The effect of various pre-processing and pre-treatment methods (Fig. 1) on the lignocellulosic matrix at the molecular level is not well understood. Applications of pre­processing methods such as size reduction or increasing porosity, and pre-treatment techniques such as steam explosion on agricultural biomass have demonstrated an improvement in pellet (compact) quality that can be attributed to the changes in the lignocellulosic components and distribution (Bagby, 1982; Focher et al., 1998). Therefore, it is critical to rapidly quantify the change in cellulose, hemicelluloses and lignin components of biomass due to application of pre-treatment methods.

Infrared spectroscopy has the potential to produce qualitative and quantitative analytical data for samples with minimum or no sample preparation, and at high speed and throughput (Adapa et al., 2011b and 2009; Budevska, 2002; Luypaert et al., 2003; Smola and Urleb, 2000; Tucker et al., 2000). Traditionally, chemical analyses of the individual components (e. g., lignin) of lignocellulosics have been performed by acid hydrolysis followed by gravimetric determination of lignin (Kelley et al., 2004). These methods can provide highly precise data. However, these methods are laborious, time-consuming, and, consequently, expensive to perform and sample throughput is limited.

Habrioux Aurelien1, Servat Karine1, Tingry Sophie2 and Kokoh Boniface1

1LACCO "Equipe E-lyse", UMR 6503 CNRS-Universite de Poitiers 2Institut Europeen des Membranes, UMR 5635, ENSCM-UMII-CNRS

France

1. Introduction

Nowadays, the development of stable devices capable of converting chemical energy into electrical one both to supply implantable devices and microelectronic apparatus is related in numerous papers (Bullen et al., 2006; Davis & Higson, 2007; Minteer et al., 2007). It is actually of great interest since it could be at the origin of new insight concerning the treatment of illness such as diabetes, deafness or heart disease (Heller, 2004; Katz & Willner, 2003). Besides it could also be a cheap solution to provide energy for microelectromechanical systems (Calabrese Barton et al., 2004) or to treat wastewater (Fishilevich et al., 2009). In the case where at least one of the catalyst used comes from biological resources (enzyme, microorganisms), these devices are called "biofuel cells". As any fuel cell, a biofuel cell consists of two separated, or not, electrodes, an anode and a cathode. The research topic concerning biofuel cells is very vast and can be divided in three subsections. The first one includes microbial fuel cells which are bio­electrochemical systems that drive a current intensity by mimicking bacterial interactions found in nature. The second one deals with enzymatic biofuel cells which use enzymes as catalysts. In this kind of device the specificity of enzymes leads to the non-separation of each compartment of the cell, allowing to minimize the size of the system (Heller, 2004). The last kind of biofuel cells deals with hybrid biofuel cells that result in the combination of an enzymatic catalyst with an abiotic one. In these applications, it is possible to vary the operating conditions of the cell (pH value, concentration of reactants) so as to increase the power density. This chapter will only be focused on the second and third kind of biofuel cells. For the latter devices, the ideal fuel is obviously glucose which is present in all organic tissues and the oxidant is dioxygen. Nowadays there is a need for improvement in what concerns both the lifetime (in the range of a few days) (Calabrese Barton et al., 2004) and the power density (classically lower than 1 mW cm-2) (Neto et al., 2010) of these apparatus. For this reason we describe herein both phenomena affecting stability and power density of biofuel cells and proposed solutions in terms of electrode assembly, catalysts used and design of the cells. Moreover, since the major way to increase enzymatic electrodes lifetime and efficiency is to improve the enzyme connection with the electrode surface, we will have a special look on the different immobilization techniques presently reported in literature. Besides, in the past few years it has noticeably been demonstrated that abiotic catalysts obviously increased the stability of the device (Kerzenmacher et al., 2008) and involved fast substrate conversion kinetic characteristics (Choi et al., 2009). Consequently, we will have a particular glance on new abiotic nanocatalysts and their use in hybrid biofuel cells.

However, in Colombia, promotion of biofuels production may represent several benefits: Energy sustainability: it will help to reduce the use of fossil fuels, thus protecting oil reserves. That is, a decreased risk of energy vulnerability. According to the Ministerio de Minas y Energia (English: Ministry of Mines and Energy) estimates show if new deposits are not found, known reserves will support the demand only for a few years. In this context, adding 10% of ethanol to gasoline helps to support fuel needs. Furthermore, Colombia has set the goal of increasing that percentage to 25% by 2020, which requires the new projects for ethanol production and the use of biomass sources other than sugar cane. In the short term the national program for Biofuels, seeks to improve fuel trade balance, and thus avoid wasting foreign reserves and spending at high prices by importing oil and petroleum products, that now tare close to 100 USD/barrel).

