Recent advances in bioenergy research vo

Adhikari Dilip Kumar, Biotechnology Area, Indian Institute of Petroleum, Dehradun Agarwal Madhu, Department of Chemical Engineering, MNIT, Jaipur Alam T., Agricultural & Food Engineeri

Recent Advances in Bioenergy Research

Volume I

Edited by SACHIN KUMAR, ANIL K SARMA

Sardar Swaran Singh National Institute of Renewable Energy, Kapurthala, India

ISBN 978-81-927097-0-3

© Sardar Swaran Singh National Institute of Renewable Energy, Kapurthala-2013

Electronic version published by SSS-NIRE

ALL RIGHTS RESERVED

A Case Study in Assam, India

D.C Baruah, Moonmoon Hiloidhari

4 Bio Mass Fuel Generation- An Ultimate Energy Resource 44

Ajeet Kumar Upadhyay

Part-II: Thermo-chemical Conversion 52

5 Modeling of Biomass Gasification Processes in Downdraft Gasifiers: 53

6 Prospect of Bioenergy Substitution in Tea Industries of 67

North East India

B.J Dutta, D Baruah, M Saikia, R Bhowmik, D.C Baruah

7 Drying Of Biomass Fuel Used For Gasifier Using Waste Heat 79

R Soni, A.K Jain, B.S Panesar, P.K Gupta

Usha Bajpai, Suresh C Bajpai

8.3 The Indian National Programme on Improved Chulhas 96

9 Development of a Briquetting Machine for Jatropha Seed Cake 105

H Raheman, B Singh, T Alam, D Padhee

References 113

A.P Singh Chouhan, S.P Singh

M.L Bamboriya

and Global Warming

Sarbjit Singh Sooch

Hyderabad to Get 50MW from Garbage (MSW)

K.K Jain, J Praveen

(Segregated high CV fraction of MSW)

Experimental Studies on Biogas Plant

Usha Bajpai, Puja Singh

14.1 Introduction 159 14.2 Materials and Methods of Experimental Studies 164

15 Poultry Litter as an Alternate Feed Stock to Cattle Dung for 170

Biogas Production and Power Generation

Sarabjit Singh Sooch, Urmila Gupta, Anand Gautam

16 CFD Modelling of an UASB Reactor for Biogas Production from 176

Industrial Waste/Domestic Sewage

Partha Kundu, I.M Mishra

Shailendra Kumar Singh, M.K Jha, Ajay Bansal, Apurba dey

17.2 Physiology of H2 production in green algae 196

18 Jatropha (Jatropha Curcas) L Plantations and Climate Change 208

18.9 Plant responses to climate change 215

19 Biodiesel Production from Algal Species Grown on Dairy Wastewater 221

Richa Kothari, Vinayak V Pathak, D.P Singh

20 Green Technology for Biodiesel Production using 230

Waste Material Based Heterogeneous Catalyst

Anil Kumar Sarma, Ashish P Singh Chouhan

Sunflower Ethyl Ester and its Blends

R Kumar, A.K Dixit, S K Singh, G.S Manes, R Khurana

22 Thermophiles: smart bugs for ethanol production from 249

agricultural residues

Sachin Kumar, Pratibha Dheeran, Dilip K Adhikari

23 Study of Bioethanol Production from Brewer’s Spent Grain 258

using Fusarium oxysporum

Abhay Dinker, Arvind Kumar, Madhu Agarwal

Preface

Sachin Kumar, A.K Sarma

Bio-energy research has received tremendous attention all over the world due to steep hike in petroleum prices and environmental concerns At the current electricity generating capacity and other available energy sources, a huge gap exists between the demand and supply (above 15%) and the Conventional Energy resources of the country are meagre Agricultural crop residues production in the country is about 550 Mt/year and is likely to increase in the coming years Majority of the crop residues are either processed in uneconomic way or get destroyed as such

Apart from the crop residues, other biomass such as animal excreta, forest wastes and agro-industrial wastes are also available in abundance and can play a major role in supplementing the energy resources of the country Waste biomass materials include various natural and derived materials, such as woody and herbaceous species, bagasse, agricultural waste, waste from paper, municipal solid waste, industrial waste, sawdust, grass, food processing waste, waste oil, non-edible oil or shell of oil-bearing seed, aquatic plants and algae, etc., which could be potentially used for production of useful fuels and chemicals The average majority of biomass energy is produced from wood and wood wastes (64%), followed by municipal solid waste (24%), agricultural waste (5%) and landfill gases (5%) Waste and degraded lands are generally used for energy plantation and biomass production

There is no debate on the issue that renewable energy is the only sustainable energy in nature Biomass energy in particular is one of the cleanest form of energy gifted by nature This is also the ‘waste to wealth’ making weapons for the farmers Because, all forms of derived agricultural waste can be converted to useful energy that directly contribute to the income of farmers and nation as well Moreover, they are highly beneficial from the viewpoint of environmental pollution control and an asset for carbon credit

