Urban Biowaste Research Articles

Innovative Circular Biowaste Valorisation—State of the Art and Guidance for Cities and Regions

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.

Recovery of carboxylic acids from actual effluent by using sequential cationic-anionic adsorption steps at semi pilot scale

This work presents for the first time an exhaustive experimental assessment at semi-pilot scale for the sequential use of cationic-anionic adsorption columns for recovering carboxylic acids (CAs) from a real fermentation broth. The consecutive steps were dedicated to i) remove cations limiting the CAs interaction with the functional group of the anionic resin, and ii) adsorb CAs onto the anionic resin, respectively. The experimental broth was obtained from anaerobic co-fermentation of urban biowaste (UBW-broth). Breakthrough (BT) tests were firstly performed with the cationic column containing the strong-acid resin Lewatit® S2568H. This allowed both to assess the single process and to prepare 60 L of decationised UBW-broth to be used in the BT-tests with the anionic column (containing the weak-basic resin Lewatit® A365). Both columns were assessed (at 25°C) under packed and expanded bed modes, by feeding at different rates the actual UBW-broth or synthetic solutions. Main study innovative outputs were: 1) 100 % of the CAs occurring in UBW-broth were recovered with the proposed system; 2) best performances were obtained under expanded bed mode of operation, allowing to use 100 % of the installed capacity; 3) the affinity of other organic matter else than CAs resulted weaker than Na+/NH4+ and CAs/PO4x-/Cl- in both cationic and anionic columns, respectively (i.e. low adsorption performances generally reported are due to inorganic cations/anions presence); 4) a very preliminary economic analysis carried out on the basis of the obtained data indicates overall costs ranging 0.58–1.49 EUR/kg of CAs (depending on the process configuration).

A Low-Cost Ecofriendly Oxidation Process to Manufacture High-Performance Polymeric Biosurfactants Derived from Municipal Biowaste.

Biosurfactants account for about 12% of the global value of the surfactant market, which is currently dominated by synthetic surfactants obtained from fossil sources. Yet, the production of biosurfactants from renewable feedstock is bound to increase, driven by the increasing pressure from both society and governments for chemistry-based industries to become more ecofriendly and economically sustainable. A photo-chemical oxidation process is reported here, yielding new biosurfactants from urban biowaste in water that perform as a solvent and terminal oxidant reagent at room temperature without the addition of conventional oxidants and catalysts. Products with 200-500 kDa molecular weight are obtained. They lower the surface tension of water down to 34 mN/m at 0.5-2 g/L concentration. The estimated cost is rather low (0.1-1.5 EUR/kg), which is competitive with the cost of synthetic surfactants but much lower than the cost of the best-performing bacterial surfactants. For the implementation of the photo-chemical oxidation process at the industrial level, the results suggest that the new biosurfactants obtained in the present work may not reach the performance level of the best-performing bacterial surfactants capable of lowering the surface tension of water down to 28 mN/m. Yet, the biosurfactants produced by the photo-chemical process have a greater chance of being marketed on large scales.

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.

Understanding the interactions between biowaste valorisation and the Sustainable Development Goals: insights from an early transition stage

ABSTRACT The valorisation of urban biowaste can contribute to a circular and sustainable resource management. However, biowaste valorisation is not inherently sustainable. This study employs the Sustainable Development Goals (SDGs) to investigate the sustainability implications of biowaste valorisation. A narrative literature review provided an overview of the current scientific knowledge on interactions between biowaste valorisation and selected SDG targets. Then stakeholder interviews yielded insights into such interactions in a national context. Our findings show the potential for 19 synergies and 11 trade-offs between biowaste valorisation and 20 selected SDG targets that are addressed in detail. Although the synergies outnumber the trade-offs, different context-dependencies influence the nature and strength of the interactions. We highlight three types of context-dependencies relating to governance. This study informs the scientific community and decision-makers on planning for sustainable biowaste valorisation that addresses context-dependencies. The insights can guide countries and cities at early transition stages towards biowaste valorisation.

Comparison of Adsorption Performance of Biochar Derived from Urban Biowaste Materials for Removal of Heavy Metals.

