A conceptual lignocellulosic ‘feed+fuel’ biorefinery and its application to the linked biofuel and cattle raising industries in Brazil

It has been argued by some that the substitution of biofuels for gasoline could increase greenhouse gas (GHG) emissions, rather than reduce them. The increase is attributed to the indirect land use change effects of planting new grain and corn crops around the world to replace those progressively being devoted to ethanol production. In this paper, indirect effects are minimised by allowing land to be used for both food and fuel, rather than for one or the other. We present a sugarcane ‘feed+fuel’ biorefinery, which produces bioethanol and yeast biomass, a source of single-cell protein (SCP), that can be used as a high-protein animal feed supplement. The yeast SCP can partially substitute for grass in the feed of cattle grazing on pasture and thereby potentially release land for increased sugarcane production, with minimal land use change effects. Applying the concept conservatively to the Brazilian ethanol and livestock industry our model demonstrates that it would be technically feasible to raise ethanol production threefold from the current level of 27 GL to over 92 GL. The extra ethanol would meet biofuel market mandates in the US without bringing any extra land into agricultural or pastoral use. The analysis demonstrates a viable way to increase biofuel and food production by linking two value chains as called for by industrial ecology studies.     

Fermentative hydrogen production - An alternative clean energy source

Hydrogen generation from wastewater is one of the promising approaches through biological route. So, exploitation of wastewater as substrate for hydrogen production with concurrent wastewater treatment is an attractive and effective way of tapping clean energy from renewable resources in a sustainable approach. In this direction, considerable interest is observed on various biological routes of hydrogen production using bio-photolysis, photo fermentation and heterotrophic dark fermentation process or by a combination of these processes. Therefore, in this communication, utilizing industrial wastewater as primary substrate for dark fermentation process is reviewed and different parametric aspects associated with this sustainable approach for better energy production is discussed. The industrial wastewaters that could be the source for bio hydrogen generation, such as rice slurry wastewater, food and domestic wastewaters, citric acid wastewater and paper mill wastewater, are also discussed in this article.     

Mo.nalis.a: a methodological approach to identify how to meet thermal industrial needs using already available geothermal resources

Mo.nalis.a is a conceptual model aimed at identifying the most suitable local geothermal sources to match the nearest industrial thermal needs. The methodological approach proposed is based on investigating industrial thermal processes and then identifying suitable geothermal solution plants that match these thermal requirements. The model was tested in Apulia (southern Italy) as a case study for assessing how the methodology could contribute to reducing the use of conventional energy resources for the industrial heat supply sector. The medium thermal needs in Apulia are always higher than 60 °C, and the main strategic industrial processes discussed into this work are “pasta and flour production” “wastewater treatment/sludge digestion” and “swimming pool management”. In order to match these industrial thermal demands, the most suitable proposed plant is the ground water heat pump system, limited to the first 100 m, the depth involved in the heat exchange through vertical probes of model. Finally, Mo.nalis.a identifies the Apulian areas with a possible development of these three activities using geothermal resource: the Foggia province, Murge and Salento sectors.     

Hydrogen production by immobilized Rhodopseudomonas palustris in packed or fluidized bed photobioreactor systems

The production of biohydrogen via photofermentation has been shown to have a low environmental impact and can often be integrated into wastewater treatment systems. However, currently, photofermentation has low production rates in comparison to industrial hydrogen production processes, and therefore requires improvement. One route for enhancing hydrogen productivity is the development of improved photobioreactor (PBR) systems. The aim of this study was to compare the hydrogen productivity of Rhodopseudomonas palustris under planktonic, and immobilized cell conditions, with the reactor operating either as a packed bed or a fluidized bed. The fluidized bed PBR achieved a maximum specific hydrogen production rate and substrate conversion efficiency of 15.74 ± 2.2 mL/g/h and 43% respectively, outperforming the conventional planktonic culture and the packed bed PBR. This work demonstrates a significant improvement in productivity over planktonic photofermentation, as well as demonstrating the use of immobilized cells under reactor conditions not usually associated with photosynthetic systems.     

