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Technologies for producing renewable fuels and chemicals rely on the production of stable intermediates. For thermochemical technologies, pyrolysis of biomass produces oils that must compromise between carbon yield and oil quality. Bio-oil extraction has largely focused on regular bio-oils (~ 33 wt% O) and partially deoxygenated oils (< 12 wt% O). Furthermore, it is desired to extract phenolics without direct distillation of bio-oils, which would enable extraction from the heaviest portion of bio-oil. Mid-level oxygen (MLO) bio-oils (16–25 wt% O) produced from switchgrass were characterized for their ability to separate into phenolic-rich fractions. Toluene-soluble portions of the oils underwent NaOH extraction to extract one-ring phenolics, while toluene-insoluble portions were fractionated with iso-propyl alcohol (IPA). While phenolic extraction proceeded without distillation (having been a prerequisite for partially deoxygenated bio-oils), the efficiency of extraction was less than optimal, owing to the presence of other oxygenated compounds in the hydrocarbon-rich fraction. Both IPA-insoluble and IPA-soluble fractions underwent solvent liquefaction reactions with base additives. While using water as a reaction medium produced greater concentrations of phenols than when using methanol, addition of sodium carbonate produced narrower product distributions of phenols and inhibited formation of benzenediols. [ABSTRACT FROM AUTHOR]

Utilization of lignin is among the most pressing problems for biorefineries that convert lignocellulosic biomass to fuels and chemicals. Recently "lignin-first" biomass fractionation has received increasing attention. In most biorefining concepts, carbohydrate portions of the biomass are separated, and their monomeric sugar components released, while the relatively chemically stable lignin rich byproduct remains underutilized. Conversely, in lignin-first processes, a one-pot fractionation and depolymerization is performed, leading to an oil rich in phenolic compounds and a cellulosic pulp. Usually, the pulp is considered as a fermentation feedstock to produce ethanol. Herein, the results of a study where various cellulosic pulps are tested for their potential to produce valuable products via pyrolysis processes, assessed via analytical pyrolysis (py-GC), are presented. Samples of herbaceous (switchgrass) and woody biomass (oak) were subjected to both an acid-catalyzed and a supported-metal-catalyzed reductive lignin-first depolymerization, and the pulps were compared. Fast pyrolysis of the pulps produced levoglucosan in yields of up to about 35 wt %. When normalized for the amount of biomass entering the entire process, performing the lignin-first reductive depolymerization resulted in 4.0–4.6 times the yield of levoglucosan than pyrolysis of raw biomass. Pulps derived from switchgrass were better feedstocks for levoglucosan production compared with pulps from oak, and pulps produced from metal-on-carbon catalyzed depolymerization produced more levoglucosan than those from acid-catalyzed depolymerization. Catalytic pyrolysis over HZSM-5 produced aromatic hydrocarbons from the pulps. In this case, the yields were similar from both feedstocks and catalyst types, suggesting that there is no advantage to lignin fractionation prior to zeolite-catalyzed catalytic pyrolysis for hydrocarbons. [ABSTRACT FROM AUTHOR]

As a dedicated bioenergy crop, switchgrass is a potential feedstock within the United States for biofuels production. It can be converted to energy dense bio-oil through fast pyrolysis. Biomass compositional differences can influence the conversion efficiency and bio-oil product yield and quality. In order to understand how improvements in bio-oil quality can be achieved by manipulation of biomass composition, differences in switchgrass biomass composition were evaluated for their impacts on fast pyrolysis product yield. Nine genotypes of switchgrass were grown on one prime and two marginal sites in New Jersey. The results show that biomass composition was affected by genotype, the environment, and genotype × environment interactions. Non-catalytic pyrolysis product yields were largely affected by genotypic differences. The most significant impacts on non-catalytic pyrolysis products were from cellulose content and K content in the biomass. It was found that non-methoxylated phenolics were mainly produced from the breakdown of levoglucosan in the presence of K. Mineral content in the biomass was highly variable by environment and soil variability across the sites examined. These differences in mineral content largely impacted product distribution of HZSM-5-catalyzed pyrolysis, showing that lower mineral uptake in the biomass was beneficial for the production of aromatic hydrocarbons. Significant genotypic and environmental effects among the pyrolysis products demonstrate that breeding for improvements in pyrolysis product yield is conceivable but that growing conditions and soil conditions must also be taken into consideration. [ABSTRACT FROM AUTHOR]

