Christopher M. Saffron

Structural characterization of alkaline hydrogen peroxide pretreated grasses exhibiting diverse lignin phenotypes

BackgroundFor cellulosic biofuels processes, suitable characterization of the lignin remaining within the cell wall and correlation of quantified properties of lignin to cell wall polysaccharide enzymatic deconstruction is underrepresented in the literature. This is particularly true for grasses which represent a number of promising bioenergy feedstocks where quantification of grass lignins is particularly problematic due to the high fraction of p- hydroxycinnamates. The main focus of this work is to use grasses with a diverse range of lignin properties, and applying multiple lignin characterization platforms, attempt to correlate the differences in these lignin properties to the susceptibility to alkaline hydrogen peroxide (AHP) pretreatment and subsequent enzymatic deconstruction.ResultsWe were able to determine that the enzymatic hydrolysis of cellulose to to glucose (i.e. digestibility) of four grasses with relatively diverse lignin phenotypes could be correlated to total lignin content and the content of p-hydroxycinnamates, while S/G ratios did not appear to contribute to the enzymatic digestibility or delignification. The lignins of the brown midrib corn stovers tested were significantly more condensed than a typical commercial corn stover and a significant finding was that pretreatment with alkaline hydrogen peroxide increases the fraction of lignins involved in condensed linkages from 88–95% to ~99% for all the corn stovers tested, which is much more than has been reported in the literature for other pretreatments. This indicates significant scission of β-O-4 bonds by pretreatment and/or induction of lignin condensation reactions. The S/G ratios in grasses determined by analytical pyrolysis are significantly lower than values obtained using either thioacidolysis or 2DHSQC NMR due to presumed interference by ferulates.ConclusionsIt was found that grass cell wall polysaccharide hydrolysis by cellulolytic enzymes for grasses exhibiting a diversity of lignin structures and compositions could be linked to quantifiable changes in the composition of the cell wall and properties of the lignin including apparent content of the p-hydroxycinnamates while the limitations of S/G estimation in grasses is highlighted.

A mild approach for bio-oil stabilization and upgrading: electrocatalytic hydrogenation using ruthenium supported on activated carbon cloth

Electrocatalytic hydrogenation (ECH) offers a new approach for bio-oil stabilization (a.k.a. partial upgrading). Water-soluble bio-oil, obtained by aqueous extraction of the liquid product of biomass pyrolysis, was hydrogenated using ECH at room conditions. A new electrocatalyst, ruthenium supported on activated carbon cloth, was used as the catalytic cathode. After electrocatalytic hydrogenation, aldehydes and ketones were reduced to the corresponding alcohols or diols, forms less prone to condensation chemistry. Carbon recovery into the liquid product, important when making liquid fuels from biomass, was more than 80%, while less than 0.1 wt% of the water-soluble bio-oil formed solid precipitate. The stability of the ECH-treated water-soluble bio-oil was checked via an accelerated aging test followed by size exclusion chromatography analysis and viscometry. Besides stabilization of bio-oil for subsequent fuel production, hydrogen and valuable diols were produced during ECH. Strategies to optimize the energy efficiency of this approach by altering the cell design, modifying the catalyst and adjusting the reaction conditions were also explored.

Electrocatalytic upgrading of model lignin monomers with earth abundant metal electrodes

Guaiacol (2-methoxyphenol) and related lignin model monomers undergo electrocatalytic hydrogenolysis/hydrogenation (ECH) to cyclohexanol with RANEY® Nickel electrodes in aqueous solution. Aryl ether (C–O) bond cleavage is followed by reduction of the aromatic ring at ambient pressure and 75 °C. Related arene-OR cleavages occur at similar rates regardless of R-group size. Protons are supplied by anodic water oxidation on a stainless steel grid coated with cobalt-phosphate catalyst, inexpensively replacing the conventional platinum anode, and remaining viable in constant current electrolyses of up to 16 hours. The overall method addresses two key barriers to energy upgrading of low specific energy biomass into fuels and chemicals: deoxygenation and hydrogenation. By directly and simply coupling energy from renewable electricity into the chemical fuel cycle, ECH bypasses the complexity, capital costs and challenging conditions of classical H2 hydrotreating, and may help open the door to truly carbon-retentive displacement of fossil petroleum by renewables.

