Whether biorefinery is a promising way to support waste source separation? From the life cycle perspective

Since the implementation of the waste separation policy, the disposal of source-separated food waste (FW) has been more strictly required. Traditional source-separated FW treatment technologies, such as anaerobic digestion (AD) and aerobic composting (AC), suffer from low resource utilization efficiency and poor economic benefits. It is one of the main limiting factors for the promotion of waste separation. Life cycle assessment (LCA) was conducted for five municipal solid waste (MSW) treatment technologies, compared their environmental impacts, and analyzed the impact of waste separation ratios to determine whether biorefinery is a promising way to support waste source separation. The results showed that black soldier fly (BSF) treatment had the lowest net global warming potential (GWP) of all technologies, reduced by 40.8 % relative to the non-source-separated treatment. Ethanol production had the second-lowest net environmental impact potential because bioethanol replaces fossil fuel to avoid the emission of pollutants from its combustion. When two biorefinery technologies with excellent efficiency to avoid environmental impact are used to treat source-separated FW, the increase in the percentage of waste separation will help reduce the environmental impact of MSW treatment. The application of biorefinery technologies is considered a viable option for source-separated FW treatment. AC should not be widely promoted because it showed the worst net environmental benefits, and waste separation will elevate the environmental impact of its treatment process.

One-Step Conversion of n-Butanol to Aromatics-free Gasoline over the HZSM-5 Catalyst: Effect of Pressure, Catalyst Deactivation, and Fuel Properties as a Gasoline

Sustainable production of gasoline-range hydrocarbon fuels from biomass is critical in evading the upgradation of combustion engine infrastructures. The present work focuses on the selective transformation of n-butanol to gasoline-range hydrocarbons free from aromatics in a single step. Conversion of n-butanol was carried out in a down-flow fixed-bed reactor with the capability to operate at high pressures using the HZSM-5 catalyst. The selective transformation of n-butanol was carried out for a wide range of temperatures (523-563 K), pressures (1-40 bar), and weight hourly space velocities (0.75-14.96 h-1) to obtain the optimum operating conditions for the maximum yields of gasoline range (C5-C12) hydrocarbons. A C5-C12 hydrocarbons selectivity of ∼80% was achieved, with ∼11% and 9% selectivity to C3-C4 paraffin and C3-C4 olefins, respectively, under optimum operating conditions of 543 K, 0.75 h-1, and 20 bar. The hydrocarbon (C5-C12) product mixture was free from aromatics and primarily olefinic in nature. The distribution of these C5-C12 hydrocarbons depends strongly on the reaction pressure, temperature, and WHSV. These olefins were further hydrogenated to paraffins using a Ni/SiO2 catalyst. The fuel properties and distillation characteristics of virgin and hydrogenated hydrocarbons were evaluated and compared with those of gasoline to understand their suitability as a transportation fuel in an unmodified combustion engine. The present work further delineates the catalyst stability study for a long time-on-stream (TOS) and extensive characterization of spent catalysts to understand the nature of catalyst deactivation.

Life cycle assessment of calcium oxide pretreatment of corn stover with carbon dioxide neutralization for ethanol production

This work used life-cycle assessment (LCA) to determine the environmental and human health impacts of four ethanol production scenarios (S1: CaO pretreatment + H₂SO₄ neutralization + C6 yeast fermentation; S2: CaO pretreatment + CO₂ neutralization + C6 yeast fermentation; S3: CaO pretreatment + H₂SO₄ neutralization + C6/C5 yeast fermentation; and S4: CaO pretreatment + CO₂ neutralization + C6/C5 yeast fermentation), with the functional unit being 1 kg of 95 % ethanol. TheLCA results showed that the total ozone depletion, global warming potential, smog, acidification, eutrophication, and ecotoxicity values were comparable when CO₂ or H₂SO₄ were used to adjust the pH of CaO-pretreated slurry. However, using CO₂ for neutralization and C6/C5 yeast for fermentation demonstrated significant benefits in terms of carcinogenicity, non-carcinogenicity, respiratory effect, ecotoxicity, and fossil fuel depletion. The findings indicate that the choice of chemicals and strains plays a key role in determining environmental and human health impacts.

