Philip H. Steele

Modeling and evaluation of chromium remediation from water using low cost bio-char, a green adsorbent

Oak wood and oak bark chars were obtained from fast pyrolysis in an auger reactor at 400-450 °C. These chars were characterized and utilized for Cr(VI) remediation from water. Batch sorption studies were performed at different temperatures, pH values and solid to liquid ratios. Maximum chromium was removed at pH 2.0. A kinetic study yielded an optimum equilibrium time of 48 h with an adsorbent dose of 10 g/L. Sorption studies were conducted over a concentration range of 1-100mg/L. Cr(VI) removal increased with an increase in temperature (Q(Oak wood)(°): 25 °C = 3.03 mg/g; 35 °C = 4.08 mg/g; 45 °C = 4.93 mg/g and Q(Oakbark)(°): 25 °C = 4.62 mg/g; 35 °C = 7.43 mg/g; 45 °C = 7.51 mg/g). More chromium was removed with oak bark than oak wood. The char performances were evaluated using the Freundlich, Langmuir, Redlich-Peterson, Toth, Radke and Sips adsorption isotherm models. The Sips adsorption isotherm model best fits the experimental data [high regression (R(2)) coefficients]. The overall kinetic data was satisfactorily explained by a pseudo second order rate expression. Water penetrated into the char walls exposing Cr(VI) to additional adsorption sites that were not on the surfaces of dry char pores. It is remarkable that oak chars (S(BET): 1-3m(2)g(-1)) can remove similar amounts of Cr(VI) as activated carbon (S(BET): ∼ 1000 m(2)g(-1)). Thus, byproduct chars from bio-oil production might be used as inexpensive adsorbents for water purification. Char samples were successfully used for chromium remediation from contaminated surface water with dissolved interfering ions.

Lead sorptive removal using magnetic and nonmagnetic fast pyrolysis energy cane biochars.

Energy cane biochar (ECBC) was prepared in a 72 s fast pyrolysis at 425 °C in an auger-fed reactor and ground into 250-600 μm diameter particles. This biochar was magnetized by fusing an iron oxide phase to the particles by mixing aqueous biochar suspensions with aqueous Fe(3+)/Fe(2+) solutions, followed by NaOH treatment (MECBC). These biochars were characterized by Raman, FT-IR, X-ray, SEM, SEM-EDX, TEM, EDXRF, pHzpc, elemental analyses, S(BET), and magnetic moment determinations. The S(BET) of energy cane biochar was negligible and increased to 37.13 m(2)/g after Fe(3+)/Fe(2+)/NaOH magnetization. The dry biochar contains 18.4% oxygen. This allows swelling in water and permits sorption inside the solid as well as on its pore surfaces, leading to high capacities at low surface areas. Maximum lead removal occurred at pH 4-5. Sorption isotherms exhibited increasing lead removal (Q(0), mg/g) as temperature increased for nonmagnetic [Q(0)(25 °C)=45.70; Q(0)(35 °C)=52.01 and Q(0)(45 °C)=69.37] and magnetic [Q(0)(25 °C)=40.56; Q(0)(35 °C)=51.17 and Q(0)(45 °C)=51.75] biochars. Second order kinetics best fit the lead removal data. Furthermore, magnetic energy cane biochar was easily manipulated by low external magnetic field, thereby, allowing its easy recovery for further recycling and replacement from water. ECBC and MECBC were also successfully applied for Pb(2+) removal from contaminated ground water. Therefore, both chars can be used as potential green low cost sorbents for lead remediation to replace commercial activated carbon.

