Renewable sustainable biocatalyzed electricity production in a photosynthetic algal microbial fuel cell (PAMFC)

Electricity production via solar energy capturing by living higher plants and microalgae in combination with microbial fuel cells are attractive because these systems promise to generate useful energy in a renewable, sustainable, and efficient manner. This study describes the proof of principle of a photosynthetic algal microbial fuel cell (PAMFC) based on naturally selected algae and electrochemically active microorganisms in an open system and without addition of instable or toxic mediators. The developed solarpowered PAMFC produced continuously over 100 days renewable biocatalyzed electricity. The sustainable performance of the PAMFC resulted in a maximum current density of 539 mA/m2 projected anode surface area and a maximum power production of 110 mW/m2 surface area photobioreactor. The energy recovery of the PAMFC can be increased by optimization of the photobioreactor, by reducing the competition from non-electrochemically active microorganisms, by increasing the electrode surface and establishment of a further-enriched biofilm. Since the objective is to produce net renewable energy with algae, future research should also focus on the development of low energy input PAMFCs. This is because current algae production systems have energy inputs similar to the energy present in the outcoming valuable products

A mathematical model for composting kinetics

Composting plays an important role in waste management schemes and organic farming, as the compost produced enables reuse of organic matter and nutrients. Modern composting plants must comply with strict environmental regulations, including gas emissions such as nuisance odors. Designing composting plants to meet these requirements using current trial-and-error strategies is too costly and time consuming and poor performance and failure are too often the result. Mathematical reactor models can serve as an essential tool for faster and better process designs, system analysis, and operational guidance.However, all reactor models developed so far are based on empirical kinetic formulations, restricting the generality and thus applicability of the results. To achieve greater generality for design and analysis, a mechanistic model for composting kinetics is needed. Any mechanistic model is based on a number of assumptions and must be validated against experiments. To make validation possible, all model parameters must be identifiable. A parameter is identifiable if one can uniquely determine its value from the data at hand. The objective of this thesis is to develop a mechanistic kinetic model of the composting process whose parameters are all identifiable.This thesis has been structured in three main parts.The first part, "dimensional identifiability analysis," is concerned with the use of dimensional analysis of parameter identifiability. Together with a proposed modified deductive modeling strategy, this part of the thesis is a methodological contribution to modeling of relatively complex systems with limited available measurements.The second part, "the single particle model," is focuses on the development and validation of a theoretical model for the aerobic degradation of a single waste particle. This theoretical model gives insight into the processes occurring within a composting waste particle. An analytical solution of this model, containing only identifiable parameters, is both derived and validated.The third part of the thesis, "the distributed model," deals with the development, validation and application of a kinetic model for a waste consisting of a distributed range of waste particle sizes. The model is based on a distribution function describing the particle size distribution and the previously developed analytical solution to the identifiable single particle model. The distributed model is validated and is used to analyze aeration requirements, compost quality and compost quantity for a new composting reactor concept. This model application shows the advantages of the distributed model relative to previous first order models for reactor design and analysis.</p

New applications and performance of bioelectrochemical systems

Bioelectrochemical systems (BESs) are emerging technologies which use microorganisms to catalyze the reactions at the anode and/or cathode. BES research is advancing rapidly, and a whole range of applications using different electron donors and acceptors has already been developed. In this mini review, we focus on technological aspects of the expanding application of BESs. We will analyze the anode and cathode half-reactions in terms of their standard and actual potential and report the overpotentials of these half-reactions by comparing the reported potentials with their theoretical potentials. When combining anodes with cathodes in a BES, new bottlenecks and opportunities arise. For application of BESs, it is crucial to lower the internal energy losses and increase productivity at the same time. Membranes are a crucial element to obtain high efficiencies and pure products but increase the internal resistance of BESs. The comparison between production of fuels and chemicals in BESs and in present production processes should gain more attention in future BES research. By making this comparison, it will become clear if the scope of BESs can and should be further developed into the field of biorefineries

Microbial solar cells: applying photosynthetic and electrochemically active organisms

Microbial solar cells (MSCs) are recently developed technologies utilizing solar energy to produce electricity or chemicals. MSCs use photoautotrophic microorganisms or higher plants to harvest solar energy, and use electrochemically active microorganisms in the bioelectrochemical system to generate electrical current. Here, we review the principles and performance of various MSCs, in an effort to identify the most promising systems as well as the bottlenecks and potential solutions towards „real life. MSC application. We give an outlook on future applications based on the intrinsic advantages of MSCs, showcasing specifically how these living energy systems can facilitate the development of an electricity-producing green roof.This is a "Post-Print" accepted manuscript, which has been published in "Trends in Biotechnology". This version is distributed under the Creative Commons Attribution 3.0 Netherlands License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Please cite this publication as follows: 2011 Trends in Biotechnology Microbial solar cells: applying photosynthetic and electrochemically active organisms. David P.B.T.B. Strik, Ruud A. Timmers, Marjolein Helder, Kirsten J.J. Steinbusch, Hubertus V.M. Hamelers, , Cees J.N. Buisman. Trends in Biotechnology 29 (1), 41-49 You can download the published version at: http://dx.doi.org/10.1016/j.tibtech.2010.10.00

Salinity Gradients for Sustainable Energy: Primer, Progress, and Prospects

Combining two solutions of different composition releases the Gibbs free energy of mixing. By using engineered processes to control the mixing, chemical energy stored in salinity gradients can be harnessed for useful work. In this critical review, we present an overview of the current progress in salinity gradient power generation, discuss the prospects and challenges of the foremost technologies — pressure retarded osmosis (PRO), reverse electrodialysis (RED), and capacitive mixing (CapMix) and provide perspectives on the outlook of salinity gradient power generation. Momentous strides have been made in technical development of salinity gradient technologies and field demonstrations with natural and anthropogenic salinity gradients (for example, seawater–river water and desalination brine-wastewater, respectively), but fouling persists to be a pivotal operational challenge that can significantly ebb away cost-competitiveness. Natural hypersaline sources (e.g., hypersaline lakes and salt domes) can achieve greater concentration difference and, thus, offer opportunities to overcome some of the limitations inherent to seawater–river water. Technological advances needed to fully exploit the larger salinity gradients are identified. While seawater desalination brine is a seemingly attractive high salinity anthropogenic stream that is otherwise wasted, actual feasibility hinges on the appropriate pairing with a suitable low salinity stream. Engineered solutions are foulant-free and can be thermally regenerative for application in low-temperature heat utilization. Alternatively, PRO, RED, and CapMix can be coupled with their analog separation process (reverse osmosis, electrodialysis, and capacitive deionization, respectively) in salinity gradient flow batteries for energy storage in chemical potential of the engineered solutions. Rigorous techno-economic assessments can more clearly identify the prospects of low-grade heat conversion and large-scale energy storage. While research attention is squarely focused on efficiency and power improvements, efforts to mitigate fouling and lower membrane and electrode cost will be equally important to reduce levelized cost of salinity gradient energy production and, thus, boost PRO, RED, and CapMix power generation to be competitive with other renewable technologies. Cognizance of the recent key developments and technical progress on the different technological fronts can help steer the strategic advancement of salinity gradient as a sustainable energy source