Methane Content In Biogas Research Articles

Покращена технологія отримання біогазу з урахуванням термічної та біотехнологічної стабілізації в реакторах біогазової установки

In any biotechnological process, biological agent - microorganisms, its nature and physiological and technological properties plays a major role. At the same time, the temperature of the fading mass is a very important factor in the effective process of fermentation. The analysis of recent researches and publications has shown that one of the promising directions for increasing the efficiency of biogas plants operation is also the development of highly efficient technology, which provides for more intensive processing of different types of substrates in biogas plants. The purpose of the study is to develop a highly efficient technology for obtaining maximum volumes of biogas by preparing input substrates with the optimal dosage of special impurities, as well as for balanced use of excess heat energy of the cogeneration unit in the summer. One of the ways to improve the energy efficiency of the BSU's work is to reduce the cost of energy for ensuring its technological processes while increasing the amount of the initial product (biogas) that can be provided by optimal dosage and destructive (cavitation) treatment of various types of raw materials, optimal heating and mixing with the required loading intensity The substrate, which will ensure the efficient use of the entire volume of the BSU reservoir, excludes the formation of dead zones, the stratification of the sediment, from Taeda mineralized sediment and appearance peel and promote the equalization of temperature field and improves gas. The process of intensifying the digestion is that the flow of different types of raw materials in the rotary-pulsating apparatus of the BSU is shredded to the required microscopic level and homogenized. In the course of processing, the bonds of long fibers (lignin, cellulose), which diminish in sizes up to 0,1 microns, are torn. Therefore, bacteria that are involved in the process of biogas production, it is easier to spread biogenic materials. As a result, methane content in biogas increases to 70-75%. In the summer and autumn transition to the thermophilic fermentation regime, with the same volume of methane, the biogas output will increase by at least 1.5-2 times, which additionally leads to a decrease in the cost of 1 kW of installed capacity. The energy used to heat the reactor for 12 hours, in all other equal conditions, during its operation in the thermophilic mode should be: in the winter period, 0.83 MW·h., In the summer - 0.52 MW·h. It was established that an increase in the thickness of the thermal insulation layer by 50 mm helps to reduce heat loss through the surface of the reservoir by 15 ... 20 %, which in turn leads to a reduction in energy consumption, which, according to the mesophilic operating mode, is 3.6% or 21 kW·year/m³. The payback period of the event - less than 6 months. The working time of the cogeneration unit, which should be (provided that the new portion of the biomass is warmed up) is calculated: for 1 hour - in the first and in the second variant - 0.8 hours; in 12 hours: 0.35 hours in the first version, and 0.22 hours in the second one. It is shown that the nominal thermal power of the cogeneration unit is sufficient to cover the heat load and to transfer the operation of the reactors of the BSU from thermotolerant to the thermophilic regime even during the cold period of the year. It has been found that energy expenditures on the intensification of anaerobic fermentation of biomass for the climatic conditions of the Kiev region can reach up to 250 kWh/year for 1 m³ of mesophilic regime and nearly 400 kWh/year for 1 m³ for the thermophilic regime of the BSU. The application of highly efficient technology for biogas production on the basis of destructive (cavitation) treatment of various types of raw materials with the optimal dosage of special impurities does not allow the foam formation and floating crust in the upper part of the bioreactor and promotes more efficient use of the entire volume of the reactor BSU. Keywords: biogas, substrate, methane tank, temperature conditions, energy-saving technology

Incorporating anaerobic co-digestion of steam exploded or ammonia fiber expansion pretreated sugarcane residues with manure into a sugarcane-based bioenergy-livestock nexus

The co-digestion of pretreated sugarcane lignocelluloses with dairy cow manure (DCM) as a bioenergy production and waste management strategy, for intensive livestock farms located in sugarcane regions, was investigated. Ammonia fiber expansion (AFEX) increased the nitrogen content and accelerated the biodegradability of sugarcane bagasse (SCB) and cane leaf matter (CLM) through the cleavage of lignin carbohydrate crosslinks, resulting in the highest specific methane yields (292–299 L CH4/kg VSadded), biogas methane content (57–59% v/v) and biodegradation rates, with or without co-digestion with DCM. To obtain comparable methane yields, untreated and steam exploded (StEx) SCB and CLM had to be co-digested with DCM, at mass ratios providing initial C/N ratios in the range of 18 to 35. Co-digestion with DCM improved the nutrient content of the solid digestates, providing digestates that could be used as biofertilizer to replace CLM that is removed from sugarcane fields during green harvesting.

