Papers by Mahmoud Sharara
BioResources, 2014
Biochars form recalcitrant carbon and increase water and nutrient retention in soils; however, th... more Biochars form recalcitrant carbon and increase water and nutrient retention in soils; however, the magnitude is contingent upon production conditions and thermo-chemical conversion processes. Herein we aim at (i) characterizing switchgrass (Panicum virgatum L.)-biochar morphology, (ii) estimating water-holding capacity under increasing ratios of char: soil; and, (iii) determining nutrient profile variation as a function of pyrolysis conversion methodologies (i.e. continuous, auger pyrolysis system versus batch pyrolysis systems) for terminal use as a soil amendment. Auger system chars produced at 600°C had the greatest lignin portion by weight among the biochars produced from the continuous system. On the other hand, a batch pyrolysis system (400 °C -3h) yielded biochar with 73.10% lignin (12 fold increases), indicating higher recalcitrance, whereas lower production temperatures (400 °C) yielded greater hemicellulose (i.e. greater mineralization promoting substrate). Under both pyrolysis methods, increasing biochar soil application rates resulted in linear decreases in bulk density (g cm -3 ). Increases in auger-char (400 °C) applications increased soil water-holding capacities; however, application rates of >2 Mt ha -1 are required. Pyrolysis batch chars did not influence water-holding abilities (P>0.05). Biochar macro and micronutrients increased, as the pyrolysis temperature increased in the auger system from 400 to 600 °C, and the residence time increased in the batch pyrolysis system from 1 to 3 h. Conversely, nitrogen levels tended to decrease under the two previously mentioned conditions. Consequently, not all chars are inherently equal, in that varying operation systems, residence times, and production conditions greatly affect uses as a soil amendment and overall rate of efficacy.
2012 Dallas, Texas, July 29 - August 1, 2012, 2012
Aquatic biomass; i.e., algae have been successfully incorporated in wastewater treatment as nutri... more Aquatic biomass; i.e., algae have been successfully incorporated in wastewater treatment as nutrients strippers. Low-maintenance algal communities; i.e., wild species, can be a cheap and effective sequestration strategy. Few studies have investigated the quality of wastewater treatment algae as a potential feedstock for thermochemical conversion in atmospheric gasification. This study is a preliminary investigation of the gasification of wastewater treatment algae as means to produce renewable gaseous fuel streams, and also to condense minerals and micro-nutrients into easily managed char using an auger gasifier. Three temperature conditions were investigated in this study; 760, 860 and 960 °C. Temperatures were found to increase the concentration of CO, and H 2 in producer gas from 12. 8% and 4.7% (vol.) at 760 °C to 16.9% and 11.4% at 960 °C, respectively. On the other hand, concentration of CO 2 in producer gas decreased from 14. 0% to 11.6% (vol.) with the increase in temperatures from 760 °C to 960 °C, respectively. Tar yields ranged between 15% and 16.6%, whereas char yields fell between 46% and 51% due to the significantly high ash content of raw algae; >40% dry-basis. The high ash content in char, however, might bolster gasification as a minerals concentration step which would facilitate transportation, and re-use of these minerals. Future studies will further investigate the thermodynamic performance of auger gasification on aquatic biomass. Also, fate of various minerals after this process will be investigated in future research.
Journal of Sustainable Bioenergy Systems, 2014
Biomass gasification is a well-developed technology with the potential to convert agricultural re... more Biomass gasification is a well-developed technology with the potential to convert agricultural residues to value-added products. The availability of on-farm gasifiers that can handle low-density agricultural wastes such as soybean residue, an underutilized feedstock, is limited. Therefore, the goal of this research was to install and assess an allothermal, externally heated, auger gasifier capable of converting agricultural wastes to combustible gas for on-farm grain drying. The system was used to convert soybean residues under different reactor temperature, i.e., 700˚C, 750˚C, 800˚C, and 850˚C. The results showed that increasing the reactor temperature from 700˚C to 850˚C increased the producer gas molar fractions of H2, CO, and CH 4 , from 1.1% to 1.5%, from 15.0% to 23.8%, and from 5.1% to 7.7%, respectively. The higher heating value of the producer gas reached 6.3 MJ/m 3 at reactor temperature of 850˚C. Specific gas yield increased from 0.32 to 0.58 m 3 /kg biomass while char and particulate yield decreased from 41.7% to 33.6% by increasing the reactor temperature from 700˚C to 850˚C. Maximum carbon sequestration achieved, in the form of biochar-carbon, was 32% of the raw feedstock carbon. Gasification of collectable soybean residues from 1 acre would be sufficient to dry 1132 kg of soybean seeds (the average yield from one acre) from moisture content of 20% to 13% (wet, weight basis). Furthermore, about 300 kg of biochar, a value-added soil conditioner, could be produced and applied to the soybean land as a bio-fertilizer.
