Improve Biogas Production Research Articles

Benchmarking environmental and economic indicators of sludge management alternatives aimed at enhanced energy efficiency and nutrient recovery

Wastewater treatment plants (WWTPs) have been developed as multifunctional systems that aim to eliminate pollutants present in wastewater, manage the sludge produced and improve energy efficiency. Specifically, sludge management accounts for the largest share in operational costs. Considering the relevant role of sludge treatment within the overall management scheme, this study aims to evaluate different alternatives and strategies for sludge management and treatment from the perspective of life cycle analysis, with special emphasis on those options that reduce environmental impacts and economic costs. Two pre-treatments (chemical or thermal) and two post-treatments (composting unit followed by land application or incineration) were evaluated to improve the eco-balance of the anaerobic digestion (AD) process in terms of operational (biogas production and digested sludge), environmental and economic indicators. According to the results obtained, both sludge pre-treatment alternatives proved to be an adequate alternative to improve biogas production without negatively affecting environmental and economic impacts. Finally, if the final disposal of the digestate is analysed, its application to the soil as a biofertiliser is recommended, since it presents a better environmental profile than incineration.

Soil-Derived Inocula Enhance Methane Production and Counteract Common Process Failures During Anaerobic Digestion.

Although soil-borne methanogens are known to be highly diverse and adapted to extreme environments, their application as potential (anaerobic) inocula to improve anaerobic digestion has not been investigated until now. The present study aimed at evaluating if soil-derived communities can be beneficial for biogas (methane, CH4) production and endure unfavorable conditions commonly associated with digestion failure. Nine study sites were chosen and tested for suitability as inoculation sources to improve biogas production via in situ measurements (CH4 fluxes, physical and chemical soil properties, and abundance of methanogens) and during a series of anaerobic digestions with (a) combinations of both sterile or unsterile soil and diluted fermenter sludge, and (b) pH-, acetate-, propionate-, and ammonium-induced disturbance. Amplicon sequencing was performed to assess key microbial communities pivotal for successful biogas production. Four out of nine tested soil inocula exerted sufficient methanogenic activity and repeatedly allowed satisfactory CH4/biogas production even under deteriorated conditions. Remarkably, the significantly highest CH4 production was observed using unsterile soil combined with sterile sludge, which coincided with both a higher relative abundance of methanogens and predicted genes involved in CH4 metabolism in these variants. Different bacterial and archaeal community patterns depending on the soil/sludge combinations and disturbance variations were established and these patterns significantly impacted CH4 production. Methanosarcina spp. seemed to play a key role in CH4 formation and prevailed even under stressed conditions. Overall, the results provided evidence that soil-borne methanogens can be effective in enhancing digestion performance and stability and, thus, harbor vast potential for further exploitation.

Swine manure valorization in fabrication of nutrition and energy.

Renewable energy can boost the growing population's need and rapid budgetary development. To reduce fossil fuel consumption is the initial purpose of renewable and sustainable energy, producing valuable bio-based products. The fermenters, using for pretreatment of swine manure, and involvement of swine carcasses are reported to enhance organic loading rate followed by improved biogas yield on household digesters. The compositions such as animal residues, pathogenic microbes, pharmaceutical residues and nutrient compositions including undigested feed are still confused. Therefore, it is mandatory to optimize and stabilize anaerobic practice and digestate filtration purification for consequential fertilizer consumption. The effective bio-methane recovery from energy-rich compounds is challenging due to slow degradation procedures. The pretreatment procedure could enhance lipid depolymerization and improve anaerobic fermentation. This article deeply focuses on biodegradation of swine manure. The components of this manure were evaluated and established several approaches to improve biogas production. Furthermore, recycling of co-digestates was discussed in detail as fertilizer consumption including hygienic aspects of manure and pretreatment strategies of biomass residues. KEY POINTS: • Co-digestion of manure and carcasses enhance bio-methane production. • Removel of ammonia from biogas digester may improve bio-methane gas. • A strong antimicrobial influence has been reported on biogas production.