Technological Solution of Biogas Output Increasing at Grain Distillery Spent Wash Fermentation

Background. Distillery spent wash is the main waste of the alcohol industry. This is highly concentrated wastewater, which is characterized by high chemical oxygen demand (COD) values – up to 60–120 g O 2 /dm 3 – and low pH values – up to 3.7. It makes its processing a complicated task. One of the methods of its utilization is anaerobic fermentation with the production of biogas. Inert carriers for microorganism immobilization or granulation are used to intensify the process of anaerobic treatment and increase sludge concentration. Due to the high concentration of anaerobic microorganisms in granules, compared to the number of microorganisms in free-floating active sludge, the process of methanogenesis is more intensive with a high yield of biogas and a decrease in COD. Objective. To determine the possible centres of anaerobic sludge granulation in highly concentrated waste of alcohol production to increase biogas output in the process of waste treatment. Method s . Activated carbon, modified carbon on which surface calcium ions were precipitated, FeCl 3 , silica gel based sorbent, talc based sorbent were used to form pellets as the centres of microorganism accumulation. Results. Pellets have not been formed with the use of activated carbon; modified carbon with calcium ions; silica gel based sorbent and ferrum compounds. Pellets of activated sludge were received with the use of talc based sorbent – formation of initial biofilm on a carrier was observed on the third day of fermentation and then it was growing in pellets. Conclusions. It was demonstrated that for highly concentrated waste effluents of a distillery (grain distillery spent wash), which after co-fermentation with poultry manure contain volatile fatty acids in concentration 800–2000 mg/dm 3 , it is needed to use sorbents to receive microorganism pellets as a centre of granulation. Sorbents must contain donors and proton acceptors. It was established that the use of granular activated sludge for the distillery waste purification improves the efficiency of COD and Biochemical Oxygen Demand removal by 15–17%, increases biogas output by 26 ± 2% and biogas methane content by 8 ± 1%.

Effect of initial pH on anaerobic co-digestion of Salvinia molesta and rice straw for biogas production and kinetics

Abstract The goal of this study was to investigate the effect of initial pH (6, 6.9 (control), 7, and 8) on biogas production from co-digestion of Salvinia molesta (SM) and rice straw (RS). The ratio of SM and RS was varied to be 40:60 and 0:100. This study used lab-scale batch anaerobic digesters operated at room temperature for 40 days. The results showed that ratio of 40:60 produced more total biogas yield (53.25–61.38 mL/g total solid (TS)) than ratio of 0:100 (45.98–51.20 mL/g TS) at all initial pH variations. Substrate pH during digestion in ratio of 40:60 was more stable than that in ratio of 0:100. The highest total biogas yield in ratio of 40:60 and 0:100 was obtained at initial pH of 8 (digester of P8, 61.38 mL/g TS) and 7 (digester of Q7, 51.20 mL/g TS) respectively because a large amount of volatile fatty acids (VFAs) was converted to biogas. Biogas from ratio of 40:60 contained higher methane content than that from ratio of 0:100. Furthermore, in ratio of 40:60, the methane content of biogas was not affected significantly by variation of initial pH. Comprehensively, the best condition for biogas production was achieved at ratio of 40:60 with initial pH of 8. In order to modeling the kinetics of biogas production, the Cone model was the best of all proposed models (modified Gompertz, first order kinetic, Cone model) because it resulted Mean Absolute Percentage Error (MAPE) of 8.42–18.60% while the others showed MAPE of more than 20%.

