Clean Technologies and Environmental Policy

Circular economy: Is there anything new in this concept?

An environmentally sustainable manufacturing network model under an international ecosystem Abstract There is a growing consensus that the increase in greenhouse gases results in unfavorable changes to the Earth's climate and is responsible for global warming. Due to this ecological imbalance, governments are under growing pressure to enact strict legislation to control these emissions in their respective countries. Consumers also demand eco-friendly products and are moving toward firms that are socially and environmentally responsible. Therefore, industries are facing increased pressure to adopt sustainable production approaches. This paper demonstrates how a mixed integer linear program can be used to optimize the balance of overall cost and carbon emissions in the production, storage, and distribution of products in a regulatory environment that includes a cap and trade policy. The model is computationally tested for fifteen case instances of different sizes. The main contributions of the proposed model are (a) to link the emission parameters to various decision variables to support the decision making related to carbon costs and carbon emissions, (b) to address international trade issues by considering international parameters such as imports, exports, and government subsidies and perform a country-specific analysis for carbon emissions, and (c) to identify the extent to which the operational adjustment can be used as an alternative to the costly investment in carbon reduction technologies to reduce emissions. Graphical abstract Proposed MILP model framework

Air pollution prediction by using an artificial neural network model Abstract Air pollutants impact public health, socioeconomics, politics, agriculture, and the environment. The objective of this study was to evaluate the ability of an artificial neural network (ANN) algorithm to predict hourly criteria air pollutant concentrations and two air quality indices, air quality index (AQI) and air quality health index (AQHI), for Ahvaz, Iran, over one full year (August 2009–August 2010). Ahvaz is known to be one of the most polluted cities in the world, mainly owing to dust storms. The applied algorithm involved nine factors in the input stage (five meteorological parameters, pollutant concentrations 3 and 6 h in advance, time, and date), 30 neurons in the hidden phase, and finally one output in last level. When comparing performance between using 5% and 10% of data for validation and testing, the more reliable results were from using 5% of data for these two stages. For all six criteria pollutants examined (O3, NO2, PM10, PM2.5, SO2, and CO) across four sites, the correlation coefficient (R) and root-mean square error (RMSE) values when comparing predictions and measurements were 0.87 and 59.9, respectively. When comparing modeled and measured AQI and AQHI, R2 was significant for three sites through AQHI, while AQI was significant only at one site. This study demonstrates that ANN has applicability to cities such as Ahvaz to forecast air quality with the purpose of preventing health effects. We conclude that authorities of urban air quality, practitioners, and decision makers can apply ANN to estimate spatial–temporal profile of pollutants and air quality indices. Further research is recommended to compare the efficiency and potency of ANN with numerical, computational, and statistical models to enable managers to select an appropriate toolkit for better decision making in field of urban air quality. Graphical abstract

Tidal current energy potential assessment in the Avilés Port using a three-dimensional CFD method Abstract Tidal energy is considered as an energy resource of maximum interest in both technical and research fields due to its largely unexploited energy potential. The use of hydrokinetic microturbines is now an attractive option with reduced environmental impact. The first step to evaluate the feasibility of a hydrokinetic microturbines installation is to perform a study of the velocity field characteristics and therefore the energy potential available. Up to now, different numerical models, of one, two and three spatial dimensions have been applied to evaluate the tidal potential in large areas. Due to the high computational resources needed, they include simplifications, like avoiding a precise study of the velocity in the vertical dimension, resulting in incomplete estimations of the available kinetic energy. To complete these estimations, the research presented sets out a methodology to evaluate the current effects, velocity profiles and the energy potential derived from tide movements in an estuary or port by solving the full Navier–Stokes equations. It also considers the water–air interface in the numerical scheme. The methodology is based, firstly, on the definition of a three-dimensional geometrical model of the geographical area of study, and then, the complete model is meshed with finite volumes, where the full three-dimensional Unsteady Navier–Stokes equations are solved. The methodology was applied and validated with a three-dimensional water–air numerical model of the port of Avilés (Spain). In conclusion, water surface elevations, averaged speed cycles, velocity profiles as a function of depth and tidal power and energy data have been obtained without the usual simplifications, which will mean an evaluation more accurate when assessing the implementation of a power generation system. Graphic abstract

