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The production of human-generated wastes is increasing with the rise in the world’s population. Under this scenario, sustainable management of large quantities of waste is becoming an increasingly challenging task. The present study carried out the anaerobic co-digestion of food waste (FW), human feces (HF), and toilet paper (TP) to evaluate its potential for use in the on-site treatment of household organic wastes. The biochemical methane potential (BMP) was determined for these wastes and their mixtures, confirming the effective methanation of each substrate and its mixtures, with FW showing significantly higher BMP than HF or TP. Response surface analysis of the BMP data successfully produced two models describing the effect of the substrate mixing ratio on the overall methane yield and the synergistic effect of co-digestion (in terms of methane yield). The obtained models revealed that methane yield and the synergistic effect of co-digestion are influenced in different ways by variations in the substrate mixing ratio. Importantly, the effect of interactions between individual substrates is not substantial in magnitude regardless of the substrate mixture composition (synergy index close to 1). This indicates that FW, HF, and TP can be co-digested without compromising the overall methane yield (i.e., no antagonistic effect) at any desired substrate mixing ratio, which makes the application of co-digestion in the field more flexible. The overall results suggest that anaerobic co-digestion is a feasible means for the on-site treatment and valorization of mixed FW, HF, and TP, the major household organic wastes.

Co-incineration with municipal solid waste (MSW) is an efficient method in disposal of paper sludge (PS). CFD technology was adopted to verify the possibility of different blending ratio of sludge to combust with MSW in a 750 t/d waste incinerator, and to predict the impact of different moisture content of sludge on co-combustion. In this paper, the reliability of the numerical model is verified by comparing predicted results with operating data; the sludge which contain 30%, 40%, 50%, 60% and 67% moisture content were blended with MSW by the mass proportion of 5% (wet basis, the same below), 10%, 15%, 20% and 25%. The simulation shows that mass residual on bed increases from 19.8% to 27.6% with the mass percentage of sludge rising from 5% to 25%; as the moisture content in sludge increased, the volatiles release and fixed carbon burning are both delayed. The solid gasification efficiency has a negative correlation with blending ratio of sludge and moisture content of sludge. The NO emission is observed to be positively correlated to the percentage of sludge and the highest is not higher than 162 mg/Nm3. Raw paper sludge with high content of water will aggravate coking and corrosion on rear flue wall because of local high temperature. The result indicates that co-combustion of 25 wt% sludge (up to 67% moisture) with MSW is feasible which maintains the furnace temperature, mass residual and several pollutants in allowable range. However, partially dried paper sludge is more proper for incinerator in the consideration of mitigating corrosion. The current work greatly help to understand the effect of paper sludge and its moisture content in large-scale waste incinerator.

The current study investigated an integrated fermentation process for efficient conversion of pulp and paper sludge (PPS) material to bio-ethanol. To achieve maximum yield of reducing sugar from the pretreated PPS, most influencing parameters such as enzyme dosages, surfactant dosages on PPS loadings were optimized in a batch saccharification process using response surface methodology. The experimental validation studies under optimal conditions of 6% (w/w) solid loading condition, 0.16% (w/w) of surfactant concentration and 158 FPU/gm of enzyme loading resulted in a maximum reducing sugar yield of 45 ± 3.75% (w/w). Separate batch saccharification studies were conducted with 4% to 7% (w/w) solid loading to formulate best operating conditions for fed-batch saccharification with 13% (w/w), 18% (w/w) and 22% (w/w) high solid loading. The PPS solid loading of 18% (w/w) in fed-batch saccharification resulted in maximal release of glucose and xylose of 79.56 g/L and 8.65 g/L respectively at 60 h. Further improvement in the conversion of PPS to bioethanol was established through adoption of fed-batch semi-simultaneous saccharification and co-fermentation (S-SSCF) process. Fermentation using co-cultivation of two yeast species namely P. stipitis NCIM 3499 and Baker’s yeast resulted in maximum ethanol concentration of 42.34 g/L with 0.53 g/g yield from 18% (w/w) solid loading. Thus, the current study demonstrated the potential application of PPS waste as a feedstock material for ethanol production, which can be adopted by industries as an environment-friendly alternative to common solid waste management.

