Globally, there is increasing awareness that renewable energy and energy efficiency are vital for both creating new economic opportunities and controlling the environmental pollution. AD technology is the biochemical process of biogas production which can change the complex organic materials into a clean and renewable source of energy. AcoD process is a reliable alternative option to resolve the disadvantages of single substrate digestion system related to substrate characteristics and system optimization. This paper reviewed the research progress and challenges of AcoD technology, and the contribution of different techniques in biogas production engineering. As the applicability and demand of the AcoD technology increases, the complexity of the system becomes increased, and the characterization of organic materials becomes volatile which requires advanced methods for investigation. Numerous publications have been noted that ADM1 model and its modified version becomes the most powerful tool to optimize the AcoD process of biogas production, and indicating that the disintegration and hydrolysis steps are the limiting factors of co-digestion process. Biochemical methane potential (BMP) test is promising method to determine the biodegradability and decomposition rate of organic materials. The addition of different environmentally friendly nanoparticles can improve the stability and performance of the AcoD system. The process optimization and improvement of biogas production still seek further investigations. Furthermore, using advanced simulation approaches and characterization methods of organic wastes can accelerate the transformation to industrializations, and realize the significant improvement of biogas production as a renewable source and economically feasible energy in developing countries, like China. Finally, the review reveals, designing and developing a framework, including various aspects to improve the biogas production is essential.

Anaerobic co-digestion process for biogas production: Progress, challenges and perspectives

Anaerobic digestion is a worldwide technology for the treatment of organic waste streams with clear environmental benefits including generation of methane as renewable energy. However, the need to improve process feasibility of existing applications as well as to expand anaerobic digestion to a range of new substrates has raised interest on several intensifications techniques. Among them, the supplementation of inorganic and biological additives has shown good results at improving digesters performance. This manuscript presents a comprehensive review about recent advances in the utilization of inorganic and biological additives. On the one hand, reviewed inorganic additives comprise: (i) macro- (e.g. P, N and S) and micro- (e.g. Fe, Ni, Mo, Co, W and Se) nutrients supplements, (ii) ashes from waste incineration, (iii) compounds able to mitigate ammonia inhibition, and (iv) substances with high biomass immobilization capacity. Among them, iron (Fe 0 and Fe(III)) has shown particularly promising results, which have been mainly related to their action as electron donor/acceptor and cofactor of key enzymatic activities. On the other hand, reviewed biological additives include: (i) the dosage of microbial inocula with high hydrolytic or methanogenic activity (bioaugmentation), and (ii) the addition of enzymes able to facilitate particulate organic matter solubilization.

The role of additives on anaerobic digestion: a review

The replacement of fossil fuels by biofuels has been extremely important worldwide to stimulate the growth of economies based on the sustainability through the use of renewable resources. Anaerobic digestion for biogas production is recognized as a clean technology that allies the suitability of wastes with energy generation, fulfilling the requirements for a sustainable alternative to provide the optimization of the biofuels production. This alternative is especially interesting for the sugarcane ethanol production in Brazil, in which the generation of vinasse, the main liquid waste, is very expressive. Nevertheless, the use of vinasse for anaerobic digestion has been finding some challenges to its establishment in the Brazilian sugarcane biorefineries. This paper reviews the actual context of anaerobic digestion within the sugarcane ethanol production in Brazil, presenting the main obstacles for its full application and the directions to promote it as well. Alternatives for biogas use are also presented and compared, highlighting the environmental and energy advantages of applying anaerobic digestion in the sugarcane biorefineries. This scenario is envisaged as a suitable way to achieve the future biorefineries model, based on the use and recovery of renewable resources with economic, social, and environmental benefits.

Anaerobic digestion of vinasse from sugarcane ethanol production in Brazil: Challenges and perspectives

Resource recovery and circular economy from organic solid waste using aerobic and anaerobic digestion technologies.

Global annual production of lignocellulosic biomass including undervalued agricultural residues and greenhouse biomass is about 181.5 billion tonnes. This undervalued biomass has a high potential to produce biogas in anaerobic digestion (AD). Among the various pre-treatment methods, hydrothermal (HT) pre-treatment of lignocellulosic biomass is a promising approach to increase biogas production in AD. However, the high carbon to nitrogen ratio (C/N) of lignocellulosic biomass is reported to be the major limiting factor for a higher biogas yield. Hence, the synergistic integration of low C/N ratio biomass with high C/N ratio lignocellulosic biomass in an AD system appears to be a logical option to enhance biogas yield. High moisture lignocellulosic biomass HT pretreatment and biogas production in AD have the potential for renewable energy production with limited use of process energy. However, hydrothermal process temperature, AD substrate C/N ratio and its inhibitory elements are important parameters for optimum biogas production. Greenhouse biomass pretreatment in hydrothermal process can produce biochar, biogas and biofertilizer, which can be used as input heat and nutrient source for greenhouses. Finally, the operation of greenhouse in this system can manage zero waste and reduce greenhouse gas (GHG) emissions and climate change.

Challenges and opportunities of lignocellulosic biomass for anaerobic digestion

The need to develop and improve sustainable energy resources is eminent due to the finite nature of our fossil fuels. Recent modification of laws, development of technologies and business movement has encouraged the transition to a recycling-based society. Today economy and technologies largely depend upon energy resources that are renewable as well as eco-friendly. Biogas is an environment friendly, economic and an alternative means to fossil fuel. The use of biogas is widespread in countries such as India and China. The Indian government׳s energy policy tries to support renewable energy by providing incentives to central and state government level. Attempts have been made to manipulate the biogas process towards industrial scale by pre and post manipulation. Pre manipulation includes maintenance of temperature, moisture, pH and microorganisms. Whereas post manipulation involves scrubbing in which water vapor, CO 2 and H 2 S has been removed through activated charcoal and water shower. Bacteria and enzymes play crucial role in anaerobic digestion and they are essential for efficient process. Trials have been made by use of bio-enzymatic preparations to enhance the biogas production. This paper reviews the details about decomposition, process of anaerobic decomposition, diverse constraints behind anaerobic technology and different aspects for enhancement of biogas production through enzymes and microorganisms.