Effect of Clinoptilolite and Halloysite Addition on Biogas Production and Microbial Community Structure during Anaerobic Digestion.

The study presents a comparison of the influence of a clinoptilolite-rich rock—zeolite (commonly used for improving anaerobic digestion processes)—and a highly porous clay mineral, halloysite (mainly used for gas purification), on the biogas production process. Batch experiments showed that the addition of each mineral increased the efficiency of mesophilic anaerobic digestion of both sewage sludge and maize silage. However, halloysite generated 15% higher biogas production during maize silage transformation. Halloysite also contributed to a much higher reduction of chemical oxygen demand for both substrates (by ~8% for maize silage and ~14% for sewage sludge) and a higher reduction of volatile solids and total ammonia for maize silage (by ~8% and ~4%, respectively). Metagenomic analysis of the microbial community structure showed that the addition of both mineral sorbents influenced the presence of key members of archaea and bacteria occurring in a well-operated biogas reactor. The significant difference between zeolite and halloysite is that the latter promoted the immobilization of key methanogenic archaea Methanolinea (belong to Methanomicrobia class). Based on this result, we postulate that halloysite could be useful not only as a sorbent for (bio)gas treatment methodologies but also as an agent for improving biogas production.

Corrigendum: Water Science and Technology 81 (6), 1231-1241: Improving biogas production performance of dairy activated sludge via ultrasound disruption prior to microwave disintegration, M. Al Ramahi, G. Keszthelyi-Szabó and S. Beszédes, https://iwaponline.com/wst/article/81/6/1231/74038/Improving-biogas-production-performance-of-dairy?searchresult = 1.

Corrigendum: Water Science and Technology 81 (6), 1231-1241: Improving biogas production performance of dairy activated sludge via ultrasound disruption prior to microwave disintegration, M. Al Ramahi, G. Keszthelyi-Szabó and S. Beszédes, https://iwaponline.com/wst/article/81/6/1231/74038/Improving-biogas-production-performance-of-dairy?searchresult = 1.

Review on pretreatment techniques to improve anaerobic digestion of sewage sludge

Anaerobic digestion (AD) of sewage sludge is one of the most efficient, effective, and environmentally sustainable remediation techniques; however, the presence of complex floc structures, hard cell walls, and large amounts of molecular organic matter in the sludge hinder AD hydrolysis. Consequently, sewage sludge pretreatment is a prerequisite to accelerate hydrolysis and improve AD efficiency. This review focuses on pretreatment techniques for improving sewage sludge AD, which include mechanical, chemical, thermal, and biological processes. The various pretreatment process effects are discussed in terms of advantages and disadvantages, including their effectiveness, and recent achievements are reviewed for improved biogas production.

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.

Biochar improves heavy metal passivation during wet anaerobic digestion of pig manure.

Anaerobic digestion (AD) is regarded as an effective treatment to stabilize organic materials and recycle the energy in pig manure. In this study, 0%, 3%, 5%, and 7% biochar (based on dry weight) were added to pig manure to investigate its influence on improving biogas production and reducing heavy metal bioavailability. The potential ecological risk of heavy metals (namely Mn, Zn, Cu, Ni, As, Cd, Pb, and Cr) in digestates was also assessed. Results show that the methane yield was significantly (P < 0.05) increased by 26.7%, 23.0%, and 26.4% following addition of 3%, 5%, and 7% biochar, respectively. Moreover, there was a significant change in the heavy metal speciation in amendment each group. The 5% biochar group showed the highest passivation rate of Ni, As, and Pb, while the highest passivation rate of Cd, Cr, Mn, and Zn was observed with 7% biochar. Although the anaerobic digestion process slightly increased the ecological risk of heavy metals, all tested digestates were still classified as a moderate risk. Results of this study can provide a reference for the treatment of heavy metal pollution in large- and medium-sized anaerobic digesters treating pig manure.

Comparative assessment of single-stage and two-stage anaerobic digestion for biogas production from high moisture municipal solid waste.