Energies, 2014
Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promote... more Switchgrass is a high yielding, low-input intensive, native perennial grass that has been promoted as a major second-generation bioenergy crop. Raw switchgrass is not a readily acceptable feedstock in existing power plants that were built to accommodate coal and peat. The objective of this research was to elucidate some of the characteristics of switchgrass biochar produced via carbonization and to explore its potential use as a solid fuel. Samples were carbonized in a batch reactor under reactor temperatures of 300, 350 and 400 °C for 1, 2 and 3 h residence times. Biochar mass yield and volatile solids decreased from 82.6% to 35.2% and from 72.1% to 43.9%, respectively, by increasing carbonization temperatures from 300 °C to 400 °C and residence times from 1 h to 3 h. Conversely, biochar heating value (HV) and fixed carbon content increased from 17.6 MJ kg −1 to 21.9 MJ kg −1 and from 22.5% to 44.9%, respectively, under the same conditions. A biomass discoloration index (BDI) was created to quantify changes in biochar colors as affected by the two tested parameters. The maximum BDI of 77% was achieved at a carbonization temperature of 400 °C and a residence time of 3 h. The use of this index could be expanded to quantify biochar characteristics as affected by thermochemical treatments. Carbonized biochar could be considered a high quality solid fuel based on its energy content.
Journal of Sustainable Bioenergy Systems, 2014
The modern trend of increasing the number of pigs at production sites led to a noticeable surplus... more The modern trend of increasing the number of pigs at production sites led to a noticeable surplus of manure. Separation of manure solids provides an avenue of their utility via thermochemical conversion techniques. Therefore, the goal of this paper was to assess the physical and thermal properties of solid separated swine manure obtained from two different farms, i.e., farrowing, and growing-finishing, and to determine their pyrolysis kinetic parameters. Swine manure solids were dried and milled prior to assessing their properties. Differential and integral isoconversional methods (Friedman, and Flynn-Wall-Ozawa) were used to determine the apparent activation energy as a function of the conversion ratio. Significant differences were observed in the proximate, ultimate composition between both manure types. The higher heating value (HHV) for the manure solids from farrowing, and growing-finishing farms reached 16.6 MJ/kg and 19.4 MJ/kg, respectively. The apparent activation energy computed using Friedman and FWO methods increased with the increase in the degree of conversion. Between 10% and 40% degrees of conversion, the average activation energies, using Friedman method, were103 and 116 kJ/mol for the farrowing and growing-finishing manure solids, respectively. On the other hand, the same activation energies, calculated from FWO method, were 98 and 104 kJ/mol, for solid manure obtained from farrowing and growing-finishing farms, respectively. The findings in this study will assist in the effort to optimize thermochemical conversion processes to accommodate swine waste. This could, in turn, minimize swine production impacts on the surrounding ecologies and provide sustainable energy and biochar streams.
Phytochemicals, Primary Metabolites and Value-Added Biomass Processing, 2012
Bioresource technology, 2014
Characterization of algae grown using swine manure slurry in different seasons. Determination of ... more Characterization of algae grown using swine manure slurry in different seasons. Determination of pyrolysis TG-DTG characteristics under different heating rates. Determination of apparent activation energies using isoconversional methods. Modeling algae consortia pyrolysis as four independent parallel reactions.
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Papers by Mahmoud Sharara