Effects of Biowaste-Derived Hydrochar on Anaerobic Digestion:Insights into Hydrochar Characteristics

Hydrochar prepared with four typical biowastes,pine wood,food waste,digested sewage sludge,and Chlorella were applied for the promotion of anaerobic digestion.The gas production and substrate composition were analyzed associated with the hydrochar characteristics.The results suggested that Chlorella hydrochar(C-C)showed the highest cumulative yield of methane(approximately 345 mL)with high total organic carbon(TOC)removal efficiency and low volatile fatty acids(VAFs)concentration.Especially,food waste hydrochar(F-C)showed a poor effect on anaerobic digestion and aroused 1.4–1.6 g/L accumulation of VAFs,in which the toxic components may account for the low efficiency.The C-C and sludge hydrochar(S-C)may develop direct interspecific electron transport(DIET)to facilitate the generation of methane by both surface groups and conductivity of the body structure,unlike pinewood hydrochar(P-C),which mainly depended on the aromatic matrix structure of hydrochar body.This work suggested that C-C can be the best candidate for the facilitation of anaerobic digestion,and N-containing biowaste like algae and lignocellulose like pine wood may establish different DIET pathways based on the physicochemical characteristics of hydrochar.

Studies of Adsorption of Cadmium Ions by Biowaste Adsorbent from Aqueous Solutions with Ion-Selective Electrodes and ICP-OES

Using environment-friendly and low-cost biowaste adsorbents as toxic metal ion removal substrates from aqueous solutions has a great economic advantage. This work evaluated pumpkin and potato peel biowastes for the adsorption of cadmium ions. The biowastes were treated with acid or base. Batch experiments were carried out by introducing a known concentration of metal ion solution into the biowaste sorbent at various pH levels. The pH and metal ion concentration was monitored with pH and cadmium ion-selective electrode continuously for two hours, and the final concentration for the metal ion after 24 hours was measured with the cadmium electrode and then confirmed with ICP-OES. L-type isotherms were obtained that fit to Freundlich model. Adsorption isotherms showed chemical adsorption and the kinetics following the second order model. Equilibrium adsorption capacity is higher than 29 mg/g at pH 5.6 when the initial concentration is 220 ppm. Dynamic cadmium adsorption capacity is 17 mg/g from aqueous solution when the feed solution is 220 ppm with pumpkin peel biowaste sorbent. The biowaste materials can be regenerated with acid washing.

Production of Hydroxylapatite from Biowaste, Chicken Manure by Hydrothermal Process

Hydrothermal process has been applied for effective production of Hydrogen from biowastes. In this study hydrothermal process for production of valuable Hydroxylapatitefrom chicken manure containing phosphorus was focused on. Conditions of 400?C and 26 - 27 MPa with addition of 1 mmol Ca(OH)2 were determined as the optimal by using O-phospho-DL-serine as a model compound. Afterwards, the real biowaste containing phosphorous, chicken manure was processed under the same conditions. Formation of a Hydroxylapatite;in the solid residue was confirmed from X-ray diffraction (XRD) patterns, after purification. It was found that 27.9% of P in the chicken manure was converted to Hydroxylapatite. With the use of acetic acid as a chemical purification medium, Hydroxylapatite was obtained.

Pd nano-catalyst supported on biowaste-derived porous nanofibrous carbon microspheres for efficient catalysis

Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibly to valuable compounds. Therefore, the design of efficient, stable and long-lifetime catalysts is a worthwhile research goal. Herein, we used nanofibrous carbon microspheres (NCM) derived from the carbohydrate chitin present in seafood waste, and characterized by interconnected nanofibrous networks and N/O-containing groups, as carriers for the manufacture of a highly dispersed, efficient and stable Pd nano-catalyst (mean diameter ca. 2.52 nm). Importantly, the carbonised chitin’s graphitized structure, defect presence and large surface area could promote the transport of electrons between NCM and Pd, thereby endowing NCM supported Pd catalyst with high catalytic activity. The NCM supported Pd catalyst was employed in the degradation of some representative dyes and the chemoselective hydrogenation of aromatic aldehydes;this species exhibited excellent catalytic activity and stability, as well as applicability to a broad range of aromatic aldehydes, suggesting its potential use in green industrial catalysis.

