. The ideal practice for determining gas emission rates from concentrated animal feeding operatio... more . The ideal practice for determining gas emission rates from concentrated animal feeding operations (CAFOs) is continuous measurement throughout the year to capture diurnal and seasonal variations. However, data that meet this criterion are scarce because this approach is costly and technically challenging. A practical approach with reduced sampling time and frequency without compromising integrity is thus necessary. In this study, we examined five reduced sampling protocols for determining emission rates from naturally ventilated dairy barns: (1) six sampling events, during even months, each event running continuously for 24 h (144 hourly data points); (2) six sampling events, during odd months, each event running continuously for 24 h (144 hourly data points); (3) six sampling events, during even months, each event running continuously for 7 d (1,008 hourly data points); (4) six sampling events, during odd months, each event running continuously for 7 d (1,008 hourly data points); and (5) 12 sampling events, one event every month, each event running continuously for 24 h (288 hourly data points). These five reduced sampling protocols were evaluated against baseline emission rates obtained from a protocol consisting of 12 sampling events, one event every month, each event running continuously for 7 d (2,016 hourly data points). The average baseline emission rates for carbon dioxide (CO2), ammonia (NH3), and hydrogen sulfide (H2S) ranged from 7.0 to 10.8 g d-1 AU-1, from 16.9 to 24.3 g d-1 AU-1, and from 0.40 to 0.63 g d-1 AU-1, respectively. Emission rates for CO2 and NH3 obtained from all five reduced sampling protocols had relative biases of less than 20% from the respective baseline emission rates. This implied that even the most reduced sampling protocol (six sampling events per year, each event running continuously for 24 h) would be adequate for determining CO2 and NH3 emission rates. However, for H2S, relative biases of the reduced sampling protocols ranged from 2% to 45%, with a 50% chance of emission rates falling outside ±20% of the baseline emission rates. These protocols, however, are only applicable for quantifying emission rates from barns with steady-state live animal mass. Keywords: Air quality, Emission rates, Air sampling protocol, CAFO, Emission inventories.
Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the ... more Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the retention of adequate active biomass, in successive-cycles, is always a challenge. This research investigated the efficacy of using a cationic polyacrylamide (PAM) flocculant for enhanced sludge retention in an ASBR treating flushed dairy manure, operated under psychrophilic conditions. Three PAM doses (10, 25, and 50 mg [PAM] l−1) were tested in duplicate reactors. At 6 d hydraulic retention time (HRT) and dosing of the feed-manure, steady state specific biogas yield for the 50 mg [PAM] l−1 treatment was 491 ± 7 ml g−1 [TCOD] (56% greater than control). At 4 d HRT the 50 mg [PAM] l−1 dose resulted in 465 ± 8 ml g−1 [TCOD] (20% higher than the control) at steady state conditions. The ratio of total volatile fatty acid to alkalinity was 0.29 ± 0.08 during the 6 d HRT and 0.14 ± 0.02 during the 4 d HRT, which were both below the trigger point for digester souring. This study shows that the use of PAM for high sludge retention in ASBR is a viable approach for, not only enhancing biogas yield, but also for improved and high-rate treatment of flushed dairy manure under psychrophilic conditions.
Abstract The dynamics of microbial communities during anaerobic digestion at different states of ... more Abstract The dynamics of microbial communities during anaerobic digestion at different states of acclimation and inhibitions is key to diagnosing ailments of this process. Previous studies focused primarily on concentrations thresholds for inhibition and adaptation. This study investigated the dynamics of methane (CH4) producing communities subjected to ammonia and salinity stresses during batch anaerobic digestion, of dairy wastewater, in both acclimated and unacclimated conditions. Experimental data was fitted into the ‘Modified Gompertz Model’ and resulting lag phase values related to stress conditions. R2-values ranged between 0.95 and 1.00 suggesting a nearly perfect fit of the model to the observed CH4 production. Irrespective of acclimation conditions, digesters under ammonia stresses produced less CH4 compared to those subjected to salinity stresses. Salinity-acclimated digesters performed similar to salinity-free digesters below 12 g L−1 salinity level. Petrimonas and Clostridium XI were the most dominant (50–61%) bacterial genera in salinity-acclimated digesters, whereas Petrimonas, Clostridium XI, Alkaliflexus, Sedimentibacter, and Clostridium III were the most abundant (69–82%) bacterial genera in salinity-unacclimated digesters. In ammonia-acclimated digesters, Petrimonas, Clostridium XI, and Alkaliflexus were the most dominant (55–68%) genera. Petrimonas, Clostridium XI, Alkaliflexus, Sedimentibacter, Clostridium III, Clostridium XIVa, were the most abundant (74–87%) bacterial genera in TAN-unacclimated digesters. Methanosarcina, Methanobrevibacter and Methanobacterium were most abundant archaea in both salinity (71–99%) and ammonia (87–98%) stressed digesters. The principal component analysis demonstrated bacteria clustering in the acclimated and the unacclimated reactors. No such clustering of archaea was evident in either acclimated or unacclimated reactors.
