Search Results (24)

The valorisation of household and commercial bio-waste into soil improvers helps to reduce disposable waste, mitigate climate change, and improve soil resilience. While the separate collection of bio-waste is mandatory in the European Union, this remains a challenging task, particularly for large cities, due to quality problems in densely populated areas. In addition to various informational and motivational tools for households, financial incentives are becoming increasingly important. However, there is a lack of robust evidence regarding the optimal use of these incentives and their impact on the quantity and quality of collected bio-waste. We investigated the impact of different charging systems on the quantity and quality of bio-waste, basing our research on the experiences of more than twenty European cities and using a detailed questionnaire completed by the relevant administrators. The results confirm that cities, which provide financial incentives for waste sorting, yield a higher quantity of separated bio-waste. As introducing tiered fees can lead to quality issues, monitoring bio-waste and taking action against polluters seems to be unavoidable. Since the identification of polluters is very difficult in the case of multi-family homes, the results are discussed with a special focus on densely populated cities. Pilot projects for alternative options for the valorisation of organic waste, particularly in districts with high-rise buildings, should be evaluated. Full article

The sustainable conversion of biogenic waste into high-value materials presents a promising approach for addressing environmental and industrial challenges. This work reports an advancement into antioxidant-enriched phosphate minerals derived from green conversion of biogenic calcium carbonates of crustaceans. We demonstrate the effectiveness of Raman technology in controlling conversion using phosphoric acid treatment. The effects of reaction parameters—including acid stoichiometry, granular size distribution, and thermal treatment at 700 °C and 1200 °C—were systematically evaluated. Raman spectroscopy results validated by X-ray diffraction (XRD) and SEM-EDX analyses revealed mixed-phase minerals monetite, brushite, whitlockite or hydroxylapatite, respectively. Notably, reducing particle size enhanced conversion efficiency by increasing the reactive surface area, while the use of excess phosphoric acid facilitated conversion to monocalcium phosphate and promoted the degradation of the organic matrix. Thermal treatment further altered the product composition: heating at 700 °C produced a whitlockite-rich phase, whereas treatment at 1200 °C shifted the balance toward hydroxylapatite. The synthesized calcium phosphate compounds, including hydroxylapatite, monocalcium phosphate, whitlockite, and brushite, hold significant practical utility in biomedical applications (such as bone grafts and dental implants), agriculture, and industrial processing. Moreover, we have proven that by controlling the reaction parameters the final product composition can be tailored according to the specific needs. A greener approach yields brushite, monetite, or monocalcium phosphate, while a more energy-demanding process, including heating to 1200 °C, yields a high-purity hydroxylapatite. This research offers a sustainable analytical route for producing high-purity calcium phosphate materials from wasted biomaterials, contributing to both the bioeconomy as well as scientific innovation. Full article

The Mediterranean region is increasingly confronted with intersecting environmental, agricultural, and socio-economic challenges, including biowaste accumulation, soil degradation, and high dependency on imported fossil fuels. Biomethane, a renewable substitute for natural gas, offers a strategic solution that aligns with the region’s need for sustainable energy transition and circular resource management. This review examines the current state of biomethane production in the Mediterranean area, with a focus on anaerobic digestion (AD) technologies, feedstock availability, policy drivers, and integration into the circular bioeconomy (CBE) framework. Emphasis is placed on the valorisation of regionally abundant feedstocks such as olive pomace, citrus peel, grape marc, cactus pear (Opuntia ficus-indica) residues, livestock manure, and the Organic Fraction of Municipal Solid Waste (OFMSW). The multifunctionality of AD—producing renewable energy and nutrient-rich digestate—is highlighted for its dual role in reducing greenhouse gas (GHG) emissions and restoring soil health, especially in areas threatened by desertification such as Sicily (Italy), Spain, Malta, and Greece. The review also explores emerging innovations in biogas upgrading, nutrient recovery, and digital monitoring, along with the role of Renewable Energy Directive III (RED III) and national biomethane strategies in scaling up deployment. Case studies and decentralised implementation models underscore the socio-technical feasibility of biomethane systems across rural and insular territories. Despite significant potential, barriers such as feedstock variability, infrastructural gaps, and policy fragmentation remain. The paper concludes with a roadmap for research and policy to advance biomethane as a pillar of Mediterranean climate resilience, energy autonomy and sustainable agriculture within a circular bioeconomy paradigm. Full article

