Biosustainability and Waste Valorization—Advancing the Circular Bioeconomy Paradigm

1. Introduction

The global pursuit of sustainable development requires a paradigm shift towards reduced bioresource consumption and enhanced circularity in resource management. In the face of environmental degradation, climate change, and resource depletion, the concept of biosustainability has emerged as a critical concept for ensuring a viable future. Biosustainability involves maintaining the health and productivity of biological systems while minimizing the ecological footprint of human activities. In this context, waste valorization is a strategic approach that reduces pressure on bioresources by converting residues and by-products into valuable products. Additionally, the adoption of green chemistry practices has emerged as a vital strategy for reconciling economic growth with ecological preservation. These interrelated concepts are pivotal in the transition towards a circular bioeconomy, where materials and energy flow in closed loops to minimize waste and enhance resource efficiency.

On 20 December 2024, the European Union published a report on waste recycling across Europe, revealing worrying trends [1]. Although there has been an increase in recycling rates and a shift towards a circular economy, driven by previous progress and binding EU recycling targets, this momentum has stagnated in recent years. In some cases, there has even been a decline in recycling efforts, with the overall waste recycling rate in 2022 being lower than it was a decade before. In 2022, the overall recycling rate—measured as the proportion of total waste generated (excluding major mineral wastes) that was recycled—stood at 44% [1]. Most waste was still managed through incineration or landfill disposal instead of valorising it in a new productive cycle. To advance circularity and reduce the environmental impact of natural resource use, more ambitious waste management policies are required that promote recycling and discourage landfilling and incineration.

Driven by the urgent need for a rapid transition, successful examples of circular product development based on waste recovery are increasingly emerging and being used as models of sustainable production and consumption. In response, guidelines are now being proposed to support companies in developing circular products through waste recovery, aligning with the broader goals of efficient resource use and waste reduction through prevention, minimization, recycling, and reuse [2].

As production demands evolve, the agricultural and food sectors are generating substantial amounts of waste, making them a priority for the development of sustainable industrial processes. Indeed, this waste can be used as a raw material in the production of high-value goods [3], and a variety of environmentally friendly technologies are now facilitating the transformation of waste into valuable products for use in the pharmaceutical and food industries [4].

The adoption of the 2030 Agenda for Sustainable Development in 2015, along with the identification of key priority areas to achieve the Sustainable Development Goals (SDGs) [5], marked a significant global commitment. This milestone reflected the shared recognition that a transition towards a more sustainable, inclusive, and resilient world was urgent, where economic growth, social equity, and environmental protection were balanced for the benefit of current and future generations.

According to the 2025 SDG Progress Report [6], only 35% of the 137 SDG targets are currently on track or showing moderate progress. Almost half (47%) are making slow or insufficient progress, while 18% have actually regressed compared to the 2015 baseline. With just five years remaining to meet the 2030 targets, the report emphasizes the urgent need to accelerate efforts and reverse these negative trends. In line with this call to action, this Special Issue (SI), entitled “Biosustainability and Waste Valorization”, emphasizes the urgency of integrating sustainable practices across agriculture, forestry, industry, and ecosystems to achieve the SDGs. The ten contributions published in this SI reflect the multifaceted nature of biosustainability, emphasising the need for interdisciplinary collaboration to address the critical challenges our planet faces. Moreover, the contributions offer practical solutions to transform waste into value, mitigate environmental impacts, and promote responsible consumption. Below, we elucidate the impact of each contribution to the SDG and their collective role in advancing the circular bioeconomy.

Invasive species from the Ambrosia genus pose significant ecological challenges, including the suppression of native vegetation and crops, soil degradation, and the release of potent allergens [contribution 1] Using these weeds as a sustainable source of material for producing biogas could help meet energy demands, reduce the reliance on non-renewable carbon sources, and mitigate the environmental impact of invasive plants. Contribution 1 explores the dual benefit of managing the noxious weed Ambrosia artemisiifolia (belonging to the family of Asteraceae), which can cause significant damage to human health, to generate bioenergy while detoxifying heavy metals (copper, chromium, and iron) through a diverse microbial community. The anaerobic digestion of Ambrosia artemisiifolia provides a sustainable approach to producing renewable energy, which addresses SDG 7 (Affordable and Clean Energy) while advancing SDG 6 (Clean Water and Sanitation) by improving ecosystem restoration through the bioremediation of contaminated environments.