A Self-growing Porous Calcium-based Adsorbent Derived from Biowaste for Efficient Wastewater Purification

Traditional adsorbents are normally suffered from a low adsorption capacity that has a finite saturated adsorption capacity. We reported herein a hierarchical self-growing porous calcium silicate hydrate(CSH) that uses biowaste as the precursor and is highly efficient in wastewater purification. In the process of phosphorus removal, CSH can react with phosphorus in water and grow into the hydroxyapatite(HAP). The generation of HAP further increases the active sites while maintains the porous structure of pristine CSH. Subsequently, the HAP could conduct the efficient extraction of Pb^(2+) from wastewater based on the ion exchange between Ca^(2+) and Pb^(2+). Clearly, the CSH structure has self-growing structure using the pollutants as the building blocks, not only achieving high adsorption capacity for pollutants, but also maintaining the hierarchically porous structure that supports the high efficiency in the next cycling. We provide here an intriguing pathway to tackle bottleneck of the traditional adsorbents, i.e., a finite saturated adsorption capacity.

Low cost, high performance supercapacitor electrode using coconut wastes: eco-friendly approach

Low cost, high performance supercapacitor electrodes were fabricated using coconut waste as precursor. Simple one step pyrolysis is adopted to get the spherical shaped particle where lignocellulosic nature of carbon converts into porous carbon nanospheres. Three types of coconut wastes, namely, coconut fiber(CF), coconut leaves(CL) and coconut stick(CS) have been studied and compared for their application in supercapacitors. Uniform spherical shape with particle size ranging from 30 to 60 nm for leaves and sticks and20 nm for fibers was obtained. The electrochemical properties of the porous carbon nanospheres were studied using cyclic voltammetry(CV), chronopotentiometry(CP) and electrochemical impedance spectroscopy(EIS). The porous carbon nanospheres derived from all the three biowaste samples show good electrochemical performance for supercapacitor application. Porous carbon nanospheres derived from coconut fiber exhibited maximum specific capacitance of 236 F/g followed by coconut stick and coconut leaves with 208 and 116 F/g respectively at a scan rate of 2 m V/s. Further impedance studies showed a charge transfer resistance of 4.9 for the porous carbon nanospheres derived from coconut fiber, while those from coconut leaves and coconut stick exhibited a slightly higher resistance of 6 and14.2, respectively. The simple eco-friendly approach we have demonstrated for synthesizing coconut waste based carbon nanospheres makes them excellent candidates for future, low-cost, energy storage devices.

Superior supercapacitive performance in porous nanocarbons

Porous nanocarbons with average particle size 20–40 nm were developed using biowaste oil palm leaves as a precursor.Simple pyrolysis was carried out at 700 °C under nitrogen atmosphere.Obtained porous nanocarbons showed excellent porous nature along with spherical shape.Symmetric supercapacitor fabricated from porous nanocarbons showed superior supercapacitance performance where high specific capacitance of 368 F/g at 0.06 A/g in 5 M KOH were reported.It also exhibited high stability(96% over 1700cycles) and energy density of 13 Wh/kg.Low resistance values were obtained by fitting the impedance spectra,thus indicating the availability of these materials as supercapacitors electrode.The presented method is cost effective and also in line with waste to wealth approach.

Differential metabolome landscape of Kadsura coccinea fruit tissues and potential valorization of the peel and seed tissues

Kadsura coccinea(Lem.)is a woody wine plant with a peculiar fruit enriched in important health-promoting compounds.The non-editable part of the fruit,i.e.,the seed and peel,represents more than 60%of the fruit and is considered a biowaste.This significantly restricts the development of the K.coccinea fruit industry.Clarifying the metabolic components of the different fruit parts can help to improve the utilization rate and valorization of K.coccinea.Herein,we evaluated K.coccinea fruit peel,pulp,and seed using widely-targeted metabolomics and quantified a set of 736 bioactive compounds from 11 major metabolite classes.The most prominent metabolite classes included lipids,amino acids,flavonoids,and lignans.Furthermore,our results emphasized a significant accumulation of flavonoids in pulp tissues,while alkaloids and lignans were abundant in peel and seed tissues,respectively.A total of 183 metabolites were differentially accumulated among the three tissues.Procyanidin C2,rutinoside,2-hydroxyoleanolic acid,5-hydroxymethyluracil,nootkatol,isoquercitrin,isohyperoside,quercetin-7-O-glucoside,hyperin,and rutin showed elevated accumulation in the peel.In the seed,kadsuralignan G,kadcoccilactone A,kadsuralignan H,lysoPE 20:5,iso-schisandrin ethyl alcohol,and kadangustin were significantly enriched.Our results highlight the diverse metabolome composition of K.coccinea fruit parts,which can be further exploited for its valorization in various industries.