Abstract Solid-state anaerobic digestion is widely used in lieu of liquid-stage anaerobic digesti... more Abstract Solid-state anaerobic digestion is widely used in lieu of liquid-stage anaerobic digestion for treating biowastes due to the former's advantages. However, unsatisfactory process performance and low methane yields inhibit the development of solid-state anaerobic digestion for treating lignocellulosic material. Soil, with the potential of inter-species electron transfer, buffer capacity, and nutritional elements for microbial growth, was used to improve the anaerobic digestion efficiency. At the same time, simultaneous NaOH treatment was adopted to simplify the lignocellulose treatment process. Results include daily methane yield enhancement and improved methane content. The maximum methane yield (344 L/kg volatile solid) was obtained at 1% NaOH for the group with soil addition; pH was maintained in a suitable range (6.6–7.8). The difference in total methane yield between a solid-state digester with no NaOH but with soil addition and a digester with 1% NaOH without soil addition was not significant, which indicates that soil stimulated the potential methane yield and could be an alternative for simultaneous NaOH treatment. The cations contained in soil is verified to be the main reason to improve the anaerobic digestion efficiency. Therefore, the discovery found in this study can be the reference for various biowastes conversion via solid-state anaerobic digestion.
Failure of methane yield is common for anaerobic digestion (AD) of &q... more Failure of methane yield is common for anaerobic digestion (AD) of "weak-acid/acid" wastes alone. In order to verify the importance of pH of materials on the process performance and the methane yield, the "weak-base" wastes-poplar wastes (PW) were used as substrate of solid-state AD (SS-AD). The results show that PW could be used for efficient methane yield after NaOH treatment, the total methane yield was 81.1 L/kg volatile solids (VS). PW also could be used for anaerobic co-digestion with high-pH cattle slurry (CM). For the group with NaOH pretreatment, time used for reaching stable state was 2 days earlier than that of the group without NaOH pretreatment. The maximal methane yield of 98.2 L/kg VS was obtained on conditions of 1:1 of PW-to-CM (P/C) ratio and NaOH pretreatment, which was 21.1% (p < 0.05) higher than that of PW. The maximal reductions of total solids (TS), VS, cellulose and hemicellulose were 51.3%, 57.5%, 46.0% and 47.0%, respectively, which were associated with the maximal methane yield. The results indicate that PW could be alone used for efficient SS-AD for methane yield after NaOH treatment.
Engineering in Agriculture, Environment and Food, 2016
Abstract Ion mobility spectrometry (IMS) has been employed successfully to detect chemicals such ... more Abstract Ion mobility spectrometry (IMS) has been employed successfully to detect chemicals such as explosives, illicit drugs, chemical warfare agents, pharmaceutical chemicals, and environmental pollutants. However, applications of IMS in pre- and post-harvest agriculture production management has not been explored adequately. Characteristics such as high sensitivity, selectivity, analytical flexibility, field portability, and real-time monitoring abilities offer great potential of IMS applications in agriculture. In this paper, reviewed are the different types of IMS, their working principles, and agricultural applications. Some of the agricultural applications include; detection of contaminants affecting soil and plants, assessing plant stress, and monitoring postharvest agricultural produce quality and safety.
