A two-cell manure storage system with a cover on the first cell was constructed in the late summer of 2009 in Eastern South Dakota. The covered cell acts as a simple anaerobic digester. Continuous temperature monitoring for 8 months shows the winter effluent temperature equilibrated to around 6°C, and that the effluent temperature trend lagged the ambient temperature trend by a month. Manure composition was also analyzed and was found to be relatively steady throughout the system. Volatile solids were the only component that dropped appreciably across the treatment cell, with an observed maximum of 50% reduction

Cortus, E.

Darrington, J.

English

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The Journal of Undergraduate ResearchVolume 9 Journal of Undergraduate Research, Volume9: 2011 Article 42011Long Term, Continuous Temperature Monitoringof a Simple Anaerobic Digester and Open ManureStorage Pond in Eastern South DakotaJ. DarringtonSouth Dakota State UniversityE. CortusSouth Dakota State UniversityFollow this and additional works at: http://openprairie.sdstate.edu/jurPart of the Agriculture Commons, and the Bioresource and Agricultural Engineering CommonsThis Article is brought to you for free and open access by Open PRAIRIE: Open Public Research Access Institutional Repository and InformationExchange. It has been accepted for inclusion in The Journal of Undergraduate Research by an authorized administrator of Open PRAIRIE: Open PublicResearch Access Institutional Repository and Information Exchange. For more information, please contact michael.biondo@sdstate.edu.Recommended CitationDarrington, J. and Cortus, E. (2011) "Long Term, Continuous Temperature Monitoring of a Simple Anaerobic Digester and OpenManure Storage Pond in Eastern South Dakota," The Journal of Undergraduate Research: Vol. 9, Article 4.Available at: http://openprairie.sdstate.edu/jur/vol9/iss1/4LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE... 19Long Term, Continuous TemperatureMonitoring of a Simple Anaerobic Digesterand Open Manure Storage Pond inEastern South DakotaAuthor: J. DarringtonFaculty Sponsor: Erin CortusDepartment: Agricultural and Biosystems EngineeringABSTRACTA two-cell manure storage system with a cover on the first cell was constructed in the latesummer of 2009 in Eastern South Dakota. The covered cell acts as a simple anaerobicdigester. Continuous temperature monitoring for 8 months shows the winter effluent temperatureequilibrated to around 6°C, and that the effluent temperature trend lagged the ambienttemperature trend by a month. Manure composition was also analyzed and was found to berelatively steady throughout the system. Volatile solids were the only component thatdropped appreciably across the treatment cell, with an observed maximum of 50% reduction. INTRODUCTIONAnaerobic digestion is a well-known method of utilizing chemical energy from organicwastes, both agricultural and municipal. Anaerobic microbes break down organic material asa part of their metabolism, and certain species produce methane as a waste product. Methaneis a greenhouse gas of high regulatory concern with over 20 times the heat capturing capacityas carbon dioxide (EPA, 2011).  In a managed anaerobic system, the methane produced canbe collected and then burned as a fuel, reducing the total greenhouse gas production of asystem. Since digestion is dependent on microbial activity, the environment where thedigestion occurs is an important factor in the system’s effectiveness. Microbial life occurs inthree distinct temperature ranges: thermophilic (50-60°C), mesophilic (25-40°C), andpsychrophilic (<20°C). Commonly, anaerobic digesters operate in the mesophilic range. ThepH and manure nutrient composition also impact the microbial activity and digestion process.An unheated manure storage system can be converted to an ambient temperatureanaerobic digester (AD) with the addition of a cover and gas collection system (NRCS,2003). While this type of AD is relatively low-cost and less technical than other types ofADs, gas production is affected by uncontrolled effluent temperature variation. The storedmanure moves to an equilibrium temperature based on ambient and soil temperatures,radiation gains and losses, and heat generated during the digestion process.There have been some studies that have investigated the digestion process under coolconditions. An early study from the Netherlands found no biogas production in dairy effluentGS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 19or swine slurry below a temperature of 20°C in any of the studied digesters without additionof previously treated effluent or an inoculum of temperature adapted bacteria (Zeeman et al.1988). A Russian study in the late 1990’s focused on the use of anaerobic digestion in thetemperature range of 3 to 9°C. The purpose for their investigation was to determine ifpsychrophilic anaerobic digestion was a viable alternative for industrial wastewatertreatment. They used a two-stage lab-scale system and loaded it with a constant mixture ofvolatile