Butanol Production from Rice Straw:

It is certified that the work contained in the thesis entitled “BUTANOL PRODUCTION FROM RICE STRAW: PROCESS DEVELOPMENT AND OPTIMIZATION”, by Amrita Ranjan (Roll No) was carried out under my supervision and that this work has not been submitted elsewhere for a degree.

List of Tables

C HAPTER 1

G ENERAL I NTRODUCTION AND

M OTIVATION OF T HESIS

Introduction

These statistics published by the Ministry of Petroleum and Natural Gas claim total reserves (proved and indicated) of 757 million metric tons of crude oil and 1241 billion cubic meters of natural gas in India as on April 2011 [2]. The prices of petroleum products (diesel, kerosene, petrol and jet fuel) have fluctuated significantly over the past 5 years.

Table 1.1: Production of crude oil for year 2010-11 (in thousand Tonnes) Item 2005-06 2006-07 2007-08 2008-09 2009-10* 2010-11*

Potential of Biomass Energy in India

It can be deduced from Figure 1.1 that rice production in India has grown almost 5 to 6 times in the last six decades. Nevertheless, about 15-20% of the biomass can be surplus, and is available for bioenergy generation.

Table 1.3. State-wise biomass production (in the form of both agro-residues and forest & wasteland) for the year 2008-09 in India

Food grains

Biofuels Endeavors of India
Aims and Scope of Present Thesis

In 2003, the Department of Petroleum and Natural Gas introduced the Ethanol Blended Gasoline Program with the mandate of blending 5% ethanol into gasoline [11]. With the resurgence of the sugar industry in 2005–2006, the Indian government announced the second phase of the 5% ethanol gasoline blend program.

Figure 1.1. All-India Area, Production and Yield of Rice alongwith coverage under Irrigation (Area - Million Hectares, Production - Million Tonnes, Yield - kg/Hectare) Source: [9]

C HAPTER 2

INTRODUCTION TO BIOBUTANOL

SCIENCE, ENGINEERING AND ECONOMICS

Introduction

In the next section, we briefly review the history of the ABE fermentation (for additional details, we refer the reader to Jones and Woods [12]). The ABE fermentation is one of the oldest known industrial fermentations with a history of more than 100 years.

Table 2.1 lists and compares some common properties of various alternative liquid fuels

Biochemistry of the ABE Fermentation

Acetyl-CoA can be converted to acetaldehyde (catalyzed by acetaldehyde dehydrogenase) and further to ethanol (catalyzed by ethanol dehydrogenase). Butyryl-CoA can be further converted to butyraldehyde (through the action of NADH and butyraldehyde dehydrogenase), and further to butanol (via the action of NADH and butanol dehydrogenase).

Figure 2.2: The metabolic pathway of ABE fermentation by Clostridia. Abbreviations: E 1 – pyruvate ferrodoxin oxidoreductase; E 2 – thiolase;

Microbial Cultures for ABE Fermentation

Shaheen et al. have done comparative studies on fermentation by these four main species (with different strains of them) using different substrates. Based on this study, Shaheen et al. concluded acetobutylicum was more suitable for starch.

Table 2.2: Comparative analysis of 4 Clostridia species *

Substrates for ABE Fermentation

This has several consequences, such as slower cell growth, slower metabolic transitions and higher acid accumulation. Solvent production was initiated at a total acid concentration of 4.5 g/L, while the final inhibition of fermentation occurred at a solvent concentration of 20 g/L. 4).

Solvent Recovery Techniques

A typical schematic of a fermentation process employing solvent recovery by liquid-liquid extraction using a rotating disk contactor is shown in Fig. A typical schematic of a fermentation process using solvent recovery with this technique is shown in Fig. The membrane composition also determines the extent of mass flux across the membrane.

The productivity of the ABE solvent in the fed batch fermentation process (integrated with in-situ solvent recovery with composite membrane) was 155 g/L. However, several practical problems arose, such as contamination of the membrane surface with some viscous impurities and non-uniform distribution of the culture. A schematic of the fermentation process integrated with adsorption columns for solvent recovery is shown in Fig.

