Sustainable Environmental Technologies: Recent Development, Opportunities, and Key Challenges

1. Introduction

The ongoing increase in global population, industrialization, urbanization, and intensive agricultural practices has resulted in a wide range of environmental challenges including increased waste generation, rising greenhouse gas emissions, the uncontrolled release of emerging and toxic pollutants, degraded soil, water, and air quality, the depletion of natural resources, and the escalating impact of climate change [1]. In response to these growing concerns, the development of sustainable environmental technologies has emerged as an indisputable priority since the beginning of the twenty-first century [1,2,3,4]. These technologies, especially in areas such as pollution prevention and remediation, waste-to-energy conversion, renewable/clean energy, greenhouse gas reduction, resource recovery, and the conservation of natural resources, play a pivotal role in advancing sustainable development [4,5,6]. The primary goals of these technologies are to focus on innovation, develop new technological solutions through sustainable processes, and significantly address the most pressing environmental issues facing our society [2,7,8]. Additionally, they aim at promoting a transition to a more sustainable and resilient planet for future generations. Various organizations/companies/industries are being urged to adopt sustainable technology in order to lower their carbon footprints and track their progress towards achieving sustainable development goals. While sustainable environmental technologies have evolved in various fields in recent decades, there is still limited knowledge regarding their full potential and their ability to address environmental problems effectively.

This Topic project was a special collection of the latest multi-disciplinary and comprehensive research/review papers as well as innovative research models, published recently (2022–2023) in four MDPI journals (Water, Environment, Toxins, and Applied Science). The collection explores diverse facets of sustainable environmental technologies (Figure 1) and aims at summarizing these technologies, highlighting the latest developments and future directions in the field. The goal is to enhance the understanding of their application in combating environmental problems and fostering a greener future. It also highlights some exciting developments of frontier technologies with sustainability potential, while discussing the current challenges and perspectives of future research and innovations required for sustainable technologies to be successfully adapted and effective. This special collection accepted 65 articles including 55 research papers and 10 reviews for publication, covering research areas such as environmental remediation, sustainable materials, waste to energy, resource recovery, renewable/clean energy, and the role of AI and ML in sustainability. These papers cover 162 primary and partner institutions across the world (from 40 countries and six continents−including Asia, Africa, North America, South America, Europe, and Australia−), showcasing the global diversity of the subject covered here. An overview of the themes of sustainable environmental technology, the focus of this Topic project, is given below:

2. Renewable/Clean Energy Technologies

Renewable energy technologies such as solar, hydro, and wind power are leading the way in providing alternatives to fossil fuels [4,9]. These technologies aim to reduce carbon, energy consumption, and greenhouse gas emissions. The growing interest in solar energy has led to the development of several photovoltaic (PV) technologies, with silicon-based PV modules becoming increasingly popular because of their exceptional long-term stability, high efficiency, and durability. Pandey et al. [10] reviewed the recent advances in solar PV systems and their potential application towards more sustainable energy solutions. They found photovoltaic thermal, building-integrated PV systems, desalination, and concentrated photovoltaic applications of solar PV to be the most technically sound and feasible solutions at the user end for future energy challenges. Despite their benefits, these PV modules generally have an operational lifespan of 25 to 30 years; thus, the number of PV modules that are approaching the end of their useful life has gradually increased, which poses a significant risk to the environment if they are disposed of incorrectly. To address this issue, Ko et al. [11] examined the processes for separating silicon photovoltaic modules and compiled efforts to produce modules that are easier to recycle. Their study findings provide valuable guidance for creating effective waste management strategies aimed at minimizing the environmental impact of PV modules at the end of their life cycle.

