Progress 09/01/16 to 09/30/20
Outputs
Target Audience:Targeted audiences of the proposed work include environmental research community, environmental/agricultural consultants, nutrient management planning specialists, personnel involved in manure/biosolids land application program, agricultural producers, and regulatory agencies. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project was primarily executed by graduate students in Biological Systems Engineering. The students had opportunities to develop independent research capabilities, design/conduct/analyze appropriate tests, gain critical analytical abilities, and improve both oral and written communication skills (via technical presentations and manuscript publications as a senior author). How have the results been disseminated to communities of interest?Results were disseminated through technical conference presentations, invited research presentations, and manuscripts submitted to peer-reviewed archival journals. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
To develop effective valorization strategies for dairy manure, pretreatment of lignocelluloses and anaerobic digestion were investigated. Compositional and structural property changes in dairy manure biomass during pretreatments and anaerobic digestion were evaluated. Analyses of fiber materials and degradation byproducts were used to compare pretreatments and determine solubilization of lignocelluloses. Batch biochemical methane potential (BMP) tests were conducted to evaluate anaerobic digestibility and methanogenesis of pretreated dairy manure biomass. Changes in phosphorus (P) speciation were also quantified to investigate P solubilization to facilitate precipitative recovery of mineral struvite. Raw dairy manure and anaerobic digestate collected from the Dane County Community Digester were used as the substrate and inoculum, respectively. Substrates were subjected to four different pretreatment methods: acid, alkaline, sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL), and alkaline hydrogen peroxide (AHP). Each pretreatment method was tested for two chemical dosages. With moderate chemical dosage, alkaline pretreatment showed enhancements in solubilization of fiber materials and carbohydrates. Effective pretreatments allowed reduction of cellulose and hemicellulose fractions and an increase in soluble sugars, suggesting solubilization of carbohydrates within the manure fiber matrix. By reducing recalcitrance of the fiber materials in the lignocellulosic biomass, anaerobic digestibility was improved resulting in greater biogas production. With moderate pretreatment, the SPORL treatment resulted in the greatest CH4 yield with 353 mL/g-VS followed by alkaline, acid, and AHP treatments with 311, 264, and 261 mL/g-VS, respectively. In comparison, raw dairy manure with no pretreatment resulted in a CH4 yield only 166 mL/g-VS. With severe pretreatment (high chemical dosage), more fiber materials and carbohydrates were solubilized. Pretreatments with greater conversion rates of fiber materials into soluble carbohydrates consequently produced more biogas and CH4. The greatest enhancement in biogas yield was observed with alkaline pretreatment producing a CH4 yield of 356 mL/g-VS. Pretreatments allowed more than a two-fold increase in CH4 yield (relative to untreated dairy manure). However, with acid pretreatment, there was an early termination in biogas production, resulting in lower yield than the untreated dairy manure. Pretreatments not only solubilize fiber materials into carbohydrates, but severe pretreatments can also further degrade soluble sugars to produce various lignocellulose-derived byproducts. Furan compounds were detected in some pretreated dairy manure biomass. The highest concentration of furans (1165 mg/L) was observed with dairy manure pretreated with acid (high dosage). To investigate the inhibitory effects of furan byproducts on methanogenesis, batch BMP tests were conducted where furfural and hydroxymethylfurfural (HMF) were each added at various loadings and biogas productions were observed. Four different loadings were tested for each compound: 500, 1000, 1500, and 2000 mg/L. Furfural addition showed inhibition in biogas generation at 1,000 mg/L and higher, while inhibition due to HMF was witnessed at 2,000 mg/L. At 1,500 mg/L of HMF, there was an initial lag phase with decreased biogas production, but the system showed acclimation with the cumulative biogas production reaching level similar to those in samples unaffected by HMF addition. Results indicate that early termination in biogas production was due to furfural accumulation. Concentrations of various P species were analyzed during pretreatment and anaerobic digestion. Effect of pretreatments on P solubilization was minimal and independent of fiber solubilization. During anaerobic digestion, however, there was a significant increase in P solubilization from the treatment groups. Test groups with pretreated biomass