Pembelajaran Ekonomi Pada Masa Pandemi Covid-19

This study seeks to find out how economics teachers carry out online learning during the COVID-19 pandemic. This research method uses a qualitative descriptive type, while data collected using interviews with several economics teachers in the Surakarta senior high schools using WhatsApp. The data were collected using purposive and snowball sampling. The results showed that the economics teachers prepared learning instruments at the beginning of the semester. However, the instruments were only the edited instruments from the previous semester. The economics teachers only adjusted them. The instruments made were only as administrative requirements for reports to the local education office. The instruments were not implemented during the learning process. Economics teachers used several media to connect with their students such as WhatsApp Group, Google Classroom, Google Meet, and YouTube. For learning assessment, they used Google Form, Quizzzz, Quipper School, Mentimeter, Kahoot, and the school's e-learning software.

Facile synthesis of graphene wool doped with oleylamine-capped silver nanoparticles (GW-αAgNPs) for water treatment applications

The facile synthesis of graphene wool doped with oleylamine-capped silver nanoparticles (GW-αAgNP) was achieved in this study. The effect of concentration, pH, temperature and natural organic matter (NOM) on the adsorption of a human carcinogen (benzo(a)pyrene, BaP) was evaluated using the doped graphene wool adsorbent. Furthermore, the antibacterial potential of GW-αAgNP against selected drug-resistant Gram-negative and Gram-positive bacteria strains was evaluated. Isotherm data revealed that adsorption of BaP by GW-αAgNP was best described by a multilayer adsorption mechanism predicted by Freundlich model with least ERRSQ < 0.79. The doping of graphene wool with hydrophobic AgNPs coated with functional moieties significantly increased the maximum adsorption capacity of GW-αAgNP over GW based on the qmax and qm predicted by Langmuir and Sips models. π-π interactions contributed to sorbent-sorbate interaction, due to the presence of delocalized electrons. GW-αAgNP-BaP interaction is a spontaneous exothermic process (negative $$\Delta H^\circ$$ Δ H ∘ and $$\Delta G)$$ Δ G ) , with better removal efficiency in the absence of natural organic matter (NOM). While GW is more feasible with higher maximum adsorption capacity (qm) at elevated temperatures, GW-αAgNP adsorption capacity and efficiency is best at ambient temperature, in the absence of natural organic matter (NOM), and preferable in terms of energy demands and process economics. GW-αAgNP significantly inhibited the growth of Gram-negative Pseudomonas aeruginosa and Gram-positive Bacillus subtilis strains, at 1000 mg/L dosage in preliminary tests, which provides the rationale for future evaluation of this hybrid material as a smart solution to chemical and microbiological water pollution.

Feasibility Study on Wastewater Treatment Using Chemically Enhanced Primary Treatment

A techno-economic analysis was performed to investigate wastewater treatment feasibility using chemically enhanced primary treatment (CEPT) compared to conventional primary treatment (PT). An experimental study was conducted to investigate the performance of CEPT at optimum conditions, and experimental results were used to feed the techno-economical study with required input data. The wastewater treatment was focused on reducing BOD5, COD, and TSS. The comparison between CEPT and PT was concerned with removal efficiency and process economics. CEPT process has shown better efficiency compared to PT process. The experimental work indicated that ferric chloride is the optimum coagulant agent since it is highly efficient and available at a low cost. The optimum coagulant experimental results showed that the turbidity removal efficiency was 82%, COD removal 84%, BOD removal 68.1%, and SS removal 85%. The techno-economic study was performed to investigate the feasibility of CEPT. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment. The techno-economic evaluation indicated that CEPT is a cost-effective and technically viable process for wastewater treatment as the operating cost can be reduced by 66% compared to PT.

Risk Analysis on PMMA Recycling Economics

Poly(methyl methacrylate) (PMMA) is a versatile polymer with a forecast market of 4 Mtons/y by 2025, and 6 USD billion by 2027. Each year, 10% of the produced cast sheets, extrusion sheets, or granules PMMA end up as post-production waste, accounting for approximately 30 000 tons/y in Europe only. To guide the future recycling efforts, we investigated the risks of depolymerization process economics for different PMMA scraps feedstock, capital expenditure (CAPEX), and regenerated MMA (r-MMA) prices via a Monte-Carlo simulation. An analysis of plastic recycling plants operating with similar technologies confirmed how a maximum 10 M USD plant (median cost) is what a company should aim for, based on our hypothesis. The capital investment and the r-MMA quality have the main impacts on the profitability. Depending on the pursued outcome, we identified three most suitable scenarios. Lower capital-intensive plants (Scenarios 4 and 8) provide the fastest payback time, but this generates a lower quality monomer, and therefore lower appeal on the long term. On 10 or 20 years of operation, companies should target the very best r-MMA quality, to achieve the highest net present value (Scenario 6). Product quality comes from the feedstock choice, depolymerization, and purification technologies. Counterintuitively, a plant processing low quality scraps available for free (Scenario 7), and therefore producing low purity r-MMA, has the highest probability of negative net present value after 10 years of operation, making it a high-risk scenario. Western countries (especially Europe), call for more and more pure r-MMA, hopefully comparable to the virgin material. With legislations on recycled products becoming more stringent, low quality product might not find a market in the future. To convince shareholders and government bodies, companies should demonstrate how funds and subsidies directly translate into higher quality products (more attractive to costumers), more economically viable, and with a wider market.