Agri-food waste management poses a growing challenge in the pursuit of sustainable development. This bibliographic review analyses the scientific literature from 2014 to 2025 to examine current methods of agro-waste valorisation and the application of circular-economy principles in the transformation of biological waste into valuable resources. Special attention is given to nanofibers—particularly nanocellulose—and other high-value biocomponents. The review assesses these recovery practices’ economic, ecological, and health-related impacts and the relevant barriers to implementation. Potential application domains are discussed, and estimations of waste quantities and future trends are provided. The findings highlight the importance of investment in sustainable technologies and increased stakeholder awareness in efforts to optimize agri-food waste valorisation and support the transition to a more sustainable agricultural sector. Full article

Municipal wastewater treatment plants produce vast amounts of sewage sludge as waste, with more than 80% dewatered sludge (DS). DS is a polymer-based sludge containing flocculant and extracellular polymeric substances, including lipids. Lipids can be converted into biodiesel as an alternative energy that reduces dependency on fossil fuels while helping cities manage waste more sustainably. Past studies explored the potential of lipids from various sewage sludges in biodiesel production. However, the potential of DS remains largely unexplored. This study evaluates the lipid extracted from DS and the potential of its fatty acid methyl ester (FAME) to be used as biodiesel. Lipid extraction was conducted under varying parameters, including temperatures of 70, 80, and 90 °C, extraction time of 2, 4, 6, and 8 h, and sludge-to-solvent (S/L) ratios of 0.05, 0.075, 0.1, 0.125, 0.15, and 0.175 g/mL. The optimal extraction conditions of 70 °C for 4 h at S/L of 0.175 g/mL yielded 1.71 ± 0.10% lipid. FTIR and TGA revealed that the DS lipids contain triglycerides, fatty acids, glycerol, and proteins. Transesterification of DS lipids produced DS FAME with a fatty acid profile ranging from C4:0 to C22:0. The evaluation of DS FAME revealed a high ester content (94.7%) of fatty acids ranging from C14:0 to C24:1, surpassing the minimum standard of 90% for biodiesel. The elevated proportion of unsaturated fatty acids in DS FAME is expected to result in a low melting point, reducing the solidifying effect and enhancing its performance as biodiesel. Full article

Biowaste from livestock production is increasing globally because of the intensification of livestock farming and inefficient waste management practices. If mismanaged, biowaste can result in environmental problems, including increased greenhouse gas (GHG) emissions. Anaerobic digestion (AD) stands as an effective approach for managing livestock biowaste, simultaneously generating biogas for energy recovery and digestate for agronomic application, following the principles of the circular economy. Considered a biowaste-to-energy approach, AD mitigates GHG emissions, facilitates nutrient recovery, and reduces dependence on fossil fuels. Despite its acknowledged benefits and status as a mature technology, further research is required to identify the best route for optimising the process in terms of stability and performance. This review examines new research that explores innovative ways to enhance the mesophilic AD process in continuous-stirred tank reactors, including the use of additives, especially carbon-based ones like biochar. From this perspective, the key challenges are exploring new insights into future research routes to implement AD units at a real scale, and pursuing goals towards a circular economy model. Finally, new opportunities have arisen for farmers to create synergies across agro-industrial sectors, enabling them to minimise their environmental footprint and simultaneously earn additional revenue. Full article

The management of the organic fraction of municipal solid waste (OFMSW), also called urban biowaste, and urban wastewater sludge (UWWS) represents a challenge for cities and regions, which want to adopt innovative urban bioeconomy approaches for their treatment and production of high-added-value products beyond the traditional anaerobic digestion (AD) and compost. This adoption is often restricted by the availability and maturity of technologies. The research object of this manuscript, based on the findings of EU Horizon 2020 project HOOP, is the identification of state-of-the-art circular technologies for material valorisation of OFMSW and UWWS, following a novel screening methodology based on the scale of implementation (tested at least at pilot scale). The screening resulted in 25 technologies, which have been compared and discussed under a multidisciplinary assessment approach, showing their enabling factors and challenges, their current or potential commercial status and their compatibility with the traditional technologies for urban biowaste treatment (composting and AD). The bioproducts cover market sectors such as agriculture, chemistry, nutrition, bioplastics, materials or cosmetics. Therefore, the results of this review help project promoters at city/region level to select innovative technologies for the conversion of OFMWS and UWWS into high value products. Full article