Theoretical Studies on the Reaction Kinetic of 2-Acetylfuran with Hydroxyl Radicals

With the development of synthetic methods, 2-acetylfuran (AF2) has become a potential biomass fuel. The potential energy surfaces of AF2 and OH including OH-addition reactions and H-abstraction reactions were constructed by theoretical calculations at the CCSDT/CBS/M06-2x/cc-pVTZ level. The temperature- and pressure-dependent rate constants of the relevant reaction pathways were solved based on transition state theory and Rice-Ramsperger-Kassel-Marcus theory, as well as Eckart tunneling effect correction. The results showed that the H-abstraction reaction on CH₃ on the branched chain and the OH-addition reaction at the C (2) and C (5) sites on the furan ring were the main reaction channels in the reaction system. At low temperatures, the AF2 and OH-addition reactions dominate, and the percentage decreases gradually to zero with increasing temperature, and at high temperatures, the H-abstraction reactions on the branched chains become the most dominant reaction channel. The rate coefficients calculated in the current work improve the combustion mechanism of AF2 and provide theoretical guidance for the practical application of AF2.

Using Alternative Sources of Energy for Decarbonization: A Piece of Cake, but How to Cook This Cake?

Few analytical or research works claim that the negative impact of improper use of ASEs may be comparable with that of hydrocarbons and sometimes even greater. It has become a common view that "green" energy (ASE) is clean, safe and environmentally friendly (eco-friendly) in contrast with "black" energy (hydrocarbons). We analyzed 144 works on systemic and/or comparative research of the modern and prospective ASE: biofuels, hydrogen, hydropower, nuclear power, wind power, solar power, geothermal power, oceanic thermal power, tidal power, wind wave power and nuclear fusion power. We performed our analysis within the Spaceship Earth paradigm. We conclude that there is no perfect ASE that is always eco-friendly. All ASEs may be dangerous to the planet considered as a closed and isolated unit ("spaceship") if they are used in an inconsistent manner. This is not in the least a reason to deny them as prospective sources of energy. Using all ASEs in different proportions in various regions of the planet, where their harm to the planet and humanity can be minimized and, on the contrary, their efficiency maximized, would give humanity the opportunity to decarbonize the Earth, and make the energy transition in the most effective way.

Sustainable conversion of biomass to rationally designed lithium-ion battery graphite

The carbon net negative conversion of bio-char, the low value byproduct of pyrolysis bio-oil production from biomass, to high value, very high purity, highly crystalline flake graphite agglomerates with rationally designed shape and size tailored for lithium-ion battery energy storage material is reported. The process is highly efficient, 0.41 g/Wh; the energy content of its co-product of the process, bio-oil, exceeds that needed to power the process. It is shown that the shape of the starting material is retained during the transformation, allowing the ultimate morphology of the graphite agglomerates to be engineered from relatively malleable biomass. In contrast to commercial graphite production, the process can be performed at small scale with low equipment costs, enabling individual research laboratories to produce Li-ion grade graphite with customizable shape, size and porosity for Si/graphite composite and other graphite involved anodes. The mechanism of the graphitization of bio-char, a “non-graphitizable” carbon, is explored, suggesting the molten metal catalyst is absorbed into the pore structure, transported through and transforming the largely immobile biochar. Finally, the transformation of biomass to rationally designed graphite morphologies with Li-ion anode performance that closely mimic commercial shaped graphite is demonstrated.

Acid-based lignocellulosic biomass biorefinery for bioenergy production: Advantages, application constraints, and perspectives

The production of chemicals and fuels from renewable biomass with the primary aim of reducing carbon footprints has recently become one of the central points of interest. The use of lignocellulosic biomass for energy production is believed to meet the main criteria of maximizing the available global energy source and minimizing pollutant emissions. However, before usage in bioenergy production, lignocellulosic biomass needs to undergo several processes, among which biomass pretreatment plays an important role in the yield, productivity, and quality of the products. Acid-based pretreatment, one of the existing methods applied for lignocellulosic biomass pretreatment, has several advantages, such as short operating time and high efficiency. A thorough analysis of the characteristics of acid-based biomass pretreatment is presented in this review. The environmental concerns and future challenges involved in using acid pretreatment methods are discussed in detail to achieve clean and sustainable bioenergy production. The application of acid to biomass pretreatment is considered an effective process for biorefineries that aim to optimize the production of desired products while minimizing the by-products.

Anaerobic digestate water for Chlorella pyrenoidosa cultivation and employed as co-substrate with cow dung and chicken manure for methane and hydrogen production: A closed loop approach

In rural India, unpleasant atmosphere, anthropogenic gas emission, air and soil pollution are caused due to disposal of livestock's wastes (cow dung and chicken waste) in open environment. This study provides zero emission concept for waste disposal and value addition of these wastes for renewable green energy production. In this study, biogas production was carried out with varying proportion of cow dung to chicken waste (1:0, 0:1, 1:1, 2:1, 1:2, 3:1 and 1:3) for duration of 40 days. Chlorella pyrenoidosa was cultivated from digestate water and used as co-substrate in digester in varying proportions (2:1:1, 2:1:2 and 2:1:3) to study its role on biogas distribution. The effect of pH, feedstock ratio, time and C/N ratio for biogas production were evaluated. The maximum methane and hydrogen yield was 68% (30th day) and 29% (10th day) for 2:1:2 ratio respectively. The slurry possessed nitrogen (1.7%), phosphate (0.8%) and potassium (0.4%) respectively.

