Chayan Saha - Academia.edu (original) (raw)

Papers by Chayan Saha

Progressive Agriculture, 2019

Mechanical intervention in each stage of post-harvest operation of paddy is time demand due to in... more Mechanical intervention in each stage of post-harvest operation of paddy is time demand due to increased cost of labour as well as shifting of labour from agriculture to non-agriculture sector. Mitigation of food demand of rapidly increasing population is becoming a major future challenge in agriculture sector. Drying of paddy is important for maintaining quality and long term storage of paddy. Among the drying methods, traditional sun drying is the most common practice in Bangladesh. Normally, farmers use yard in wet season (Boro & Aus) and field in dry season (Aman) to dry paddy. In this case, appropriate paddy drying technology could play a vital role to strengthen food security by reducing drying loss. Therefore, a study was conducted to investigate the drying loss of paddy both in traditional sun drying and mechanized drying method (BAU-STR dryer) at selected areas of Bangladesh. Popular and mega rice varieties cv. BRRI dhan28 and BRRI dhan49 were used as drying materials to ev...

Sustainability, 2020

Converting organic waste into energy through anaerobic digestion is gaining popularity day by day... more Converting organic waste into energy through anaerobic digestion is gaining popularity day by day. The reactor temperature is considered as one of the most vital factors for the digestion process. An experiment was conducted in the Biogas Laboratory of Green Energy Knowledge Hub at Bangladesh Agricultural University (BAU) to examine the influence of temperature on anaerobic digestion of cow-dung. Laboratory-scale continuous stirred tank reactors with a working volume of 15 L were operated for a 30-day retention time. The reactors were set at 20 °C, 25 °C, 30 °C, 35 °C, 40 °C and 45 °C, respectively to determine the effect of temperature on anaerobic digestion performance. Different parameters like total solids, volatile solids, pH, volatile fatty acids, ammonia nitrogen, total nitrogen, biogas production rate and methane concentration were examined. Among all the reactors, the reactor at 40 °C temperature produced maximum biogas (312.43 L/kg VS) and methane yields (209.70 L/kg VS), ...

Agricultural Engineering International: The CIGR Journal, 2016

The mechanization status of dairy farming in Bangladesh is not mentionable. In every steps of the... more The mechanization status of dairy farming in Bangladesh is not mentionable. In every steps of the farming operation, indigenous systems have been practiced in most of the farms. This study has been conducted to assess mechanization status in dairy farming. The selected areas of this study were Bangladesh Agricultural University (BAU) dairy farm, Mymensingh, Rural Development Academy (RDA) dairy farm, Bogra and four small, four medium and two large farms in Sirajganj district. Most mechanized RDA dairy farm and rest of the non-mechanized farms were selected for this study. The field survey was conducted by interviewing identified sample respondents with pre-determined interview schedules to cover all selected locations. Most of the farms have no specific designed farm building with specific space per animal, feeding alley, manger, gutter and drainage system, ventilation system. Even the manure management system in study area was very poor. A biogas plant can utilize manure properly. ...

Water Research, 2015

Knowledge about characteristics of gas releases from various types of organic wastes can assist i... more Knowledge about characteristics of gas releases from various types of organic wastes can assist in developing gas pollution reduction technologies and establishing environmental regulations. Five different organic wastes, i.e., four types of animal manure (swine, beef, dairy, and layer hen) and municipal wastewater, were studied for their characteristics of ammonia (NH3), carbon dioxide (CO2), hydrogen sulfide (H2S), and sulfur dioxide (SO2) releases for 38 or 43 days in reactors under laboratory conditions. Weekly waste additions and continuous reactor headspace ventilation were supplied to simulate waste storage conditions. Results demonstrated that among the five waste types, layer hen manure and municipal wastewater had the highest and lowest NH3 release potentials, respectively. Layer manure had the highest and dairy manure had the lowest CO2 release potentials. Dairy manure and layer manure had the highest and lowest H2S release potentials, respectively. Beef manure and layer manure had the highest and lowest SO2 releases, respectively. The physicochemical characteristics of the different types of wastes, especially the total nitrogen, total ammoniacal nitrogen, dry matter, and pH, had strong influence on the releases of the four gases. Even for the same type of waste, the variation in physicochemical characteristics affected the gas releases remarkably.