Environmental: biofuels are biodegradable, 85% is degraded in about 28 days.

Ethanol is a compound free of aroma, benzene and sulfur components, so the blending produces less smoke (particulates) and generate lower emissions (Stern, 2006). By using a 10% ethanol blending there is a reduction in CO emissions between 22% and 50% in carbureted vehicles, and a decrease of total hydrocarbons between 20% and 24% (Lopez & Salva, 2000).

With only a 10% blending of ethanol with gasoline, in new cars, 27% of carbon monoxide emissions decrease. In typical Colombian cars with 7-8 years of use it decreases 45%, and there is 20% reduction in hydrocarbons emissions. The effects of these reductions shall be reflected in the environmental emissions indices (Kumar, 2007), and in improve the citizens’ living conditions, for example Bogota where acute respiratory diseases are public health problems. Diesel blending decreases vehicle emissions such as particulate matter, polycyclic aromatic hydrocarbons, carbon dioxide and sulfur dioxide (U. S. Environmental Protection Agency, 2003).

Biodiesel is biodegradable, nontoxic and sulfur and aromatic components free, no matter the source of the oil used in its production. It reduces the soot emission in 40%-60%, and CO between 10% and 50%. Biodiesel can replace diesel (diesel fuel) without changes in ICE. Emissions with primary pollutants; with the exception of nitrogen oxides NOx. Despite these obvious benefits, there is not enough information about the solution to by-products and waste generated from biethanol-vinasses-and biodiesel-glycerin production processes, which are a source of future contamination if they are not properly disposed.

Agricultural development: biofuels production from agricultural raw materials, can guarantee both jobs growth and the possibility of crops diversification, including those for biofuel production. Export expectation, if there is pipe dream with Free Trades Agreement implementation, where Colombia supposedly is able to export bioenergy to poor energy countries, or that require large amounts of fuel for supporting economic growth.

Advantages of Colombia: As a reference, the abundance and variety of raw materials could be pointed out; several regions suitable for cultivation in all the country; guaranteed domestic market; government incentives and appropriate legal framework; high-yield crops, uninterrupted interest in research and development.

Based on the above results, we estimated the CO2 emission in conventional case and that of BT-SOFC case (see Fig. 12). In this study, the CO2 intensities in BT-SOFC case are included on the uncertainties of moisture content and a transportation distance (See section 3.3.1).

In the conventional case, the specific CO2 emission of 622.6 g-CO2/paprika was estimated. On the other hand, in the BT-SOFC case, the specific CO2 emission of 38.1 to 218.4 g — CO2/paprika was analysed, and CO2 reduction rate was 64.9% to 93.9%, respectively. Also, since the surplus electricity of 4,137 MWh/ yr would be generated through this system, the much CO2 reduction benefit might be obtained due to the alternation with the conventional electricity.

800

Conv. min ave max

<—————— ,—————— ‘

BT-SOFC case

4. Conclusions

As we described before, there is a good potential to install the renewable energy system such as a biomass energy system. In this section, we focused on the Blue Tower gasification process. In the near future, when we consider the promotion of eco-friendly business, we have to realize the sustainable business model which can be operated under a good cost condition and/or a reduction of CO2 emission. That is, we have to consider not only technological barrier but also the CO2 abatement effect. In this case, LCA methodology would be reasonable and necessary. Of course, the business scheme would be extremely significant.

In this section, we introduced two cases based on the biomass gasification system of BT process. In both cases, for instance, if we utilize the subsidies due to the central and/or local governments at the initial stage, or the regulation of feed-in tariff is available, the proposed business scheme would become increasingly competitive against the conventional business model. Also, recently, people have a great concern on the carbon-foot print based on LCA methodology. This means that there is potentiality to purchase the product with low-carbon emission. For the future, in order to mitigate GHG gases, we might have to consider the suitable technological system and the effective eco-socio system.