Biohydrogen production from wastewater-based microalgae: Progresses and challenges

Microalgae originating from wastewater has been exhibiting particularly promising results in terms of biohydrogen production and wastewater treatment. This paper aims to review the factors affecting production, pretreatment techniques to improve synthesis, advanced technologies utilized for enhancing biohydrogen production, and techno-economic feasibility evaluation of the processes at a commercial scale. Microalgae possess metabolic components to synthesize biohydrogen using photobiological and fermentative processes but must undergo pretreatment for efficient biohydrogen production. The efficiency of these processes is influenced by factors such as the microalgae species, light intensity, cell density, pH, temperature, substrates, and the type of bioreactors. Moreover, many limitations, such as oxygen sensitivity, altered thylakoid constitution, low photon conversion efficiency, light capture disruption, and the evolution of harmful by-products hinder the sustainability of biohydrogen production processes. High operational and maintenance costs serve as the major bottleneck in the scaling up of the process as an industrial technology. Therefore, future research needs to be directed towards increasing optimization of the processes by reducing energy and resource demand, recycling metabolic wastes and process components, genetically engineered microalgae to adopt more efficient routes, and conducting pilot studies for commercialization.     

Recent advances in reuse of waste material as substrate to produce biohydrogen by purple non-sulfur (PNS) bacteria

Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and non-polluting nature. Biological hydrogen production processes, mostly mediated photosynthetic bacteria, are more favorable candidates for biological hydrogen production due to their high conversion efficiency and versatility in the substrates (including wastewater) they can utilize. The potential utilization of waste material is being investigated extensively with suitable bioprocess technologies for providing cheaper raw materials with simultaneous waste treatment and bioremediation. Thus, this review article summarizes the biohydrogen production metabolism of purple non-sulfur (PNS) bacteria and research works involving biohydrogen production using various wastes such as tofu wastewater, palm oil mill effluent, olive mill wastewater, brewery wastewater, etc. by photosynthetic PNS bacteria. Waste materials used, yields and rates are reviewed, together with a discussion of the economics and perspectives of biohydrogen production from waste materials.     

Waste-to-wealth approach in water economy: The case of beneficiation of mercury-contaminated water in hydrogen production

Heavy metals (Hg, Cd, Pb, etc.) are micro-pollutants and result in water contamination. Significant bio-concentration of heavy metal like Hg can lead to fatal disease such as Minamata. Given this context, heavy metal removal from wastewater is essential before discharge. The wastewater treatment process requires considerable amount of energy which is being met by the conventional carbon-based fuels. This contributes to the global carbon dioxide emission, and hence global warming. Therefore, if clean energy sourcing is enabled during the treatment of the wastewater; it would offer obvious advantages. If the energy production is ‘clean’ and achieved via the process itself, it would serve two outcomes: (a) meeting the energy demand for wastewater treatment, and (b) getting rid of the need for external ‘carbon-based’ energy. Recently a few research articles have reported simultaneous clean energy production from wastewater during its treatment. Thus, the energy demand of the wastewater treatment process can be potentially met with the clean energy produced during the process. In this review, we will discuss mercury-contaminated wastewater treatment with simultaneous hydrogen production. We will provide a brief overview of waste-to-wealth approaches currently prevailing in water economy, recent mercury removal processes, and discuss future possibilities of self-sustained Hg-contaminated wastewater treatment.     