ABSTRACT Air flow measurements as well as concentration measurements within a naturally ventilate... more ABSTRACT Air flow measurements as well as concentration measurements within a naturally ventilated dairy barn (NVD) were carried out during one summer season of 2012. Air flow measurements were performed using ultrasonic anemometers (UA), either as short duration (20 min duration) measurements with a higher spatial distribution (using up to 9 UAs at the same time) or as long period (roughly 2 weeks) measurements with a lower spatial resolution (3 to 5 UAs). Measurements were conducted at two heights, at 1.5 m within the animal occupied zone (AOZ) and at 2.6 m height above the AOZ for understanding the distribution of airflow within the building. The three wind components (u, v and w) were measured either as lateral profile or evenly distributed at the ground area of the building. The results showed that wind speeds measured at the height 2.6 m were generally smaller than wind speeds measured at the height 1.5 m. The analysis of the lateral profile showed that only the first third of the wind facing side seem to benefit from the approaching wind. The long term measurements (duration 2 weeks) showed a high variability in the data and a correlation analysis showed lower CO2 concentrations for higher wind speeds. However, the linear correlation was weak (p= -0.7), which implies that the relationship cannot be described simply by a linear correlation.

ABSTRACT Accurate quantification of gaseous emissions from livestock buildings to the atmosphere ... more ABSTRACT Accurate quantification of gaseous emissions from livestock buildings to the atmosphere requires accurate determination of the ventilation rate and the representative gas concentration in the exhaust air. But there is a lack in the investigation of reasons and uncertainties for selecting sampling points and locations in naturally ventilated dairy (NVD) buildings. The objective of this study was to investigate uncertainties in calculating AER based on carbon dioxide (CO2) balance method. The experiment was carried out in an NVD building located in north-east Germany. Concentrations of CO2 were continuously measured inside the barn at eight uniformly distributed points and outside the barn at four points. Air exchange rate (AER) per hour was calculated using the concentration difference between inside and outside the barn where inside concentrations of 4 sampling locations left (4PL), middle (4PM), right (4PR) and corner (4PC) of the barn, 6 sampling locations in left (6PL), right (6PR) and randomly (6RS) selected points inside the barn were used, then compared with AER calculated using an average CO2 concentration of 8 sampling points (8PA) according to the CO2 balance method. The results showed that the relative AER calculation differences using 4PL, 4PM, 4PR, 4PC, 6PL, 6PR, and 6 RS were -49 to 112%, -5 to 26%, -29 to 34%, -12 to 13%, -5 to 44%, -14 to 10% and -8 to 4% compared to 8PA. The variations in relative differences are because of uncertainties involved in concentration measurement due to the variations of outside wind speed and direction.