Keeping in view the need and importance of bioenergy research in our country,

we express pleasure to introduce the first edition of ‘Recent Advances in Bioenergy Research- Volume-I’ in the form of a book The book is divided in five parts viz Part-I: Biomass Assessment and Management for Energy Purpose; Part-II: Thermo-chemical Conversion; Part-III: Biogas & Biohydrogen; Part-IV: Production Aspects of Biodiesel;

Part-V: Lignocellulosic Ethanol Production Each section includes respective chapters from Eminent Academician, Scientists and Researchers in the field We are really grateful for their commendable contribution for this book

Emphasis is given such that current trends of research and investigation in the bioenergy sector can be easily worked out from the in-depth study of this book Our efforts will be successful if the readers dig up the expected gain out of these articles

Adhikari Dilip Kumar, Biotechnology Area, Indian Institute of Petroleum, Dehradun

Agarwal Madhu, Department of Chemical Engineering, MNIT, Jaipur

Alam T., Agricultural & Food Engineering Department, Indian Institute of Technology,

Kharagpur

Bajpai Suresh C., BSIP, 53, University Road, Lucknow

Bajpai Usha, Renewable Energy Research Laboratory, Department of Physics,

University of Lucknow, Lucknow

Bamboriya M.L., MNRE, New Delhi

Bansal Ajay, Department of Chemical Engineering, Dr B R Ambedkar National

Institute of Technology, Jalandhar

Baruah D., Department of Energy, Tezpur University, Napaam, Assam

Baruah D.C., Department of Energy, Tezpur University, Napaam, Assam

Bhavanam Anjireddy, Department of Chemical Engineering, NIT, Warangal

Bhowmik R., Department of Energy, Tezpur University, Napaam, Assam

Chouhan Ashish P Singh, Sardar Swaran Singh National Institute of Renewable

Energy, Kapurthala

Dey Apurba, Department of Biotechnology, National Institute of Technology,

Durgapur

Dheeran Pratibha, Biotechnology Area, Indian Institute of Petroleum, Dehradun

Dinker Abhay, Department of Chemical Engineering, MNIT, Jaipur

Dixit A.K., Department of Farm Machinery and Power Engineering, Punjab

Agricultural University, Ludhiana

Dutta B.J., Department of Energy, Tezpur University, Napaam, Assam

Gautam Anand, School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Gupta P.K., School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Gupta Urmila, School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Hiloidhari Moonmoon, Department of Energy, Tezpur University, Napaam, Assam

Jain A.K., Sardar Swaran Singh National Institute of Renewable Energy, Kapurthala

Jain K.K., Ellenki Engineering College, Hyderabad

Jha M.K., Department of Chemical Engineering, Dr B R Ambedkar National Institute

of Technology, Jalandhar

Khurana R., Department of Farm Machinery and Power Engineering, Punjab

Agricultural University, Ludhiana

Kothari Richa, School for Environmental Sciences, Babasaheb Bhimrao Ambedkar

University, Lucknow

Kumar Arvind, Department of Chemical Engineering, MNIT, Jaipur

Kumar R., Department of Farm Machinery and Power Engineering, Punjab Agricultural University, Ludhiana

Kumar Sachin, Sardar Swaran Singh National Institute of Renewable Energy,

Kapurthala

Kundu Partha, Department of Chemical Engineering, Indian Institute of Technology

Roorkee, Roorkee

Manes G.S., Department of Farm Machinery and Power Engineering, Punjab

Agricultural University, Ludhiana

Mishra I.M., Department of Chemical Engineering, Indian Institute of Technology

Roorkee, Roorkee

Padhee D., Agricultural & Food Engineering Department, Indian Institute of

Technology, Kharagpur

Panesar B.S., School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Pathak Vinayak V., School for Environmental Sciences, Babasaheb Bhimrao

Ambedkar University, Lucknow

Praveen J., Mall Reddy Engg College, Hyderabad

Raheman H., Agricultural & Food Engineering Department, Indian Institute of

Technology, Kharagpur

Saikia M., Department of Energy, Tezpur University, Napaam, Assam

Sarma Anil Kumar, Sardar Swaran Singh National Institute of Renewable Energy,

Kapurthala

Sastry R.C., Department of Chemical Engineering, NIT, Warangal

Sharma S.K., Energy Research Centre, Panjab University, Chandigarh

Singh Avtar, Department of Forestry and N.R., Punjab Agricultural University,

Singh Puja, GCRG Group of Institutions, Bakshi Ka Talab, Lucknow

Singh S.K., Department of Farm Machinery and Power Engineering, Punjab

Agricultural University, Ludhiana

Singh S.K., School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Singh S.P., School of Energy and Environmental Studies, Devi Ahilya

Vishwavidyalaya, Takshila Campus, Khandwa Road, Indore

Singh Shailendra Kumar, Department of Chemical Engineering, Dr B R Ambedkar

National Institute of Technology, Jalandhar

Soni R., School of Energy Studies for Agriculture, College of Agricultural Engineering

and Technology, Punjab Agricultural University, Ludhiana

Sooch Sarbjit Singh, School of Energy Studies for Agriculture, College of Agricultural

