Biowaste Management Research Articles

Chemical Production Based on Biomass—Potential and Limits

As the raw material transition from fossil to renewable feedstock progresses, the demand for biogenic raw materials for industrial purposes will increase. This applies above all to the energy and chemical sectors. However, the capacities for biogenic energy and carbon sources to be provided by agriculture and forestry are limited. This review examines the contribution that biogenic raw materials and CO2 from biogenic sources can make to sustainable chemical production in the EU. It analyses statistical data from the EU and studies from the chemical industry. First priority needs to be given to edible biomass for the sector of nutrition. When it comes to the industrial use of biomass, sectors should be prioritised that cannot do without carbon-supplying raw materials. This is particularly the case in the field of organic chemistry. This review focuses on bio-based organic chemical products and gives an outlook on the future of chemical production in Europe based on primary, secondary, and tertiary biomass and CO2 from biogenic sources. Finally, two new indicators for economically and ecologically sustainable industrial use of biomass are proposed. Both indicators can support the determination of the sustainability status of the sustainable integration of agriculture, forestry, residual, and biowaste management in bioeconomic value networks.

Evaluation de la rentabilité de la production de larves de la Mouche Soldat Noire (MSN) dans les unités de production du projet IITA-BBEST-Mali

Unsustainable biowaste management and unsustainable supply of feed for fish and poultry farming are 2 major challenges of emerging cities including Bamako. The Black Soldier Fly (BSF) technology transforms these challenges into an opportunity through an ecological method of decomposing biowaste into economically valuable products - animal feed and organic fertilizers. It is based on the principle of circular bioeconomy which stands out from the linear economy and is based on the principles of the 3Rs (Reduce, Reuse and Recycle) as opposed to: Buy - Use - Throw away. It gives a new life and creates new value chains from organic agropastoral waste. It is then perceived as a business model to stimulate private investment in sustainable biowaste management and sustainable production of animal feed and organic fertilizers. This requires an initial establishment cost and a production cost that must necessarily be made available to the future investor. To determine these costs, we identified, quantified and evaluated the costs required to obtain MSN larvae in the larva production units in Sotuba and IPR/IFRA. The production costs obtained were respectively 685.50 FCFA/kg of larvae for the type of production with fly breeding and 837.13 FCFA/kg for the type of production without fly breeding. The profitability rates were respectively 102.18% and 51.07%. Keywords: Black Soldier Fly, Production cost, Profitability.

A Proposed Circular Economy Model for Hospital Bio-Waste Management in Municipal Settings

This paper presents a proposed circular economy (CE) model for hospital bio-waste management, using Athens as a case study to demonstrate its applicability in urban environments. The model incorporates waste segregation at the source, resource recovery methods such as composting and anaerobic digestion, and data-driven tools to enhance the efficiency and sustainability of healthcare waste management. The study investigates the transition from linear to CE practices, focusing on structured collection strategies, collaborative efforts between hospitals and municipal authorities, and continuous tracking of waste flows. A comprehensive analysis of bio-waste volumes from participating hospitals over a three-year period is conducted, utilizing multi-criteria decision-making (MCDM) tools such as TOPSIS to evaluate the system’s effectiveness. The results indicate a significant increase in hospital participation, improved waste separation, and optimized resource recovery, offering a scalable framework for other municipalities seeking to implement CE-based waste management practices in healthcare settings.

Upcycled cosmetic ingredients: extraction process optimization via green solvents by the means of I-optimal and Box–Behnken designs

Current trends are shifting attention to the sustainable valorization of food bio-waste management and by-product utilization, as they are rich in nutrients and bioactive compounds, such as dietary fiber, polyphenols, and peptides. Upcycled ingredients and green cosmetics are becoming more and more appealing concepts in the nutraceutical and cosmetic industries encouraging them to invest and develop sustainable products aligning with the green concept of circular economy. In this research, we focused on the waste products (peels) of super exotic fruits Litchi chinensis and Selenicereus undatus, which are packed with antioxidants, fibers, vitamins, and minerals. Extraction of the peels with green solvent (propylene glycol) was performed and optimized by the means of an I-optimal and box-behnken designs with different independent variables for each design and total phenolic content (TPC) as a response. The resulted optimized extract of lychee peels propylene glycol extract (LPPG) was evaluated in terms of anti-tyrosinase activity, resulting in an (IC50 = 264.1 ± 16.9 µg/mL) with an average inhibition percentage of (92.33%), DPPH assay was performed, revealing antioxidant activity of (2666.7 ± 68.71 µmol ascorbic acid/mL) and (24,774.68 ± 834.67 µmol ascorbic acid/mL) using ABTS assay. As for dried dragonfruit propylene glycol extract (DDPG), the antioxidant activity was found to be (1299.82 ± 20.80 µmol Ascorbic acid/mL) using DPPH assay and (1510.506 ± 12.93 µmol Ascorbic acid/mL) using ABTS assay. In conclusion, optimization of the extraction process of food by-products using propylene glycol as a solvent may offer a valuable sustainable cosmetic ingredient.