Removing the Bottleneck on Wind Power Potential to Create Liquid Fuels from Locally Available Biomass

In order to reduce global greenhouse gas emissions, renewable energy technologies such as wind power and solar photovoltaic power systems have recently become more widespread. However, Japan as a nation faces high reliance on imported fossil fuels for electricity generation despite having great potential for further renewable energy development. The focus of this study examines untapped geographical locations in Japan’s northern most prefecture, Hokkaido, that possess large wind power potential. The possibility of exploiting this potential for the purpose of producing green hydrogen is explored. In particular, its integration with a year-round conversion of Kraft lignin into bio-oil from nearby paper pulp mills through a near critical water depolymerization process is examined. The proposed bio-oil and aromatic chemical production, as well as the process’ economics are calculated based upon the total available Kraft lignin in Hokkaido, including the magnitude of wind power capacity that would be required for producing the necessary hydrogen for such a large-scale process. Green hydrogen integration with other processes in Japan and in other regions is also discussed. Finally, the potential benefits and challenges are outlined from an energy policy point-of-view.

Utilization of Barley Straw as Feedstock for the Production of Different Energy Vectors

During the bioethanol production process, vast amounts of residues are generated as process waste. To extract more value from lignocellulosic biomass and improve process economics, these residues should be used as feedstock in additional processes for the production of energy or fuels. In this paper, barley straw was used for bioethanol production and the residues were valorized using anaerobic digestion (AD) or used for the production of heat and power by combustion. A traditional three-step bioethanol production process was used, and the biomass residues obtained from different stages of the process were analyzed. Finally, mass and energy balances were calculated to quantify material flow and assess the different technological routes for biomass utilization. Up to 90 kg of ethanol could be produced from 1 t of biomass and additional biogas and energy generated from processing residues can increase the energy yield to over 220%. The results show that in terms of energy output, combustion was the preferable route for processing biomass residues. However, the production of biogas is also an attractive solution to increase revenue in the bioethanol production process.

Identification of the major fermentation inhibitors of recombinant 2G yeasts in diverse lignocellulose hydrolysates

Background Presence of inhibitory chemicals in lignocellulose hydrolysates is a major hurdle for production of second-generation bioethanol. Especially cheaper pre-treatment methods that ensure an economical viable production process generate high levels of these inhibitory chemicals. The effect of several of these inhibitors has been extensively studied with non-xylose-fermenting laboratory strains, in synthetic media, and usually as single inhibitors, or with inhibitor concentrations much higher than those found in lignocellulose hydrolysates. However, the relevance of individual inhibitors in inhibitor-rich lignocellulose hydrolysates has remained unclear. Results The relative importance for inhibition of ethanol fermentation by two industrial second-generation yeast strains in five lignocellulose hydrolysates, from bagasse, corn cobs and spruce, has now been investigated by spiking higher concentrations of each compound in a concentration range relevant for industrial hydrolysates. The strongest inhibition was observed with industrially relevant concentrations of furfural causing partial inhibition of both D-glucose and D-xylose consumption. Addition of 3 or 6 g/L furfural strongly reduced the ethanol titer obtained with strain MD4 in all hydrolysates evaluated, in a range of 34 to 51% and of 77 to 86%, respectively. This was followed by 5-hydroxymethylfurfural, acetic acid and formic acid, for which in general, industrially relevant concentrations caused partial inhibition of D-xylose fermentation. On the other hand, spiking with levulinic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid or vanillin caused little inhibition compared to unspiked hydrolysate. The further evolved MD4 strain generally showed superior performance compared to the previously developed strain GSE16-T18. Conclusion The results highlight the importance of individual inhibitor evaluation in a medium containing a genuine mix of inhibitors as well as the ethanol that is produced by the fermentation. They also highlight the potential of increasing yeast inhibitor tolerance for improving industrial process economics.