Optimizing water-energy-food nexus: achieving economic prosperity and environmental sustainability in agriculture

The increasing global population, rapid urbanization, and climate change are putting unprecedented pressure on limited water and energy resources for food production. It requires integrated management of the key resources to achieve economic and environmental sustainability. The water-energy-food (WEF) nexus, in conjunction with circular bioeconomy (CBE) principles, offer a promising approach to achieve sustainable agriculture. It provides the integration between interconnectedness and interdependencies of the resources through closing bio-resource loops. Using bio-based materials, renewable energy resources


Introduction
Agriculture, as a major consumer of water and energy resources, significantly impacts the environment through land use change, greenhouse gas emissions, and biodiversity loss (Lynch et al., 2021).With the global population surpassing 8 billion people, the limited resources for food production, coupled with the need for food security, pose unprecedented pressure on water and 10. 3389/fsufs.2023.1207197Frontiers in Sustainable Food Systems 02 frontiersin.orgenergy supplies (Li et al., 2021).This necessitates integration and a holistic perspective to achieve sustainable outcomes and balance the food supply and demand.The water-energy-food (WEF) nexus approach has gained global attention and led to international and regional agreements emphasizing the interconnectedness and interdependence of these critical elements (Geressu et al., 2020;Yue and Guo, 2021).It highlights three critical elements for ensuring food security, reducing poverty, improving human health, and protecting the environment, and those effective solutions must be based on a thorough understanding of the interdependencies and feedback between these systems (Geressu et al., 2020;Siderius et al., 2022).This concept also recognizes that these elements are not separate entities but are profoundly interconnected, and those changes in one element can significantly impact the others.
The nexus approach, encompassing resource systems, resource management, and drivers of change, can be strengthened by integrating circular economy (CE) considerations, particularly in the context of the bioeconomy (BE), which utilizes biological resources and processes to produce goods, services, and energy sustainably, aligning with the principles of circularity (Hetemäki et al., 2017;Braun et al., 2022).Within the bioeconomy framework, the term "circular bioeconomy" has emerged to describe an economic system that combines CE principles with utilizing biological resources.The circular bioeconomy (CBE) − manifesting the intersection between CE and BE− aspires to create a sustainable and regenerative system that maximizes the value derived from biological resources, such as biomass and organic waste, as inputs, while minimizing waste and negative environmental impacts within a closed-loop system (Tan and Lamers, 2021;Kumar Sarangi et al., 2023).While the CE is a broader concept that encompasses all sectors and resources, the CBE narrows its focus to the sustainable utilization of biological resources and processes to achieve circularity and sustainability.
The WEF nexus and CBE are interconnected concepts that address the sustainable management of resources (Biggs et al., 2015;Tan and Lamers, 2021;Peña-Torres et al., 2022).The WEF nexus recognizes the interdependencies and trade-offs between water, energy, food, and ecosystems (Wu et al., 2021;Yue and Guo, 2021).It emphasizes the need for an integrated approach to manage these resources, considering their interconnectedness and the potential impacts of decisions made in one sector on others.The CBE, on the other hand, focuses on utilizing bio-based resources and processes in a sustainable and regenerative manner (Stegmann et al., 2020;Tan and Lamers, 2021).It aims to replace the linear take-make-dispose model with a circular approach that maximizes resource efficiency, reduces waste, and minimizes adverse environmental impacts.The CBE can contribute to the goals of the WEF nexus by promoting resource efficiency and reducing the strain on water, energy, and food systems (Tan and Lamers, 2021;Peña-Torres et al., 2022).This concept revolutionizes the traditional economic principle that solely emphasizes extraction, production, and disposal, which is inherently unsustainable in the long term.This transformative concept decouples economic growth from resource depletion and environmental degradation, fostering a more sustainable and resilient future for current and future generations (Stegmann et al., 2020;Khan et al., 2021).