This study investigated the adsorption performance of biochar produced from different types of urban biowaste material viz., sugarcane bagasse (SB), brinjal stem (BS), and citrus peel (CP) for removal of heavy metal ions (Pb, Cu, Cr, and Cd) from aqueous solution. The effects of biowaste material, dosage of biochar, solution pH, and initial concentration of heavy metal ions and isotherm models were performed to understand the possible adsorption mechanisms. The results showed that the biochar derived from BS and SB removes Cu (99.94%), Cr (99.57%), and Cd (99.77%) whereas biochar derived from CP removes Pb (99.59%) and Cu (99.90%) more efficiently from the aqueous solution. Biochar derived from BS showed maximum adsorption capacity for Cu (246.31 mg g-1), Pb (183.15 mg g-1), and Cr (71.89 mg g-1) while the biochar derived from CP showed highest for Cd (15.46 mg g-1). Moreover, biochar derived from BS and SB has more polar functional groups and less hydrophobicity than the biochar derived from CP. This study reveals that solution pH and biochar doses play a major role in removal of heavy metal ions from aqueous solution. The results of Langmuir model fitted well for Pb and Cu while the Freundlich model for Cr and Cd. Our study concludes that the biochar derived from different biowaste materials adsorbs heavy metal ions majorly through surface complexation and precipitation processes. The results of this study will be very useful in selecting the effective urban biowaste material for making biochar for heavy metal removal from the aqueous environment.

Evaluation of physico-chemical and structural properties of biochar produced from pyrolysis of urban biowaste

Evaluation of physico-chemical and structural properties of biochar produced from pyrolysis of urban biowaste

ROOTS - Circular policies for changing the biowaste system.

The circular economy has a huge potential to make our societies more sustainable and decarbonised, with a reduced impact on the planet's resources.The deployment of innovative solutions in the field of urban biowaste valorisation and reuse is still hindered by numerous bottlenecks, such as technological readiness, funding and financing tools availability, quality and quantity of biowaste and regulatory barriers. The European Green Deal and associated legislative initiatives provide the opportunity to overcome the last ones. To promote innovative solutions for the European circular bioeconomy and help to overcome the barriers for the deployment of a circular bioeconomy, five Horizon 2020 projects working on biowaste valorisation have teamed up. This joint initiative is named ROOTS - circulaR pOlicies for changing the biOwasTe System.The projects HOOP, VALUEWASTE, SCALIBUR, WaysTUP! and CITYLOOPS are piloting new solutions to transform urban biowaste (food waste and green waste) and wastewater into valuable products like feed, fertilisers, bioplastics, biopesticides, proteins and bioethanol. They use different processes and technologies, but they all rely on high levels of recycling/upcycling and propose valorisation solutions relevant to the uptake of a truly circular bioeconomy. As a result of the work performed and experience acquired, a number of bottlenecks have been identified, on the following topics: biowaste prevention, recycling targets and treatment plants, waste and by-products, biopesticides, insects for animal feed, single cell protein, citizen behaviour, investment needs. For each identified bottleneck, this open letter proposes specifically 1) policy recommendations for each level of governance, and 2) information about solutions, good practices and concrete experiences from the participating projects.

Biocomposites from porcine plasma protein and urban parks and gardens green waste

Biorefinery was used to transform two organic wastes, i.e. urban park & garden green waste and porcine plasma (PPP), into raw materials for biocomposite production. The effect of the nature, size and content of the filler on the final performance of biocomposites was assessed. Two fractions stemming from an urban park and garden green waste, i.e. a representative fraction of the total waste (RF) and a branches-rich fraction (B), were considered as fillers of a PPP bioplastic. PPP-RF/B biocomposites were obtained by compression-moulding and then characterised by tensile tests, dynamic mechanical analysis, water uptake, and water vapour permeability. Using a filler size around 28 µm at 30 wt%, the Young’s Modulus of samples including B fraction was double the value of that including RF, due to the presence of grass in the overall urban waste. Moreover, a greater strengthening was perceived when using larger particle sizes (around 140 µm) of the B fraction, highlighting the importance of the grinding stage. The loss tangent evolution with temperature from dynamic mechanical tests denoted an antiplasticizing effect of the urban biowastes, which should be considered in future applications as a certain exudation degree would be expected. Regarding barrier properties, water permeability increased at higher filler contents (i.e., 30 wt%), while oxygen permeability decreased.Generally, composites from plasma and urban biowaste could be considered in future applications (e.g., packaging), as they showed great reinforcement and stability during water immersion, apart from a darker tonality and decreased oxygen permeability.