English

This study focuses on the production of biogas from slaughter house waste to generate optimal methane yield which has high calorific value under optimum temperature, pH and substrate proportion (blood, manure and undigested food material). In this study, two different kinds of experiment were done. The first experiment was carried out to determine the pH, total solid, volatile solid and ash content of each type of waste fermented independently at optimal temperature (35°C) and pH 7. The second experiment was done by mixing three types of wastes based on crossed D-optimal design expert software, a well-accepted statistical technique used to design and optimize the experimental process. It involves choosing the optimal experimental design and estimating the effect of the several variables which have 42 runs at different proportions of the substrates. After the experiment, the following parameters: methane content and volume of biogas, pH, temperature, total solid, volatile solids, and ash content of each type of waste were determined. From individual type of 0.351 sample waste (blood, manure and undigested content), maximum biogas production and methane composition obtained were 01, 71, 41 and 0%, 66% and 54%, respectively. From the 42 runs experimental result, the best optimal methane composition and biogas produced were 79.26% and 0.381 l/g, respectively. Optimal conditions included 20% blood, 20% manure, and 60% undigested content substrate at pH 7.88 and t 32.49°C temperature. Key words: Digester, biogas, methane, anaerobic digestion, abattoirs.

Antioxidant activity of plant extracts and their effect on methane fermentation in bioreactors

Abstract Extracts of Solidago virgaurea L. (European goldenrod), Lavandula angustifolia Mill. (lavender) and Arnica chamissonis Less. (arnica) were tested as potential additives for methane fermentation in bioreactors, as it was hypothesized that their antioxidant properties may improve biogas production efficiency. Hence, methane fermentation of maize silage with the addition of tested extracts was performed in eudiometers, and both the biogas volume and methane content in biogas were measured. In addition, antioxidant properties, such as reducing power and 1,1-diphenyl-2-picrylhydrazyl free radical-scavenging activity, were determined spectrophotometrically. The results showed that only the addition of a goldenrod crude extract caused a significant increase in biogas yield, despite the fact that it presented the lowest antioxidant activity of the three tested species. No significant differences in biogas yield were found between the other two additives and the control. Biogas production efficiency was not correlated with the antioxidant activity of the crude extracts. Hence, the increase in methane fermentation efficiency in the case of goldenrod supplementation might have resulted from some other non-antioxidant compounds occurring in this species.

Analysis of Product and Temperature of Biogas Combustion in Various Air Biogas Equivalence Ratio and Methane Content

Biogas resulted from anaerobic digestion of organic compounds have various methane content depend on the type of the degraded material. The methane content of biogas is range between 40–80% that influence the heating value and combustion characteristic of that biogas. The higher methane content can be obtained through upgrading biogas by removing CO2 and other trace components like H2S, NH3, and water vapor. This research was a simulation of product composition and temperature of biogas combustion in various methane content and air biogas equivalence ratio. Biogas combustion was done in combustion chamber at constant pressure of 1 atm. Biogas and air enter into combustion chamber at temperature approximately of 30 °C as the common ambient temperature in Indonesia. The input air was designed higher than stoichiometric need in order to reach complete combustion. Combustion reaction between methane and O2 then carried out in the combustion chamber to produce CO2 and H2O. The product gases consisting of CO2, H2O, N2, and excess O2, bring heat from combustion reaction and exit from combustion chamber at the higher temperature. The analysis was done for methane content range between 20 and 100% with air biogas equivalence ratio from 1 until 3. The simulation result showed that for V m3 biogas, the combustion gases could reach 0.12271 until 1.26798V gmol with temperature above 700 °C until above 1900 °C. More than 50% component in the combustion gases is N2 as inert material from input air to combustion chamber.

Optimization of performance and emissions in a biogas–diesel dual fuel engine with cerium oxide nanoparticle addition

This study was carried out on a diesel engine operated in dual fuel mode by introducing biogas in the intake air stream. Cerium oxide (CeO2) nanoparticles in varying concentrations were used as diesel additive. Performance and emission tests were carried out to evaluate the effects of five input parameters, namely, CeO2 concentration, torque, biogas flow rate, methane fraction of biogas, and intake temperature. Taguchi’s method was adopted to reduce the number of experimental trials. Signal-to-noise ratio variations were studied and analysis of variance was carried out to obtain the optimum combination of operating parameters and their contributions towards the performance and emission indices. Results showed that low biogas flow rates ensure better thermal and volumetric efficiency and low HC and CO emissions. High biogas flow rates provide significant reduction in diesel consumption and NOx emissions. Increasing the methane content of biogas lowers diesel consumption and emissions of HC and CO. Adding 25 mg/L of CeO2 to diesel improves brake thermal efficiency and lowers all emissions. While manifold heating improves brake thermal efficiency, low intake temperature is preferred from the standpoint of volumetric efficiency and emissions.