Table 2.4. Summary of literature on various alternate substrates for ABE fermentation

Fermentation Process Design .1 Batch fermentation

The gas stripping technique was applied to ABE fermentation in batch culture (C. acetobutylicum on whey permeate) by Ennis et al. Some other studies published in the 1980s are those by Bahl et al.[55] and Afscher et al. 55] studied the limited two-stage phosphate fermentation of C .acetobutylicum in a chemostat and reported solvent concentration of 18.2 g/L with yield of 0.34 g/g and productivity of 0.55 g/L-h.

The salient features of the model were as follows: (1) The bacterial species considered is C. 2) The substrate consumption (glucose) was written in the form of the Herbert-Pirt equation. Various reactions in the metabolic pathway and the corresponding rate expressions along with kinetic parameters and notation are summarized in Table 2.10. In the flow sheets for the separation of gas-stripped ABE solvents, azeotropic columns are taken into account.

Table 2.7: Summary of literature on solvent recovery techniques in ABE fermentation

Economics of Acetone Butanol Fermentation

Separation of acetone, butanol and ethanol was achieved with trains of energy integrated distillation column. As a result, the breakeven price for butanol produced by the two processes also differs by about 20%. Thus, the cost of fermentation substrate and scale of production are the main factors affecting the breakeven price of biobutanol.

An increase in the price of process by-products can still reduce the breakeven price. In a subsequent article, Qureshi and Blaschek [339] assessed the economics of batch fermentation plants with a capacity of 153,000 tons of ABE production. Thus, although the substrate itself is cheap, the cost of pretreatment adversely affects the overall economics of the process.

Table 2.11: Summary of economic analysis of ABE fermentation processes (A) Analysis of Lenz and Moreira [330]

Overview

150] Ezeji T, Qureshi N, Blaschek HP (2007d) Production of acetone-butanol-ethanol (ABE) in a continuous flow bioreactor using germinated maize and Clostridium beijerinckii. 227] Qureshi N, Blaschek HP (1999c) Production of acetone-butanol-ethanol (ABE) by a hyperproducing mutant strain of Clostridium beijerinckii BA101 and recovery by pervaporation. 229] Qureshi N, Maddox IS (1995) Continuous production of acetone-butanol-ethanol using immobilized cells of Clostridium acetobutylicum and integration with product removal by liquid-liquid extraction.

254] Mulchandani A, Volesky B (1994) Production of acetone-butanol-ethanol by Clostridium acetobutylicum using a spin-filter perfusion bioreactor. 266] Godin C, Engasser JM (1988) Improved stability of the continuous production of acetone-butanol by Clostridium acetobutylicum in a two-stage process. 271] Soni BK, Soucaille P, Goma G (1986a) Effects of phosphate cycling on acetone-butanol production by Clostridium acetobutylicum in chemostat culture.

287] Badr HR, Toledo R, Hamdy MK (2001) Continuous acetone-ethanol-butanol fermentation of immobilized cells of clostridium acetobutylicum. 289] Maddox IS, Qureshi N, Roberts TK (1995) Production of acetone-butanol-ethanol from concentrated substrates by Clostridium acetobutylicum in an integrated fermentation-product removal process.

C HAPTER 3

R ICE S TRAW AS P OTENTIAL F EEDSTOCK FOR

B IOFUELS : A SSESSMENT AND R EVIEW

Introduction

Rice Straw: Structure, Composition and Properties

Rice straw is unique compared to other straws because it has a low lignin and high silica content. Rice straw consists mainly of three types of structural carbohydrate polymers: (1) cellulose, (2) hemicellulose and (3) pectic polysaccharides (lignin). Carbohydrate, protein and mineral content of rice straw can vary with variation in soil conditions, weather, fertilization, harvest time, crop growth etc.

A comparative overview of the mineral content of rice straw with other straws is given in Table 3.1. Rice straw as a feedstock has the advantage of having a relatively low total alkali content (Na2O and K2O typically comprise < 15% of the total ash), while wheat straw can typically have an alkali content of > 25% in the ash [14]. In the next section, we have described various pretreatment and hydrolysis methods for rice straw reported in the literature.

