|Year : 2015 | Volume
| Issue : 3 | Page : 147-150
Feasibility of large amounts biogas production from garbage bioliquid
Hassan Hashemi1, Mehdi Safari2, Asghar Ebrahimi3, Mohammad Reza Samaei1, Abbas Khodabakhshi4
1 Assistant Professor of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences, Iran
2 Kurdisan Environmental Health Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran
3 Environmental Sciences and Technology Research Center, Department of Environmental Health Engineering, Iran
4 Assistant Professor of Environmental Health Engineering, School of Health, Shahrekord University of Medical Sciences, Shahrekord, Iran
|Date of Web Publication||20-May-2015|
Assistant Professor of Environmental Health Engineering, School of Health, Shahrekord University of Medical Sciences, Shahrekord
Source of Support: None, Conflict of Interest: None
Aims: One of the best available alternatives to face the energy and environment problem is to tend renewable energies. The main aim of this study is producing biogas from garbage bioliquid (leachate). Materials and Methods: This study was conducted at wide range of organic loading rate (OLR = 0.93-25 g COD l -1 d -1 ) by varying hydraulic retention times (HRT = 23 and 12 hsr) and initial COD of 1.85-25 g l -1 . pH variations, COD, SCOD, rbCOD and VFAs degradation, biogas and methane production were considered in this study. Results: The COD removal efficiencies were in the range of 76-81% depending on loading rates applied. The maximum volumetric methane production rate (VMPR) of 5.7 l CH4 l -1 d -1 was achieved at the OLR of 19.65 g COD l -1 d -1 . About 85% of removed COD during the biodegradation was converted to methane. Conclusion: The results have shown that the anaerobic sequencing batch reactor (ASBR) reactor could be an appealing option for changing composting leachate into useable products such as biogas and other energy-rich compounds, which may play a serious role in meeting the world's ever-increasing energy requirements in the future.
Keywords: Biogas, crisis, energy, leachate
|How to cite this article:|
Hashemi H, Safari M, Ebrahimi A, Samaei MR, Khodabakhshi A. Feasibility of large amounts biogas production from garbage bioliquid. Int J Health Syst Disaster Manage 2015;3:147-50
|How to cite this URL:|
Hashemi H, Safari M, Ebrahimi A, Samaei MR, Khodabakhshi A. Feasibility of large amounts biogas production from garbage bioliquid. Int J Health Syst Disaster Manage [serial online] 2015 [cited 2021 Feb 27];3:147-50. Available from: https://www.ijhsdm.org/text.asp?2015/3/3/147/157380
| Introduction|| |
The energy, water, land and natural resources have been under great pressure to support increasing world population. The availability of fossil energy has been declining worldwide. It is essential to change the global fossil-depending economy into a sustainable bio-based economy. 
Biogas technology seems promising to attain sustainable energy yields without damaging the environment. Waste management, health care and employment foundation are the benefits of biogas system. Use of biogas assures renewable energy supply and balance of green house gases. 
Biomass is a renewable energy because it contains the energy which comes from the sun. Examples of biomass include: Plants, crops, trees and garbage. 
Based on literature, waste production rate has increased by 7.3% in Iran between 2002 and 2009 so that the average waste production was about 746 gr per person per day in 2006.
Since 68.81% of solid waste is consisted of biodegradable materials, leachate production potential is high during waste management.
A significant amount of biogas can be produced in the anaerobic digestion of leachate. The leachate organic load (BOD = 34400 mg/L and COD = 53900 mg/L) is considerably higher when compared with other countries due to higher amount of organics available in developing country wastes. 
Leachate may be treated anaerobically, saving environment and converting the organic material partially to biogas energy.  Even toxic compounds may be degraded anaerobically depending on the process applied. One prerequisite is that a feed waste contains a considerable amount of organic matter that is finally converted mainly to CH 4 and CO 2 . At least 20% of energy used in the EU coming from renewable sources and 10% of the fuels used in transport being biofuels.  In this context, anaerobic digestion with biogas generation is a good answer to today's environmental challenges.  Indeed, anaerobic digestion with energy recovery produces less greenhouse gases than incineration or landfilling. 
As a rule of thumb, wastes containing less than 60% of volatile solids are rarely considered as substrates for anaerobic digestion. Therefore, with regard to the total solids content, the percentage of volatile solids, the C: N ratio and the biodegradability, composting leachate can be used proper substrate for anaerobic digestion that generate useable biogas as a source of energy.  Few studies have been conducted on the biogas production from compost leachate. Furthermore, most of those studies use synthetic leachate. Composting leachate and young landfill leachate normally contain high amounts of volatile fatty acids. These readily biodegradable volatile acids account for the bulk of the chemical oxygen demand (COD) of leachate, so the ratio of biological oxygen demand (BOD) to COD is relatively high.  The anaerobic treatment of young leachate in an anaerobic system allows the anaerobic stabilisation to terminate which was initiated in the tip.
