Bala Yamini Sadasivam

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.

Landfill methane oxidation in soil and bio-based cover systems: a review

Mitigation of landfill gases has gained the utmost importance in recent years due to the increase in methane (CH4) emissions from landfills worldwide. This, in turn, can contribute to global warming and climatic changes. The concept of microbially mediated methane oxidation in landfill covers by using methanotrophic microorganisms has been widely adopted as a method to counter the rise in methane emissions. Traditionally, landfill soil covers were used to achieve methane oxidation, thereby reducing methane emissions. Meanwhile, the continual rise of CH4 emissions from landfills and the significant need to and importance of developing a better technology has led researchers to explore different methods to enhance microbial methane oxidation by using organic rich materials such as compost in landfill covers. The development and field application of such bio-based systems, explored by various researches worldwide, eventually led to more widely accepted and better performing cover systems capable of reducing CH4 emissions from landfills. However, the long-term performance of bio-based cover systems were found to be negatively affected by factors such as the material’s ability to self-degrade, causing CH4 to be generated rather than oxidized as well as the greater potential for forming pore-clogging exopolymeric substances. In order to design an effective cover system for landfills, it is essential to have a thorough understanding of the concepts incorporated into methodologies currently in favor along with their pros and cons. This review summarizes previous laboratory and field-scale studies conducted on various soil and bio-based cover systems, along with the modeling mechanisms adopted for quantifying CH4 oxidation rates. Finally, several issues and challenges in developing effective and economical soil and bio-based cover systems are presented.

Review of the effects of biochar amendment on soil properties and carbon sequestration

AbstractBiochar is one of a series of materials referred to as black carbon because it is produced by thermochemical transformation of the original biomass material under a variety of conditions. The objectives of this paper are to summarize the characteristics of biochar created from different feedstocks and identify the potential of biochar to maintain soil quality and sequester carbon. Biochar properties were analyzed in context to the biochar sources using indicators of their elemental compositions, pH, surface area, and cation exchange capacity. Application effects were also compared to evaluate the potential of biochar as a soil amendment and carbon capture agent on the basis of pot and field study results. Biochar performed well in terms of the improvement of soil pH and organic carbon, the stability of soil fertilizer generated from its large surface areas and cation exchange capacities. In general, the use of biochar proved to be an appropriate strategy for carbon neutralization resulting from ca...

Adsorption and transport of methane in biochars derived from waste wood.

Mitigation of landfill gas (LFG) is among the critical aspects considered in the design of a landfill cover in order to prevent atmospheric pollution and control global warming. In general, landfill cover soils can partially remove methane (CH4) through microbial oxidation carried out by methanotrophic bacteria present within them. The oxidizing capacity of these landfill cover soils may be improved by adding organic materials, such as biochar, which increase adsorption and promote subsequent or simultaneous oxidation of CH4. In this study, seven wood-derived biochars and granular activated carbon (GAC) were characterized for their CH4 adsorption capacity by conducting batch and small-scale column studies. The effects of influential factors, such as exposed CH4 concentration, moisture content and temperature on CH4 adsorption onto biochars, were determined. The CH4 transport was modeled using a 1-D advection-dispersion equation that accounted for sorption. The effects of LFG inflow rates and moisture content on the combined adsorption and transport properties of biochars were determined. The maximum CH4 adsorption capacity of GAC (3.21mol/kg) was significantly higher than that of the biochars (0.05-0.9mol/kg). The CH4 gas dispersion coefficients for all of the biochars ranged from 1×10(-3) to 3×10(-3)m(2)s(-1). The presence of moisture significantly suppressed the extent of methane adsorption onto the biochars and caused the methane to break through within shorter periods of time. Overall, certain biochar types have a high potential to enhance CH4 adsorption and transport properties when used as a cover material in landfills. However, field-scale studies need to be conducted in order to evaluate the performance of biochar-based cover system under a more dynamic field condition that captures the effect of seasonal and temporal changes.

Social Sustainability Evaluation Matrix (SSEM) to quantify social aspects of sustainable remediation

Sustainability analysis, or triple bottom line analysis, is increasingly recognized as a holistic approach when all the three pillars of sustainability (environmental, economic and social aspects) are equally incorporated into the decision-making process of a project. Currently, the tools for assessing the environmental and economic impacts are well established. On the contrary, the development of a quantitative tool to assess the social impacts has been particularly challenging because a multitude of subjective factors may vary among social entities depending upon the type of project assessed. In this study, a new tool called Social Sustainability Evaluation Matrix (SSEM) is developed and applied to two environmental remediation project sites. In both cases, remedial options were previously identified and assessed based on environmental and economic aspects. SSEM is an Excel-based tool comprising four social dimensions: (1) socio-individual, (2) socio-institutional, (3) socio-economic, and (4) socio-environmental. Under each dimension, several key areas are identified, and a scoring system is devised to quantify the extent of resulting social impacts. Scores for the identified key areas are summed under each social dimension, and a comparative assessment is performed to allow for more informed decisions about remedy selection, design, implementation, and mitigation as necessary. Overall, SSEM was found to be quite beneficial in assessing social sustainability of the selected remedial options in this study; however, it is important to incorporate an objective basis to the highest degree practicable. Also, when negative, substantive impacts are identified, mitigation efforts should be made to minimize or avoid the impact.