By adopting circular practices in the bioeconomy within WEF, such as the utilization of renewable biomass, organic waste, and byproducts, significant benefits can be achieved regarding resource efficiency, economic prosperity, and environmental sustainability.These practices minimize the need for excessive resource inputs, decrease waste generation, and mitigate environmental pollution.In turn, the principles of the WEF nexus can guide decision-making within the CBE by considering the impacts and trade-offs among water, energy, food, and ecosystems; it helps ensure that the CBE's practices align with broader sustainability objectives, such as water and energy conservation, food security, and ecosystem preservation (Stegmann et al., 2020;Tan and Lamers, 2021;Yue and Guo, 2021).Therefore, this perspective aims to explore the potential of synergies between the WEF nexus approach with CBE principles, with the overarching goal of fostering economic prosperity and environmental sustainability in agriculture.Ultimately, the goal of this perspective is to contribute to a more sustainable and resilient agricultural system that can meet the population's food, energy, and water needs while protecting the environment and promoting economic growth.

WEF nexus with CBE
Incorporating CBE into the WEF nexus (WEF-CBE) holds significant potential for addressing the intricate interconnections among these crucial sectors.Adopting CBE into WEF can enhance resource-use efficiency, facilitate effective waste management, and ensure long-term value preservation within this nexus.The CBE's holistic approach, combining concepts such as feedback systems, "cradle-to-cradle" principles, and closed-loop systems, enables us to create a more sustainable and resilient system (Khan et al., 2021;Tan and Lamers, 2021;Ncube et al., 2022).Treating and converting waste into bio-based materials and keeping products and materials in use for as long as possible can create a robust framework for promoting economic and environmental sustainability and lead to synergism among components (Wu et al., 2021;Kumar Sarangi et al., 2023).This integration meets the growing demand for bio-based materials in agriculture (MacArthur, 2013), as they are perceived to offer safer and more sustainable alternatives compared to synthetic products.
WEF-CBE offers various opportunities for sustainable resource management (Figure 1).For example, using wastewater from food production for irrigation can reduce the demand for freshwater resources, leading to more sustainable water use (Ansari et al., 2019;Geressu et al., 2020;Yue and Guo, 2021).On the one hand, a CBE principle to water management could involve using natural ecosystems, such as wetlands or riparian buffers, to filter and store water, which can help to reduce the need for expensive and energy-intensive water treatment systems (Geressu et al., 2020;Nepal et al., 2021).On the other hand, it can involve using water-efficient crops such as drought-tolerant varieties to reduce the water requirements for irrigation and using water-efficient technologies such as drip irrigation to reduce water loss and increase irrigation efficiency.Moreover, innovative technologies such as membrane filtration and reverse osmosis can help recover valuable resources (e.g., nutrients and energy) from wastewater.