resulted in higher dissolved reactive P (DRP) levels with an average increase of 23%. The increase in DRP levels did not vary between treatments and was not in accordance with biogas production, but improved anaerobic digestibility also resulted in enhanced P solubilization. Conversion of organic P into more reactive inorganic orthophosphates could facilitate P recovery from anaerobic digestate as inorganic P precipitates (struvite). Although further research on optimizing pretreatment conditions is necessary to fully utilize the lignocelluloses while minimizing any inhibitory effect from degradation byproducts, our results suggest that alkaline pretreatment can effectively solubilize fiber materials from dairy manure biomass and increase CH4 production. Based on the batch experiments, pretreatments allowed more than a two-fold increase in CH4 yield. Anaerobic digestion process also facilitated P solubilization (conversion of particulate P into orthophosphates), suggesting that coupling anaerobic digestion and struvite recovery may present an integrated solution for a sustainable dairy manure management strategy. To determine the feasibility of implementing pretreatment technologies in full-scale dairy farms, a comprehensive techno-economic evaluation is necessary to determine tradeoffs between increased biogas production and the costs associated with the incorporation of various pretreatment options. By accounting for extra capital and operational costs involved in each pretreatment technology, a techno-economic analysis would allow evaluation of the potential benefits of each pretreatment technology.
Publications
- Type:
Journal Articles
Status:
Other
Year Published:
2021
Citation:
Kim, J.R. and K.G. Karthikeyan. 2021. Solubilization of Lignocellulosic Biomass Using Pretreatments for Enhanced Methane Production During Anaerobic Digestion of Manure. ACS ES&T Engineering (accepted, pending revisions)
- Type:
Conference Papers and Presentations
Status:
Other
Year Published:
2020
Citation:
Kim, J.R., and K.G. Karthikeyan. Assessment of pretreatments for enhanced methane production during dairy manure anaerobic digestion. Accepted for poster presentation at the 42nd Symposium on Biomaterials, Fuels and Chemicals during April 26-29, 2020 in New Orleans, LA. (Note: The symposium was canceled due to the COVID-19 pandemic)
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:Targeted audiences of the proposed work include environmental research community, environmental/agricultural consultants, nutrient management planning specialists, personnel involved in manure/biosolids land application program, agricultural producers, and regulatory agencies. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project is being primarily executed by a Ph.D.-level graduate student (in Biological Systems Engineering), Mr. Joonrae Kim. How have the results been disseminated to communities of interest?Two technical conference presentations, 1 invited presentation, and submission of 2 manuscripts to peer-reviewed archival journals will be accomplished in 2020 to disseminate results to targeted audiences. What do you plan to do during the next reporting period to accomplish the goals?We will continue all activities as originally proposed and approved.
Impacts
What was accomplished under these goals?
One of the primary challenges for efficient and economic utilization of lignocellulosic biomass is to overcome the natural recalcitrance of cellulose to enzymatic hydrolysis caused by its association with lignin and hemicelluloses. Pretreatments can facilitate enzymatic hydrolysis by disrupting the lignin structure resulting in increased biomethane yields. While biochemical methane potential (BMP) tests are commonly used to evaluate anaerobic degradability, quantitative analysis of sugars can be alternatively used to evaluate the enzymatic hydrolysis process. We evaluated carbohydrate analysis using anthrone for its ability to serve as an efficient proxy to facilitate quick comparison of various pretreatment options. Experimental results showed an increase in carbohydrate concentration in pretreated manure samples (compared to untreated samples). However, severe pretreatment conditions may degrade carbohydrates into furan compounds, which may interfere with the anthrone analysis causing an overestimation of total carbohydrates. To validate the anthrone method and for direct quantification of fermentable sugars, high-performance liquid chromatography (HPLC) analysis is being used to analyze sugar and byproduct contents in dairy manure. Preliminary experiments using raw dairy manure and digestate (after anaerobic treatment) revealed the presence of various interfering compounds suggesting the necessity to use sample extraction (e.g., soxhlet method) prior to HPLC analysis. We are developing a HPLC-based method suitable for direct quantification of individual sugars (i.e., arabinose, cellobiose, galactose, glucose, mannose, xylose) and furan compounds (i.e., furfural, HMF) in dairy manure samples. BMP tests for four different pretreatment methods (i.e., acid, alkaline, sulfite pre-treament to overcome recalcitrance of lignocellulose [SPORL], alkaline hydrogen peroxide [AHP]) are being conducted. Serum bottles with dairy manure substrate and digestate inoculum are incubated at mesophilic temperature (i.e., 35°C) for 27 days during which the generated biogas is collected and analyzed. Most cumulative biogas production resulted from the SPORL pretreatment with 3,780 mL, followed by alkaline (3,518 mL), AHP (3,022 mL), and acid (2,786 mL) pretreatments. The relatively low biogas yield from acid pretreatment could be explained by the low acid soluble lignin (ASL) fraction in raw dairy manure. Lignin analysis of raw dairy manure showed that most of the lignin was acid insoluble (~20.9%) and only a small fraction was acid soluble (~0.73%). Understanding compositional and structural changes to manure components during pretreatment is important to elucidate underlying processes associated with each pretreatment method. Such analyses include elemental composition, carbohydrate and byproduct (i.e., furans, phenolics) concentrations, fiber (i.e., acid detergent fiber, neutral detergent fiber) and lignin (i.e., acid soluble, acid insoluble) compositions. Comprehensive analysis of compositional changes of dairy manure, before and after each pretreatment, will be further examined to assess pretreatment methods and anaerobic digestibility.
Publications
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:Targeted audiences of the proposed work include environmental research community, environmental/agricultural consultants, nutrient management planning specialists, personnel involved in manure/biosolids land application program, agricultural producers, and regulatory agencies. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project is being primarily executed by a Ph.D.-level graduate student (in Biological Systems Engineering), Mr. Joonrae Kim. How have the results been disseminated to communities of interest?One technical conference presentation and submission of one manuscript to peer-reviewed archival journals is planned for 2019. What do you plan to do during the next reporting period to accomplish the goals?We will continue all activities as originally proposed and approved.
Impacts
What was accomplished under these goals?
Activities relevant for this project period include: (a) evaluation of biological and thermochemical pretreatment methods to enhance biogas yield and phosphorus (P) solubilization during anaerobic digestion of dairy manure, and (b) assessment of the impact of substrate-to-inoculum (S/I) ratio on cumulative biogas production. Biochemical methane potential (BMP) tests were performed to compare the effects of different pretreatment methods (i.e., biological pretreatment with enzyme supplementation, thermochemical pretreatment). Raw dairy manure and anaerobically digested solids were collected from a local anaerobic dairy manure digester for use as substrate and seeding inoculum, respectively. Commercially available enzyme cocktail product was used as the biological additive, with the enzymes including bacterial amylase, fungal amylase, protease, and cellulase. Thermochemical pretreatment involved autoclaving or microwave digestion with acid (HCl) or base (NaOH) addition. Autoclave was set at 136 deg C for 25 minutes and the microwave was set at 500 W for 25 minutes. HCl and NaOH loadings of 0.185% and 0.35 g/g-dry matter were used, respectively. In each serum bottle, 50 mL of the pretreated dairy manure substrate and 450 mL of the digestate inoculum were added to make a total volume of 500 mL. Prepared bottles were purged with N2 gas (anaerobic system) and subsequently incubated under mesophilic condition (i.e., 35°C). All treatments were tested in duplicates and the batch experiment lasted for 70 days. Biogas production and composition (i.e., methane, carbon dioxide, nitrogen gas) were periodically measured during this experimental period using gas chromatography (Model 8610C, SRI Instruments, USA) equipped with a thermal conductivity detector (TCD). Enzyme supplementation enhanced biogas production (compared to control manure with no pretreatment) while the opposite effect was observed with acid addition. About 4893 mL of cumulative biogas production was obtained with enzyme addition compared to 3835 and 3502 mL, respectively for control system and microwave (+ acid) treatment. Direct relationship between cumulative biogas production and volatile solids reduction was obtained. Treatments involving NaOH addition exhibited an initial lag effect with low biogas production rates attributable to inhibitory effects of increasing pH on methanogenesis. Distribution of P between dissolved and particulate-bound forms was determined. All pretreatment methods tested showed an increase in P solubilization (by as much as 34%) from dairy manure (compared to