Tonia Tommasi

Electrochemical and impedance characterization of Microbial Fuel Cells based on 2D and 3D anodic electrodes working with seawater microorganisms under continuous operation.

A mixed microbial population naturally presents in seawater was used as active anodic biofilm of two Microbial Fuel Cells (MFCs), employing either a 2D commercial carbon felt or 3D carbon-coated Berl saddles as anode electrodes, with the aim to compare their electrochemical behavior under continuous operation. After an initial increase of the maximum power density, the felt-based cell reduced its performance at 5 months (from 7 to 4 μW cm(-2)), while the saddle-based MFC exceeds 9 μW cm(-2) (after 2 months) and maintained such performance for all the tests. Electrochemical impedance spectroscopy was used to identify the MFCs controlling losses and indicates that the mass-transport limitations at the biofilm-electrolyte interface have the main contribution (>95%) to their internal resistance. The activation resistance was one order of magnitude lower with the Berl saddles than with carbon felt, suggesting an enhanced charge-transfer in the high surface-area 3D electrode, due to an increase in bacteria population growth.

Acid pre-treatment of sewage anaerobic sludge to increase hydrogen producing bacteria HPB: effectiveness and reproducibility.

The present study is aimed to test the effectiveness and the reproducibility of the acid pre-treatment of sewage sludge to suppress the methanogenic bacteria activity, in order to increase the hydrogen forming bacteria activity, mainly Clostridium species. The treated sludge has been tested on glucose reach medium under mesophilic conditions (35 degrees C), in batch mode to quantify the biological fermentative hydrogen production. In the whole series of experiments, the main components of biogas are hydrogen (52-60%) and carbon dioxide (40-48%); no methane and hydrogen sulphide were present in it. The rate of biogas production reached a maximum of 75 ml/lh. An overall mean hydrogen conversion efficiency was 11.20% on the assumption of maximum of 3 mol H2/mol glucose. Clostridium spp. multiplied ten times after 10 h of fermentation and over that thousand times at the end of fermentation.

Additive Manufacturing of a Microbial Fuel Cell—A detailed study

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m−3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments.

Pyrolytic carbon-coated stainless steel felt as a high-performance anode for bioelectrochemical systems.

Scale up of bioelectrochemical systems (BESs) requires highly conductive, biocompatible and stable electrodes. Here we present pyrolytic carbon-coated stainless steel felt (C-SS felt) as a high-performance and scalable anode. The electrode is created by generating a carbon layer on stainless steel felt (SS felt) via a multi-step deposition process involving α-d-glucose impregnation, caramelization, and pyrolysis. Physicochemical characterizations of the surface elucidate that a thin (20±5μm) and homogenous layer of polycrystalline graphitic carbon was obtained on SS felt surface after modification. The carbon coating significantly increases the biocompatibility, enabling robust electroactive biofilm formation. The C-SS felt electrodes reach current densities (jmax) of 3.65±0.14mA/cm(2) within 7days of operation, which is 11 times higher than plain SS felt electrodes (0.30±0.04mA/cm(2)). The excellent biocompatibility, high specific surface area, high conductivity, good mechanical strength, and low cost make C-SS felt a promising electrode for BESs.

On the pre-treatment of municipal organic waste towards fuel production: a review.

Lignocelluloses are the main constituents of municipal organic waste (MOW). In order to increase the production of fuels, via fermentations, the enzymatic hydrolysis is the first step towards a valorisation process. It is well-known that the hydrolysis of lignocelluloses is not very effective because of the high stability of the constituents. In this respect the pre-treatment of MOW is necessary to increase the efficiency of the biological processes. Several pre-treatment processes are reviewed and analysed in the paper and the drawbacks are pointed out. The fundamental scientific features are highlighted and details are given on the technological parameters. The increase in the availability of sugars after pre-treatment seems to be rather high. The necessity of setting up a design procedure and defining scale-up criteria for the full scale pre-treatment of MOW are problems that still need to be overcome in order to extend the technology to MSW treatment field. A pilot plant of adequate potentiality is shown in an attempt to cover this gap.

New insights in Microbial Fuel Cells: novel solid phase anolyte

For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.