Path-dependencies in the transition to sustainable biowaste valorization: Lessons from a socio-technical analysis of Sweden and Greece

Achieving sustainable biowaste management is a key challenge for cities worldwide. In this context, biowaste valorization is an indispensable option for managing unavoidable biowaste and reducing the associated methane emissions. Several innovations that enable biowaste valorization are technologically mature. However, their implementation is still limited in most cities around the world. Therefore, it is essential to better understand the different pathways towards implementing biowaste valorization. This paper presents a case-study of two countries at different phases in their transition to biowaste valorization: Sweden as a case at a mature phase and Greece as a case at a formative phase. We apply the Technological Innovation Systems framework to investigate how innovation systems for biowaste valorization develop and associated path-dependencies. Our findings show that various path-dependence lock-ins can occur at different transition phases. Our empirical insights suggest that a focus on the diffusion of certain mature innovations can support the growth of biowaste valorization systems. However, it can also lead to path-dependence lock-ins that influence the systems’ resilience to shocks. We thus recommend decision-makers to pursue balance between the rapid diffusion of mature innovations for biowaste valorization and parallel support for experimenting with more radical innovations to harness the systems’ resilience to shocks.

Optimizing Object Detection in Bio-Waste Management with Improved Hyperbolic Tangent YOLOv5 and Binarization-Adapted K-Means Algorithm

<p style="margin-bottom:11px;text-align:justify;"><span style="font-family:Calibri,sans-serif;font-size:11pt;line-height:107%;">With the increasing importance of green development, bio-waste classification has become an important element of green development. However, in garbage stacking scenarios, the task of segmenting highly overlapping objects is difficult because the bottom garbage is in an occluded state and it is usually difficult to distinguish its contours from occluded boundaries. This paper presents a rotationally invariant system for solid bio-waste container detection and bio-waste level classification. This paper proposes a rotationally invariant system for detecting solid bio-waste containers and classifying their fill levels. It employs Hough line detection to identify container orientations and positions, complemented by cross-correlation for distinguishing similar objects. Features extracted from within and outside the container area are utilized, enabling precise determination of discard levels. The system accommodates varying bio-waste amounts through transformation and rotation of container images. Object detection utilizes an Improved Hyperbolic Tangent-based YOLOv5 model with a Binarization-Adapted K-Means Algorithm (BKA) to enhance sorting accuracy. Additionally, the method efficiently calculates object motion through segmented BKA-detected objects. Experimental validation with a bio-waste image dataset demonstrates superior performance in accuracy, specificity, sensitivity, and overall precision compared to existing methodologies.</span></p>

Novel Specifications Regarding Biogas Production from Agriengineering Activities in Romania

This study centers on examining the carbon/nitrogen (C/N) ratio and metal levels in various batches of manure and their potential impact on biogas production through anaerobic fermentation. A novel aspect of this research involves the utilization of nine distinct batches sourced exclusively from livestock manure found in Romanian farms, without mixing with other potential substrates. At present, the farms are not harvesting manure for energy, but they are keen to invest in biogas production in the future as a necessary step towards renewable energy in a circular economy and a bio-waste management model. As a general conclusion that is resulting, it is shown that both the C/N ratio and the content of heavy metals in animal manure must be known when dealing with the animal manure fermentation process, especially when aiming for biogas production. The C/N ratio in the analyzed samples ranges from 6.7 to 30.2. While the ideal ratio is often considered 20–30, good methane production can occur outside this range, as seen in Sample B (small pig farm), with a C/N ratio of 13.8, proving the highest methane output. This shows that the C/N ratio is important but not the only factor influencing biogas generation. The metal content in the manure samples is similar to other studies, with potassium (K) ranging from 1.64% to 8.96%. Calcium (Ca) and K are the main metals found, posing little concern. The variation in values is linked to feed recipes. Monitoring heavy metals is crucial not only for biogas production but also for the safe use of animal manure as fertilizer, as soil contamination limits must be continuously supervised. The results are also valuable for the management of waste used as fertilizer in agricultural fields in accordance with EU law.