In terms of nutrient management, bio-based materials (Giampietro, 2019;Jain et al., 2022;Mukhtar et al., 2023), such as biofertilizers, produced from agricultural waste and organic sources, have emerged as a promising alternative to synthetic fertilizers, providing a range of benefits for both crops and the environment (Figure 1).It can promote soil health and fertility without the negative environmental impacts associated with synthetic fertilizers, such as soil acidification, nutrient leaching, and water pollution.Moreover, biofertilizers can improve soil structure, promote beneficial microbial 10.3389/fsufs.2023.1207197 Frontiers in Sustainable Food Systems 03 frontiersin.orgactivity, and reduce the risk of nutrient runoff (Giampietro, 2019;Yue and Guo, 2021;Peña-Torres et al., 2022).In addition to bio-based materials products, a range of other bio-based materials can be used to support sustainable agriculture practices, such as biopesticides and biochar.Biopesticides, a compound derived from natural sources such as plants or microbes, can be used to control pests and diseases, while biochar, a type of charcoal produced from organic waste material such as crop residues and animal manure, can be used to improve water retention and carbon sequestration (Jain et al., 2022;Osman et al., 2022).Furthermore, the application of bio-based materials can contribute to reduce GHG emissions and mitigate climate change impacts through potential carbon sequestration and reducing soil and water pollution (Lin et al., 2022b;Mukhtar et al., 2023).The energy component of the WEF nexus plays a vital role in promoting sustainable agriculture, as it is required for power machinery, transport goods, and process products.The energy demand is expected to rise significantly due to increasing population, urbanization, industrialization, and climate change (van Ruijven et al., 2019;Ahmad and Zhang, 2020).However, the conventional energy used in agriculture contributes to GHG emissions, climate change, and other environmental problems.Agriculture is responsible for approximately ~21-37% of global GHG emissions annually, including methane (CH 4 ), nitrous oxide (N 2 O), and carbon dioxide (CO 2 ), with energy use accounting for a significant portion of these emissions (Mbow et al., 2019;Lin et al., 2022a).Therefore, to promote sustainable agriculture, it is essential to develop renewable energies and implement energy-efficient practices and technologies.For example, using renewable energies from solar, wind, and hydropower can reduce dependence on fossil fuels to meet the energy needs of agricultural operations and decrease GHG due to its eco-friendlier energies (Payet-Burin et al., 2019;Rahman et al., 2022).This manner can have substantial economic benefits, as renewable energy systems can provide a stable source of energy that is less vulnerable to price fluctuations and supply disruptions.On the other hand, energyefficient practices and technologies, such as precision agriculture, improve the efficiency of the equipment and machinery, reduce energy consumption in buildings and facilities, and optimize irrigation systems, to reduce water and energy use (Gathala et al., 2020;Iddio et al., 2020;Lefers et al., 2020).These technologies can also help farmers to identify inefficient areas and implement targeted solutions to improve their operations.Regarding waste management, there are also opportunities to integrate energy and waste management systems in agriculture to produce bioenergy which can be used for transportation fuels, electricity, heat, and product (Giampietro, 2019;van Ruijven et al., 2019;Jain et al., 2022).For instance, biogas and biofuel production from agricultural waste and crops can provide a sustainable source of renewable energy that can be used to power farm operations, fed into the grid, transportation, and other applications.Moreover, anaerobic digestion can convert organic waste materials, such as animal manure, food waste, crop residues, and wastewater biosolids, into bioenergy and biochemicals (Lefers et al., 2020;Chew et al., 2021;Osman et al., 2022).Therefore, farmers can reduce their operating costs, improve their bottom line, and reduce their environmental impact by reducing energy consumption.WEF-CBE aligns with key Sustainable Development Goals (SDGs), including Zero Hunger (SDG 2), Clean Water and Sanitation (SDG 6), Affordable and Clean Energy (SDG 7), Responsible Consumption and Production (SDG 12), and Climate Action (SDG 13).WEF-CBE promotes sustainable agriculture and food production by efficiently utilizing biological resources, reducing waste, and enhancing food security (Pastor et al., 2019;Ansari et al., 2021;Tan and Lamers, 2021;el-Ramady et al., 2022;Kumar Sarangi et al., 2023).It focuses on sustainable resource management, including water, to minimize pollution and conserve water resources.This can unlock new pathways towards achieving more resilient, resource-efficient, and sustainable water management to meet the socioeconomic needs of communities and ensure the long-term availability of high-quality water resource for future generations, which align with the long history of Mar del Plata (MDP) and New York City (NYC) water conference (Quentin Grafton et al., 2023).Moreover, it contributes to the sustainable management of blue, green, and grey water by optimizing freshwater, improving water retention in soil, and promoting wastewater treatment and reuse through practices like precision irrigation, regenerative agriculture, and innovative technologies.WEF-CBE supports the transition to clean and renewable energy sources through bioenergy from organic waste and biomass, reducing reliance on fossil fuels.It encourages responsible consumption and production patterns, aiming to minimize waste generation and optimize resource utilization.WEF-CBE contributes to climate action by reducing greenhouse gas emissions through sustainable practices and the use of renewable resources, promoting lower carbon footprints and climate-resilient strategies.
