Towards an Understanding of the Role of Biochar as an Agro-Enviromental Tool: Potential for Control Water Release, Bacterial Retention, and Greenhouse Gas Emissions
Abstract
by Waled Suliman, Ph.D.
Washington State University
August 2014
Co-chairs: Manuel Garcia-Perez/Ann-Marie Fortuna
This dissertation aims to advance our knowledge on the relationship between biochar physico-chemical properties and its performance as a soil amendment. An emphasis was placed on understanding how the feedstock source and pyrolysis conditions influence biochar bulk and surface properties and what effects these properties have on greenhouse gas emissions, soil water retention, and movement of bacteria in sandy soils.
Three lignocellulosic biomass feedstocks (poplar wood, pine bark, and pine wood) were used to produce biochars at six different pyrolysis temperatures (350, 400, 450, 500, 550, and 600oC). It was found that the content of volatiles, the oxygen to carbon (O/C) ratio, and hydrogen to carbon (H/C) ratio decreased linearly with temperature suggesting a gradual increase in aromatic structures and thermal recalcitrance. Pine bark-derived biochars had higher ash content than wood-derived biochars, and as the pyrolysis temperature increased, the ash content also increased.
The surface study showed that biochars produced at low temperature (<500oC) retained some surface functionalities characteristics of the feedstock. The XPS and Boehm titration confirmed that most oxygenated surface functional groups (mainly; carbonyl, carboxyl and hydroxyl groups) are gradually removed as pyrolysis temperature increased. Oxidation by air at 250oC was able to introduce several oxygen functional groups onto the biochar surface. Particularly, the formation of carbonyl and carboxyl groups is facilitated in biochars produced at low temperature. The formation of these oxygenated functional groups contributes additional negative charges on the biochar surface.
Upon biochar application to Quincy sandy soil, it was found that oxidized biochar held significantly more water and this is believed to be related to the content of oxygen functional groups and the pores structure. Oxidized biochars facilitated the transport of Escherichia coli through soil columns likely due to their negative surface charges that could repel bacteria that often carry an overall negative charge. Our results suggest that unoxidized pine wood-derived biochar was effective in reducing the transport of E. coli. Moreover, compared to the soil, biochar amendments did not affect the emissions of N2O but significantly reduced cumulative CO2 emissions (at 95% level of confidence).
This is the abstract of my PhD dissertation
Sample Preparation Technique for Micro- and Nano-structure Characterization of Biochar using SEM and TEM Microscopy
This abstract was accepted at the "Electron Microscopy for Biological, Environmental, and Energy Research (EMBEER) Symposium", held at the Pacific Northwest National Laboratory (PNNL), 2015, Richland, WA.
Accepted Abstract
By Waled Suliman, Manuel Raul Pelaez-Samaniego, and Manuel Garcia-Pérez
Routine biochar sample preparation techniques for microscopic investigations usually include cross-sectioning, hand crushing, or powdering of already produced biochars. Since these traditional techniques are conducted after the production of biochar, the biochar particles are subjected to cutting and crushing forces that result from the sample preparation, which affects the sample morphology and, possibly, its structure, thus resulting in misleading topographical information about the effect of charcoaling of lignocellulosic biomass. Additionally, pyrolysis liquid intermediates or lignin-carbohydrate compounds (LCC) either trapped inside the cell walls or deposited on the surfaces of the biochar particles during the pyrolysis process could have been partially removed or affected on their structure and morphology during the sample preparation of biochar. Partial removal, in particular, may also lead to inaccurate estimations of macro/micropore size, wall thickness, and orientation of the carbon sheets in biochars. Therefore, sample preparation techniques to avoid alteration of charcoal particles structure are required. The present study describes a technique for biochar sample preparation for microscopic studies. Small wood pieces were cross-sectioned and powdered for microscopic studies prior biochar production via fast pyrolysis, using a tube furnace (spoon) reactor. The samples were then soaked in an ethanol-toluene mixture for 10 min for partial removal of extractives, dried at room temperature, and pyrolyzed at 350 and 600oC for 30 mins. Visualization of the structure and morphology of the biochar particles was performed using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). This technique allowed us to reveal distinctive topographic features and degrees of disorder of the biochar structures, which can help for a better understanding of the biochar production process and for designing potential uses of biochar.