Marine Ecosystems and Pollution: Intersection of Zoology and Law in Environmental Sustainability

Marine Biowaste, resulting from natural biological processes or human activities, seriously threatens the environment. Sources and impacts of Marine bio waste are discussed, classifying into two broad categories: Organic and Inorganic. Organic biowastes include those from aquaculture, agricultural runoff, industrial discharges, and urban runoff, while inorganic Biowaste include plastics, microplastics, metals, and synthetic materials. Those sources present pollution, habitat destruction, and impacts on marine species, which together drastically close the ecological balances. The role of zoology in Biowaste degradation is important, because it is concerned with the study of organisms responsible for breaking down organic wastes to make nutrients available. Both National and International legislation, such as UNCLOS and MMPA in the United States, provide a legal framework for the protection of Marine ecosystems from pollution and overexploitation. Advances in Marine biotechnology offer novel solutions to problems related to bio waste management, such as algal Biofuels and integrated waste management systems. Synthetically, biology trends, adaptation of climate change, and models of the circular economy provide potential solutions for future research and sustainable practices. This paper gives reasons for full strategies of Biowaste management with a view towards the preservation of Marine ecosystems and assurance of Environmental sustainability.

Resolving Coffee Waste and Water Pollution-A Study on KOH-Activated Coffee Grounds for Organophosphorus Xenobiotics Remediation.

This study investigates using KOH-activated coffee grounds (KACGs) as an effective adsorbent for removing organophosphorus xenobiotics malathion and chlorpyrifos from water. Malathion and chlorpyrifos, widely used as pesticides, pose significant health risks due to their neurotoxic effects and environmental persistence. Spent coffee grounds, abundant biowaste from coffee production, are chemically activated with KOH to enhance their adsorptive capacity without thermal treatment. This offers a sustainable solution for biowaste management and water remediation. Adsorption kinetics indicating rapid initial adsorption with high affinity were observed, particularly for chlorpyrifos. Isotherm studies confirmed favorable adsorption conditions, with higher maximum adsorption capacities for chlorpyrifos compared to malathion (15.0 ± 0.1 mg g-1 for malathion and 22.3 ± 0.1 mg g-1 for chlorpyrifos), highlighting its potential in mitigating water pollution. Thermodynamic analysis suggested the adsorption process was spontaneous but with the opposite behavior for the investigated pesticides. Malathion interacts with KACGs via dipole-dipole and dispersion forces, while chlorpyrifos through π-π stacking with aromatic groups. The reduction in neurotoxic risks associated with pesticide exposure is also shown, indicating that no more toxic products were formed during the remediation. This research contributes to sustainable development goals by repurposing biowaste and addressing water pollution challenges through innovative adsorbent materials.

Synthesis of agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads: Characterization and application as controlled-release microencapsulated fertilizers

Synthesis of novel agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads, micromeritic/morphometric characteristics of the prepared formulations, greenhouse trials using controlled-release microencapsulated fertilizers, and acute fish toxicity testing were conducted simultaneously for the first time within the scope of an integrated research. In the present analysis, for the first time, 16 different morphometric features, and 32 disinct plant growth traits of the prepared composite beads were explored in detail within the framework of a comprehensive digital image analysis. The hydrogel beads composed of 19 different agro-industrial wastes/materials were successfully synthesized using the ionotropic external gelation technique and CaCl2 as cross-linker. According to micromeritic characteristics, the ionotropically cross-linked beads exhibited 77.86 ± 3.55 % yield percentage and 2.679 ± 0.397 mm average particle size. The dried microbeads showed a good swelling ratio (270.02 ± 80.53 %) and had acceptable flow properties according to Hausner's ratio (1.136 ± 0.028), Carr's index (11.94 ± 2.17 %), and angle of repose (25.03° ± 5.33°) values. The settling process of the prepared microbeads was observed in the intermediate flow regime, as indicated by the average particle Reynolds numbers (169.17 ± 82.81). Experimental findings and non-parametric statistical tests reveal that dried fertilizer matrices demonstrated noteworthy performance on the cultivation of red hot chili pepper plant (Capsicum annuum var. fasciculatum) according to the results of greenhouse trials. Surface morphologies of the best-performing fertilizer matrices were also characterized by Scanning Electron Microscopy. Moreover, the static fish bioassay experiment confirmed that no abnormalities and acute toxic reactions occurred in shortfin molly fish (Poecilia sphenops) fed with dried leaves of red hot chili pepper plants grown with formulated fertilizers. This study showcased a pioneering investigation into the synthesis of microcapsules using synthesized hydrogel beads along with digital image processing for bio-waste management and sustainable agro-application.