The use of biobased substances derived from industrial and household waste as renewable raw materials for environmental applications is gaining prominence due to its sustainable and cost-effective approach to waste valorisation. Herein, we report the uptake of paraquat, a widely used pesticide, by magnetite nanoparticles coated with composted urban biowaste-derived substances (MNP-BBS). The magnetic nanoparticles were prepared using a modified co-precipitation method, and were characterized through various physicochemical techniques. They were tested as an adsorbent for paraquat removal under diverse experimental conditions, exploring the influence of pH (3–10), MNP-BBS dosages (200–1000 mg L⁻¹), ionic strength (0–0.01 M), and presence of organic matter. The kinetic study revealed that the adsorption of paraquat onto MNP-BBS follows the pseudo-second-order model, reaching the adsorption equilibrium after 2 h of contact and 90% of paraquat removal in the best condition tested (1000 mg L⁻¹). The equilibrium experimental data showed a high adsorption performance with a good fitting to the Freundlich isotherm model. Also, from Langmuir model a maximum adsorption capacity of 0.085 mmol g⁻¹ was estimated. The results indicated that electrostatic interaction between the negative functional groups of the adsorbent and the paraquat play a major role in the adsorption mechanism, although the contribution of π-π and hydrophobic interactions cannot be completely ruled out. This research underscores the potential of utilizing MNP-BBS as an effective adsorbent for the removal of paraquat, shedding light on its application in sustainable water purification processes. Full article

The valorisation of sewage sludge for sustainable agricultural use and biofuel production proposes an effective and beneficial management of sewage sludge in a closed-loop cycle. The management of sewage sludge biowaste is a rising problem due to increasing waste storage expenses. In this sense, the use of circular economy principles in sewage sludge management creates opportunities to develop new technologies for processing. The biorefinery model allows the application of wasteless technologies via sewage sludge valorisation in terms of agricultural use and biofuel production, especially with the hydrothermal carbonisation method. Applying hydrothermal carbonisation in the treatment of biosolid sewage sludge has numerous benefits due to processing highly hydrated organic waste into carbon hydro char, a high-quality solid biofuel. The direct use of sewage sludge in the soil does not allow for full use of its functional properties. However, the hydrothermal carbonisation of sewage sludge results in biocarbon pellets, making it a viable approach. This work also discusses the barriers (legal, chemical, biological, and technical) and possibilities related to sewage sludge biorefining processes. Full article

This paper focuses on the optimisation of an efficient extraction process for cellulose and lignin from rice straw waste from the Albufera of Valencia using the steam explosion method. This method is particularly pertinent given the environmental and economic challenges posed by the current disposal practices of agricultural waste. The technique comprises a high-temperature cooking stage followed by instantaneous decompression, effectively altering the biomass’s physical and chemical properties to enhance its surface area and porosity. Our adaptation of the steam explosion technique specifically addresses the challenges of rice straw waste, marking a significant departure from previous applications. This innovation is crucial in addressing the urgent need for more sustainable waste management practices, as it effectively deconstructs the lignocellulosic matrix of rice straw. This facilitates the selective extraction of cellulose at a 70% efficiency, with a 20% yield and the subsequent recovery of lignin. The results of this study are significant for sustainable biomaterial production, offering novel insights into optimising these crucial biomass components. By refining the process and focusing on critical parameters, our work advances the application of steam explosion methods for agricultural waste, enhancing efficiency and sustainability. By utilising rice straw biowaste, this research not only proposes a solution to a pressing environmental issue but also demonstrates the potential to create new market opportunities, increase the economic value for rice producers, and significantly reduce the environmental footprint of existing waste disposal methods. The holistic and ecological approach of this study underscores the vital need for innovative strategies in agricultural waste management, positioning the valorisation of rice straw waste as a key component in the pursuit of environmental sustainability. Full article

By the end of 2023, biowaste must be completely separated or recycled at source, based on EU legislation. Separate biowaste collection and valorisation for biofuels could play an essential role in the biobased circular economy. In this context, the principal goal of this paper was to demonstrate on a pilot scale the technological solution of bioethanol production via the utilisation of urban source-separated biowaste within the city context of Athens, Greece. More specifically, the main aim was the demonstration of a pilot system for more than 10 consecutive operating cycles with real feedstock—wet; separately collected biowaste. From the 11 pilot trials performed with wet feedstock, the mean starch and cellulose degradation of the pilot trials amounted to 80.69 ± 16.27% and 79.41 ± 10.37%, respectively, while the bioethanol yield was 74.05 ± 6.82%. The latter was comparable to that of more intensive pretreatment methods. Homogenization and shredding, which were applied in this study, stand as promising pretreatment methods for bioethanol production from wet feedstock. Further research is needed to optimize conditions and evaluate scalability. Nevertheless, pilot-scale testing is a crucial step in the deployment of this technology since it serves as a bridge between laboratory research and full-scale implementation, offering a practical and controlled environment to validate and optimize the technology while minimizing risks and uncertainties. Conclusively, this study could stand as a flagship case study for the implementation of circular and sustainable approaches in the management of organic fractions of source-separated municipal waste, showcasing the technical feasibility of the whole value chain from waste collection to final bioethanol product recovery. Full article

