclohexanone production. In this work, a pilot-scale cyclohexanone production by phenol hydrogenation over Pd/CN was successfully realized for the first time in a continuous ceramic membrane reactor, which was constructed by a three-stage continuous stirred tank reactor in series coupled with a side-stream membrane separation system. The continuous ceramic membrane reactor system could be steadily operated over 85 h with a cyclohexanone yield of ∼80%.

Enzymatic production of trans‐4‐hydroxy‐l‐proline by proline 4‐hydroxylase

Summary Trans‐4‐hydroxy‐l‐proline (Hyp) is a useful chiral building block for production of many nutritional supplements and pharmaceuticals. However, it is still challenging for industrial production of Hyp due to heavy environmental pollution and low production efficiency. To establish a green and efficient process for Hyp production, the proline 4‐hydroxylase (DsP4H) from Dactylosporangium sp. RH1 was overexpressed and functionally characterized in Escherichia coli BL21(DE3). The recombinant DsP4H with l‐proline as a substrate exhibited K m, k cat and k cat/K m values up to 0.80 mM, 0.52 s−1 and 0.65 s−1·mM−1 respectively. Furthermore, DsP4H showed the highest activity at 35°C and pH 6.5 towards l‐proline. The highest enzyme activity of 175.6 U mg−1 was achieved by optimizing culture parameters. Under the optimal transformation conditions in a 5‐l fermenter, Hyp titre, conversion rate and productivity were up to 99.9 g l−1, 99.9% and 2.77 g l−1 h−1 respectively. This strategy described here provides an efficient method for production of Hyp and thus has a great potential in industrial application.

Highly efficient catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol using UiO-66 without metal catalysts

In this paper, the as-prepared metal-organic frameworks material UiO-66 and other Zr-MOFs were directly used as catalytic transfer hydrogenation (CTH) catalysts to catalyze furfural (FF) to furfuryl alcohol (FAL) with 2-propanol (IPA) acted as both solvent and hydrogen donor. The results showed that the as-prepared UiO-66 had satisfactory catalytic activity and selectivity in yielding FAL (97 %) from the CTH of FF at 140 °C within 5 h. Moreover, the as-prepared UiO-66 exhibited relatively stable catalytic activity over five cycles and easy regeneration. Interestingly, UiO-66 was also applicable for the CTH of the other aldehydes such as 5-hydroxymethyfurfural, 5-methylfurfural, 4-methoxybenzaldehyde, and n-hexanal to the corresponding alcohols, affording high product yields up to 98 %. This work provides a green, simple and sustainable process for the catalytic production of FAL from biomass-based furfural, which has certain significance for the sustainable utilization of biomass.