eLatrine: Lessons Learned from the Development of a Low-Tech MFC Based on Cardboard Electrodes for the Treatment of Human Feces

Abstract

The aim of the study was to provide experimental proof-of-concept that stand-alone power generation based on microbial fuel cells (MFCs) operated using human feces as the substrate can be achieved. A pit latrine that is typically employed for decentralized treatment of human feces e.g. in regions without access to centralized wastewater infrastructures was installed as sampling site. It was the philosophy that the components, i.e. anodes and cathodes, used in the MFCs had to be based on low-cost precursors. This was achieved by recycling common household materials or waste products and a low-tech/cost production method was developed to convert them into usable electrodes. It is demonstrated that i) pre-tests on using an equivalent to vent-air from ovens or fire-places allowed a low-tech carbonization of e.g. corrugated cardboard to electrode materials; ii) that anodes based on corrugated cardboard can be operated using real human feces as substrate, nevertheless, providing only low current densities (15.09 ± 5.18 μA cm −2 ) and iii) cathodes -with nitrogen functionalities derived from (artificial) urine -based on corrugated cardboard or as an alternative jeans cloth show a good oxygen reduction reaction (ORR) activity. Introducing nitrogen containing surface moieties to the cathode surface increased the ORR up to factor 5 (chronoamperometry at 0 V vs. Ag/AgCl sat. KCl) compared to the untreated reference. Most importantly, highly valuable lessons for exploiting real and highly heterogeneous and dense substrates like human feces in microbial electrochemical technologies were learned. In 2015 the United Nations proposed the 17 Sustainable Development Goals to be achieved by 2030.1 Among these are for instance "Good health and well-being", "Clean water and sanitation", "Affordable and clean energy" as well as "Sustainable cities and communities". Hence, sanitation and concurrently treat of waste is a key challenge, as it covers technical as well as socio-economic and health related issues.2,3 Wastewater treatment facilities and related infrastructure, e.g. as typically installed in the USA or Europe, can be a significant sink for energy and resources, 4-6 which are needed for construction, maintenance, especially of the sewer system, and operation. 7At the same time an estimated 2.4 billion people, or approx. 33 % of the world population, do not have access to such infrastructure. For this share of the world's population using simple solutions such as pit latrines can already be advantageous in terms of hygiene and security when compared to open defecation.2,3 Therefore decentralized sanitation systems seem advantageous in developing regions with no or only very little existing infrastructure.Waste and wastewaters have gradually become perceived not as sinks of chemicals and energy but as re-sources thereof. In this light microbial electrochemical technologies (MET) 8 and especially microbial fuel cells (MFCs) are considered to be a highly promising solution.6 MFCs are primary microbial electrochemical technologies...

Microbial fuel cells: From fundamentals to applications. A review

“…The obtained carbonized carboard is then attached onto a rigid support. The material is very low-cost, has high electrical conductivity and high porosity [191] , [228] , [267] .…”

Integrating Human Waste with Microbial Fuel Cells to Elevate the Production of Bioelectricity

“…Disposing of human excreta by MFCs may cleanse toilet waste and recover electrical power [ 65 ]. Kretzschmar et al constructed an eLatrine MFC with low-cost corrugated cardboard as an electrode material and human feces as a substrate during anodic oxidation to capture potential energy from human waste [ 23 ]. Perlow’s first investigation on MFC waste treatment by microbial oxidation produced a low open-circuit voltage of 200 mV [ 66 ].…”

“…Cardboard electrodes help in developing a low-cost MFC. The MFC yields power output of 15.09 ± 5.18 μA cm −2 [ 23 ]. In Ghana, Castro et al (2014) created an MFC that was used to handle organic matter removal.…”

Recent advancements in real-world microbial fuel cell applications

“…Most of the core parts and components can be bespoke and therefore expensive, even at prototype level, and there is a scientific challenge in identifying alternatives that would (i) perform equally well and for prolonged periods but most importantly (ii) be inexpensive and widely available. One of the avenues researchers have explored are the alternative low cost materials including ceramic [53,54] or cardboard 55., 56. and plant derived electrodes [57]. As reported by Ge and He in long term operation of their pilot study in wastewater treatment plant, over 60% of the material cost of the MFCs was due to the cation exchange membrane [40] therefore inexpensive separators such as ceramics are a valid alternative for this technology.…”