Improved methane production of corn straw by the stimulation of calcium peroxide

This research focused on the effect of calcium peroxide (CaO2) addition on anaerobic digestion (AD) of corn straw. It was found that the CaO2 dose of 0.032–0.256 g·g−1 TVS (total VS of substrate and inoculum) had positive effect on the AD of corn straw by improving methane yield and content in biogas. Maximum methane yield was achieved at the CaO2 dose of 0.032 g·g−1 TVS, which was 241.6 mL·g−1 VSS (VS of substrate) and 11% higher than that of the control. Methane content in biogas also increased according to the in situ immobilization of CO2 by Ca(OH)2 that produced via the reaction of CaO2 with water (XRD analysis results). Microbial community structure was significantly affected by CaO2 addition. The variation of bacterial community structure led to higher hydrolysis rate, and the variation of archaea community structure ensured the proceeding of methanogenesis process. The use of CaO2 could be a cost-effective method to improve methane production of corn straw because it avoids harsh condition and high cost (e.g., chemical and energy inputs) associated with conventional chemical treatment techniques. The digestate from the AD with the addition of CaO2 can contain high CaCO3 content, making it a potential soil amendment for acidic soil.

UTILIZATION OF POULTRY MANURE IN BIOGAS PRODUCTION AS AN ALTERNATIVE TO LIQUIEFIED PETROLEUM GAS

Egypt is facing a shortage of traditional fuels. Poultry farms consume a huge amount of liquefied petroleum gas (LPG) cylinders for heating purpose in winter, which affects the needs of the domestic sector. Poultry Manure is difficult to dispose and its accumulation causes spreading of harmful insects and pests which leading to the dissemination of various diseases that are transmitted to humans and animals and pose a threat to public health. While poultry wastes can be anaerobically fermented to produce biogas to make self-sufficiency of methane. Poultry manure (PM) contains high percentage of nitrogen though it must be co-digested with other substrates to adjust carbon nitrogen ratio to produce biogas with high quality and high percentage of methane. Poultry manure is co-digested with Banana Peels (BP). A simple setup was used to digest the mixed substrate PM /BP with different ratios. PM /BP mixtures at different ratios -5 mixtures- were digested. Mixtures are as follows BP and PM was mixed at ratios 1-3, 1-1, 3-1 respectively in addition to BP and PM only. Five digesters were used to carry out experiments. Biogas was collected and measured daily. The studied parameters were pH, C/N ratio, biogas yield, and methane content. The best co-substrates with the highest percentage of methane content and highest amount of biogas produced are 50% BP+50%PM.

Anaerobic digestion of thermal pre-treated emulsified slaughterhouse wastes (TESW): Effect of trace element limitation on process efficiency and sludge metabolic properties

Slaughterhouse solid wastes, characterized by a high lipid content, are considered a valuable resource for energy production by means of anaerobic digestion technologies. Aim of this study was to examine the effect of trace element limitation on the mesophilic anaerobic digestion of thermally pre-treated emulsified slaughterhouse wastes (TESW). Under two distinct experimental periods (Period I – low and Period II – high trace element dosage respectively) a CSTR with sludge recirculation was operated at increasing organic loading rate (OLR) from 1.5 to 10 g L−1 d−1. Under optimum conditions, COD removal was higher than 96%, biogas yield equal to 0.53 L g−1 COD feed and the biogas methane content 77%. Trace element limitation however, resulted in a dramatic decline in process efficiency, with VFA accumulation and events of extreme sludge flotation, despite that the soluble concentration of Ni, Co and Mo were between 12 and 28 μg L−1. This is indicative of mass transfer limitations caused by lipids adsorption onto the anaerobic biomass.