Municipal biowastes are conventionally treated by assessed anaerobic and aerobic fermentation to produce biogas, anaerobic digestate, and compost. Low-temperature hydrolysis and the oxidation of the digestate and compost, which are still at the experimental stage, are known to yield water-soluble value-added chemical specialities for use in different sectors of the chemical industry and in agriculture. The present paper reports the application of the two chemical reactions to the biowastes before fermentation. The products obtained in this manner are compared with those obtained from the chemical reactions applied to the fermented biowastes. Based on the experimental results, the paper discusses the expected environmental and economic benefits of the above chemical processes and products in comparison with the products obtained by other known biotechnologies for the valorisation of biomass as a feedstock for the biobased chemical industry. The results point out that a sustainable biowaste-based refinery that produces biofuel and biobased chemicals may be developed by integrating chemical and fermentation technologies. Full article

The valorisation of municipal and household biowaste as a relevant component of the EU’s Circular Economy Strategy is currently under discussion. However, there are several legal, technical and economic challenges associated with biowaste valorisation. This paper aims to pinpoint factors affecting biowaste supply chains using the PESTEL+I method and stakeholder workshops. Our analysis focuses on the macro-environment of an integrated biowaste conversion and valorisation concept in the region of Wallonia, Belgium. One key influencing factor is the EU’s legal framework on waste, which describes the end-of-waste status and defines criteria for biowaste reuse. While the analysis shows that EU regulations support biowaste valorisation, its transposition into national and regional law is lagging behind. The technological development of biowaste concepts might be hampered and many questions related to the marketisation of bio-based products remain unanswered. We therefore suggest that legal procedures for biowaste management have to be facilitated at the regional level. The region of Wallonia should establish a category for biowaste that would include standardized procedures for biowaste valorisation and products. It is essential that such regional barriers be overcome to establish the necessary cooperation with local stakeholders and to transfer biowaste supply chains to the market. Full article

Composting is one of the most viable alternatives to landfill disposal to reduce the environmental impacts of organic waste management, such as the emission of greenhouse gases (GHGs). A community composting system consisting of four 1 m³ modules was installed in a selected primary school in Bellaterra (Spain) and monitored through daily analysis of the main process parameters (temperature, moisture content and interstitial oxygen) and weekly analysis of gaseous emissions (CH₄, N₂O and VOCs). The composting process was successful and gaseous emissions were maintained under desirable values, which can be used to support and promote this kind of initiatives. Full article

The environmental impact of biowaste generated during animal production can be mitigated by applying a circular economy model: recycling, reinventing the life cycle of biowaste, and developing it for a new use. The aim of this study was to evaluate the effect of adding sugar concentrate solutions obtained from the nanofiltration of fruit biowaste (mango peel) to slurry from piglets fed with diets incorporating macroalgae on biogas production performance. The nanofiltration of ultrafiltration permeates from aqueous extracts of mango peel was carried out using membranes with a molecular weight cut-off of 130 Da until a volume concentration factor of 2.0 was reached. A slurry resulting from piglets fed with an alternative diet with the incorporation of 10% Laminaria was used as a substrate. Three different trials were performed sequentially: (i) a control trial (AD₀) with faeces resulting from a cereal and soybean-meal-based diet (S0); (ii) a trial with S₁ (10% L. digitata) (AD₁), and (iii) an AcoD trial to assess the effect of the addition of a co-substrate (20%) to S1 (80%). The trials were performed in a continuous-stirred tank reactor (CSTR) under mesophilic conditions (37.0 ± 0.4 °C), with a hydraulic retention time (HRT) of 13 days. The specific methane production (SMP) increased by 29% during the anaerobic co-digestion process. These results can support the design of alternative valorisation routes for these biowastes, contributing to sustainable development goals. Full article