Integration of decentralized torrefaction with centralized catalytic pyrolysis to produce green aromatics from coffee grounds

The aim of this work was to integrate decentralized torrefaction with centralized catalytic pyrolysis to convert coffee grounds into the green aromatic precursors of terephthalic acid, namely benzene, toluene, ethylbenzene, and xylenes (BTEX). An economic analysis of this bioproduct system was conducted to examine BTEX yields, biomass costs and their sensitivities. Model predictions were verified experimentally using pyrolysis GC/MS to quantify BTEX yields for raw and torrefied biomass. The production cost was minimized when the torrefier temperature and residence time were 239°C and 34min, respectively. This optimization study found conditions that justify torrefaction as a pretreatment for making BTEX, provided that starting feedstock costs are below

Thermochemical Conversion of Palm Kernel Shell (PKS) to Bio-Energy

58 per tonne.

Engineering the Bioeconomy

Palm kernel shell is an important by-product of oil palm production. It is often neglected and handled as waste in the product mix of palm oil production. One kilogram of PKS was pyrolized in a bench scale pyrolysis screw reactor at temperature range of 450°C to 500°C in 10mins. The process yielded 61 wt%, 24.5 wt% and 14 wt% bio-oil, bio-char and non condensable flammable gas respectively. Palm Kernel shell is relatively abundant in the tropical West Africa and Asia. Until recently PKS is commonly combusted for cooking purposes which contributes to total GHG emission. The products were characterized by determining their physical and chemical properties using standard methods. The thermochemical conversion shows that there is 29% and 26% increase in the higher heating values and lower heating values (on dry basis) respectively, of the bio-oil obtained when compared with the energy values of the original PKS. Similarly, the HHV of the bio-char is 62% higher than that of the original PKS. In addition the results of the GC-MS analysis of the bio-oil show that it contains useful chemicals that can be harnessed for industrial applications. The ash content of the bio-oil and the original PKS sample are 0.37% and 8.68% respectively, on as received, while the results of the elemental analyses show that there is < 0.08% and < 0.05% sulphur content of the PKS and its bio-oil respectively. This makes the products an environmentally suitable fuels for transportation and power generation. The results of this work show that the products compare well with those of other woody samples used for commercial pyrolysis process. PKS bio-char possesses the potential to be used as industrial absorbent in water treatment and process technology. Hence, PKS can be harnessed as potential future source of bio-energy and Activated carbon, and as such should be given adequate attention as a major product of oil palm processing for sustainable economic development of emerging economies.Copyright

Resources from Wastes: Benefits and Complexity

The bioeconomy is most associated with renewable bio-based fuels for meeting transportation and stationary energy needs. At the federal level, the U.S. Energy Independence and Security Act of 2007 set a target of 36 billion gallons of bio-based fuel production by the year 2022. Of this, 16 billion gallons are to be produced from nonstarch sources of sugars such as agricultural and forestry biomass. State governments are also participating as over half have enacted renewable electricity standards that promote the use of bio-based energy sources. Market forces are beginning to drive the bioeconomy as the private sector becomes increasingly aware of the beneficial uses of by-products from biofuel production, as animal feeds, neutraceuticals, pharmaceuticals, and other valuable chemicals. Engineering a sustainable and efficient bioeconomy requires a monumental research effort. Systems analysis, including the tools of life-cycle assessment and economics, is needed to transparently quantify the economic, environmental, and social costs as well as benefits of adopting bio-based supply chains and technologies. Profitability is now computed not only from the sale of products and by-products but also by carbon and renewable energy credits. Considering environmental and social qualitative impacts, both positive and negative, is essential to avoid unintended consequences. Research in agriculture, silviculture, and biomass conversion is actively being pursued to support the burgeoning bioeconomy. Biomass sources such as energy crops and cellulosic residues that can be economically and sustainably converted into bio-based products are being developed. Traditional agricultural research is again needed, not on food production, but instead on growing,

Mild electrocatalytic hydrogenation and hydrodeoxygenation of bio-oil derived phenolic compounds using ruthenium supported on activated carbon cloth

AbstractThe United States produces significant quantities of waste biomass from wastewater treatment, food production, food services, and landscape and wood debris. This waste contains essential re...