Renewable energy supply and carbon capture: capturing all the carbon dioxide at zero cost Abstract Climate change is likely to be (and is) more serious and likely to proceed much more rapidly than was previously thought. This article surveys and evaluates the technology of processing carbon dioxide and hydrogen into sustainable synthetic carbohydrate fuels and the related economics in relation to a particular route, the capture of carbon dioxide from the flue gas stream of gas burning power stations, provided the gaseous fuel is of biogenic origin. Biogenic methane is renewable and can, after combustion into carbon dioxide, via carbon capture be further processed into a range of carbohydrate fuels, or alternatively captured for final storage under carbon capture and store (CCS). It is proposed that the air intake of a power station be replaced by cooled flue gases consisting mainly of carbon dioxide, enriched with oxygen obtained by electrolysis of water. The co-produced hydrogen can then be processed further into more easily transportable and storable forms of fuel. This implies that a gas-fired power station is not so much a means of producing energy, but rather of producing pure carbon dioxide. The capture process as such is the same as the one which arises if the purpose is carbon capture and use or CCS in which case capture of CO2 from the combustion of methane from biogenic origin amounts to negative emissions. The indirect route of supplying and using energy via the production of carbohydrate fuels requires much more primary energy than the direct use of electricity does. For this reason, use of that indirect route is efficient for aviation, where the direct route of electric power is impractical. For shipping, there also is the alternative of the implicit transport of hydrogen as part of ammonia. It is assumed that the use of biogenic methane followed by processing of the captured carbon dioxide into synthetic hydrocarbon fuels is in combination with volcanic carbon hydroxide, sufficient to meet the demand for hydrocarbon fuels. Capture of carbon dioxide from biogenic methane can also be applied in the context of CCS.

Opportunities and challenges of natural gas development and utilization in China Abstract In the background that the China government robustly advocates low carbon and green energy, China has turned to focus on natural gas, both production and consumption of which are soaring high these days and the role of which is gradually prominent in energy sources. But it also faces many problems. With the rapid development of natural gas in China, it has gradually formed a system of natural gas industry chain. With the aims to help promote more healthy and sustainable development of natural gas industry in the future, it is very valuable to think deeply about the past development process. This paper reviews and analyzes China's natural gas resources, pipeline layout, and industry development status. Based on China's specific conditions and resource characteristics, it analyzes China's future natural gas development opportunities. Simultaneously, the analysis shows China's natural gas production will reach 236.5 billion cubic meters by 2030 and the proportion of natural gas in the primary energy structure will reach about 15% in 2030. But in terms of current natural gas production, the supply gap is very large. Moreover, the dependence on foreign natural gas imports has continued to increase in recent years. Thus, China should continue to improve its natural gas layout and utilization system, increase investment in domestic natural gas exploration and development, strengthen core technology research, and improve its relevant laws and regulations in order to better maintain the rapid development of natural gas. Graphical abstract

Photocatalytic decomposition of VOCs by AC–TiO 2 and EG–TiO 2 nanocomposites Abstract In this study, TiO2 nanoparticles (NPs)-based catalysts were prepared for the photocatalytic removal of toluene as a model VOC from air under UV light. Expanded graphite (EG) and activated carbon (AC) as two sustainable supports were employed for immobilization of TiO2 NPs by sol–gel technique. In this approach, substrates were added to TiO2 sol–gel and heated up to 60 °C followed by calcination process at 400 °C to afford, EG/TiO2 and AC/TiO2. The studies show that much better results ensued for AC–TiO2 because of higher surface area, good nanoparticle distribution, and lower pore width. The products were characterized by X-ray diffraction, scanning electron microscope, energy dispersive X-ray, as well as N2 adsorption/desorption. Graphical abstract

