A.P. de los Ríos

Process design and economic analysis of a hypothetical bioethanol production plant using carob pod as feedstock

A process for the production of ethanol from carob (Ceratonia siliqua) pods was designed and an economic analysis was carried out for a hypothetical plant. The plant was assumed to perform an aqueous extraction of sugars from the pods followed by fermentation and distillation to produce ethanol. The total fixed capital investment for a base case process with a capacity to transform 68,000 t/year carob pod was calculated as 39.61 millon euros (€) with a minimum bioethanol production cost of 0.51 €/L and an internal rate of return of 7%. The plant was found to be profitable at carob pod prices lower than 0.188 €/kg. An increase in the transformation capacity of the plant from 33,880 to 135,450 t/year was calculated to result in an increase in the internal rate of return from 5.50% to 13.61%. The obtained results show that carob pod is a promising alternative source for bioethanol production.

Ionic liquid technology to recover volatile organic compounds (VOCs)

Volatile organic compounds (VOCs) comprise a wide variety of carbon-based materials which are volatile at relatively low temperatures. Most of VOCs pose a hazard to both human health and the environment. For this reason, in the last years, big efforts have been made to develop efficient techniques for the recovery of VOCs produced from industry. The use of ionic liquids (ILs) is among the most promising separation technologies in this field. This article offers a critical overview on the use of ionic liquids for the separation of VOCs both in bulk and in immobilized form. It covers the most relevant works within this field and provides a global outlook on the limitations and future prospects of this technology. The extraction processes of VOCs by using different IL-based assemblies are described in detail and compared with conventional methods This review also underlines the advantages and limitations posed by ionic liquids according to the nature of the cation and the anions present in their structure and the stability of the membrane configurations in which ILs are used as liquid phase.

Microalgae as substrate in low cost terracotta-based microbial fuel cells: Novel application of the catholyte produced.

In this work, the by-product generated during the operation of cylindrical MFCs, made out of terracotta material, is investigated as a feasible means of degrading live microalgae for the first time. In addition to the low cost materials of this design, the reuse of the solution produced in the cathode renders the technology truly green and capable of generating bioenergy. In this study, the effect of a light/dark cycle or dark conditions only on the digestion of live microalgae with the catholyte is investigated. The results show that a combination of light/dark improves degradation and allows algae to be used as substrate in the anode. The addition of 12.5mL of a 1:1 mix of catholyte and microalgae (pre-digested over 5days under light/dark) to the anode, increases the power generation from 7μW to 44μW once all the organic matter in the anode had been depleted.

Over-activity and stability of laccase using ionic liquids: screening and application in dye decolorization

The use of a wide range of water miscible and immiscible ionic liquids (ILs) as reaction media for ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) oxidation by Trametes versicolor laccase was studied. Thirteen ILs were shown to be suitable media for the laccase oxidation reaction, increasing the activity with respect to conventional media. Among them, the water-miscible IL choline dihydrogen phosphate [Chol][H2PO4] allowed over-laccase activity with an enhancement rate of 451% at 25 °C and pH 7.0. This ionic liquid improved the stability of the enzyme in the face of high temperature and high pH, while storage at room temperature in aqueous medium was increased up to 4.5 times. Moreover, it was found that in the reaction medium for decolourizing dyes (antraquinonic and azoic) using laccase increased the decolourization rate by up to 216% and 137% for the azoic dyes Acid Black 1 and Remazol Brilliant Blue R, respectively. A high decolorization rate was also obtained for a mixture of dyes (80% within 8 h). To understand the effect of [Chol][H2PO4] on the secondary protein structure of the laccase, several spectroscopic techniques were used such as Circular Dichroism (CD), Fourier transform infrared (FT-IR) and Fluorescence, all of which demonstrated that the β sheet structure was affected. A shift to an α-helix structure [Chol][H2PO4] could be responsible for the enhancement of the enzyme activity observed at 300 mM.

A Box–Behnken Design-Based Model for Predicting Power Performance in Microbial Fuel Cells Using Wastewater

Although modeling is regarded as a useful tool to understand the performance of microbial fuel cells (MFCs), the number of MFC models remains very low compared with the number of experimental works available in the literature. Moreover, there are very few MFC modeling attempts dealing with the use of wastewater as fuel in these devices, which is essential for the practical implementation of MFCs since the potential of this technology lies in the two-fold benefit of wastewater treatment and bioenergy generation. In this work, a four-factor three-level Box–Behnken design was developed to model the electrochemical power generation in two-chamber MFCs using wastewater as fuel. The optimum values of temperature, external resistance, feed concentration and anodic pH that maximized power output were investigated. Optimum conditions were found at T = 35°C and R = 1 kΩ, corresponding to a maximum power density of 0.88 W·m−3, while feed concentration and pH did not show statistical significance in the ranges studied. Thus, a Box–Behnken design-based model as empirical approach could provide an effective tool for the optimization study of MFC systems.

Synthesis of low cost organometallic-type catalysts for their application in microbial fuel cell technology

ABSTRACT Microbial fuel cells (MFCs) are a promising technology that generates electricity from several biodegradable substrates and wastes. The main drawback of these devices is the need of using a catalyst for the oxygen reduction reaction at the cathode, which makes the process relatively expensive. In this work, two low cost materials are tested as catalysts in MFCs. A novel iron complex based on the ligand n-phenyledenparaethoxy aniline has been synthesized and its performance as catalyst in single chamber MFCs containing ionic liquids has been compared with a commercial inorganic material such as Raney nickel. The results show that both materials are suitable for bioenergy production and wastewater treatment in the systems. Raney nickel cathodes allow MFCs to reach a maximum power output of 160u2005mW.m−3 anode, while the iron complex offers lower values. Regarding the wastewater treatment capacity, MFCs working with Raney nickel-based cathodes reach higher values of chemical oxygen demand removal (76%) compared with the performance displayed by the cathodes based on Fe-complex (56%).