Engineering and Technology, Punjab Agricultural University, Ludhiana

Upadhyay Ajeet Kumar, Department of Chemical Engineering, IITT College of Engineering, Pojewal

Part I Biomass Assessment and Management

for Energy Purpose

CHAPTER 1 CHARACTERISTICS OF BIOMASS

A.K Jain

1.1 Introduction

All the plant materials produced through photosynthesis via carbon dioxide fixation is biomass This includes agricultural products and residues, fuel wood trees and agro-industrial waste materials Major agricultural products such as grains, fruits, vegetables etc are used for human consumption where as crop residues and forestry residues and fuel woods are very important from energy point of view

The word biomass in this text would further refer to agricultural crop residues and fuel woods Biomass can be used as energy source directly through combustion or can be converted to gaseous liquid and solid fuels which are more convenient to use and efficient, through thermochemical (combustion, gasification and pyrolysis) and biochemical (anaerobic digestion and fermentation) conversion processes

All agricultural crop residues, agro-industrial wastes and fuel trees are cellulosic materials but their individual characteristics vary over a wide range In the present scenario of biomass conversion to useful energy products, selection of the biomass suitable for a specific use or application is extremely important which is possible with sufficient property data Therefore, importance of adequate characterization data has been realized world wide for designing of any thermo-chemical or biochemical conversion device

ligno-During the last two decades several publications have appeared containing data on thermodynamic properties of biomass materials The characteristics of biomass reported in the literature differ to a large extent The difference may be attributed to many factors such

as agro-climatic conditions (type of soil and mineral content), variety of crop grown, sampling technique etc While conducting laboratory experiment on determination of characteristics, the author observed the different characteristics of sample from main trunk, primary and secondary branches of the same tree The sample from the main trunk had high ash, density, low calorific value and higher cellulose content compared to primary

and second limbs However the difference was of the order of 1 to 3% in most of the cases Another observation is that if a biomass ground sample is put to sieve analysis, different biomass fractions obtained after the sieve analysis do not exhibit similar characteristics It is, therefore essential that the biomass sample should be carefully selected and should be a true representative sample for reliable results

Fuel characteristics important to the design and analysis of biomass conversion processes are; Physical properties, i.e density, angle of repose and moisture content; thermal properties i.e calorific value and proximate analysis and chemical properties elemental analysis and chemical composition The physical properties vary considerably with environment and handling procedures whereas the remaining are intrinsic properties These properties are extremely useful in the design of biomass conversion device and processes analysis

on dry weight basis The true density of several species of fast growing fuel wood trees

such as Acacia, Albizia, Eucalyptus, Derris indica, Leucaena Lecocephala, Arjuna etc, are

reported by Jain, 1997 The true density values for these woods vary from 600 to 820 kg/m3

The bulk is the weight of bulk biomass material divided by the volume occupied The weight of the biomass depends on the size, shape and level of its compaction or densification It determines the storage capacity of fuel charging hopper and the size of any furnace, gasifier or other biomass conversion device It is useful in the evaluation of transportation cost and storage space for biomass fuel

Bulk density of a fuel is different from that of true or specific density of the single fuel For example, the true density of eucalyptus is 700 kg/m3, whereas the bulk density of 2-3.5 cm3 cube pieces of eucalyptus is around 250-300 kg/m3 Bulk densities of certain fuels are given in Table 1.1

Table 1.1 Bulk density and true density of certain fuel materials

1.2.2 Angle of Repose

The angle of repose is the angle made by the biomass from the horizontal to the sides of pile under free falling conditions It is expressed in degrees It is a flow property of the material It is generally determined by filling a large open ended tube with oven dry biomass, keeping the tube with its one end on the ground and then lifting the tube in such a manner that the biomass forms a pile on the ground The angle made by the pile with the horizontal base is the angle of repose The values of angle of repose depend on the size and moisture content of the biomass

Angle of repose is useful in the determination of the angle of fuel hopper, fuel transportation lines to the furnaces or gasifier During the thermochemical conversion process the angle of repose changes due to change in shape and size of the fuel particle If

the angle of repose approaches 90 degrees or more it indicates tendency of the fuel towards bridging Lower angle of repose is an indication of free flow behavior of biomass material As an example the angle of repose for oven dry paddy husk is 58 degrees

1.2.3 Moisture Content

Most of the biomass are hygroscopic in nature and absorb moisture from the atmosphere Moisture in biomass is fundamentally subdivided into inherent, surface and decompo-sition moisture Inherent moisture is the moisture a fuel can hold in the capillary openings

of the biomass when in equilibrium with the atmosphere Surface moisture occurs on the surface of the biomass and is in excess of inherent moisture The moisture content of biomass cited in the literature usually refers to inherent plus surface moisture

The percent moisture content (MC) of the biomass can be determined by drying the sample at 110 oC in hot air oven till a constant weight is obtained The method is known as standard oven method The following expression may be used for computing percent moisture:

Moisture content of a biomass is usually reported on wet weight basis as indicated

by above equation Since the moisture content of biomass varies from day to day due to variation in atmospheric relative humidity and temperature It is, therefore, preferable to report the biomass characteristic data on dry weight basis At a relative humidity of 90 to 95%, the moisture content of most biomass ranges from 25 to 35%, which reduce to around 10% at a relative humidity of 30 to 40%