Engineering in Agriculture, Environment and Food, 2016
Abstract In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH... more Abstract In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH 3 ) emissions reduction and in retaining nitrogen (N) in fresh liquid swine manure (SM) was evaluated. The relationship between pH and NH 3 emission was also determined. Different doses of polymer (namely Treatment 1 = T1 = 0.8 L polymer/ton of manure, Treatment 2 = T2 = 1.6 L polymer/ton of manure, Treatment 3 = T3 = 2.4 L polymer/ton of manure, and Treatment 4 = T4 = 3.2 L polymer/ton of manure) were added to the SM and its effects were observed for 30 d. The tests results showed significant reduction in pH for T1, T2, T3 and T4 compared to control (C). For the short term (up to 3d) T2, T3, and T4 showed significantly lower NH 3 gas concentrations than C, however, for the long term (up to 10–20 d) only T4 continued to indicate significantly lower NH 3 gas concentrations. Although numeric observations were reported for other treatments (T1, T2 and T3), no significant differences in NH 3 gas concentrations were found. The NH 3 emissions reductions were calculated in the range of 81–92%, 31–88%, −39–61%, 6–41%, −106% to −6% for the treatment period of 1, 3, 10, 20 and 30 d, respectively. The addition of polymer resulted in no significant difference in total ammonia nitrogen (TAN) and NO 3 − –N concentration. However, the addition of polymer had a significant influence on total Kjehldahl nitrogen (TKN) and soluble chemical oxygen demand (SCOD) concentration. The NH 3 gas emissions strongly correlated with the manure pH (R 2 = 0.911–0.999).
There is a lack of literature reporting the methane potential of several livestock manures under ... more There is a lack of literature reporting the methane potential of several livestock manures under the same anaerobic digestion conditions (same inoculum, temperature, time, and size of the digester). To the best of our knowledge, no previous study has reported biochemical methane potential (BMP) predicting models developed and evaluated by solely using at least five different livestock manure tests results. The goal of this study was to evaluate the BMP of five different livestock manures (dairy manure (DM), horse manure (HM), goat manure (GM), chicken manure (CM) and swine manure (SM)) and to predict the BMP using different statistical models. Nutrients of the digested different manures were also monitored. The BMP tests were conducted under mesophilic temperatures with a manure loading factor of 3.5g volatile solids (VS)/L and a feed to inoculum ratio (F/I) of 0.5. Single variable and multiple variable regression models were developed using manure total carbohydrate (TC), crude pro...
The anaerobic co-digestion of Chinese cabbage waste silage (CCWS) and swine manure (SM) was carri... more The anaerobic co-digestion of Chinese cabbage waste silage (CCWS) and swine manure (SM) was carried out at mesophilic temperature (36-38oC) under batch mode. The mixtures ratios of SM and CCWS were 100:0, 75:25, 67:33, 33:67 and 0:100 (SM:CCWS) on a volatile solid (VS) basis at OLR of 16 gVS/L and F/M ratio of 1.6. After 40 days of digestion, biogas yield was calculated to be 425, 408, 410, 342 and 196 mL/gVS added for the SM:CCWS (100:0), SM:CCWS (75:25), SM:CCWS (67:33), SM:CCWS (33:67) and SM:CCWS (0:100), respectively. The result also showed that CCWS content in the feed can be used up to 67% (VS basis) without decreasing the methane yield per unit feedstock input (mL/g substrate added).
The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabb... more The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabbage waste silage (CCWS) with swine manure (SM). Batch and continuous experiments were carried out under mesophilic anaerobic conditions (36-38°C). The batch test evaluated the effect of CCWS co-digestion with SM (SM: CCWS=100:0; 25:75; 33:67; 0:100, % volatile solids (VS) basis). The continuous test evaluated the performance of a single stage completely stirred tank reactor with SM alone and with a mixture of SM and CCWS. Batch test results showed no significant difference in biogas yield up to 25-33% of CCWS; however, biogas yield was significantly decreased when CCWS contents in feed increased to 67% and 100%. When testing continuous digestion, the biogas yield at organic loading rate (OLR) of 2.0 g VSL⁻¹ d⁻¹ increased by 17% with a mixture of SM and CCWS (SM:CCWS=75:25) (423 mL g⁻¹ VS) than with SM alone (361 mL g⁻¹ VS). The continuous anaerobic digestion process (biogas production, pH, total volatile fatty acids (TVFA) and TVFA/total alkalinity ratios) was stable when co-digesting SM and CCWS (75:25) at OLR of 2.0 g VSL⁻¹ d⁻¹ and hydraulic retention time of 20 days under mesophilic conditions.