Computers and Electronics in Agriculture, 2011

Biosystems Engineering, 2009

Biosystems Engineering, 2009

Biosystems Engineering, 2010

Biosystems Engineering, 2011

Biosystems Engineering, 2013

ABSTRACT Natural ventilation (NV) of buildings refers to the exchange of indoor air with outdoor ... more ABSTRACT Natural ventilation (NV) of buildings refers to the exchange of indoor air with outdoor air due to pressure differences caused by wind and/or buoyancy. Increased knowledge of the factors that affect NV and emissions from naturally ventilated dairy (NVD) buildings may lead to a better understanding of indoor air quality, an improvement of emission abatement technologies and a refinement of emission models. The influence of external wind speed and direction on point concentration, air change rate, ammonia (NH3) and methane (CH4) emissions was evaluated in an NVD building located in northern Germany. The measured data were classified according to four wind direction groups: 0°–10° (N), 85°–95° (E), 175°–185° (S), and 265°–275° (W), with consideration for similar wind frequencies and representation of each major side for further analyses and comparisons. The results showed that wind speed and wind direction had significant influence on air change per hour (ACH) (P < 0.05) both individually and when interacting. In contrast, only wind speed and interactions of external wind speed and direction significantly affected NH3 and CH4 emissions (P < 0.05). The surrounding obstacles, other climate parameters (temperature and relative humidity) and other emission sources should be taken into account when interpreting the effects of wind direction on ACH and emissions. Empirical models for ACH, NH3 and CH4 emissions were developed. Intensive experiments in the lab (e.g. scale model in boundary layer wind tunnel) and long-term measurement including all seasons at full scale are required to establish a good empirical model.

Science of The Total Environment, 2011

Identification of different factors that affect emissions of gasses, including volatile organic c... more Identification of different factors that affect emissions of gasses, including volatile organic compounds (VOCs) is necessary to develop emission abatement technology. The objectives of this research were to quantify and study temporal variation of gas emissions from a model pig house under varying ventilation rates. The used model was a 1:12.5 scale of a section of a commercial finishing pig house. The VOC concentrations at inlet, outlet, and slurry pit of the model space were measured using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). PTR-MS can measure the temporal variations of odor compounds' emission from the slurry pit in real time. The emissions of H(2)S and 14 VOCs were lower compared to real pig buildings except for ammonia, which indicated possible other sources of those compounds than the slurry in the slurry pit. The ventilation rate affected significantly on ammonia and trimethylamine emission (p<0.05). The hydrogen sulfide (H(2)S) emission was independent of the ventilation rate. VFAs' emission dependency on ventilation rate increased with the increase of carbon chain. Phenols, indoles and ketones showed the positive correlation with ventilation rate to some extent. Generally, compounds with high solubility (low Henry's constant) showed stronger correlation with ventilation rates than the compounds with high Henry's constant.

Biosystems Engineering, 2010

Progressive Agriculture, 2019

Mechanical intervention in each stage of post-harvest operation of paddy is time demand due to in... more Mechanical intervention in each stage of post-harvest operation of paddy is time demand due to increased cost of labour as well as shifting of labour from agriculture to non-agriculture sector. Mitigation of food demand of rapidly increasing population is becoming a major future challenge in agriculture sector. Drying of paddy is important for maintaining quality and long term storage of paddy. Among the drying methods, traditional sun drying is the most common practice in Bangladesh. Normally, farmers use yard in wet season (Boro & Aus) and field in dry season (Aman) to dry paddy. In this case, appropriate paddy drying technology could play a vital role to strengthen food security by reducing drying loss. Therefore, a study was conducted to investigate the drying loss of paddy both in traditional sun drying and mechanized drying method (BAU-STR dryer) at selected areas of Bangladesh. Popular and mega rice varieties cv. BRRI dhan28 and BRRI dhan49 were used as drying materials to ev...

Sustainability, 2020

Converting organic waste into energy through anaerobic digestion is gaining popularity day by day... more Converting organic waste into energy through anaerobic digestion is gaining popularity day by day. The reactor temperature is considered as one of the most vital factors for the digestion process. An experiment was conducted in the Biogas Laboratory of Green Energy Knowledge Hub at Bangladesh Agricultural University (BAU) to examine the influence of temperature on anaerobic digestion of cow-dung. Laboratory-scale continuous stirred tank reactors with a working volume of 15 L were operated for a 30-day retention time. The reactors were set at 20 °C, 25 °C, 30 °C, 35 °C, 40 °C and 45 °C, respectively to determine the effect of temperature on anaerobic digestion performance. Different parameters like total solids, volatile solids, pH, volatile fatty acids, ammonia nitrogen, total nitrogen, biogas production rate and methane concentration were examined. Among all the reactors, the reactor at 40 °C temperature produced maximum biogas (312.43 L/kg VS) and methane yields (209.70 L/kg VS), ...