The moisture content on wet weight basis can be converted to dry weight basis using the expression given below In the following equation Mw and Md are the percent moisture content on wet and dry weight basis respectively

During storage, the exposure of biomass to high relative humidity should be avoided so that the high moisture in biomass due to high relative humidity do not exceed too much, because higher moisture in biomass lead to its faster decay The

The net heating value and the moisture content of a biomass can be correlated by the following expression In the expression below λ, Mf, CVw and CVd are latent heat

of vaporization, moisture fraction of biomass, heating value of wet and dry biomass respectively

CVw = (1-Mf) x CVdλMf

The theoretical limit of moisture for cellulose at which the combustion is no longer self sustaining is 88%, however, in practice, the moisture content at which the biomass combustion can be sustained is much lower i.e 70% For gasifier, the optimum moisture content of the biomass is 15%, and higher moisture in biomass leads to poor gasifier performance Also high moisture lowers the effective heating value of the biomass and should be avoided while using as fuel in furnaces

Decomposition moisture is the moisture formed from organic compounds of biomass during thermal decomposition reactions It is estimated stoichiometrically that every kilo gram of biomass yields 450 to 600 gram of water during thermal decomposition reactions depending on its composition

1.3.1.1 Higher Heating Value

It is the amount of heat liberated when a known quantity of biomass is burned under ideal combustion condition at constant volume and the decomposition moisture is condensed i.e its latent heat of vapourization is taken into account It is determined using standard bomb calorimeter, where known weight of biomass material is burnt in a constant volume bomb in presence of oxygen The heat liberated is absorbed by known weight of water It is a measure of heating value when combustion is taking place at constant volume and the water formed during combustion or present as moisture in the biomass is condensed The latent heat of vaporization of water is also taken into account and this heating value is usually referred as the higher heating value (HCV) In almost all the thermochemical conversion devices, operation occurs at constant pressure and vapors leave with flue gases without getting condensed The heating value under these conditions is called lower heating value (LCV) It is therefore, suggested that the LCV should be used in preference to HCV for the energy and mass balance, and other design and performance evaluation calculations for a thermo-chemical conversion device

1.3.1.2 Lower Heating Value

Knowing the elemental analysis and higher heating value of the biomass, the lower heating value can be determined It is usually 10 to 15% lower as compared to the higher heating value The lower heating value can be linked with the higher heating value by the following expression λ and Wf are the latent heat of vaporization of water and weight fraction of water formed during combustion process The lower heating values of selected biomass species are given in Table 1.2

Proximate analysis provides information on the combustion characteristics of biomass It

is a measure of fixed carbon (FC), volatile matter (VM), Ash (A) and Moisture (M) in the

biomass material and expressed as percent The term volatile matter and fixed carbon

does not have clear definitions The volatile matter of any substance in a broad sense is the fraction that is driven off by heating the sample to a specific time and temperature The total amount of volatile matter and its composition is the function of heating rate as well as the final temperature The volatile matter is an important parameter because it characterises the expected contamination of the raw gas with condensable vapours in any gasifier or pyrolysis equipment

Table 1.2 Ultimate analysis of selected fuels

Source: Pathak and Jain, 1984; Reed and Das, 1988

There are no standard techniques for the proximate analysis of biomass as yet, however, the most commonly adopted procedure for proximate analysis of coal outlined in

BS 1016 Part 3&4, 1973 are in use for the proximate analysis of biomass as well The biomass is placed in a muffle furnace at 915 oC for 7 minutes in a covered platinum crucible The moisture and VM and are driven off and the residue left after 7 minutes is the fixed carbon and ash

The most common constituents of ash are SiO2, Al2O3, Fe2O3, TiO2, CaO, MgO,

Na2O, K2O and SO3 as these minerals amounts to at least 95% of all minerals in the ash

It has been found that the most troublesome components of the ash are SiO2 and oxides

of alkali metals Na2O and K2O In most of the biomass SiO2 content amounts to above 50% and can reach to extreme value of 97% in case of rice husk These components lower the ash melting temperature and the most dangerous is their tendency to vaporize

at temperatures usually obtained in gasifiers or combustion furnace The problem becomes even more severe when the biomass has sulfur and chlorine and the alkali metals react to form chlorides and sulfide and sulfates The melting temperature of these compounds is much lower and they also form eutectic mixtures having much lower melting temperature The melting point of SiO2 is fairly high i.e around 2350 oC but in most of the cases it melts at much lower temperatures

The vapors of molten ash reach the engine in extremely fine form (<0.1 micron) and are highly abrasive and can cause damage to the critical parts of the engine During thermal applications the ash vapors condenses on the cold boiler tube surface and reduce the heat transfer coefficient and tend to deteriorate the overall performance of the system

The difficulties in controlling slagging can be overcome by two totally different types of operation

