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Ammonia increases buffer capacity of methanogenic medium in mesophilic anaerobic reactor thus increasing the stability of anaerobic digestion process. Optimal ammonia concentration ensures sufficient buffer capacity while not inhibiting the process. It was found out in this paper that this optimum depends on the quality of anaerobic sludge under investigation. The optimal concentrations for methanogens were 2.1, 2.6 and 3.1 g/L of ammonia nitrogen in dependence on inoculum origin. High ammonia nitrogen concentration (4.0 g/L) inhibited methane production, while low ammonia nitrogen concentration (0.5 g/L) caused low methane yield, loss of biomass (as VSS) and loss of the aceticlastic methanogenic activity. It was found out that negative effect of low ammonia nitrogen concentration on biomass is caused not only by low buffer capacity but also by insufficiency of nitrogen as nutrient. It was also found out that anaerobic sludge with higher ammonia nitrogen concentration (4.2 g/L) tolerates even concentration of volatile fatty acids (160 mmol/L) which causes inhibition of the process with low ammonia nitrogen concentration (0.2 g/L).

This paper describes anaerobic thermophilic sludge digestion (55 °C) in a continuously stirred tank reactor (CSTR) on a pilot-plant scale (150 L). The experimental protocol was defined to examine the effect of the increase in the organic loading rate on the efficiency of the digester and to report on its steady-state performance. The reactor was subjected to a programme of steady-state operation over a range of solids retention times (SRTs) of 75, 40, 27, 20 and 15 days and organic loading rates (OLR) in the range 0.4–2.2 kg VS/(m3 day). The digester was fed with raw sludge (containing approximately 35 kg/m3 volatile solids (VS)) once daily during the 75-day SRT period, twice daily during the 40-day SRT period and three times a day during the 27-, 20- and 15-day SRT periods. The reactor was initially operated with an organic loading rate of 0.4 kg VS/(m3 day) and an SRT of 75 days. The volatile solids removal efficiency in the reactor was found to be 73%, while the volumetric methane production rate produced in the digester reached 0.02 m3/(m3 day). Over a 338-day operating period, an OLR of 2.2 kg VS/(m3 day) was achieved with 49.1% VS removal efficiency in the pilot sludge digester, at which time the volumetric methane production rate content of biogas produced in the digester reached 0.4 m3/(m3 day). The chemical oxygen demand (COD) mass balance obtained indicated that COD used for methane generation increased when the SRT was decreased or when the influent organic loading rate was increased. This implies that the amount of COD used in the anabolism route decreased with SRT due the microbial population becoming adapted to new operational conditions and more COD being used to generate methane.

One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80°C and 90°C), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.

Abstract Biofuels are considered as an alternative to partially replace fossil fuels and mitigate climate change effects. A life cycle assessment of second generation ethanol, derived from banana agricultural wastes, was developed to assess its environmental sustainability and demonstrate its capacity of reducing greenhouse gas emissions. The methodological approach was conducted in a Well-to-Wheel perspective, using as functional unit 1 MJ of energy released in the combustion of bioethanol in a passenger car from different bioethanol blends. Primary and secondary information sources were used for the assessment; mass balance and ethanol yield data came from laboratory experimentation. The environmental assessment was carried out using SimaPro 8.0.4.30 with the ReCiPe midpoint (H) impact assessment methodology. The quantified impact categories were climate change (CC), terrestrial acidification (TA), freshwater eutrophication (FE), photochemical oxidant formation (PO), particulate matter formation (PM), and fossil depletion (FD). In addition, net energy value and energy ratio (ER) were analyzed to ensure a positive energy balance. Compared to using pure gasoline, blended gasoline reduced CC, PO, PM, and FD impacts, but increased FE and TA impacts. The obtained energy balance was positive, with an ER of 2.68 MJ/MJ. Wastewater treatment is the process that presented the greatest energy consumption. Since Ecuador is the world's largest exporter of bananas, and a great amount of agricultural waste is available, a case study in this country was analyzed. This case study indicated that Ecuador could use banana residue for ethanol production, considering its positive and negative impacts. In conclusion, second generation ethanol derived from banana agricultural waste has potential to reduce greenhouse gas emissions and fossil depletion and has a positive energy balance.

AbstractFly ash is currently a problem in different companies, mainly in thermoelectric plants, which must follow a production and consumption model that involves reusing, renewing, and recycling, thus contributing to the circular economy. This work aims to evaluate the reactivity and compressive strength of different types of ashes in concrete monoliths. For this purpose, sugarcane bagasse (SCBA), bituminous coal (BC), and untreated hazardous waste (RUD) were evaluated as replacements for cement. Monoliths and mortars have been manufactured in different mixtures, taken to a curing room, and their compressive strength and reactivity have been determined at different times (up to 28 days for the monoliths and up to 90 for the mortars), mainly in order to check the formation of calcium silicate hydrate (CSH) gels. In the monolith tests, the best performances have been with SCBA and BC, which have been used for the manufacture of the mortars. On day 56, the behavior of the replacement of 30% fly ash (15% BC:15% SCBA) presents a type H mortar behavior, with better results than the control. By day 90, all replacements had the same resistance as M mortars and even higher resistances than the control. This demonstrates the feasibility of its use in the production of Portland cement for the manufacture of low‐performance inputs. This implies the possible reduction of impacts, both in waste disposal sites and in emissions caused by the construction industry, thus contributing to the circular economy.