Establishment of analysis method for methane detection by gas chromatography

The study focused on the establishment of analysis method for methane determination by gas chromatography. Methane was detected by hydrogen flame ionization detector, and the quantitative relationship was determined by working curve of y=2041.2x+2187 with correlation coefficient of 0.9979. The relative standard deviation of 2.60-6.33% and the recovery rate of 96.36%∼105.89% were obtained during the parallel determination of standard gas. This method was not quite suitable for biogas content analysis because methane content in biogas would be over the measurement range in this method.

Effects of temperature on the performance of anaerobic co-digestion of vegetable waste and swine manure.

The amount of vegetable wastes (VW) obtained from vegetable supply chain increased rapidly in recent years in China, which has posed environmental pollution problems. In view of the high moisture and organic content of VW, anaerobic digestion (AD) has shown to be an alternative with multi-environmental benefits such as waste disposal and renewable energy production. In this research, the anaerobic co-digestion of VW and swine manure (SM) in a 10 L fed-batch anaerobic digester was investigated, and the effects of temperature at psychrophilic (20°C), mesophilic (32°C and 37°C) and thermophilic (55°C) conditions on biogas production characteristics were studied with the aim of finding the better temperature for the enhanced performance of co-digestion. The results indicated that the operation performance of the anaerobic digester were maintained stability with no accumulation of volatile fatty acids (VFA) at mesophilic and thermophilic condition, as indicated by the low VFA/alkalinity ratio, which was lower than 0.10. The results of anaerobic co-digestion also showed that the value of pH, ammonia nitrogen (NH4+-N) and VFA ranked in normal range. The optimal temperature for co-digestion of VW with SM was mesophilic digestion at 32°C. Under this condition, the biogas and methane production yields reached 463.16 L/kg VS and 256.24 L CH4/kg VS, respectively. The average methane content in biogas at 32°C was the highest and reached 55.33%. Anaerobic digestion at 37°C and 55°C provided slightly lower methane yields of 93.75 L CH4/kg VS and 143.16 L CH4/kg VS, respectively. The lowest methane yield of 22.17 L CH4/kg VS was obtained at 20°C, with 22.88% of methane composition in biogas. The pilot-scale experimental results in 3 m3 household biogas digester showed that the cumulative biogas production was 70.52 m3 during the 42 d fermentation period. The average daily biogas production was 1.680 m3 and the average content of CH4 was 58.2%. The experimental results showed that the co-digestion with VW and SM at 32°C in a household biogas system could improve the stability of anaerobic process and achieve a higher biogas yield, which can satisfy farmers’ domestic biogas demand. Keywords: vegetable wastes, swine manure, anaerobic co-digestion, temperature, household biogas digester DOI: 10.25165/j.ijabe.20181101.3706 Citation: Ren H W, Mei Z L, Fan W G, Wang Y J, Liu F F, Luo T, et al. Effects of temperature on the performance of anaerobic co-digestion of vegetable waste and swine manure. Int J Agric & Biol Eng, 2018; 11(1): 218–225.

Biomethanation of water hyacinth biomass

The aim of this study was to test practical solutions to improve biogas yield during the anaerobic digestion of water hyacinth (WH) biomass. Increasing the WH (whole plant) solid content to ∼40% through sun drying (6 h), and its subsequent digestion increased biogas yield by 14% with a higher biogas methane (75%) content. Ensilation of dried WH (40% moisture) was found effective for its preservation to ensure its continuous availability even during offseasons, but the biogas yield from six months ensilated biomass was 20% less compared with fresh WH. Co-digestion of WH with waste activated sludge and food waste revealed ∼150 and ∼400 ml biogas/g VS respectively against ∼140 ml/g VS of WH alone. The practical approaches tested in this study like pre-treatment, preservation, and co-digestion of WH found to be effective to make its bio methanation more feasible.