For the determination of ash, biomass is heated in a tarred silica crucible in a muffle furnace at a temperature of 600 oC for 2 to 3 hours till a constant residual weight is obtained The constant weight residue is taken as ash in the biomass The percent ash content can be determined using the following expression

Knowing moisture content and combination of moisture and volatile matter, the volatile matter of the biomass can be estimated Also if ash and combination of ash and

FC are determined, fixed carbon content of the fuel can be estimated The proximate analysis is represented by the following expression

Proximate analysis of certain fuel materials is given in Table 1.3 The volatile matter of the biomass starts distilling off at moderate temperatures of 250-350 °C in any thermochemical conversion process The vapors thus formed consist of water, oils, tar and gases It is, therefore, obvious that biomass fuels having high volatile matter have tendency

to form higher tar during pyrolysis or gasification Most of the biomass materials have volatile matter content around 75-80% on dry and ash free basis Thus biomass tends to release high tar as compared to materials having low volatile matter such as charcoal during gasification

When all the volatile matter is driven off from the biomass, the residue left is fixed carbon and ash In a gasification process, the fixed carbon provides favorable environments where reduction reactions take place to form carbon monoxide, methane and hydrogen Thus biomass materials with higher fixed carbon are considered as better feed

weight of wet biomass x

Source: Pathak and Jain, 1984; Reed and Das, 1988

Ash is the inorganic matter in the biomass left after the volatiles, fixed carbon and moisture are driven off It contains varying quantities of oxides of silica, sodium, potassium, phosphorus, magnesium, iron etc Higher ash content in the biomass is coupled with the ash handling problems in a thermochemical conversion device Ash from some biomass material fuses at temperatures i.e 800-1200 oC which are usually attained in gasifiers or furnaces and tends to fuse and form large hard clinker of ash The fused ash from certain biomass gets vaporized at these temperatures which condenses on relatively low temperature surfaces such as boiler tubes and tends to plug the gas/air flow channels

in gasifiers and furnaces Knowledge of slagging behavior of the biomass ash is, therefore, essential before it is used as a feed stock for gasifier or furnaces Ash slagging temperatures of some selected biomass materials are given in Table 1.4

1.3.3 Thermogravimetric Analysis

In thermogravimetric analysis, the biomass is heated under controlled conditions of temperature and environment or reaction atmosphere Thermogravimetric analysis (TGA) provides information on weight change as a function of temperature and time

whereas differential thermogravimetric analysis (DTG) i.e rate of weight change with respect to time It also gives information on differential thermal analysis (DTA), the type

of reaction prevailing at a specific temperature i.e weather the reaction was exothermic

or endothermic The weight loss and temperature/time data can be used to work out quantities of volatile matter, char and ash in the biomass The data can further be used to compute the thermal degradation reaction kinetic parameters such as activation energy, order of reaction and pre-exponential factor

Table 1.4 Softening and melting temperature of ash from biomass

Biomass

Softening Temperature (°°°°C)

Melting Temperature (°°°°C)

Isothermal degradation is characterised by large samples, bigger size and is carried out in specially designed thermo balances The conditions prevailing in such equipment resemble with the actual conditions during combustion or gasification where

RT E

E RT

In the above equations:

Wo = Initial weight of sample, mg

W = Time dependent weight of

sample, mg

Wf = Final weight of the sample, mg

α = Fraction of A decomposed at any

time t

A = Pre-exponential factor, s-1

R = Universal gas constant

q = Linear heating rate °C min-1

E = Energy of activation, kJ mole-1

T = Absolute temperature, K

n = Order of reaction

The first term of right hand side of both the above equations tend to be reasonably constant Thus, a plot of left hand side against 1/T allows the activation energy to be determined from the slop E/R The pre-exponential factor A can be determined with E known from the above equations In all the determinations a prior knowledge of the value of the order of reaction is to be assumed

Jain et al (1996) reported the thermo gravimetric analysis of paddy husk, cellulose, and lignin under oxidative, intermediate (O2 5:N2 95%) and inert atmospheres at different linear heating rates (1 to 100 oC/min) The following observations are reported

1 Activation energy for thermal degradation of cellulose was the highest followed by paddy husk and lignin under similar conditions of environment and linear heating rates

2 Under oxidative environment, the activation energy was the highest followed by intermediate and inert reaction environments under similar conditions of linear heating rates and the biomass materials

3 With the increasing linear heating rates the activation energy in general decreased

4 Order of reaction was found to be a function of linear heating rate At lower heating rates the thermal degradation reactions followed the first order reaction mechanism

whereas at higher heating rates the appropriate order of reaction was 1.5 or 2 1.4 Chemical Analysis

