• Energy Research

Abstract Standardization of biogas technology is immensely important for the promotion of the biogas industry worldwide. China has built a complete biogas standard system, which is divided into common, household biogas, biogas engineering, biogas digester for domestic sewage treatment, output utilization, and service system standards. The problems and potential barriers for biogas standardization in China are analyzed and come down to sluggish standard, overlapped standard, government-dominated standard, and lagging international standard. Accordingly, all potential biogas standards should be evaluated and placed under the same department. China Biogas Society and China Association of Rural Energy Industry play leading roles in developing enterprise or group/association biogas standards and ISO biogas standards. The bio-natural gas standard system and experimental standardization should be developed as well to replenish biogas standard system. A paradigm shift in biogas standardization should be from government-dominated to market-oriented model. The lessons learned for other developing countries includes expanding standardization to multi-aspects to realize full lifecycle control and management, building rapid responding mechanism of standardization to adopt industry transformation, integrating outdated standards into new versions, and establishing market-based standard system.

Anaerobic digestion is one of the most sustainable and promising technologies for the management of organic residues. China plays an important role in the world’s biogas industry and has accumulated rich and valuable experience, both positive and negative. The country has established relatively complete laws, policies and a subsidy system; its world-renowned standard system guarantees the implementation of biogas projects. Its prefabricated biogas industry has been developed, and several biogas-linked agricultural models have been disseminated. Nonetheless, the subsidy system in China’s biogas industry is inflexible and cannot lead to marketization, unlike that of its European counterpart. Moreover, the equipment and technology levels of China’s biogas industry are still lagging and underdeveloped. Mono-digestion, rather than co-digestion, dominates the biogas industry. In addition, biogas upgrading technology is immature, and digestate lacks planning and management. China’s government subsidy is reconsidered in this work, resulting in the recommendation that subsidy should be based on products (i.e., output-oriented) instead of only input subsidy for construction. The policy could focus on the revival of abandoned biogas plants as well.

AbstractBiomass energy (bio-energy) is a clean energy, which is helpful to environmental construction and CO2 emission reduction. China is the largest energy consumer in the world, building Biomass Power Plant (BPP) is beneficial to make use of agricultural biomass as well as to reduce environmental pollution. However, many factors influence the exploitation of a proposed BPP project. The objective of this paper is to develop a methodology that is able to analyze the agricultural biomass potential for BPP in China. This methodology analyses the related factors then conducts the sensitivity analyses of the main factors. Related factors mainly include local condition, demand of multiduty agricultural residues, logistics while sensitivity of main factors mainly aims to competition of nearby BPP, competition of other utilizations, price of biomass, preferential policy, etc. Based on a field study, an applied illustration of this methodology on evaluating agricultural biomass potential for a proposed BPP project is presented. The case study shows that it is not suitable to build a new BPP. In view that renewable energy projects will be promoted strongly, it is predicted that the methodology would be a potential tool, which can be applied well for BPP in China.

Abstract China plays a leading role in the worldwide development and dissemination of household-based biogas technology. Since the 1980s, China has developed many types of commercialized or half-commercialized prefabricated biogas digesters (PBDs), which are categorized into three: glass fiber-reinforced plastic digesters, plastic soft digesters, and plastic hard digesters. This paper summarizes the development of PBDs in China, including their key characteristics, manufacturing process, advantages and disadvantages, cost analysis, marketing, and future prospects. Furthermore, the paper highlights and analyzes potential constraints in the promotion of these types of digesters; examples of these constraints include incomplete standardization systems, insufficient demonstration projects, low-quality digesters, and missing authorizations from the inspection department. A preferential policy should be formulated for the prefabricated digester industry. Specifically, the standardization system should be improved, technological innovations should be encouraged, self-regulation of the industry should be intensified, demonstration projects should be implemented, and follow-up services should be improved. PBD technologies can potentially be applied with great reliability and high efficiency not only in China but also in other countries.

With the increasing demand for renewable energy and environmental protection, biogas technology has attracted considerable attention around the world. Fecal sludge (FS) is rich in organic matter, and it contains high concentrations of excreted pathogens that cause gastro-intestinal infection. In Tanzania, fecal sludge management from on-site sanitation systems poses a threat on environmental safety. This study aimed to assess the feasibility of the use of anaerobic digestion (AD) for the treatment of FS and the production of biogas as renewable energy to achieve multiple benefits in Tanzania. For the experiments, FS and food waste (FW) were used as feedstock, and rice straw-derived biochar (RSB) was added as an additive to improve biogas production. The mesophilic anaerobic digestion resulted in a methane yield of 287.5 ml/g VS for FS + FW co-digestion and 396 ml/g VS for FS + FW + RSB co-digestion. At ambient temperature (20–26°C), the system produced a methane yield of 234 ml/g VS for FS + FW co-digestion and 275 ml/g VS for FS + FW + RSB co-digestion. Three different scenarios (digester with volumes of 4, 100, and 400 m3, respectively) and strategies for FS treatment by AD in Tanzania were proposed and analyzed. These treatments can produce methane volumes of 1.95, 49.5, and 199.5 m3 with pay-back periods of 3, 5, and 15 years and net present values of + 28, +1,337, and +52,351 USD, respectively. The calculations also showed that the heat value from the produced biogas and energy needed to heat the digester at 26–37°C resulted in energy balance values of + 0.012, + 0.53, and + 2.22 GJ/day for the 4, 100, and 400 m3 digester volumes, respectively.

