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Pretreatment plays an important role in enhanced methane production from lignocellulose material. In this study, four different types of heating processes such as hot air oven, autoclave, liquid hot water bath, and microwave oven were used for comparison. The study was carried out in a biochemical methane potential assay to evaluate the different thermal heating process for enhanced methane production. Methane yield was increased in varied proportions with reduced digestion time for different heating processes of thermal pretreatment with low heating temperature at high residence time. Hot air oven pretreatment (17.92%) showed a high yield of methane production followed by autoclave (13.44%), microwave oven (9.54%), and hot water bath (7.54%) than control samples. In addition, the effect of pretreatment on biodegradability was assessed with three different kinetic models. Modified Gompertz model presents similar experimental data with a high degree of best fit when compared with the other two models.

Anaerobic fungi produce extracellular hydrolytic enzymes that facilitate degradation of cellulose and hemicellulose in ruminants. The purpose of this work was to study the impact of three different anaerobic fungal species (Anaeromyces mucronatus YE505, Neocallimastix frontalis 27, and Piromyces rhizinflatus YM600) on hydrolysis of two different lignocellulosic substrates, corn (Zea mays L.) silage and reed (Phragmites australis (Cav.) Trin. ex Steud.). Biomass from each plant species was incubated anaerobically for 11 days either in the presence of live fungal inoculum or with heat-inactivated (control) inoculum. Headspace gas composition, dry matter loss, soluble chemical oxygen demand, concentration of volatile fatty acids, and chemical composition were measured before and after hydrolysis. While some microbial activity was observed, inoculation with anaerobic fungi did not result in any significant difference in the degradation of either type of plant biomass tested, likely due to low fungal activity or survival under the experimental conditions tested. While the premise of utilizing the unique biological activities of anaerobic fungi for biotechnology applications remains promising, further research on optimizing culturing and process conditions is necessary.

Anaerobic digestion of corn silage was studied in a semi-continuous anaerobic plug flow reactor (PFR) at mesophilic condition. This work study the influence of increase in organic loading rate (OLR) on biogas production and other important parameters during anaerobic digestion. Varied OLR in the range of 3.5–8.5 kg m−3 d−1 (volatile solids (VS) fed basis)-volatile fatty acids (VFA) and FOS/TAC value increased with OLR, was stable up to 6.5 kg m−3 d−1, and became critically unstable when OLR was 8.5 kg m−3 d−1. An increase in biogas production was perceived with each upsurge in OLR, although CH4 concentration decreased and H2S content increased under high loading. The PFR lost its stability at 8.5 kg m−3 d−1 OLR that was apparently observed by decline in biogas yield and CH4 content.

Recovery of value-added materials from wastewater creates an opportunity for recycling resources to the circular bioeconomy and reduces the burden of the burgeoning demand and depletion of the natural resources. Much progress is focused and found successful in resource recovery options from wastewater in the laboratory scale over the last decade. This chapter aims to highlight and identify the emerging technologies that facilitate the recovery of value-added materials from wastewater systems focusing on subjective opinions and several key challenges. Value-added products such as biofuels, biopolymers, biopesticides, bioflocculants, biosurfactants, proteins and enzymes, and nutrient recovery from wastewater by various biotechnological advanced methodologies and other mechanical/chemical methods have been the primary focus and objective. Foreseeing the future generation of wastewater treatment plants with these resource recovery units along with the traditional treatment plant design would pave a way for the sustainable and circular bioeconomy concept. This helps to identify the potential application of treatment methodologies for the value-added products with further technological advancements. It is also important to understand and identify these knowledge gaps in converting the final end product to a profitable market, with a more sustainable and energy efficient way.

This work studied the effect of total solids content on methane production potential from pulp and paper mill sludge and its kinetic modeling. The modified Gompertz, logistic function, and ...

This study assessed the effect of different swine manure (SM)/corn stover (CS) mixtures based on total solids (TS) content with respect to hygienization, microbial community dynamics and methane yields on batch anaerobic co-digestion performance. Different ratios of SM and CS with TS content between 0.69 and 6% digested at 75 d revealed SM had the greatest methane yield at 403.9 mL g−1 volatile solids added (VS) and 86.31% VS reduction. BIOLOG AN microplates and lignocellulolytic enzyme assays proved to be rapid tools for characterizing microbial community metabolism as noted by the different carbon source utilization patterns between TS loadings. Hygienization of fecal indicator bacteria groups was achieved with some (E. coli) but not all groups (Clostridia spp.). The results showed that colorimetric biochemical assays and culture-based techniques can rapidly assess microbial community dynamics during co-digestion, and that TS- in the form of lignocellulosic biomass- influences microbial metabolic activities.