Enzymatic biofuel cells (EBFCs) utilize redox enzymes such as glucose oxidase (GOx), laccase as the catalysts that can facilitate the electron generation between substrates and electrode surface, hence generating the output potential. There are two types of electron transfer mechanisms which are direct electron transfer (DET) and mediator electron transfer (MET). In DET based EBFCs, the substrate is enzymatically oxidized at the anode, producing protons and electrons which directly transfer from enzyme moleculars to anode surface. At the cathode, the oxygen reacts with electrons and protons, generating water. However, DET between an enzyme and electrode has only been reported with several enzymes such as cytochrome c, laccase, hydrogenase, and several peroxidases (Schuhmann, 2002 and Freire et al., 2003). Some enzymes have nonconductive protein shell so that the electron transfer is inefficient. To overcome this barrier, MET was used to enhance the transportation of electrons. The selection and mechanism of MET in EBFCs are quite similar to those of MFCs that are discussed before. Similarly, there are still some challenges in using MET in EBFCs, such as poor diffusion of mediators and non-continuous supply. Therefore, modification of bioelectrodes to realize DET based EBFCs attracted most attention. In EBFCs system, power density and lifetime are two important factors which determine the cell performance in the application of EBFCs. Significant improvements have been made during the last decade (Katz et al., 2003; Calabrese et al., 2004; Zhu et al., 2007; Moehlenbrock & Minteer, 2008; Wang et al., 2009; Lee et al. 2010 and Saleh et al. 2011). Noticeably, these advancements have been mostly achieved by modification of electrode with better performance, improving enzyme immobilization methods as well as optimizing the cell configuration. Recent development of enzymatic biofuel cells is shown in Table 2.

The performance of electrodes for EBFCs mainly depends on: electron transfer kinetics, mass transport, stability, and reproducibility. The electrode is mostly made of gold, platinum or carbon (Katz & Willner 2003). Besides these conventional materials, biocompatible conducting polymers are widely used because they can facilitate electron transfer and co-immobilize the enzymes at the same time (Schuhmann & Muenchen, 1992; Haccoun et al., 2006 and Nagel et al. 2007). In order to maximize the cell performance, mesoporous materials have been applied in many studies because of their high surface areas thus high power density could be achieved. Moreover, many attempts using nanostructures such as nanoparticles, nanofibers, and nanocomposites as electrode materials have also been made to fabricate electrodes for EBFCs. The large surface area by using these nanostructures leads to high enzyme loading and enables to improve the power density of the cells. Recently, one of the most significant advances in EBFCs is electrode modification by employing carbon nanotubes. (Wang et al.2009; Lee et al. 2010; Tanne et al. 2010 and Saleh et al. 2011.) Several research activities have addressed the application of single wall carbon nanotube hybrid system. The oriented assembly of short SWNT normal to electrode surfaces was accomplished by the covalent attachment of the CNT to the electrode surface. It was reported that surface assembled GOx is in good electric contact with electrode due to the application of SWNT, which acted as conductive nanoneedles that electrically wire the enzyme active site to the transducer surface. Other studies have been reported on improving electrochemical and electrocatalytic behavior and fast electron transfer kinetics of CNTs. Improved enzyme activity was observed in comparison to similar enzyme-containing composites without using SWNTs. It was discussed that the application of SWNTs, which

possesses a high specific surface area, may effectively adsorb enzyme molecules and retain the enzyme within the polymer matrix, whereas other forms of enzyme-composites may suffer from enzyme loss when they were placed in contact with aqueous solutions. Although recent advancement in modification of electrodes appears to be promising due to the improvement of cell performance obtained, biocompatibility and nanotoxicity need to be further studied and addressed.

Successful immobilization of the enzymes on the electrode surface is considered as another critical factor that affects cell performance. The immobilization of enzyme can be achieved physically or chemically. There are two major types of physical methods, physical absorption and entrapment. The first one is to absorb the enzymes onto conductive particles such as carbon black or graphite powders. For example, hydrogenase and laccase were immobilized by using physical absorption on carbon black particles to construct composite electrodes and the EBFCs could continuously work for 30 days. Another physical immobilization method is based on polymeric matrices entrapment, which usually shows more stabilized enzyme immobilization (Mano et al., 2002; Mano et al., 2003, Heller, 2004 & Soukharev et al., 2004). For example, Soukharev utilized redox polymers to fabricate enzymatic biofuel cells system. The electrodes were built by casting the enzyme-polymer mixed solution onto 7 pm diameter, 2 cm length carbon fibers. It showed that the glucose — oxygen biofuel cell was capable of generating a power density up to 0.35 mW/ cm2 at 0.88 V (Soukharev et al., 2004). Compared with the physical immobilization which is unstable during the operation, the chemical immobilization methods with the efficient covalent bonding of enzymes and mediators are more reliable. Katz et al. reported a biofuel cell using co-immobilized enzyme-cofactor-mediator composites on metal electrodes to functionalize the electrode surface with a monolayer then integrate with enzymes via bioaffinity (Willner et al., 1998; Katz et al., 2001 and Katz et al., 2003). Another example is that a redox monolayer was covalently grafted with pyrroloquinoline quinone (PQQ) to Au-electrode. Then GOx-FAD electrode was assembled with PQQ as mediators (Willner et al., 1996). Other widely used materials to functionalize electrode surface have also been reported, such as nitrospiropyran (Blonder et al., 1998), rotaxane (Katz et al., 2004), C-60 (Patolsky et al., 1998) and Au nanoparticles (Xiao et al., 2003).