Pyrolysisof mixtures of agricultural plastic waste in the formof polyethylene hay bale covers (PE) (4–37%) and switchgrasswere investigated using the US Department of Agriculture’stail gas reactive pyrolysis (TGRP) process at different temperatures(400–570 °C). TGRP of switchgrass and plastic mixturessignificantly reduced the formation of waxy solids that are producedduring regular pyrolysis. Under an atmosphere of approximately 70%recycled tail gas, mostly noncondensable gases were produced alongwith highly deoxygenated and aromaticized pyrolysis oil. When theatmosphere was diluted further to a recycled tail gas concentrationof about 55%, higher yields of liquid product were achieved but withless deoxygenation. TGRP of low plastic mixtures (4–8%) producedoils with increased carbon and reduced oxygen content compared tothe fast pyrolysis of switchgrass alone. Noncondensable gas fractionscontaining high concentrations of H2, CO, ethylene, andother light hydrocarbons remained a significant portion of the productmixture at temperatures above 500 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Switchgrass and polyhydroxybutyrate (P3HB) were co-pyrolyzed. [•] Switchgrass pyrolysis oil, bio-char and crotonic acid were produced at 375°C. [•] Maximum crotonic acid yield was about 45% of input P3HB. [•] Crotonic acid may be present as both gas and aerosol in the pyrolysis vapor stream. [ABSTRACT FROM AUTHOR]

Thefate of inorganic species present in switchgrass during fluidizedbed catalytic pyrolysis over HZSM-5 catalysts was studied with emphasison their accumulation on the catalyst. Five catalytic pyrolysis experimentswere performed in two series, reusing the catalyst after each sample.Catalysts were regenerated from deactivation due to carbon depositsvia their removal by combustion at regular intervals. The fates ofseven inorganic elements were tracked: Ca, Cu, Fe, K, Mg, Na, andP. Potassium accumulated with the HZSM-5 catalyst the fastest whileiron was the metal that accumulated most preferentially on the catalysts,with about 42% of the Fe content of the biomass remaining with theHZSM-5. The total amount of these seven elements accumulated on HZSM-5in a linear fashion during continued use of the same catalyst sample.As the catalyst was exposed to more switchgrass and accumulated moreinorganic containments, its effectiveness at deoxygenating the pyrolysisliquids decreased. Selectivity for aromatic hydrocarbons also decreased,indicating that deactivation of HZSM-5 by exposure to inorganic contaminantsin biomass should be a consideration for biomass deoxygenation bycatalytic fast pyrolysis. [ABSTRACT FROM AUTHOR]

Abstract: Zeolites have been shown to effectively promote cracking reactions during pyrolysis resulting in highly deoxygenated and hydrocarbon-rich compounds and stable pyrolysis oil product. Py/GC–MS was employed to study the catalytic fast pyrolysis of lignocellulosic biomass samples comprising oak, corn cob, corn stover, and switchgrass, as well as the fractional components of biomass, i.e., cellulose, hemicellulose, and lignin. Quantitative values of condensable vapors and relative compositions of the pyrolytic products including non-condensable gases (NCG''s) and solid residues are presented to show how reaction products are affected by catalyst choice. While all catalysts decreased the oxygen-containing products in the condensable vapors, H-ZSM-5 was most effective at producing aromatic hydrocarbons from the pyrolytic vapors. We demonstrated how the Si/Al ratio of the catalysts plays a role in the deoxygenation of the vapors towards the pathway to aromatic hydrocarbons. [Copyright &y& Elsevier]

Abstract: A solid water insoluble material (WIS), commonly called pyrolytic lignin, can be isolated from biomass fast pyrolysis oils. Such material was isolated from the bio-oils produced from barley straw, barley hulls, switchgrass, soy straw and oak and then fully characterized. Analytical techniques employed in the characterization included elemental analysis, pyrolysis-GC/MS, Nuclear Magnetic Resonance Spectroscopy (NMR) and Gel Permeation Chromatography (GPC). The characterization showed that the materials were mostly but not entirely derived from the lignin fraction of the biomass; they were largely made up of aromatic rings, substituted with varying amounts of methoxy groups and linked by varying types of aliphatic linkers. The NMR identified different types of aliphatic linkers in the isolates, some previously reported and some newly proposed. GPC analysis showed that the dimers and trimers were the most common oligomeric size though units comprising a wide variety of molecular weights, some >1500Da, were detected. [Copyright &y& Elsevier]

