Bo Zhang

High-speed rail has been operating in more than 25 countries (mainly in Asia, Europe and North America), and has become an important part of global economic development. However, the cleaning and maintenance of high-speed rail is a comprehensive task, which may easily cause environmental pollution. This study aims to analyze and improve the sustainability of the formulation and production process of a concentrated complex enzyme detergent used as the maintenance agent for high-speed trains via the life cycle assessment (LCA) method. The eFootprint software system with built-in China, European and Swiss Ecoinvent databases was used to establish the LCA model with the system boundary being from cradle to gate. The LCA model showed that the production of 1 kg of concentrated detergent generates the global warming potential of 2.53 kg CO₂ eq, and other environmental emissions including acidification potential of 0.01 kg SO₂ eq, eutrophication potential of 3.76E-03 kg PO₄³⁻eq, inhalable inorganic matter of 3.17E-03 kg PM2.5 eq, ozone depletion potential of 5.3E-06 kg CFC-11 eq, photochemical ozone formation potential of 3.44E-03 kg NMVOC eq, primary energy demand of 3.17 MJ, abiotic depletion potential of 4.97E-6 kg antimony eq, and water use of 0.84 kg. LCA results are not strongly dependent to the assumptions of the research, and the uncertainties of LCA results are between 8 and 16%, which is mainly due to the regional differences in technology sources, the year of technical data collection, and the representativeness of technology collection companies. Carbon footprint analysis showed that the production processes of enzyme stabilizer (glycerol) and surfactants contributed the most, while changes in power consumption during production and transportation distance of raw materials had limited effect on total carbon emissions. Therefore, the formulation of the concentrated complex enzymatic detergent was improved based on the LCA results. The new formulations with less enzyme stabilizer showed similar detergency to the original formulation. The new formulations could reduce carbon emissions by 5,500–9,200 tons per year and save between $4.4 and $7.4 million in annual production of 10,000 tons.

Biomass pyrolysis has become one of the promising technologies for fuel and fine chemical production. Cellulose constitutes the main body of plant biomass and may serve as a stereochemically pure reservoir to obtain active reagents for the synthesis of biologically active substances and structural units of valuable chemical substances. This study investigated the effect of cadmium (Cd) and tin (Sn) modified mesoporous sieve R-MCM-41 (R: Cd or Sn) on the pyrolysis of cellulose via thermogravimetric analysis (TGA) and pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS). The Si/R molar ratio of metal modified catalysts was between 100:1 and 10:1. TGA showed that Cd- and Sn-modified MCM-41 can effectively promote the degradation of cellulose, which was almost completely volatilized at 650 °C under the catalysis of Cd-MCM-41(50) and Sn-MCM-41(50). Py-GC/MS tests were carried out with different R-MCM-41s, reaction temperatures of 450 °C, 550 °C, and 650 °C, and the cellulose-to-catalyst ratios of 5:1, 1:1, and 1:5. The use of Sn-MCM-41 promoted the formation of glycolaldehyde and a limited amount of 1,2-cyclopentanedione and 5-methylfurfural. Cd-MCM-41 catalyzed pyrolysis produced higher levels of 5-hydroxymethylfurfural, 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC), 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2-hydroxy-3-methyl-2-cyclopenten-1-one, 1,2-cyclopentanedione, 3-methyl-2,4(3H,5H)-furandione, furfural, hydroxyacetone, glycolaldehyde, and butanone. When the pyrolysis temperature increased from 450 °C to 650 °C, the content of most small-molecule chemicals in the products increased by 1.8–4.1 times. When applying over-dosage of Cd-MCM-41(50) in the pyrolysis, anhydrosugars were completely degraded and dehydration/decarbonylation reactions were extensively enhanced, resulting in major products of butanone, furfural, and 5-methylfurfural. The possible reaction mechanism was proposed.

Because of the increase in concentrated animal feeding operations, there is a growing interest in sustainable manure management. In this study, hydrothermal liquefaction (HTL) of dairy manure enhanced by various chemicals (NH₃·H₂O, H₃PO₄, and glycerol) was proposed as a sustainable alternative for the dairy manure management. The applications of NH₃·H₂O and H₃PO₄ during HTL could significantly enhance the production of liquid chemicals. The addition of NH₃·H₂O or glycerol increased the amounts of non-polar toluene, xylene, and other benzene-contained compounds, while the use of H₃PO₄ produced high amounts of acids, pyridine, 3-methyl-pyridine, 2,6-dimethyl-pyrazine, 2-cyclopenten-1-ones, and phenols. The biochars produced via HTL showed a significant increase in the surface area/pore volume and relatively higher N, P, C, and other minerals, and may serve as a good soil amendment and nutrient source. The preliminary energy analyses showed that the energy consumption of this process might be reduced to 50% of the original energy content of the feedstock, and the energy payback period was about 3.5 years. Combining all advantages, HTL of dairy manure might increase the sustainability of the farming operation via producing energy products, fine chemicals, and biochars.

In this study, an innovative green biorefinery system was successfully developed to process the green biomass into multiple biofuels and bioproducts. In particular, fresh giant miscanthus was separated into a solid stream (press cake) and a liquid stream (press juice) using a screw press. The juice was used to cultivate microalga Chlorella vulgaris, which was further thermochemically converted via thermogravimetry analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis, resulting in an approximately 80% conversion. In addition, the solid cake of miscanthus was pretreated with dilute sulfuric acid and used as the feedstock for bioethanol production. The results showed that the miscanthus juice could be a highly nutritious source for microalgae that are a promising feedstock for biofuels. The highest cell density was observed in the 15% juice medium. Sugars released from the miscanthus cake were efficiently fermented to ethanol using Saccharomyces cerevisiae through a simultaneous saccharification and fermentation (SSF) process, with 88.4% of the theoretical yield.

The possibility of using the solid base as the pyrolysis catalyst to synthesize chemicals from duckweed (Lemna minor) was explored. Thermogravimetric analyses indicated that the conversion of duckweed in slow pyrolysis was approximately 60 wt%. Direct pyrolysis of duckweed could form various hydrocarbons and precursors for industrious products. When pyrolyzing this species with the solid base catalyst, new chemicals such as 3-methyl-butanal, cyclobutanol, 2-methyl-1H-pyrrole, ethylbenzene, 2-pyrrolidinone, and 4-ethyl-phenol were synthesized. The results indicated that the application of the solid base in pyrolysis mainly enhanced the alkyl substitution reactions and could direct complex pyrolysis reactions to preferred products.

A Comparison of Energy Consumption in Hydrothermal Liquefaction and Pyrolysis of Microalgae