Abstract

The development of mobile systems for the decentralized pelletizing of forest-based residual biomass is currently underway. However, there is a lack of knowledge regarding the environmental impacts of such systems that needs to be developed for correct judgements on the most sustainable developing paths. The objective of this study was to quantify and compare the environmental impacts of a decentralized mobile production system for pelletizing logging residues in Northern Sweden operating at either the forest landing or forest terminal from a Life Cycle Assessment (LCA) perspective. The results showed that the landing- and terminal-based scenarios showed similar environmental profiles. The pelleting, transportation and drying stages of both scenarios were identified as environmental hotspots. These production stages accounted for 62%, 14% and 14% of the total greenhouse gas emissions, respectively. Key factors influencing the system were the use of electricity at terminals, the increase in pelletizer capacity, and long transportation distances. The use of a Swedish electricity mix instead of diesel based electricity in the terminal-based scenario reduced all of the environmental impacts by between 68% and 83%, with the exception of fresh water eutrophication potential, which increased by 26%. In conclusion, our findings indicate that an electrified mobile pellet production system with high operational efficiency and situated at a terminal close to the harvesting sites could, from an LCA point of view, be an interesting option for pelletizing Nordic logging residues, especially in regions with long transportation distances to industry.

Abstract

Pine (Pinus oocarpa) wood has great economic importance in Brazil. Pine stands represent the second largest reforested area in the country due to their industrial interest. Combining the relevance of industrial pine stands in the country and corresponding environmental concerns, this current study aims to identify and quantify the environmental impacts derived from industrial pine roundwood production in Brazil. The environmental study was developed considering the Life Cycle Assessment (LCA) methodology according to ISO14040 framework. The study convers the life cycle of pine roundwood production from cradle-to-forest gate perspective and considers the current practices in the country. The production system was divided in five main stages: Soil preparation, seedlings plantation, forest management, forest harvesting and infrastructure establishment. The environmental profile was estimated considering characterization factors from the ReCiPe method, in terms of twelve impact categories. According to the results, forest harvesting stage was identified as the environmental hotspot being the main responsible of contributions to nine impact categories under assessment with contributing ratios ranging from 21% (e.g., freshwater eutrophication) to 76% (e.g., photochemical oxidants formation). The high amount of fossil fuel required by heavy machinery used in the activities involved in this stage is behind this result. Soil preparation stage reported also an outstanding contribution in categories such as freshwater eutrophication (37%) and toxicity related categories (≈35%). The rationale behind these contributions is associated with the use of chemical fertilizers, mostly superphosphate. The identification of the environmental hotspots in forest biomass production can assist the Brazilian forest practitioners to improve the environmental profile by means of the optimization of forest practices.

Abstract

In recent decades, the wastewater treatment sector has undergone a shift to adapt to increasing discharge limits. In addressing the evaluation of innovative technologies, it is necessary to determine the scale at which reliable and representative values of environmental impacts and costs can be obtained, ensuring that the system under assessment follows the direction of eco-efficiency. This study has evaluated the environmental and economic indicators of an autotrophic nitrogen removal technology (ELAN®) from laboratory conception (1.5 L) to full scale (2 units of 115 m3) using the Life Cycle Assessment (LCA) methodology. Indirect emissions related to electricity consumption are the main contributor in all impact categories except eutrophication. Electricity consumption referred to the functional unit (1 m3 of treated wastewater) decreases as the scale increases. The rationale behind this can be explained, among other reasons, by the low energy efficiency of small-scale equipment (pumps and aerators). Accordingly, a value of approximately 25 kg CO2eq per m3 of treated water is determined for laboratory scale, compared to only 5 kg CO2eq per m3 at full-scale. When it comes to assessing the reliability of data, a pilot scale system of 0.2 m3 allowed to perform a trustworthy estimation of environmental indicators, which were validated at full-scale. In terms of operational costs, the scale of approximately 1 m3 provided a more accurate estimate of the costs associated with energy consumption.

Abstract

In the food industry, the brewing sector holds a strategic economic position since beer is the most consumed alcoholic beverage in the world. Brewing process involves the production of a large amount of lignocellulosic residues such as barley straw from cereal cultivation and brewer’s spent grains. This study was aimed at developing a full-scale biorefinery system for generating bio-ethanol and xylooligosaccharides (XOS) considering the mentioned residues as feedstock. Life Cycle Asssessment (LCA) methodology was used to investigate the environmental consequences of the biorefinery system paying special attention into mass and energy balances in each production section to gather representative inventory data. Biorefinery system was divided in five areas: i) reconditioning and storage, ii) autohydrolysis pretreatment, iii) XOS purification, iv) fermentation and v) bio-ethanol purification. LCA results identified two environmental hotspots all over the whole biorefinery chain: the production of steam required to achieve the large autohydrolysis temperature (responsible for contributions higher than 50% in categories such as acidification and global warming potential) and the production of enzymes required in the simultaneous saccharification and fermentation (>95% of contributions to terrestrial and marine aquatic ecotoxicity potentials). Since enzymes production involves high energy intensive background processes, the most straightforward improvement challenge should be focused on the production of steam. An alternative biorefinery scenario using wood chips as fuel source to produce heating requirements instead of the conventional natural gas was environmentally evaluated reporting improvements ranging from 44% to 72% in the categories directly affected by this hotspot.