. The ideal practice for determining gas emission rates from concentrated animal feeding operatio... more . The ideal practice for determining gas emission rates from concentrated animal feeding operations (CAFOs) is continuous measurement throughout the year to capture diurnal and seasonal variations. However, data that meet this criterion are scarce because this approach is costly and technically challenging. A practical approach with reduced sampling time and frequency without compromising integrity is thus necessary. In this study, we examined five reduced sampling protocols for determining emission rates from naturally ventilated dairy barns: (1) six sampling events, during even months, each event running continuously for 24 h (144 hourly data points); (2) six sampling events, during odd months, each event running continuously for 24 h (144 hourly data points); (3) six sampling events, during even months, each event running continuously for 7 d (1,008 hourly data points); (4) six sampling events, during odd months, each event running continuously for 7 d (1,008 hourly data points); and (5) 12 sampling events, one event every month, each event running continuously for 24 h (288 hourly data points). These five reduced sampling protocols were evaluated against baseline emission rates obtained from a protocol consisting of 12 sampling events, one event every month, each event running continuously for 7 d (2,016 hourly data points). The average baseline emission rates for carbon dioxide (CO2), ammonia (NH3), and hydrogen sulfide (H2S) ranged from 7.0 to 10.8 g d-1 AU-1, from 16.9 to 24.3 g d-1 AU-1, and from 0.40 to 0.63 g d-1 AU-1, respectively. Emission rates for CO2 and NH3 obtained from all five reduced sampling protocols had relative biases of less than 20% from the respective baseline emission rates. This implied that even the most reduced sampling protocol (six sampling events per year, each event running continuously for 24 h) would be adequate for determining CO2 and NH3 emission rates. However, for H2S, relative biases of the reduced sampling protocols ranged from 2% to 45%, with a 50% chance of emission rates falling outside ±20% of the baseline emission rates. These protocols, however, are only applicable for quantifying emission rates from barns with steady-state live animal mass. Keywords: Air quality, Emission rates, Air sampling protocol, CAFO, Emission inventories.
Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the ... more Anaerobic sequencing batch reactors (ASBR) are preferred for treating dilute wastewaters but the retention of adequate active biomass, in successive-cycles, is always a challenge. This research investigated the efficacy of using a cationic polyacrylamide (PAM) flocculant for enhanced sludge retention in an ASBR treating flushed dairy manure, operated under psychrophilic conditions. Three PAM doses (10, 25, and 50 mg [PAM] l−1) were tested in duplicate reactors. At 6 d hydraulic retention time (HRT) and dosing of the feed-manure, steady state specific biogas yield for the 50 mg [PAM] l−1 treatment was 491 ± 7 ml g−1 [TCOD] (56% greater than control). At 4 d HRT the 50 mg [PAM] l−1 dose resulted in 465 ± 8 ml g−1 [TCOD] (20% higher than the control) at steady state conditions. The ratio of total volatile fatty acid to alkalinity was 0.29 ± 0.08 during the 6 d HRT and 0.14 ± 0.02 during the 4 d HRT, which were both below the trigger point for digester souring. This study shows that the use of PAM for high sludge retention in ASBR is a viable approach for, not only enhancing biogas yield, but also for improved and high-rate treatment of flushed dairy manure under psychrophilic conditions.
Abstract The dynamics of microbial communities during anaerobic digestion at different states of ... more Abstract The dynamics of microbial communities during anaerobic digestion at different states of acclimation and inhibitions is key to diagnosing ailments of this process. Previous studies focused primarily on concentrations thresholds for inhibition and adaptation. This study investigated the dynamics of methane (CH4) producing communities subjected to ammonia and salinity stresses during batch anaerobic digestion, of dairy wastewater, in both acclimated and unacclimated conditions. Experimental data was fitted into the ‘Modified Gompertz Model’ and resulting lag phase values related to stress conditions. R2-values ranged between 0.95 and 1.00 suggesting a nearly perfect fit of the model to the observed CH4 production. Irrespective of acclimation conditions, digesters under ammonia stresses produced less CH4 compared to those subjected to salinity stresses. Salinity-acclimated digesters performed similar to salinity-free digesters below 12 g L−1 salinity level. Petrimonas and Clostridium XI were the most dominant (50–61%) bacterial genera in salinity-acclimated digesters, whereas Petrimonas, Clostridium XI, Alkaliflexus, Sedimentibacter, and Clostridium III were the most abundant (69–82%) bacterial genera in salinity-unacclimated digesters. In ammonia-acclimated digesters, Petrimonas, Clostridium XI, and Alkaliflexus were the most dominant (55–68%) genera. Petrimonas, Clostridium XI, Alkaliflexus, Sedimentibacter, Clostridium III, Clostridium XIVa, were the most abundant (74–87%) bacterial genera in TAN-unacclimated digesters. Methanosarcina, Methanobrevibacter and Methanobacterium were most abundant archaea in both salinity (71–99%) and ammonia (87–98%) stressed digesters. The principal component analysis demonstrated bacteria clustering in the acclimated and the unacclimated reactors. No such clustering of archaea was evident in either acclimated or unacclimated reactors.
