Jillian L. Goldfarb

Impact of blend ratio on the co-firing of a commercial torrefied biomass and coal via analysis of oxidation kinetics

Incorporation of torrefied biomass into coal-fired power plants could potentially lower the SOx and net CO2 emissions resulting from electricity generation. However, concerns over lower heating values and slightly higher ash content of torrefied biomass suggest that blending it with coal in industrial boilers may be preferable to complete fuel transition. By studying the oxidation kinetics of coal-torrefied biomass blends in a thermogravimetric analyzer at a heating rate of 100°C/min, we find an additive nature among the fuels for peak mass loss rates and enthalpies of combustion. The activation energy required to initiate decomposition decreases from 132.6 to 77.6 kJ/mol as the torrefied biomass increases from 0 to 100 wt%, with a sharp decrease between 0 and 40 wt%. Data suggest that incorporation of torrefied biomass into coal-fired boilers is dependent on the ability to sacrifice heating value for the lower emissions of SOx and net CO2 garnered using bio-coal.

Vapor Pressures and Thermodynamics of Oxygen-Containing Polycyclic Aromatic Hydrocarbons Measured Using Knudsen Effusion

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (OPAHs) are ubiquitous environmental pollutants resulting from the incomplete combustion of coal and fossil fuels. Their vapor pressures are key thermodynamic data essential for modeling fate and transport within the environment. The present study involved nine PAHs containing oxygen heteroatoms, including aldehyde, carboxyl and nitro groups, specifically: 2-nitrofluorene; 9-fluorenecarboxylic acid; 2-fluorenecarboxaldehyde; 2-anthracenecarboxylic acid; 9-anthracenecarboxylic acid; 9-anthraldehyde; 1-nitropyrene; 1-pyrenecarboxaldehyde and 1-bromo-2-naphthoic acid. The vapor pressures of these compounds, with molecular weights ranging from 194 to 251 grams per mole, were measured using the isothermal Knudsen effusion technique in the temperature range of 329 to 421. The corresponding enthalpies of sublimation, calculated via the Clausius-Clapeyron equation, are compared to parent, non-oxygenated PAH compound data to determine the effect of the addition of these oxygen-containing heteroatoms. As expected, the addition of –CHO,–COOH, and –NO2 groups onto these PAHs increases the enthalpy of sublimation and decreases the vapor pressure as compared to the parent PAH; the position of substitution also plays a significant role in determining the vapor pressure of these OPAHs.

An integrated biorefinery concept for olive mill waste management: supercritical CO2 extraction and energy recovery

Commercial production of olive oil generates four times the amount of waste as it does oil, along with a number of environmental issues. We propose an integrated biorefinery concept for the management of pomace, i.e. solid Olive Mill Waste (OMW), that utilizes supercritical carbon dioxide (SCO2), coupled with a polar co-solvent (Ethanol), for extracting value-added polyphenols and mono/poly-unsaturated fatty acids (MUFA/PUFA), followed by thermochemical (oxidation or pyrolysis) recovery of energy, biofuels and materials. The SCO2 + EtOH extraction recovered 77.6 g of freeze-dried extract per kg of raw OMW, with relatively high concentrations in polyphenols (10.9 g kg−1 of which 60.1% of di-hydroxytyrosol), PUFA (20 g kg−1), MUFA (601 g kg−1) and other valuable compounds, such as squalene (10 g kg−1). All these substances are of extreme interest in pharmaceutical and nutraceutical market, for their antioxidant, anti-cancer, functional, anti-bacterial and nutritional properties. The SCO2 + EtOH flux acted as physical/chemical carrier for over 85% of humidity, leaving the exhaust OMW almost dry, with evident advantages for downstream. Using nonisothermal thermogravimetric analysis, the apparent activation energies required to pyrolyze OMW to produce fuel and biochar ranged from 20 to 140 kJ mol−1 depending on heating ramp rate and temperature regime. BET analysis of unactivated biochars show increased (+25%) mesopore surface areas after SCO2 extractions (up to 500 m2 g−1). A more in-depth view on the proposed biorefinery is needed, to consider the overall energy balance, as well as possible market values of the obtained extract, and evaluate the real feasibility of the proposed concept.

