Erin N. Yargicoglu

Characteristics and Applications of Biochar for Environmental Remediation: A Review

Biochar is a stabilized, recalcitrant organic carbon compound, created when biomass is heated to temperatures usually between 300 and 1000°C, under low (preferably zero) oxygen concentrations. It is produced from a variety of biomass feedstock, such as agricultural residues, wood chips, manure, and municipal solid waste, through a variety of thermal treatments, among which slow pyrolysis is the most widely used due to its moderate operating conditions and optimization of biochar yields. Despite the recent introduction of the term biochar for this material, there have been several applications of charred materials in the past due to their unique properties (e.g., high specific surface area, microporosity, and sorptive capabilities). These early applications have primarily focused on the use of biochar as a soil amendment in agriculture, though other applications in environmental remediation engineering may be equally important (i.e., for soil and groundwater treatment and stormwater filter media). The objective of this review is to provide a detailed examination into the engineering properties and potential uses of biochar as an engineered material for environmental remediation. Biochar, due its highly variable and customizable surface chemistry, offers great potential in a variety of engineering applications, some of which have yet to be discovered.

Physical and chemical characterization of waste wood derived biochars.

Biochar, a solid byproduct generated during waste biomass pyrolysis or gasification in the absence (or near-absence) of oxygen, has recently garnered interest for both agricultural and environmental management purposes owing to its unique physicochemical properties. Favorable properties of biochar include its high surface area and porosity, and ability to adsorb a variety of compounds, including nutrients, organic contaminants, and some gases. Physical and chemical properties of biochars are dictated by the feedstock and production processes (pyrolysis or gasification temperature, conversion technology and pre- and post-treatment processes, if any), which vary widely across commercially produced biochars. In this study, several commercially available biochars derived from waste wood are characterized for physical and chemical properties that can signify their relevant environmental applications. Parameters characterized include: physical properties (particle size distribution, specific gravity, density, porosity, surface area), hydraulic properties (hydraulic conductivity and water holding capacity), and chemical and electrochemical properties (organic matter and organic carbon contents, pH, oxidation-reduction potential and electrical conductivity, zeta potential, carbon, nitrogen and hydrogen (CHN) elemental composition, polycyclic aromatic hydrocarbons (PAHs), heavy metals, and leachable PAHs and heavy metals). A wide range of fixed carbon (0-47.8%), volatile matter (28-74.1%), and ash contents (1.5-65.7%) were observed among tested biochars. A high variability in surface area (0.1-155.1g/m(2)) and PAH and heavy metal contents of the solid phase among commercially available biochars was also observed (0.7-83 mg kg(-1)), underscoring the importance of pre-screening biochars prior to application. Production conditions appear to dictate PAH content--with the highest PAHs observed in biochar produced via fast pyrolysis and lowest among the gasification-produced biochars.

Enhanced microbial methane oxidation in landfill cover soil amended with biochar

AbstractBiochar amendment to landfill cover soil is proposed as an economical solution to reduce methane (CH4) emissions from landfills without gas-recovery systems or in conjunction with gas recovery for near-complete CH4 removal. In this study, column experiments were conducted to simulate the effects of biochar amendment to landfill cover soil and investigate whether biochar amendment can promote the growth of methanotrophic bacteria able to oxidize CH4 into carbon dioxide (CO2). Acrylic columns were packed with coarse gravel (gas-distribution layer) and then filled with either soil or 20% biochar/80% soil. The columns were fed humidified synthetic landfill gas (25% CH4:25% CO2:50% N2) continuously for 4 months. Sampling ports along the length of the column were used to collect gas samples for measurement of the CH4 and CO2 concentrations. Additional isotopic analysis (δ13C) and temperature profiles were also used to evaluate the extent of CH4 oxidation as a function of depth. The deoxyribonucleic acid...

High pH microbial ecosystems in a newly discovered, ephemeral, serpentinizing fluid seep at Yanartaş (Chimera), Turkey

Gas seeps emanating from Yanartaş (Chimera), Turkey, have been documented for thousands of years. Active serpentinization produces hydrogen and a range of carbon gases that may provide fuel for life. Here we report a newly discovered, ephemeral fluid seep emanating from a small gas vent at Yanartaş. Fluids and biofilms were sampled at the source and points downstream. We describe site conditions, and provide microbiological data in the form of enrichment cultures, Scanning electron microscopy (SEM), carbon and nitrogen isotopic composition of solids, and PCR screens of nitrogen cycle genes. Source fluids are pH 11.95, with a Ca:Mg of ~200, and sediments under the ignited gas seep measure 60°C. Collectively, these data suggest the fluid is the product of active serpentinization at depth. Source sediments are primarily calcite and alteration products (chlorite and montmorillonite). Downstream, biofilms are mixed with montmorillonite. SEM shows biofilms distributed homogeneously with carbonates. Organic carbon accounts for 60% of the total carbon at the source, decreasing downstream to <15% as inorganic carbon precipitates. δ13C ratios of the organic carbon fraction of solids are depleted (−25 to −28‰) relative to the carbonates (−11 to −20‰). We conclude that heterotrophic processes are dominant throughout the surface ecosystem, and carbon fixation may be key down channel. δ15N ratios ~3‰, and absence of nifH in extracted DNA suggest that nitrogen fixation is not occurring in sediments. However, the presence of narG and nirS at most locations and in enrichments indicates genomic potential for nitrate and nitrite reduction. This small seep with shallow run-off is likely ephemeral, but abundant preserved microterracettes in the outflow and the surrounding area suggest it has been present for some time. This site and others like it present an opportunity for investigations of preserved deep biosphere signatures, and subsurface-surface interactions.