control), which presents greater opportunities for recovery of value-added products after anaerobic digestion. Additional BMP tests are being conducted to optimize the substrate-to-inoculum (S/I) ratio for cumulative biogas production. While higher biodegradability and methane potential are usually obtained at lower S/I ratios for most organic substrates, dairy manure may withstand higher S/I ratios due to their relatively high alkalinity. Four S/I ratios were tested - 1:9, 1:5, 1:1, and 2:1 by volume, or 0.17, 0.30, 1.51, and 3.02 by g-VS, respectively. The BMP setup was used with each bottle consisting of raw dairy manure substrate and anaerobically digested solids as the inoculum. The test was performed in triplicates and lasted for 40 days. Cumulative methane production was highest in the order of 1:5, 2:1, 1:1, and 1:9 S/I ratio with 135.61, 119.25, 96.07, and 10.92 mL-CH4/g-VSManure, respectively. Use of higher S/I ratio during anaerobic digestion may enhance both biodegradability and treatment efficiency. Further research and experiments will be conducted for a more direct comparison between various pretreatment methods. Calorimetric test using anthrone would be utilized to estimate monosaccharide contents in pretreated dairy manure substrate. Degradation of cellulosic biomass (i.e., hydrolysis) will be determined by comparing monosaccharide contents between untreated and pretreated substrates. With such less time-consuming techniques, several other pretreatment methods (e.g., co-digestion with other organic carbon sources) and/or use of biological additives (e.g., ruminal fluids) will be evaluated for their ability to enhance anaerobic digestion of dairy manure.
Publications
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Progress 10/01/16 to 09/30/17
Outputs
Target Audience:Targeted audiences of the proposed work include environmental research community, environmental/agricultural consultants, nutrient management planning specialists, personnel involved in manure/biosolids land application program, agricultural producers, and regulatory agencies. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project is being primarily executed by a Ph.D.-level graduate student (in Biological Systems Engineering), Mr. Joonrae Kim. How have the results been disseminated to communities of interest?We will start disseminating project results through presentations at appropriate technical conferences and publications in peer-reviewed journals. What do you plan to do during the next reporting period to accomplish the goals?We will continue all activities as originally proposed and approved.
Impacts
What was accomplished under these goals?
Activities relevant for this project period include: (a) identification of local anaerobic digesters for collecting substrate and inoculum samples, (b) characterization of separated dairy manure solid substrate and seeding inoculum, and (c) evaluation of the potential of enzyme supplementation to enhance anaerobic digestion using batch biochemical methane potential (BMP) tests. Raw dairy manure and anaerobically digested solids were collected from a local anaerobic dairy manure digester for use as substrate and seeding inoculum, respectively. This community digester was first commissioned in 2010 and treats manure generated from three adjacent dairy farms. Approximately 80,000 gallons of manure is treated daily with a hydraulic retention time of 20-30 days. Collected samples were characterized for the following chemical characteristics: total solids content, volatile solids content, pH, chemical oxygen demand, total Kjeldahl N (TKN), total P (TP). To determine the optimal operating conditions for anaerobic manure digestion with enzymatic supplementation, a series of BMP test is being performed with three different commercially available enzyme cocktail products. All three products have optimal pH range of 6.5-8.5, comprise bacterial species known for their unique abilities to break down carbohydrates, proteins, fats, oils and grease so that they are capable of enhancing hydrolysis of cellulosic biomass. These cocktail products differ in composition and the microbial species from which the enzymes were obtained. While all three products possess bacterial species Bacillus subtilis and Bacillus licheniformis, one product additionally contains Bacillus amyloliquefaciens. The two products without Bacillus amyloliquefaciens differ by the presence/absence of chemical reagents for odor control. Exact compositional details of the three cocktail products could not be obtained from the commercial supplier due to proprietary reasons. BMP test allows assessment of potential anaerobic biodegradability of a substrate by performing tests in a controlled laboratory environment. Using the BMP tests, a variety of experimental conditions will be compared to identify optimal condition (for enhancement of biodegradability and nutrient solubilization) prior to constructing a pilot-scale continuous reactor. BMP