Model for Assessment Evaluation of Methane Gas Yield Based on Hydraulic Retention Time during Fruit Wastes Biodigestion

This paper presents an assessment evaluation of methane gas yield using a derived model based on the hydraulic retention time (HRT) of the feed stock (waste fruits) undergoing biotreatment in the digester. The derived model;γ = e(3.5436 α + 2.0259) indicates an exponential relationship between methane yield and the HRT. Statistical analysis of the model-predicted and experimental gas methane yield for each value of HRT considered shows a standard error of 0.0081 and 0.0114% respectively. Furthermore, the correlation between methane yield and HRT as obtained from derived model and experimental results were evaluated as 0.9716 and 0.9709 respectively. Methane gas yield per unit HRT as obtained from derived model and experiment are 0.0196 and 0.0235 (m3kg-1 VS) days-1 respectively. Deviational analysis indicates that the maximum deviation of the model-predicted methane yield from the corresponding experimental value is less than 16%. It was also found that the validity of the model is rooted on the expression 0.2822 ln γ = α + 0.5717 where both sides of the expression are correspondingly approximately equal.

Anaerobic Digestion of Food Waste Using UASB Sludge from a Poultry Slaughterhouse as Inoculum

In 2010, Brazil endorsed a new national policy of solid wastes, which has a very ambitious target to close up all the dumping areas and to manage adequately all the municipal solid waste, disposing in landfills only the refuse of treated municipal solid waste after 2019. Food waste is the largest representative of organic waste produced in Brazilian municipalities, which can produce both fertilizer and biogas through anaerobic digestion （AD） process, reducing in both cases greenhouse gases emissions. AD assays of some samples of restaurant food wastes were performed in batch laboratory, 500 mL reactors for determination of optimized start-up conditions. The tests were conducted in triplicate, using anaerobic sludge from a poultry slaughterhouse wastewater treatment as inoculum to start up the anaerobic biodigestors. The effect of three different substrates to inoculum mixing ratios 10：90 （S1）, 20：80 （S2） and 30：70 （S3） was evaluated. The food waste used as substrate was previously homogenized and submitted to aerobic mechanical mixing for four days before it was fed in the reactors in anaerobic conditions at the mentioned proportions with the inoculum. The reactors were maintained at 35 ℃ and under mechanical mixing at 60 rpm. The methane production was monitored until its stabilization. Results showed that S1 presented the best performance during the initial 12 d, when it totalized 526 NmLCH4/gVSsubstrate.

Apparatus Prototype for Purposes of Teaching in Bio-digesters

A mathematical model is developed based on a simplified mechanism of anaerobic digestion. The main objective is to quantitatively analyze the digestion process to optimize operating conditions and maintenance of this equipment, which could be used to test different materials and be able to apply these results to the possible scaling to bio-digesters installed in the field. The experiments were carried out in a hybrid system bio-digester photovoltaic cells. The bio-digester is made of stainless steel with dimensions to treat an average of 10 kg of raw material and produce biogas from different organic materials. The reactor has been conditioned with temperature sensors, pressure and methane gas that allow monitoring the concentration of the gas and the conditions of operation during the time of digestion. The system has a photovoltaic array to provide the energy required to keep the temperature constant, The experiment was conducted using materials such as goat manure mixed with household waste, and various formulations of these materials were prepared. The experimental results were used to test the mathematical model.

Construction Technology of Biodigesters in Senegal

Faced with the depletion of fossil energy resources and given the current context of the fight against climate change, Renewable Energies (RE) represent an increasingly growing challenge. Of all these energies, those resulting from the biomethanization of biomass now provide an opportunity in the world of farmers and breeders. The treatment of agro-pastoral residues by anaerobic digestion has been the subject of renewed interest in recent years, thanks in particular to the production of energy from biomass, not to mention the production of fertilizers from effluents. Expelled from the digesters. This method of transformation offers many environmental, socio-economic and agricultural interests. Indeed, the biogas obtained from organic matter allows, among other things, to cook, light houses, and produce electricity and heat. The objective of this study is to compare the construction techniques and costs of the biodigester models that exist in Senegal. There are many biodigesters, the choice of an installation depends on the available space and the nature of the soil. Several types of biodigester technologies are installed in Senegal. The GGC 2047 fixed dome, the RMB geomembrane and the BEG geomembrane. First we will describe the construction techniques of the modified GGC model fixed dome biodigester, then of the RMB model geomembrane and finally of the BEG model geomembrane.

