Improvement Of Anaerobic Digestion Research Articles

Improvement of Anaerobic Digestion by Addition of Halloysite and Magnetite Powders

Objectives : This study aimed to explore the potential of halloysite and magnetite powders to enhance anaerobic digestion efficiency and to compare their effects.Methods : Anaerobic digestion experiments were conducted in a total of four consecutive batch processes using reactors with halloysite and magnetite powders added at concentrations of 1 g/L, 10 g/L, and 50 g/L, as well as a control reactor without any powder addition. Cumulative methane production was measured in each batch, and the Gompertz model was applied to calculate kinetic parameters, which were then compared with the control. Additionally, microbial community analysis was performed using 16S rRNA amplicon sequencing, and correlations between the powder concentrations, Gompertz kinetic parameters, and microbial groups were evaluated.Results and Discussion : Both powders demonstrated an effect on improving methane production rates. When halloysite was added at a concentration of 50 g/L, an increase in methane production rate was observed in all batches. Compared to the control, the lag phase (λ) was reduced by up to 31.4%, and the maximum methane production rate (R<sub>m</sub>) increased by 17.6%. While the effects of halloysite at concentrations of 1 g/L and 10 g/L were less significant compared to 50 g/L, trends of reduced lag phase and increased Rm were noted in at least two batches. For magnetite powder, the most effective concentration in the first and second batches was 1 g/L, but in the third and fourth batches, lag phase (λ) was reduced by up to 39.3%, and the maximum methane production rate (R<sub>m</sub>) increased by 13.2% at concentrations of 10 g/L and 50 g/L. Microbial community analysis revealed an increased dominance of <i>Geobacter</i> and <i>Methanosarcina<>/i associated with the DIET mechanism as the amount of magnetite increased.Conclusion : This study confirms the potential of halloysite and magnetite powders to enhance methane production rates in anaerobic digestion processes. These findings suggest the feasibility of using powdered additives to improve the efficiency of anaerobic digestion, providing foundational data for future related research.

Environmental applications of carbon-based materials: a review

Environmental pollution is a major issue, yet actual remediation techniques are limited. Carbon-based materials are increasingly used to treat air and water. Here we review the applications of carbon nanomaterials made of biochar, activated carbon, carbon nanotubes and graphene for the adsorption of toxic gases, the removal of pollutants from ecosystems, and the improvement of anaerobic digestion. Carbon materials have been found efficient in removing nitric oxide, hydrogen sulfide, heavy metals, dyes, pharmaceutical compounds and other pollutants from the environment, with adsorption efficiencies reaching 80% and degradation efficiencies up to 99%. Biochar addition induces a 60% improvement in biogas production. Similarly, in composting, up to 60% less ammonia emissions were observed when biochar was added. Biomass-based carbon materials appear economical, sustainable and eco-friendly.

Perspectives of surface plasmon resonance sensors for optimized biogas methanation.

Biogas production is becoming significantly viable as an energy source for replacing fossil‐based fuels. The further development of the biogas production process could lead to significant improvements in its potential. Wastewater treatment currently accounts for 3% of the electrical energy load in developed countries, while it could be developed to provide a source of nitrogen and phosphorus, in addition to energy. The improvement of anaerobic digestion (AD) detection technologies is the cornerstone to reach higher methane productivities and develop fully automatized processes to decrease operational costs. New sensors are requested to automatically obtain a better interpretation of the complex and dynamical internal reactor environment. This will require detailed systematic detection in order to realize a near‐optimal production process. In this review, optical fiber‐based sensors will be discussed to assess their potential for use in AD. There is currently a disparity between the complexity of AD, and online detection. By improving the durability, sensitivity, and cost of dissolved H2 (as well as H2S, acetic acid, ammonia, and methane) sensor technology, further understanding of the AD process may allow the prevention of process failure. The emergence of surface plasmon resonance (SPR) sensing with optical fibers coupled with the H2‐sensitive metal palladium, allows detection of dissolved hydrogen in liquid. By implementing these SPR sensors into AD, improvements to the biogas production process, even at small scales, may be achieved by guiding the process in the optimum direction, avoiding the collapse of the biological process. This review intends to assess the feasibility of online, cost‐effective, rapid, and efficient detection of dissolved H2, as well as briefly assessing H2S, acetic acid, ammonia, and methane in AD by SPR.

Contribution of solid and liquid fractions of sewage sludge pretreated by high pressure homogenization to biogas production

High pressure homogenization (HPH) pretreatment can effectively enhance anaerobic sludge digestion. In order to understand the corresponding mechanisms, different homogenization pressures were applied on sewage sludge, and solid and liquid fractions were separately digested to clarify contribution of solid and liquid fractions to biogas production. Results showed that the methane was mainly produced from solid fraction, and methane yield was increased with the increase of pretreatment pressure. The biogas and methane production from sludge (digested without solid–liquid separation) was 17% and 45% higher than the sum of that from solid and liquid fractions (digested separately) under a pressure of 40 MPa, respectively. This indicated that the sludge liquid fraction synergistically improved the biodegradation of sludge solids. The improvement of anaerobic digestion was attributed to organic release by sludge disintegration, sludge disruption and further increase of particle surface area. The methane production was linear with effectiveness of HPH pretreatment.