Practicality of biochar additions for sustainable use of irrigation water: influence on water retention characteristics of the Quincy sandy soil
This abstract was accepted at the "The 2014 Water for Food Global Conference", October 19-22, Seattle, WA.
Accepted Abstract
by Waled Suliman*, James B. Harsh, Nehal I. Abu-Lail, Ann-Marie Fortuna, and Manuel Garcia-Perez
Irrigated agriculture is by far the largest water-use sector, 70% of the world’s useable water is consumed in agriculture. With the population growing to 8.1 billion by 2025, water irrigation rates have to increase to meet global food production needs. Crop yields and yield potentials on sandy soils are strongly limited due to restricted nutrient retention and water-holding capacity. Application of biochar in agricultural systems has been reported to improve soil properties for plant growth. Little, however, is known about biochar effects on sandy soil hydrological properties. The objective of this research was to evaluate the efficacy of biochar on the water retention capacity of Quincy sandy soil. The applied biochars were produced at 350 and 600oC from three different biomass feedstocks (poplar and pine woods, and pine bark) using lab scale spoon pyrolysis reactor. We determined water retention, plant-available water content, water content at field capacity, permanent wilting point, porosity, and selected chemical properties of biochar-amended sandy soil microcosms. At application rate of 15 ton/ha, we found an increase in plant-available water in the Quincy sandy soil proportional to the biochar type, with about 21.7%, 16.6% and 15.7% for poplar wood, pine bark, and pine wood biochars, respectively. The increase in water content at field capacity is likely attributed to an increase in overall porosity due to biochar additions. According to our results, use of biochar can be a worthy strategy to improve water storage and reduce overall water use in irrigated agricultural systems.
Modification of Bio-char Surface by Air Oxidation: Role of Pyrolysis Temperature
This abstract was accepted at the "Biorefinery I: Chemicals and Materials From Thermo-Chemical Biomass Conversion and Related Processes", Sep. 27- Oct. 2st 2015, Chania, Greece
Accepted Abstract
by Waled Suliman*, James B. Harsh, Nehal I. Abu-Lail, Ann-Marie Fortuna, and Manuel Garcia-Perez
This paper reports results on the effect of pyrolysis temperature in the range between 350 and 600 oC on the oxidability of bio-chars derived from hybrid Poplar, Pine Wood and Pine Bark. The oxidation step for all the bio-char produced was conducted at 250oC in the presence of air in a spoon reactor. The elemental and proximate analyses of all the oxidized and un-oxidized chars suggest that the carbonaceous materials produced at low temperature is more susceptible to oxidation than those obtained at high temperature. A number of surface properties of resultant biochars were examined to better understand how pyrolysis temperatures and feedstock sources relate to the development of surface characteristics. The removal of volatiles during the pyrolysis step resulted in the gradual creation of microporosity detectable by CO2 adsorption but which was difficult to detect with N2 adsorption, suggesting that the chars contain micropores mostly less than 1 nm in entrance dimension. In some cases the surface area decreased after being oxidized likely due to the blockage of micropores by oxygen-containing functional groups. The surface composition determined by XPS and Boehm titration confirms that the formation of carbonyl and carboxyl groups is easier for biochars produced at low temperature. The formation of these oxygenated functional groups contributes to add negative charges on the surface and consequently the pH at the point of zero charge is always higher for un-oxidized bio-chars. The cation exchange capacity of oxidized bio-chars was always higher.
Effect of Biochar Addition on CO2 and N2O Fluxes, and Inorganic-N contents in Quincy Sand: A Short-Term Laboratory Study
Abstract
by Waled Suliman*, James B. Harsh, Nehal I. Abu-Lail, Ann-Marie Fortuna, and Manuel Garcia-Perez
The incorporation of biochar into the soil has been advocated as a carbon sequestration method and environmental tool. Biochar also has the potential to influence the soil N cycle by altering nitrifi cation rates and by adsorbing NH4 + or NH3. A laboratory study was performed to examine the effect of biochar incorporation into sandy soil on N2O and CO2 emissions, and inorganic-N contents, following the application of N-fertilizer (Urea). Incubation experiments were conducted with unfertilized and fertilized soil amended with different amounts (10, 15 and 20 tons ha-1) of low- and high-temperature biochars (LTB and HTB, respectively). During the first week of incubation, emissions of CO2 from LTB-amended microcosms were generally higher than HTB-amended microcosms. This variation was linked to the different quantities of labile carbon between LTB and HTB biochars. Emissions of N2O from the biochar amended microcosms were generally lower than from controls (soil alone) during the first 7 days, but after day 14 there was no significant difference. Inorganic N pool was clearly influenced by biochar addition; the NO3 decreased as biochar doses increased while NH4+ differed between treatments. In general, the inorganic-N pool available for N2O-producing mechanisms was reduced by adding biochar, suggesting a mechanistic link to the observed reduction in N2O emissions.