Sensors have a wide range of applications, being used to ensure consistent quality in different manufacturing processes, detect contaminants and pathogens, and act as spoilage indicators to ensure food safety. They are also used for environmental monitoring, such as monitoring air and water quality, and in healthcare for medical diagnostics and patient monitoring. Developing small, versatile, and portable sensors is of the utmost importance, and electrochemical devices can offer a viable solution due to the downsizing capability of electrode components enabled by nanotechnology and microfabrication processes. Currently, conventional glassy carbon electrodes are still widely used as transducers in the development of new electrochemical sensors for pollutants, but carbon fibre paper has been established as an excellent alternative due to its interesting physicochemical, electronic, and electrochemical properties [contribution 2]. Recently, carbon fibre paper has been increasingly used in electrochemical sensors for a variety of compounds. Contribution 2 uses life cycle assessment to demonstrate the reduced environmental burden of sensors when comparing them with a conventional chromatographically based analytical technique (HPLC) for detecting ketoprofen pharmaceutical drugs in fish samples. Ketoprofen is among the most widely used anti-inflammatory drugs and is also one of the most frequently detected pharmaceuticals in the environment. It has the potential to bioaccumulate and cause adverse effects on ecosystems and human health. As well as demonstrating significant environmental savings through the transition to carbon fibre paper sensors, the research presented in contribution 2 also supports SDG 14 (Life Below Water) by promoting more environmentally friendly analytical techniques for monitoring aquatic pollutants and consequently improving the protection of marine and freshwater ecosystems from pollution. Furthermore, this research promotes green analytical chemistry and provides tools for sustainable monitoring practices in environmental sciences.

One of the major challenges facing contemporary societies is waste management. Population growth, coupled with widespread consumption and industrialization, has led to an alarming increase in waste production. To avoid harmful environmental impacts and the misuse of resources, urgent action is needed to combat this issue. One potential solution is the creation of industrial symbioses [contribution 3], which are characterized by the practical application of circular economy principles and the use of collaborative platforms. Soares et al. [contribution 3] explore the role of digital platforms in fostering industrial symbiosis, enabling companies to exchange waste and by-products. As a practical tool for circular economy implementation, the proposed Upvalue platform represents a digital innovation toward smarter, more sustainable industrial ecosystems. Their study addresses SDG 9 (Industry, Innovation, and Infrastructure) by proposing scalable solutions for waste exchange and resource efficiency in businesses with the development of an innovative digital infrastructure to support industrial collaboration. It encourages the modernization of industrial processes through technology and supports more inclusive and sustainable industrialization by making resource-efficient practices accessible to a broader range of businesses, including small- and medium-sized enterprises.

The rapid increase in the global population has resulted in an escalation in food production, with intensified agricultural practices being employed to meet the growing demand. Despite advancements in food processing technologies offering high production efficiencies, the generation of waste and food by-products is still increasing, posing serious environmental and socioeconomic consequences. This kind of waste is usually rich in bioactive compounds and has nutritional value. It can be valorized by extracting compounds of biological interest and incorporating them into cosmetic products [contribution 4] or producing high-quality ingredients for use in ice cream bases [contribution 5]. Gomes et al. [contribution 4] highlight the valorization of kiwi peel extract in moisturising creams, and the extract’s demonstrated antioxidant and antibacterial activities reinforce its potential in natural product-based cosmetics. This reduces the dependency on synthetic additives and aligns with the growing demand for clean beauty products. The valorization of kiwi peels into antioxidant-rich cosmetic ingredients merges waste reduction with green chemistry, promoting SDG 12 (Responsible Production and Consumption) and SDG 3 (Good Health and Well-Being) while showing how agro-waste can replace synthetic additives in personal care products. Trejo-Flores et al. [contribution 5] transform food waste into a nutritious ice cream base, developing sustainable food formulations while promoting food security and reducing waste. The study revealed that an ice cream base with excellent physicochemical, functional, and sensory properties can be prepared using mango seed kernel and cheese whey waste, demonstrating how biosustainability principles can be applied in agro-food systems to address food security (SDG 2—Zero Hunger) and waste reduction (SDG 12—Responsible Production and Consumption).

Ensuring the protection of forests is essential for achieving environmental, social, and economic sustainability. However, the threat of wildfires has intensified due to climate change, poor forest management and the accumulation of unmanaged forest residues. Although legislation requires such residues to be removed from forests and pastures, compliance is often limited, particularly among private landowners, due to the high operational and disposal costs involved. In response, the Municipality of Viseu in northern Portugal has established a network of biomass collection centres to facilitate the removal of agricultural and forestry waste across the region. This initiative helps to reduce the incidence of rural fires and promotes the recovery and valorization of residual bioresources. Effective waste management should align with the waste hierarchy: prevention, preparation for reuse, recycling, valorization (e.g., energy recovery), and as a last resort, disposal. Nonetheless, deviations from this order may be warranted for certain waste streams when a life cycle assessment reveals broader environmental benefits [contribution 6]. In such cases, it is essential to rethink these waste streams within the framework of the circular economy, to ensure the full potential of bioresources is harnessed and reintegrated into productive use. Using LCA, contribution 6 assessed and compared the potential environmental impacts associated with the mulching, composting, and energetic valorization of agricultural and forest residues. Composting was identified as the most environmentally friendly option. The study not only quantifies environmental impacts, supporting SDG 13 (Climate Action), but also guides decision-making for local authorities, exemplifying the role of waste management in improving biosustainability at the community level.

