There is currently considerable global attention on improving the livelihoods of smallholder farmers, particularly in developing countries, through the adoption of sustainable water and soil management practices. This focus stems from the challenges these farmers encounter, including unpredictable rainfall, inadequate irrigation infrastructure, and limited access to essential agricultural technical equipment. Among various technical tools, soil moisture sensors are pivotal as they provide farmers with information on soil moisture levels, thereby facilitating the efficient use of water. However, existing sensors are often costly, unsustainable, and challenging to use in off-grid regions where most of these farms are situated. This study aims to develop low-cost, biodegradable, off-grid soil moisture sensing systems (SMSSs) for smallholder farmers of developing countries. It seeks to address the hypothesis that soil moisture sensors can be directly powered by electricity generated from the soil through soil microbial fuel cell (SMFC) technology, utilizing the bacteria present in the soil, with current production being directly proportional to the soil moisture.

The development of low-cost, biodegradable, off-grid SMSSs using soil moisture sensors for smallholder farmers represents a significant advancement in sustainable agriculture. Integrating SMFC to power these sensors address multiple challenges simultaneously. It not only provides farmers with crucial soil moisture data but also eliminates the need for external power sources, making it particularly suitable for remote and off-grid locations. It also provides uninterrupted power supply as it uses naturally available bacteria from soil. The biodegradable nature of these sensors aligns with environmental sustainability goals, reducing electronic waste and minimizing the ecological footprint of agricultural practices. Furthermore, it has the potential to revolutionize water management practices in smallholder farming. By providing soil moisture data, farmers can make informed decisions about irrigation, optimizing water usage and potentially increasing crop yields. This technology could improve water use efficiency, also the low-cost nature of these sensors makes it accessible to a broader range of farmers, potentially democratizing access to advanced agricultural technologies in developing regions......

Biodegradable membranes are crucial for environmental applications, offering sustainable and low-impact solutions. These membranes play a vital role in biodegradable batteries by separating the anode and cathode while facilitating proton movement. The aim of this study is to develop a biodegradable membrane using biodegradable polymers such as chitosan (CS) and polyvinyl alcohol (PVA), reinforced with filter paper. In this research, a cost effective, biodegradable membranes using CS, PVA, and a 1:1 CS/PVA composite through solution-casting method were synthesized. The membranes were reinforced with cellulose filter paper and coated with water-resistant graphene conductive ink. Performance metrics, including swelling ratios, water uptake, ion exchange capacity, oxygen diffusion, proton conductivity, and degradation in compost tea, were evaluated. Uncoated CS membrane exhibited the highest water uptake (94.10%), while uncoated PVA membrane demonstrated the highest swelling ratio (150%) and ion exchange capacity (3.94 meq/g). Coated CS/PVA membrane showed the lowest oxygen diffusion coefficient (0.058 × 10−5 cm2/s) and the highest proton conductivity (1.74 mS/cm). All membranes exhibited slow degradation over 100 days. The findings of this research have significant implications beyond the laboratory, presenting a biodegradable, cost-effective, and environmentally sustainable alternative to conventional membranes. These membranes can be utilized in the construction of biobatteries, which, in turn, can be employed to power low-cost devices.

The removal of nitrate (NO3−) from water and its subsequent valorization for various applications are crucial due to environmental, health, and economic considerations. A promising method for its removal is the process of electrocatalytic reduction of nitrate. Copper/nickel (Cu/Ni) composite electrodes have demonstrated potential for this process in aqueous solution, however, the effect of thin Cu film coated on Ni using physical vapor deposition (PVD) has not been investigated for NO3− removal. Here, the PVD technique was employed to deposit a thin film of Cu onto a Ni plate to form Cu-Ni composite electrodes of varying Cu thicknesses (25–100 nm), enabling the investigation of the influence of the Cu film thickness on NO3− reduction. Electrodes prepared using PVD were utilized for electrocatalytic nitrate reduction (NO3RR) for the first time. The Cu-Ni electrodes were analyzed using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to examine the deposited Cu film which is critical for NO3− reduction and ammonium (NH4+) selectivity. The Cu film was found to be uniformly distributed on the Ni plate without any additional contamination. Cyclic voltammetry was performed to obtain the information on electron transfer between the Cu-Ni electrode and the nitrogen (N2) species on the surface. NO3− was primarily reduced to NH4+, with no significant difference in the NO3− conversion rate observed as a function of the Cu thickness. As the Cu thickness increased, the current density decreased. This study also investigated the effect of stirring on NO3− reduction, considering potential applications where rotation or stirring is not feasible such as in some batteries. The findings of this investigation indicate that thin film coated electrodes fabricated using the PVD method exhibit capability for NO3− elimination through electrocatalytic reduction processes.

Soil moisture monitoring is essential for a variety of applications including agriculture, forestry, and environmental monitoring. However, soil moisture sensors may be expensive and require batteries or other energy sources, making them unsuitable for remote or off-grid locations and farmers. Improper e-waste management of short-lived sensing components can reveal the contradictions of solutions aimed at environmental sustainability, which also degrade environmental health. Therefore, the development of low-cost, off-grid, biodegradable in-situ soil moisture sensing system (SMSS) is necessary for these regions. This article provides an overview of the current state-of-the-art in low-cost, off-grid, and biodegradable in-situ soil moisture sensing. It highlights low-cost SMSS components including hardware (microcontrollers and communication modules), software, and off-grid ambient energy sources. It also highlights the current research in biodegradable polymers used for moisture sensing. The challenges in combining low-cost, off-grid, and biodegradable soil moisture sensing are identified as a research gap. Finally, the underlining question of the “perfect” choice of SMSS is explored based on the trade-offs of performance, operational feasibility, and the newly proposed aspect of biodegradability, consequently suggesting context-specific decisions by consciously managing these tradeoffs.

This paper shares an early-career perspective on potential themes for the upcoming International Association of Hydrological Sciences (IAHS) Scientific Decade (SD). This opinion paper synthesizes six discussion sessions in western Europe identifying three themes that all offer a different perspective on the hydrological threats the world faces and could serve to direct the broader hydrological community: “Tipping points and thresholds in hydrology,” “Intensification of the water cycle,” and “Water services under pressure.” Additionally, four trends were distinguished concerning the way in which hydrological research is conducted: big data, bridging science and practice, open science, and inter- and multidisciplinarity. These themes and trends will provide valuable input for future discussions on the theme for the next IAHS SD. We encourage other early-career scientists to voice their opinion by organizing their own discussion sessions and commenting on this paper to make this initiative grow from a regional initiative to a global movement.