Comparative analysis between the impacts produced by centralized biowaste management – a hospitality sector case study in Brazil

Comparative analysis between the impacts produced by centralized biowaste management – a hospitality sector case study in Brazil

Characterization of fresh biowastes for biogas production and environmental health in Niger Delta, Nigeria

BackgroundEnvironmental pollution is a public health problem in Niger Delta, Nigeria. Therefore, the aims of the present study were to: identify the major fresh biowastes in Bayelsa State, Niger Delta; quantify the biogas yields from mono-digestion and co-digestion of identified biowastes; determine the first day of biogas production during hydraulic retention time; assess pH variations during anaerobic digestion; and evaluate biogas flame colours.MethodsFifteen communities in Bayelsa State were randomly selected, and on-the-spot assessment and quantification of the biowastes found in each community were carried out daily per week. Mono-digestion of 20 kg of each biowaste and co-digestion of 10 kg of animal waste with 10 kg of plant waste were carried out respectively under anaerobic conditions. Cumulative biogas yield and pH were measured using a pH meter and weighing scale respectively. Biogas flame colours during combustion were visually assessed.ResultsExactly 120.61 metric ton of fresh biowastes was found to be generated per week in Bayelsa State, Niger Delta. Industrial biowastes were the highest [47.6 tonnes, (39.46%)], followed by abattoir biowastes [33 tonnes (27%)], market and roadside sellers biowastes [25.5 tonnes (21.14%)], and farm biowastes [14.51 (12.03%)]. Biogas yields (kg) were: 0, 0, 0, 0, 0, 17, 14, 2, 18, 16, 17, 15 and 1 kg for palm oil mill effluent (POME), orange fruit waste (OFW), pineapple peels (PP), plantain peels, cassava mill effluent (CME), rumen digesta (RD), cow dung, sewage, PP-RD, plantain peels-cow dung, POME-rumen digesta, OFW-cow dung, and CME-sewage respectively. The first day of biogas production for RD, cow dung, sewage, PP-RD, plantain peels-cow dung, POME-RD, OFW-cow dung, and CME-sewage was on the 6th, 32nd. 56th, 1st, 26th, 18th, 25th, and 60th day of hydraulic retention time respectively. A dominant blue flame colour mixed reddish yellow or orange flames were found during biogas combustion. A slight increase in pH was found in all the biodigester media.ConclusionsIn the present study, a variety of biowastes yielding various quantities and qualities of biogas were identified in Bayelsa State, Niger Delta. The study’s findings have provided evidence-based data that might be explored as a road map and catalyst for policy creation against inadequate biowaste management and as sustainable alternatives to the expensive liquefied petroleum gas. The potential of current research study to be scaled up for commercial use is implicated in the present study.

Enhancing the potential application of food-waste biochar as a sustainable bio-solid fuel: Analysis of post-treatment and combustion behavior