Opportunities for heat exchanger applications in environmental systems

There is a worldwide interest in using pollution prevention methods to eliminate or lessen air, water, land and thermal pollution problems. Pollution prevention is designing processes that do not create pollution in the first place. Heat exchangers play an essential role in pollution prevention and in the reduction of environmental impact of industrial processes, by reducing energy consumption or recovering energy from processes in which they are used. They are used: (1) in pollution prevention or control systems that decrease volatile organic compounds (VOCs) and other air pollutant emissions; (2) in systems that decrease pollutants in wastewater discharges, the amount of the discharge and thermal pollution; and (3) used to recover energy in facilities that incinerate municipal solid waste and selected industrial hazardous wastes. Heat exchangers are also used in the heating, cooling and concentration of process streams that are part of many other pollution prevention or control related processes. In this paper, first presented is background information on the role of heat exchangers, their types, and a discussion of environment pollution problems. Next, the role of heat exchangers is outlined in the prevention and mitigation of the following pollution problems: air pollution from VOCs, sulphur oxides (SO_x), nitrogen oxides (NO_x); water pollution from industrial processes, thermal pollution, and land pollution resulting from municipal solid wastes or industrial hazardous wastes. Specific Research and Development needs for environmental heat exchangers are then summarized in the paper. It is hoped that this paper will challenge the heat transfer engineering community to further enhance the role of heat exchangers for pollution prevention and global sustainable development.     

山梨醇缩醛类成核剂生产中的废水回用技术

在介绍山梨醇缩醛成核剂合成原理和生产工艺的基础上,重点介绍了该类成核剂生产过程中废水的来源。研究表明,利用常规的絮凝剂及Feton试剂氧化法均无法使废水达到排放标准。在不考虑投资大、施工周期长的生化处理技术的前提下,进行了废水回用试验。小试和工业试验结果表明废水回用不会对产品熔点和白度造成影响。直接将废水回收再利用,每生产1t成核剂,可减少外排污水7t。     

炼油厂酸性水罐恶臭气体的治理

酸性水罐恶臭气体是炼油厂重要的恶臭污染源之一,介绍了目前国内工业上已采用或即将工业化的几种治理方法,包括吸附法、吸收法和吸收串连吸附法,并对它们各自的工业应用效果进行了客观比较。     

Recent advances in constructed wetland‐microbial fuel cells for simultaneous bioelectricity production and wastewater treatment: A review

The coupling of constructed wetlands (CWs) to microbial fuel cells (MFCs) has turned out to be a source of renewable energy for the production of bioelectricity and for the simultaneous wastewater treatment. Both technologies have an aerobic zone in the air‐water interface and an anaerobic zone in the lower part, where the anode and the cathode are strategically placed. This hybridization is a promising bioelectrochemical technology that exerts a symbiosis between plant‐bacteria in the rhizosphere of an aquatic plant, converting solar energy into bioelectricity through the formation of root exudates as an endogenous substrate and a microbial activity. The difference between CW‐MFC and MFC conventional lies in the bioelectricity and substrate production in situ, where exogenous substrates are not required for example wastewater. However, CW‐MFC can take organic content present in wastewater, promoting the removal of some pollutants. Different areas that comprise the study of a CW‐MFC have been explored, including the structures and their operation. This review aims to provide concise information on the state of the art of CW‐MFC systems, where a summary on important aspects of the development of this technology, such as bioelectricity production, configurations, plant species, rhizodeposits, electrode materials, wastewater treatment, and future perspectives, is presented. This system is a promising technology, not only for the production of bioenergy but also to maintain a clean environment, since during its operation, no toxic byproducts were formed.     

An energy evaluation of coupling nutrient removal from wastewater with algal biomass production

Recently, several life cycle analyses of algal biodiesel from virtual production facilities have outlined the potential environmental benefits and energetic balance of the process. There are a wide range of assumptions that have been utilized for these calculations, including the addition of fertilizers and carbon dioxide to achieve high algal yields in open ponds. This paper presents an energy balance of microalgal production in open ponds coupled with nutrient removal from wastewater. Actual microalgal yields and nutrient removal rates were obtained from four pilot-scale reactors (2500 gallons each) fed with wastewater effluent from a conventional activated sludge process for 6 months, and the data was used to estimate an energy balance for treating the total average 12 million gallons per day processed by the wastewater treatment plant. Since one of the most energy-intensive steps is the dewatering of algal cultures, several thickening and dewatering processes were compared. This analysis also includes the energy offset from removing nutrients with algal reactors rather than the biological nutrient removal processes typically utilized in municipal wastewater treatment. The results show that biofuel production is energetically favorable for open pond reactors utilizing wastewater as a nutrient source, even without an energy credit for nutrient removal. The energy content of algal biomass was also considered as an alternate to lipid extraction and biodiesel production. Direct combustion of algal biomass may be a more viable energy source than biofuel production, especially when the lipid content of dry biomass (10% in this field experiment) is lower than the high values reported in lab-scale reactors (50–60%).     