The amending potential of vermicompost, compost and digestate from urban biowaste: Evaluation using biochemical, Rock-Eval® thermal analyses and transmission electronic microscopy

Organic fraction of municipal solid waste can be recovered using a variety of processes including composting, anaerobic digestion and vermicomposting. The impact of these products was evaluated using an innovative approach combining quantitative and qualitative analyses. Chemical analysis showed that the organic matter content of dry compost, digestate and vermicompost was 76 %, 67.2 % and 41.7 %, respectively. Index of Recalcitrant Organic Carbon (IROC) was higher for vermicompost (87.2 %) than for compost (77.9 %) or digestate (66.9 %). The Rock-Eval® approach was correlated to the IROC with its R-index (R2 = 0.97). Transmission electron microscopy was used to describe the microbial activity, the decomposition state and we observed more advanced maturity from vermicompost, compost to digestate. Finally, the digestate is predicted to have a fertilizing effect whereas the compost should have more an amending effect in the medium/long term. Due to a higher degree of stability, the vermicompost could have both a fertilizing and amending effect.

Unlocking New Value from Urban Biowaste: LCA of the VALUEWASTE Biobased Products

The VALUEWASTE project can offer a sustainable solution to transform biowaste into added-value bioproducts, such as proteins from microorganisms and insects and biofertilizers. The present study focused on the environmental impacts linked to obtaining these bioproducts, which was performed by the standardized Life Cycle Assessment (LCA) approach, using the Environmental Footprint methodology to evaluate the midpoint impact categories considered. At the same time, the bioproducts coming from biowaste were compared to regular ones: other protein sources and mineral fertilizers. The study results show that these new protein sources are firm candidates to reach the market from an environmental point of view. Furthermore, their environmental impacts could be improved by reducing the energy use (the main contributor) within some impact categories, such as ecotoxicity and global warming. In case of the biofertilizers, their environmental performance was overall worse compared to mineral fertilizers, except for the following impact categories: mineral and metal use and water scarcity. Nevertheless, these biofertilizers come from biowaste, extending the circularity concept, and from local places, reducing the dependency on other actors. Hence, the study showed that the obtained bioproducts are real alternatives to implement in a circular economy. However, continuous improvement of the solution should be performed.

Removal of As(III) via adsorption and photocatalytic oxidation with magnetic Fe-Cu nanocomposites.

Magnetic Fe-Cu nanocomposites with high adsorption capacity and photocatalytic properties were prepared via the precursor method using soluble substances isolated from urban biowaste (BBS) as carbon sources and different temperatures of the pyrolysis treatment (400, 600, and 800°C). BBS is used as complexing agent for the Fe3+ and Cu2+ ions in the precursors. The as-prepared magnetic materials were tested in As(III) removal processes from water. Dark experiments performed with the materials obtained at 400 and 600°C showed excellent adsorption capacities achieving a significant uptake of 911 and 840mgg-1 for As(III), respectively. Experiments conducted under steady-state irradiation showed a reduction of 50-71% in As(III) levels evidencing the meaningful photocatalytic capacity of Fe-Cu nanocomposites. The best photocatalytic performance was obtained for the nanocomposite synthesized at the highest pyrolysis temperature, in line with the reported trend of HO· radicals production. Transient absorption spectroscopy experiments revealed the occurrence of an alternative oxidation pathway involving the valence band holes and yielded relevant kinetic information related to the early stages of the As(III) photooxidation. The higher absorption of the electron-hole pairs observed for the samples treated at lower temperature means that controlling the pyrolysis temperature during the synthesis of the Fe-Cu nanocomposites allows tuning the photocatalyst activity for oxidation of substrates via valence band holes, or via HO· radicals.

Application of DEMATEL for Barriers Analysis of Co- management of Urban Bio-wastes in Phnom Penh ,Cambodia

Application of DEMATEL for Barriers Analysis of Co- management of Urban Bio-wastes in Phnom Penh ,Cambodia

Enhanced production of aromatic hydrocarbons and phenols by catalytic co-pyrolysis of fruit and garden pruning wastes

Nowadays, urban bio-wastes (food, park and garden residues) are mainly processed into compost and biogas for energy recovery, or even directly landfilled without exploiting their potential as feedstock for valuable products. As an alternative, this work reports a comprehensive experimental study for their potential valorization via catalytic co-pyrolysis. For that, different mixtures of fruit wastes (FW), a representative component of food refuse, and garden pruning residues (GP) were co-pyrolyzed in presence of a nano-ZSM-5 zeolite (and in absence of catalyst for comparison purposes) in an ex-situ fixed-bed reactor to evaluate the occurrence of different interactions that may affect the yield and properties of the pyrolysis bio-oil* (water-free basis). All pyrolysis fractions were characterized and the composition of bio-oil* was exhaustively identified and quantified, going further than the previous works devoted to the co-pyrolysis of feedstock comprising lignocellulose and fruit wastes usually performed at microgram scale (using micropyrolysis), with intrinsic limitations in terms of the product yields and properties determination. Thus, we found that the incorporation of higher FW amounts in the feed mixture led to lower oxygen contents in the bio-oil*, improving its quality and its potential use as bio-fuel. Moreover, the bio-oil* composition was notably narrowed to marketable chemicals, both phenolic derivatives (cresols and phenol) and especially monoaromatics (mainly xylenes and trimethylbenzenes).

