Suresh Kumar Puri

Hydrothermal conversion of lignin to substituted phenols and aromatic ethers

Hydrothermal liquefaction of lignin was performed using methanol and ethanol at various temperatures (200, 250 and 280°C) and residence times of 15, 30 and 45min. Maximum liquid product yield (85%) was observed at 200°C and 15min residence time using methanol. Increase in temperature was seen to decrease the liquid products yield. With increase in residence time, liquid yields first increased and then decreased. FTIR and (1)H NMR showed the presence of substituted phenols and aromatic ethers in liquid products and breakage of β-O-4 or/and α-O-4 ether bonds present in lignin during hydrothermal liquefaction was confirmed through FTIR of bio-residue. In comparison to the existing literature information, higher lignin conversion to liquid products and maximum carbon conversion (72%) was achieved in this study.

Biodiesel surrogates : Achieving performance demands

Synthesis of surrogate molecules is particularly useful for generating in sight of structural-activity relationships, understanding processes and improving the performance. In order to improve upon the physico-chemical properties of biodiesel, methyl, ethyl, isopropyl and n-butyl esters of beta-branched fatty acid have been synthesized, initiating from beta-branched alcohols. Beta-branched alcohols upon oxidation gave corresponding acids, which were converted to their esters. The synthesized esters have substantially better oxidative stability, exhibited by Rancimat oxidation induction period of more than 24 h. The cloud point of synthesized esters is < -36 degrees C, pour point is < -42 degrees C and CFPP is < -21 degrees C, which is substantially better than fatty acid methyl esters. Besides achieving the objective of better oxidative stability and improved low temperature properties, the synthesized surrogate esters have viscosity in the range of 4.2-4.6 cSt at 40 degrees C, meeting the international diesel and biodiesel standards. The cetane number of synthesized esters is 62-69, which is much better than diesel and biodiesel. The blends of the synthesized esters in diesel at 5% and 10% meet Indian standards of diesel.

Aquatic weeds as the next generation feedstock for sustainable bioenergy production

Increasing oil prices and depletion of existing fossil fuel reserves, combined with the continuous rise in greenhouse gas emissions, have fostered the need to explore and develop new renewable bioenergy feedstocks that do not require arable land and freshwater resources. In this regard, prolific biomass growth of invasive aquatic weeds in wastewater has gained much attention in recent years in utilizing them as a potential feedstock for bioenergy production. Aquatic weeds have an exceptionally higher reproduction rates and are rich in cellulose and hemicellulose with a very low lignin content that makes them an efficient next generation biofuel crop. Considering their potential as an effective phytoremediators, this review presents a model of integrated aquatic biomass production, phytoremediation and bioenergy generation to reduce the land, fresh water and fertilizer usage for sustainable and economical bioenergy.

Electro-biocatalytic conversion of carbon dioxide to alcohols using gas diffusion electrode

Impact of gas diffusion electrodes (GDEs) was evaluated in enhancing the CO2 bio-availability for its transformation to C4-organics, especially to alcohols using selective mixed culture. Observed current density was more stable (9-11 A/m2) than submerged experiments reported and significantly varied with pH and respective CO2 solubility. Uncontrolled operating pH (starting with 8.0) showed its impact on shifting/triggering alternate metabolic pathways to increase the carbon length (butyric acid) as well as producing more reduced end products, i.e. alcohols. During the experiments, CO2 was transformed initially to a mixture of volatile fatty acids dominated with formic and acetic acids, and upon their accumulation, ethanol and butanol production was triggered. Overall, 21 g/l of alcohols and 13 g/l of organic acids were accumulated in 90 days with a coulombic efficiency (CE) of 49%. Ethanol and butanol occupied respectively about 45% and 16% of total products, indicating larger potential of this technology.

Intensification of steam explosion and structural intricacies impacting sugar recovery

Dilute acid (DA) pretreatment at pilot level failed for cotton stalk (CS) due to the technical issues posed by its inherent nature. Reasonable glucan conversion has been reported via two-stage pretreatment but adds on to the process cost. Proposed herewith is a single-stage steam explosion (SE) process preceded by water extraction resulting in high sugar recovery from CS. Raising the extraction temperature to 80°C increased the glucan conversion from 37.9 to 52.4%. Further improvement up to 68.4% was achieved when DA was incorporated during the room temperature extraction. LC-MS revealed the formation of xylo-oligomers limiting the glucan conversion in proportion to the length of xylo-oligomers. Varying extraction conditions induced structural alterations in biomass after SE evident by compositional analysis, Infrared Spectroscopy, X-Ray Diffraction and Scanning Electron Microscopy. Overall glucose recovery, i.e. 75.8-76.7% with and without DA extraction respectively was achieved.

Thermochemical Valorization of Lignin

Abstract The inevitability of transition toward a biobased economy is fueled by the problems related to fossil fuel utilization such as climate change due to greenhouse gas emissions. Lignin is a renewable feedstock that can be used to produce hydrocarbons in a sustainable manner. Lignin is obtained as a by-product of several conversion processes when it is isolated from the lignocellulosic biomass matrix. It is the major fraction that contributes to the organic hydrocarbons such as aromatics, phenolics, and platform chemicals that are presently produced from fossil resources. Lignin exhibits different physicochemical characteristics depending on the isolation process used. Lignin, over the years, has been converted to various value-added hydrocarbons (bioenergy, biofuels, biochemicals, and petrochemical feedstocks) using several thermochemical methods of conversion such as pyrolysis, gasification, and liquefaction. Challenges in the valorization of lignin include understanding the effect of source on the lignin structure, development of novel catalysts for conversion, increased selectivity and yield from processes, and effective separation processes.

