Microbial fuel cells (MFCs) seems to be progressing at an amazing speed in the past few years, with higher power density but lower cost being continuously achieved and have created a promising future for us. Thus bioelectricity production technology using microbes can act very well as a sustainable renewable source of energy. Till now, a large number of microbes and a variety of substrates (including waste) have been used to produce electricity. In our study we have identified the documents showing bioelectricity production using bacteria (more preferably Geobacter spp.), where the power output of more than 25W (upto 300 W) is produced using microbial fuel cells.
The elevating energy crisis due to both prevailing and prospective exhaustion of natural and non-renewable energy resources has gripped the whole world. Due to continuing economic growth and expanding population, world energy consumption is expected to increase nearly 50% between 2001 and 2050 . Thus, all sorts of ideas and inventions for developing greener and more efficient methods of energy generation are increasingly being hailed across the globe.
Till now, so many renewable resources like solar, wind, water energy etc, has been studied thoroughly to determine their efficiency compared to highly efficient current resources such as coal, natural gas, petroleum etc. However, due to various limitations they may not be as efficient as required. Firstly, they depend upon climatic condition for final output, restricting their application in other areas in which climate is highly fluctuating or is not available at an amount suitable for power production. Like, wind energy cannot be used in area with slow wind or solar based resources are completely useless in places where the sun is not available or covered with clouds for most of the time in a year. Moreover, they do not provide continuous and constant power output. Thus urging a need to identify or develop alternative energy resources, which are renewable and practically sustainable replacement to the current resources.
Biological Products are made from living organisms. The material they are made from can come from many sources, including humans, animals and microorganisms such as bacteria or yeast. Biological products are manufactured through biotechnology, derived from natural sources or, in some cases, produced synthetically.
One of the approaches to generate green energy, which can be seen as having tremendous potential, is the use of microbes for the production of electricity. Microbial fuel cell (MFC) is a bioelectrical device that harness natural metabolism of microbes, to generate electrical power by oxidizing simple compounds like glucose or organic matter, leading to release of electrons. These electrons are combined with protons, which completes the circuit and produces current. Electricity is generated directly from a large variety of organic or inorganic compounds, using microbe as a catalyst [2, 3].
The idea of using microbes to produce electricity was conceived in 1911, by Michael Cresse Potter, who generated electricity from Saccharomyces cerevisiae, but the work went inattentive. Since then, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbial catalyzed anodic and cathodic electrochemical reactions. In 1931, Branet Cohen developed a batch of biological fuel cells that generated a current of approximately 2 mA, followed by Karube et al. catalyst investigations in the 60's and in the 80s-90s, with the work of Bennetto et al. on synthetic mediators, which resulted in the development of the so-called "analytical MFC" that is still in use to date. In the period from 2000 to 2010, developments in the physical design of MFCs have increased their appreciable power output from less than 0.1 mW/m2 to over 1000 mW/m2. [1, 14]
Most recently, researchers at Binghamton University in New York have developed the first micro-scale self-sustaining bacterial cell, generating power for 13 straight days through symbiotic interactions of two types of bacteria. In recent years, China has been playing an increasingly important role in this field, and has contributed considerably to moving MFCs forward toward large-scale implementations for both power generation and extended applications. Leading players in the market such as Cambrian Innovation Inc., Emefcy, MICROrganic Technologies, Inc., Microbial Robotics, ElectroChem, Prongineer, and Triqua International BV are focusing on research & development activities related to the scalable commercialization of MFCs. [4, 5, 6]
The future of MFCs is promising as it engenders green technology without CO2 emission. The Microbial Fuel Cell market is expected to reflect a positive growth trend in upcoming years. Geographically, North America is by far the largest market, whereas the Asia Pacific region, particularly the Middle East is expected to grow at the highest CAGR. As per the latest Market Research Report, Global market for microbial fuel cells is estimated to be worth USD 9.1 million and is expected to grow to USD 21.1 million by 2023 growing at a CAGR of 18.32% [7, 8]
Microbial electricity is a promising alternative energy source having various advantages. As MFC can be run in closed ambience, it can be useful at any region, independent of its climate. It provides continuous and constant power output as it didn't affect by the climate change. MFC requires smaller space and having simpler configuration, enabling it's mounting and transport from one place to another at ease in lesser time. MFC is able to produce power actively as long as microorganism are live and growing (no lag phase). Growth substrate for MFC microorganisms is widely available and cheap, which includes industrial or municipal waste water or effluent, agricultural waste, etc. MFC simultaneously treats waste and produces power making the process more cost effective. MFC having longer lifespan and demands lower maintenance.
Electricity generation is the prime application of MFCs. Scientists are attempting to create power stations generating electricity from humble bacteria, genetically modified or chemically engineered microorganism, for more efficient electricity-generating technology in the future. Their ability to extract bioelectricity, especially from pollutants in wastewater, renders MFCs a practically useful technology. Recently, MFCs are used as devices to produce electrical power for treatment of industrial, agricultural, and municipal wastewater. They are applicable to run low-power sensors that collect data from remote areas. Major advantage of using a microbial fuel cell in remote sensing rather than traditional battery is that bacteria reproduce, giving it significantly longer lifetime than traditional batteries. Thus, MFC may prove to be highly effective as compared to conventional batteries as they are environment friendly and do not require additional electricity to power them. Lebone Solutions, a startup based in Cambridge, MA, attempted to use microbial fuel cells to provide power to remote regions of Africa. Enough electricity can be created to power LED lights and mobile phones. According to Van Vuuren, about one square meter of fuel cell yields one watt, which could recharge a cell phone and five square meters can power a portable stereo, fan, or small light. [9, 11, 12]
Patent research and analytics of Biological is challenging and time-consuming because of
Searching involves, in general broad terms like "electricity", "generation" "microorganisms" which resulting in many off target results and hence producing difficulties in identifying the relevant results
We come across patents, where bioelectricity and generation terms are used in accordance to some other technology or a different aspect; Many results are produced where these terms are used in context to different technology such as medical technology, environmental technology, etc. For example:
Patents titled as "Process for producing antibiotics" and "Mosquito-repellent incense drying device and dust settling method" deal with "bioelectricity utilization", and not related to "bioelectricity generation".
Patents titled as "Antistatic and antibacterial plastics and preparation method" deal with preventing static electricity absorbing bacteria
Patents deal with Environmental technology showing electricity generation by microbes as a secondary alternative or bioelectricity is generated as a by product
Many patents deal with "bioelectricity measurement" rather than "bioelectricity generation"
Further challenging task is to search for a particular range of power produced (>25 W). The power production range which is restricted by a numerical value is very difficult because unit of power shows a lot a variation with different formats like W/m3, mW/m2, W, mW m-3, mW m-2, Watt, mW/m3 and difficult method for converting the power in a single unit format