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• Fast pyrolysis of mannan-rich ivory nut was performed at 350 °C and 500 °C. • Pyrolysis liquids (yield 58–60 wt%) were rich in levomannosan and 5-hydroxymethyl furfural. • Biochar and non-condensible gases (NCGs) were characterized. • Biochar holds potential for e.g. soil applications, NCGs hold potential for e.g. syngas processes. Ivory nut residues from the palm Phytelephas aequatorialis were converted via fast pyrolysis into a set of valuable biorefinery products, being (i) pyrolysis liquids rich in levomannosan and 5-hydroxymethyl furfural (5-HMF), (ii) biochar, with potential for soil applications, (iii) and non-condensable gases with potential for upgrading and syngas processes. The ivory nut residues were mannan-rich leftovers from button manufacturing in Ecuador. A handful of studies, dating back from the 20th century, have investigated gram-scale valorization of ivory nut to e.g. mannose. Nevertheless, advances in science and technology on biorefinery products called for a comprehensive reassessment of the valorization potential of this underutilized feedstock. A fully equipped, continuously operated lab-scale reactor (200 g.h−1 feed) was used for pyrolysis at 350 °C and 500 °C. The pyrolysis liquid yield was 57.53 wt% at 350 °C and 60.36 wt% at 500 °C. The aqueous phase obtained at 350 °C contained 17.5 wt% (d.b.) anhydrosugars, of which 90% was levomannosan, and contained 11.6 wt% (d.b.) furans, of which 56% was 5-HMF and 17% furfural. The carbon stability of the biochars, measured with the Edinburgh accelerated ageing tool, were 40.6% and 64.6%, respectively. Non-condensable gases during pyrolysis at 350 °C only were composed of CO 2 and CO (CO 2 :CO molar ratio of 4:1), while at 500 °C, gases were obtained with a CO 2 :CO:H 2 :CH 4 molar ratio of 9:9:4:1. Overall, the results demonstrate that pyrolysis of ivory nut holds potential as starting point for valuable biorefinery products. [ABSTRACT FROM AUTHOR]

Abstract Lignin-rich digested stillage as a novel feedstock for biochar production was subjected to slow pyrolysis. The lignin residue stemmed from a lignocellulosic ethanol pilot run with poplar, from which the stillage was anaerobically digested prior to pyrolysis. Pyrolysis conditions were optimized to meet guidelines put forth by the International Biochar Initiative and the European Biochar Certificate (molar H/C org ratio < 0.7 and O/C org ratio < 0.4), as biochar could be carbon-negative upon soil amendment, while reallocating nutrients to the field. Bench-scale pyrolysis of the lignin residue and straw were conducted according to a 33 factorial design with center runs (ranges: 370–450 °C highest treatment temperature, 5–45 min holding time and 5–50 °C.min−1 heating rate). Parametric and nonparametric statistics revealed that the highest treatment temperature was by far the most influencing factor for both feedstocks which 'pushed' H/C and O/C ratios within the desired range. Lignin-based biochar can be obtained with 50.7% yield, a H/C ratio of 0.70 and an O/C ratio of 0.20, already at 384 °C. This is considerably better when compared to straw-based biochar with identical H/C and O/C ratios, which came with a lower yield (33.7%) and required a modestly higher temperature (410 °C). Results from this study emphasize the feasibility to integrate slow pyrolysis in a lignocellulosic biorefinery. Graphical abstract Image 1 Highlights • Lignin residue from digested stillage was pyrolysed to biochar for the first time. • Temperature, heating rate and holding time were varied in a 33 factorial design. • Statistical models were used for process optimization to meet biochar standards. • The quality-quantity trade-off during pyrolysis was assessed. • At 384 °C, lignin-biochar with H/C = 0.7 and O/C = 0.2 is obtained with 50.71% yield. [ABSTRACT FROM AUTHOR]

This work pioneers the thermocatalytic conversion of tagua seeds (or ivory nut) from the palm Phytelephas aequatorialis into key chemical building blocks, being levoglucosenone, furfural and levomannosan. Annually, ca. 100,000 metric ton of those seeds are produced in Ecuador. Mannan (a mannose-polymer similar to cellulose) is the main constituent in tagua. Thermocatalytic conversions were first explored on analytical scale to see if – and to which extent – e.g., levoglucosenone, was obtained from tagua, using catalysts with proven activity for cellulose conversion, being H3PO4 or ZnCl2. Non-catalytic fast pyrolysis led to levomannosan as main product (33.89 wt% ± 0.24 wt%), much like levoglucosan is the main product from cellulose pyrolysis. Catalytic fast pyrolysis using H3PO4 or ZnCl2 resulted in value-added levoglucosenone (max 6.64 wt% ± 0.27 wt%) and furfural (max 13.17 wt% ± 0.66 wt%) at the expense of levomannosan (between 12 wt.%–14 wt%). Validation experiments with a continuous fast pyrolysis auger reactor were successful and led to pyrolysis liquids with e.g., 3.69 wt% levoglucosenone, using H3PO4 -infused ivory nut. Although further optimization should follow this work, the results showcased a fundamental "mannan to levoglucosenone and furfural" conversion and therefore the potential of mannan-rich feedstock for biorefining. Moreover, these results can be translated to other mannan-rich agricultural residues, like açaí seeds, which are a major residue in Brazil (1.1 million metric ton annually). [Display omitted] • Mannan-rich tagua was demonstrated a valuable biorefinery feedstock. • Tagua was converted to levoglucosenone and furfural with H 3 PO 4 and ZnCl 2 , resp. • Analytical experiments were successfully translated to mini-plant scale experiments. • The biorefinery potential of mannan-rich ivory nut has been showcased. [ABSTRACT FROM AUTHOR]