Start Up of a UASB Treating Malted Ingredient Manufacturing Wastewater

With a greater push to achieve waste management and renewable energy targets technologies such as anaerobic digestion (AD) have increased in popularity. One such technology option is the Upflow Anaerobic Sludge Blanket (UASB) reactor, these have been shown to be a particularly robust option for high strength organic wastewaters, such as those generated by the malted ingredient manufacturing industry. Despite their effectiveness they are reported to have lengthy and complex start ups due to the range of physiochemical and biological interactions influencing sludge blanket stability. This process can be sped up by seeding the plant from sludge from similar plants, however this is not always possible. This paper aims to investigate the start up of a full-scale mesophilic UASB treating malted ingredient wastewater that was initially seeded with a granular sludge treating dairy wastewater. Operational performance during the first 75 days of start up was comparable to that of a fully established plant with a COD removal efficiency in excess of 81.89% and a biogas methane concentration greater than 57.24%. During this period the plant remained operationally robust with the Organic Loading Rates (OLR) exuding the greatest influence on plant performance. Similar to operations during stable conditions key operational parameters such as HRT times, temperatures and pH did not exert a strong influence on the plant.

Increasing methane content in biogas and simultaneous value added product recovery using microbial electrosynthesis.

Electrosynthesis of multi-carbon compounds from the carbon dioxide present in biogas is a nascent approach towards purification of biogas. Microbial electrosynthesis (MES) cells, fabricated using different electrode materials, were operated using different electrolytes and mixed anaerobic culture as biocatalysts in the cathodic chamber under an applied cathode potential of -0.7 V vs standard hydrogen electrode (SHE). The rate of production of acetate, isobutyrate, propionate and 2-piperidinone from reduction of CO2 in the cathodic chamber of the MES was 0.81 mM/day, 0.63 mM/day, 0.44 mM/day and 0.53 mM/day, respectively. As methane was also present in the biogas, methyl derivatives of these acids were also found in traces in catholyte. It was observed that the use of nickel foam as an anode, 1 M NiSO4 solution as anolyte, graphite felt as a cathode, phosphate buffer solution as catholyte at a pH of 5.2 proved to be the best possible combination for MES for this study to get enhanced product yield at higher energy efficiency.

Effect of illumination intensity on photosynthesis assisted anaerobic digestion of cattle manure leachate for enhanced biogas production

Bio-methane is an attractive energy source which can be produced by utilization of waste sources through anaerobic digestion process. However, low methane content of biogas hinders its effective applications. In this study, photosynthesis reaction was used concurrent with anaerobic digestion as an effective controlling mechanism for biogas up-grading and enhancement of its methane content. For this purpose, photosynthesis assisted anaerobic digestion of cattle manure leachate was conducted at light intensities of 2700, 5900 and 9600 Lux in batch bioreactors. The effect of illumination intensity on COD removal, biogas composition and yield was investigated. Moreover, the concentrations of phosphate and nitrate as major intermediates in anaerobic digestion and photosynthesis processes were monitored. Results showed that COD removals of 51, 53 and 54% and specific methane yields of 0.058, 0.036 and 0.024 L CH4/g CODremoved were obtained for light intensities of 2700, 5900 and 9600 Lux, respectively. At light intensity of 2700 Lux, the highest methane content of almost 90% and nitrate removal of 48% were achieved. At this condition, the concentration of methane in biogas was high enough to be considered as a prospective energy carrier.

Co-digestion of Cattle Manure and Tea Waste for Biogas Production

The increase of world population brings energy and food requirements. Increasing energy demand drives humanity towards new energy sources and work towards energy efficiency developments. Concordantly, due to population growth, the amount of waste is also increasing and causing environmental -issues. Biogas production by co-digestion of wastes -could be a common solution to both issues. Animal manures are typically used as a main substrate in co-digestion applications. Tea waste is used as a co-substrate in this -work due to having large production and consumption volume in Turkey. The aim of this study is to emerge new methods for disposal and reuse of household tea waste. For this purpose, co-digestion method was carried out to determine the biogas potential of household tea waste. Laboratory scale batch type co-digestion is carried out for 80 days under mesophilic (37±2 o C) conditions. All reactors fed with different mixing ratio of wastes and operated with different stirring speeds. The results showed that co-digestion of the wastes have positive impact on biogas and methane yield. Optimum biogas yield is 296.89 mL/gVS and 77.10% methane content are obtained from A2 which consist of 75% cattle manure and 25% tea waste with 100 rpm stirring speed. According to the results, co-digestion of cattle manure and household tea waste both have a positive effect on biogas production and methane content of biogas.