tests are being performed in 250-mL serum bottles in which 0.5 g-VS of raw solid dairy manure is used as substrate (i.e., organic load). Four test groups are being evaluated in triplicate (i.e., 12 batch fermenters). While the control group has no enzyme addition, the remaining three test groups correspond to the three different enzyme cocktail products acquired. Using the inoculum the total volume in each serum bottle is adjusted to 100 mL. Anaerobic condition in each prepared bottle is achieved by purging with nitrogen gas prior to sealing with air-tight rubber seal and aluminum cap. Sealed BMP test bottles are incubated under mesophilic condition (i.e., 35°C) and periodic monitoring of biogas production and composition (i.e., methane, carbon dioxide, and nitrogen gas) performed using gas chromatography (GC). The GC unit is equipped with a thermal conductivity detector and uses helium as the carrier gas (Model 8610C, SRI Instruments, USA). Throughout the 90 days of experimental period, all four test groups showed signs of effective organic matter degradation and biogas production. A sigmoidal function can be used to describe the relationship between methane production and incubation time. As soon as the microbial communities adjust to the environment, rapid organic C degradation and biogas production can be observed until the available substrate is slowly depleted. Analyzed methane content was relatively consistent at 50% throughout indicating stable anaerobic digestion process. Only one out of three test groups with enzymatic supplementation showed enhanced biogas production compared to the control group. The cumulative methane yields during the experimental period were 93.7, 92.8, 100.7, and 88.8 mL-CH4/g-VS for the control group and three test groups with enzyme supplementation, respectively. Whereas the enzyme cocktail product with three bacterial species showed similar methane yield (99.1%) compared to the control group, the product with two bacterial species and odor control agents resulted in the lowest yield (94.7% of the control group yield) and the product without odor control agents produced the highest methane yield (107.5%). At the end of incubation period, each BMP test bottle will be opened and the contents will be tested for additional parameters: volatile solids removal, TKN, TP, total dissolved P, water extractable P, and dissolved reactive P. Additional BMP tests are currently being designed to be performed with different operating conditions including alternative pretreatment methods such as thermal pretreatment (autoclave) or alkaline pretreatment (NaOH). Optimal operating conditions with enhanced organic C biodegradation and nutrient solubilization will be determined after which pilot-scale anaerobic digesters (20-L PVC vessels) will be constructed for operation as continuous reactors. We plan to design and construct continuous stirred-tank anaerotic reactors to operate under mesophilic conditions. The reactors will have continuous flow of organic C substrate with generated biogas captured using tedlar bags. The reactors will be constructed to facilitate control of organic loading rates and also periodic samplings to maintain operational stability and evaluation of various process/reaction parameters.
Publications
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Progress 09/01/16 to 09/30/16
Outputs
Target Audience:Targeted audiences of the proposed work include environmental research community, environmental/agricultural consultants, nutrient management planning specialists, personnel involved in manure/biosolids land application program, agricultural producers, and regulatory agencies. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project will be primarily executed by a Ph.D.-level graduate student (in Biological Systems Engineering), Mr. Joonrae Kim. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?We will continue all activities as originally proposed and approved.
Impacts
What was accomplished under these goals?
This project commenced only in Sep. 2016 and relevant activities for 1 month of reporting period (9/1/16 to 9/30/16) include: (a) Recruitment of 1 PhD-level graduate student (Mr. Joonrae Roger Kim) to work on this project, (b) Development of experimental design for the batch fermenters (i.e., biochemical methane potential (BMP) test). Apparatus necessary for the research project are being reviewed and the required equipment/chemical reagents are being purchased. We are in the process of collecting and preparing separated dairy manure solid substrate and seeding inoculum. Chemical properties of both substrate and inoculum will be examined after which the optimal operating conditions for anaerobic manure digestion will be determined using BMP tests. Pilot scale anaerobic digesters (20-L PVC vessels) will be constructed in spring 2017. Comprehensive reactor design and operational planning will be performed.
Publications
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