Sustainability of (H2 + CH4) by Anaerobic Digestion via EROI Approach and LCA Evaluations

The contents of this Chapter focus on the theoretical sustainable energy approach and its application to hydrogen and methane production, on the basis of results obtained from experimental tests on the Anaerobic Digestion (AD) technology. The evaluation of sustainability is pursued through the life cycle assessment (LCA), energy return on investment (EROI) and energy payback time (EPT) approaches. The EROI and EPT parameters are defined and applied to score the sustainability of the H2/CH4 energy carrier. The evaluation of the indirect energy following a life cycle assessment is consistent for the sustainability analysis. The sustainability of AD technology strongly depends on the reactor diameter: for values lower than 1 m the technology is not able to sustain the well-being of the society; the effect of the insulating material as well as the labor could be very important, and in this respect, thus, a sensitivity analysis on the sustainability is reported.

Pretreatment to Increase Hydrogen Producing Bacteria (HPB)

This chapter focuses on the investigation of an easy and efficacious method of obtaining a hydrogen-producing bacteria (HPB) culture to the detriment of hydrogen-consuming bacteria (HCB), such as methanogens and homoacetogenic bacteria. Although the use of mixed microflora is more viable from both the practical and biological points of view, important limitations arise from the co-activity of HPB and HCB. In this respect, pretreatment is one of the most important issues in anaerobic hydrogen production, in order to produce suitable inocula of HPB. In particular, we investigated the effectiveness of acid pretreatment applied to mixed microflora in order to stop methanogen activity. We evaluated the content of Clostridium bacteria, which are the main ones responsible for H2 fermentation in two of the most widely used inoculum sources: anaerobic sludge from wastewater treatment plants and rumen microorganisms from cow stomachs.

A Low complexity wireless microbial fuel cell monitor using piezoresistive sensors and impulse-radio ultra-wide-band

Microbial Fuel Cells (MFCs) are energy sources which generate electrical charge thanks to bacteria metabolism. Although functionally similar to chemical fuel cells (both including reactants and two electrodes, and anode and cathode), they have substantial advantages, e.g. 1) operation at ambient temperature and pressure; 2) use of neutral electrolytes and avoidance of expensive catalysts (e.g. platinum); 3) operation using organic wastes. An MFC can be effectively used in environments where ubiquitous networking requires the wireless monitoring of energy sources. We then report on a simple monitoring system for MFC comprising an ultra-low-power Impulse-Radio Ultra-Wide-Band Transmitter (TX) operating in the low 0-960MHz band and a nanostructured piezoresistive pressure sensor connected to a discrete component digital read-out circuit. The sensor comprises an insulating matrix of polydimethylsiloxane and nanostructured multi-branched copper microparticles as conductive filler. Applied mechanical stress induces a sample deformation that modulates the mean distance between particles, i.e. the current flow. The read-out circuit encodes pressure as a pulse rate variation, with an absolute sensitivity to the generated MFC voltage. Pulses with variable repetition frequency can encode battery health: the pressure sensor can be directly connected to the cells membrane to read excessive pressure. A prototype system comprises two MFCs connected in series to power both the UWB transmitter which consumes 40μW and the read-out circuit. The two MFC generate an open circuit voltage of 1.0±0.1V. Each MFC prototype has a total volume of 0.34L and is formed by two circular Poly(methyl methacrylate) (PMMA) chambers (anode and cathode) separated by a cation exchange membrane. The paper reports on the prototype and measurements towards a final solution which embeds all functionalities within a MFC cell. Our solution is conceived to provide energy sources integrating energy management and health monitoring capabilities to sensor nodes which are not connected to the energy grid.

EAB—Electroactive Biofilm: A Biotechnological Resource

In nature, special kind of microorganisms has evolved strategies to transport electrons over biological membranes to or from their extracellular environment. In the presence of an electrode these bacteria are able to generate or consume current by using the electrode as electron acceptor or electron donor, respectively. In order to maximize their interaction with the electrode, they colonize the electrode surface, forming the so-called EAB—electroactive biofilm. EEAB plays a fundamental role in bioelectrochemical systems, multidisciplinary research technology for energy or bioproduct recovery and simultaneous wastewater treatment or soil bioremediation. This article aims to provide the reader an insight into the concept of EAB, giving an overview of the current applications for EAB-based technologies. How multiple parameters affect EAB formation and optimization is briefly introduced. The key features of exoelectrogenic as well as electrotrophic biofilms are discussed, including inward and outward electron transfer mechanisms occurring at the biofilm–electrode interphase. Furthermore, a brief overview of the best-known electroactive microorganism species is reported. Finally, the last paragraph summarizes the most relevant techniques available for the characterization of electrode-colonizing microbial communities, electron transfer mechanisms and biofilm structure and composition.