fatty acids. Under the low temperature conditions they observed a removal rate ofover 90% of volatile material after an initial break in period, even when the temperaturedropped to a minimum of 3°C for a period of 8 days. In addition to reducing the operationaltemperature they attempted to decrease the hydraulic retention time to a minimum whilemaintaining effective removal of volatile matter (Lettinga et al. 1999). This shows thatdegradation of volatile matter to methane can occur at low temperatures, and can attain highconversion efficiencies. Martin (2008) monitored the performance of a covered lagoonutilizing separated dairy effluent in California. They found no variation in the amount of gasproduced by the system during the year of monitoring. The temperature of the effluent variedfrom 12.4°C (54.4°F) to 28.6°C (83.6°F) and differed from ambient temperature by 9.1°C(15.3°F) in January. As the gas production remained unchanged the temperature of thelagoon never left the optimal range for microbe growth even though the lagoon fell below20°C. The literature suggests psychrophilic anaerobic digestion has the potential to beeffective down to 3°C in an intensely controlled system. Furthermore, effective digestionwas shown to continue through a 16.2°C reduction while maintaining gas output. Also, itwas found that addition of adapted bacteria to the effluent acted to jump start digestion incold systems that would otherwise have not produced biogas. The monitored system is notcontrolled and will not be as effective as a tightly regulated system. However, the simplicityof the construction and maintenance could balance out the loss of performance. This paper shows preliminary results from a long term, continuous monitoring project ofa simple AD system in South Dakota. This temperature data provides baseline measurementsfor more specific investigations into the overall effectiveness and heat transfer basics ofsimple AD systems in cooler climates.MATERIALS AND METHODThe monitored site was a 1,100-head dairy operation in eastern South Dakota with a flushmanure removal system and a two-cell waste storage system. The flushed manure firstencountered a solid separation system. The liquid fraction flowed out into the covered celland the solid portion was used for bedding. The covered cell was connected in series with anopen cell that stores the treated liquid that flows from the covered cell. Some of the liquid inthe second cell was recycled back through the barn in the flush system. The cover was a synthetic material, weighted down with concrete tubes to push gasthrough a gas collection system around the perimeter of the covered cell. The gases producedin the anaerobic conditions of the covered cell were flared off in order to reduce the totalgreenhouse gas emissions of the system. A total of 12 polyvinyl chloride(PVC) sludgelineswere built into the covered cell, parallel to the east wall and along the bottom, approximately20 LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE...GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 2020 cm from the covered cell floor. The purpose of the sludgeline was to allow for agitationand then removal of any sludge accumulation in the covered cell. The sludglines offered apractical access point to inside the covered cell.Temperature data for the covered cell was collected by threading five temperatureloggers (Model UA-001-08, Onset Computer Corp., Bourne, MA) into the sludgelines withcross-linked polyethylene (PEX) tubing. Three loggers were placed at the full depth of thecovered cell in sludgelines 3, 7, and 10. Two loggers were placed at approximately half thedepth of the covered cell in sludgelines 3 and 10 (Figure 1). The tube and loggers were left inthe sludgelines continuously except during monthly data retrieval, from 9/24/2010 to5/17/2011. Temperature measurements were recorded every 15 minutes.Figure 1. Location of the float (A) and weir (B) in the open cell (left), and the sludgelines(C) and temperature loggers (red circles, D) in the covered cell (right).Temperature data for the open cell was collected by placing a float in the center of thecell. The float was made of capped PVC pipe and wood. The dataloggers were fastened to a3-m chain at depths 0.6, 1.8, and 3.0 m from the surface. The float was anchored on theedges of the open cell. The open cell froze over in the winter so the sample rate was set to 1hour to allow for deployment without retrieval from 11/19/2010 to 4/19/2011. The ambient temperature 1 m above the south berm of the covered cell was recordedwith a logger in a solar shield from 11/19/2010 to 5/17/2011. Prior to 11/19/2010 hourlymean temperature data from Brookings, SD, was used (weatherunderground.com).The temperature accuracy of the dataloggers was assessed in ice water upon eachdeployment. The observed logger accuracy was within +/- 0.5°C.Manure samples were taken every two months starting in December to measure manurecomposition before and after treatment in the covered cell, as well as on recirculation into thebarn (after the open