Fermentation-derived bio-succinic acid (BioSA) is a valuable intermediate; it is used as a chemical building block, and has multiple industrial applications as an alternative to petroleum counterparts. The aim of this study was to develop a full-scale plant to produce BioSA from apple pomace, a low-cost solid waste from the cider- and juice-making industry, based on a biorefinery concept, and to determine its environmental profile using a cradle-to-factory-gate, scaled-up LCA approach. Foreground data used in this LCA were based on mass and energy flows, modelled in detail. The production process was divided into three stages: i) reconditioning and storage; ii) fermentation with Actinobacillus succinogenes; and iii) purification. The results indicate that the use of enzymes is responsible for the highest environmental burdens, due to their highly energy-intensive background production processes. When these were excluded from the analysis (following other studies available in the literature), the purification stage played an environmentally significant role, due to the extraction and distillation units involved. The electricity use and the requirements for organic solvents in these operations make up the largest environmental burdens. Thus, approaches with the highest potential for improvement must involve both operations. Alternatives for improvement are proposed that offer interesting potential reductions in the environmental profile, especially at the purification stage.

Abstract

A biological pretreatment of olive tree biomass (OTB) was carried out. First, seven white-rot fungi (WRF) were screened on solid-state fermentations by analyzing the substrate composition, ligninolytic enzymes production and enzymatic hydrolysis yields at three different pretreatment times (15, 30 and 45 days). Glucose released by enzymatic hydrolysis of OTB pretreated with Irpex lacteus for 45 days doubled that obtained with the control (non-inoculated). In addition, to enhance this yield, the combination of fungal pretreatment with a chemical pretreatment was studied. It was also found that the order of the pretreatment combination has a relevant effect on the glucose yield. Thereby, the best option determined, fungal pretreatment with I. lacteus after 28 days of culture followed by diluted acid pretreatment (2% w/v H2SO4, 130 °C and 90 min), enhanced 34% the enzymatic hydrolysis yield compared with the acid pretreatment alone. Applying the best pretreatment combination, the overall sugar yield of the whole process (sequential pretreatment plus enzymatic hydrolysis) was 51% of the theoretical yield.

Abstract

Biotransformation of most organic micropollutants (OMPs) during wastewater treatment is not complete and an unexplained steady decrease of the biotransformation rate with time is reported for many OMPs in different biological processes. To minimize and accurately predict the emission of OMPs into the environment, the mechanisms and limitations behind their biotransformations should be clarified. Aiming to achieve this objective, the present study follows a mechanistic modelling approach, based on the formulation of four models according to different biotransformation hypotheses: Michaelis-Menten kinetics, chemical equilibrium between the parent compound and the transformation product (TP), enzymatic inhibition by the TP, and a limited compound bioavailability due to its sequestration in the solid phase. These models were calibrated and validated with kinetic experiments performed in two different anaerobic systems: continuous reactors enriched with methanogenic biomass and batch assays with anaerobic sludge. Model selection was conducted according to model suitability criteria (goodness of fitting the experimental data, confidence of the estimated parameters, and model parsimony) but also considering mechanistic evidences. The findings suggest that reversibility of the biological reactions and/or sequestration of compounds are likely the causes preventing the complete biotransformation of OMPs, and biotransformation is probably limited by thermodynamics rather than by kinetics. Taking into account its simplicity and broader applicability spectrum, the reversible biotransformation is the proposed model to explain the incomplete biotransformation of OMPs.

Abstract

This article examines the potential benefits of using Data Envelopment Analysis (DEA) for conducting energy-efficiency assessment of wastewater treatment plants (WWTPs). WWTPs are characteristically heterogeneous (in size, technology, climate, function …) which limits the correct application of DEA. This paper proposes and describes the Robust Energy Efficiency DEA (REED) in its various stages, a systematic state-of-the-art methodology aimed at including exogenous variables in nonparametric frontier models and especially designed for WWTP operation. In particular, the methodology systematizes the modelling process by presenting an integrated framework for selecting the correct variables and appropriate models, possibly tackling the effect of exogenous factors. As a result, the application of REED improves the quality of the efficiency estimates and hence the significance of benchmarking. For the reader's convenience, this article is presented as a step-by-step guideline to guide the user in the determination of WWTPs energy efficiency from beginning to end. The application and benefits of the developed methodology are demonstrated by a case study related to the comparison of the energy efficiency of a set of 399 WWTPs operating in different countries and under heterogeneous environmental conditions.