Dimensioning of an Anaerobic Digester for the Treatment of Chicken Manure and for the Production of Biogas: The Case Study of a Chicken Farm in Yaokokoroko (Côte d’Ivoire)

This study allowed us to highlight the level of pollution of a BAYA River water near several poultry farms and the sizing of an anaerobic digester that will be able to treat chicken manure from a poultry farm (BRIN FOUNDATION). To evaluate this pollution, the parameters such as ammonium (NH4+), Phosphate (PO43-), Biochemical Oxygen Demand (DBO5) and Nitrate (NO3-) were determined. For sampling point P1, the concentrations in mg/L of these parameters are (25.00 ± 4.25), (0.40 ± 0.20), (98.00 ± 6.35) and (96.00 ± 5.35), respectively. On the other hand, for sampling point P2, the concentrations in mg/L of these parameters are respectively (33.00 ± 9.05), (0.70 ± 0.12), (123 ± 7.13) and (93 ± 7.10). These values indicate a strong organic pollution of the BAYA River. The determination of the different concentrations of the organic pollution parameters allowed us to evaluate the degradation and the quality of the water of the BAYA River water, by the poultry activity. However, considering the physicochemical properties of the waste (chicken manure), which is the main source of organic pollution, we have considered an energy recovery through the production of biogas. This requires the design, sizing, and implementation of an anaerobic digester in a poultry farm. Therefore, the project would require the construction of an adapted masonry type anaerobic digester with a capacity of 10 m3.

Design and Construction of an Experimental Biodigester in the Senkerfa Poultry Farm in Kankan,Guinea

This study is a continuation of our research work on the energy recovery of OM(Organic Matter)and the protection of the environment.It took place from October 1 to November 25,2021 in the poultry farm of Mr.Elhadj Daye KABA in the Senkefra district,urban commune of Kankan.During this work,we designed,built and tested a 6 m^(3)biodigester.Cow dung(2,500 kg)with 2,300 L of water served as a substrate for the production of biogas during 30 days of digestion.The following physico-chemical parameters:Temperature(T°C),Humidity(H%),Hydrogen potential(pH),Dry Matter(DM),Organic Matter(OM)and the ratio between Carbon(C)and Nitrogen(N)(C/N)of cow dung were determined,namely:T(28°);H(75%);pH(6.5);MS(15%);MO(55%)and C/N(25%).During the 30 days of digestion,the temperature varied from 27 to 35°C with an average of 30.57°C(mesophilic digestion);the pH varied from 6 to 9,with an average of 7.58;the daily production kinetics represented the four stages of digestion(hydrolysis,acidogenesis,acetogenesis and methanogenesis).The cumulative production of biogas is 198 m^(3).The composition of the biogas produced is 60%CH_(4),36%CO_(2),2%N_(2),2%H_(2)S and 1.5%H2.The biogas produced was used for lighting,water heating and cooking.These results show that the biogas produced is of good quality and remains consistent with the literature.

Design and Production of a Device for Remote Control by GSM of the Operating Parameters of a Biodigester

This article describes the design and creation of a remote monitoring and control system based on GSM(Global System for Mobile)communications technology for monitoring the key parameters of a biodigester.Biodigesters are widely used for the conversion of organic materials into biogas,thereby contributing to renewable energy production and organic waste management.However,real-time monitoring and regulation of parameters such as temperature,humidity,product gas level,pH are essential to ensure the efficiency and safety of the digestion process.We created the device for remote control of the operating parameters of the biodigester using an Arduino card,a DHT11 sensor,a pH sensor,a GSM module and a 2×16 LCD(Liquide-Crystal-Display)display.A biodigester(4.5 L plastic container)and accessories were used.The experimental device created made it possible to remotely monitor the evolution of the temperature,humidity,the gas produced as well as the pH in the digester loaded with cow dung,for 45 days.Examination of the real-time evolution of the parameters measured by the device produced showed the same results as those carried out locally by the usual instruments,with a correlation coefficient of around 98%.During this digestion period,the temperature provided by the sensor varied from 25°C to 37°C(mesophilic mode)and the humidity levels varied from 70%to 95%.The results obtained show the reliability of the device produced.This research represents a significant advance in the management of biodigestion facilities.It offers a powerful tool to maximize biogas production,reduce maintenance costs,minimize environmental impact and contribute to the transition to cleaner,renewable energy.