Amongst the biological processes found in the scientific literature, ASBR have shown good removal efficiencies in pretreatment of municipal solid waste composting plant leachate. COD removal was as high as 85-90% for the whole sequential anaerobic-aerobic treatment process while the COD removal efficiency in the anaerobic stage was only 60%.  HRT of about 70 days would be needed to achieve 90% COD removal in a leachate containing in excess of about 150000 mg/l of COD which relatively large reactors are required.  Nevertheless has been claimed that the anaerobic digestion of leachate does not remove ammoniacal-N at all (often up to 1000 mg/l), and indeed is more likely to increase concentrations of this main contaminant of leachates. This study will mainly focus on the composting leachate COD removal and biogas production using ASBR process.
| Materials and Methods|| |
The total volume of reactor was 2 l that 0.5 l was filled with sludge, 1 l was completed with the addition of pretreated leachate and 0.5 l was as freeboard for biogas storage in to the headspace. The lab scale batch reactor consisted of a thermostated water bath glass container with a liquid working volume of 20 l which was maintained a temperature of 37˚C. To obtain a homogeneous suspension, feeding was injected by one etatron pump through the bottom of the reactor. The reactor content was mixed with a vertical mixer inside the reactor. At the end of each cycle, mixer was stopped and after 1 hr settling, 1l of supernatant was withdrawn from decant valve.
Bioreactor start-up and operational pattern
Experimental study was conducted at wide range of organic loading rate (OLR = 0.93-25 g COD l -1 d -1 ) by varying hydraulic retention times (HRT = 23 and 12 hr) and initial COD of 1.85-25 g l -1 . Because of the seasonal biodegradability variations and acidic nature of the composting leachate, by using higher HRT and dilution of the influent, anaerobic reactor was adopted gradually. So that was not need to supplementation alkalinity. The reactor was operated with a 24-hour cycle consisting of approximately fill (10 min of mixed fill), react (23-12 hrs), settle (1 hr), and decant (10 min) phases. Partially granulated anaerobic sludge with a total Volatile Suspended Solids (VSS) amount of 7500 mg/l, was taken from the methanogenic digester of wastewater treatment plant in Isfahan (Iran) and used as seed in ASBR reactor. Sometimes, biomass loss was occurred due to influent shock that was replaced, using 0.5 l acclimated sludge. In first runs, HRT and OLR were fixed. The influent rate was kept constant at 1 l d -1 . After steady state, HRT was decreased and OLR was increased. Adaptation of micro-organisms to the leachate and operating conditions was also pointed out along the consecutive batches.
Experimental set-up, sampling and operation
ASBR reactor was inoculated with 1 liters sludge from an anaerobic digester (North Isfahan, IR) that operated at 35°C. Washing of sludge with distilled water for remove coarse particles and then sieving with a pores diameter were 5 mm. The system was properly sealed to ensure anaerobic condition and to prevent gas leakage. Biogas exited the top of the reactor and was measured by a wet-gas meter (Elster, AMCO, Germany).
Operational issues of the each cycle including pH, COD Total , rbCOD, COD Soluble (in filtered samples) and TSS were analysed in accordance with standard methods twice a week. The pH was measured with a calibrated pH meter (Schott, Model GC 824). COD measurement was conducted based on Dichromate method (closed reflux, 5220 C, colorimetric method).  The floc/filtration method was used for measurement of the rbCOD concentration.  The volume of produced biogas was measured using a gas sampling bag and the composition of the produced biogas was determined by gas chromatography. The gas chromatograph (Auto System Perkin Elmer, USA) was equipped with a packed column (Perkin Elmer, 6' ×1.8'' OD, 80/100, Mesh, USA) and a thermal conductivity detector (Perkin Elmer, USA). An inject temperature of 150˚C was applied, and the carrier gas was nitrogen operated with a flow rate of 20 mL/min at 75˚C (25). An Agilent technologies system consisting of a 5975˚C Inert MSD with a triple axis detector equipped with a 7890A gas chromatograph with a split/splitless injector was used for the quantification and confirmation of the VFA.
| Results|| |
Variation of the pH in feed and effluent of reactor is presented in [Figure 1].
[Figure 2] is showing the removed COD in ASBR reactor at various HRTs.
The VFA removal efficiency was high throughout all testing OLRs, in excess of 85% [Figure 2].
| Discussion|| |
Feeding leachate characterization
The mixture of leachate produced in different units of Isfahan composting plant (Receiving hall, Shredding, Press and fermentation site) was obtained. Total COD of mixed leachate was measured 1.85-25 g/l. Composting leachate was pretreated by AMBR to alleviate organic loading and solids, after that injected to the ASBR.
