Zohrab Samani

Reference Crop Evapotranspiration from Temperature

MEASURED lysimeter evapotranspiration of Alta fescue grass (a cool season grass) is taken as an index of reference crop evapotranspiration (ETo). An equation is presented that estimates ETo from measured values of daily or mean values of maximum and minimum temperature. This equation is compared with various other methods for estimating ETo. The equation was developed using eight years of daily lysimeter data from Davis, California and used to estimate values of ETo for other locations. Comparisons with other methods with measured cool season grass evapotranspiration at Aspendale, Australia; Lompoc, California; and Seabrook, New Jersey; with lysimeter data from Damin, Haiti; and with the modified Penman for various locations in Bangladesh indicated that the method usually does not require local calibration and that the estimated values are probably as reliable and useable as those from the other estimating methods used for comparison. Considering the scarcity of complete and reliable climatic data for estimating crop water requirements in developing countries, this proposed method can do much to improve irrigation planning design and scheduling in the developing countries.

Anaerobic digestion of municipal solid waste and agricultural waste and the effect of co-digestion with dairy cow manure

Anaerobic digestion of dairy cow manure (CM), the organic fraction of municipal solid waste (OFMSW), and cotton gin waste (CGW) was investigated with a two-phase pilot-scale anaerobic digestion (AD) system. The OFMSW and CM were digested as single wastes and as combined wastes. The single waste digestion of CM resulted in 62m3 methane/ton of CM on dry weight basis. The single waste digestion of OFMSW produced 37m3 methane/ton of dry waste. Co-digestion of OFMSW and CM resulted in 172m3 methane/ton of dry waste. Co-digestion of CGW and CM produced 87m3 methane/ton of dry waste. Comparing the single waste digestions with co-digestion of combined wastes, it was shown that co-digestion resulted in higher methane gas yields. In addition, co-digestion of OFMSW and CM promotes synergistic effects resulting in higher mass conversion and lower weight and volume of digested residual.

Energy recovery from grass using two-phase anaerobic digestion

Municipal solid wastes are major sources of air, water and soil contamination. There is a need for alternative waste management techniques to better utilize the waste and minimize its adverse environmental impact. A two-phase pilot-scale bio-fermentation system was used to evaluate the feasibility of producing methane from grass waste, a major constituent of solid wastes. The bi-phasic system consists of a solid phase and a methane phase. Leachate is re-circulated through the solid phase until a desired level of volatile fatty acid (VFA) is accumulated in the leachate. The leachate is then transferred to the methane reactor where the VFA is converted to methane. The results showed that 67% of the volatile solids in the waste can be converted into soluble chemical oxygen demand in a period of six months. The system produced an average of 0.15 m3 of methane per kg of grass. The average methane concentration in the produced gas was 71%. A mathematical model was developed to estimate the methane and carbon dioxide concentrations in the gas phase as a function of reactor properties.

Remediation of lead contaminated soil by EDTA. I. Batch and column studies

Extraction using ethylenediaminetetraacetic acid (EDTA), and other chelates has been demonstrated to be an effective method of removal of Pb from many contaminated soils. However, column leaching of Pb from alkaline soils with EDTA has been problematic due to extremely low soil permeability. The first purpose of this study was to develop batch extraction procedures and methods of analysis of batch extraction data to provide Pb solubility information which can be used to model the column extraction of Pb from soils. The second purpose was to determine the effect of the addition of KOH and CaCl2 to K2H2EDTA extract solution on both hydraulic conductivity and Pb removal. A Pb-contaminated soil sample was collected from an abandoned battery recycling facility. Both batch shaker extractions and column leaching experiments were completed using 5 different EDTA extract solutions. When only CaCl2 was added to EDTA no change in the amount of Pb removed by batch extraction was observed. As expected, lead solubility was observed to decrease as pH was increased by the addition of KOH. However, Pb solubility was only slightly decreased by the addition of both CaCl2 and KOH. The amount of time required to leach 6.0 L of extraction solution through the soil columns varied from 2 to 33 days. The addition of CaCl2 and/or KOH resulted in increased soil hydraulic conductivity relative to the EDTA-only solution. The hydraulic conductivity was related to residual calcium carbonate content, suggesting that dissolution of CaCO3 and subsequent production of CO2 gas in the soil pores was partially responsible for the observed reductions in soil permeability. However, Pb removal was diminished with the addition of CaCl2 and KOH because of the decreased Pb solubility and also kinetic limitations associated with the shorter residence time of the extract solution in the column.

Remediation of Lead Contaminated Soil by Column Extraction with EDTA: II. Modeling

Lead contamination of soils is a common problem throughout the world. Laboratory batch test and bench scale experiments have shown that EDTA can be used to remove lead from contaminated soils. However, due to the high cost and laborious task associated with actual environmental remediation of a lead contaminated soil, there is a need to be able to predict the outcome of a remediation process in advance in order to optimize the process and minimize the cost. This paper describes the development and validation of a computer model which can be used to simulate the removal of lead from a contaminated soil column using EDTA as the chelating agent. The model is able to simulate the lead removal from soil based on equilibrium as well as kinetic dissolution of Pb. The comparison of the simulated results with actual lead concentrations both in effluent and soil shows that the model can predict the lead removal process with reasonable accuracy.