Life-Cycle Assessment of Pyrolysis Bio-Oil Production*

As part of the Consortium for Research on Renewable Industrial Materials’ Phase I life-cycle assessments of biofuels, lifecycle inventory burdens from the production of bio-oil were developed and compared with measures for residual fuel oil. Bio-oil feedstock was produced using whole southern pine (Pinus taeda) trees, chipped, and converted into bio-oil by fast pyrolysis. Input parameters and mass and energy balances were derived with Aspen. Mass and energy balances were input to SimaPro to determine the environmental performance of bio-oil compared with residual fuel oil as a heating fuel. Equivalent functional units of 1 MJ were used for demonstrating environmental preference in impact categories, such as fossil fuel use and global warming potential. Results showed near carbon neutrality of the bio-oil. Substituting bio-oil for residual fuel oil, based on the relative carbon emissions of the two fuels, estimated a reduction in CO2 emissions by 0.075 kg CO2 per MJ of fuel combustion or a 70 percent reduction in emission over residual fuel oil. The bio-oil production life-cycle stage consumed 92 percent of the total cradle-to-grave energy requirements, while feedstock collection, preparation, and transportation consumed 4 percent each. This model provides a framework to better understand the major factors affecting greenhouse gas emissions related to bio-oil production and conversion to boiler fuel during fast pyrolysis. This report has been produced as part of the Consortium for Research on Renewable Industrial Materials (CORRIM) Phase I reports on the life-cycle inventory (LCI) and life-cycle impact assessment (LCIA) studies of biofuels. CORRIM’s goal is to provide a database of information for quantifying the environmental impacts and economic costs of biofuels from woody biomass through the stages of collection, fuel conversion, and combustion in the United States. Life-cycle assessment (LCA) has evolved as an internationally accepted way to analyze complex impacts and outputs of a product and the corresponding effects on the environment. An LCA can provide the most comprehensive method to assess net carbon emissions and their associated impacts for fossil and biofuels evaluated under similar uses. The environmental outcomes of an LCA can accurately target the source of impacts, including where, when, and how they occur throughout a product’s life. The LCA process can provide characteristics such as global warming potential (GWP) and fossil fuel use that can be useful on a regional, national, or global scale. Outcomes from LCAs can be used to suggest more ‘‘environmentally friendly’’ products or sustainable production methods and may also provide insights regarding raw material conservation and emissions and waste output reduction. LCIA aggregates the inventory data and classifies them into the type of environmental impact to which they contribute, for example, GWP. Comparisons of the emission outputs of bio-oil with a relevant fossil fuel

Rapid conversion of cellulose to 5-hydroxymethylfurfural using single and combined metal chloride catalysts in ionic liquid

Abstract Direct conversion of cellulose into 5-hydroxymethylfurfural (HMF) was performed by using single or combined metal chloride catalysts in 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) ionic liquid. Our study demonstrated formation of 2-furyl hydroxymethyl ketone (FHMK), and furfural (FF) simultaneously with the formation of HMF. Various reaction parameters were addressed to optimize yields of furan derivatives produced from cellulose by varying reaction temperature, time, and the type of metal chloride catalyst. Catalytic reaction by using FeCl 3 resulted in 59.9% total yield of furan derivatives (HMF, FHMK, and FF) from cellulose. CrCl 3 was the most effective catalyst for selective conversion of cellulose into HMF (35.6%) with less concentrations of FHMK, and FF. Improving the yields of furans produced from cellulose could be achieved via reactions catalyzed by different combinations of two metal chlorides. Further optimization was carried out to produce total furans yield 75.9% by using FeCl 3 /CuCl 2 combination. CrCl 3 /CuCl 2 was the most selective combination to convert cellulose into HMF (39.9%) with total yield (63.8%) of furans produced from the reaction. The temperature and time of the catalytic reaction played an important role in cellulose conversion, and the yields of products. Increasing the reaction temperature could enhance the cellulose conversion and HMF yield for short reaction time intervals (5–20 min).

Comparing Life-Cycle Carbon and Energy Impacts for Biofuel, Wood Product, and Forest Management Alternatives*

The different uses of wood result in a hierarchy of carbon and energy impacts that can be characterized by their efficiency in displacing carbon emissions and/or in displacing fossil energy imports, both being current national objectives. When waste wood is used for biofuels (forest or mill residuals and thinnings) fossil fuels and their emissions are reduced without significant land use changes. Short rotation woody crops can increase yields and management efficiencies by using currently underused land. Wood products and biofuels are coproducts of sustainable forest management, along with the other values forests provide, such as clean air, water, and habitat. Producing multiple coproducts with different uses that result in different values complicates carbon mitigation accounting. It is important to understand how the life-cycle implications of managing our forests and using the wood coming from our forests impacts national energy and carbon emission objectives and other forest values. A series of articles published in this issue of the Forest Products Journal reports on the life-cycle implications of producing ethanol by gasification or fermentation and producing bio-oil by pyrolysis and feedstock collection from forest residuals, thinnings, and short rotation woody crops. These are evaluated and compared with other forest product uses. Background information is provided on existing life-cycle data and methods to evaluate prospective new processes and wood uses. Alternative management, processing, and collection methods are evaluated for their different efficiencies in contributing to national objectives.