Abstract Solid-state anaerobic digestion is widely used in lieu of liquid-stage anaerobic digesti... more Abstract Solid-state anaerobic digestion is widely used in lieu of liquid-stage anaerobic digestion for treating biowastes due to the former's advantages. However, unsatisfactory process performance and low methane yields inhibit the development of solid-state anaerobic digestion for treating lignocellulosic material. Soil, with the potential of inter-species electron transfer, buffer capacity, and nutritional elements for microbial growth, was used to improve the anaerobic digestion efficiency. At the same time, simultaneous NaOH treatment was adopted to simplify the lignocellulose treatment process. Results include daily methane yield enhancement and improved methane content. The maximum methane yield (344 L/kg volatile solid) was obtained at 1% NaOH for the group with soil addition; pH was maintained in a suitable range (6.6–7.8). The difference in total methane yield between a solid-state digester with no NaOH but with soil addition and a digester with 1% NaOH without soil addition was not significant, which indicates that soil stimulated the potential methane yield and could be an alternative for simultaneous NaOH treatment. The cations contained in soil is verified to be the main reason to improve the anaerobic digestion efficiency. Therefore, the discovery found in this study can be the reference for various biowastes conversion via solid-state anaerobic digestion.
Failure of methane yield is common for anaerobic digestion (AD) of &q... more Failure of methane yield is common for anaerobic digestion (AD) of "weak-acid/acid" wastes alone. In order to verify the importance of pH of materials on the process performance and the methane yield, the "weak-base" wastes-poplar wastes (PW) were used as substrate of solid-state AD (SS-AD). The results show that PW could be used for efficient methane yield after NaOH treatment, the total methane yield was 81.1 L/kg volatile solids (VS). PW also could be used for anaerobic co-digestion with high-pH cattle slurry (CM). For the group with NaOH pretreatment, time used for reaching stable state was 2 days earlier than that of the group without NaOH pretreatment. The maximal methane yield of 98.2 L/kg VS was obtained on conditions of 1:1 of PW-to-CM (P/C) ratio and NaOH pretreatment, which was 21.1% (p < 0.05) higher than that of PW. The maximal reductions of total solids (TS), VS, cellulose and hemicellulose were 51.3%, 57.5%, 46.0% and 47.0%, respectively, which were associated with the maximal methane yield. The results indicate that PW could be alone used for efficient SS-AD for methane yield after NaOH treatment.
Engineering in Agriculture, Environment and Food, 2016
Abstract Ion mobility spectrometry (IMS) has been employed successfully to detect chemicals such ... more Abstract Ion mobility spectrometry (IMS) has been employed successfully to detect chemicals such as explosives, illicit drugs, chemical warfare agents, pharmaceutical chemicals, and environmental pollutants. However, applications of IMS in pre- and post-harvest agriculture production management has not been explored adequately. Characteristics such as high sensitivity, selectivity, analytical flexibility, field portability, and real-time monitoring abilities offer great potential of IMS applications in agriculture. In this paper, reviewed are the different types of IMS, their working principles, and agricultural applications. Some of the agricultural applications include; detection of contaminants affecting soil and plants, assessing plant stress, and monitoring postharvest agricultural produce quality and safety.
Engineering in Agriculture, Environment and Food, 2016
Abstract In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH... more Abstract In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH 3 ) emissions reduction and in retaining nitrogen (N) in fresh liquid swine manure (SM) was evaluated. The relationship between pH and NH 3 emission was also determined. Different doses of polymer (namely Treatment 1 = T1 = 0.8 L polymer/ton of manure, Treatment 2 = T2 = 1.6 L polymer/ton of manure, Treatment 3 = T3 = 2.4 L polymer/ton of manure, and Treatment 4 = T4 = 3.2 L polymer/ton of manure) were added to the SM and its effects were observed for 30 d. The tests results showed significant reduction in pH for T1, T2, T3 and T4 compared to control (C). For the short term (up to 3d) T2, T3, and T4 showed significantly lower NH 3 gas concentrations than C, however, for the long term (up to 10–20 d) only T4 continued to indicate significantly lower NH 3 gas concentrations. Although numeric observations were reported for other treatments (T1, T2 and T3), no significant differences in NH 3 gas concentrations were found. The NH 3 emissions reductions were calculated in the range of 81–92%, 31–88%, −39–61%, 6–41%, −106% to −6% for the treatment period of 1, 3, 10, 20 and 30 d, respectively. The addition of polymer resulted in no significant difference in total ammonia nitrogen (TAN) and NO 3 − –N concentration. However, the addition of polymer had a significant influence on total Kjehldahl nitrogen (TKN) and soluble chemical oxygen demand (SCOD) concentration. The NH 3 gas emissions strongly correlated with the manure pH (R 2 = 0.911–0.999).