BackgroundAnaerobic digestion (AD) is a suitable process for treating high moisture MSW with biogas and biofertilizer production. However, the low stability of AD performance and low methane production results from high moisture MSW due to the fast acidify of carbohydrate fermentation. The effects of organic loading and incineration fly ash addition as a pH adjustment on methane production from high moisture MSW in the single-stage AD and two-stage AD processes were investigated.ResultsSuitable initial organic loading of the single-stage AD process was 17 gVS L−1 at incineration fly ash (IFA) addition of 0.5% with methane yield of 287 mL CH4 g−1 VS. Suitable initial organic loading of the two-stage AD process was 43 gVS L−1 at IFA addition of 1% with hydrogen and methane yield of 47.4 ml H2 g−1 VS and 363 mL CH4 g−1 VS, respectively. The highest hydrogen and methane production of 8.7 m3 H2 ton−1 of high moisture MSW and 66.6 m3 CH4 ton−1 of high moisture MSW was achieved at organic loading of 43 gVS L−1 at IFA addition of 1% by two-stage AD process. Biogas production by the two-stage AD process enabled 18.5% higher energy recovery than single-stage AD. The 1% addition of IFA into high moisture MSW was useful for controlling pH of the two-stage AD process with enhanced biogas production between 87–92% when compared to without IFA addition. Electricity production and energy recovery from MSW using the coupled incineration with biogas production by two-stage AD process were 9,874 MJ ton−1 MSW and 89%, respectively.ConclusionsThe two-stage AD process with IFA addition for pH adjustment could improve biogas production from high moisture MSW, as well as reduce lag phase and enhance biodegradability efficiency. The coupled incineration process with biogas production using the two-stage AD process was suitable for the management of MSW with low area requirement, low greenhouse gas emissions, and high energy recovery.

Evaluation of Microaeration and Sound to Increase Biogas Production from Poultry Litter

Microaeration, wherein small amounts of air are introduced into otherwise anaerobic digesters, has been shown to enhance biogas production. This occurs by fostering the growth of facultatively aerobic bacteria and production of enzymes that enhance the degradation of complex polymers such as cellulose. The treatment of anaerobic digestate with sound at sonic frequencies (&lt;20 kHz) has also been shown to improve biogas production. Microaeration at a rate of 800 mL day−1, treatment with a 1000-Hz sine wave, and combined microaeration/sound were compared to a control digester for the production of biogas and their effect on wastewater quality. Poultry litter from a facility using wood chips as bedding was used as feed. The initial feeding rate was 400 g week−1, and this was slowly increased to a final rate of 2400 g week−1. Compared to the control, sound treatment, aeration, and combined sound/aeration produced 17%, 32%, and 28% more biogas. The aeration alone treatment may have been more effective than combined aeration/sound due to the sound interfering with retention of aeration or the formation of free radicals during cavitation. Digesters treated with sound had the highest concentrations of suspended solids, likely due to cavitation occurring within the sludge and the resulting suspension of fine particles by bubbles.

Anaerobic Digestion of Floral Waste and Methane Enrichment: A Sustainable Approach for Waste to Energy Conversion

Disposal of floral waste into water or landfill because of religious beliefs causes water and soil pollution. The purpose of present experimental work is to find an energy proficient solution for the disposal of floral waste. The method used in the present work includes anaerobic digestion of floral waste for biogas generation. The proposed method aims to follow waste-to-energy approach, for meeting the local energy demands. The techniques for getting enhanced biogas production from floral waste include novel alkaline chemical pretreatment of floral waste, and co-digestion of floral waste along with food waste. Alkaline chemical pretreatment of floral waste using sodium carbonate showed improved biogas production up to 106%, as compared to the traditional sodium hydroxide chemical pretreatment. Also, a reduction in the cost of chemical pretreatment up to 90% was possible. Co-digestion of floral waste along with food waste was also found effective for getting enhanced biogas output. A feedstock mixture of 70% of floral waste and 30% food waste could produce 32.6% more biogas than the singular feedstock in the form of floral waste. Alkaline pretreatment of floral waste using sodium carbonate and co-digestion with food waste seem to be the novelty of the work. Application of chemical absorption technique for biogas quality improvement could enrich the methane content of biogas up to 96%. Large-scale application of the proposed techniques of solid waste management can meet the energy demands at potential locations. The biogas with enriched methane content can suitable for widespread applications, such as vehicular applications and electricity generation for the benefit of the end users.