Food-waste biochar holds significant potential as a bio-solid fuel for achieving carbon neutrality; however, its high content of sodium (Na), potassium (K), calcium (Ca), chlorine (Cl), and nitrogen, inhibits its potential use. This study explored the effects of post-treatment with ascorbic, acetic, citric, and iminodiacetic acids on the properties of food-waste biochar and volatile ionic substances to establish a foundation for assessing both the environmental impact and practical use of food waste. Post-treatment with organic acids achieved 92% Cl-removal efficiency and induced deformation of the functional groups of food-waste biochar surfaces, leading to the re-adsorption of alkali and alkaline earth metals. This re-adsorption of alkali metal ions showed a distinct correlation with NOx mitigation. The amount of re-adsorbed Na and K varied based on the types of organic acids, resulting in different NOx emission reduction effects. Iminodiacetic acid was particularly effective in alleviating Ca and PO4 volatilization, whereas citric acid exhibited the highest Ca elution performance, and the Ca-contained leachate is a potential source of CO2 storage through indirect mineral carbonation. Acetic acid is the most feasible alternative, considering both economic and environmental aspects. The findings suggest that the post-treatment of food-waste biochar effectively mitigates air pollutants during combustion and is beneficial for sustainable biosolid fuel production and bio-waste management.

Clam shell waste recycling and valorization for sustainable Hg remediation

Shellfish aquaculture world production is constantly growing due to the increase in demand for seafood and reached over 18 million tons in 2022. The suitable management of the shell waste is one of the main environmental challenging issues as most of this waste is sent to landfills with emanation of foul odors, pathogens proliferation and reduction of available space. However, the conversion of this biowaste to new value-added materials could provide significant environmental and economic benefits. Clam shell waste was the starting material for the synthesis of hydroxyapatite (CSHAP) applied as an adsorbent for Hg2+ removal from aqueous solutions. Adsorption experiments were performed in batch using simulated wastewaters prepared from HgCl2 to investigate the effects of contact time and initial Hg2+ concentration on the removal process. Mineralogical composition, morphological features and elemental composition of CSHAP before and after the experiments were investigated by XRPD, SEM-EDS and FTIR analysis. The concentrations of Hg2+ and Ca2+ in the solutions were analyzed by ICP-AES. The adsorption kinetics of Hg2+ was simulated with the pseudo-first-order rate model, the pseudo-second order model and the intraparticle diffusion model. The results of the kinetics study showed that the Hg2+ adsorption followed the pseudo-second-order kinetics model and reached equilibrium within 40 min. The Langmuir model fitted the experimental results better than the Freundlich, Temkin and Dubinin-Radushkevic isotherm models, with a maximum adsorption capacity of 65.8 mg/g which is generally higher than other waste-derived adsorbents used for the removal of Hg2+ ions from water. The removal mechanism includes rapid surface complexation on CSHAP grains, followed by a slow incorporation of the Hg2+ ions in the crystalline structure. The results of this study could contribute to delineate a new research direction for a more sustainable management of clam shell biowaste.

Innovative Strategies for Bio-Waste Collection in Major Cities during the COVID-19 Pandemic: A Comprehensive Model for Sustainable Cities—The City of Athens Experience

This paper introduces an innovative model for the organization and management of municipal bio-waste collection networks in major cities, particularly relevant in the context of the COVID-19 pandemic. Embracing circular economy principles and sustainable city practices, the proposed model addresses the urgent need for sustainable urban bio-waste management systems. Delving into the dynamic urban landscape, with a focus on the city of Athens, the study highlights the necessity of a robust decision-making methodology, the implementation of resilient processes, and the evaluation of their efficacy, especially during challenging times. The model centers on the effective collection, transportation, and monitoring of bio-waste, with a strategic aim to moderate environmental impacts, limit greenhouse gas emissions, and advance sustainable development goals. Utilizing the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method, this paper thoroughly examines critical components of an innovative bio-waste collection network, including infrastructure, technology, and human resources. By merging best practices from global urban centers and accounting for the unique characteristics of Athens, the model envisions a transition toward a circular economy. Notably, the proposed municipal bio-waste collection network at the source anticipates substantial contributions to achieving Sustainable Development Goals in major cities. The study concludes by showcasing the successful application of these methodologies in the Municipality of Athens, providing tangible evidence of their positive impact.