Different heating processes were applied to pretreat the pulp and paper mill sludge to enhance the hydrolysis stage. Hot air oven, autoclave, microwave and water bath were used for comparison. Chemical analyses exposed that all the pretreatment methods have shown improvement in solubilisation of organic matter. Among the pretreatments studied, heat transfer through hot air (80 °C for 90 min) mode had the highest impact on sludge solubilisation. There was an increase in cellulose (P = 0.0096), acid soluble (P = 0.0053) and insoluble lignin (P = 0.0012), but decrease in hemicellulose (P = 0.0009) content after pretreatment. The XRD and FT-IR spectroscopic characterisation shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the pretreated samples at higher severities. FESEM picture also confirms the change in structure after pretreatment. Thus, pretreatments contribute to disruption of the lignocellulosic structure making the cellulose easily accessible to acidogenic microorganisms.

The methane production rate increases with a decrease in moisture content up to the optimum threshold level and diminish in a batch reactor fed with the lignocellulosic material in solid state anaerobic digestion. The interpretation on two-faceted effect of moisture content could not be elucidated by the conventional anaerobic digestion model no 1. This study proposed that the decreased moisture content causes augmented mass diffusion resistance by the accumulation of hydrolytic product. This could lead to the reduced production of methane gas. Based on the hypothesis, a new solid state anaerobic digestion model was developed based on mass diffusion limitation and hydrolysis inhibition. The better degree of agreement between model simulation and the literature as well as experimental data verified that the deterioration in the volumetric rate of methane production. This could be attributed to hydrolysis inhibition as a result of limited mass diffusion in solid state anaerobic digestion.

This novel work is focused on evaluating the electrohydrolysis pretreatment conditions (applied voltage and time) and anaerobic digestion process for the biological bioconversion of pulp and paper mill sludge into biogas in batch assay. The pretreatment at 15 V for 45 min shows highest impact on sludge solubilization. The XRD and FT-IR spectroscopic characterization shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the pretreated samples. FESEM picture also qualities the change in alteration of structure after pretreatment. Batch anaerobic bioreactor was carried out to determine the efficacy of electrohydrolysis pretreated and untreated pulp and paper mill sludge. The methane production potential was increased from 274 ± 5 to 301 ± 4 mL CH4/g VS after electrohydrolysis pretreatment.

The application of anaerobic digestion is mounting worldwide because of its economic and environmental benefits. As a concern, the rate and extent of the anaerobic digestion of pulp and paper mill sludge was tested using the biochemical methane potential (BMP) with different food/microorganisms (F/M) ratio. The study was evaluated at five different F/M ratios (i.e. 0.5, 1.0, 1.5, 2.0, 2.5). In addition to that reaction kinetics and the influence of biodegradability were also evaluated for the biomethane potential of substrates. The highest cumulative methane yield was obtained in F/M ratio 2.0 with 3.4 L followed by F/M ratio 1.5 and 2.5 with 3.3 L and 2.9 L, respectively. The maximum methane production rate 3.66 L CH4 was perceived as per kinetics. The biomass activity may be affected due to the high substrate concentration during BMP test of lower F/M ratios. On the other hand, F/M ratio greater than 2.0, methane yield was decreased due to increased volatile fatty acid production reduces the reactor pH and inhibits methanogens activity.

Composting is a sustainable technology in treating organic pollutants and controlling odorous gas emissions from different organic solid waste, by reducing its size and volume. When the process parameters are handled efficiently, composting process is greatly effective than other waste treatment options in terms of operational costs, income generation out of compost, reduced air and water pollution. The successful composting operation does not count only the final product, but also the odorous gas emissions being released off to the atmosphere. Biofiltration is a relatively successful air treatment technology for polluted gases containing biodegradable compounds. By optimizing and focusing the operational parameters of biofiltration technology, 90% of treatment efficiency could be achieved with more economical advantage compared to other air treatment technologies. However, the complexity and the uncertainty measures in operating the system and understanding the process biodegradation mechanism is very crucial for the successful performance. Therefore, this review focusses and provides an assessment and treatment of different odorous gas emissions emitted during the composting processes. The recent advancements and treatment options for various volatile organic compounds (VOCs) and other odorous gas emissions during composting is updated. The advancements in bio-trickling filters, bioscrubber technology and membrane bioreactors treating VOCs has been focused. The use of different models in evaluating the process optimization and gas mitigation is also explained. Finally, the environmental impact of VOC compounds released into atmosphere from composting plants has been discussed.