Chemical analysis gives information about the chemical composition (cellulose, cellulose, pentosan lignin and alcohol benzene extractives) and elemental analysis (carbon, hydrogen, nitrogen, oxygen, sulfur, silica, sodium, potassium etc.) of biomass

hemi-1.4.1 Ultimate Analysis

Ultimate analysis gives information regarding the elemental composition of carbon, hydrogen, oxygen and nitrogen content of a biomass fuel Equipment for the analyses of carbon, hydrogen and nitrogen (CHN analyzer) are now available commercially Oxygen

is generally determined by the difference

The ultimate analysis does not reveal the suitability of biomass for gasification, combustion or any other process but is the main tool for the determination of

stoichiometric formula, stoichiometric air requirement and air fuel ratio, gas composition, temperature limits, gas production rate etc through a mass and energy balance over the thermochemical conversion processes It is also used to predict the lower heating value of the biomass Ultimate analysis and heating value of some selected fuel is given in Table 1.5 The data in the table is reproduced from Reed and Das (1987) and Jain (1997)

Table 1.5 Ultimate analysis of selected fuels

Source: Pathak and Jain, 1984; Reed and Das, 1988

The total carbon in the biomass is different from fixed carbon as determined by proximate analysis In order to avoid confusion, the total carbon may be split into base carbon and volatile carbon Base carbon represents the carbon that remains after devolatilization, whereas volatile carbon is defined as the carbon estimated from the difference between total carbon and base carbon Base carbon does not equal the fixed carbon as given by proximate analysis because the fixed carbon includes some other organic components also which have not been evolved during the process of devolatilization

Table 1.6 Chemical analysis of certain biomass

is a irregular polymer of phenyl propane unit, it tend to yield high tar proportion during thermal decomposition reactions Thus the biomass rich in lignin are known to generate producer gas with high tar during thermal gasification

The first two model correlates lower and higher heating values and ash content

of biomass It is assumed that the heating value of ash free biomass is constant and is a linear function of ash content The LCV or HCV obtained by these models is fairly in agreement with the experimental values with a variation of ± 2-3%

The third model predicts lower heating value knowing carbon hydrogen and oxygen content of the biomass In the models LCV and HCV, are lower and higher heating values (MJ kg-1) whereas A, C, O and H are the percent ash, carbon, oxygen and hydrogen of biomass on dry weight basis respectively For biomass, which is not fully characterized, these models can effectively be used to get first hand information of the characteristics of biomass

1.5.2 Stoichiometric Formula

Stoichiometric formula gives the atomic composition of carbon, hydrogen and oxygen in a biomass Knowing the elemental analysis of a biomass, its stoichiometric formula can be determined For any biomass if the stoichiometric formula is represented by C HxOy, where

x and y are atomic ratios of hydrogen and oxygen, x and y can be determined using the following expressions

x = H / (C/12)

y = (O/16)/(C/12)

The typical atomic ratios for biomass is CH1.4O0.6 and for coal CH0.9O0.1 Once we know the stoichiometric formula, the molecular weight and the stoichiometric air fuel ratio can be determined The Stoichiometric formula/values of x & y for certain biomass materials is given in Table 1.7

Table 1.7 Stoichiometric formula and air fuel ratio of certain biomass

1.5.2 Stoichiometric Air Fuel Ratio

Stoichiometric air fuel ratio is the theoretical air required for complete oxidation for a unit weight of the biomass The stoichiometric air fuel ratio is useful for the determination of air quantity requirement for furnaces or gasifiers and subsequently for designing air and gas handling system Using stoichiometric formula of biomass, the following procedure may be used to determine the stoichiometric air fuel ratio Combustion of a biomass material can be represented by the following reaction

CHxOy + n(0.21O2 + 0.79N2) → CO2 + x/2 H2O + 0.79 (n) N2

In the above equation air is assumed to have a molar composition as O2:N2::21:79 The moles of air in the reaction are represented by n Writing an oxygen balance over the above reaction:

y + 0.21 (2n) = 2 + x/2

If we substitute the values for x and y in the above equation number of moles of air required for complete oxidation of biomass material can be determined The stoichiometric air fuel ratio for biomass materials varies to a large extent i.e 3.34 m3/kg for paddy husk to 5.1 m3/kg for acacia auriculiformis (Jain, 1996, 1997) The air fuel ratio for certain biomass materials is given in Table 6

1.6 Conclusions

On the basis of information on characteristics of biomass some general classification regarding their suitability for different applications can be worked out Fuels with low ash content, high calorific value and density are suitable for gasification and fuel for furnaces Biomass with low ash slagging temperature are trouble some fuels High ash biomass coupled with poor flow properties such as paddy husk are not suitable for gasification in down draft gasifier with throat, however, it is good fuel for throat less and updraft gasifiers and furnaces Fuels with high volatile matter have tendency to generate considerable tar and are less suitable for updraft gasification High moisture in the fuel is not suitable regarding the application of fuel in gasifiers as well as furnaces Biomass materials with high cellulose content are suitable as feed stock for paper industry High cellulose materials are appropriate for alcoholic fermentation and anaerobic digestion as well High pentosan content in a biomass supports its use for furfural production High silica biomass such as paddy straw and paddy husk can be used to produce amorphous and precipitated silica

Biomass materials have certain limitations such as less density, high volatile matter, high ash content, hygroscopic nature etc But inspite of that there is no doubt that it has tremendous potential for various energy related applications It can be converted to better quality fuels such as producer gas, biogas, methanol, ethanol, tar, charcoal etc via thermochemical and biochemical conversion route It can be directly used as fuel for industrial boilers and domestic kitchens for thermal application Biomass also has potential as feedstock for proper and board, furfural, activated carbon, silica industries