Abstract

Anaerobic fermentation of organic wastes using microbial mixed cultures is a promising avenue to treat residues and obtain added-value products. However, the process has some important limitations that prevented so far any industrial application. One of the main issues is that we are not able to predict reliably the product spectrum (i.e. the stoichiometry of the process) because the complex microbial community behaviour is not completely understood. To address this issue, in this work we propose a new metabolic network of glucose fermentation by microbial mixed cultures that incorporates electron bifurcation and homoacetogenesis. Our methodology uses NADH balances to analyse published experimental data and evaluate the new stoichiometry proposed. Our results prove for the first time the inclusion of electron bifurcation in the metabolic network as a better description of the experimental results. Homoacetogenesis has been used to explain the discrepancies between observed and theoretically predicted yields of gaseous H2 and CO2 and it appears as the best solution among other options studied. Overall, this work supports the consideration of electron bifurcation as an important biochemical mechanism in microbial mixed cultures fermentations and underlines the importance of considering homoacetogenesis when analysing anaerobic fermentations.

Abstract The aim of this study was to compare the environmental performance and sustainability of different management options for livestock waste in Cyprus. The two most common practices in the country, i.e. the use of anaerobic lagoons and conventional biogas plants, were compared with the innovative scheme developed in the LiveWaste project (LIFE12 ENV/CY/000544), which aims not only to produce bioenergy, but also to treat the digestate for nutrient recovery and water reuse. The Life Cycle Assessment (LCA) methodology was combined with the Analytic Hierarchy Process (AHP) to compare the performance of these alternatives. Four relevant indicators were selected for each dimension of sustainability (environmental, social and economic). The results of the evaluations showed that anaerobic lagoons are not an appropriate option for the sustainable management of livestock waste due to environmental (e.g. climate change, acidification and eutrophication) and social impacts (e.g. noise exposure, visual impact and risk perception for human health). The most important strengths and weaknesses of anaerobic treatment with and without digestate treatment were identified. Compared to conventional anaerobic digestion where digestate is directly applied as an organic fertiliser, the technology proposed in the project entails higher technological complexity due to nitrogen removal and phosphorus recovery. The rise in chemical and electricity requirements increased the impacts on some indicators, such as climate change and operational cost (emissions of greenhouse gases and operation costs were around 50% higher), while reduced impacts in others due to proper nutrient management, as acidification and eutrophication impacts (which were 10 and almost two times lower, respectively). For the specific Cypriot conditions, where the overapplication of nutrients leads to pollution of water bodies, the innovative treatment scheme with higher technological development presents an interesting approach. Nevertheless, the treatment of the digestate should be analysed taking into account the specific characteristics of each scenario.

https://doi.org/10.1016/j.scitotenv.2018.03.299

Abstract

Organic micropollutants (OMPs) comprise a wide group of substances highly consumed in modern societies. There has been a growing social and scientific interest on OMPs in wastewaters in the twentyfirst century. This research paper has identified the evolution of the research trends in the period 2001–2017 on OMPs fate during secondary wastewater treatment. These trends have moved from a global perspective on the occurrence of OMPs in wastewaters to more specific research focussed on understanding their behaviour during advanced treatment processes. Based on a bibliometric analysis carried out using one of the leading scientific databases, pharmaceuticals have been identified as the main group of OMPs. An increasing number of publications have been released on the fate of pharmaceuticals in wastewater with a growing number of countries involved: from 38 publications belonging to 14 countries in first 5-year period analysed (2001–2005) up to 138 from 42 countries only in the last 2 years (2016–2017). The main operational conditions in wastewater treatment plants influencing the removal of OMPs, as well as the mechanisms involved depending on the physico-chemical characteristics of the substances are reviewed. The paper also considers the role of microbial populations, as well as technological and operational features in OMPs abatement. Finally, a specific section is dedicated to the metabolic and cometabolic biotransformations of some OMPs taking place under heterotrophic, nitrifying and anaerobic conditions, a more novel research trend explored more recently.