The deinking ability of chitosan-based particles in the pretreatment of recycling paper was studied. All these polymers were able to adsorb carbon black as ink pigment. Amount of adsorbents, contact time, solution pH and temperature were optimized to estimate maximum sorption capacity of polymers. The optimum condition of carbon black adsorption was achieved using chitosan-coated Ca-alginate beads at 30 min, 35 °C, pH 6.5 and 220 rpm of agitation speed. The adsorption capacity was more than 80%. Packed-bed reactor filled with chitosan-coated alginate beads was conducted and operated under the optimal conditions. More than 95% of ink was adsorbed onto carriers after 20 h. Saccharification with industrial enzyme preparation of deinked paper pulp was carried out and sugars released were converted into ethanol. The results of alcoholic fermentation confirmed the success of the deinking process. Our results are very promising in the development of pretreatment technology to enhance the efficiency of the utilization of recycling paper.

In this study, ozonation (OZN) combined consortium of hydrolytic enzymes (CE) method was studied for augmenting anaerobic biodegradability (ABD) of pulp and paper industry waste (PPMW) biosolid. Initially, OZN method was performed by varying ozone dosage and pretreatment time. A higher lysis rate and suspended solids (SS) reduction were noticed respectively to be 20% and 15% at an optimized ozone dosage (0.04 g/g TS) and pretreatment time (24 min). For further enhancing PPMW biosolid disintegration, OZNCE method was proceeded with respect to CE dosage and pretreatment time at an optimized ozone dosage (0.04 g/g TS). At 10% v/v CE dosage and 15 min pretreatment time, maximum of lysis rate (31%) and SS reduction (23.5%) were achieved. The pretreated biosolids were subjected to ABD assay in which OZNCE method obtained higher methane gas production potential of 324 L/kg VS. Also, cost analysis was done, which revealed that OZNCE method obtained a net profit of 15 $ per ton of PPMW biosolid.

The current study was designed to isolate and identify superior cellulose-degrading fungi from Egyptian soils reached with cellulosic compounds, then production of bioethanol from paper wastes using this isolate. Among 9 fungal isolates, one isolate was selected as the highest cellulases producer. This isolate was identified by morphological and genetic characteristics as Aspergillus niger MK543209. Basal mineral salt medium amended with 1% rice straw was the best medium for cellulose-degrading enzymes production under submerged fermentation (SmF). Additionally, bagasse at 30% and urea at 2% were the best carbon and nitrogen sources, respectively. In respect to the environmental conditions, the optimum temperature, pH and incubation period were 45 °C, 5.5 and 4 days, respectively. The optimized conditions were applied to produce reducing sugars from paper wastes, followed by production of bioethanol as a renewable energy. A 0.9 g/l/h of ethanol were produced as the best value. This study may be considered the initial point for production of renewable energy and protection of environment from wastes.

Crude oil samples contain several types of contaminants including metalorganic compounds, sulfur containing compounds and sediments. Energy dispersive X-ray fluorescence spectrometry was used for the direct determination of S, Ca, Fe, Ni and V in crude oils, enabling a fast and reliable method that avoids complex sample preparation. Crude oil samples were homogenized and 20 μL of a diluted sample (1/1 v/v oil/toluene) were placed in the center of a 10 mm diameter filter paper that was sandwiched between two polypropylene film foils and attached to the instrument cell for measurements. For the purpose of matrix corrections, fixed amounts of H, N and O were introduced in the calibration model with C (achieved through elemental analysis) used to balance the matrix content. Quantification was made by fundamental parameters method using ASTM proficiency test samples to perform mathematical adjustment of the analytical model. The results for metals were statistically comparable to the ones obtained by flame atomic absorption spectrometry while the ones for S were in accordance to the results achieved in ASTM proficiency programs and achieved by elemental analysis. Ca, Fe, Ni and V were directly determined in the oil at concentrations as low as 1 μg g −1 and for S, the value was 0.002% w/w, showing the potential of the proposed method to screen for samples with higher amounts of these critical contaminants.

