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Paper wastes form the major biodegradable fraction of the municipal solid waste. One of the best ways to treat paper wastes is using them as a feedstock for biomethane production through anaerobic digestion (AD). However, the AD characteristics, kinetics, and energy potential of different types of paper wastes are not clear. In this study, four kinds of typical paper wastes including corrugated board (CB), office paper (OP), tissue paper (TP), and magazine paper (MP) were used as feedstocks to produce biomethane at different volatile solids (VS) organic loading (OL). TP had a high cellulose content and showed high biomethane potential, while the lowest was obtained by CB, possibly due to its high lignin content. Kinetic analysis showed that Cone and modified Gompertz model could fit the biomethane production process well. Energy potential analysis revealed that biomethane yield, electric generating efficiency, and electricity price were the principal factors accounting for the profitability of biomethane production project treating paper wastes. Overall, paper wastes could be a promising feedstock for biomethane production, because paper wastes not only had high biomethane yield and biodegradability that exceeded many kinds of organic wastes but also could be continuously supplied for AD plants without the influence of seasonal changes.

Demand Side Management (DSM) performs a significant function in the electrically powered energy system in order to manage power demand-side resources. Although China has brought DSM for the first time in the early 1990s, its advantages have not been entirely utilized. In this study, we first present a quick history of the energy policy of China, its electricity enterprise, and reform. Based on the analysis of DSM practices in Asia- Pacific region, the DSM development and the reform of electrical energy pricing in seven countries namely, Pakistan, India, Malaysia, Singapore, Thailand, Bangladesh, and China have been discussed. The primary limitations to DSM include fallacious market-oriented DSM mechanisms, the underdeveloped power carrier industry, low motivation level of grid companies for DSM because of their conventional business model, and low motivation of electricity end-users. This paper represents a case study of China’s electricity sector reform which can probably alter power transmission and pricing of distribution scheme and enterprise model of grid companies, thereby enhancing competition. A number of rules & regulations and series of policies linked to DSM were formulated by Chinese country wide ministries. But still, there are many troubles in the implementation of DSM. The current status of DSM improvement in China is investigated from distinct factors of policies and guidelines associated with DSM, DSM improvement of representative regions and DSM organizational administration. This study has also discussed the challenges faced by the implementation of DSM and proposed feasible measures totally based on the challenges encountered in implementing of DSM. This study is beneficial in promoting the improvement of China’s DSM. Based on these findings, the possible effects of DSM reforms are; government must give more attention to DSM; grid companies might also have better incentives to invest in DSM; DSM end users of electricity motivations may also increase; demand response applications can be improved and commercial DSM business models can be proposed.

Anaerobic digestion (AD) is a promising technology for treating food waste, as it has high energy recovery and controls environmental problems. The biogasification performance of food waste was observed by changing the process parameters such as hydraulic retention time (HRT) and organic loading rate (OLR). A continuously stirred tank reactor (CSTR) was operated to investigate one-phase anaerobic digestion performance of food waste due to its easy operation and lower cost for industrial application. Two operating conditions R1 (fixed HRT and loading) and R2 (varying HRT and loading concentration) were set for 116 and 92 days respectively. Results showed that the best OLR for R1 was 2.25 g ⋅ L−1 ⋅ d−1 with the biogas yield of 787 mL ⋅ g−1 ⋅ d−1. However, the best OLR for R2 was also 2.25 g ⋅ L−1 ⋅ d−1 with the biogas yield of 724 mL ⋅ g−1 ⋅ d−1. Reactor 1 with fixed HRT showed better performance with higher biogas yield and better stability indicators. The results obtained in this study would be useful for industrial utilization of food waste in the future.

A large amount of sheep dung (SD) produced on farms in China is a potential feedstock for production of clean energy in the form of biogas. Similarly, waste paper can be a notable energy source that is worth exploiting. In this study, we assessed the feasibility of co-digesting nitrogen-rich SD with the carbon-rich corrugated board (CB) or waste office paper (OP) in varying volatile solids (VS) ratios, to produce methane. Synergistic effect of co-digesting SD with CB and SD with OP on methane production was found in this study. The highest methane yields of 151.62 and 198.85 mL/g-VS were obtained during the co-digestions of SD with CB at 4:1 ratio (SDCB) and SD with OP at 2:3 ratio (SDOP), respectively. High-throughput 16 S rRNA gene sequencing demonstrated that the microbial diversity and richness in SDCB and SDOP co-digests were higher than in SD and OP mono-digests, respectively. Characteristic bacteria and archaea in the digests were strongly substrate-related and might contribute to methane production. The validated results indicated that methane production through anaerobic co-digestion of SD and waste paper can be an efficient way that could not only reduce environmental pollution but also contribute to methane production.