WASTE AND CITY FORM:RECONSIDERING THE MEDIEVAL STRATEGY

This paper argues that“new”sustainable technologies being used to manage human waste-composting toilets,bioremediation,and biodigestion-are essentially reviving the medieval strategy of waste management:containment and reuse of waste,as opposed to the modern strategy of dilution and evacuation.This debate should not occur in a vacuum,uninformed by the motivations for,and history of,the development of the modern system.Therefore,this paper more closely examines the medieval system,which closely linked waste and agricultural production.It then considers the transformation to the modern system,using the design of Leonardo da Vinci’s city of Romorantin as a case study.It is argued that this transformation was largely predicated on now-delegitimized miasmic theory,which held foul or corrupt air to be the cause of disease,and that it precipitated larger changes in the urban environment.In light of this historical view it is suggested that contemporary sustainable technologies imply larger changes in the form of human settlement,and that the nature of these changes must be explored further.

CFD analysis for mixing performance of different types of household biodigesters

Household biodigesters are self-mixing anaerobic digesters used mostly in rural areas of developing countries as a reliable source of clean cooking energy.For an efficient anaerobic digestion process,the mixing of slurry inside the digester is regarded as one of the most important parameters.In this study,the mixing of slurry in three different designs of household digesters,namely the fixed-dome digester(GGC 2047 model),plug-flow digester and prefabricated plastic digester,are investigated and compared using compu-tational fluid dynamics.A 3D transient simulation is performed using a multiphase volume of fluid(VOF)model in Ansys^(■)Fluent release 16.0.The rheological properties of the feedstock are considered identical for all three digesters.The volume of the plug-flow and prefabricated plastic digesters is designed to be 1 m^(3) while the volume of the GGC 2047 digester was 6 m^(3) as the standard size of the household digester.The regions inside the digester where the velocity of slurry is<0.02 m/s are regarded as dead zones and the obtained results were analysed and compared using velocity patterns and dead-zone formation.It is found that the prefabricated plastic digester model has a relatively higher percentage of dead volume(74.6%)and the plug-flow digester has the lowest per-centage(54%)of dead volume among digesters that were compared in this study.The study will serve as the basis for designers and researchers to improve the design of household digesters for better mixing performances.

Greenhouse Gas Emissions and Growth of Wheat Cultivated in Soil Amended with Digestate from Biogas Production

Digestate, the product obtained after anaerobic digestion of organic waste for biogas production, is rich in plant nutrients and might be used to fertilize crops. Wheat （Triticum spp. L.） was fertilized with digestate, urea, or left unfertilized and cultivated in the greenhouse for 120 d. Emissions of greenhouse gasses （carbon dioxide （CO2）, methane （CH4）, and nitrous oxide （N20）） were monitored and plant growth characteristics were determined at harvest. The digestate was characterized for heavy metals, pathogens, and C and N mineralization potential in an aerobic incubation experiment. No Salmonella spp., Shigella spp., or viable eggs of helminths were detected in the digested pig slurry, but the number of faecal coliforms was as high as 3.6 ~ 104 colony-forming units （CFU） g-1 dry digestate. The concentrations of heavy metals did not surpass the upper limits established by US Environmental Protection Agency （EPA）. After 28 d, 17% of the organic C （436 g kg-1 dry digestate） and 8% of the organic N （6.92 g kg-1 dry digestate） were mineralized. Emissions of CO2 and CH4 were not significantly affected by fertilization in the wheat-cultivated soil, but digestate significantly increased the cumulative N20 emission by 5 times compared to the urea-amended soil and 63 times compared to the uncultivated unfertilized soil. It could be concluded that digestate was nutrient rich and low in heavy metals and pathogens, and did not affect emissions of CH4 and CO2 when applied to a soil cultivated with wheat, but increased emission of N20. Key Words： biodigester, C and N mineralization potential, faecal coliform, heavy metal, pathogen, pig slurry