Furthermore, green technologies, including green hydrogen electric vehicles and natural gas, have gained increasing attention as sustainable and clean energy alternatives in recent years. According to Zhang et al. [12], natural gas has responded more favorably to the substitution impact in G7 nations as they move away from conventional energy sources and toward clean and renewable ones, and this is more significant in countries like the UK, France, Italy, and Japan. This trend underscores the importance of emphasizing natural gas’s role as a key component of the energy transition and energy conservation efforts. Green hydrogen, produced through the process of hydrolysis, is another promising energy resource that is gaining momentum. It has diverse potential applications in various sectors, such as transportation, industry, and power generation [13]. Recently, several ground-breaking research studies have further advanced this field. Falcone et al. [14] reviewed green hydrogen technology in the context of sustainable development goals. They have demonstrated the potential of hydrogen as a clean energy source and how it can be used to achieve both social and environmental objectives. Yu et al. [15] discussed various low-carbon hydrogen generation techniques and green, blue, and aqua hydrogen, exploring their benefits and the differences in each approach while highlighting how each reduces carbon emissions. The article also highlighted the process involved in producing green hydrogen from renewable resources, blue hydrogen from carbon capture and storage, and aqua hydrogen using nuclear power and electrolysis. In another study, Abate et al. [16] indicated that microalga–bacterium consortia have significant potential for advancements in biotechnology related to renewable energy generation, particularly in the area of biohydrogen. These findings demonstrate how these techniques could promote sustainable energy transitions and contribute to a low-carbon hydrogen economy.

3. Waste-To-Energy Conversion

Waste management technology is currently undergoing a significant transformation, revolutionizing how we manage different types of waste [17]. Recent innovations in this field are enabling the conversion of waste into energy, producing sustainable resources, and replacing traditional, non-renewable materials with energy derived from plant and animal sources [17,18,19]. As a result, biomass waste is increasingly being converted into valuable products such as ethanol, biofuels, bioenergy, and biogas, all of which are key contributors to a more sustainable future. For example, Anacleto et al. [20] conducted a detailed analysis of biogas production, specifically methane (CH₄), from textile waste. Their study found that using biological pretreatments, instead of chemical methods, could boost methane production by up to 360%, while being more environmentally friendly and cost-effective. This method not only generates clean energy but also reduces environmental impact by facilitating the reuse of textile wastewater. In another study, Sharma et al. [19] investigated the potential of lignocellulosic biomass like rice straw and other agricultural residues as potential raw material for high-value-added products like bioethanol and biodiesel. The result indicated that the use of these biomasses can replace petrochemical products, positioning them as essential components of sustainable and renewable energy production. For instance, rice straw can be gasified using fermentation techniques to produce biogas or methane. Furthermore, rice straw could be used for renewable biohydrogen production, where it undergoes fast pyrolysis to produce bio-oil, which is then reformed with steam to produce hydrogen [18]. Additionally, Okolie et al. [21] experimented with the potential of converting human and animal waste into biofuels, sustainable materials, and value-added chemicals. These technologies could significantly reduce waste deposition as well as greenhouse gas emissions into the atmosphere. The study demonstrates considerable advancements in converting human and animal waste into biofuels and value-added materials through thermochemical and biological conversion pathways. It also noted that the USA, China, and England are the leading nations in research on resource recovery from human or animal waste4. Remediation of Emerging/Toxic Contaminants