The nature of raw leachate was acidic but after pre-treatment of leachate by AMBR, pH was reached between 7.4-8. In the beginning of each run, due to high loading the VFA accumulation led to pH decreasing fewer than 7 inside the reactor. In steady state, gradual Increasing of pH was occurred for two reasons. First, due to Ammonia production as a by-product of anaerobic digestion during mineralization of organic nitrogen, second, methanogenosis activity caused pH rising except in high loading rates. Changes in pH are illustrated in [Figure 3]. Generally, the pH value in ASBR was between 7.47 and 8.15 without any pH adjustment throughout the study. This showed the favorite conditions for anaerobic digestion.
During the start-up batch a lag can be observed in methane production in reactor. Then, during the subsequent batches the lag becomes less and less pronounced as the reaction becomes quicker. This phenomenon can be attributed to an adaptation of the micro-organisms to the waste and to the conditions of the experiment.
The study was conducted at eleven OLRs from 1.04 to 19.65 gr CODl-1 day-1 in the period of 280 days. We are determined the ability of ASBR reactor in biogas production at various OLRs and its efficiency in removal of COD, SCOD, rbCOD and VFAs. As well as the effects increasing of HRT on reactor performance was investigated. The results from the experiments are explained in the below sections.
Influent COD, SCOD and rbCOD concentrations were in the ranges of 1.85-25, 0.42-6.52 and 0.07-2.3 gl -1 respectively. In the effluent these parameters concentrations were in the ranges of 0.4-6.3, 0.1-2.4 and 0.01-0.8 g l -1 respectively. The influent and effluent ranges of BOD 5 /COD ratio are 0.28-0.38 and 0.1-0.28 respectively. When HRT was decreased from 12-23 hrs, the effluent concentrations of parameters were increased and BOD 5 /COD ratio was decreased.
Total COD, SCOD, and rbCOD removal efficiencies respectively of more than 80.3%, 80.6% and 90%were achieved at an OLR of 10.17 gr CODl -1 d -1 and a gradually decrease to an OLR of 25 grCOD l- 1 d -1 still gave COD, SCOD, rbCOD and BOD 5 removal efficiencies respectively of 75%, 63% and 80%. Removal efficiency of rbCOD was higher than COD and SCOD. These parameters removal efficiency was initially high and relatively stable but decreased when OLR was increased to 25 grCOD l -1 d -1 Average removal efficiency of COD, SCOD and rbCOD in HRT of 24 hrs were 81%, 84% and 91.3%. But in HRT of 12 hrs was decreased to 76%, 78% and 85% respectively.
At any microorganism concentration, the food to microorganism ratio (F/M) is high right after the feed cycle is completed. This provides a high driving force for metabolic activity and high overall rates of waste conversion to biogas.
Up to the end of the react cycle the substrate concentration is minimum, providing low F/M ratio for biomass flocculation.
The biogas produced during the anaerobic degradation is a valuable resource of energy. 
The exact expectation of the producible biogas amount and its methane content is one of the most important aspects of an anaerobic reactor.
The quality and quantity of the biogas have special importance.
The chemical compositions of a leachate determine the potential biogas yields, as well as the gas composition. The biogas production versus OLRs has been shown in [Figure 3]. The biogas was produced 0.55 l when the OLR was1.04 gr COD l -1 d -1 and gradually increased to an OLR of 10.08 gr COD l -1 d -1 still gave 5.68l.
Rashidi et al., (2012) results indicated that an amount of 33504 m 3 /d biogas can be produced in Tehran's landfill that eventually would be sufficient to run a power plant of 3.4 MW capacities. ,
The range of the methane content of biogas was between 55-65%, which is comparable with the reported range of 67 ± 81% for the leachate.
When the OLR was 1.04 gr COD l -1 d -1 the produced methane was 0.3 l and gradually increased to an OLR of 10.08 gr COD l -1 d -1 still gave 3.12l. Methane production for reactor was in the range of 0.29-0.42 l CH 4 /g COD removed. When the OLR was 10.08 gr COD l -1 d -1 and HRT was 23 hrs, the biogas production rate was 5.68 l but in HRT of 12 hrs and OLR of 19.65 gr COD l -1 d -1 , the biogas production rate was 6.65 l.
Timur and Ozturk (1999) reported that, about 83% of COD removed is converted to methane. Also each g of VSS in ASBR reactors is capable of converting a daily maximum of 1.06 g of COD to the methane. 
| Conclusion|| |
Compost leachate may be treated anaerobically, saving environment and converting the organic material partially to biogas energy.
The COD removal efficiencies were in the range of 76-81% depending on loading rates applied. The maximum volumetric methane production rate (VMPR) of 5.7 l CH4 l -1 d -1 was achieved at the OLR of 19.65 g COD l -1 d -1 . About 85% of COD removed during the treatment was converted to methane. The results have shown that the ASBR reactor could be an appealing option for changing composting leachate into useable products such as biogas and other energy-rich compounds, which may play a serious role in meeting the world's ever-increasing energy requirements in the future.
| Acknowledgments|| |
We are grateful to the Waste Management Organization of Isfahan for allowing the collection of leachate samples.
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[Figure 1], [Figure 2], [Figure 3]