Conversion of Waste Parasitic Insect(Hylobius abietis L.)into Antioxidative,Antimicrobial and Biodegradable Films

Hylobius abietis is a plant parasitic insect belonging to the order Coleoptera and which causes severe damages to coniferous forests in Northern and Eastern Europe.This current study is aimed to provide a new viewpoint into the waste of this insect by producing chitosan.Dry insect corpses consisted of 27.9%chitin and 86.2%of the chitin was converted into the chitosan.FT-IR spectra analyses confirmed the purity and the deacetylation degree of the produced chitosan(molecular weight of chitosan;7.3 kDa).This chitosan exhibited antimicrobial activity against 18 bacterial strains.Further,biodegradable chitosan composite films with β-carotene were produced.Antioxidant activity of chitosan films were found to be higher than chitosan gels;andβ-carotene incorporation further increased the antioxidative properties of the chitosan films.This study demonstrated that the waste of parasitic insect like H.abietis can be evaluated as a source for production of biodegradable and edible chitosan-based films for applications in food coating.

Green Bio-Based CaO from Guinea Fowl Eggshells

Eggshells are among the emerging hazardous waste from the food processing industry. This work sought to valorize waste guinea fowl eggshells. Guinea fowl eggshells (GFEs) were evaluated in the production of CaO for chemical and industrial application. The functionality, thermal stability, elemental composition, phase distribution and surface morphology properties of uncalcined GFEs and GFEs calcined at 700°C, 800°C, 900°C, 1000°C and 1100°C were systematically studied by FTIR, TGA, XRF, XRD and SEM-EDX respectively. The elemental analysis revealed Ca as the main element in the GFEs. The uncalcined GFEs showed intense peaks that corresponded to calcite (CaCO3) phases. These transformed into Ca(OH)2 as the temperature of calcination increased and finally to CaO in the FTIR analysis. In the XRD diffractograms, the main peaks at 2θ values were 29.466° for the uncalcined GFESs and at 37.377° for the sample treated at 1100°C. The phases were confirmed as CaO when compared with JCPDS files. Using the Scherer equation, the CaO crystallite size for the sample calcined at 1100°C was found to be 50.68 nm along the (2 0 0) orientation. All the samples showed multi-step decomposition patterns in the thermogravimetric analyses (TGA), with weight loss of up to 47% for the uncalcined GFEs sample, which was mainly due to the transformation of the calcite (CaCO3) phase to CaO by removal of bound water, organic components, and CO2. Samples calcined at 1100°C showed mainly CaO phases in XRD analyses and fairly stable with 7% loss in weight after treatment at 800°C. SEM images of samples calcined at 900°C were irregular compared to samples treated at 1100°C. EDX data revealed that the surface structure was 100% calcium and oxygen. GFEs are a potential source of pure calcium oxide for various industrial uses.

Application of Black Soldier Fly Frass, Hermetia illucens (Diptera: Stratiomyidae) as Sustainable Organic Fertilizer for Lettuce, Lactuca sativa Production

In recent years, black soldier fly (BSF) has been shown to efficiently convert organic waste into nutrient-rich larval biomass while generating frass as the main by-product. This work aims to investigate the potential of BSF frass (BSFF) as an organic fertilizer for agricultural production. BSFF was produced by recycling household waste using BSF larvae, and a portion was taken to the lab for physicochemical and microbial analyses before the field trial on lettuce growth and health. The field trial consisted of two doses of BSFF (15 t·ha-1 and 30 t·ha-1) and one dose of urea (0.214 t·ha-1). An unfertilized plot was prepared and used as a control, and the effects on lettuce growth were assessed using agronomic parameters while the health effects were assessed using parameters such as: the number of leaves affected per plant, the incidence of affection, the severity of the affection and the microbial analysis. BSFF exhibited acceptable physicochemical properties as an organic fertilizer. Its application improved the growth parameters of lettuce plants compared to urea and control. The application rates of 15 t·ha-1 and 30 t·ha-1 did not reveal any significant difference (p > 0.05). Further studies are therefore needed to determine the minimum applicable dose. The health parameters of the lettuce plants were slightly altered regardless of the treatment and the microbial analysis of the affected leaves revealed pathogenic microorganisms. We therefore recommend that decontamination methods be considered when producing BSFF as an organic fertilizer.

