Applications of Emerging Bioelectrochemical Technologies in Agricultural Systems: A Current Review

Development of Plumeria alba extract supplemented biodegradable films containing chitosan and cellulose derived from bagasse and corn cob waste for antimicrobial food packaging

With the increase in global plastic pollution due to conventional plastic packaging (petroleum-derived), bioplastics have emerged as an alternative green source for practising a circular economy. This research aimed to extract cellulose from bagasse and corn cob waste and utilized in mixed form to prepare bioplastic film. The mixed cellulose was further reinforced with natural substances such as chitosan, bentonite, and P. alba extract. These newly developed bioplastics films were characterized by various physical tests like film thickness, moisture content, water solubility and spectroscopic techniques such as Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive spectroscopic (SEM-EDX), thermal gravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectroscopy for opacity testing. The results revealed the enhanced bioplastic thermal and mechanical characteristics through robust interactions between cellulose and bentonite molecules. Moreover, incorporating chitosan solution as reinforcements in bio-composite films resulted in improved water barrier properties. The results indicated lower absorption in the UV range of 250-400 nm, attributed to the absence of UV-absorbing groups. Finally, their biodegradability was tested in soil, and 85.3 % weight loss of bioplastic films was observed after 50 days of the experiment which is the main task of this research. The antimicrobial properties of bioplastic films have been evaluated, and showed an inhibition zone of 16 mm against E. coli. After 12 days of incubation of sherbet berries, complete spoilage is identified in the control group compared to those covered with the bioplastic film. This outcome is attributed to the antioxidant and antimicrobial activities provided by chitosan and P. alba extract in the bioplastic film. The comprehensive outcomes of this study suggest the potential future adoption of these entirely bio-derived, environmentally sustainable and biodegradable bioplastic films as a viable substitute for the plastic packaging currently present in the market.

Bioenergy production from chicken feather waste by anaerobic digestion and bioelectrochemical systems

BACKGROUND

Poultry feather waste has a potential for bioenergy production because of its high protein content. This research explored the use of chicken feather hydrolysate for methane and hydrogen production via anaerobic digestion and bioelectrochemical systems, respectively. Solid state fermentation of chicken waste was conducted using a recombinant strain of Bacillus subtilis DB100 (p5.2).

RESULTS

In the anaerobic digestion, feather hydrolysate produced maximally 0.67 Nm3 CH4/kg feathers and 0.85 mmol H2/day.L concomitant to COD removal of 86% and 93%, respectively. The bioelectrochemical systems used were microbial fuel and electrolysis cells. In the first using a microbial fuel cell, feather hydrolysate produced electricity with a maximum cell potential of 375 mV and a current of 0.52 mA. In the microbial electrolysis cell, the hydrolysate enhanced the hydrogen production rate to 7.5 mmol/day.L, with a current density of 11.5 A/m2 and a power density of 9.26 W/m2.

CONCLUSIONS

The data indicated that the sustainable utilization of keratin hydrolysate to produce electricity and biohydrogen via bioelectrical chemical systems is feasible. Keratin hydrolysate can produce electricity and biofuels through an integrated aerobic-anaerobic fermentation system.

Nanocellulose/wood ash-reinforced starch-chitosan hydrogel composites for soil conditioning and their impact on pea plant growth

Hydrogels are 3-dimensional polymer networks capable of absorbing a large amount of water. Natural polymeric hydrogels are biodegradable, non-toxic and biocompatible. They can effectively retain nutrients for the plant and can be used as soil conditioners. This study uses a chemical cross-linking technique to synthesize starch and chitosan-based hydrogel using citric acid as a cross-linker. Additionally, hydrogel composites were developed by incorporating wood ash, nano-cellulose, and NPK (nitrogen-phosphorus-potassium) fertilizer as fillers to enhance their properties. The formulated hydrogel/hydrogel composite samples were characterized by FTIR spectroscopy, SEM analysis, X-ray diffraction and thermo-gravimetric analysis. The experiment results showed the chemical cross-linking among the polymeric chain and the semi-crystalline nature of the hydrogel/hydrogel composite samples. The swelling capacity of the hydrogel/hydrogel composite samples was 200-420% (in distilled water) and 104-220% (in saline medium) and demonstrated biodegradability within 110 days. The NPK reinforced hydrogel composite showed an excellent effect on the growth of pea plants (leaves count = 37, stem height = 20.2 cm), and could be effectively used as soil conditioners for agricultural applications. Considering the ability of hydrogel composites to reduce irrigation needs, enhance nutrient retention, and improve crop production, these novel hydrogel composites present an economically viable solution for sustainable agricultural practices.