Previous studies have analyzed CBE practices in agriculture that have already been applied in several countries focusing on the efficient utilization and treatment of agricultural waste (Duan et al., 2020;Ngammuangtueng et al., 2020;Khan and Ali, 2022).For example, a study by Ngammuangtueng et al. (2020) assessed the nexus of water, food, and energy in Thailand's cassava and sugarcane supply chains.They highlighted the need to prioritize improvements in cultivation even better water and energy use efficiency are needed for a more sustainable bioeconomy.Another study from Khan and Ali (2022) indicated that CBE could be applied in Pakistan's agriculture sector by using residual agricultural waste as a biomass resource for generating valuable bio-products and bioenergy.This approach can help achieve higher standards of sustainability in the sector.Indeed, a study by Duan et al. (2020) reported that organic solid waste biorefinery is considered a promising approach for achieving a CBE in China, which can contribute to environmental protection and sustainable development by reducing greenhouse gas emissions and conserving biodiversity.Moreover, hydrothermal processing of microalgal biomass is regarded as a promising technology to generate a multitude of energy-based and value-added products (biochar, biofertilizers, and platform chemicals) (Behera et al., 2022).Utilizing algal biomass for hydrothermal processing makes it a viable bioresource providing ample opportunities to establish and integrate the value and supply chain products for addressing the issues linked to the combined nexus.This technology can accelerate the circular bioeconomy by providing sustainable energy and value-added platform solutions.
Additionally, Conservation Agriculture based Sustainable Intensification (CASI), exemplifying agricultural practices with broad socioeconomic implications, has diverse impacts, including increased productivity and income, resource efficiency, cost savings, environmental sustainability, social equity and empowerment, and climate change resilience (Dixon et al., 2019(Dixon et al., , 2020)).These impacts align with the goals of the CBE and contribute to the efficient use of water, energy, and food resources.The success of CASI, as highlighted in the studies by Dixon et al. (2019Dixon et al. ( , 2020)), is evident through its adoption on over 15% of global cropland, including irrigated farming systems (e.g., Eastern Gangetic Plain) and rainfed systems.One key factor contributing to their success is the integration of conservation practices, such as reduced tillage, soil cover, and diversified cropping systems.These practices optimize water and energy use by enhancing water retention, reducing soil erosion, and minimizing energyintensive activities.CASI also improves food production, addresses food security challenges, and builds climate resilience through sustainable intensification strategies to get higher crop yields while minimizing negative environmental impacts.The diversified cropping systems in CASI enhance resilience to climate variability and mitigate risks associated with monoculture systems.Furthermore, the scalability and adaptability of CASI to different agroecological conditions have facilitated its rapid adoption in various regions.
Implementing CBE into WEF nexus creates a range of conditions that promote resource efficiency, sustainability, and resilience.Firstly, a shift towards CBE fosters integrated and holistic approaches to manage water, energy, and food systems.This encourages synergistic interactions and optimizing resource allocation among the different sectors, minimizing waste and maximizing resource utilization.CBE promotes adopting practices and technologies that enhance resource efficiency within the WEF nexus.For example, water-efficient irrigation systems, renewable energy generation, and sustainable agricultural practices are implemented to minimize water and energy consumption while ensuring adequate food production.Moreover, WEF-CBE encourages innovation and collaboration among stakeholders.It creates opportunities to develop new technologies, business models, and value chains that promote resource efficiency and sustainability.This collaboration among different sectors, such as agriculture, energy, and water management, fosters knowledgesharing, capacity-building, and co-creating solutions for integrated resource management.