Review of biological diagnostic tools and their applications in geoenvironmental engineering

Biological diagnostic tools are becoming an increasingly important aspect of geoenvironmental problems. Modern geoenvironmental professionals must be able to both understand and exploit biological processes for a variety of applications, ranging from contaminant biodegradation and removal to evaluation and monitoring of environmental quality in and around landfills and landfill cover systems. Advancements in genetics and environmental measurement have yielded a wealth of sophisticated tools to evaluate biological processes in soils, sediments and groundwater. Successful use of these tools requires a keen understanding of the limitations and advantages offered by each. This paper provides an overview of the currently available biological diagnostic tools with an emphasis on their application in geoenvironmental engineering. Limitations and unresolved challenges in successful applications of these tools are also discussed.

Evaluation of PAH and Metal Contents of Different Biochars for Use in Climate Change Mitigation Systems

Biochar, a solid byproduct generated during biomass pyrolysis or gasification in the absence (or near-absence) of oxygen, has recently garnered interest for both agricultural and environmental uses owing to its unique physical and chemical properties, such as its high surface area and porosity, and ability to adsorb a variety of compounds, including nutrients, organic contaminants, and some gases. This material is also considered ‘sustainable’ as it can be derived from agricultural wastes and is currently being investigated for carbon sequestration applications and as a soil cover amendment for reduced greenhouse gas emissions from landfills. Ongoing research in our laboratory has shown that biochar can enhance both methane adsorption and subsequent microbial oxidation in soils, making it a promising material to mitigate residual landfill emissions for which gas recovery is not economical or feasible. Physical and chemical properties of biochar are dictated by the feedstock and production conditions (i.e. temperature, conversion technology and post-treatment processes, if any), which vary widely across commercially produced biochars. In this study, several commercially available biochars are characterized for key physical and chemical properties relevant to the common uses of biochars in environmental applications, with special attention given to PAH and heavy metal content and leachability. A high variability in chemical composition, surface properties, and PAH and heavy metal contents among commercially available biochars was observed, underscoring the importance of pre-screening biochars for the presence of PAHs and heavy metals prior to selection as a landfill cover or soil amendment.

Effects of biochar-amendment to landfill cover soil on microbial methane oxidation: Initial results

Biochar amendments to landfill covers have been proposed as an economic solution to reduce methane emissions from landfills without gas recovery systems, or in conjunction with gas recovery for near-complete methane removal in new landfills. In this study, column experiments are used to simulate the effects of biochar amendments to landfill cover soils for methane mitigation. Acrylic columns were packed with coarse gravel, and filled with either soil or 20% biochar/80% soil. Measurements of CH4, CO2 and temperature along the depth of the column allowed the determination of gas profiles and oxidation efficiencies over the course of the experiment. DNA-based assays and isotopic measurements (δ 13 CH4 and δ 13 CO2 (‰)) were used to infer the extent of microbial oxidation and to evaluate the distribution of methanotrophs within each column. qPCR targeting the pmoA (particulate methane monoxygenase) gene indicate a higher number of methanotrophs exist in the biochar- amended column, supporting the observed higher rates of methane oxidation. Batch incubation experiments were conducted to determine Michaelis-Menten kinetic parameters for methane oxidation. Initial results indicate that biochar is effective in increasing methanotrophic activity and promoting methane oxidation.

Microbial Abundance and Activity in Biochar-Amended Landfill Cover Soils: Evidence from Large-Scale Column and Field Experiments

AbstractField and laboratory studies were conducted to evaluate the impact of biochar amendment on methane oxidation rates and microbial communities in landfill cover soils. Deoxyribonucleic acid (...

Phytoremediation of heavy metals and PAHs at slag fill site: three-year field-scale investigation

Abstract Big Marsh is a 121-hectares site, representative of many other sites in the Calumet region (near Chicago, IL, USA), which has been significantly altered by the steel industry and decades of legal and illegal dumping and industrial filling. The slag-containing soil at the site has been found to be contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Due to the large size of the site to be remedied, and variable distribution of the contaminants throughout the shallow depth at slightly above the risk-based levels, phytoremediation is considered as a green and sustainable remedial option. The objective of this work was to investigate the use of phytoremediation in a three-year field-scale study, specifically determine plant survival and the fate of PAHs and heavy metals in soil and plant roots and stems. Replicate test plots were prepared by laying a thin layer of compost at the ground surface and then tilling and homogenizing the slag–soil fill to a depth of approximately 0.3 m. Nine native and restoration plant species were selected and planted at the site, and their survival and growth were monitored and fate of contaminants in soil and plants were also monitored for three growing seasons. Sequential extraction procedure was performed to determine the fractionation of the heavy metals in soils before and after planting. The results showed a decrease in PAHs concentrations in the soil, probably due to enhanced biodegradation within rhizosphere. No significant decrease in heavy metal concentrations in soil was found, but they were found to be immobilized. Contaminant concentrations were found below detection limits in the plant roots and shoots samples, demonstrating insignificant uptake by the plants. Overall, selected native grasses in combination with compost amendment to the soil proved to be able to survive under the harsh site slag fill conditions, helping to degrade or immobilize the contaminants and reducing the risk of the contaminants to public and the environment.

Biochar-amended soil cover for microbial methane oxidation: Effect of biochar amendment ratio and cover profile

AbstractA long-term soil column study was carried out to investigate the methane (CH4) removal capacity of landfill cover soil and biochar-amended cover soil under simulated landfill cover conditio...