Waste paper has a potential to serve as renewable feedstock for the biorefineries of fuels, chemicals and materials due to rich in cellulose and its abundance at low cost. In the present study, pretreated waste office paper (WOP) was enzymatically hydrolysed and used for lipid production by Cryptococcus curvatus. The results suggested that the WOP hydrolysate supplemented with ammonium sulphate (2 g/L) and yeast extract (0.5 g/L) as nitrogen source at a C/N ratio of 80 were the most suitable for high yield of lipids. The biomass, lipid yield, lipid content and lipid coefficient achieved from batch cultivation of C. curvatus using untreated and pretreated WOP hydrolysates were 6.32 and 15.20 g/L, 1.39 and 5.75 g/L, 22 and 37.8%, and 99.9 and 234.6 mg/g sugar with the productivity of 0.02 and 0.08 g/L/h, respectively. The fatty acid profile of the lipids indicated that the oleic acid was the major fatty acid followed by palmitic acid, stearic acid and linoleic acid which is quite similar to plant/vegetable oils. Thus, the results suggested that the waste office paper could be an alternative feedstock for production of microbial lipids for biodiesel.

A commercially available GDL based on carbon paper or carbon cloth as a macroporous substrate was characterized by various physical and electrochemical measurements: mercury porosimetry, surface morphology analysis, contact angle measurement, water permeation measurement, polarization techniques, and ac-impedance spectroscopy. SGL 10BB based on carbon paper demonstrated dual pore size distribution and high water flow resistance owing to less permeable macroporous substrate, and more hydrophobic and compact microporous layer, as compared to ELAT-LT-1400 W based on carbon cloth. The membrane-electrode-assembly fabricated using SGL 10BB showed an improved fuel cell performance when air was used as an oxidant. The ac-impedance response indicated that a microporous layer which has high volume of micropores and more hydrophobic property allows oxygen to readily diffuse towards the catalyst layer due to effective water removal from the catalyst layer to the gas flow channel.

The possibility of co-processing paper sludge with coal in power plants for power production and useful products was investigated as an alternative to the disposal option. The thermal behaviour of the fuels and their blend during pyrolysis and combustion processes was studied, kinetic models were developed and the compatibility of each component in the blend was evaluated. The experiments were conducted in a thermogravimetric analysis system, at non-isothermal heating conditions, over the temperature range 25–850 °C. The effect of the inorganic constituents of the fuels and their mixture on thermal conversion characteristics, reactivity, slagging and fouling propensities and environmental pollution was examined. The thermochemical reactivity of the two fuels was different in both nitrogen and air. Devolatilization of paper sludge occurred earlier and with a higher rate, while its combustion was hindered by the high content of ash. When the two fuels were mixed their pyrolysis or combustion reactivities did not substantially change. A first-order parallel reactions model for pyrolysis and a power low model for combustion fitted the experimental results accurately. The kinetic parameters of the blend could be predicted from the data of the individual components. Co-firing paper sludge with subbituminous coal might somehow improve the slagging/fouling potential of the coal. However, if the mineral matter of paper sludge is partly removed before use, then the combustion behaviour of the mixture could resemble that of coal alone and the overall efficiency of the process would increase.

Uncoated printing and writing paper, one of the principal waste papers in Taiwan, was pyrolyzed with a thermogravimetric analysis (TGA) reaction system. The pyrolysis experiments were carried out in nitrogen environment at a constant heating rate of 5 K min −1 . The gaseous products and the residues were collected at room temperature (300 K) and analyzed by gas chromatography (GC) and elemental analyzer, respectively. The major gaseous products investigated included non-hydrocarbons (H 2 , CO, CO 2 , and H 2 O) and hydrocarbons (C 1–3 , C 4 , C 5 , C 6 , 1-ring, C 10–12 , levoglucosan, C 13–15 , and C 16–18 ). The cumulated masses and the instantaneous concentrations of gaseous products were obtained under the experimental conditions. The yields of non-hydrocarbon gases and of hydrocarbon gases were about 10.46 and 0.49% at 623 K, 33.68 and 0.89% at 700 K, 64.52 and 1.05% at 788 K, and 79.10 and 1.63% at 938 K, respectively. The estimation of the mass of tar, yielded at various pyrolysis temperatures was also made. The results of this study might be useful for the design of pyrolysis process as well as for determining the pyrolysis mechanisms of the uncoated printing and writing paper.