With the increasing presence of emerging/chemical contaminants in the environment, the use of sustainable, low-cost materials plays a major role for the cleanup of contaminated sites and the treatment of wastewater or contaminated water bodies [6,22,23,24]. Several studies are currently underway to address this formidable pollution crisis. Ganie et al. [23] studied the role of carbon nanotubes as a nano-remediation approach for water decontamination. Their results indicated that carbon nanotubes are regarded as effective adsorbents for the removal of both organic and inorganic pollutants such as heavy metals, harmful organic contaminants including Dichlorodiphenyltrichloroethane (DDT), pesticides, chlorinated solvents, and perfluoroalkyl and polyfluoroalkyl substances (PFAS). The high adsorption capacity of carbon nanotubes is due to their large surface area and hollow layered structure, making them a promising alternative to conventional methods. In contrast to many conventional techniques, nano-remediation techniques offer long-term sustainable solutions by reducing the cost of cleaning up polluted areas and producing less waste. In addition, biochar, a low-cost sustainable material, has shown enormous potential as an engineered material in environmental remediation. Al Masud et al. [24] reviewed the diverse applications of biochar in remediating contaminated soil, water, and air. The review highlighted biochar’s sustainability and eco-friendly characteristics from lab-scale to field-scale experiments, demonstrating its effectiveness to in mitigate contaminants, improving soil quality and restoring ecosystems. Similarly, Sachdeva et al. [25] investigated the use of biochar in immobilizing potentially hazardous elements (PTEs) in agricultural soils. Their study demonstrated that biochar effectively reduced the mobility and bioavailability of heavy metals such as Pb, Cd, Cu, and Ni in soils, leading to a lower uptake of these metals by plants. This enhanced biochar adsorption potential is due to its high surface area, porosity, pH, aromatic structure, and several functional groups, which mostly rely on the feedstock type and pyrolysis temperature. Thus, this study shows that agriculture waste-based biochar can be an effective option for soil remediation and sustainable agriculture. Biochar has also been effectively applied in the treatment of polluted water and wastewater. Thakur et al. [22] reviewed the possible application of various feedstock-based raw and modified biochar in the remediation of geogenic pollutants such as fluoride (F⁻) and uranium (U) from aqueous solutions. The data showed that cellulose- and hemicellulose-rich feedstocks, including agricultural residues, grasses, softwood, and manure-based biochars, were successful in removing U and F⁻ at low-to-medium pyrolysis temperatures. While metal oxide, hydroxide, and alkali modification promoted F-adsorption, acidic and magnetic modification favored U adsorption.

Similarly, Neulls et al. [26] investigated the effectiveness of plant-based waste materials as adsorbents for removing nitrogen-based chemicals from water. The results demonstrated that in comparison to animal biomass and chitosan, vegetal biomass and pineapple crowns were more effective in eliminating organic pollutants from water bodies. Therefore, the use of these plant-based biomasses is a practical and affordable solution to lessen the amount of waste that ends up in sanitary landfills and dumps while also addressing environmental pollution. The performance of the denitrifying bacterial strain Pseudomonas sp. in a laboratory-scale sequencing batch reactor was examined in another study conducted by Chen et al. [27]. The findings imply that microorganisms can improve total nitrogen (TN) elimination by bioaugmentation. A metal–organic framework (MOF) was developed by Sun et al. [28] as an effective sorbent for environmentally friendly oil–water separation. Similar to this, an MOF was used by Karami et al. [29] to remove methyl orange from water, showing the versatility of MOFs in water treatment. Phytoremediation, a process that uses plants to remove contaminants from the environment without creating secondary pollution, is another low-cost, sustainable, and effective option compared to conventional procedures based on chemical extraction. In another study conducted by Park and Son [30], the phytotoxicity and accumulation of antibiotics in two different types of plants were examined. The researchers found that water lettuce had a higher accumulation of antibiotics in its tissues compared to parrot feather plants, indicating its great potential for removing xenobiotics from contaminated environments. These plants possess a natural ability to adapt and thrive in harsh, polluted conditions, making them valuable tools for environmental cleanup. Overall, these studies offer insightful information on the technical developments in the production of sustainable materials for the removal of pollutants from water and soils. The integration of plant-based solutions, microbial bioaugmentation, and MOFs highlights the growing potential of sustainable, low-cost methods for addressing environmental contamination.