Table 3.1: Mineral content of various cereal straw [1]

Rice Straw: Pre-treatment/ Hydrolysis

Pretreatment has been considered one of the most expensive processing steps in cellulosic biomass-to-fermentable sugars conversion [15]. Enzymatic hydrolysis of rice straw can be improved by microwave pretreatment in the presence of water [22-23], and also in glycerine medium with less water [24]. Pretreatment can be carried out at low temperatures, but with a relatively long time and high concentration of the base.

Zhang and Cai [35] reported that alkaline pretreatment of chopped rice straw with 2% NaOH with 20%. The efficiency of the whole process is generally increased by the cumulative use of physical, chemical and enzymatic biomass pretreatment. The following table summarizes the different rice straw pretreatment techniques used in the production of different types of biofuels.

Biofuel Production from Rice Crop Residue: A Literature Review

58] studied fast pyrolysis of rice straw and sawdust under microwave irradiation with 2 ionic liquids, viz. For microwave heating of 20 minutes, yield of bio-oil from rice straw was 38%, while that of sawdust was 34%. These results pointed to the importance of aeration in the process of fermentation of rice straw hemicellulosic hydrolyzate.

64] have reported the preparation and characterization of solid biomass fuel made from rice straw and rice bran. 67] have studied the production of bio-oil from rice straw and bamboo sawdust under different reaction conditions. 76] have studied the two-stage pretreatment of rice straw with aqueous ammonia and dilute acid.

Conclusion

32] Moniruzzaman M (1996) Effect of steam explosion on the physicochemical properties and enzymatic saccharification of rice straw. 43] Hsu TC, Guo GL, Chen WH, Hwang WS (2010) Effect of dilute acid pretreatment of rice straw on structural properties and enzymatic hydrolysis. 51] Patel SJ, Onkarappa R, Shobha KS (2007) Investigation of ethanol production from fungal pretreated wheat and rice straw.

56] Yang SY, Wu CY, Chen KH (2011) The physical characteristics of bio-oil from fast pyrolysis of rice straw. 78] Park J-y, Ike M, Arakane M, Shiroma R, Li Y, Arai-Sanoh Y, Kondo M, Tokuyasu K (2011) DiSC (direct stalk saccharification) process for bioethanol production from rice straw. 81] Lei Z, Chen J, Zhang Z, Sugiura N (2010) Methane production from rice straw with acclimated anaerobic sludge: effect of phosphate supplementation.

S ELECTION OF S UBSTRATE AND

M ICROBIAL S TRAIN & U NDERSTANDING

ABE F ERMENTATION

Introduction

Material and Methods

Batch fermentation experiments were performed with 100 ml working volume of fermentation broth in custom-made 250 ml screw cap Erlenmeyer flasks (Fig. 4.4). All flasks were sparged with nitrogen at the beginning and after every 24 hours of fermentation to maintain anaerobic conditions. The optical density of the cells in the fermentation broth was measured using UV-Vis spectrophotometer (Thermo Fischer) with absorbance at 600 nm after appropriate dilution in water.

Quantification of total sugar was done by Anthrone test (Fig. 4.5) as indicated by Hedge and Hofreiter [9]. Solvent production in the fermentation broth was monitored on a gas chromatograph (Varian) using a CP Wax 52CB (250 mm × 0.25 mm × 0.39 mm) capillary column, and a flame ionization detector. Standard curve for quantitative estimation of acetone, butanol and ethanol solvent was plotted using GC grade standard acetone, butanol and ethanol solvents from Sigma Aldrich.

Figure 4.4: Maintenance and culturing of clostridial species. (a) RCM Broth, (b) Cultured RCM broth, (c) clostridial slant (d) bacterial lawn (spread plate)

Results and Discussion

Solvent yield was calculated as grams per liter of solvent produced per gram liter of total sugar added (g/g). Butanol selectivity was calculated as moles of butanol produced per mole of total solvent production (ABE). During vegetative growth, an oil immersion microscopic view (100×) of all four Clostridium strains shows cell motility.

This mechanism is logical as it allows the cell to find nutrients and move away from the byproducts produced by its own metabolism [15–16]. As the cell enters the stationary phase, solvent production begins, with acetone as the initial product. Upon other environmental cues, such as an anoxic environment, the cell germinates and restarts the vegetative cycle [17].