Urban biowaste integrated management based on synergy mechanism and multi-objective optimization: A case study in Suzhou, China

Urban biowaste is the organic fraction of municipal solid waste (MSW) and is a predominant waste type in low- and middle-income countries. Urban biowaste is the main cause of pollution and produces odor and leachate, and it could also serve as a source of energy and nutrient elements. Therefore, urban biowaste management should actuate minimal pollution, maximized resource utilization, and economic feasibility, which makes it a multi-objective problem. With increasing requirements for the classified management of MSW, the complexity of urban biowaste management is increasing, and it is necessary to consider the synergy mechanism between different wastes and technologies from a systematic perspective. We constructed urban biowaste management integrated model (UBMIM) to support urban biowaste management system design and policy formation. Firstly, a dynamic quantitative simulation of the numerical matching and influence conduction was conducted based on technology system synergy mechanism. Secondly, a multi-objective evaluation of the technology system was conducted based on material flow analysis, life cycle assessment, and project economic benefit assessment. On this basis, a multi-objective optimization algorithm was used for technology selection under high-dimensional objectives, and the long-term risks were identified and policy recommendations were made based on an uncertainty analysis algorithm. As a case study for the application research of the model, Suzhou, China, was selected, and integrated technology solutions and policy suggestions were provided for 2020 and 2025. The optimized solution can improve the system's efficiency of energy-saving and emission reduction by 14.5%–400.9% while reducing operating costs and new investments.

The Potential Contribution of Decentralized Anaerobic Digestion towards Urban Biowaste Recovery Systems: A Scoping Review

The potential contribution of decentralized approaches in implementing biowaste recovery systems has attracted interest in urban policy making and scientific research. Although the scientific literature on the topic is rapidly increasing, it is still limited and scattered. A comprehensive overview of current scientific knowledge is thus needed to support future research on decentralized options for biowaste recovery systems. Anaerobic digestion (AD) is a mature biowaste treatment technology that recovers energy and nutrients, and can close urban resource loops. Through a scoping literature review, this paper investigated decentralized AD and its potential contribution in implementing urban biowaste recovery systems. We identified opportunities and challenges for planning of decentralized AD, and concluded that these mainly concern: (a) digestate management; (b) the potential for local circularity with product valorization in outlets such as urban agriculture; and (c) the development and application of decision support tools. The findings highlighted the need to enhance scientific evidence on the impact of decentralized AD in different urban contexts. Results from published studies were highly context-specific, making it difficult to draw general conclusions. This study can support the transition to integrated planning of AD and wider urban biowaste recovery systems. Such planning must include a comprehensive analysis of configuration approaches.

Environmental and economic assessment of decentralized bioenergy and biorefinery networks treating urban biowaste

The decentralization of waste management argues to support better planning, fair distribution of material and economic resources, and increased citizen participation. This study aims at assessing the environmental and economic performance of a decentralized biowaste management system, using the frameworks of life cycle assessment and net present value analysis. Five scenarios are designed to reflect the transition from an energy-centered biowaste management (scenario 1) towards a novel biorefinery system (scenario 2) and its expansion to a decentralized network (scenarios 3, 4, and 5) of small-scale plants treating urban biowaste. The global warming potential of the energy-centered system is 134 kg CO2 eq, while the biorefinery system offers mitigation of the global warming by -4324 kg CO2 eq t−1 biowaste treated. The decentralized network designed to capture 20% of the urban biowaste generated in Lyon Metropolitan (S5) provides environmental (S5a: -1983 kg CO2 eq, S5b: -1992 kg CO2 eq) and economic (S5a: 491€, S5b: 475€) benefits, especially when collection is performed with electric bikes (S5b) and the bio-products substitute resource and energy intensive equivalents in the market. Collection with electric bikes contributes to a low-carbon economy while significantly increases labor costs. The transition towards a bio-based economy can transform biowaste management into novel cascading biorefineries of multiple high-value products. Resilient and optimized system design can support low carbon economies and increase employment while being economically sustainable.