Understanding driving patterns of carbon emissions from the transport sector in China: evidence from an analysis of panel models Abstract China's transport industry has made rapid progress, which has led to a great amount of carbon emissions. However, it is still unclear how carbon emissions from the transport sector are punctuated by shifts in underlying factors. This paper aims to examine the process of China's carbon emissions from the transport sector as well as its major driving forces at the provincial level during the period of 2000 to 2015. We first estimate the carbon emissions from the transport sector at the provincial level based on the fuel and electricity consumption using a top-down method. We find that the carbon emission per capita is steadily increasing across the country, especially in the provinces of Chongqing and Inner Mongolia. However, the carbon emission intensity is decreasing in most provinces, except in Yunnan, Qinghai, Chongqing, Zhejiang, Heilongjiang, Jilin, Inner Mongolia, Henan and Anhui. We then quantify the effect of socioeconomic factors and their regional variations on carbon emissions using a panel model. The results show that the development of secondary industry is the most significant variable for carbon intensity at both the national and regional levels, while the effects of the other variables vary across regions. Among these factors, population density is the main factor of the increasing carbon emissions per capita from the transport sector for both the whole country and the western region, whereas the consumption level per capita of residents and the development of tertiary industry are the primary drivers of per capita carbon emissions for the eastern and central regions. Graphical abstract

Gasification of waste tires in a circulating fixed-bed reactor within the scope of waste to energy Abstract Thermochemical decomposition of waste tires was evaluated in order to produce solid and gaseous products within the aim of waste-to-energy concept. Pyrolysis and gasification occur in an "oxygen-starved" environment to "thermally degrade" organic wastes. Waste tires form a large volume of a landfill space that may lead to serious environmental issues and management complexities. Proximate and ultimate analyses reported that approximately 80% carbon in waste tire can be converted to different solid, liquid and gaseous forms for energy gain. Pyrolysis and gasification experiments were carried out in a circulating fixed-bed reactor with cyclone separator at varying temperatures between 600 and 800 °C. Dried air (0.05–0.5 L/min) and pure oxygen (0.01–0.015 L/min) were fed to gasification reactor as partially oxidizing agents. Pyrolysis gasification (PyroGasification—PG) was conducted to produce "syngas" which mainly contains carbon monoxide and hydrogen. One and 4 h of cooking time for the first-step pyrolysis were applied in a nitrogen-rich medium before gasification to enrich carbon amount in fuel. A syngas rich in H2, CH4 and CO with a high calorific value of almost 4900 kcal/m3 was obtained in gasification experiments performed with 0.05 L/min of dried air. Volumetric percentages of hydrogen and methane in syngas were around 35% and 40%, respectively. More than 65% mass and 80% volume reductions which are very important for waste management hierarchy and minimization were achieved by gasification of waste tires. Graphical abstract

Quaternary ammonium-functionalized rice straw hydrochar as efficient adsorbents for methyl orange removal from aqueous solution Abstract In this study, a series of quaternary ammonium-modified hydrochars was fabricated using rice straw as raw material. The physicochemical properties of the hydrochars before and after modification were characterized by FTIR, XPS and CHN element analysis, and an adsorption mechanism was proposed. Results showed the quaternary ammonium groups were successfully grafted onto the hydrochar. The modified hydrochar showed favorable capacity for methyl orange (MO) elimination from aqueous solution with a maximum value of 849 mg/g, which was an order of magnitude higher than that of pristine hydrochar (49 mg/g). Besides, the MO adsorption of all the adsorbents fitted well with the pseudo-second-order and Langmuir models, and the adsorption process was exothermal. Analysis of the adsorption mechanism showed that the decontamination process was primarily controlled by electrostatic attractions and ion exchange. Graphical abstract Utilization of rice straw to produce quaternary ammonium-functionalized hydrochars for the efficient removal of methyl orange.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com