Digestividad anaeróbica de biosólidos de aguas residuales usando el sistema Oxitop para estimar la producción de biogás

Panamá experimenta un crecimiento económico sostenido en los últimos 10 año. Esto trae como consecuencia algunos potenciales problemas, como es la acumulación de biosólidos de aguas residuales (BioAR) y que estos son dispuestos en rellenos sanitarios. Por ejemplo, hasta el año 2014 se depositaron aproximadamente 75946 toneladas de BioAR en el principal relleno sanitario de Panamá. Esta situación genera una gran presión a la gestión de manejo de desechos y a nivel ambiental. En este sentido, nuestra investigación se basó en el estudio de digestividad anaeróbica de BioAR usando el sistema Oxitop, a fin de estimar la cinética y potencial generación de biogás para su posible aprovechamiento. La caracterización de BioAR estudiados de diversas actividades económicas indican su viabilidad para usarlos, dada sus bajas concentraciones de contaminantes y su alto contenido de materia orgánica. Los ensayos de digestividad indican que los rangos de producción de biogás estuvieron entre 9.6 y 41.56 mL CH4/g SV. Dichos valores son bajos en comparación con los reportados en la literatura y no tendrían la capacidad para sostener una actividad de generación eléctrica; sin embargo, es posible aprovechar estos biosólidos si son mezclados con otros sustratos orgánicos para mejorar los rendimientos de producción de biogás.

Pretreatment of Animal Manure Biomass to Improve Biogas Production: A Review

The objective of this research is to present a review of the current technologies and pretreatments used in the fermentation of cow, pig and poultry manure. Pretreatment techniques were classified into physical, chemical, physicochemical, and biological groups. Various aspects of these different pretreatment approaches are discussed in this review. The advantages and disadvantages of its applicability are highlighted since the effects of pretreatments are complex and generally depend on the characteristics of the animal manure and the operational parameters. Biological pretreatments were shown to improve methane production from animal manure by 74%, chemical pretreatments by 45%, heat pretreatments by 41% and physical pretreatments by 30%. In general, pretreatments improve anaerobic digestion of the lignocellulosic content of animal manure and, therefore, increase methane yield.

Effect of a Sono-Thermal Pre-treatment Over Methane Production, Specific Activities and the Microbial Community of Sludge Anaerobic Digesters

As pre-treatment processes improve biogas production during anaerobic digestion of sewage sludge, it is expected that the microbial communities of digesters will adapt to the exposition to pre-treated substrate in terms of their composition or activity. In this study, the influence of sono-thermal pre-treatment over the microbial communities of digesters operated at decreasing solids retention times (SRT) was assessed. Differences in the microbiome and specific activities were observed and associated with pre-treatment and SRT. Pre-treatment increased methane yields (19.1–29.9%), bacterial range-weighted richness (27.8–46.5%) and archaea concentration (one order of magnitude in terms of 16S rDNA gVS−1), without causing process inhibition or instability. No effect over archaea richness was observed, which was dominated by the presence of acetoclastic methanogens. Hydrolytic and acidogenic activities were similar among the reactors and across SRT, with values of 1.55–2.28 gCOD−1d−1 and 1.45–1.88 gCOD−1d−1, respectively. Methanogenic activity showed a positive correlation with SRT, with values of 0.12–0.13 gCOD gVS−1 d−1 at 7.5 days SRT and 0.31–0.37 gCOD gVS−1 d−1 at 30 days SRT. Overall, the results shown that the main drivers of the observed effects over methane yield and the microbiome were organic loading rate and the solubilization caused by pre-treatment.