The Pretreatment Technologies for Deconstruction of Lignocellulosic Biomass

Owing to the finite supply of fossil fuels, greenhouse gasses emission, global warming, increasing price, and unexpected fluctuations, there is a need to pay attention for alternative energy resources and thus interest in ethanol which is renewable, environmentally sustainable, and economically viable fuel has been strengthened. Due to economic and environmental concerns cropped up with the use of the first-generation ethanol processes, second-generation ethanol processes which comprise the use of waste biomass, viz., agricultural crop residues, municipal solid waste, sludge, livestock manure, etc., has been contemplated to be the hot emerging field. However, due to many technological issues, development of an effective technology is still a challenge. This chapter, therefore, provides insight into the pretreatment technologies involved in the production of free sugars which can be fermented to ethanol along with discussion on the merits and demerits of each of the technologies and their future prospects. This chapter also deals with various biomass-related issues and the updated technology status along with commercial aspects.

High-Value Coproducts from Algae—An Innovational Way to Deal with Advance Algal Industry

Expanded worldwide energy consumption and usage of fossil fuel cause its exhaustion and create energy crises, fuel security, global warming that have prompted a development of energy from alternative biomass that is renewable, economical, and eco-friendly. First- and second-generation biomass types, nonetheless, are frequently reprimanded because of displacement of food and the amount of crops it takes to deliver a gallon of oil. Algae to biodiesel (third-generation biofuel) have gained attention by many researchers, experts from petroleum industry as inexhaustible reliable and secure source of energy. Department of Energy, Govt. of USA, has investigated that algae grow much faster than terrestrial plants which give 30 times more energy yield per acre than land crops such as soybeans. Algae are a renewable bioresource that use sunlight, mitigate CO2 emissions, reduced nutrients (N, P, and K) from waste streams and water, and produce biomass in the form of sugars, proteins, and oils that can be processed into both biofuels and valuable coproducts. In light of utilization, worldwide algal products are separated into nutraceuticals, nourishment and bolster supplements, pharmaceuticals, paints, colorants, etc. Algal-derived coproducts such as carotenoids, β-carotene, omega 3 polyunsaturated fatty acids (docosahexaenoic acid and eicosahexaenoic), astaxanthin, squalene, phycobiliproteins have increased popularity from the neutraceuticals and pharmaceutical industry and are relied upon to give high income to the algae producing companies around the world. A few algal strains with a high wholesome esteem and vitality content are developed industrially as aquaculture feed and are also a potential source of lipids, ethanol, and hydrogen. In this chapter, we attempt to elucidate the primary existing and potential high-value coproducts and its commercial significance, algal species used and market sizes, trends, and future prospects.

Characterization of ionic liquid pretreated plant cell wall for improved enzymatic digestibility

An insight into the properties of cell wall of mustard stalk (MS) pretreated by five ionic liquids (ILs) revealed ILs interaction with cellulose, hemicellulose and lignin components. Differential Scanning Calorimetry (DSC) showed increased pore size coupled with increased population of pores evoked by certain ILs in better facilitating enzymatic accessibility. Interestingly, all the five ILs predominantly increased the propensity of two pore sizes formation; 19 and 198 nm, but remarkable difference in the pore volumes of pretreated MS suggested the supremacy of [OAc]- based ILs, resulting in higher glucose yields. Cellulose I to II transition in pretreated MS was supported by the reduced total crystallinity index (TCI), lateral order index (LOI) values. Strong inverse correlation existed between the said parameters and residual acetyl content with enzymatic hydrolysis (R2 > 0.8). An inverse relationship between hydrogen bond basicity, LOI and TCI suggested it to be a good indicator of IL pretreatment efficiency.

Long-term operation of electro-biocatalytic reactor for carbon dioxide transformation into organic molecules

Electro-biocatalytic reactor was operated using selectively enriched mixed culture biofilm for about 320 days with CO2/bicarbonate as C-source. Biocathode consumed higher current (-16.2 ± 0.3 A/m2) for bicarbonate transformation yielding high product synthesis (0.74 g/l/day) compared to CO2 (-9.5 ± 2.8 A/m2; 0.41 g/l/day). Product slate includes butanol and butyric acid when CO2 gets transformed but propionic acid replaced both when bicarbonate gets transformed. Based on electroanalysis, the electron transfer might be H2 mediated along with direct transfer under bicarbonate turnover conditions, while it was restricted to direct under CO2. Efficiency and stability of biofilm was tested by removing the planktonic cells, and also confirmed in terms of Coulombic (85-97%) and carbon conversion efficiencies (42-48%) along with production rate (1.2-1.7 kg/m2 electrode) using bicarbonate as substrate. Selective enrichment of microbes and their growth as biofilm along with soluble CO2 have helped in efficient transformation of CO2 up to C4 organic molecules.