4. AI and ML Application in Environmental Sustainability

Artificial intelligence (AI) and machine learning (ML) models are increasingly playing a pivotal role in addressing key challenges related to the management of natural resources, improving the accuracy of contaminant detection and optimizing remediation strategies [31,32,33]. AI is also being used for the timely monitoring of natural resources, including water, soil, energy, minerals, coal, oil, natural gas, biodiversity, and forests, as well as for decision assistance, in order to increase environmental sustainability. Pandey et al. [31] demonstrate an in-depth review on the use of AI and ML approaches and big data in the management of natural resources. This study explained the data-driven methods for decision-making, emphasizing how AI and ML can help policymakers assess the current status of natural resources, create evidence-based policies, and identify areas that require improvement. By utilizing these technologies, both public and private sectors can better manage natural resources, ensuring their responsible extraction and long-term preservation for future generations. In another study, Rao et al. [32] examined the nexus between natural resources and environmental sustainability for the period 1990–2020 in 19 Asian countries through the ML approach. This study mainly focused on the impacts of the Industrial Revolution, and digitalization revealed interesting results. This research indicated that when natural resource use is between 0.1 and 9.87, CO₂ emission decreases, but when the range is 0–0.1 or above 9.87, the impact on CO₂ emission is positive. The analysis further revealed that urbanization, energy use, and economic complexity make the greatest contributions in Asian CO₂ predictions. This finding suggested that governments in Asian countries should use these AI/ML techniques to effectively manage their resources. Similarly, AI has demonstrated effective use for the discovery of mineral resources [33], as well as the management of water bodies, energy, transportation, and biodiversity [34]. Similarly, Zhao et al. [35] used a multi-indicator weighted robustness analysis to monitor planktonic communities in marine plankton ecosystems. This network technology exposed unseen topological flaws and provided a new direction for future research. The findings of this work can help with marine conservation and the sustainable management of these sources. Additionally, AI approaches are revolutionizing agriculture for sustainable and precision farming. These methods make food production more environmentally friendly and sustainable by utilizing resources more wisely. Overall, these studies advance scientific knowledge and innovative ideas that could aid in highlighting the importance and dynamic nature of sustainable environmental technology, which is not just transforming the environment and industries, but also laying the foundation for a more sustainable and eco-friendly future. The continued advancement and widespread use of these technologies will be essential to solving contemporary environmental problems on a worldwide scale.

5. Key Challenges and Future Prospects for Advancing Sustainable Technologies

Although sustainable technologies have proven to be an effective and promising solution for addressing a range of various environmental issues, they also face some key challenges that hinder their widespread adoption and advancement. These challenges include high production costs, technological limitations, infrastructure and logistics barriers, and research and regulatory hurdles [5]. There are also several challenges to improve efficiency and effectiveness in innovation and turn sustainability into a reality/practice for field-based applications One such issue is evident in the renewable energy sector. Despite the fact that a significant number of patents have been filed on various green energy technologies such as solar, wind, tidal, and hydrogen energy, all of which have the potential to lower greenhouse gas emissions, some of these emerging technologies are still at the research or development stage within some energy companies. As a result, despite the promise of these technologies, they are not yet ready for large-scale commercial deployment, limiting their ability to deliver technological innovations for broader market applications. To overcome these challenges and support the further development of these technologies, the following future directions are essential: (1) Advance research infrastructure and significant investment should be made across multiple sectors to foster innovation, increase efficiency, minimize costs, and create cutting-edge applications in sustainable technologies [3]. (2) In the energy sector, funding low-carbon projects is urgently needed, and interest-free or low-interest allowances must be established in order to improve the use of contemporary technologies [9]. Additionally, breakthrough research is needed to upgrade the energy system and introduce advanced batteries and hydrogen fuel cells that can produce less waste and fewer toxic fumes, with the potential to overcome conventional technologies. (3) In the transportation sector, the rise in electric vehicles (EVs) alongside policy measures can be a major focus to create a more sustainable future by reducing greenhouse gas emissions. Also, innovations in smart grid technologies are required for a further contribution to environmental sustainability. (4) In newly developed cities or buildings, there is an emerging need to use the Internet of Things (IoT) to optimize energy usage and minimize waste. This smart technology will also optimize resource usage and provide easy solutions for water quality and quantity management, air quality monitoring, and urban planning. (5) Furthermore, to address the real demands of mitigating climate change, green and low-carbon efforts as well as the idea of the “dual-carbon” goal should be taken into consideration in conjunction with the initiative of energy saving and carbon emission reduction. Additionally, to strengthen the renewable energy market system and resource conservation, each country’s SDG targets must include environmental tax and financial subsidy policies [2]. (6) Furthermore, emphasis should be placed on strong collaboration and partnership between various stakeholders including governments, financial institutions, and civil society to finance renewable energy projects, sustainable infrastructure, and initiatives to address climate change and drive significant positive changes towards achieve sustainable development goals [9]. (7) Governments worldwide should also prioritize climate change action plans to regulate greenhouse gas emissions and effect the transition to a low-carbon economy. They should also implement methods like carbon pricing in order to incentivize the reduction in environmental impact. (8) Moreover, the integration of artificial intelligence (AI), machine learning (ML), and big data into sustainability research will bring new opportunities to optimize resource usage, manage natural resources in real time, mitigate climate change, and drive innovation in the energy sector [36]. By integrating vast amounts of data from diverse sources, including sensors, Internet of Things (IoT) devices, and digital platforms, these technologies can find novel solutions for urgent environmental issues and advance the understanding required to comprehend the extent of their use in addressing those issues and pinpoint areas for improvement.