Abstract

Granular activated carbon (GAC) is applied as post-treatment technology in wastewater treatment plants (WWTPs) in order to increase the elimination of organic micropollutants (OMPs). However, the efficiency and life-time of GAC depend on several parameters, such as the quality of the effluent to be treated or the type of GAC. In the present paper, two types of GAC, based on bituminous carbon (BC-GAC) and coconut shell (CS-GAC), were assessed from a technical, economic and environmental point of view to further remove OMPs present in two secondary effluents, coming from integrated biological systems with a membrane or a settler, respectively. Although all GAC filters were efficient in removing selected OMPs, the quality of the secondary effluent had a strong influence on the lifespan of adsorbent material and the technical operability of the filtration systems. While GAC filters treating membrane effluent were highly effective to remove recalcitrant compounds, such as carbamazepine and diazepam (>80%), even after 430 d of operation (>30,800 BV), the efficiency of GAC filters treating settler effluent quickly lowered to 50% after 100 d of operation (<7200 BV). Both types of GAC showed similar adsorption capacities and only slight differences were found in terms of costs (2.4 €/kg vs 2.7 €/kg). However, CS-GAC has a lower carbon footprint than BC-GAC, mainly due to the more environmentally friendly production process of CS-GAC.

Abstract

Humic acid has a controversial effect on the biological treatment processes. Here, we have investigated humic acid effects on the Anammox activity by studying the nitrogen removal efficiencies in batch and continuous conditions and analyzing the microbial community using Fluorescence in situ hybridization (FISH) technique. The results showed that the Anammox activity was affected by the presence of humic acid at a concentration higher than 70 mg/L. In fact, in the presence of humic acid concentration of 200 mg/L, the Anammox activity decreased to 57% in batch and under continuous condition, the ammonium removal efficiencies of the reactor decreased from 78 to 41%. This reduction of Anammox activity after humic acid addition was highlighted by FISH analysis which revealed a considerable reduction of the abundance of Anammox bacteria and the bacteria living in symbiosis with them. Furthermore, a total inhibition of Candidatus Brocadia fulgida was observed. However, humic acid has promoted heterotrophic denitrifying bacteria which became dominant in the reactor. In fact, the evolution of the organic matter in the reactor showed that the added humic acid was used as carbon source by heterotrophic bacteria which explained the shift of metabolism to the favor of heterotrophic denitrifying bacteria. Accordingly, humic acid should be controlled in the influent to avoid Anammox activity inhibition.

Abstract

A single stage partial nitritation and anammox granular pilot scale reactor (600 L) was operated to treat primary settled sewage in an urban wastewater treatment plant. The fed wastewater contained low total nitrogen concentrations of 6–25 mg TN/L and the system operated without temperature control ranging from 18 to 12 °C. A control strategy, based on the pH value, was applied to stop the aeration supply. The pH set-point was fixed at 6.0 and allowed obtaining a total nitrogen removal efficiency approximately of 50% treating a load of 67 mg TN/(L·d) without the addition of any chemicals. Although nitrite oxidizing bacteria were present in the inoculated sludge, when the pH-based control was implemented (day 30) the ammonium oxidation was favored compared to the nitrite oxidation activity. Then, the system operated stable the rest of the operational period (days 30–94) despite the presence of organic matter in the wastewater and the high variability of nitrogen load and temperature during the operation. Nitrogen was autotrophically removed accomplishing the stringent discharge limits (10 mg TN/L) and nitrate concentrations in the effluent lower than 3 mg NO3−-N/L. Both biomass concentration and granules size increased during the operational period indicating the growth of the biomass inside the reactor and therefore the potential treatment capacity.

Abstract

The general framework of the Chemical Engineering studies in Spain includes the Bachelor's Degree (4 years), Master's Degree (the most common duration is 1.5 years) and Doctorate (3-4 years). In 2008, the Conference of Directors and Deans of Chemical Engineering (CODDIQ) was constituted with the main objective of promoting and improving the quality of Chemical Engineering studies in Spain. Currently, Faculties and Schools of 29 Spanish universities are members of CODDIQ. An analysis of the most characteristic indicators provides a representative radiography of the Chemical Engineering Studies in Spain, whose most outstanding data are: (i) 7,396 undergraduate students, 1,014 Master students and 556 PhD students, (ii) according to the gender profile of undergraduates and graduates, the percentage of women is similar to that of men, while for faculty staff, the percentage of women is 43% and 46% for Associate and Assistant Professor (respectively) and 23% for the category of Full Professor category; (iii) after completing the Bachelor studies, most of them continue their training in the MSc in Chemical Engineering, (iv) the employability after obtaining the Master's degree is very high (>75%), which in the case of PhDs is close to 100%. The studies of Chemical Engineering in Spain have a very direct relationship with society, especially in the chemical, environmental, biotechnological and energy fields. The companies that collaborate in the training of future professionals are distributed throughout the national territory, which allows a strong connection with the socioeconomic environment.