Biochars derived from carp residues:characteristics and copper immobilization performance in water environments

Heavy metal pollution has attracted worldwide attention because of its adverse impact on the aquatic environment and human health.The production of biochar from biowaste has become a promising strategy for managing animal carcasses and remediating heavy metal pollution in the aquatic environment.However,the sorption and remediation performance of carp residue-derived biochar(CRB)in Cu-polluted water is poorly understood.Herein,batches of CRB were prepared from carp residues at 450–650℃(CRB450–650)to investigate their physicochemical characteristics and performance in the sorption and remediation of Cu-polluted water.Compared with a relatively low-temperature CRB(e.g.,CRB450),the high-temperature biochar(CRB650)possessed a large surface area and thermodynamic stability.CRB650 contained higher oxygen-containing functional groups and P-associated minerals,such as hydroxyapatite.As the pyrolytic temperature increased from 450 to 650℃,the maximum sorption capacity of the CRBs increased from 26.5 to 62.5 mg/g.The adsorption process was a type of monolayer adsorption onto homogenous materials,and the sorption of Cu^(2+)on the CRB was mainly based on chemical adsorption.The most effective potential adsorption mechanisms were in order of electrostatic attraction and cation-πinteraction>surface complexation and precipitation>pore-filling and cation exchange.Accordingly,the CRBs efficiently immobilized Cu^(2+)and reduced its bioavailability in water.These results provide a promising strategy to remediate heavy metal-polluted water using designer biochars derived from biowastes,particularly animal carcasses.

Bioplastic production in terms of life cycle assessment:A state-of-theart review

The current transition to sustainability and the circular economy can be viewed as a socio-technical response to environmental impacts and the need to enhance the overall performance of the linear production and consumption paradigm.The concept of biowaste refineries as a feasible alternative to petroleum refineries has gained popularity.Biowaste has become an important raw material source for developing bioproducts and biofuels.Therefore,effective environmental biowaste management systems for the production of bioproducts and biofuels are crucial and can be employed as pillars of a circular economy.Bioplastics,typically plastics manufactured from bio-based polymers,stand to contribute to more sustainable commercial plastic life cycles as part of a circular economy in which virgin polymers are made from renewable or recycled raw materials.Various frameworks and strategies are utilized to model and illustrate additional patterns in fossil fuel and bioplastic feedstock prices for various governments'long-term policies.This review paper highlights the harmful impacts of fossil-based plastic on the environment and human health,as well as the mass need for eco-friendly alternatives such as biodegradable bioplastics.Utilizing new types of bioplastics derived from renewable resources(e.g.,biowastes,agricultural wastes,or microalgae)and choosing the appropriate end-of-life option(e.g.,anaerobic digestion)may be the right direction to ensure the sustainability of bioplastic production.Clear regulation and financial incentives are still required to scale from niche polymers to large-scale bioplastic market applications with a truly sustainable impact.

Two-step hydrothermal conversion of biomass waste to humic acid using hydrochar as intermediate

Converting biomass materials to humic acid is a sustainable method for humic acid production and achieve biomass valorization. A two-step hydrothermal treatment method was adopted in this study to produce humic acid from corn stalks. In the first step of the process, hydrochar was prepared at different hydrothermal temperatures and pH values. Their chemical properties were then analyzed, and the hydrochar-derived humic acids were produced under alkaline hydrothermal conditions (denoted as HHAalk). The hydrochar, prepared under high temperature (200 °C) and strong acidic (pH 0) conditions, achieved high HHAalk yields (i.e., 67.9 wt% and 68.8 wt% calculated based on weight of hydrochar). The sources of HHAalk formation were as follows: 1) production in the hydrochar preparation stage, and 2) increment under the alkaline hydrothermal treatment of hydrochar. The degree of hydrochar unsaturation was suggested as an indicator for evaluating the hydrochar humification potential under alkaline hydrothermal conditions. This study provides an important reference for the preparation of suitable hydrochar with high hydrothermal humification potential.