Other challenges include ecological destruction, land use, and habitat impact. For example, land use and habitats will be affected by any large-scale renewable energy projects, which emphasizes the importance of ecological impact assessments and sustainable practices to minimize disturbance and preserve biodiversity. Moreover, the lack of a scientific framework for the systematic and integrated assessment of technology innovation at various phases of the life cycles of technological advances may result in an unclear picture of the full range of their sustainability performance. In order to undertake a systematic sustainability assessment of such technologies at different stages, urgent research is needed to develop such frameworks. Addressing these challenges is essential to effectively incorporate and optimize the capabilities of environmentally friendly technology, which would be useful to researchers, decision makers, and organizations in guiding technological advancements for sustainable environmental practices and keeping the planet in good shape for future generations.

6. Opportunities in Sustainable Environmental Technologies

Environmental technologies offer numerous opportunities for innovation and technological advancements across various sectors, creating potential for new enterprises or research centers that provide employment opportunities. By enabling businesses to create sustainable materials and services in response to the rising consumer demand for sustainability, these technologies promote corporate innovation and encourage collaboration among various stakeholders from governments, industries, and international organizations. Moreover, environmentally friendly technologies play a major role in the battle against climate change, as they help reduce carbon emissions and resource consumption, thus mitigating environmental degradation. From a social perspective, these technologies contribute to improved living standards by ensuring access to cleaner water and air, as well as creating a healthier environment for agriculture. They also provide a means to achieve national and global sustainability goals, advancing progress toward a more sustainable future. In essence, the widespread adoption of environmental technologies holds significant potential to not only stimulate economic growth but also pave the way for a fairer and more sustainable global community.

7. Conclusions

This Editorial, prepared for the Topic project ‘Sustainable Environmental Technologies’, provides a comprehensive overview of the current trends and recent technological advancements in the field of environmental sustainability. It highlights the key challenges faced in this area, along with potential solutions and strategies for moving forward. As demonstrated throughout this paper, the utilization of sustainable environmental technologies, driven by innovation, can significantly contribute to mitigating environmental degradation, reducing greenhouse gas emissions, enhancing energy security, and offering promising solutions to resource depletion and waste reduction. Moreover, the integration of artificial intelligence and machine learning models has proven effective in predicting and optimizing resource conservation and contributing to the shaping of a more sustainable future. However, many challenges related to such technology remain, including cost barriers, the lack of a scientific framework for the systematic assessment of technology innovation, and the potentially negative environmental impacts of certain technologies, that constitute significant hurdles to overcome. It is crucial for researchers, policymakers, industry leaders, governments, and research institutions to collaborate in a unified effort to address these challenges. A collective commitment to advancing technological innovation through high-quality research, systematic assessment, and methodological rigor is critical for overcoming the current barriers and ensuring practical and impactful innovations. Such collaborative efforts are key to unlocking the full potential of sustainable technologies and safeguarding the health of our planet for future generations. Furthermore, the success of these technologies towards long-term environmental goals will require the establishment of supportive policy frameworks, incentives for investment, and global cooperation to accelerate their development and implementation. These combined efforts will be vital in overcoming the existing challenges and enabling a successful transition toward environmental sustainability.