Influence of Physico-Chemical Properties of Different Biochars on Landfill Methane Adsorption

Landfill cover systems can be tailored to achieve effective methane adsorption as well as oxidation by adding organic materials such as biochars. In this study, a comprehensive investigation is performed to determine the influence of different physico-chemical properties of biochars on their respective methane adsorption characteristics so as to aid the selection of suitable biochar types for field application. Seven different types of wood-based biochars were characterized for their methane adsorption as well as physico-chemical properties. The experimental maximum adsorption capacity values for the biochars ranged between 0.04 and 0.18 mol/Kg. Overall, the methane adsorption capacity of biochars specific to this study increased with increasing porosity and surface area and decreased with increasing particle size, carbon content (total and fixed) and moisture content. Selected biochars are found to have ability to increase the adsorptive capacity of methane when used as a cover soil amendment.

Engineering properties of waste wood-derived biochars and biochar-amended soils

The application of biochars or biochar-amended soils in engineered systems (e.g. landfill biocover and in-ground filtration system) is contingent upon specific properties such as compressibility and shear strength that define their structural stability during and after construction under expected loading conditions. In this study, seven different types of waste wood-derived biochars were tested for their compressibility and shear strength properties. In addition, selected biochar-amended soils were tested. Compressibility testing was performed using one-dimensional compression testing apparatus, and shear strength testing was performed using direct shear testing apparatus. Biochars and biochar-amended soils were tested under dry and moist conditions. The results of compression testing were used to calculate constrained modulus and that of shear strength testing were used to calculate shear strength parameters (cohesion and angle of internal friction). The constrained modulus and shear strength parameters were correlated with the physicochemical properties of biochars or biochar-amended soils to develop relationships that can aid in the selection of suitable biochars or biochar-amended soils for engineering applications. Overall, this study provided critical engineering properties needed for the analysis and design of engineered systems using biochars or biochar-amended soils.

Quantifying the Effects of Moisture Content on Transport and Adsorption of Methane through Biochar in Landfills

This study was aimed at investigating the effects of moisture content (MC) on the methane transport and adsorption through wood-pellet biochar (CE- WP2) and comparing those results with that of a more conventional adsorbent, granular activated carbon (GAC). Laboratory column adsorption tests were conducted under dry and two levels of moisture content at three different landfill gas inflow rates. The breakthrough curves from column studies were modeled using the 1-D advection-diffusion equation by accounting for both the transport and adsorption processes affecting the system under different levels of MC. The presence of moisture negatively affects the methane adsorption onto both the materials with more pronounced influence in the case of GAC. The methane diffusion coefficients were modeled under dry and wet conditions for CE-WP2 and GAC. Results from this study show that the modeled methane diffusion coefficients for CE-WP2 were higher than that of GAC. Overall, this study provides critical information to design a novel biocover for landfills by incorporating biochar as a sustainable cover material to mitigate current CH4 emissions.

Sustainability Assessment of Subtitle D Cover versus Biocover for Methane Oxidation at Municipal Solid Waste Landfills

A life cycle analysis (LCA) was conducted in this study to evaluate the sustainability of using two different widely adopted cover system designs, the Subtitle D cover and the biocover. The two cover systems were designed according to RCRA regulations using a field validated, California Landfill Methane Inventory Model (CALMIM). The cover systems were designed for an IEPA-listed, active landfill site (Countryside Landfill Inc.) located in the Chicago Metropolitan area. Environmental sustainability analysis for the two cover system designs was performed using SimaPro (Version 7). Economic and social sustainability analysis was methodically performed for both the cover systems. Overall, this study showed that the biocover system is a more sustainable option when compared to the Subtitle D cover system by accounting for sustainability metrics involving the environmental, social and economical aspects.

Approaches to Selecting Sustainable Technologies for Remediation of Contaminated Sites: Case Studies

Conventional remediation technologies are designed and implemented with the aim of achieving reduction of contaminant concentrations to meet the remedial goals in a cost-effective and timely manner. On the contrary, green and sustainable remediation (GSR) is a holistic approach to remediation which helps reduce the overall environmental impact by weighing out different technically feasible remedial options and selecting the one with minimal impact. This paper provides in-depth information pertaining to the application of GSR at three different contaminated sites in Illinois, USA. All the three sites had varied contaminant characteristics and site-specific conditions for which different remedial options were evaluated. Environmental site assessment reports were reviewed, and the final recommendations for remedial action (RA) were made based on conducting a qualitative as well as quantitative comparison between technically feasible remedial options using available tools to quantify the sustainability metrics, such as Green Remediation Evaluation Matrix (GREM), Illinois Greener Cleanups Matrix, Sustainable Remediation Technology (SRTTM), and SiteWiseTM. Remedial Action Plans (RAPs) were developed by incorporating best management practices (BMPs), and the use of coupled-treatment techniques (remedial train) was proposed and designed for site-specific conditions along with detailed cost estimates and expected time frame to achieve the remedial goals. Long-term monitoring and maintenance plans were also included in the proposed RAPs.