References

1 Jain A.K (1996) Mid term review report of the AICRP project on RES Producer gas component School of Energy Studies for Agriculture, PAU Ludhiana

4 Kaupp A (1984) Gasification of rice hulls-theory and practice Published by GATE/GTZ, Germany

5 Kaupp A and Goss J.R (1984) Small scale gas producer engine system Published

by GATE/GTZ, Germany

6 Pathak B.S and Jain A.K (1985) Biomass Characteristics, Final report of the project Energy in Agriculture and first report of the School of Energy Studies for Agriculture PAU Ludhiana, 49-64

7 Reed T.B and Das A (1988) Handbook of biomass down draft gasifier engine systems SERI/SP-271-3022 DE88001135, UC Category: 245, USA

3500 MT, which will account for 20% of the total consumption and is analogous to the current global annual consumption of oil

Bio-energy is considered renewable due to its origin from and end in carbon dioxide, as a result of closed carbon cycle However, a large number of first generation technologies fail to meet the test of sustainability based on the criteria of ratio of renewable energy output to fossil energy input; as considerable amount of primary/secondary energy is needed in biomass process chain during cultivation, harvesting, transportation, conversion processes, supply chain, use of the products and disposal During production process, energy inputs are required for ploughing, sowing, fertiliser and pesticide production During production process, energy is required for pre-treatment, processing, purification of products As per sustainability criteria, it is not only the amount of energy but also the source of energy used for processing, which is important If sustainability criteria are not applied to biomass it will result in biodiversity loss from land use change, food insecurity, overuse of water, and mismanagement of soil Global warming concerns are becoming an overriding factor all over the world, resulting in a paradigm shift in the development of bio energy technologies This has created a new window of opportunity for the researchers for developing new technologies and modifying the old technologies Life cycle analysis for carbon and water footprints should be used to analyse the global warming impact of the product

Keeping in view the competition between food and fuel, selection of raw material for bio- energy should take in to consideration the fact that the first priority of biomaterials is for food, then animal feed and bio-energy is the last claim Food enjoys higher commercial value than bio- energy Hence, bio-energy has to be subsidised if it is

to compete with food Best option for the raw material for bio-energy is waste material from agriculture, animals, human, and non -edible oils etc It is estimated that more than 90 million tons of municipal solid waste is generated each year in India 40% to 60

% of this waste is compostable matter MNRE has estimated a potential of 2500 MW under Energy to waste programme

2.2 New Research opportunities in Bio Energy

2.2.1 Bio fuels

Alkali and acid (homogeneous and heterogeneous) catalysed esterification processes have been extensively used for the production of bio-Diesel Esterification Processes for oils containing high free fatty acid (non edible oils, animal fat, waste oil) are energy intensive Use of homogeneous and heterogeneous catalysed processes for transesterification suffer from heat transfer and Mass transfer limitations, as oil and alcohol are not completely miscible (Canakei and Van Gerpen, 2001; Freedman et al., 1986; Vicente et al., 2004) Use of Process intensification technologies such as ultrasonic and microwaves can overcome these problems It has been estimated that the use of microwave for transesterification of commercial seed oils with methanol in the presence of various catalysts gives yields greater than 97% with a reaction times of less than 2 minutes and are more energy efficient (Balat et al., 2008) Other intensification technologies such as static mixers, micro-channel oscillatory flow and cavitation are also very promising These can reduce molar ratio of alcohol to oil as well as energy inputs due to increase in heat and mass transfer rates

Use of enzymatic transesterification of triglycerides is environmentally more attractive as compared to conventional physiochemical methods (alkali and acid esterification) (Noureddini et al., 2005; Singh and Singh, 2010) High cost of enzyme is one of the limitations of this process This can be partially offset by immobilisation of the enzymes, which helps in the stability, recovery and reuse of lipases Different methods of immobilisation include; physical adsorption on solid support, Covalent bonding to a solid support and Physical entrapment within a polymer matrix (Noureddini et al., 2005) However, use of polymer matrix for physical entrapment of

lipase by sol- gel method appears to be better option due to ease of preparation and greater stability and activity of lipase over longer period A number of studies on

different lipases such as Mucor michi, Candida antartica, Pseudomonas cepacia,

Porcinepancreatic for different triglycerides and alcohols to optimise reaction

parameters such as molar ratios of reactants, kinetics, temperature, enzyme loading, stability and reusability Use of multiple enzymes in sequence for varied substrates has given encouraging results

However, biggest bottle neck in the use of enzymes for production of biodiesel lies in their high initial and replacement cost Research should focus on reducing enzyme cost and increasing enzyme activity for large scale economically viable industrial applications

2.2.2 Bio-oils from Micro Algae

Microalgae have emerged as a potential source of bio oil due to its high oil productivity

as compared to other crops (Nigam and Singh, 2011) as shown in Table 2.2

There are three main categories of micro algae namely: Diatoms, Green algae and Golden algae Each category has thousands of species