Bioelectrochemical systems (BESs) for agro-food waste and wastewater treatment, and sustainable bioenergy-A review

Producing food by farming and subsequent food manufacturing are central to the world's food supply, accounting for more than half of all production. Production is, however, closely related to the creation of large amounts of organic wastes or byproducts (agro-food waste or wastewater) that negatively impact the environment and the climate. Global climate change mitigation is an urgent need that necessitates sustainable development. For that purpose, proper agro-food waste and wastewater management are essential, not only for waste reduction but also for resource optimization. To achieve sustainability in food production, biotechnology is considered as key factor since its continuous development and broad implementation will potentially benefit ecosystems by turning polluting waste into biodegradable materials; this will become more feasible and common as environmentally friendly industrial processes improve. Bioelectrochemical systems are a revitalized, promising biotechnology integrating microorganisms (or enzymes) with multifaceted applications. The technology can efficiently reduce waste and wastewater while recovering energy and chemicals, taking advantage of their biological elements' specific redox processes. In this review, a consolidated description of agro-food waste and wastewater and its remediation possibilities, using different bioelectrochemical-based systems is presented and discussed together with a critical view of the current and future potential applications.

Environmental assessment of the production of itaconic acid from wheat straw under a biorefinery approach

This study performs the environmental assessment of itaconic acid (IA) production from wheat straw. The Life Cycle Assessment (LCA) methodology is used to determine the environmental hotspots, considering impact categories such as Global Warming (GW), Fossil Resource Scarcity (FRS), Water Consumption (WC), among others. A sensitivity analysis was performed considering an optimization of the steam explosion process and 100% renewable energy. Results report an impact of about 14.33 kg CO₂ eq in GW, 4.15 kg of oil eq in FRS, for each kg of IA produced for the baseline scenario. Moreover, the pretreatment and fermentation stages constitute hotspots of the IA production. In addition, using a renewable energy source in production would reduce the impact by 82% in GW, 71% in PM and 82% in FRS categories. The optimization of the steam explosion process presents a better performance in GW and FRS but also lies in an increase in WC.

Waste Materials as a Resource for Production of CMC Superabsorbent Hydrogel for Sustainable Agriculture

Waste materials are receiving more attention as concerns about the future of our planet increase. Cellulose is the most common substance in agricultural waste. Agricultural wastes containing cellulose are misplaced resources that could be reused in various fields for both environmental and economic benefits. In this work, 32 different kinds of waste are investigated for chemical modification in order to obtain carboxymethyl cellulose for the production of a superabsorbent hydrogel that can be applied in agriculture. A brief literature review is provided to help researchers wishing to obtain carboxymethyl cellulose by carboxymethylation starting with waste materials. We also provide details about methods to obtain as well as verify carboxymethylation. Carboxymethyl cellulose (CMC), as a constituent of cellulosic water and superabsorbent hydrogels with applications in agriculture, is described. Superabsorbent hydrogels with CMC are able to absorb huge amounts of water and are biodegradable.

SMFC as a tool for the removal of hydrocarbons and metals in the marine environment: a concise research update

Marine pollution is becoming more and more serious, especially in coastal areas. Because of the sequestration and consequent accumulation of pollutants in sediments (mainly organic compounds and heavy metals), marine environment restoration cannot exempt from effective remediation of sediments themselves. It has been well proven that, after entering into the seawater, these pollutants are biotransformed into their metabolites, which may be more toxic than their parent molecules. Based on their bioavailability and toxic nature, these compounds may accumulate into the living cells of marine organisms. Pollutants bioaccumulation and biomagnification along the marine food chain lead to seafood contamination and human health hazards. Nowadays, different technologies are available for sediment remediation, such as physicochemical, biological, and bioelectrochemical processes. This paper gives an overview of the most recent techniques for marine sediment remediation while presenting sediment-based microbial fuel cells (SMFCs). We discuss the issues, the progress, and future perspectives of SMFC application to the removal of hydrocarbons and metals in the marine environment with concurrent energy production. We give an insight into the possible mechanisms leading to sediment remediation, SMFC energy balance, and future exploitation.

