Sustainable hydroponic production using solar energy and treated greywater within the water-energy-food-environment nexus

| Sustainable Hydroponics Production Data |

Abstract

Addressing the Water-Energy-Food-Environment (WEFE) nexus is critical for sustainable resource management. This study investigates a novel hydroponic system integrating photovoltaic (PV) solar energy and treated greywater (System-II), compared to a grid-powered system (System-I). Key performance indicators, including energy consumption, energy efficiency indices, and CO₂ emissions, are evaluated for the two systems. Additionally, the morphological, physiological, and biochemical parameters of lettuce are measured. System-II achieved superior energy performance, with an energy ratio of 0.11, energy productivity of 0.16 kg/MJ, and specific energy of 6.14 MJ/kg, compared to System-I’s 0.05, 0.07 kg/MJ, and 14.89 MJ/kg, respectively. Additionally, the water use efficiency values were 0.071 kg/L for System-I and 0.073 kg/L for System-II. Moreover, System-II reduced CO₂ emissions by over 94%, emitting only 0.0861 kg CO₂ eq/m²compared to 1.5386 kg CO₂ eq/m² from System-I. Morphological and physiological traits of lettuce irrigated with treated greywater remained optimal, showing a mean head weight of 682.9 g, head length and diameter of 17.7 cm and 18.3 cm, relative water content of 93.5%, 5.4% dry matter, and total chlorophyll content of 1.023 mg/g, comparable to those irrigated with tap water. This study highlights the potential of solar-powered hydroponics, utilizing treated greywater as a scalable and sustainable solution for efficient food production in alignment with WEFE nexus objectives. The findings provide insights into optimizing resource management in agricultural systems and contribute to the development of resilient, efficient, and sustainable food production systems in the face of global resource challenges.

Introduction

The interdependence of Water, Energy, Food, and Environment (WEFE) resources has become a central focus in addressing global sustainability challenges. These sectors are intricately linked, where interventions in one area often have significant impacts on the others¹. Agricultural activities significantly impact environmental sustainability through land use, greenhouse gas emissions, and water consumption^2,3. Innovative solutions that promote resource efficiency are crucial to ensuring food security, energy sustainability, water efficiency, and environmental protection^4,5. As population growth, urbanization, and climate change continue to intensify pressures on water, energy, food, and environmental systems, there is an urgent need for integrated and sustainable approaches to resource management. To meet the food requirements of a growing global population, global food production must increase by an estimated 60% by 2050. This intensifies pressure on natural resources, as agriculture currently accounts for approximately 70% of global freshwater withdrawals and nearly 30% of global energy consumption for food production and supply⁶. The pressures on water, energy, and food systems are further exacerbated by rapidly expanding populations and intensifying urbanization, placing additional stress on resource availability and ecosystem health ⁷.Moreover, the Commission on Sustainable Agriculture and Climate Change emphasizes the increasing correlation between population growth, rising food demand, and the need for sustainable intensification of food production⁸. Without integrated strategies that address the interconnectedness of water, energy, food, and the environment, efforts to achieve sustainability will remain fragmented and insufficient. Therefore, adopting a holistic WEFE Nexus approach is essential for ensuring the resilience and sustainability of these critical resource systems in the face of escalating global challenges.

Hydroponic farming is an advanced agricultural method that enhances water and space efficiency compared to conventional soil-based farming. It allows for precise control over nutrient and water delivery, reducing water wastage and increasing crop yields^9,10. Despite these advantages, hydroponic systems require a continuous energy supply to operate pumps, nutrient delivery systems, and climate control mechanisms¹¹. Therefore, ensuring the sustainability of these energy demands is critical for the long-term viability of hydroponic farming. On the other hand, renewable energy sources provide a sustainable alternative to conventional electricity derived from fossil fuels^12,13,14,15. PV technology plays a critical role in enhancing the sustainability of hydroponic systems. While hydroponics is inherently efficient in water and nutrient use, it remains energy-intensive due to its reliance on continuous power for pumps, nutrient delivery, artificial lighting, and climate control systems. Integrating solar energy into hydroponic operations addresses this challenge by reducing dependence on non-renewable energy sources^16,17,18. Therefore, solar-powered hydroponics has the potential to significantly lower the environmental footprint of controlled-environment agriculture while ensuring energy security in off-grid or resource-constrained areas¹⁹.

Greywater originates from kitchen and bathroom sinks, showers, and laundry, while blackwater contains urine, fecal matter, toilet paper, and toilet flushing water²⁰. Reclaimed greywater can be used for non-drinking applications like irrigation, toilet flushing, landscaping, and replenishing aquifers, helping to mitigate water supply and demand imbalances in a region²¹. Treated greywater contains essential nutrients that can support plant growth, thereby reducing the need for synthetic fertilizers²². Additionally, greywater reuse addresses global water scarcity issues by repurposing water that would otherwise be discarded. However, ensuring the safety and effectiveness of greywater for hydroponic applications requires rigorous treatment and monitoring processes²³. Moreover, the reuse of treated greywater hydroponic systems represents an innovative approach to conserving freshwater resources.

Despite the growing interest in sustainable agricultural practices, there is a notable knowledge gap in the comparative evaluation of hydroponic systems powered by PV solar energy versus those relying on conventional electricity, particularly when utilizing greywater as a primary water source. While hydroponics offers significant advantages in water and nutrient efficiency, the integration of renewable energy and unconventional water sources introduces complex dynamics that remain underexplored. A comprehensive understanding of the trade-offs and synergies between these systems is essential, especially in terms of performance, energy efficiency, crop yield, and environmental impacts²⁴. This study directly addresses the WEFE nexus by promoting an integrated approach to resource management. It explores the efficient use of treated greywater (Water), the application of renewable PV solar energy for powering agricultural systems (Energy), the enhancement of crop production through hydroponic techniques (Food), and the potential for reducing carbon emissions and freshwater withdrawals, thereby mitigating environmental impacts (Environment). The primary objective of this study is to conduct a comparative analysis of the performance and efficiency of hydroponic systems powered by PV solar energy and conventional electricity sources, with a specific focus on the utilization of greywater treated as an irrigation resource. The study aims to evaluate key factors such as energy consumption, water use efficiency, crop productivity, and the associated CO₂ emissions of these systems. The findings of this research contribute to the advancement of sustainable agriculture and resource-efficient management strategies, aligning with broader global sustainability goals. By demonstrating the feasibility and benefits of integrating renewable energy and greywater reuse in hydroponic food production, this study offers valuable insights to inform policy development and promote innovative practices that support the transition toward sustainable, resilient, and low-impact agricultural systems.

Read the FULL Original Study Here: https://www.nature.com/articles/s41598-025-16030-4