Effect of airflow on biodrying of gardening wastes in reactors

Biodrying consists of reducing moisture by using the heat from aerobic bio-degradation.The parameters that control the process are：aeration,temperature during the process,initial moisture of biowaste,and temperature and relative humidity of the input air.Lawn mowing and garden waste from the gardens of the University Jaume I,Castellón（Spain）were used as a substrate.Biodrying was performed in 10 reactors with known air volumes from 0.88 to 6.42 L/（min·kg dry weight）.To promote aeration,5 of the reactors had 15% of a bulking agent added.The experiment lasted 20 days.After the experiments it was found that the bulking agent led to greater weight loss.However,the increased airflow rate was not linearly proportional to the weight loss.

Biogas and its opportunities——A review

Biogas production is a well-established technology primarily for the generation of renewable energy and also for the valorization of organic residues. Biogas is the end product of a biological mediated process, the so called anaerobic digestion, in which different microorganisms, follow diverse metabolic pathways to decompose the organic matter. The process has been known since ancient times and was widely applied at domestic households providing heat and power for hundreds of years. Nowadays, the biogas sector is rapidly growing and novel achievements create the foundation for constituting biogas plants as advanced bioenergy factories. In this context, the biogas plants are the basis of a circular economy concept targeting nutrients recycling, reduction of greenhouse gas emissions and biorefinery purposes. This review summarizes the current state-of-the-art and presents future perspectives related to the anaerobic digestion process for biogas production. Moreover, a historical retrospective of biogas sector from the early years of its development till its recent advancements gives an outlook of the opportunities that are opening up for process optimisation.

Flow fuel cell powered by combustible agricultural waste

Combustible agricultural waste is a potential source of energy because of its high organic content and heating value.As China’s economy develops,energy demand increases while environmental protection becomes more stringent.These competing demands make it urgent to find environmentally acceptable ways to extract energy from agricultural wastes.In this study,a liquid catalyst flow fuel cell(FFC)directly powered by combustible agricultural waste is investigated.This type of flow fuel cell can directly convert combustible agricultural waste at atmospheric pressure to electricity at 80-150℃and it is environmentally friendly.Polyoxometalates act as catalysts and charge carriers to drive the FFC.Wheat straw and wine residues were used to represent the main components of combustible agricultural waste.Experiment results indicated that the power density reached as high as 111 mW/cm^(2),hundreds of times higher than the output of a microbial cell.

Raw material of water-washed hydrochar was critical for the mitigation of GHGI in infertile paddy soil:a column experiment

Water washing is a meaningful method to improve the surface’characteristic of hydrochar produced using hydrothermal carbonization and minimize the negative effect on crop growth.However,the greenhouse effect resulting from water-washed hydrochar application was unclear in agricultural ecosystems.Hence,the effect of water-washed hydrochar on methane and nitrous oxide emissions was analyzed in an infertile paddy soil based on a soil-column experiment.Sawdust-derived hydro-char(WSH)and wheat straw-derived hydrochar(WWH)after water washing were selected and applied with low(5‰,w/w;8.5 t ha^(−1))or high addition rate(15‰,w/w;25.5 t ha^(−1)).The study indicated that water-washed hydrochar could increase the grain yield;the difference between WWH with 5‰application rate and CKU treatments was significant.WSH signifi-cantly decreased CH4 and N2O emissions in comparison with WWH addition treatments.For the same material,there were trends in reducing greenhouse gas(GHG)emissions at low application rate,although the differences were not significant.Compared with all treatments,WSH with 5‰application rate achieved the lowest seasonal emissions for both GHGs.The mcrA gene was the critical factor affecting CH4 emission;soil NO_(3)^(−)-N concentration and the copy numbers of nirK,nirS,and nosZ jointly affected N2O emissions.Benefits from the high yield and low global warming potential,GHG emission intensity(GHGI)at low application rate was lower than at high application rate for WSH.Overall,the response of GHG emissions to water-washed hydrochar varies with the derived feedstock;WSH is a good additive for the mitigation of GHGI.