Herbaceous bioenergy crops, including sorghum, switchgrass, and miscanthus, were evaluated for their potential as phytoremediators for the uptake of phosphorus in the Delmarva Peninsula and their subsequent conversion to biofuel intermediates (bio-oil) by fast pyrolysis using pyrolysis-gas chromatography/mass spectroscopy. Four cultivars of sorghum, five cultivars of switchgrass and one miscanthus ( Miscanthus × giganteus ) were grown in soils with two different levels of poultry manure (PM) applications. Little variation was seen in phosphorus uptake in the two different soils indicating that the levels of available phosphorus in the soil already saturated the uptake ability of the plants. However, all plants regardless of trial took up more phosphorus than that measured for the non- PM treated control. Sorghum accumulated greater levels of nutrients including phosphorus and potassium compared to switchgrass and miscanthus. The levels of these nutrients in the biomass did not have an effect on carbohydrate contents. However, the potential yield and composition of bio-oil from fast pyrolysis were affected by both agronomics and differences in mineral concentrations. [ABSTRACT FROM AUTHOR]

• For most scenarios, densifying biomass does not improve the economics. • Densification is economically advantageous when there is a high feedstock competition. • The plant size of a densification facility has a minimal impact on the overall economics. Biomass such as switchgrass can be converted to renewable gasoline and diesel (RGD) fuels via integrated fast pyrolysis and hydrodeoxygenation. However, the low bulk density of biomass feedstocks produces relatively high transportation costs, driven by the large volumes needed to supply biorefineries. Densification can reduce transportation volumes, and therefore transportation costs for bioenergy production. However, the additional costs of biomass densification, along with decreases in overall mass and energy yields, influence the overall economic performance of RGD production. This study investigated the techno-economic impacts of pelletizing, torrefying, or pyrolyzing the biomass at distributed facilities prior to upgrading the intermediates to RGD at a centralized facility. Eight scenarios were considered. When there is no feedstock competition, biomass densification at the distributed facility was shown to reduce the transportation cost by 20%–50%. However, the capital and operating costs required for densifying biomass increased the total cost of RGD production by 3%–35% compared to RGD made from non-densified biomass. The cost of making RGD from densified biomass was only reduced below the cost of making RGD from non-densified biomass for the case when the fraction of land surrounding the biorefinery facility allocated to the biomass cultivation is less than 0.25. This finding is attributed to the high cost of transporting non-densified biomass from a larger procurement radius. Sensitivity analysis indicated that RGD fuel yield, densification costs, project investment, and the rate of return all have significant impacts on the overall economics of RGD production. [ABSTRACT FROM AUTHOR]

The resource efficiency of biofuelproduction via biomass pyrolysisis evaluated using exergy as an assessment metric. Three feedstocks,important to various sectors of U.S. agriculture, switchgrass, forestresidue, and equine waste, are considered for conversion to bio-oil(pyrolysis oil) via fast pyrolysis, a process that has been identifiedas adaptable to on- or near-farm application. Biomass and biofuelproduction pathways are defined, material flows are determined, andexergy in- and outflows associated with biomass production and conversionare computed, including the depletion of exergy from its natural state(cumulative exergy demand, CExD). Sources of exergy depletion arequantified and categorized by energy carriers, e.g., electricity anddiesel fuel, and materials, e.g., fertilizer, as well as renewableand nonrenewable resources. Yields for biomass to bio-oil conversionby fast pyrolysis are determined experimentally. Breeding factors,a measure of exergy production (the ratio of the chemical exergy ofthe output product to process exergy inputs), are determined for theproduction of biomass and bio-oil. The quantification of exergy depletionfor process pathways enables the possible identification of more sustainable(resource efficient) pathways for biomass and bio-oil production.It is shown, for example, that feedstocks grown primarily for biomasssuch as switchgrass may be less sustainable using the exergy measurecompared to use of residue (e.g., forest thinnings) or waste biomass(e.g., equine waste). With regard to the pyrolysis process, thereis substantial reduction in exergy depletion when the coproducts noncondensablegases and biochar are recycled and utilized as a source of heat. Thesustainability of biomass production and conversion, as measured byexergy depletion, is strongly influenced by energy carriers. The studyreveals that the method of electricity production, i.e., on-site generationor grid electricity, as well as the choice of grid electricity canhave a significant impact on sustainability. The exergy content ofthe bio-oil produced varies from 24 to 27 MJ/kg bio-oil, which ismuch lower than traditional fuels. However, the cumulative exergydepletion for the production and conversion to bio-oil varies fromapproximately 4 to 11 MJ/kg bio-oil, which is also much lower thantraditional fuels. Breeding factors for biomass production and conversionto bio-oil based on cumulative exergy depletion vary from approximately2 to 5, demonstrating the potential exergy benefit of bio-oil productionusing fast pyrolysis. [ABSTRACT FROM AUTHOR]