This study employs a microaerobic pretreatment that includes different microbial reagents combined with oxygen to enhance the energy conversion potential of rice straw (RS) via anaerobic digestion (AD) in a more cost-effective and time-efficient manner. Five broad varieties of microbial reagents including liquid consortium (LC), cow manure (CM), sheep dung (SD), biogas slurry (BS), and straw-decomposing consortia (SC), have been used as sources of useful microbes at varying oxygen concentrations of 0, 6, 12 and 24 mLO2/gVS to explore the effect of microaerobic pretreatment on RS degradation. The results showed that RS pretreated with SC had the highest cumulative methane yield (CMY) of 311.7 mL/gVS at 12 mLO2/gVS, followed by BS, CM, LC, and SD, with the CMYs of 270.5, 263.2, 257.1, and 256.7 mL/gVS at 6 mLO2/gVS, respectively. The RS pretreated with SC, BS, CM, LC, and SD led to improvements in the methane yield by 88.7%, 63.7%, 59.3%, 55.6%, and 55.4%, respectively, compared to the untreated RS. The microbial community analysis revealed that the relative abundance (RA) of Firmicutes, which are known to play a key role in accelerating the rate of hydrolysis, increased after microbial pretreatment combined with oxygen supply. The RA of Clostridium III, which facilitates cell wall degradation via hydrolytic pathways along with other sugar-fermenting bacteria, such as Saccharofermentans, Lutaonella, and Sedimentibacter, increased after AD in the digestate of pretreated RS compared to that in untreated RS. Moreover, a shift in acetoclastic and hydrogenotrophic archaea, including Methanothrix and Methanospirillum, was also observed, indicating precursor changes resulted by pretreatments and varied microbial metabolism, which might have enhanced the methane production process of RS. The energy potential analysis revealed that microbial pretreatment was a suitable technique for stimulating the energy conversion efficiency of RS. This study can be used as a reference for future utilization of a diverse range of lignocellulosic materials for clean energy production.

Biochar simply is the material produced when biomass undergoes any chemical processes under the conditions of pyrolysis. The variety of biomasses, including wood waste, agricultural crop leftover, organic waste, animal manure, and forestry residues, have been considered as raw material to produce biochar. Biochar is widely used for generation of heat and power and an addition to soils, in which it serves as a fertilizer and carbon sequestration agent. Also in the form of being activated, it finds significant role for various adsorption applications. The most beneficial use of a given char depends on its physical and chemical characteristics, even though the relationship of char properties to these applications is not well defined. Various widely used modern analytical techniques, which are applicable and crucial for biochar characterization, have been reviewed in the present work, such as solid state nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-rays photoelectron spectroscopy, X-rays diffraction, thermogravimetric analysis, near edge X-rays absorption fine structure spectroscopy, and gas chromatography-mass spectroscopy. Utilization of these modern techniques provides the quantitative as well as qualitative information, i.e., determining the sizes, shapes, and physicochemical characteristics of biochar, which is reliable to track changes in the carbon arrangement over reaction time and temperature, and will be useful for efficient production of biochar and application. It provides the useful information for the researchers in this area and is beneficial not only for the effective biochar production, but also for potential utilization/application, and not only for environment but also for agriculture.

Agricultural residues, such as lignocellulosic materials (LM), are the most attractive renewable bioenergy sources and are abundantly found in nature. Anaerobic digestion has been extensively studied for the effective utilization of LM for biogas production. Experimental investigation of physiochemical changes that occur during pretreatment is needed for developing mechanistic and effective models that can be employed for the rational design of pretreatment processes. Various-cutting edge pretreatment technologies (physical, chemical and biological) are being tested on the pilot scale. These different pretreatment methods are widely described in this paper, among them, microaerobic pretreatment (MP) has gained attention as a potential pretreatment method for the degradation of LM, which just requires a limited amount of oxygen (or air) supplied directly during the pretreatment step. MP involves microbial communities under mild conditions (temperature and pressure), uses fewer enzymes and less energy for methane production, and is probably the most promising and environmentally friendly technique in the long run. Moreover, it is technically and economically feasible to use microorganisms instead of expensive chemicals, biological enzymes or mechanical equipment. The information provided in this paper, will endow readers with the background knowledge necessary for finding a promising solution to methane production.