Cathodic material effect on electron acceptance towards bioelectricity generation and wastewater treatment

Influence of cathode material on electron accepting conditions during the treatment of recalcitrant pharmaceutical wastewater (PWW) was comparatively evaluated at different organic loads (3, 6, 9 and 15 g/l) in three bioreactors. Two bio-electrochemical treatment systems employed with different electrode materials viz., BET-SS (graphite as anode and stainless steel (SS) as cathode) and BET-G (graphite as both anode and cathode) were evaluated for PWW degradation and bioelectricity generation in comparison to conventional anaerobic treatment (AnT). BET-G exhibited high bioelectrogenic activity than BET-SS, elucidating the impact of varied cathode material. High cathode potential necessary for effective reduction at cathode were observed with graphite-cathode than SS-cathode which are crucial for treatment and power generation. Ohmic losses ascribed to electrode material interference were relatively high in BET-SS in comparison to BET-G. Graphite-cathode exhibited high electron acceptance conditions leading to higher pollutant removal along with organic fraction degradation, bio-electrogenesis and inorganic salts removal, when compared to SS-cathode. Placement of electrode assembly while operating BET with different electrode materials is proved to be significant for treatment and bioelectricity production. Efficient electron accepting conditions and high cathode potential in BET-G proved graphite as promising cathode material over SS for the treatment of PWW.     

Integrated approach for textile industry wastewater for efficient hydrogen production and treatment through solar PV electrolysis

Combining solar PV based electrolysis process and textile dyeing industry wastewater for hydrogen production is considered feasible route for resource utilization. An updated experimental method, which integrates resource availability to assess the wastewater based hydrogen production with highlights of wastewater treatment, use of solar energy to reduce the high-grade electricity for electrolysis (voltage, electrode materials) efficiency of the process was employed. Results showed that maximum pollutant removal efficiency in terms of conductivity, total dissolved solids, total suspended solids, biological oxygen demand, chemical oxygen demand, hardness, total nitrogen and total phosphorus were obtained from ≅73% to ≅96% at 12 V with steel electrode for pollutant load. The maximum input voltage was found at 3 V for the best efficiency i.e. 49.6%, 67.8% and 57.1% with carbon, steel and platinum electrodes respectively. It was observed that with high voltage (12 V) of the electrolyte the rate of production of hydrogen was higher with carbon, steel and platinum electrodes. However, the increase in the efficiency of the production of hydrogen was not significant with high voltage, may be due to energy loss through heat during extra-over potential voltage to the electrodes. Hence, this integrated way provides a new insight for wastewater treatment and hydrogen energy production simultaneously.     

微藻生物膜去污技术应用研究进展

文章综述了微藻生物膜净化污水和生产生物燃料等方面的国内外最新成果,阐述了典型微藻去污生物膜系统的运行情况、综合效益、优缺点和推广价值,并对微藻生物膜去污技术存在的问题及关键技术进展及发展趋势进行了分析,就微藻生物膜去污技术的规模化及产业化应用提出了建议,以期为微藻生物膜去污技术的成熟和规模应用提供理论和实践支撑。     

丙烯腈及相关装置污染物减排的技术措施

介绍了丙烯腈及相关装置在污染物排放方面存在的问题,并讨论了污染物减排的技术措施。这些措施有采取催化反应法AOGC技术治理吸收塔尾气的超标排放问题;设立精制尾气回收系统;将废水罐区的尾气引入焚烧炉,使氰化物得到无害化处理;降低丙烯腈及相关装置的废水量;将三级八组旋风分离器改成PV—E型二级旋风分离器,减少催化剂废渣的产生。以上措施的实施,达到了丙烯腈及相关装置污染物减排的目的。     