Elucidating the key factors in semicontinuous anaerobic digestion of urban biowaste: The crucial role of sludge addition in process stability, microbial community enrichment and methane production

Anaerobic digestion, a virtuous process to reduce and reuse biowaste to obtain renewable bioenergy, is often dramatically subject to process failure during long timescale operation. This study aimed to evaluate the process robustness and reliability by elucidating the composition of microbial populations and the link with process parameters under a wide range of different operating conditions in long-term semicontinuous reactors. Mesophilic semipilot digesters were fed with real urban biowaste, namely, food waste alone or food waste with activated sludge, to explore the impact of feedstock composition and organic loading rate (OLR: 0.8–3.5 kgVSfed m−3d−1) on volatile fatty acid (VFA) composition and pattern, biomethane production, and core microbiome dynamics. The major bacterial phyla were Bacteroidetes (basically more abundant when the feedstock was only food waste), followed by Chloroflexi and Firmicutes, while Euryarcheota hydrogenotrophic methanogens, mainly represented by members of the Methanomicrobiales family, prevailed in all systems. During monodigestion of food waste, however, independent of the OLR, methanogenic conversion of fermentative end-products decreased progressively after 1 HRT. In particular, the observed propionate and butyrate accumulations seemed to derive from thermodynamic limitations due to the increase in hydrogen levels, indicative of progressively lower H2 consumption rates. However, the induced process recovery assured a large degradation of fatty acids with higher carbon chain lengths together with methane production, suggesting the upswing of hydrogenotrophic methanogen activity emerging after stressful conditions. The addition of a minimal amount of sludge boosted the methane production rates (up to 0.29 ± 0.1 Nm3CH4 kg−1VSfed) along with excellent process stability, also at a high OLR, creating a robust methanogen community shaped by high biodiversity. Methanospirillum and Candidatus Methanofastidiosum, strictly related to the codigestion systems, have a large H2 consumption capacity, thus preventing thermodynamic bottlenecks and process failure.

Redesign of urban biowaste sustainable management system based on industrial ecology concept: A case study in China

Urban biowaste, which refers to the organic fraction of municipal solid waste (MSW), is a predominant type of waste in low- and middle-income countries. Therefore, the sustainable management of urban biowaste is a key problem in solid waste management (SWM). However, treatment technologies usually come with secondary pollution and by-products that need further treatment, which would limit the economic and environmental benefits of the waste management system. The concept of industrial ecology has the potential to be introduced into the waste management field to solve this problem. Based on a practical case study of a city in eastern China, this paper conducted a complete urban biowaste treatment system planning exercise using concepts in industrial ecology. The establishment of the new system has significant economic, environmental and social benefits. The total output value of the project would reach 342 million yuan in 2025, corresponding to 945,000 tons of solid wastes consumed every year, which would significantly reduce the environmental pollution caused by solid waste. More than 700 jobs could also be created. In addition, the establishment of an urban biowaste sustainable management system requires the joint effort of enterprise, government and the public, which in turn requires innovation in business models and management policies. Therefore, a special management committee should be established to promote collaboration among stakeholders, and an online platform that enables end-to-end process supervision covering the entire system, including emergency management mechanisms, needs to be established to ensure the long-term stable operation of various treatment facilities. The results of this paper show that synergies among technologies should be promoted to provide systemic benefit, and that the infrastructure for pollution control should be shared to ensure high utilization.

Volatile fatty acid platform - a cornerstone for the circular bioeconomy.

Annually, the EU produces more than 100 million tonnes of urban biowaste, which is largely under-valorized and in some cases even still landfilled without any energy or material recovery. If Europe wants to be ready for the future, it will need to make better use of this large biomass potential within a circular economy approach. The research project funded by the European Commission under the Horizon 2020 programme entitled 'VOLATILE-Biowaste derived volatile fatty acid platform for biopolymers, bioactive compounds and chemical building blocks' aimed to produce volatile fatty acids (VFAs) from biowaste for reprocessing into products, materials or substances to close the material loop. During the project, the partners were able to obtain average volatile fatty acid yields of 627g COD/kg organic matter (OM) for food waste, 448g COD/kg OM for separately collected vegetable, garden and fruit waste (VGF) and 384g COD/kg OM for the organic fraction of municipal solid waste (OF-MSW) at concentrations ranging from 12 to 48g/L, 6 to 40g/L and 13 to 26g/L, respectively. A membrane filtration cascade consisting of micro-, ultra- and nano-filtration followed by reverse osmosis was identified as a feasible way to purify and concentrate the VFA effluent, making them a suitable carbon source for further fermentation processes. Besides technical optimization, socio-economic and legal aspects associated with this platform technology were also studied and show that although this technology is still in development, it is providing an answer to changing societal and market expectations both regarding organic waste treatment and bio-based production strategies. Based on the current technological, economic and market evolutions, it is expected that the VFAP will play an important role in organic waste treatment in the coming years.