The pyrolysis kinetics of cellulosic coated printing and writing paper, a principal component of municipal solid waste (MSW) in Taiwan, were investigated by thermogravimetric analysis in nitrogen over the temperature range 450–900 K at heating rates of 1, 2 and 5 K min−1. The t.g.a. curves indicated two principal reactions, distinguished by significant and distinct mass changes over the experimental range. The pyrolysis of coated paper could be adequately described by a two-reaction model. The corresponding activation energies, pre-exponential factors and reaction orders were determined. The experimental results were satisfactorily fitted by the proposed model.

Ignition behaviour of combustible wastes from the pulp and paper industry was studied in a modified thermogravimetric furnace. Criteria for ignition and the ignition mechanism were developed. The ignition of combustible wastes was predominantly homogeneous. The influence of different factors, such as particle size, sample type, heating rate and oxygen concentration, was studied. In general, no monotonic relationship between ignition temperature and particle size was observed. Different types of sample had different ignition temperatures (ranging from 203 to 227°C). The ignition temperature increased with heating rate but decreased with oxygen concentration. The combustible waste samples were collected and morphologically analysed at different stages of the heating process. No significant differences in morphology were observed just before and after ignition. The results obtained are useful in identifying the region for injection of combustible wastes into industrial combustors (e.g. boilers or fluidized beds).

This second paper in a series describes results of pilot-scale testing for mercury (Hg) removal from coal combustion flue gas using a scrubbing solution based on the Fenton reactions. The selected reagents contain hydrogen peroxide and iron salts. The mercury scrubbing was performed in a condensing heat exchanger (CHX) with flue gas generated by coal combustion in CANMET’s vertical combustor research facility (VCRF). Both the Ontario Hydro method and a Hg CEM were used for Hg sampling and speciation. The results, obtained with the combustion of three different pulverized coals – bituminous, sub-bituminous and lignite – showed that the CHX was very effective in removing oxidized mercury (Hg(II)). Concerning the performance of the scrubbing solutions, 30–40% of elemental mercury (Hg(0)) oxidation was achieved for the lignite coal, with the solution being preferably composed of FeCl 3 and H 2 O 2 and with pH value between 1 and 3. Results also showed that better Hg removal results were achieved by combining sulphur removal and Hg removal in the same stage of the CHX. An additional test done on the pilot-scale research boiler with a conventional wet scrubber showed that the Hg removal capability using the Fenton reactions was not dependent on the configuration of the wet scrubber. Although the Hg(0) oxidation ratio was not particularly high compared to the achievements from bench-scale tests, considering the economic and non-toxic nature of the scrubbing solution and the readily available equipment, the current results are encouraging and deserve further work to develop a better understanding of the chemistry in order to determine if the method can be further optimized.

Biomass fuel is the largest renewable energy resource and the fourth largest primary energy supply in the world. Because of its complex characteristics when compared to fossil fuel, potential problems, such as combustion system stability, the corrosion of heat transfer tubes, the qualities of the ash, and the emission of pollutants, are major concerns when co-firing the biomass fuel with fossil fuel in a traditional boiler. In this study, co-firing of coal with a biomass blend, including fuel derived from densified refuse, sludge, and waste tires, were conducted in a 130 ton/h steam circulating fluidized bed co-generation boiler to investigate the feasibility of utilizing biomass as a complemental fuel in a traditional commercial coal-fired boiler. The properties of the fly ash, bottom ash, and the emission of pollutants for various fuel ratios are analyzed and discussed in this study.

Co-combustion of waste with coal was carried out using a fluidised bed combustor with the aim of achieving a fuel mixture with little variations in its heating value and simultaneously reducing the accumulation of non-toxic waste material by upgrading them for energy purposes. Results obtained indicate that the feeding of waste materials plays an important role to achieve conditions for a stable combustion. The form in which the fuel is fed to the combustor makes a significant contribution to achieve desirable combustion performance and differences were observed in results regarding the combustion efficiency and emissions when waste was fed densified or in a fluffy state when it was burned mixed with coal. Part of the combustion of waste material, contrary to that of coal, was observed to take place in the freeboard where the temperature was as much as 150 °C above that of the bed.