A review on anaerobic decomposition and enhancement of biogas production through enzymes and microorganisms

A key strategy allied with today is to develop an alternative energy source instead of fossil fuels in order to compensate present energy need in addition to reduce environmental concerns owed by pollution and global warming. Energy generation in feasible manner without possessing environmental crash is a difficult task where alternative concepts were requisite to ensure sustainable development with accessible technologies. Further advances triggered renewed attention in biogas production technology while it has great impacts on diminishing major economic issues raised in the world. Since the light of these strategies, the present review intended to critically evaluate the recent technological advances and promising prospects coupled with various aspects of biogas production such as sustainable feedstock utilization, microbial and enzyme dynamics, parameter optimization and process segregation, for enhancing this technology in outlook. Appropriate selection, co-digestion, and biotransformation offers a great challenge that crafts substrate to become more energy efficient, besides to trim down the constraints behind principle biomass utilization. A basic framework for process stimulation with microorganisms and enzyme preparations explored that further experimental trials by means of identification of efficient microbes and standardization of enzyme dynamics would augment the feasibility of energy flow during anaerobic digestion. Accordingly, the optimization of various parameters is preferred to accelerate biogas production by resolving the problems occur during anaerobic digestion. Despite the development of multi-stage digester designs intend a breakthrough for process segregation and existing opportunities in this aspect needed further research interest to attain better performance of the system. Moreover, advance simulation approaches using projected prospects from this review would realize significant enhancement of biogas production in the predictable manner.

A review on current aspects and diverse prospects for enhancing biogas production in sustainable means.

Microorganisms play a vital role in processing organic matter and returning the chemical elements into active cycle. In these decomposers are effective in dismantling the complex organic matter through a sequential break down and release of energy. Biogas is one such process which occurs in the absence of oxygen and several groups of microorganism involve in degrade the organic compounds and release methane gas. To attain biogas with high methane concentration it is important to create and maintain the suitable bacterial consortia within the digester. Therefore, the present research was carried out to isolate different bacterial species from cow dung and construct four different bacterial consortia to analyze their efficiency of biogas production. The biogas production was carried out in a pilot scale batch reactor for 30 days using poultry droppings as a substrate and four different bacterial consortia in four separate digesters. Various hydrolytic enzymes, volatile fatty acids and biogas production were measured in the interval of 10 days. From the above study it was concluded that consortia 4 containing high amount methanogenic bacteria gave the highest biogas production with methane 79.45%.

/pdf/identification-and-evaluation-of-effective-bacterial-37uz0lt5n0.pdf

Identification and Evaluation of Effective Bacterial Consortia for Efficient Biogas Production

The anaerobic digestion of cow dung was investigated for 30days in a laboratory scale batch reactor. Totally nine bacterial strains were isolated from cow dung slurry. The bacterial isolates were preliminarily examined by morphological characteristics and they were further confirmed by 16S rRNA sequencing and analyzed through BLAST. Microbial dynamics showed that hydrolytic bacterial population was initially increased and decreased towards the end of anaerobic digestion. But in methanogenic population, they were initially very low and increased gradually towards the end of anaerobic digestion. In Ruminococcus species the population was observed in fluctuation. The total solid (TS), volatile solid (VS) and chemical oxygen demand (COD) removals amounted to 46.12%, 43.14% and 45.23% respectively. Anaerobic digestion was feasible with pH about 7.17, temperature at 37.180C and maximum methane yield was about 64% at 30th day of digestion

/pdf/microbial-dynamics-during-anaerobic-digestion-of-cow-dung-2cu4823mg7.pdf

Microbial dynamics during anaerobic digestion of cow dung

During this century, sustainable development programs focusing on global environmental concerns such as conservation of energy, preservation of water and management of environment through appropriate alternatives and technologies. In this context, biogas production technology has been developed and proven successful presently. In recent past, research on this technology has limited on some instances like optimization of different substrate and parameters like temperature, pH, total solid concentration, retention time, etc. A critical analysis reveals that few issues associated with the system used for biogas production at present, while various prospects lifted during the review gives an opportunity to enhance biogas production using advance techniques in future. Pretreatment of lignocellulosic substrate, incorporation of biological, chemical or inorganic additives and enzymes to the substrate were found as effective for increasing biogas production. Another interesting trend in this field is the development of potential microorganism for enhancing biogas production through gene manipulation. Multi-stage processes with separation of hydrolysis, acidogenesis, acetogenesis and methanogenesis would provide biological stability for each step which absolutely enforces the reaction at temporal dimension.

http://www.isca.in/IJENS/Archive/v3/i1/12.ISCA-IRJEvS-2013-253.pdf

P. Merlin Christy

Papers

A review on anaerobic decomposition and enhancement of biogas production through enzymes and microorganisms

A review on current aspects and diverse prospects for enhancing biogas production in sustainable means.

Identification and Evaluation of Effective Bacterial Consortia for Efficient Biogas Production

Microbial dynamics during anaerobic digestion of cow dung

A Review on Trends issues and Prospects for Biogas Production in Developing Countries