Green pathway to a new fuel extender: continuous flow catalytic synthesis of butanol/butyl butyrate mixtures

The preparation of a butanol/butyl butyrate mixture was performed in one-step under continuous flow conditions with a CuO/ZrO₂ catalyst. The catalytic system allows one to directly obtain up to 40–42% of butyl butyrate starting from butanol via a dehydrogenative coupling reaction without using solvent or additives. The obtained mixture was tested in a direct injection spark ignition engine as a blend of 70%_vol gasoline and 30%_vol butanol/butyl butyrate mixture. One of the main goals was to evaluate overall performance and whether knock tendency increased compared to the reference condition that featured gasoline only fueling. Exhaust gas pollutants were evaluated as well, so as to give a more complete picture of environmental impact effects. Overall engine performance and emissions were found to be comparable to those obtained for the reference case, with negligible increase in knocking characteristics.

The preparation of a butanol/butyl butyrate mixture was performed in one-step under continuous flow conditions with a CuO/ZrO₂ catalyst.

Isolation and Characterization of Bacterial Cellulase Producers for Biomass Deconstruction: A Microbiology Laboratory Course

The conversion of biomass to biofuels presents a solution to one of the largest global challenges of our era, climate change. A critical part of this pipeline is the process of breaking down cellulosic sugars from plant matter to be used by microbes containing biosynthetic pathways that produce biofuels or bioproducts. In this inquiry-based course, students complete a research project that isolates cellulase-producing bacteria from samples collected from the environment. After obtaining isolates, the students characterize the production of cellulases. Students then amplify and sequence the 16S rRNA genes of confirmed cellulase producers and use bioinformatic methods to identify the bacterial isolates. Throughout the course, students learn about the process of generating biofuels and bioproducts through the deconstruction of cellulosic biomass to form monosaccharides from the biopolymers in plant matter. The program relies heavily on active learning and enables students to connect microbiology with issues of sustainability. In addition, it provides exposure to basic microbiology, molecular biology, and biotechnology laboratory techniques and concepts. The described activity was initially developed for the Introductory College Level Experience in Microbiology (iCLEM) program, a research-based immersive laboratory course at the US Department of Energy Joint BioEnergy Institute. Originally designed as an accelerated program for high-potential, low-income, high school students (11th-12th grade), this curriculum could also be implemented for undergraduate coursework in a research-intensive laboratory course at a two- or four-year college or university.

Evaluating the Impacts of ACP Management on the Energy Performance of Hydrothermal Liquefaction via Nutrient Recovery

Hydrothermal liquefaction (HTL) is of interest in producing liquid fuels from organic waste, but the process also creates appreciable quantities of aqueous co-product (ACP) containing high concentrations of regulated wastewater pollutants (e.g., organic carbon, nitrogen (N), and phosphorus (P)). Previous literature has not emphasized characterization, management, or possible valorization of ACP wastewaters. This study aims to evaluate one possible approach to ACP management via recovery of valuable scarce materials. Equilibrium modeling was performed to estimate theoretical yields of struvite (MgNH4PO4·6H2O) from ACP samples arising from HTL processing of selected waste feedstocks. Experimental analyses were conducted to evaluate the accuracy of theoretical yield estimates. Adjusted yields were then incorporated into a life-cycle energy modeling framework to compute energy return on investment (EROI) for the struvite precipitation process as part of the overall HTL life-cycle. Observed struvite yields and residual P concentrations were consistent with theoretical modeling results; however, residual N concentrations were lower than model estimates because of the volatilization of ammonia gas. EROI calculations reveal that struvite recovery is a net-energy producing process, but that this benefit offers little to no improvement in EROI performance for the overall HTL life-cycle. In contrast, corresponding economic analysis suggests that struvite precipitation may be economically appealing.

