In the past few years, thermally regenerative ammonia battery (TRAB) has been proposed as an effective tool to recover waste heat at temperatures below 130 °C. Most of the literature available is devoted to the power production step, with less attention being given to the regeneration step (e.g. the removal of ammonia from the anolyte). In this paper, the TRAB is analyzed with particular attention to the 15 regeneration step and to the study of various generation of energy-regeneration cycles. It was shown that approximately 90 °C is necessary for the regeneration step due to the fact that ammonia is present in the anolyte mainly as an ammonia complex. Various cycles were performed with success, demonstrating the efficacy of the proposed regeneration step.
In this work, four air-breathing microbial fuel cells (AB-MFC) were operated for 1 month in order to determine if the methodology of inoculation affects the steady-state performance of this type of MFCs. For this purpose, anaerobic and aerobic sludge were fed to two identical AB-MFCs without any external carbon source into a tight sealed environment during the first three days of start-up. For comparison purposes, other two AB-MFCs were operated mixing the initial sludge and an amount of sodium acetate as substrate. Results point out that the inoculation procedure does not affect the steady-state treatment capacity of the cells but it affects very seriously the production of electricity. Only the system fed with concentrated aerobic sludge was able to develop an efficient culture of bioelectrogenic microorganisms, while the other three systems failed in this purpose. This result was confirmed in a second independent series of experiments and by a last operation test, which consists of a re-inoculation of a low active MFC with microorganisms obtained from the best-performing cell in order to evaluate how much the MFC performance can be enhanced.
Waste minimization and circular thinking are to be achieved in order to cope with the limited amount of resources of our planet. In this perspective, bio-electrochemical systems (BESs) can contribute to the global balance with their ability to extract chemical residual energy from wastewater and transform it directly into electrical current. BESs development has been limited by the cost connected to reactor design, in which membranes and cathode catalyst constituted a major drawback. In this paper we report the optimization process of a simple reactor without membranes or precious catalyst that produced 47.1 mW m −2 , which is more than what achieved with configurations including membranes, operating in similar conditions (glycerol as substrate and hydraulic retention times of 3 days). In opposition to what is usually reported for conventional divided microbial fuel cells (MFCs), we have found that in this kind of reactor fermenting substrates (mainly glycerol) can give higher current density than non-fermentable ones (acetate). Feeding modality and proper electrode orientation were confirmed to have a dramatic impact on power output. Finally, a possible niche for the exploitation of our single chamber membraneless MFC was pointed out to exist in bio-refinery industry.
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