• Acid leaching breaks down the chemical structure of carbohydrates and proteins. • Pretreatment effects on pyrolysis volatiles have been discussed. • Removal of inorganics increased the relative yields in aromatics and aliphatics. • Influence of water-soluble and acid-soluble AAEM species was discussed. • Interactions between microalgae components and AAEMs catalysis were elucidated. This study compared the volatiles distribution in analytical scale pyrolysis (py-GC–MS) of Nannochloropsis gaditana (marine microalgae) and Scenedesmus almeriensis (freshwater microalgae) and their demineralized counterparts. The role of inorganic elements and their removal via ultrasonic treatment, water washing and (in)organic acid leaching were elucidated. Principal component analysis (PCA) and grey relational analysis were applied to analyze the pyrolysis volatiles distribution and demonstrate the influence of inorganic elements in pyrolysis, respectively. Demineralization affects (breaks down) the chemical structure of carbohydrates, followed by (to a lesser extent) proteins and lipids. Acid leaching promoted hydrolysis and suppressed the catalytic effect associated to inorganic elements in subsequent pyrolysis, compared to ultrasonic treatment and water washing. Elements like K and Na had a larger catalytic influence on microalgae pyrolysis than Ca and Mg. The composition and pyrolytic formation mechanism of major product groups at 500 °C were studied, including anhydrosugars, phenolics, furans, carboxylic acids, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, N-heterocyclic compounds, nitriles and amides. The results indicate that demineralization shows positive effects on fast pyrolysis of microalgae: (1) by disrupting the cell wall and releasing the lipids and cellular contents. Based on the py-GC–MS peak area normalized to sample mass, the relative contribution of hydrocarbons in the pyrolysis vapors increased from 25.5 % (NG: Nannochloropsis gaditana) to 32.1 % (NG-HCl: Nannochloropsis gaditana, HCl treated), and from 16.1 % (SA: Scenedesmus almeriensis) to 22.4 % (SA-HCl: Scenedesmus almeriensis, HCl treated); (2) by decreasing the relative yields in O-containing compounds resulting from the suppressed catalytic effects of alkali and alkaline earth metals (53.3 % (NG) to 37.1 % (NG-HCl), 57.5 % (SA) to 47.8 % (SA-HCl)) that would otherwise have been present in non-demineralized microalgae feedstock. The effects of demineralization on the denitrogenation of pyrolysis vapors were not that obvious. Suggestions for potential full scale applications have been proposed. [ABSTRACT FROM AUTHOR]

The long-term stability of biochar in soil is key for carbon capture and storage and soil amelioration. Yet, its assessment is hampered by the long time-horizons needed to actually probe biochar's stability. Therefore, quick and reliable estimation methods are sought. Analytical pyrolysis (Py-GC-MS) offers a quick tool to predict biochar's stability in soil, if adequate and validated metrics can be extracted from it. This work derives and validates stability scores from biochar pyrograms and advanced data analysis. The stability scores were benchmarked by comparison with other stability metrics (Edinburgh stability tool, fixed carbon content and atomic H/C ratio). Calibration of the stability scores with these stability metrics had an R 2 between 0.61 and 0.95; validation resulted in R 2 between 0.59 and 0.72. Overall, this work illustrates how Py-GC-MS can lead to simple and adequate predictors of biochar stability. [Display omitted] • Stability Scores derived from Py-GC-MS can probe the stability of biochar in soil. • Py-GC-MS and principal component analysis were combined to set up Stability Scores. • Stability scores were selected by comparison alternative stability metrics. • Stability scores were calibrated with max R2 of 0.95. • Stability scores were validated with max R2 of 0.72. [ABSTRACT FROM AUTHOR]