Effects of temperature on the performance of anaerobic co-digestion of vegetable waste and swine manure

The amount of vegetable wastes (VW) obtained from vegetable supply chain increased rapidly in recent years in China, which has posed environmental pollution problems. In view of the high moisture and organic content of VW, anaerobic digestion (AD) has shown to be an alternative with multi-environmental benefits such as waste disposal and renewable energy production. In this research, the anaerobic co-digestion of VW and swine manure (SM) in a 10 L fed-batch anaerobic digester was investigated, and the effects of temperature at psychrophilic (20°C), mesophilic (32°C and 37°C) and thermophilic (55°C) conditions on biogas production characteristics were studied with the aim of finding the better temperature for the enhanced performance of co-digestion. The results indicated that the operation performance of the anaerobic digester were maintained stability with no accumulation of volatile fatty acids (VFA) at mesophilic and thermophilic condition, as indicated by the low VFA/alkalinity ratio, which was lower than 0.10. The results of anaerobic co-digestion also showed that the value of pH, ammonia nitrogen (NH4+-N) and VFA ranked in normal range. The optimal temperature for co-digestion of VW with SM was mesophilic digestion at 32°C. Under this condition, the biogas and methane production yields reached 463.16 L/kg VS and 256.24 L CH4/kg VS, respectively. The average methane content in biogas at 32°C was the highest and reached 55.33%. Anaerobic digestion at 37°C and 55°C provided slightly lower methane yields of 93.75 L CH4/kg VS and 143.16 L CH4/kg VS, respectively. The lowest methane yield of 22.17 L CH4/kg VS was obtained at 20°C, with 22.88% of methane composition in biogas. The pilot-scale experimental results in 3 m3 household biogas digester showed that the cumulative biogas production was 70.52 m3 during the 42 d fermentation period. The average daily biogas production was 1.680 m3 and the average content of CH4 was 58.2%. The experimental results showed that the co-digestion with VW and SM at 32°C in a household biogas system could improve the stability of anaerobic process and achieve a higher biogas yield, which can satisfy farmers’ domestic biogas demand. Keywords: vegetable wastes, swine manure, anaerobic co-digestion, temperature, household biogas digester DOI: 10.25165/j.ijabe.20181101.3706 Citation: Ren H W, Mei Z L, Fan W G, Wang Y J, Liu F F, Luo T, et al. Effects of temperature on the performance of anaerobic co-digestion of vegetable waste and swine manure. Int J Agric & Biol Eng, 2018; 11(1): 218–225.

An investigation on utilization of biogas and syngas produced from biomass waste in premixed spark ignition engine

Syngas and biogas are two typical biofuels generated from biomass wastes through gasification and anaerobic digestion processes, which are considered to be the future fuels for IC engines. In this work, the utilization of biogas and syngas produced from horticultural waste in a premixed spark ignition engine was investigated. An experimentally validated KIVA4-based CFD simulation integrated with CHEMKIN was performed to evaluate engine performance fuelled by syngas and biogas under both single and blended-fuel modes. Effects of ignition timing, hydrogen content in syngas and methane content in biogas on both energetic and environmental performance have been studied. The indicated thermal efficiency (ITE) of syngas fueled engine at wide open throttle (WOT) condition under maximum brake torque (MBT) operation was found to be higher than that of biogas fueled engine, meanwhile, with much lower NOx emission. In addition, a comparison of the engine performance between the single and blended-fuel modes under different syngas mixing ratios was conducted in terms of ITE and NOX emission. The results suggest that the utilization of syngas and biogas under blended-fuel mode can not only maintain the MBT energetic performance under single-fuel mode, but also show its potential in reducing NOx emission and lessening the tendency of knock onset.