Investigation of different pre-treatments of chromium leather shavings to improve biogas production

Chromium shavings are wet by-products of the leather industry, of which thousands of tons accrue worldwide during leather manufacture. Due to their chromium content, chromium shavings are responsible for the most important ecological challenges caused by the leather industry. They are stable towards temperatures of up to 110 °C and enzymatic degradation. This high stability is caused by the three-dimensional native structure, typical for collagen, and additional chemical cross-links between the collagen fibres achieved by Cr3+ salts in the tanning process. Therefore, hitherto chromium shavings are not utilized industrially to produce biogas. In order to generate biogas, this stable structure has to be denatured. Chromium shavings were pre-treated by extrusion and hydrothermal methods. To prove the enzymatic degradability, the different pre-treatments were evaluated by differential scanning calorimetry (DSC), enzymatic assays, and by measuring the solubility in water. The biogas production potential was investigated using batch trials to examine feasibility. Results demonstrated that both pre-treatments allowed enzymatic attack and increased degradability of the chromium shavings reducing the lag-phase of biogas production and the remaining waste.Graphical abstract

Potential Recovery of Biogas from Lime Waste after Juice Extraction Using Solid–Liquid Extraction Process

A large percentage of fruit mass is left as waste after the consumption or processing of citrus fruits. The inappropriate disposal of these wastes directly leads to environmental and economic concerns. However, scientific investigations have demonstrated that citrus wastes, due to their high concentration in soluble sugars, can be a source of cellulosic biomass for biogas recovery. d-Limonene, the major constituent of essential oils present in citrus wastes, is however, known to hamper the conversion process of citrus wastes to biogas. With the aim of improving biogas production, a study on the pre-treatment of lime fruit waste to reduce the effect of d-limonene was carried out. The pre-treatment process was done using hexane as the solvent in a solid–liquid extraction process to leach out essential oils from lime wastes. Solid–liquid extraction was carried out in a Soxhlet apparatus with pulverized lime waste at 68 °C for 180 min; then the residue was washed and aerated. From the pre-treatment procedure, 21.3 mL of essential oil was recovered, indicating an oil yield of 3.8%. Substrates of untreated and pre-treated lime waste were digested in batches under mesophilic conditions for a period of 28 days. The biogas yield of each substrate was evaluated and the results compared. Substrate of untreated lime waste yielded 66.9 mL/g VS. biogas after the digestion period. In comparison, pre-treated lime waste gave a better biogas yield of 93.2 mL/g VS. after 28 days, indicating an improvement in biogas yield by about 40%. The findings of this research show that there is a viable recovery option of biogas from lime waste, and recommendations of this research can be further explored to develop an economically viable biogas plant process that efficiently utilizes citrus wastes. This would boost the drive of government towards alternative sources of energy and also fulfil two of the sustainable development goals presented by the United Nations.

Feasibility analysis for reduction of carbon footprint in a wastewater treatment plant

This study presents an integrated feasibility analysis approach to reduce the carbon footprint in the largest Italian wastewater treatment plant (WWTP). Firstly, a model-based feasibility analysis was carried out to assess the applicability of upgrading scenarios, for an ongoing anaerobic sludge digestion process. Application of dynamic sludge thickener, as well as hybrid thermo-alkali pre-treatment of waste activated sludge, were assessed to enhance the biogas production in the WWTP. Further, an implementation of the selective membranes was proposed and studied to upgrade the produced biogas in sludge treatment units to biomethane with an average efficiency of 98.6%. Model-based sludge pre-treatment and biogas upgrading strategies were developed and evaluated in terms of mass, energy, and greenhouse gas emission balance. The obtained results prove that practicing the proposed upgrading scenario can lead to an 18% improvement in biogas production and a significant reduction of thermal energy auto-consumption and total greenhouse gas emissions. In the second phase, the laboratory-based feasibility analysis was performed about the integration of microalgae technology into the current process of the WWTP. A planar photobioreactor was built to estimate the volumetric mass transfer coefficient (KLa) and CO2 consumption of the reactor. By the use of 44 and 76 μmol/m2/s light intensities, the results show 80% and 70% reductions in total CO2, respectively. The tested configuration guaranteed 11.763 and 27.943 mg/l/h CO2 consumptions, as well as 0.5775 h−1 and 17.7 h−1 KLa values. Overall, the results prove that applications of the technologies proposed in this study can significantly reduce the carbon footprint of the WWTP.