Mesoporous pineapple crown-derived activated carbon modified matrix for the detection of carbendazim in the presence of anionic surfactant

Carbon paste electrodes (CPEs) are commonly employed in electroanalysis because of their chemical stability, broad electrochemical window, low capacitive current, ease of fabrication, and surface renewability. Electrocatalysts can easily be embedded into CPEs to make them suitable for a variety of applications. Poor biowaste management presents a significant challenge in the agro-industry and agriculture due to the rapid decomposition of biowaste, driven by its high water content and limited biological stability, which leads to pest attraction and greenhouse gas emissions. Consequently, this green waste can be utilized for the development of electrocatalysts. Activated carbon (AC) has been utilized in progressive electrochemical applications as it exhibits high conductivity and porosity that help to enhance electrocatalytic activity. Herein, pineapple fruit crown (PC) peel-derived AC (PCAC) is utilized as the sensing material for the determination of fungicide, carbendazim (CBM). The synthesized material was characterized using SEM, FT-IR, XRD, EDX, AFM, CV and EIS. Besides, to enhance the surface properties, Sodium dodecyl sulfate (SDS) surfactant is used as a mediator in detecting CBM. The CV and SWV approaches were employed to assess the electrochemical response of the developed electrodes for the CBM determination. Under optimum experimental conditions, the SDS/PCAC/CPE exhibits low DLim and QLim values of 32.0 nM and 128.0 nM with considerable selectivity. Furthermore, the SDS/PCAC/CPE was employed in real-time analysis of CBM in spiked environmental samples, which showed satisfying recovery results. Moreover, the electrode showed good stability over multiple measurements, and these results demonstrate that SDS/PCAC/CPE is a promising sensor for CBM detection.

Improving the biowaste management in Egypt and Jordan to mitigate methane emissions from the waste sector

Improving the biowaste management in Egypt and Jordan to mitigate methane emissions from the waste sector

Improved recovery of antioxidants from aronia juice processing residue via optimization of extraction variables based on multi-prediction models

Aronia melanocarpa, which has attracted attention for its outstanding antioxidant activity, is usually consumed as a juice, leaving considerable residue after processing into beverages. Recycling these by-products as feedstock for biorefineries is an important strategy for achieving a sustainable circular economy through biowaste management. In this study, the optimal extraction conditions for efficient antioxidant recovery from A. melanocarpa juice-processing residue (AJPR) were determined using statistical methods. Based on the Plackett-Burman design (PBD), four variables (shaking speed, solid loading, ethanol concentration, and total volume) were found to have significant effects on antioxidant extraction. The optimum points of the selected four variables were calculated by multi-regression models from response surface methodology (RSM), and the determined conditions were as follows:196.2 rpm, 71.3 g/L, 54.3% ethanol, and 137.8 mL of total volume. The DPPH• IC50 and ABTS•+ TEAC value of AJPR extracts were determined to be 2.02 mg/mL and 11.49 mg/mL, respectively, exhibiting promising potential as an antioxidant. The recovered polyphenol, flavonoid, and anthocyanin contents were 80.4, 42.5, and 14.1 mg/g-biomass, respectively. We show that bioengineering technologies can be used to achieve a circular economy by recycling discarded biowaste into value-added substances.

Biowaste management by hydrothermal carbonization and anaerobic co-digestion: Synergistic effects and comparative metagenomic analysis

The feasibility of anaerobic co-digestion in semicontinuous mode of two major urban biowaste, food waste (FW) and garden and park waste (GPW) (75 % FW and 25 % GPW) as well as the co-digestion of FW with the process water originated from the hydrothermal carbonization of GPW (95 % FW and 5 % process water), both on a COD basis, has been assessed. The effect of varying organic loading rate (OLR) from 1.5 to 3.5 g COD/L·d on methane yield, gross energy recovery, and microbiome population was evaluated. For comparison, anaerobic digestion of FW was also conducted to determine the best strategy for sustainable biowaste management. This study showed an optimal OLR of 2.5 g COD/L·d. Acetic and propionic acid content increased as OLR raised for each condition studied, while methane yield decreased at the highest OLR tested indicating overloading of the system. The anaerobic co-digestion of FW and process water showed a 10 % increase on methane production compared to anaerobic digestion of FW (324 vs. 294 mL CH4 STP/L·d). Moreover, it enhances the process due to a greater abundance and diversity of hydrolytic and acidogenic bacteria belonging to Bacterioidota, Firmicutes, and Chloroflexi phyla, as well as promotes the hydrogenotrophic pathway under higher propionic concentrations which is not usually favoured for methane production. The integration of hydrothermal carbonization of GPW with the anaerobic co-digestion of 95 % FW and 5 % of process water results in the highest potential energy recovery and could be a good strategy for sustainable management of urban biowaste.

Conversion of Sewage Sludge into Biofuels via Different Pathways and Their Use in Agriculture: A Comprehensive Review

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.