Potential of Crystalline and Amorphous Ferric Oxides for Biostimulation of Anaerobic Digestion

Iron oxides have been widely investigated to accelerate the conversion of organic wastes to methane. However, the potential mechanism involved with different types of iron oxides is a controversial topic. In this study, crystalline Fe2O3 and amorphous Fe (OH)3 were respectively supplemented to explore the effects of the crystal form of Fe(III) on anaerobic digestion. The results showed that the addition of Fe2O3 and Fe(OH)3 both significantly enhanced COD removal and biomethanation compared with the control. The reason was related to that the supplement of Fe(OH)3 induced an efficient microbial dissimilatory iron reduction to enhance the decomposition of complex organics into simples. Consistently, 28.3% of Fe(OH)3 dosed at the initial stage were reduced into Fe(II), while no obvious iron reduction was observed with the Fe2O3 supplement. Interestingly, Fe2O3 significantly stimulated the secretion of protein and humic acid-like substances in EPS, leading to an electron-transfer capacity higher than that for Fe(OH)3 and control reactors, which seemed to be an important reason for the improved anaerobic performance. The gene function prediction also showed a different degree of expression of functional genes involved in amino-acid, polysaccharides, and inorganic ion transport and metabolism in the presence of Fe2O3 and Fe(OH)3. This study helped to give a more comprehensive insight for the mechanisms of ferric oxides on the improvement of anaerobic digestion.

A research challenge vision regarding management of agricultural waste in a circular bio-based economy

Agricultural waste is a huge pool of untapped biomass resources that may even represent economic and environmental burdens. They can be converted into bioenergy and bio-based products by cascading conversion processes, within circular economy, and should be considered residual resources. Major challenges are discussed from a transdisciplinary perspective, focused on Europe situation. Environmental and economic consequences of agricultural residue management chains are difficult to assess due to their complexity, seasonality and regionality. Designing multi-criteria decision support tools, applicable at an early-stage of research, is discussed. Improvement of Anaerobic Digestion (AD), one of the most mature conversion technologies, is discussed from a technological point of view and waste feedstock geographical and seasonal variations. Using agricultural residual resources for producing high-value chemicals is a considerable challenge analysed here, taking into account innovative eco-efficient and cost-effective cascading conversion processes (bio-refinery concept). Moreover, the promotion of agricultural residues-based business is discussed through industrial ecology, to promote synergy, on a local basis, between different agricultural and industrial value chains. Finally, to facilitate a holistic approach and optimise materials and knowledge flows management, the connection of stakeholders is discussed to promote cross-sectorial collaboration and resource exchange at appropriate geographic scales.

Disintegration of sewage sludges and influence on anaerobic digestion

The improvement of anaerobic digestion was investigated in an interdisciplinary research group. Using four different methods of mechanical cell disintegration the influence of the degree of disintegration and the digestion parameters on the performance of the anaerobic process was investigated. Analytical methods to describe the degree of cell-disruption had to be developed. The best results were obtained using a stirred ball mill and a high-pressure homogenizer. As a result of disintegration the degradation is accelerated and the digestion time can be reduced, especially when using immobilized micro-organisms. The treatment of digested sludge by ozonization respectively by mechanical disintegration led to an improved biodegradability of residual organic compounds. In a following second anaerobic process the treated sludge reached an even higher degree of degradation. On the other hand the disruption of the particle structure leads to an increase in polymer-demand and no improvement in dewatering results. Sludge water, returned to the aeration tanks, is slightly more polluted, especially the concentration of ammonia increases because of the better anaerobic digestion.

Disintegration of sewage sludges and influence on anaerobic digestion

The improvement of anaerobic digestion was investigated in an interdisciplinary research group. Using four different methods of mechanical cell disintegration the influence of the degree of disintegration and the digestion parameters on the performance of the anaerobic process was investigated. Analytical methods to describe the degree of cell-disruption had to be developed. The best results were obtained using a stirred ball mill and a high-pressure homogenizer. As a result of disintegration the degradation is accelerated and the digestion time can be reduced, especially when using immobilized micro-organisms. The treatment of digested sludge by ozonization respectively by mechanical disintegration led to an improved biodegradability of residual organic compounds. In a following second anaerobic process the treated sludge reached an even higher degree of degradation. On the other hand the disruption of the particle structure leads to an increase in polymer-demand and no improvement in dewatering results. Sludge water, returned to the aeration tanks, is slightly more polluted, especially the concentration of ammonia increases because of the better anaerobic digestion.