• Energy Research

The main object of this work is to present a “proof of concept” test of a method to produce Polyhydroxybutyrate (PHB) in the cathode of the Microbial Electrolysis Cell (MEC) utilizing directly the H2 gas via the electrons generated at the anode in the oxidation of an organic substance. A batch test in a rectangular microbial electrolysis cell has been performed at room temperature (20÷22 °C). In the anode compartment a solution of Volatile Fatty Acids was used as organic electrons donor while the cathode was filled with a mineral solution to assure the electrical continuity. A. eutrophus is able to growth and to produce PHB in autotrophic conditions on a gaseous substrate of H2, O2, CO2 using organic contaminated waste­water as electron donor. This seems a good option compared to an expensive substrate as glucose, even if a low PHB productivity was reached: about 2% after 3 days of batch test. Proceedings of the 19th European Biomass Conference and Exhibition, 6-10 June 2011, Berlin, Germany, pp. 2327-2331

Extra virgin olive-oil (EVO) production is an important economic activity for several countries, especially in the Mediterranean area such as Spain, Italy, Greece and Tunisia. The two major by-products from olive oil production, solid-liquid Olive Pomace (OP) and the Olive Mill Waste Waters (OMWW), are still mainly disposed on soil, in spite of the existence of legislation which already limits this practice. The present study compares the environmental impacts associated with two different scenarios for the management of waste from olive oil production through a comparative Life Cycle Assessment (LCA). The two alternative scenarios are: (I) Anaerobic Digestion and (II) Disposal on soil. The analysis was performed through SimaPro software and the assessment of the impact categories was based on International Life Cycle Data and Cumulative Energy Demand methods. Both the scenarios are mostly related to the cultivation and harvesting phase and are highly dependent on the irrigation practice and related energy demand. Results from the present study clearly show that the waste disposal on soil causes the worst environmental performance of all the impact categories considered here. Important environmental benefits have been identified when anaerobic digestion is chosen as the final treatment. It was consequently demonstrated that anaerobic digestion should be a feasible alternative for olive mills, to produce biogas from common olive oil residues, reducing the environmental burden and adding value to the olive oil production chain.

This Paper shows different biological routes to valorise the metabolic products of acidogenesis fermentation after H2 production and to increase the overall balance of bioenergy production as well. The routes go from a conventional anaerobic digestion till to a novel microbial electrolysis cells. We have demonstrated that methane production from volatile fatty acids can easily be established not only from anaerobic digestion technology, but also from a membraneless Microbial Electrolysis Cells (MEC) at ambient temperatures. The two­stages (H2+CH4) by AD is nowadays the most feasible and can increase energy efficiency from 11% (hydrogen only production) to 55%, leading to a positive net energy balance which is 11% more than traditional AD for only biogas production. Furthermore, test in a standard MEC was successfully conducted to produce H2 from sodium acetate, demonstrating that also this novel biotechnology can be used to extract further energy by end­products of H2­dark fermentation. Finally, a test was conduced to utilize in loco the produced H2 by MEC for the production of PHB. Results of this test reveals the feasibility of such process, even if further investigation are essential to increase the efficiency of PHB production. Proceedings of the 18th European Biomass Conference and Exhibition, 3-7 May 2010, Lyon, France, pp. 1395-1404

The study investigated and compared the anaerobic digestion (AD) of real organic fraction municipal solid waste (OFMSW) prior pre-treated with four types of pre-treatments: mechanical, thermal, hydrodynamic-cavitation (HC), and ultrasound (US). The tested pre-treatments and AD configurations were selected through Design of Experiments and then regression models were built to find the most promising configurations in terms of biogas production and energetic sustainability of the whole process. The novelty of the research is the simultaneously study of the working conditions of the pre-treatments; and AD parameters like the two origins of the inoculum, its incubation time, and the substrate: inoculum ratio (SI). The results demonstrated that the best configurations of pre-treatments and AD were the ones performed with thermal pre-treatment at 120 degrees C for 45 min (with inoculum incubation of 10 d at substrate: inoculum (SI) ratio of 2:1) and HC at 55 degrees C (with inoculum incubation of 10 d at SI of 3:1). The thermal, and to some extent the mechanical pre-treatment, evidenced as significant the interaction between the pre-treatment time and the inoculum incubation time. AD of US-OFMSW achieved the lowest performances since inhibition occurred, probably due to the lignocellulosic inhibitors release after ultrasound pre-treatment.