The diatoms (Bacillariophyceae) not only dominate the phytoplankton of the oceans, but are also found in fresh and brackish water Approximately 100,000 species are known to exist Due to its ability to grow in saline, there is a great potential for them

in the area with brackish water, where it is not possible to grow normal oil crops

The Golden algae have nearly 1000 species and are also quite similar to diatoms, with a more complex pigmentation system The golden algae produce natural oils and carbohydrates as storage compounds

The green algae (Chlorophyceae) grow quite abundantly, especially in freshwater The main storage compound for green algae is starch, although it is possible

to produced oil under certain conditions

There are number of critical areas which require in depth studies for large scale exploitation of this energy source These include; studies on algal biology and physiology, strain isolation, siting, resource management, regulation and policy, cultivation, harvesting, dewatering.oil extraction, conversion to fuels, co product production etc

Table 2.1 Conversion efficiencies of enzymatic esterification process used for different

oils (Singh and Singh, 2010)

(%) Solvent

2 Mowrah, Mango,

Kernel, Sal, C,-C, alcohols

M miehei (Lipozyme

isopropanol and 2-butanol

M miehei (Lipozyme

7 Sunflower Methanol; Ethanol P juorescens 3; 79; 82

None;

Petroleum ether; none

8 Palm kernel; Oil Methanol; Ethanol L cepucin (Lipase PS-30) 15; 72 None : None

9 Soyabean oil Methganol

Rhizomucor miehei

(Lipozyme IM-77) enzyme amount 0.9 BAUN

92.2 Molar ratio 3:4:1

10 Soyabean oil Methanol C antarctica lipase 93.8

> ½ molar equivalent MeOH

11 Sunflower oil Methanol Pseudomonas fluorescens

(Amano AK) (>90)

Oil : methanol (1: 4.5)

2.2.3 Bio- Ethanol

Bio Ethanol production through fermentation is an age old process Fermentation is

carried out with yeast strains such as Saccharomyees cerevisiae, S uvarum,

Schizosaccharomyces pombe, Kluyveromyces sp etc

Table 2.2 The oil productivity of different crops

Oil crops Productivity (gallons per acre per year)

to diversify the feedstock to agricultural residues

There is a need for the development of genetically modified stable yeast strains suitable for different feed stocks Stability of the yeast strain is essential for ensuring a prolonged continuous process, In order to improve stability of the yeast, new strains should have better pH, ethanol, osmo and temperature tolerance High osmo and ethanol tolerance will allow greater recycling rates of the stillage, thus reducing energy consumption This will also result in prolonged stable fermentation process increasing the overall productivity

Studies show that bacteria such as Zymomonas mobilis, Clostridium

thermosaccharolyticum, Thermoanaerobacter ethanolicus) can also be used for ethanol

fermentation (Nigam and Singh, 2011) Thermophilic bacterial fermentations would increase energy efficiency in distillation Many bacteria also have the capability of fermenting pentose sugars, thus increasing conversion efficiencies As studies are at bench scale, sustained efforts are need for the development of full-scale bacterial ethanol fermentation process

In addition residual stillage management is essential to further improve the energy efficiency and economics of the fermentation process It has been estimated that

nearly 75% to 100% of the overall process heat demand could be met from biogass produced by anaerobic digestion of stillage

2.2.4 Bio Gas Slurry Management

Management of biogas slurry from large plants is the major bottle neck in large scale propagation of this technology for power generation There is a chronic shortage of chemical fertiliser in the country A huge subsidy is given to the farmer so as keep the input costs low Large foreign exchange is spent on the import of raw material and fertiliser There is an urgent need to develop techniques for upgrading organic fertiliser, which could replace urea based chemical fertilisers Chemical fertilisers in general destroy soil flora and fauna, which keep the soil alive Organic fertiliser adds value to the crop and open export avenues In addition, it will reduce crippling subsidy burden of the government Value addition of the slurry will make biogas based power units economically more viable, resulting in achieving the targets of MNRE

2.3 Conclusions

Discussion given above shows that this is a unique period in the history of bioenergy research There is huge number of opportunities to develop clean and green bioenergy technologies with low carbon foot print There is an urgent need to create teams of scientists in the diverse areas of biotechnology, chemistry, chemical and mechanical engineering, microbiology etc to undertake focused and time bound programme for developing new cost effective bio-energy technologies NIRE can play a very import role in this direction This will help in achieving energy security for the country, especially in the rural areas At present nearly 70% of the rural population does not have access to commercial energy This is the main reason for deprivation and underdevelopment of the rural areas New bio-energy technologies can transform the face of rural India

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2 Canakei M and Van Gerpen J (2001) Transactions of the ASAE, 44:1429-1436

3 Freedman B., Butterfield R.O and Pryde E.H (1986) JACCS 63(10)

4. Nigam P.S and Singh A (2011) Progress in Energy and Combustion Science, 37.

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6 Singh S.P and Singh D (2010) Renewable and Sustainable Energy Reviews, 14:200-216

7 Vicente G., Martinez M and Aracil J (2004) Bioresource Technology,

92:297-305