Swine manure and corn stover are abundant agricultural wastes which contribute to greenhouse gas (GHG) emissions, nutrient runoff leading to eutrophication, and a biosafety risk with respect to improper swine manure handling. Anaerobic co-digestion (AcoD) of swine manure and corn stover can mitigate these negative impacts while producing biogas as a renewable energy source. Semi-continuous mesophilic plug flow reactor (PFR operation) was studied during a step-wise increase in organic loading rate (OLR) over the range of 0.25–4.7 kg volatile solids added (VS) m−3 d−1, which corresponded to total solids content (TS) of 1.5–9.0%. Process stability was observed at all OLR, with the highest total biogas yield and methane content of 0.674 ± 0.06 m−3 kg−1 and 62%, respectively, at 0.25 kg m−3 d−1. As OLR and TS increased, VS reduction decreased and volatile fatty acids (VFA) increased due to shorter hydraulic retention times (HRT). Hygienization potential was assayed using fecal indicator bacteria (FIB), with some groups being reduced (E. coli, fecal coliforms) and others not (Clostridia spp., fecal enterococci). Lignocellulolytic enzyme activity trended upward as OLR was increased, highlighting changes in microbial activity in response to feeding rate.

Kinetic study of plug flow reactor digesting corn silage was studied under the mesophilic condition (37 ± 2 °C). The effect of organic loading rate (OLR) on biogas yield and its production was tested in a long-term experimental study. Both the biogas yield (0.68–0.39 m3/kg) and methane content in the biogas (66–58%) were reduced with the increase in OLR (3.5–8.5 kg VS /m3٠d). In this study, the maximum biogas yield (ym) as 0.716 m3/kg and first-order reaction rate constant (k) values as 0.0689 per day was obtained. The developed kinetic model could be used to design the dimension for a plug flow reactor digesting different organic wastes such as agricultural residue, animal manures, and biogas crops.

A novel electrohydrolysis pretreatment enhances methane production from lignocellulose material during anaerobic digestion. A biochemical methane potential assay was carried out to determine the effect of direct current and the efficacy of electrohydrolysis pretreatment on biogas production. Methane yield was increased by 13.8%, to 301 ± 3 mL CH4/g VS, when lignocellulosic waste was pretreated with electrohydrolysis. A net energy gain of 13,224 kJ was realized after electrohydrolysis pretreatment, which was 1.51 times higher than reported for thermal pretreatment. In addition, two kinetic models were used, including the modified Gompertz model to reproduce the experimental data. These finding support the potential for increased methane recovery from lignocellulosic waste using electrohydrolysis as a pretreatment.

Pulp and paper industry is one of the most polluting, energy and water intensive industries in the world. Produced pulp and paper mill sludge (PPMS) faces a major problem for handling and its management. An anaerobic digestion has become an alternative source. This review provides a detailed summary of anaerobic digestion of PPMS - An overview of the developments and improvement opportunities. This paper explores the different pretreatment methods to enhance biogas production from the PPMS. First, the paper gives an overview of PPMS production, and then it reviews PPMS as a substrate for anaerobic digestion with or without pretreatment. Finally, it discuss the optimal condition and concentration of organic and inorganic compounds required for the anaerobic metabolic activity. Future research should focus on the combination of different pretreatment technologies, relationship between sludge composition, reactor design and its operation, and microbial community dynamics.

The objective of the study was to assess the effect of substrate concentration by specific methanogenic activity (SMA) of thermally pretreated pulp and paper mill sludge. Different substrate concentration through food to microorganism ratio varied from 1.0 to 3.0 was carried out in a mesophilic condition as biochemical methane potential assay. Experimental results offered that cellulose removal rate spikes up to 60.2%. The specific methane gas production and biodegradability were increased up to 303 mL of CH4/g VS and 73% respectively. By increasing the substrate concentration, SMA was significantly improved in a linear manner. The net energy of 8735 kJ was gained after thermal pretreatment. In addition to that three kinetics model were used, among that the modified Gompertz and logistic function models represent and reproduce the experimental data, while the earlier has the better fit.