Biomass gasification processes generate large amounts of solid. The aim of this work is to characterize the particles produced at a demonstration scale downdraft multi-stage gasification plant running on pinewood. The results have been used to understand their formation mechanism, evaluate potential applications and determine their hazardousness to human health and the environment. Chemical, physical, morphological and textural analyses suggest that most of the particles are formed via gas phase condensation reactions, with a very limited proportion resulting from direct carbonization of the original biomass feedstock. This is confirmed by a very limited micropore structure, surface area and adsorption capacity, making the particles unsuitable for use as an adsorbent in gas and water treatment applications. The particles exhibit superior fuel properties in terms of carbon content, heating value and thermal stability, which may be associated with the high temperatures at which they are generated. Due to their biomass origin, the particles contain a high proportion of calcium, potassium, magnesium and other plant micronutrients that could be beneficial if the material is used for soil conditioning and fertilizing. Regarding particle size distribution, most of the particles fitted in the range between 100 and 250 μm, with only 0.5 wt% smaller than 30 μm. This is too large for a carbon black surrogate but minimizes health risks associated with exposure to the lower regions of the respiratory tract. The concentration of biologically active PAH is sufficiently low to represent no hazard to the environment or human health.

Abstract Low-level technological radioactive wastes, in Spain, are commonly produced in research and medical centers. These wastes must be characterized before conditioning in order to determine their radioactive content for inventory purposes. A prototype has been designed for beta–gamma radiological characterization of standardized 25 l bags containing heterogeneous low-density technological radioactive wastes within the density range 0.05–0.6 g/cm 3 . The system consists of an iron shielding box with three NaI(Tl) and a silicon implanted detectors for gamma and gross beta activity determinations, respectively. The study of the measurement method, carried out with rotating scanning, included the optimization of the detection solid angle to minimize the uncertainties and the influence of the relative position of the radioactive material. Several materials and densities, in the range aforementioned, were considered to obtain the experimental attenuation factors, used for fitting a correction algorithm in function of density and γ-emission energy. The sensitivity of this method, calculated for the most frequent average density of this kind of waste (0.1 g/cm 3 ), is lower than 50 Bq/kg for the main β – γ emitters ( 137 Cs and 60 Co) and lower than 480 Bq/kg for gross beta activity.

AbstractAimTo explore the concept of sustainability in nursing using social media as a vehicle for discussion on the topic.BackgroundThere is a need for an increased awareness among nurses of the issues that are crucial for the healthcare sector to prepare for climate change and contribute to sustainable development. However, topics about sustainability and climate change are not a requirement of nursing curricula in Europe; social media provides an opportunity to raise issues and promote discussion.DesignA thematic analysis of a Twitter discussion.MethodsA Twitter discussion session hosted by @WeNurses took place on 24 March 2015 over 1 hour. Data were gathered via this online discussion hosted on Twitter, a social media platform. Following the discussion a thematic analysis of the posted Tweets was conducted.FindingsOne hundred and nineteen people posted nine hundred and ninety six Tweets, a reach of 3,306,368. Tweets broadly followed the questions posted by the team. Several threads related to the sustainable use of healthcare resources and the need to reduce waste was evident. A Word Cloud of the Tweets highlighted prominent words in the discussion: sustainability, nursing/nurses, curriculum, important, waste, practice, resources, student, plastic, health, gloves.ConclusionSocial media is an effective way of engaging nurses and students in a discussion on challenging issues. Sustainability appears to be important for nurses, with a particular emphasis on resource use and the importance of sustainability topics in nurse education.

Abstract The residual circulation of the Ria de Muros, a large coastal embayment in NW Spain, are studied using a three-dimensional baroclinic finite-difference model. The driving forces considered by the model include the tide, winds, river inflows and density forcing at the open boundary. In situ data of current velocity and direction, water level, wind velocity and direction, river discharge, and temperature and salinity are used for model validation. Simulated and observed time series of water level and current velocity are in good agreement. Once validated, the model is applied to compute the residual circulation induced by the relevant agents of the ria hydrodynamics—the tide, an upwelling-favourable wind characteristic of spring and summer, a downwelling-favourable wind typical of winter, and freshwater inflows associated with high river runoff. The resulting residual circulation differ notably. The tide does not generate significant residual flows except in the inner ria. By contrast, winds and river discharges induce important residual flows throughout; in the middle and outer ria they generate a 3D residual circulation pattern which renders the conventional two-layer scheme of estuarine circulation too simplistic in this case. Thus, this first application of a 3D numerical model to the Ria de Muros sheds new light on its fundamental hydrodynamics.