The heat radiates at a rate of 1.79 kW/m2 to the bottom surface of 60 cm mitad. In the study, a typical baking of mitad of 60 cm in diameter and efficiency of 25% requires an energy of 1.424 kW. By closing this message, you are consenting to our use of cookies. Using biogas in power generation (when compared to fossil fuels) avoids additional GHG emissions (Razbani et al., 2011). The ammonium concentrations were around 1,150 mg/L, and that did not seem to be inhibitory to biological activities, as evidenced by increases in biogas production. Last but not the least, I would like to thank the technology institute official for their support in giving a piece of information regarding cafeteria energy consumption data. The calculation of flame length is as follows: Among the various types of digesters, in this section of the design, fixed dome torispherical, a continuous feed (displacement) digester is selected for the reason that relatively small amounts of slurry (a mixture of manure and water) are added daily. As shown, the average emissions from NG-fueled and biogas-fueled operations are: NO2 (30 ± 3 vs. 23 ± 4 ppm); NO (17 ± 4 vs. 10 ± 3 ppm); CH4 (1,200 ± 170 vs. 1,680 ± 200 ppm); CO2 (7.2 ± 0.1 vs. 7.7 ± 0.1%); CO (122 ± 9 vs. 142 ± 14 ppm); O2 (8.0 ± 0.1 vs. 7.2 ± 0.1%); and SO2 (0 ± 0 vs. 0 ± 0 ppm). The average mass of the dough is around 598 grams per each injera baked. The biogas or methane yield is measured by the amount of biogas or methane that can be produced per unit of volatile solids contained in the feedstock after subjecting it to anaerobic digestion for a sufficient amount of time under a given temperature. There is a lack of readily available scientific information on the quality of raw biogas, as well as on potential emissions from power generation using this biogas. The biogas stove does use 65 holes at 5 mm diameters () set at 90° to the vertical, and the flames are fairly expanded on the left area. H2S is the dominant reduced sulfur compound in the raw biogas, while n-propyl mercaptan is another one detected. The installed injera baking mechanism in the cafeteria is a traditional three-stone fireplace that lacks an energy conservation mechanism and smoke outlet. Integration of a biogas digester to a baking stove is made by a pipe for the delivery of the methane gas to the end user. With co-digestion of food waste and FOG, the runtime on biogas has increased to over 22 hr or longer (Dow, personal communication, 2016). The data indicate that the TS concentrations for PS, TWAS, and food waste are relatively consistent, while those for FOG vary considerably. Using Equation (1) and a physical property listed in Table 5, the daily total volumetric flow rate () is found to be 0.74 m3/day. Utilizing the daily biogas generated for baking injera improves the overall food making process and reduces ・〉ewood consumption by 5.4%. Based on the assessment made for injera baking, the average mass of the dough is around 598 grams per each injera baked. The geometry of the digester major components and mixing chamber shown in Table 8 is based on designation in Figure 5. The gas will leave the digester at a pressure of 74.2 kPa from the gas holder as shown in Figure 13. This enables that gas and fertilizers are produced continuously and predictably. A portable emission analyzer, ECOM J2KN Pro Industrial OCNX-IR (ECOM America, Ltd., Gainesville, GA), was acquired for this project. The output power from flame combustion required to bake injera is 5.696 kW. Process flow diagram of biogas generation, conditioning, and utilization. The results are summarized in Table 6 and the values between the portable biogas analyzer and the certified lab are comparable. Accordingly, collecting data has been made through direct measurement of the waste using a balance at the disposal site. The findings from this study include the following: With FOG and food waste making up approximately 25% of TS or VS loading to the anaerobic digesters, the digesters are being operated under stable conditions. Inside the burner head, the air/gas mixing chamber outlet is placed vertically to the surface of the burner head. Furthermore, the stove has an insulation mechanism considered to conserve the heat loss to the surrounding. Gas treatments for H2S removal include adsorption, chemical scrubbing, and biological scrubbing using biotrickling filters (Huertas et al., 2011). Historical data of this facility prior to codigestion were also included in the data analysis when appropriate, so that comparisons could be made. Many WWTPs are now in different stages of anaerobic digestion of food waste (Institute for Local Self-Reliance [ILSR], 2012; Kraemer, 2012; Moriarty, 2013; EPA 2014c). California Environmental Protection Agency. 1 gallon/day = 3.785 L/day; 1 ton/day = 2,000 lb/day = 908 kg/day. The dough is liquid enough to pour into the flat surface of the baking stove (mitad); the flat pancakes (injera) will have a smooth texture in the bottom side, the side that has direct contact with the stove (mitad); and the upper surface creates a porous-like profile called eye. After selecting the type of digester, the retention time, which is a key parameter in determining digester size, is chosen to maximize the percentage of production of biogas with respect to the retention time. Since there is 58% methane in biogas and 21% oxygen in air, volume of biogas requires volume of air or one volume of biogas requires volume of air (stoichiometric air requirement). Figure 1. The “outer mantle” of the flame is where combustion is completed with the aid of the secondary air that is drawn into the flame from the sides. 24 days is chosen as the minimum amount of time for sufficient bacterial action to take place to produce biogas and to destroy many of the toxic pathogens found in human waste, considering the diameter () and height () of mixing pit are equal (). Tests on IC engine emissions, when the engine was fueled by biogas, were also conducted by a BAAQMD-certified source tester on 10/29/14 and 10/30/14. The average power required for baking injera on mitad for a typical baking of mitad of 60 cm in diameter and efficiency of 25% is found from Equation (4) [9]. Table 4 provides some statistics on characteristics of the digestate. Selected samples were also analyzed for siloxanes (gas chromatography/flame ionization detection [GC/FID]) and VOCs (TO-15), as well as for EPA Method 3C, “Determination of Carbon Dioxide, Methane, Nitrogen, and Oxygen From Stationary Sources,” with testing by certified laboratories. The most significant components targeted in biogas conditioning/pretreatment are hydrogen sulfide (H2S), siloxanes, moisture, PM, ammonia, and CO2. Although anaerobic codigestion of food waste is a viable process, full-scale operation of this process is still new. The pressure drop in the mixing tube, which should be at least 315 mm long () [2], can be calculated as follows: The pressure drop due to the flow of the mixture in the mixing tube is checked, by first calculating the Reynolds number; then, the flow type is found to be laminar. 2, no. Biogas yield predominantly depends on the type of feedstock used. No specific discharge limits on these compounds were found from a literature search.). Permit guidance for anaerobic digesters and co-digesters, Version 2, Adopted operating and capital budget, fiscal year, Proposed operating and capital budget, fiscal year, Las Gallinas Valley Sanitation District—Biogas utilization technologies evaluation, Energy efficiency and biogas generation at wastewater plants, Central Marin Commercial Food-to-Energy (F2E) Program, a presentation to Bay Area Water/Wastewater Workforce, CA regulatory arena for dairy based anaerobic digesters.