Plant microbial fuel cell in paddy field : A power source for rural area

As an energy carrier, electricity access is one of important aspect for human development. There is a positive correlation between electricity consumption per capita and human development index (HDI) and also gross domestic product (GDP). However, the world electrification is not equally distributed. Most of those who do not have electricity access live in rural areas and located in developing countries. In these area, some people use polluted kerosene lamps as their light source or expensive gasoline generator as their electricity source. Other than that, battery is also widely used as a power source. In addition to the unequal electrification, the world electricity generation is still dominated by fossil fuel sources that have a negative impact on the environment, increased health risk and global climate change. Therefore, it is important to shift from conventional energy source to low-carbon renewable electricity sources. This thesis “Plant Microbial Fuel Cell in Paddy Field: a power source for rural area“ aims to assess the applicability of the plant microbial fuel cell (Plant-MFC) as a low power off-grid power source in a rural area for a theoretical Indonesian case. To achieve this, a technical design was made for a household in rural area of Indonesia based on the latest research developments. Then, the applicability was assessed on technical, social, and environmental safety and health criteria as well as economics and some scenarios were suggested which could improve the real application. Values for a plant-MFC system to fulfil basic electricity needs were calculated. The main highlights and findings on this work are summarized in accordance with the chapters outlined in this thesis as following. Chapter 2 “Marine Sediment Mixed with Activated Carbon Allows Electricity Production and Storage from Internal and External Energy Sources: A New Rechargeable Bio-Battery with Bi-Directional Electron Transfer Properties” investigates the abilities of marine sediment and activated carbon to store and generate electricity in a bio-battery. In this work, several mixture of marine sediment and activated carbon were studied in a bio electrochemical system (BES). When operated in the MFC mode, the system generated electricity with solely marine sediment as the anode electron donor, resulted in the creation of a bio-battery. The results show that by usage of marine sediment and activated carbon (AC) electricity was generated and stored. The internal electrical storage density is 0.3 mWh/kg AC marine anode. These insights give opportunities to apply such BES systems as e.g. ex-situ bio-battery to store and use electricity for off-grid purpose in remote areas. Chapter 3 “Activated Carbon Mixed with Marine Sediment is Suitable as Bioanode Material for Spartina anglica Sediment/Plant Microbial Fuel Cell: Plant Growth, Electricity Generation, and Spatial Microbial Community Diversity” aims to investigate the suitability of a mixture of activated carbon and marine sediment as a bioanode in a plant-MFC system with Spartina anglica. This work focused on study how different mixtures of the activated carbon (AC) and the marine sediment (MS) as an anode material affected the plant vitality, electricity generation and spatial microbial community. Results show that Spartina anglica grew in all of the plant-MFCs, although the growth was less fertile in the 100% activated carbon Plant-MFC. On long-term (2 weeks) performance, mixture of 33% and 67% marine sediment outperformed other Plant-MFCs in terms of current density (16.1 mA/m2 plant growth area) and power density (1.04 mW/m2 plant growth area). Results also show a high diversity of microbial communities dominated by Proteobacteria and indicates that the bacterial communities were affected by the anode composition. These findings show that the mixture of activated carbon and marine sediment are suitable material for bioanodes and could be useful for the application of Plant-MFC in a real wetland. Chapter 4 “Performance and Long Distance Data Acquisition via LoRa Technology of a Tubular Plant Microbial Fuel Cell Located in a Paddy Field in West Kalimantan, Indonesia” provide an insight about the field performance of tubular Plant-MFC. In this study, one-meter tubular Plant-MFC with graphite felt anode and cathode were installed in triplicates in a paddy field for four rice growth seasons. An online data acquisition using LoRa technology was developed to investigate the performance of the tubular Plant-MFC over the final whole rice paddy growing season. The result revealed that the Plant-MFC do not negatively affect the rice growth. A continuous electricity generation was achieved during a wet period in the crop season. On average the Plant-MFC generated power of 6.6 mW/m2 plant growth area (0.4mW per meter tube). The Plant-MFC also shows a potential to be used as a bio sensor, e.g. rain event indicator, during a dry period between the crop seasons. Chapter 5 “A Thin Layer of Activated Carbon Deposited on Polyurethane Cube Leads to New Conductive Bioanode for (Plant) Microbial Fuel Cell” exploits the potential of electrochemically active self-assembled biofilms to fabricate three-dimensional bio electrodes for of (plant) microbial fuel cells with minimum use of electrode materials. For this purpose, polyurethane foams coated with activated carbon was prepared and studied as platform bio anodes for harvesting electric current in lab microbial fuel cells (MFCs) and field Plant-MFCs. Results show that electric conductivity of the PU/AC electrode enhance over time during bioanode development. The maximum current and power density of an acetate fed MFC reached 3mA/m2 projected surface area of anode compartment and 22mW/m3 anode compartment. The field test of the Plant-MFC reached a maximum performance of 0.9 mW/m2 plant growth area at a current density of 5.6 mA/ m2 PGA. A rice paddy field test showed that the PU/AC electrode was suitable as anode material in combination with a graphite felt cathode. Finally, the main findings of this thesis are summarized and discussed in Chapter 6, “General Discussion”. In this chapter, a theoretical available power for Plant-MFC system from a paddy field is presented to give an insight how far performance of current Plant-MFC meets theoretical understanding. Based on the experimental results, this chapter answers the thesis goal to discuss the applicability of the Plant-MFC as an off-grid power source in a rural area by assessing its technical, economic, social, and environmental safety and health criteria. Finally, an outlook for future Plant-MFC application is provided.