There is a lack of literature reporting the methane potential of several livestock manures under ... more There is a lack of literature reporting the methane potential of several livestock manures under the same anaerobic digestion conditions (same inoculum, temperature, time, and size of the digester). To the best of our knowledge, no previous study has reported biochemical methane potential (BMP) predicting models developed and evaluated by solely using at least five different livestock manure tests results. The goal of this study was to evaluate the BMP of five different livestock manures (dairy manure (DM), horse manure (HM), goat manure (GM), chicken manure (CM) and swine manure (SM)) and to predict the BMP using different statistical models. Nutrients of the digested different manures were also monitored. The BMP tests were conducted under mesophilic temperatures with a manure loading factor of 3.5g volatile solids (VS)/L and a feed to inoculum ratio (F/I) of 0.5. Single variable and multiple variable regression models were developed using manure total carbohydrate (TC), crude pro...
The anaerobic co-digestion of Chinese cabbage waste silage (CCWS) and swine manure (SM) was carri... more The anaerobic co-digestion of Chinese cabbage waste silage (CCWS) and swine manure (SM) was carried out at mesophilic temperature (36-38oC) under batch mode. The mixtures ratios of SM and CCWS were 100:0, 75:25, 67:33, 33:67 and 0:100 (SM:CCWS) on a volatile solid (VS) basis at OLR of 16 gVS/L and F/M ratio of 1.6. After 40 days of digestion, biogas yield was calculated to be 425, 408, 410, 342 and 196 mL/gVS added for the SM:CCWS (100:0), SM:CCWS (75:25), SM:CCWS (67:33), SM:CCWS (33:67) and SM:CCWS (0:100), respectively. The result also showed that CCWS content in the feed can be used up to 67% (VS basis) without decreasing the methane yield per unit feedstock input (mL/g substrate added).
The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabb... more The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabbage waste silage (CCWS) with swine manure (SM). Batch and continuous experiments were carried out under mesophilic anaerobic conditions (36-38°C). The batch test evaluated the effect of CCWS co-digestion with SM (SM: CCWS=100:0; 25:75; 33:67; 0:100, % volatile solids (VS) basis). The continuous test evaluated the performance of a single stage completely stirred tank reactor with SM alone and with a mixture of SM and CCWS. Batch test results showed no significant difference in biogas yield up to 25-33% of CCWS; however, biogas yield was significantly decreased when CCWS contents in feed increased to 67% and 100%. When testing continuous digestion, the biogas yield at organic loading rate (OLR) of 2.0 g VSL⁻¹ d⁻¹ increased by 17% with a mixture of SM and CCWS (SM:CCWS=75:25) (423 mL g⁻¹ VS) than with SM alone (361 mL g⁻¹ VS). The continuous anaerobic digestion process (biogas production, pH, total volatile fatty acids (TVFA) and TVFA/total alkalinity ratios) was stable when co-digesting SM and CCWS (75:25) at OLR of 2.0 g VSL⁻¹ d⁻¹ and hydraulic retention time of 20 days under mesophilic conditions.
Precision application of manure in agricultural land requires information on its nutrients but th... more Precision application of manure in agricultural land requires information on its nutrients but the existing reliable nutrient estimation methods are unsuitable for real-time nutrient levels estimation. Near infrared spectroscopy (NIRS) is a rapid, non-destructive method of composition analyses and is commonly used in agricultural plant and produce quality evaluations. Previous studies have shown potential of NIRS for manure nutrients determination without identifying specific or narrow bands suitable to predict manure nutrients (nitrogen (N), phosphorus (P), etc.). In order to develop miniaturized sensing modules for variable rate manure nutrients applications, research is needed to determine specific wavelengths suitable for predicting the nutrients. The main goal of this study was thus to develop a robust method to determine specific key wavelengths in NIR region for manure nutrients determination.
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