cell). The sample dates were 12/15/2010, 2/8/2011, and 4/19/2011.Effluent was collected prior to treatment just after the solid separation process. Effluent wascollected after treatment at the weir that controls flow from the covered to the open cell.Recirculation liquid was collected at the point where it re-entered the barn. Analyses(density, total nitrogen, phosphorus, potassium, ammonium nitrogen, pH, and moisture) werecompleted by Olson Agricultural Analytical Services Laboratory using standard practices.LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE... 21GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 21The volatile solids were determined by the Water and Environment Engineering ResearchCenter using standard methods. RESULTS AND DISCUSSIONTemperature in the covered cell in September was around 18°C, with the warmesttemperature being 18.6°C on the bottom of sludgeline 10 and the coolest being 17.8°C on theside of sludgeline 10. The temperature steadily declined to a minimum of between 5.5 and6.5°C throughout the covered cell. The early fall manure temperature of 18°C was coolerthan expected and appeared to already be on the decline. The effluent temperature trend inthe covered cell lagged the ambient temperature trend by approximately 4 weeks. Thetemperature trends were defined as periods when the temperature increased, decreased, orstayed the same over a period of time. Figure 2 shows the data collected from bothdataloggers in sludgeline 3 as well as the recorded ambient temperature. The temperature insludgeline 3 stayed essentially constant from 12/17/2010 to 3/25/2011. After 3/25/2011, themanure temperature rose at a gradual rate to a local maximum of 9.9°C for the bottom and9.6°C for the side loggers. The observed equilibrium temperature reached during the winterwas 6-7°C which constitutes psychrophilic conditions. Figure 2. Measured temperature at the side and bottom of sludgeline 3 and ambienttemperature.22 LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE...GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 22Temperature in the open cell in November was around 5°C at the 0.6-m (2’) depth andaround 8°C at the bottom. The 1.8-m (6 ft) and 3-m (10 ft) dataloggers both started on thebottom of the cell as it was recently pumped out in November. As the depth increased theloggers separated and a temperature profile developed as can be seen in figure 3. Theresponse to ambient temperature change was negatively correlated to depth, or the deeper thelogger the slower the response to the temperature change. That is most noticeable in midApril when the measured temperature of the 0.6-m (2 ft) datalogger spikes upward in responseto higher ambient temperature. The open cell was pumped out again starting on 4/18/2011.Figure 3. Manure temperatures in the open cell at 0.6 m (2’), 1.8 m (6’) and 3 m (10’) depthsfrom the surface.The data for three month-long periods were averaged by hour (Figures 4, 5, and 6).During October of 2010, there is an increase in effluent temperature between noon and16:00. The average change is small, around 0.15°C, which is less than the accuracy of thesensors, but it is unlikely that the observed increase in temperature at these hours would bedue to a consistent error in all of the sensors for the duration of deployment. Figure 5 showsthe average temperature over the January 2011 period. The temperature remained constantthrough this period. Figure 6 shows the data from April-May of 2011. Emerging temperaturechanges are evident in the morning from 8:00 to noon in all locations. Interestingly, thechanges in the spring month (Figure 6) are opposite to what was observed in the fall (Figure4), and the logger locations of the maximum and minimum temperatures are exactly oppositebetween fall and spring.LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE... 23GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 23Figure 4. Hourly averages over the 9-24 to 11-4 deployment period.Figure 5. Hourly averages over the 1-12 to 2-8 deployment period.Figure 6. Hourly averages over the 4-19 to 5-17 deployment period.24 LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE...GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 24Based on these measurements, we recommend a temperature sampling frequency of 1hour to allow for longer deployment durations as the dataloggers are robust enough to handlethe environment, as was seen in the open cell. Also, hourly sampling still allows for dailytrends to be examined. The recommended location of sampling is multiple depth profiles inthe covered manure if possible. If the emergency vents through the cover are located in thefull depth of the covered cell, this provides an ideal sampling location for measuring thetemperature profile. If temperature profiles through the cover are not an option, sampling inthe sludglines works well. It is recommended for future projects to add another samplinglocation in the sludgeline at a shallower depth so that more of a profile could be seen. Also, itwould be interesting to monitor