Agricultural Engineering International: The CIGR Journal, 2016

The mechanization status of dairy farming in Bangladesh is not mentionable. In every steps of the... more The mechanization status of dairy farming in Bangladesh is not mentionable. In every steps of the farming operation, indigenous systems have been practiced in most of the farms. This study has been conducted to assess mechanization status in dairy farming. The selected areas of this study were Bangladesh Agricultural University (BAU) dairy farm, Mymensingh, Rural Development Academy (RDA) dairy farm, Bogra and four small, four medium and two large farms in Sirajganj district. Most mechanized RDA dairy farm and rest of the non-mechanized farms were selected for this study. The field survey was conducted by interviewing identified sample respondents with pre-determined interview schedules to cover all selected locations. Most of the farms have no specific designed farm building with specific space per animal, feeding alley, manger, gutter and drainage system, ventilation system. Even the manure management system in study area was very poor. A biogas plant can utilize manure properly. ...

Water Research, 2015

Knowledge about characteristics of gas releases from various types of organic wastes can assist i... more Knowledge about characteristics of gas releases from various types of organic wastes can assist in developing gas pollution reduction technologies and establishing environmental regulations. Five different organic wastes, i.e., four types of animal manure (swine, beef, dairy, and layer hen) and municipal wastewater, were studied for their characteristics of ammonia (NH3), carbon dioxide (CO2), hydrogen sulfide (H2S), and sulfur dioxide (SO2) releases for 38 or 43 days in reactors under laboratory conditions. Weekly waste additions and continuous reactor headspace ventilation were supplied to simulate waste storage conditions. Results demonstrated that among the five waste types, layer hen manure and municipal wastewater had the highest and lowest NH3 release potentials, respectively. Layer manure had the highest and dairy manure had the lowest CO2 release potentials. Dairy manure and layer manure had the highest and lowest H2S release potentials, respectively. Beef manure and layer manure had the highest and lowest SO2 releases, respectively. The physicochemical characteristics of the different types of wastes, especially the total nitrogen, total ammoniacal nitrogen, dry matter, and pH, had strong influence on the releases of the four gases. Even for the same type of waste, the variation in physicochemical characteristics affected the gas releases remarkably.

ABSTRACT Air flow measurements as well as concentration measurements within a naturally ventilate... more ABSTRACT Air flow measurements as well as concentration measurements within a naturally ventilated dairy barn (NVD) were carried out during one summer season of 2012. Air flow measurements were performed using ultrasonic anemometers (UA), either as short duration (20 min duration) measurements with a higher spatial distribution (using up to 9 UAs at the same time) or as long period (roughly 2 weeks) measurements with a lower spatial resolution (3 to 5 UAs). Measurements were conducted at two heights, at 1.5 m within the animal occupied zone (AOZ) and at 2.6 m height above the AOZ for understanding the distribution of airflow within the building. The three wind components (u, v and w) were measured either as lateral profile or evenly distributed at the ground area of the building. The results showed that wind speeds measured at the height 2.6 m were generally smaller than wind speeds measured at the height 1.5 m. The analysis of the lateral profile showed that only the first third of the wind facing side seem to benefit from the approaching wind. The long term measurements (duration 2 weeks) showed a high variability in the data and a correlation analysis showed lower CO2 concentrations for higher wind speeds. However, the linear correlation was weak (p= -0.7), which implies that the relationship cannot be described simply by a linear correlation.