Wheat Straw Optimization via its Efficient Pretreatment for Improved Biogas Production

The complex indigenous configuration of non-bio-labile wheat straw necessitates its pretreatment to optimize the breakdown of its structural components for its ultimate conversion into biogas by means of anaerobic digestion. In this research work, wheat straw was pretreated with potassium hydroxide (KOH) to facilitate its improved biodegradability. The pretreatment of wheat straw was also obvious in terms of its crystallinity resulting in the improved amorphous regions compared to the control wheat straw. The results showed that pretreated wheat straw digestion transpired into comparatively higher removal of TS (86%), VS (89%) and total lignin, cellulose and hemicellulose (22%) than that obtained with control wheat straw. Maximum biogas production accrued was 1550 mLN per day with optimized dosing of KOH compared to 967 mLN per day obtained with control wheat straw, implying that the cumulative biogas production was improved by 45% using pretreated wheat straw than that using control wheat straw. These results suggested that pretreated wheat straw digestion led to a significant improvement in the biogas yield.

Improving Biogas Production by Co-digestion of Banana Stem Juice with Agro-Based Material Washings and Digestate Along with Microbial Culture

Biogas production carries a huge scope in India for the efficient utilization of agricultural wastes in an eco-friendly manner. The anaerobic digestion process involves the conversion of different solid and liquid wastes with high organic content to biogas primarily containing methane that is used for heating and electricity generation. India has enormous quantity of cultivable land, and thus substantial agricultural remains are generated here. About 100 metric tons of banana stem is generated per hectare annually as waste after harvesting the banana fruit. Banana stem juice (BSJ) was extracted and explored for its potential in biogas production. The present study is focused on co-digestion of blending BSJ with agro residues washings viz. bagasse washing (BW) and wheat straw washing (WSW) for biomethanation. The effect of adding the Pseudomonas aeruginosa on biogas generation was also studied. The microbial consortia play vital roles in the degradation of organic matters. Methane share in biogas produced during anaerobic fermentation of BSJ was increased from 43 to 61% with the addition of P. aeruginosa due to possible degradation of fatty acids and proteins. The digestion of BSJ using microbial consortia of digestate augmented with P. aeruginosa showed the highest amount of gas (3350 mL/L) containing 79% methane share. The Co-digestion of BSJ with BW and WSW was found to be highly effective and showed the potential to increase the efficiency of the biogas plants of paper mills for methane production. BSJ alone as well as with BW and WSW showed excellent potential for biomethanation.

Utilization of pumice for improving biogas production from poultry manure by anaerobic digestion: A modeling and process optimization study using response surface methodology

The aim of the present work was to optimize and to model the biogas production yield from anaerobic digestion (AD) of poultry manure (PM) using response surface methodology (RSM). The influence of total solid percentage (TS%), inoculum ratio (%), the amount of pumice (g L−1), and particle size of pumice (mm) was investigated for cumulative biogas production, methane content in produced biogas (CH4%), and the removal percentage of chemical oxygen demand (COD% removal). The results showed that RSM with central composite design (CCD) was successfully applied to predict and model the biogas production from AD of PM. From the analysis of variance (ANOVA) results, the obtained models were highly significant with coefficient values (R2) of 0.98, 0.98, and 0.99 for cumulative biogas production, CH4%, and COD% removal, respectively. The results indicate that the obtained quadratic models are significant for the selected responses, as well as acceptable for the relationship between the investigated parameters and the responses. The optimum conditions of the investigated parameters were found by the numerical analysis method based on RSM. At the obtained optimal AD process conditions, the maximum cumulative biogas production, CH4%, and COD% removal were 8965.87 mL, 71.298%, and 68.4711%, respectively.