Challenges and limitations
The WEF-CBE in agriculture offers significant benefits but also entails challenges and limitations.Balancing trade-offs and synergies within the nexus component is a major challenge (Putra et al., 2020;Wu et al., 2021;Zhao et al., 2021;Ding and Chen, 2023;Wang et al., 2023).For instance, using renewable energy from crops and agricultural waste may lead to competition for land use and potential conflicts between food and energy components (Dixon et al., 2010;Langeveld et al., 2014).The cultivation of biofuel feedstocks such as corn and sugarcane often demands substantial amounts of water, leading to increase pressure on water sources.This can worsen water scarcity in regions already facing water stress and create competition  (Piacentino et al., 2019;Chang et al., 2020;Zhang et al., 2022;Osman et al., 2023;Wang et al., 2023).However, certain regions may lack suitable infrastructure and technologies, and the high cost can hinder small-scale farmer communities' adoption (Gilg and Barr, 2006;Gadenne et al., 2011;Tiefenbeck et al., 2013).On the other hand, investments in research, development, infrastructure, and training are necessary but can be costly and pose barriers to adoption.
Innovative business models are needed to incentivize sustainable practices and technologies.Insufficient financial resources, technological expertise, and supportive policies and regulations further hinder achieving economic and environmental sustainability.
Implementing WEF-CBE may encounter socioeconomic and cultural challenges, which vary depending on the context and location (Dixon et al., 2020;Ngammuangtueng et al., 2020;Khan et al., 2021;Bottausci et al., 2022;Ncube et al., 2022).Limited awareness and understanding of the integration's potential benefits can hinder support from stakeholders and the public, making it difficult to secure necessary resources and funding.Moreover, adopting WEF-CBE may require changes in consumption and production patterns, which can face consumer resistance and producers hesitant to embrace new practices.Social equity and distributional impacts also present challenges, as improper implementation may result in uneven distribution of benefits and costs among different social groups, leading to conflicts and inequalities.Additionally, the WEF-CBE faces environmental limitations due to chemical, biological, and physical factors.Therefore, evaluating the WEF's strengths, weaknesses, opportunities, and threats is essential for understanding its potential (Table 1).
To overcome the challenges within WEF-CBE, collaboration and investment from governments, policymakers, and the private sector are crucial.Sustainable technologies, research, and development should be prioritized to address limitations and promote a holistic approach (Schöggl et al., 2020).Engaging local communities, stakeholders, and policymakers in planning and implementation is vital to ensure equitable distribution of benefits and even achieve economic and environmental sustainability (Klein et al., 2022).Capacity building and knowledge transfer programs are essential to increase understanding and awareness among stakeholders.These programs can disseminate best practices, case studies, and research findings through various platforms.Farmers, industry leaders, and policymakers can benefit from tailored capacity-building programs.Awareness campaigns can encourage public participation and support.Establishing a framework for monitoring, evaluating, and adapting policies and practices is crucial.This framework should consider environmental and socioeconomic aspects and involve all relevant stakeholders.Through fostering collaboration among different sectors, it promotes innovation and co-creation of knowledge and practices to enhance sustainability.

Conclusion
Altogether, the WEF-CBE in agriculture provides a comprehensive framework for promoting sustainable resource management, creating collaboration between different sectors, and advancing CBE practices.The potential benefits of incorporating biological processes into the circular economy model, provide opportunities for the sustainable production of food, energy, and other goods, to achieve food security, sustainable economic growth, and reduced environmental impacts, making it a worthwhile endeavor.Additionally, this approach can provide new income streams for farmers, boost rural development, and support the achievement of SDGs.However, to fully realize the potential of this integration, there is a need for supportive policy and institutional frameworks, significant infrastructure investments, the development of new technologies, and a better understanding of social and cultural constraints.Finally, public engagement and awarenessraising campaigns through capacity-building and knowledge transfer programs are necessary to build support for the WEF-CBE and encourage behavioral change.

FIGURE 1
FIGURE 1Synergies and trade-off of WEF nexus with circular bioeconomy.