The sustainability of microbial lipids production from traditional carbon sources, such as glucose or glycerol, is problematic given the high price of raw materials. Considerable efforts have been directed to minimize the cost and find new alternative carbon sources. Volatile fatty acids (VFAs) are especially attractive raw materials, because they can be produced from a variety of organic wastes fermentation. Therefore, the use of volatile fatty acids as carbon sources seems to be a feasible strategy for cost-effective microbial lipid production.Lipid accumulation in Y. lipolytica using synthetic and food waste-derived VFAs as substrates was systematically compared and evaluated in batch cultures. The highest lipid content obtained with acetic, butyric, and propionic acids reached 31.62 ± 0.91, 28.36 ± 0.74, and 28.91 ± 0.66%, respectively. High concentrations of VFA inhibited cell growth in the following order: butyric acid > propionic acid > acetic acid. Within a 30-day experimental period, Y. lipolytica could adapt up to 20 g/L acetic acid, whereas the corresponding concentration of propionic acid and butyric acid were 10 and 5 g/L, respectively. Cultures on a VFA mixture showed that the utilization of different types of VFA by Y. lipolytica was not synchronized but rather performed in a step-wise manner. Although yeast fermentation is an exothermic process, and the addition of VFA will directly affect the pH of the system by increasing environmental acidity, cultures at a cultivation temperature of 38 °C and uncontrolled pH demonstrated that Y. lipolytica had high tolerance in the high temperature and acidic environment when a low concentration (2.5 g/L) of either synthetic or food waste-derived VFA was used. However, batch cultures fed with food fermentate yielded lower lipid content (18.23 ± 1.12%) and lipid productivity (0.12 ± 0.02 g/L/day). The lipid composition obtained with synthetic and food waste-derived VFA was similar to commercial biodiesel feedstock.This work demonstrated the feasibility of utilizing synthetic and food waste-derived VFA for lipid production by Y. lipolytica. The good adaptability of Y. lipolytica to the high temperature and acidic environment further illustrated its considerable potential for practical application.

More than 500 million people will be added to Africa’s cities by 2040, marking the largest urbanization in history. However, nonrenewable fossil energy sources are inadequate to meet Africa’s energy needs, and their overexploitation leads to intensified global warming. Fortunately, Africa has a huge potential for biomass energy, which will be an important option for combating climate change and energy shortage. In this study, we present a typical large-scale biogas plant in Burkina Faso, West Africa (Ouagadougou Biogas Plant, OUA), which is the first large-scale biogas generation plant in West Africa. The primary objective of OUA is to treat human feces, and it serves as a demonstration plant for generating electricity for feed-in tariffs. The objectives of this study are to assess the greenhouse gas reduction capacity and economic, environmental, and social benefits of OUA and to analyze the opportunities and challenges of developing biogas projects in Africa. As a result, the net economic profit of the OUA biogas plant is approximately USD 305,000 per year, with an anticipated static payback period of 14.5 years. The OUA plant has the capacity to treat 140,000 tons of human feces and 3000 tons of seasonal mixed organic waste annually, effectively reducing greenhouse gas emissions by 5232.61 tCO2eq, improving the habitat, and providing over 30 local jobs. Finally, the development of biogas projects in Africa includes advantages such as suitable natural conditions, the need for social development, and domestic and international support, as well as challenges in terms of national policies, insufficient funding, technical maintenance, and social culture.

Cement is the most widely used construction material in the world. However, its manufacture is high energy consumption and high carbon emission owing to the high temperature calcination process. Geopolymer is an ideal alternative material for cement because it has a similar structure and performance to cement. In addition, it can be synthesized at room temperature and thus has the advantages of energy saving and carbon emission reduction. Sewage sludge (SS) can be used as raw material for geopolymer synthesis. However, the high organic matter content in SS lowers the mechanical strength of geopolymer. Although the organic matter in SS can be removed by incineration at high temperature, this consumes energy and emits carbon dioxide, which diminishes the advantages of geopolymer. In this study, the Fenton method was applied for the removal of organic matter in SS at room temperature. The parameters of the Fenton method, including the dosages of hydrogen peroxide (H2O2) and Fe2+ reagent (FeSO4·7H2O), reaction time, and initial pH value, were investigated. The results indicated that 83.7% of the organic matter in SS could be removed at room temperature by using 5.15 M H2O2 and 5.15 mM FeSO4·7H2O at pH 7, which suggested the possibility of sewage sludge reclamation through geopolymer synthesis as an alternative material for cement toward sustainability.