A Bioelectrochemical System for Waste Degradation and Energy Recovery From Industrial Coffee Wastewater

Abstract

The primary production of coffee involves the extensive use of water resources, since it is not only used for irrigation of coffee plantations, but it is also required in large volumes for the processing of the coffee berry to obtain high quality green beans. It is calculated that for every kg of dry coffee grain produced, up to 40 L of water are consumed, and its disposal represents a significant environmental problem, since most coffee growers are small producers with no access to efficient technologies for wastewater treatment. This situation leads to these liquid wastes to be discarded untreated in natural water sources, generating environmental pollution and public health problems. Bioelectrochemical Systems (BES) have been proposed as an alternative to conventional wastewater treatments, either as a primary bioremediation strategy or for secondary wastewater treatment systems. Among BES, microbial fuel cells (MFCs) are designed to exploit the metabolic capability of andophilic microorganisms to degrade the organic matter present in the waste. Anodophilic microorganisms use electrodes as terminal electron acceptors, generating a flow of electrons that can be used in the generation of electricity. In this work, we evaluated the ability of native microbial communities to degrade the organic matter present in wastewater from the coffee agroindustry and its electrogenic potential for the co-generation of electricity was evaluated using an MFC device developed by the authors. Wastewater samples obtained at different stages of the coffee wet process were used as inoculum and feedstocks. The system was operated in fed-batch, in both open and closed-circuit conditions, for 60 days. The degree of decontamination or bioremediation of the wastewater was assessed by measurements of physicochemical parameters. For the characterization of the native microbial community, microscopic and molecular techniques were used and the electrogenic potential was established by assessing the electrochemical performance of the system. With the proposed bioelectrochemical system, a reduction of up to 70% of the initial content of organic matter of the residual water from the coffee benefit was achieved, and open circuit voltages of up to 400 mV were recorded, comparable to those reported for conventional air breathing cathode MFC.

Determination of Electrogenic Potential and Removal of Organic Matter from Industrial Coffee Wastewater Using a Native Community in a Non-Conventional Microbial Fuel Cell

“…For example, within a native microbial community of a complex substrate, such as CWW, there could coexist a great diversity of prokaryotic and eukaryotic microorganisms responsible not only for producing usable energy but also for degrading the carbon sources and complex nutrients during different stages [63,64]. In previous studies [34,45,64] the presence of the genera Acetobacter sp., Bacillus sp., Clostridium sp., and Lactobacillus sp., among others, were associated with, in addition to an electrogenic potential, the anaerobic or fermentative metabolisms that produce the metabolic intermediates used by different electrogenic microorganisms as substrates.…”

“…In the experiment, two different wastewaters were used: WW from a fermentation stage (S1) and leachate from a coffee-pulping stage (S2). The inocula used were a mixed native microbial community (I1) obtained from a 1:1 mixture of both CWW substrates and a mature native microbial community (I2) [34] obtained from a previous experiment with non-conventional MFCs. To conserve the inocula, each sample was mixed with a proportion of 15% pure glycerol in 15 mL conical tubes and stored at −80 °C.…”

“…Experimental setup. The open-cathode MFC used in the experiment was fabricated with unconventional materials [34]. The chamber was fabricated with ABS polymeric material.…”

Outline of microbial fuel cells technology and their significant developments, challenges, and prospects of oxygen reduction electrocatalysts

“…Converting organic or inorganic waste materials into useful products and energy can better address energy and environmental problems (Babanova et al, 2022;Díaz-Vázquez et al, 2022;Gargalo et al, 2022;Kamali et al, 2023). Bioelectrochemical systems (BES) can be an effective potential candidate for the waste materials conversion and energy production (Agudelo-Escobar et al, 2022). BES is one of the emerging bioengineering technologies which show the process of electrochemical reactions, such as the conversion of chemical energy into electrical energy or vice versa, in the presence of microorganisms or biomaterials (Zheng et al, 2020).…”