While oleaginous yeasts have been extensively investigated for single-cell oil production, less attention has been paid towards valorization of the erstwhile-discarded de-oiled biomass. The current study demonstrates the valorization potential of the de-oiled biomass through production of bio-crude by hydrothermal liquefaction process. The performance of the process was enhanced by using glycerol as co-solvent and also by optimizing the processing conditions. Glycerol addition enhanced the bio-crude yield up to 50 wt% with an improved energy content of 32 MJ/kg. The major organic groups found in the bio-crude are acids, esters and phenolics. Typical energy recovery achieved in bio-crude was in the range of 43–62%. Thus, strategic valorization of yeast into green crude with net energy gain, as evident from the energy balance, implies the process is energetically favourable. © 2019 Elsevier Ltd

R. Vinu

Department Of Chemical Engineering

Rajnish Kumar

Attada Yerrayya

Biomass

Energy balance

Glycerol

Liquefaction

BIO CHARS

COSOLVENTS

HYDROTHERMAL LIQUEFACTIONS

NET ENERGY GAINS

OLEAGINOUS YEASTS

Performance enhancements

Processing condition

SINGLE CELL OIL

yeast

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Cleaner Production

In this study, microwave-assisted co-pyrolysis of high ash Indian coal and rice husk is investigated to evaluate the yield and quality of the pyrolysis oil, and to understand the interactions during co-pyrolysis. Microwave co-pyrolysis experiments were conducted in a bench scale unit, and the effects of various parameters such as microwave power (420 W and 560 W), coal:rice husk ratio, and feed:susceptor (graphite) ratio on product yields and oil composition were thoroughly evaluated. Oil yield was not significantly affected by microwave power and feed:susceptor ratio for a particular coal:rice husk ratio. The oil yields were 11 ± 2 wt%, 15 ± 2 wt%, 18 ± 2 wt%, 21 ± 2 wt% and 26 ± 2 wt% for 100:0, 75:25, 50:50, 25:75 and 0:100 wt./wt. coal:rice husk, respectively, at both microwave powers, and followed an additive effect with increase in rice husk amount in the mixtures. Pyrolysis oil contained monoaromatic hydrocarbons, naphthalene derivatives, aliphatic hydrocarbons and phenolic derivatives. The interactions between coal and rice husk pyrolysis intermediates were evidenced in the form of enhanced yields of polyaromatic hydrocarbons with a concomitant reduction in yield of methoxy phenols. Pyrolysis oil from coal had highest heating value (36-38 MJ kg−1) due to the presence of aliphatic hydrocarbons, while that from rice husk had the lowest heating value (28-30 MJ kg−1) due to high oxygenate content. The heating values of co-pyrolysis oils were in the range of 30-36 MJ kg−1. Hydrogen constituted a major fraction in the pyrolysis gases, and the addition of rice husk to coal promoted the evolution of CO. © 2018 Elsevier B.V.

Fuel Processing Technology

Microwave-assisted co-pyrolysis of high ash Indian coal and rice husk: Product characterization and evidence of interactions

In this study, co-pyrolysis of five lignocellulosic biomass residues, viz. groundnut shell (G), bagasse (B), rice husk (RH), Prosopis juliflora (PJF) and mixed wood sawdust (MWSD), with two synthetic plastics, polypropylene (PP) and polystyrene (PS), was conducted to improve the quality of bio-oil. Equal composition of biomass and plastic was pyrolyzed at 450 W microwave power using graphite susceptor, and the yields of bio-oil, char and gas fractions were determined. The bio-oil yields from PS-biomass blends varied in the range of 51–60 wt%, with maximum yield obtained from PS-MWSD, while that from PP-biomass blends were 25–41 wt% with maximum yield obtained from PP-RH. The higher heating value of co-pyrolysis bio-oil was high (38–42 MJ kg−1) as compared to bio-oil obtained from only biomass pyrolysis (20–30 MJ kg−1). Energy yield of co-pyrolysis bio-oil was significantly higher with PS mixtures (73–81%) than PP mixtures (32–62%). Importantly, the bio-oil, char and gas yields, and organic composition of bio-oil were non-additive with respect to that obtained from pyrolysis of the individual feedstocks. The presence of PS boosted the production of aromatic hydrocarbons (48–54 wt%), while PP promoted aliphatic hydrocarbons (19–33 wt%) in co-pyrolysis bio-oil. Specifically, high selectivity towards alkanes in bio-oil was obtained from PP-RH mixture. Co-pyrolysis bio-oil contained less moisture with lower acidity compared to pyrolysis bio-oil. RH-PS and RH-PP mixtures were shown to be the better biomass-plastic combinations from the viewpoint of recovering high energy in bio-oil. The microwave co-pyrolysis process efficiency was also high (63–68%) and promising. © 2018 Elsevier B.V.