ABSTRACT Accurate quantification of gaseous emissions from livestock buildings to the atmosphere ... more ABSTRACT Accurate quantification of gaseous emissions from livestock buildings to the atmosphere requires accurate determination of the ventilation rate and the representative gas concentration in the exhaust air. But there is a lack in the investigation of reasons and uncertainties for selecting sampling points and locations in naturally ventilated dairy (NVD) buildings. The objective of this study was to investigate uncertainties in calculating AER based on carbon dioxide (CO2) balance method. The experiment was carried out in an NVD building located in north-east Germany. Concentrations of CO2 were continuously measured inside the barn at eight uniformly distributed points and outside the barn at four points. Air exchange rate (AER) per hour was calculated using the concentration difference between inside and outside the barn where inside concentrations of 4 sampling locations left (4PL), middle (4PM), right (4PR) and corner (4PC) of the barn, 6 sampling locations in left (6PL), right (6PR) and randomly (6RS) selected points inside the barn were used, then compared with AER calculated using an average CO2 concentration of 8 sampling points (8PA) according to the CO2 balance method. The results showed that the relative AER calculation differences using 4PL, 4PM, 4PR, 4PC, 6PL, 6PR, and 6 RS were -49 to 112%, -5 to 26%, -29 to 34%, -12 to 13%, -5 to 44%, -14 to 10% and -8 to 4% compared to 8PA. The variations in relative differences are because of uncertainties involved in concentration measurement due to the variations of outside wind speed and direction.

Computers and Electronics in Agriculture, 2011

Biosystems Engineering, 2009

Biosystems Engineering, 2009

Biosystems Engineering, 2010

Biosystems Engineering, 2011

Biosystems Engineering, 2013

ABSTRACT Natural ventilation (NV) of buildings refers to the exchange of indoor air with outdoor ... more ABSTRACT Natural ventilation (NV) of buildings refers to the exchange of indoor air with outdoor air due to pressure differences caused by wind and/or buoyancy. Increased knowledge of the factors that affect NV and emissions from naturally ventilated dairy (NVD) buildings may lead to a better understanding of indoor air quality, an improvement of emission abatement technologies and a refinement of emission models. The influence of external wind speed and direction on point concentration, air change rate, ammonia (NH3) and methane (CH4) emissions was evaluated in an NVD building located in northern Germany. The measured data were classified according to four wind direction groups: 0°–10° (N), 85°–95° (E), 175°–185° (S), and 265°–275° (W), with consideration for similar wind frequencies and representation of each major side for further analyses and comparisons. The results showed that wind speed and wind direction had significant influence on air change per hour (ACH) (P < 0.05) both individually and when interacting. In contrast, only wind speed and interactions of external wind speed and direction significantly affected NH3 and CH4 emissions (P < 0.05). The surrounding obstacles, other climate parameters (temperature and relative humidity) and other emission sources should be taken into account when interpreting the effects of wind direction on ACH and emissions. Empirical models for ACH, NH3 and CH4 emissions were developed. Intensive experiments in the lab (e.g. scale model in boundary layer wind tunnel) and long-term measurement including all seasons at full scale are required to establish a good empirical model.

Science of The Total Environment, 2011

Identification of different factors that affect emissions of gasses, including volatile organic c... more Identification of different factors that affect emissions of gasses, including volatile organic compounds (VOCs) is necessary to develop emission abatement technology. The objectives of this research were to quantify and study temporal variation of gas emissions from a model pig house under varying ventilation rates. The used model was a 1:12.5 scale of a section of a commercial finishing pig house. The VOC concentrations at inlet, outlet, and slurry pit of the model space were measured using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS). PTR-MS can measure the temporal variations of odor compounds' emission from the slurry pit in real time. The emissions of H(2)S and 14 VOCs were lower compared to real pig buildings except for ammonia, which indicated possible other sources of those compounds than the slurry in the slurry pit. The ventilation rate affected significantly on ammonia and trimethylamine emission (p<0.05). The hydrogen sulfide (H(2)S) emission was independent of the ventilation rate. VFAs' emission dependency on ventilation rate increased with the increase of carbon chain. Phenols, indoles and ketones showed the positive correlation with ventilation rate to some extent. Generally, compounds with high solubility (low Henry's constant) showed stronger correlation with ventilation rates than the compounds with high Henry's constant.

Biosystems Engineering, 2010