Biogas Upgrading and Ammonia Recovery from Livestock Manure Digestates in a Combined Electromethanogenic Biocathode—Hydrophobic Membrane System

Anaerobic digestion process can be improved in combination with bioelectrochemical systems in order to recover energy and resources from digestates. An electromethanogenic microbial electrolysis cell (MEC) coupled to an ammonia recovery system based on hydrophobic membranes (ARS-HM) has been developed in order to recover ammonia, reduce organic matter content and upgrade biogas from digested pig slurry. A lab-scale dual-chamber MEC was equipped with a cation exchange membrane (CEM) and ARS with a hydrophobic membrane in the catholyte recirculation loop, to promote ammonia migration and absorption in an acidic solution. On the other hand, an electromethanogenic biofilm was developed in the biocathode to promote the transformation of CO2 into methane. The average nitrogen transference through the CEM was of 0.36 gN m−2 h−1 with a removal efficiency of 31%, with the ARS-HM in the catholyte recirculation loop. The removal of ammonia from the cathode compartment helped to maintain a lower pH value for the electromethanogenic biomass (7.69 with the ARS-HM, against 8.88 without ARS-HM) and boosted methane production from 50 L m−3 d−1 to 73 L m−3 d−1. Results have shown that the integration of an electromethanogenic MEC with an ARS-HM allows for the concomitant recovery of energy and ammonia from high strength wastewater digestates.

Convenient non-invasive electrochemical techniques to monitor microbial processes: current state and perspectives

Real-time electrochemical monitoring in bioprocesses is an improvement over existing systems because it is versatile and provides more information to the user than periodic measurements of cell density or metabolic activity. Real-time electrochemical monitoring provides the ability to monitor the physiological status of actively growing cells related to electron transfer activity and potential changes in the proton gradient of the cells. Voltammetric and amperometric techniques offer opportunities to monitor electron transfer reactions when electrogenic microbes are used in microbial fuel cells or bioelectrochemical synthesis. Impedance techniques provide the ability to monitor the physiological status of a wide range of microorganisms in conventional bioprocesses. Impedance techniques involve scanning a range of frequencies to define physiological activity in terms of equivalent electrical circuits, thereby enabling the use of computer modeling to evaluate specific growth parameters. Electrochemical monitoring of microbial activity has applications throughout the biotechnology industry for generating real-time data and offers the potential for automated process controls for specific bioprocesses.

Enhancing Stability of Microalgae Biocathode by a Partially Submerged Carbon Cloth Electrode for Bioenergy Production from Wastewater

The electricity output from microbial fuel cell (MFC) with a microalgae assisted cathode is usually higher than that with an air cathode. The output of electricity from a photosynthetic microalgae MFC was positively correlated with the dissolved oxygen (DO) level in the microalgae assisted biocathode. However, DO is highly affected by the photosynthesis of microalgae, leading to the low stability in the electricity output that easily varies with the change in microalgae growth. In this study, to improve the electricity output stability of the MFC, a partially submerged carbon cloth cathode electrode was first investigated to use oxygen from both microalgae and air, with synthetic piggery wastewater used as the anolyte and anaerobically digested swine wastewater as the catholyte. When the DO levels dropped from 13.6–14.8 to 1.0–1.6 mg/L, the working voltages in the MFCs with partially submerged electrodes remained high (256–239 mV), whereas that for the conventional completely submerged electrodes dropped from 259 to 102 mV. The working voltages (average, 297 ± 26 mV) of the MFCs with the 50% submerged electrodes were significantly (p < 0.05) higher than with other partially or completely submerged electrodes. The associated maximum lipid production from wastewater was 250 ± 42 mg/L with lipid content of 41 ± 6% dry biomass. Although the partially submerged electrode had no significant effects on lipid production or nitrogen removal in wastewater, there was significant improvement in the stability of the electricity generated under variable conditions.