Microwave assisted co-pyrolysis of biomasses with polypropylene and polystyrene for high quality bio-oil production

Microalgae is projected as a promising third generation biomass feedstock for the production of biofuel and fine chemical intermediates. This study is focused on the selective production of chemicals from Nannochloropsis oculata microalga via catalytic fast pyrolysis technique using Co-Mo/γ-Al2O3 catalyst. Non-catalytic and catalytic fast pyrolysis (CFP) experiments were conducted in an analytical micropyrolyzer coupled with gas chromatograph/mass spectrometer to study the effects of temperature, catalyst-to-algae ratio, and metal loading on support on pyrolysate composition. The catalyst, Co-Mo/γ-Al2O3, was prepared using wetness incipient impregnation method, and characterized for its structure and pore size distribution. Catalyst-to-algae mass ratios used to study the pyrolysate composition and quality were 1:3, 1:1 and 2:1. The major organic compounds from both non-catalytic fast pyrolysis and CFP of the microalga were long chain nitriles, long chain alkanes and alkenes, polyaromatic and monoaromatic hydrocarbons. The optimum fast pyrolysis temperature under non-catalytic conditions that promoted the selectivity of aliphatic and aromatic hydrocarbons was 500 °C. The incorporation of Co-Mo/γ-Al2O3 catalyst promoted the formation of specific organic compounds like 1‑isocyanobutane and dimethylketene to the tune of 35% selectivity. The formation pathways for these compounds are proposed to involve dehydration, isomerization, ketonization and CH addition reactions of the amide and carboxylic acid moieties generated from the protein and lipid fractions of the alga. Owing to the low oxygen content in the pyrolysates from CFP, the estimated calorific value of organics in the pyrolysates was higher (33–39 MJ kg−1) than that of the microalga (18 MJ kg−1). © 2018 Elsevier B.V.

Algal Research

Non-catalytic fast pyrolysis and catalytic fast pyrolysis of Nannochloropsis oculata using Co-Mo/γ-Al2O3 catalyst for valuable chemicals

This study reports an experimental technique to obtain the isothermal mass loss profiles of four different microalgae (Chlorella vulgaris, Nannochlorpsis oculata, Schizochytrium limacinum, and Arthrospira platensis) under fast pyrolysis conditions in the temperature range of 400-700 °C at short residence times of 2-60 s using an analytical pyrolyzer. The microalgae investigated in this study vary significantly, based on elemental and biochemical composition. The apparent kinetic parameters of fast pyrolysis of the algae were evaluated using first-order and multidimensional diffusion models. The apparent activation energy and pre-exponential factor evaluated under fast heating rate conditions were lower compared to those reported under slow pyrolysis conditions, which is attributed to the diffusion effects. The rate parameters were validated by constructing a kinetic compensation plot, which showed that ln(A) = 0.19Ea + 0.43. The product time evolution at short time scales was studied using in situ Fourier transform infrared spectroscopy, and a majority of the functional groups evolved in the range of 5-12 s. The evolution of C=O and aliphatic C-H stretching vibrations for lipid-rich algae was slow, compared to that for protein-rich algae. The pyrolysates were characterized using gas chromatography/mass spectrometry, and the yield of nitrogen-containing organics followed a linear trend with the elemental nitrogen content in the algae. © 2017 American Chemical Society.

Energy and Fuels

Apparent Kinetics of Fast Pyrolysis of Four Different Microalgae and Product Analyses Using Pyrolysis-FTIR and Pyrolysis-GC/MS

A review on the hydrothermal processing of microalgal biomass to bio-oil - Knowledge gaps and recent advances

Performance enhancement of hydrothermal liquefaction for strategic and sustainable valorization of de-oiled yeast biomass into green bio-crude

Journal	Data powered by TypesetJournal of Cleaner Production
Publisher	Data powered by TypesetElsevier Ltd
ISSN	09596526
Open Access	No