[Display omitted] • A green and effective strategy for biomass valorization was proposed. • Citric acid (CA) washing promoted furfural production during the torrefaction step. • CA washing increased levoglucosan yield to 3.76 times for W250-FP compared to R250-FP. • Torrefaction reduced acetic acid yield by 65% for W250-FP compared to WRaw-FP. Converting agricultural waste biomass into value-added chemicals is attractive. However, a low selectivity for target chemicals hinders practical applications. This study presents a stepwise strategy to convert sugarcane trash (ST) into furfural and levoglucosan with high selectivity. The approach includes citric acid washing to reduce mineral content in ST, followed by torrefaction at different temperatures (210 °C, 250 °C and 290 °C) in a tube furnace and then fast pyrolysis at 500 °C in a micro-reactor. This study highlights the valorization potential of the torrefaction liquid, an often overlooked by-product from torrefaction, through significantly increasing furfural selectivity during the torrefaction of washed ST. Furthermore, the vapors from subsequent fast pyrolysis of washed-torrefied ST exhibited reduced acetic acid content compared to that of solely washed ST, which is advantageous for minimizing the acidity of the resulting bio-oil. Moreover, fast pyrolysis of ST, treated with washing and torrefaction at 250 °C, achieved a high levoglucosan yield while maintaining a high furfural yield obtained in the prior torrefaction step. The findings of this study provide valuable insights into future research and industrial applications in agricultural waste biomass utilization. [ABSTRACT FROM AUTHOR]

2-methyl furan (MF) is a fuel additive with improved fuel characteristics compared to bio-ethanol. Unfortunately, the production of MF (from furfural (FF) hydrogenation) is not economically feasible. Interestingly, molten salts in biomass pyrolysis have shown to promote the formation of furans (mainly FF). Because molten salts hydropyrolysis could be an alternative route to both produce FF and convert it into MF, an assessment is indispensable. Molten salts pyrolysis and hydropyrolysis of pinewood and wheat straw and related model compounds were studied in a micro-reactor. The effect of hydropyrolysis process variables was assessed on the total detectable condensable vapors and MF formation. At low pressures (0.4 MPa), the chloride salts favored the production of FF and acetic regardless of the reaction atmosphere. Under a high pressure of hydrogen though (1.6 and 3.0 MPa), the conversion of FF to MF was enhanced through hydrogenation, hydrodeoxygenation and demethylation reactions. Molten salts hydropyrolysis at 350 °C and pressures of either 1.6 MPa (biomass mass fraction of 0.09) or 3.0 MPa (biomass mass fraction of 0.24) were optimal and yielded ca. 8 wt% to 9 wt% MF. Reaction temperatures >350 °C were unfavorable for the MF yield and instead promoted furfural decarbonylation to furan. [Display omitted] • Hydropyrolysis in molten salts highly promoted 2-methyl furan formation. • Targeted production of 2-methyl furan as fuel additive. • Higher pressure and biomass mass fraction are beneficial to product yield. • Product portfolio and yield in molten salts pyrolysis is carrier gas dependent. [ABSTRACT FROM AUTHOR]

This study outlines the effect of citric acid leaching on the quality and stability of fast pyrolysis bio-oils from sugarcane bagasse (SCB) and sugarcane trash (SCT). The quality of bio-oil was probed by GC-MS analysis, elemental composition, higher heating value, water and solids content, pH, dynamic viscosity and stability (ageing). Pyrolysis was performed at 500 °C in a fully controlled, continuously operated plant with a biomass throughput of ca. 300 g.hr−1. While citric acid leaching causes a decrease of the average bio-oil yield with 5%, it does not lead to a bio-oil with improved fuel-related properties. However, the bio-oil composition became more advantageous in light of its biorefining. Indeed, citric acid leaching led to an increased levoglucosan concentration – a promising platform chemical – of 17% for SCB and of to 35% for SCT (based on relative abundance in GC-MS). In tandem, the concentration of carboxylic acids and phenols in the bio-oil decreased after citric acid leaching, which is beneficial for downstream purification of levoglucosan. Regarding the non-condensable gases, CO and CO 2 represented between 88% and 91% by weight of the total non-condensable gases produced in pyrolysis. Therefore, the results of this study demonstrate that optimized biomass demineralization pretreatment with citric acid could produce bio-oil at high yield and rich in high-value chemical compounds like levoglucosan. Biomass demineralization pretreatment however, does not result in bio-oil with improved quality for fuel purposes, nor does it necessarily lead to bio-oil having higher stability. • Mild pretreatment with CA is effective in ash removal in sugarcane residues. • CA pretreated feedstock has higher bio-oil yields on pretreated feedstock basis. • Fresh/aged trash derived bio-oils have lower viscosity than bagasse derived bio-oils. • CA pretreatment holds no major benefit for bio-oil composition in terms of fuel use. • Major increase in anhydrosugar content after mild CA pretreatment of sugarcane residues. [ABSTRACT FROM AUTHOR]