Towards the Quantification of The Effects of Biochar Oxidation and Pyrolysis Temperature on the Transport of Pathogenic and Non-Pathogenic E. coli in Biochar-Amended Sand Columns
This abstract was accepted at the "The International Annual Meetings of the ASA, CSSA, and SSSA", Nov.15-18, Minneapolis, MN
Accepted Abstract
by Waled Suliman*, James B. Harsh, Ann-Marie Fortuna, Manuel Garcia-Perez, and Nehal I. Abu-Lail
A detailed understanding of the transport of Escherichia coli O157:H7 within the soil-groundwater system is critical to the protection of public health. Although incorporation of biochar, a carbon-rich porous material, into soils has a potential for reducing the leaching of manure-borne pathogens, knowledge concerning the impact of biochar surface functionality on the retention and transport of E. coli O157:H7 is still largely missing. The main objective of this research was to evaluate whether the addition of un-oxidized and oxidized biochar to a sandy soil affected the transport of E. coli strains through water-saturated soil columns. We hypothesized that the transport of E. coli through bio-char-amended soils will depend on biochar surface chemistry. To test our hypothesis, we quantified the transport of E. coli O157:H7 and E. coli K12 in water-saturated column experiments for Quency sand amended with 20% pine wood or pine bark biochars produced at 350 and 600°C using lab scale spoon pyrolysis reactor. Our results showed that (1) Oxidized biochar could enhance the transport of E. coli O157:H7 cells due to surface charge effects; (2) E. coli O157:H7 displayed higher retention then E. coli K12 in biochar-amended soil under experimental pH conditions tested; (3) increased biochar application rates (from 0 to 20%) led to a reduction in the transport of both bacterial strains from 95 to 35%; (4) increased transport was observed for the pine bark biochar produced at 600 oC whereas reduced transport was observed for the pine wood biochar produced at the same pyrolysis temperature. Our results suggest that un-oxidized pine wood biochar produced at 350oC was effective in reducing transport of E. coli in the Quincy sand.
Effect of Pyrolysis Temperature and Post-pyrolysis Oxidation on the Physico-chemical Properties of Biochars
This abstract was accepted at the "The ASABE Annual International Meeting", July 26-29, New Orleans.
Accepted Abstract
by Waled Suliman*, James B. Harsh, Nehal I. Abu-Lail, Ann-Marie Fortuna, and Manuel Garcia-Perez
Thirty-six bio-char samples were produced from the pyrolysis of pine wood (PW), pine bark (PB), and hybrid poplar wood (HP) at six temperatures (350, 400, 450, 500, 550 and 600oC) in a lab scale spoon reactor. The study aimed to the effect of pyrolysis temperature and air oxidation on bulk and surface physico-chemical properties of biochars. Changes in the bulk composition of the biochar produced were examined by elemental and proximate analyses while changes in the surface chemistry was studied by Boehm titration and XPS analysis methods. The elemental and proximate analyses of all the oxidized and unoxidized biochars suggest that the content of volatiles, oxygen, nitrogen and hydrogen decreased linearly with pyrolysis temperature. The removal of volatiles during the pyrolysis step resulted in the gradual creation of microporosity detectable by CO2 adsorption. The surface composition determined by XPS and Boehm titration confirms that the formation of oxygenated functional groups is easier for biochars produced at low temperature. The biochars produced at low temperature is more susceptible to oxidation than those obtained at high temperature. This work illustrates the relative importance of pyrolysis temperature and post-pyrolysis oxidation on the bulk and surface properties of bio-char products.
Three more accepted abstracts will be posted later,
Thanks!