Multi-objective self-adaptive algorithm for highly constrained problems: Novel method and applications

As a substantive input to resolve the industrial systems and challenging optimization problems, which are multi-objective in nature, the authors introduce an emerging systematic multi-objective optimization methodology for large-scale and highly-constrained industrial production systems. The methodology uses a simulation-based optimization framework built on a novel multi-objective evolutionary algorithm that exhibits several specific innovative features to maintain genetic diversity within the population of solutions and to drive the search towards the Pareto-optimal set/front. This novel algorithm was validated using standard test functions and the results demonstrate undoubtedly that the proposed algorithm computes accurately the Pareto-optimal set for optimization problems of at least two-objective functions. Next, the algorithm was applied on a base case cogeneration optimization problem with three-objective functions named the modified CGAM problem. The modified problem includes concentrations and tax rates of pollutant emissions (i.e. CO₂ and NO_x). The multi-objective optimization of such a problem consists of simultaneously maximizing the exergetic efficiency of the cogeneration plant, minimizing the total cost rate (including pollutant tax rate), and minimizing the specific rate of pollutant emissions. A fuel-to-air equivalence ratio ranging from 0.5 to 1.0, and pollutant tax rates of 0.15 $/kg CO₂, and 7.50 $/kg NO_x were used to compute the surfaces of the Pareto fronts. The results found for the modified CGAM problem clearly demonstrate the applicability of the proposed algorithm for optimization problems of more than two-objective functions with multiple constraints. The results strengthen the fact that there is no single optimal solution but rather a set of optimal solutions that present the best trade-off alternatives from which a decision-maker can select the appropriate final decision. Also, the study emphasizes the key role of both economic and environmental issues in the optimization problem of energy systems.     

Biotechnological applications of wood-rotting fungi: A review

Among the main categories of wood-rotting fungi, white rot and brown rot fungi and their enzymes are being increasingly used in a variety of biotechnological applications, some of which include wood and pulping, textile, bioenergy/biofuel and bioremediation (decolourization of synthetic dyes, wastewater treatment, detoxification/removal of toxic substances, including wood preservatives). The paper reviews various biotechnological applications of wood-rotting fungi and their key enzymes, laccase and peroxidases, and outlines future prospects where technological developments can lead to their more efficient and economic industrial uses and can create opportunities to expand applications. The information is presented under defined, interactive categories. Thoughts are presented on potential future technology development that can ensure economic production of specific enzymes and their targeted industrial applications.     

A／O工艺处理炼油厂海水和淡水混合废水的研究

对大连石化公司污水场处理海淡混合污水的工艺条件、运行方式、控制方法进行分析和研究，总结出操作规律。结果表明，使用A／O生物法处理该性质的污水是可行的；在启动运行上，污泥培养驯化方式上与常规工业污水驯化相同但控制条件不同；在工艺条件上，SWI低于100mL／g，但污泥增长较为缓慢；在控制条件上，要求原水的含盐量必须稳定在±5％的变化幅度以内；在处理效果上，污染物可以达到90％以上的去除率，满足国标一级排放标准的要求。     

Use of thermodynamic functions for expressing some relevant aspects of sustainability

Sustainability is a key concept for our future and the role of thermodynamics in its assessment is fundamental. The use of energy and matter must be considered not only from a microscopic viewpoint (the use of a single fuel or material, or the presence of a single pollutant) but also by means of holistic approaches able to synthesize all the characteristics of a single process. Exergy is a suitable function for this purpose. The exergy concept can also be applied to natural systems and to systems at the interface between natural and artificial ones. In this context also emergy can express very helpful indications. Four different efficiency indices are here examined to better understand different aspects of the sustainability of processes and systems. An application to two similar agricultural systems (wine production in Italy) shows how these indices work in real case studies. Copyright © 2005 John Wiley & Sons, Ltd.