Another challenge is to increase the resilience and resistance of forests to mitigate the effects of climate change. Instead of performing clear-cutting, the management strategy must therefore be to adopt an approach involving managing uneven-aged forests, despite its low economic performance, because of the sustainable ecological bene-fits. Crisan et al. [contribution 7] analyse forest management strategies to preserve biodiversity and stable conditions in Romanian mountain regions. By comparing uneven-aged forest stands, the study evaluates natural growth conditions and silvicultural practices. Its insights are crucial for sustainable forest management, emphasising the importance of biodiversity and the conservation of ecosystem services within the biosustainability agenda. This work contributes to SDG 15 (Life on Land) by encouraging silvicultural practices that balance ecological resilience with economic needs, providing a global model for sustainable forestry.

The textile industry is well known as being one of the most polluting sectors. Its harmful environmental impact results from excessive energy, water, and chemical consumption, as well as the production of textile waste and the release of microfibres into the environment during washing. Driven by rising demand for clothing and the expansion of the fast-fashion model, the textile industry is undergoing a transformative shift towards sustainability, prompted by increased environmental awareness and evolving policies. Various eco-friendly solutions for the textile industry have been identified for reducing the sector’s carbon and ecological footprint. The most important of these practices are bio-dyeing and wastewater treatment via bioremediation. Using natural dyes derived from waste is an environmentally sustainable and healthy way to replace chemical dyes in the textile industry, and it also constitutes a way of waste valorization. Contribution 8 demonstrates the potential of grape pomace as a sustainable textile dye to replace synthetic alternatives. Grape pomace, an agro-industrial waste product, can also be used for eco-friendly textile dyeing. This study provides a model for rethinking industry practices in the textile sector, combining biosustainability and circularity through the synergy of agro-waste valorization and eco-friendly consumer practices. This alternative to synthetic dyes is viable, reduces toxic waste, and promotes SDG 12 (Responsible Production and Consumption).

The logistics sector is one of the largest consumers of fuel and energy, contributing significantly to greenhouse gas emissions. Using straw as a transported material in the straw recycling process, particularly in heavy-duty trucks, raises environmental concerns due to the high fuel consumption associated with these vehicles, which poses a serious threat to environmental sustainability. Developing efficient straw logistics networks therefore presents an opportunity to reduce environmental impacts and promote more sustainable practices in the sector. Mao et al. [contribution 9] propose a model to optimize straw recycling logistics, balancing economic viability with environmental benefits in north-east China. By minimising transportation costs and carbon emissions, their work exemplifies how biomass supply chains can enhance the sustainability of power generation. This study aligns with SDG 7 (Affordable and Clean Energy) and SDG 12 (Responsible Consumption and Production) by offering a plan for low-carbon logistics networks, and directly addresses biosustainability through systemic infrastructure planning.

Volatile organic compounds (VOCs) are a major contributor to air pollution, particularly in industrial areas. They pose well-documented environmental and health risks and require efficient, sustainable control policies. These concerns have led to the development of new treatment technologies, including biological treatment technologies such as biofilters, biotrickling filters, and bioscrubber, as well as emerging technologies such as bioaugmentation and microbial fuel cells. Contribution 10 reviews biological methods for VOC treatment and explores cutting-edge strategies to control air pollution. It promotes sustainable alternatives to conventional methods of controlling air pollution and highlights future directions for energy valorization, thereby contributing to the achievement of SDG 13 (Climate Action) and SDG 9 (Industry, Innovation, and Infrastructure).

2. Final Remarks

Collectively, these ten contributions form a coherent response to the challenges identified in the scope of this SI. They reflect real-world applications and theoretical advancements that contribute to (i) reducing bioresource consumption and the environmental impact; (ii) promoting waste-to-resource strategies in agriculture, industry, and energy; (iii) implementing green chemistry and biotechnology for sustainable production; (iv) fostering local and global circular economy models; and (v) enhancing monitoring and decision-making with advanced tools.

While the thematic scope is wide, the unifying thread is clear: biosustainability cannot be achieved without transforming waste into value. Each contribution underlines the importance of intersectoral cooperation and scientific innovation in overcoming sustainability bottlenecks.

We are deeply grateful to all the authors, reviewers, and the editorial team for their contributions and collaboration. The solutions presented here move us a step closer to achieving a circular and sustainable bioeconomy (Figure A1). This is our modest contribution towards meeting the 2030 targets for achieving the SDGs.