Pretreatment of wheat straw using basic ethanolamine-based deep eutectic solvents for improving enzymatic hydrolysis

A series of ethanolamine based deep eutectic solvents (DESs), which have strong basicity, were firstly applied in wheat straw pretreatment. Typically, choline chloride: monoethanolamine (C:M) as the best solvent among these DESs can remove 71.4% lignin and reserve 93.7% cellulose (70 °C, L/S mass ratio of 20:1, 9 h), and improve the enzymatic hydrolysis of residue, i.e., 89.8% cellulose and 62.0% xylan conversion. The pretreatment capacity of C:M is comparable to other solvents while C:M has several advantages, e.g., lower cost with cheap materials and simpler preparation process, mild conditions and lower polysaccharide loss. The XRD, SEM and FT-IR results verified that the polysaccharide conversion and sugars yield were enhanced by the removal of lignin in the pretreatment process. The basic ethanolamine based DESs are promising solvents for industrial application of wheat straw pretreatment.

Upgradation of chemical, fuel, thermal, and structural properties of rice husk through microwave-assisted hydrothermal carbonization

The process parameters of microwave hydrothermal carbonization (MHTC) have significant effect on yield of hydrochar. This study discusses the effect of process parameters on hydrochar yield produced from MHTC of rice husk. Results revealed that, over the ranges tested, a lower temperature, lower reaction time, lower biomass to water ratio, and higher particle size produce more hydrochar. Maximum hydrochar yield of 62.8% was obtained at 1000 W, 220 °C, and 5 min. The higher heating value (HHV) was improved significantly from 6.80 MJ/kg of rice husk to 16.10 MJ/kg of hydrochar. Elemental analysis results showed that the carbon content increased and oxygen content decreased in hydrochar from 25.9 to 47.2% and 68.5 to 47.0%, respectively, improving the energy and combustion properties. SEM analysis exhibited modification in structure of rice husk and improvement in porosity after MHTC, which was further confirmed from BET surface analysis. The BET surface area increased from 25.0656 m²/g (rice husk) to 92.6832 m²/g (hydrochar). Thermal stability of hydrochar was improved from 340 °C for rice husk to 370 °C for hydrochar.

Cholinium amino acids-glycerol mixtures: New class of solvents for pretreating wheat straw to facilitate enzymatic hydrolysis

New solvents for pretreating wheat straw, mixtures of cholinium amino acids ionic liquids ([Ch][AA] ILs) and glycerol, were developed. As a typical result, 50% cholinium alanine-glycerol is capable of removing 67.6% lignin while reserving 95.1% cellulose (90°C, L/S mass ratio of 20:1, 6h) and the conversions of cellulose and xylan are 89.7% and 70.9%, respectively, which is comparable to the pretreatment capability of other solvents, while [Ch][AA]-glycerol mixtures have desirable advantages, e.g., biocompatibility, lower cost with adding glycerol than pure IL, much lower pretreatment temperature (typically <100°C) than that by glycerol (typically >200°C). Lignin removal and polysaccharide conversion are dependent on [Ch][AA] content and pH of pretreatment solvents. [Ch][AA] not only remove lignin in wheat straw effectively but also swell cellulose while not remarkably dissolve cellulose with high cellulose reservation, favoring the enzymatic hydrolysis. Such mixtures of ILs and co-solvents are potential solvents for pretreating biomass.

Production of furfural from xylose and corn stover catalyzed by a novel porous carbon solid acid in γ-valerolactone

An efficient catalytic system using S-RFC as catalyst was developed to produce furfural from xylose and corn stover in GVL.

Integrated in situ transesterification for improved biodiesel production from oleaginous yeast: a value proposition for possible industrial implication

An integrated in situ transesterification process was developed in this study for energy and cost-efficient biodiesel production from oleaginous yeast biomass.

Promotion effects of plasma treatment on silica supports and catalyst precursors for cobalt Fischer–Tropsch catalysts

Glow discharge plasma would modify the surface hydrophilicity of support; the plasma treated catalysts showed much higher FTS activity.

Extractive denitrogenation of fuel oils using ionic liquids: a review

Extractive denitrogenation (EDN) of fuel oils using ILs is reviewed. EDN using ILs is a promising technology for the elimination of N-compounds from fuel oils.

Co-processing of bio-oil from de-oiled Jatropha curcas seed cake with refinery gas–oil over sulfided CoMoP/Al2O3 catalyst

Schematic representation of Co-processing of bio-oil from de-oiled Jatropha curcas seed cake with refinery gas–oil over sulfided CoMoP/Al₂O₃ catalyst.

Green oxidation of bio-lactic acid with H2O2 into tartronic acid under UV irradiation

Lactic acid was photochemically converted into tartronic acid via green oxidation by using H₂O₂.

Thermochemical processing of fuels involving the use of molecular oxygen

Properly introducing O₂ into the thermochemical processing (TCP) of fuel is not simply just burning fuel. It can improve thermal efficiency, simplify TCP operation, reduce CO₂ emission, help to utilize unminable energy resources, etc.