Sustainable waste mitigation: biotemplated nanostructured ZnO for photocatalytic water treatment via extraction of biofuels from hydrothermal carbonization of banana stalk

Working at the food-energy-water nexus, we identified an abundant agricultural waste with little intrinsic value – banana stalk – that can be converted to biofuels via hydrothermal carbonization. However, to make biomass to biofuel conversions economically viable, we must identify value-added products to add to the biorefinery, such as materials for water treatment. Both the resulting hydrochar and raw biomass were biotemplated with zinc acetate to yield ZnO nanostructures with surface areas ∼20 m2 g−1. The zincite particles were able to degrade a model organic dye (methylene blue) from aqueous solution. Though both the raw biomass and hydrochar yielded particles with similar surface areas, the photocatalytic activity of the raw templated particles was superior. We believe this is due to a higher concentration of calcium (naturally present in the banana biomass) in the hydrochar relative to the raw biomass. The calcium produced calcite crystals in the biotemplated materials, which may hinder the ZnO photocatalytic activity. However, the CaO may be useful for removing heavy metals from water and catalyzing biofuel production.

Pyrolysis reaction models of waste tires: Application of Master-Plots method for energy conversion via devolatilization

Land applied disposal of waste tires has far-reaching environmental, economic, and human health consequences. Pyrolysis represents a potential waste management solution, whereby the solid carbonaceous residue is heated in the absence of oxygen to produce liquid and gaseous fuels, and a solid char. The design of an efficient conversion unit requires information on the reaction kinetics of pyrolysis. This work is the first to probe the appropriate reaction model of waste tire pyrolysis. The average activation energy of pyrolysis was determined via iso-conversional methods over a mass fraction conversion range between 0.20 and 0.80 to be 162.8±23.2kJmol-1. Using the Master Plots method, a reaction order of three was found to be the most suitable model to describe the pyrolytic decomposition. This suggests that the chemical reactions themselves (cracking, depolymerization, etc.), not diffusion or boundary layer interactions common with carbonaceous biomasses, are the rate-limiting steps in the pyrolytic decomposition of waste tires.

Models and Mechanisms to Explore the Global Oxidation Kinetics of Blends of feed corn stover and Illinois No. 6 Coal

Biomass-coal co-firing has the potential to reduce SOx and net CO2 emissions from coal-fired power plants.Given the heterogeneity of biomass and coal feed stocks, the oxidation kinetic behavior of such blends is not wellunderstood. In this investigation, we probe the applicability of a variety of kinetic models to describe the fast oxidationof feed corn stover, Illinois No. 6 coal, and their blends using thermogravimetric analyzer. We find that a first order reaction assumption (often referred to as the Arrhenius Equation), as well as three-dimensional diffusion reaction models offer the best fit to the data as measured through correlation coefficients, and return reasonably similar activation energies. Derivative thermogravimetric curves show that peak mass loss rates occur within ~30K of each other for each fuel and blend, though the peak mass loss rate is dependent on the specific fuel and blend. Evidenceof reaction synergism between the fuels in the blends, in the form of a non-additive activation energy predictionscheme, suggests that the biomass promotes decomposition of the coal at lower temperatures.

Invasive species or sustainable water filters? A student-led laboratory investigation into locally sourced biomass-based adsorbents for sustainable water treatment

Abstract Designing sustainable products requires a holistic consideration of issues at the Food-Energy-Water Nexus. One of the world’s greatest challenges is to insure clean water access for all inhabitants. Across the globe, communities often suffer from metal contamination in their water. We must develop low-cost, sustainable materials to treat this contamination, without putting undue stress on other systems. Biomass-based carbon adsorbents are often touted as one potential solution, but to be sustainable the biomass must be locally sourced, not grown on land that could be used to cultivate food, not require extensive water to grow, and not need undue amounts of energy to process. In this laboratory investigation, students were challenged to use a locally available, problematic biomass – phragmites, an invasive species in the Muddy River in Boston, Massachusetts – to develop a green adsorbent to remove metals from water. Specifically, students focused on the removal of manganese, as it is a local problem for several Massachusetts communities. Students activated the phragmites biomass using a room and low (40 °C) temperature KOH treatment, which opened the porous network of the reed to enable adsorption of Mn+2 upwards of 8 mg/g of biomass. In doing this experiment, students were exposed to the concept of adsorption, a separation process not often covered in the traditional chemistry curriculum. Students gained experience in performing adsorption isotherm experiments using atomic adsorption spectroscopy and UV–Vis spectrophotometry and learned to analyze data within adsorption isotherm models. Finally, students made connections between their laboratory data and adsorption theory, and how this data can be used to design greener materials to address environmental issues.

Building Public Support for Science Spending

While most Americans support scientific research, few favor an increase in federal investment. This opposition is driven in large part by misinformation about the actual level of governmental support for science. Employing an experiment embedded on a nationally representative survey, we find that most Americans significantly overestimate the share of the federal budget allocated to scientific research. Correcting this misperception significantly increases support for additional science spending. We find little evidence that subjects engage in motivated reasoning when confronted with this correction. Information about the low level of existing funding increased support for investment in science across partisan and ideological divides.