Converting gin and dairy wastes to methane

Alternatives to gin trash and manure disposal would benefit both the cotton ginning and dairy industries. Anaerobic digestion produces both methane gas and a class A soil amendment. Gin and dairy wastes were combined in the solid phase portion of a two-phase anaerobic system to determine the combinations of temperature, rewetting interval, and mixture ratio that maximize potential methane gas production and minimize process completion time. No significant volatile fatty acid formation occurred after leachate pH approached 7.0, indicating process completion. This took approximately three weeks when temperatures were above 32°C (90°F), mixture ratios were below 5:1 (gin to dairy waste, dry mass basis), and the solid phase was wetted twice daily. Ten percent of the mass was converted to soluble chemical oxygen demand (COD), which has potential for conversion to methane in the second phase.

Using ASTER satellite data to calculate riparian evapotranspiration in the Middle Rio Grande, New Mexico

Riparian evapotranspiration (ET) in the Rio Grande Basin in New Mexico, USA is a major component of the hydrological system. Over a period of several years, ET has been measured in selected locations of dense saltcedar and cottonwood vegetation. Riparian vegetation varies in density, species and soil moisture availability, and to obtain accurate measurements, multiple sampling points are needed, making the process costly and impractical. An alternative solution involves using remotely sensed data to estimate ET over large areas. In this study, daily ET values were measured using eddy covariance flux towers installed in areas of saltcedar and cottonwood vegetation. At these sites, remotely sensed satellite data from the National Aeronautics and Space Administration (NASA) Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were used to calculate the albedo, normalized difference vegetation index (NDVI) and surface temperature. A surface energy balance model was used to calculate ET values from the ASTER data, which were available for 7 days in the year. Comparison between the daily ET values of saltcedar and cottonwood measured from the flux towers and calculated from remote sensing resulted in a mean square error (MSE) of 0.16 and 0.37 mm day−1, respectively. The regional map of ET generated from the remote sensing data demonstrated considerable variation in ET, ranging from 0 to 9.8 mm day−1, with a mean of 5.5 mm day−1 and standard deviation of 1.85 mm day−1 (n = 427481 pixels) excluding open water. This was due to variations in plant variety and density, soil type and moisture availability, and the depth to water table.

Water Budget Calculator Created for Residential Urban Landscapes in Albuquerque, New Mexico

AbstractThe current methods used to calculate urban landscape water budgets are limited because they lack site specificity. The objective of this study was to create a landscape water budget web interface based on ground-proofed information, such as plant coefficients (Ks), vegetation components, and reference evapotranspiration (ETo). Using Albuquerque, New Mexico as the base city, mixed landscape and monthly turf grass coefficients for each zip code in Albuquerque were developed. The spatial variability of zip code ETo and ETo weather anomalies was assessed because of their potential effect on water budgets. Evapotranspiration varied among zip codes, months, and El Nino Southern Oscillation (ENSO) phases. To improve the water budget estimate, the interface accounts for spatial and temporal variability of the monthly, historical (monthly and yearly), and the ENSO phases ETo. Because nonturf landscape plant Kss were unavailable for Albuquerque, the authors developed a Region Match Analysis to transfer non...

PRODUCING ENERGY AND SOIL AMENDMENT FROM DAIRY MANURE AND COTTON GIN WASTE

Millions of tonnes of feedlot manure and cotton gin waste are generated in the U.S. each year. Dairy and feedlot operations in New Mexico produce 1.2 million tonnes of manure annually. Traditionally, manure has been used as a soil amendment in agriculture. However, land application of manure is limited in New Mexico due to problems with salinity, potential groundwater contamination, and limited availability of agricultural land. Waste treatment alternatives are sought. A two-phase anaerobic digestion system was used to evaluate the feasibility of producing methane and soil amendment from mixed agricultural wastes. Cotton gin waste and dairy manure were combined and used as feedstock. Under mesophilic conditions, 48% of the combined waste was converted into biogas. The gas yield was 87 m3 of methane per tonne of mixed waste. Methane concentration in the biogas averaged 72%. Gas production with mixed waste increased 35% compared to digesting dairy waste alone. Nutrient analyses of the residuals showed that they could be used as soil amendments. Residual solid material from the two-phase anaerobic digester had a considerably higher nitrogen and lower sodium content than aerobically composted manure. Anaerobic digestion lasted from one to three months and required 0.15 m3 of water per 1 m3 of waste. Aerobic composting of similar waste in New Mexico takes eight to nine months and consumes 1.2 m3 of water per 1 m3 of waste.

Estimating Solar Radiation from Temperature with Spatial and Temporal Calibration

A procedure is introduced to estimate daily solar radiation from maximum and minimum temperatures for areas where solar radiation is either unavailable or unreliable. The procedure uses historical temperature data for spatial and temporal self-calibration. The results from the self-calibrated procedure are compared with measured solar radiation data in one coastal and two interior regions. The self-calibrated procedure is also compared with an equation presented by Thornton and Running that also uses historical maximum and minimum temperature to estimate solar radiation. The comparison between measured and predicted solar radiation values for several years shows that the self-calibrated method can predict solar radiation with error ranging from 0–3%. The error from the Thornton and Running equation ranges from 7–11%. In general, the Thornton and Running equation tends to overestimate solar radiation especially for overcast sky conditions such as monsoon season.