the temperature of the effluent flowing from the closed to theopen cell at the weir.Manure composition results are shown in Table 1. The composition of the effluent ateach stage is variable, but does not change appreciably. The solids composition decreases thefurther through the system the effluent goes, and likewise the density increases towards 1g/mL, the density of water. The pH of the effluent in all stages was observed highest from theFebruary sampling; this corresponds to a higher ammonia concentration. Ammonia is a baseand is less volatile under cool conditions so higher concentrations will lead to higher pHmeasurements. The manure samples take a snapshot of the effluent compositions at each ofthe locations. The design hydraulic retention time of the covered cell was 60 days; the totaltime it took for effluent to be recycled back to the barn in the flush system is not known.Also, only a fraction of the effluent was used as flush water, but it is assumed that therecirculation effluent is representative of the open cell composition.Table 1 shows that volatile solid composition changed through treatment in the coveredcell. Volatile solids are the feed material for the microbial population, and are converted tomethane. Thus, volatile solid destruction correlates to the amount of methane produced andis a common method of determining digestion efficiency. On 12/15/2010 the volatile solidswere reduced by 50% through the covered cell. The overflow volatile soild compositionincreased markedly on the following two sample dates. There was an observed 33.5%reduction on 2/8/2011 and an observed 5.6% increase in volatile solids on 4/19/2011. Thevolatile soilds in the separated effluent on 4/19/2011 were much lower than the previoussamples. The sample was taken at a different time of day and likely corresponded with theflushing of washwater used to clean the parlor after the morning milking. Washwater woulddilute the effluent which would lower the concentration of observed volatile solids. It isassumed that the volatile solid loading into the covered cell would be relatively constant inthe 0.019 to 0.020 g/ml (0.16 to 0.17 lbs/gal) range based on constant diet nutrientcomposition, homogeneous cattle genetics, and the first two measurements.  LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE... 25GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 25Table 1. Manure composition for each sample point and each date.SUMMARYData gathered from the monitored site represents baseline data on the seasonal temperaturecharacteristics of a simple anaerobic digester in a climate with harsh winter conditions andextended cold periods. The data show that winter equilibrium temperatures in the coveredcell are adequate for digestion processes to occur, although at a reduced rate from the warmermonths. An important finding was that the manure temperature stabilized for almost 16weeks at around 6°C over the winter. Additionally, the hourly averages of manuretemperature shows that heat addition in the covered cell follows a cycle that appears toreverse from fall to spring. Future work could include investigation into the effect of thetemperature lag of the manure storage system with changes in ambient conditions and waysto reduce or lengthen it. ACKNOWLEDGEMENTSThe authors acknowledge the help and assistance of the dairy owner; Environmental CapitolManagement, LLC; the Griffith Undergraduate Research Program and Scholarship; ScottCortus; Corey Lanoue; and the Ag Engineering Department.26 LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE...GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 26REFERENCESEPA. 2011. Methane. United State Environmental Protection Agency.http://www.epa.gov/methane. Accessed May 24, 2011.NRCS. 2003. Natural Resource Conservation Standard, Conservation Practice Standard:Anaerobic temperature – Ambient temperature. Code No 365. Natural ResourceConservation Service. http://efotg.sc.egov.usda.gov//references/public/ID/365.pdf.Accessed May 24, 2011.Lettinga, G., S. Rebac, S. Parshina, A. Nozhevnikova, J.B. Vanlier, A.J.M. Stams. 1999.High-rate anaerobic treatment of wastewater at low temperatures. Applied and Env.Microbiology 65(4): 1696-1702Martin, J.H. 2008. An evaluation of a covered anaerobic lagoon for flushed dairy cattlemanure stabilization and biogas production. EPA Contract No. GS-10F-0036KZeeman, G., K. Sutter, T. Vens, M. Koster, A. Wellinger. 1988. Psychrophilic digestion ofdairy cattle and pig manure: Start-up procedures of batch, fed-batch and CSTR-typedigesters. Biological Wastes 26(1): 15-31LONG TERM, CONTINUOUS TEMPERATURE MONITORING OF A SIMPLE... 27GS019 JUR11_GS  JUR text  1/19/12  1:22 PM  Page 27

Long Term, Continuous Temperature Monitoring of a Simple Anaerobic Digester and Open Manure Storage Pond in Eastern South Dakota

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Long Term, Continuous Temperature Monitoring of a Simple Anaerobic Digester and Open Manure Storage Pond in Eastern South Dakota

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