Microwave Pyrolysis of Corn Cob and Characteristics of the Pyrolytic Chars

Abstract Microwave pyrolysis is a new process for converting biomass to bio-oil, syngas, and solid char. In this study, pyrolysis of corn cob was performed in an inert environment at atmospheric pressure and temperatures ranging from 300 to 600°C. The aim of this work was to study the effect of pyrolysis conditions on the characteristics of the solid char residue. The char was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, elemental analyzer, BET surface area analysis, and inductive coupled plasma. The char yield from pyrolysis decreased significantly to 23% with an increase in temperature to 600°C. SEM analysis indicated that pyrolysis of corn cob led to a stepwise accumulation of inorganic matter onto the exposed surface, and some organic matter melted, resulting in the formation of hollow cavities by the evolving volatiles. Fourier transform infrared spectroscopy results showed a continuous decrease in the intensity of the hydroxyl group stretch with temperature and the aromatic group to be at maximum at 600°C. Elemental analysis indicated both H/C and O/C ratio decreased continuously with increasing temperature to 450°C then became constant at higher temperatures.

Optimization of hot-compressed water pretreatment of bagasse and characterization of extracted hemicelluloses

Developing optimum treatment and separation procedures for hemicellulose components of lignocellulosic biomass could be useful in ethanol fermentation processes and obtaining pure hemicelluloses as biopolymers. Sugarcane bagasse analyses indicate that xylose is the major hemicellulose component constituting 17.7% of dry bagasse weight. In this study the effects of treatment conditions such as time, temperature and pressure on the yields of extracted hemicelluloses were studied. The optimum conditions were achieved at 180 °C for 30 min and 1 MPa pressure, with the yield of xylose reaching to 85% and the concentrations of sugar degradation products such as HMF and furfural remaining minimal at 0.95 and 0.07 g/L, respectively. Further, isolation of hemicelluloses from extracted hemicelluloses solutions was performed using Alfa Laval M20 membrane filtration system in two steps: (1) concentration of high molar mass hemicelluloses by ultrafiltration; and (2) separation of low molar mass hemicelluloses and oligomeric sugars by nanofiltration. The isolated hemicelluloses with the optimum pretreatment conditions were characterized by FT-IR and (13)C NMR techniques, resulting in agreement with typical spectra of xylan-type hemicelluloses.

Inhibitors removal from bio-oil aqueous fraction for increased ethanol production

Utilization of 1,6-anhydro-β-d-glucopyranose (levoglucosan) present (11% w/v) in the water fraction of bio-oil for ethanol production will facilitate improvement in comprehensive utilization of total carbon in biomass. One of the major challenges for conversion of anhydrous sugars from the bio-oil water fraction to bio-ethanol is the presence of inhibitory compounds that slow or impede the microbial fermentation process. Removal of inhibitory compounds was first approached by n-butanol extraction. Optimal ratio of n-butanol and bio-oil water fraction was 1.8:1. Removal of dissolved n-butanol was completed by evaporation. Concentration of sugars in the bio-oil water fraction was performed by membrane filtration and freeze drying. Fermentability of the pyrolytic sugars was tested by fermentation of hydrolyzed sugars with Saccharomyces pastorianus lager yeast. The yield of ethanol produced from pyrolytic sugars in the bio-oil water fraction reached a maximum of 98% of the theoretical yield.

Carbon Emission Reduction Impacts from Alternative Biofuels

Abstract The heightened interest in biofuels addresses the national objectives of reducing carbon emissions as well as reducing dependence on foreign fossil fuels. Using life-cycle analysis to evaluate alternative uses of wood including both products and fuels reveals a hierarchy of carbon and energy impacts characterized by their efficiency in reducing carbon emissions and/or in displacing fossil energy imports. Life-cycle comparisons are developed for biofuel feedstocks (mill and forest residuals, thinnings, and short rotation woody crops) with bioprocessing (pyrolysis, gasification, and fermentation) to produce liquid fuels and for using the feedstock for pellets and heat for drying solid wood products, all of which displace fossil fuels and fossil fuel–intensive products. Fossil carbon emissions from lignocellulosic biofuels are substantially lower than emissions from conventional gasoline. While using wood to displace fossil fuel–intensive materials (such as for steel floor joists) is much more effec...

Microwave Pyrolysis of Corn Stover

This study investigated microwave pyrolysis of corn stover under different conditions. The process yielded bio-oil, gas, and solid charcoal residue. Under experimental conditions, a power input level above 300 W was necessary to initiate thermal pyrolysis of a 50 g sample of corn stover. The yields of gas and bio-oil increased to 46.9 wt % and 30.2 wt %, respectively, when microwave input power increased from 300 to 900 W. A higher power input also favored gas production. Adding 1 wt % pyrolytic charcoal residue to the pyrolysis of corn stover increased the bio-oil and gas yields, particularly the bio-oil yield. Addition of NaOH to the pyrolysis of corn stover as catalyst increased the gas yield greatly. The chemical profiles of the gas and bio-oils were also determined using GC and GC-MS, respectively. This study demonstrated that microwave pyrolysis can be optimized to produce valuable gas and liquid bio-fuel.