The characterization of anodic microbial communities is of great importance in the study of microbial fuel cells (MFCs). These kinds of devices mainly require a high abundance of anode respiring bacteria (ARB) in the anode chamber for optimal performance. This study evaluated the effect of different enrichments of environmental freshwater sediment samples used as inocula on microbial community structures in MFCs. Two enrichment media were compared: ferric citrate (FeC) enrichment, with the purpose of increasing the ARB percentage, and general enrichment (Gen). The microbial community dynamics were evaluated by polymerase chain reaction followed by denaturing gradient gel electrophoresis (PCR-DGGE) and real time polymerase chain reaction (qPCR). The enrichment effect was visible on the microbial community composition both during precultures and in anode MFCs. Both enrichment approaches affected microbial communities. Shannon diversity as well as β-Proteobacteria and γ-Proteobacteria percentages decreased during the enrichment steps, especially for FeC (p < 0.01). Our data suggest that FeC enrichment excessively reduced the diversity of the anode community, rather than promoting the proliferation of ARB, causing a condition that did not produce advantages in terms of system performance.

This study evaluated the key role of inoculum in mesophilic anaerobic digestion (AD) of Organic Fraction of Municipal Solid Waste. The effect of two different inocula, the mesophilic digestate of wastewater activated sludge (WAS) and the mesophilic digestate of cow-agriculture sludge (CAS), at three different substrate: inoculum ratios (1:2, 1:1 and 2:1) at three different incubation times (0, 5 and 10 d) were studied in batch feeding reactor for a total of 18 AD configurations. The AD configurations were study through specific biogas and methane productions, first order disintegration kinetics, Gompertz modified study and energy sustainable index. A multi criteria decision aid outranked the 18 AD configurations tested. The study proved that the AD performed with inoculum CAS incubated for 10 d at 2:1 substrate inoculum ratio reached the highest biogas yield and methene content equal to 997.81 NL/kgVS and 70.00% v/v.

Abstract Microbial fuel cell (MFC) is an upcoming technology that allows oxidizing organic matter to generate current by microorganism's activity. To render MFCs a cost-effective and energy sustainable technology, low-cost materials can be employed as support for bacteria growth and proliferation. With this purpose in mind, ceramic Berl saddles were opportunely covered by a thin and conductive carbon layer, thus obtaining an innovative low-cost anode material able to efficiently recover the electrons released by bacteria metabolisms. The conductive layer was obtained by using α- d -glucose deposition process within the following steps: impregnation, caramelization, and pyrolysis. In this way, a homogenous coating of polycrystalline graphitic carbon was successfully obtained and characterized by several methods. The carbon-coated Berl saddles were then tested as anode material in a two-compartment MFC prototype, in batch mode and using Saccharomyces cerevisiae as active microorganisms. The MFC performances were evaluated using electrochemical techniques. The carbon-coated Berl saddles showed a maximum power density of 130 mW m−2 (29.6 mA L−1) which is about 2–3 times higher than the values reported in literature by using commercial anode materials. In particular, we have carefully estimated the production and process costs of these carbon-coated Berl saddles used in our MFC prototype, obtaining a value comparable to the commercial carbon felt employed in the same MFC apparatus. All these results confirm that our innovative carbon-coated Berl saddles not only satisfy the electrical requirements, but also favor an optimal bacteria adhesion and can be produced as a low-cost anode for scaling-up MFC.

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°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.