Rapid development on EBFCs has been achieved in the past decade with the arised demands for reliable power supplies for implantable medical device. It has shown particular advantages over conventional batteries because of the specific biocatalysts and the possibility of miniaturization. However, there are still challenges for further development of long term stability of the enzymatic bioelectrodes and efficient electron transfer between enzymes and electrode surfaces. Recent efforts have been given to protein engineering, reliable immobilization method and novel cell configuration.

The behaviour of automotive diesel fuel at low ambient temperatures is an important quality criterion, as partial or full solidification of the fuel may cause blockage of the fuel lines and filters, leading to fuel starvation and problems of starting, driving and engine damage due to inadequate lubrication. The melting point of biodiesel products depend on chain length and degrees of unsaturation, with long chain saturated fatty acid esters displaying particularly unfavourable cold temperature behaviour.

2. Conclusion

Biodiesel is an important new alternative biofuel. It can be produced from many vegetable oil or animal fat feedstocks. Conventional processing involves an alkali catalyzed process but this is unsatisfactory for lower cost high free fatty acid feedstocks due to soap formation. Pretreatment processes using strong acid catalysts have been shown to provide good conversion yields and high quality final products. These techniques have even been extended to allow biodiesel production from feedstocks like soapstock that are often considered to be waste. Adherence to a quality standard is essential for proper performance of the fuel in the engine and will be necessary for widespread use of biodiesel.

3. Acknowledgment

We acknowledge the Faculty of Agricultural Engineering (FEAGRI/UNICAMP)), the Food Technology Institute (ITAL), the State of Sao Paulo Research Foundation (FAPESP) and the

National Council for Scientific and Technological Development (CNPq) for their financial

and technical support.

Prior to the availability a fully sequenced genome, the genetics of D. salina were explored for useful elements such as regulatory sequences of highly expressed genes. Highly active endogenous promoter and 3′-untranslated region (UTR) pairs are of particular interest and significance to expressing transgenes in Dunaliella. Recent publications describing the use of the actin, rbcS, carbonic anhydrase, and ubiquitin promoters (Jiang et al., 2005; Walker et al., 2004; Chen et al., 2009) and nitA 3′-UTR (Li et al., 2007; Xie et al., 2007) are the basis for many of the pioneering attempts to genetically engineer D. salina, including the work presented hereafter.

3.1 Materials and methods

3.3.1 Microalgal cell culture

D. salina strains CCAP 19/18 and UTEX 1644 were obtained from the Culture Collection of Algae and Protozoa (UK) and the Culture Collection of Algae at University of Texas at Austin, respectively, and maintained on sterile agar plates (1.5% w/w) containing 1 M NaCl Dunaliella medium (Weldy et al., 2007). Cells were cultivated photoautotrophically in 1-L glass Fernbach flasks at 27° C (± 1) using 1 M NaCl Dunaliella medium (DM). Each axenic batch culture was inoculated with 10 ml of exponentially growing cells (1 x 106 cells ml-1), constantly stirred, bubbled with sterile air, and illuminated with cool-white fluorescent bulbs at an intensity of 80 pE m-2 s-1.

Methyl acetate is produced industrially by methanol carbonylation in the acetic acid production processes. Methanol carbonylation reaction is a well known reaction since Monsanto in 1970 performed it in liquid phase using a rhodium-base catalytic system. which was later acquired and optimized by Celanese. Such system had been preceded by a cobalt — based system developed by BASF, which suffered from significantly lower selectivity and the necessity for much harsher conditions of temperature and pressure. Although the rhodium catalysed system has much better activity and selectivity, the R&D has continued for new catalysts which improve efficiency even further. The strategies employed have involved either modifications to the rhodium-based system or insertion of another metal, eventually Iridium (Haynes, 2006). In the homogenous system, acetic acid was used as solvent, so esterification leads to substantial conversion into methyl acetate. Methyl acetate formation is facilitated by the methyl iodide used in carbonylation as a mediator. Heterogenous systems for methanol carbonylation have been suggested for several years. Research has been primarily focus on two possible catalysts for this reaction: 1) rhodium supported polymers (Acetica process as an example) or 2) zeolites and a variety of metals supported on activated carbon (Merenov and Abraham, 1998). The choice of the support seems to play an important role in the activity of the catalyst (Yashima et al., 1979). Another way to produce methyl acetate is by an esterification reaction. Eastman Chemical Company, produced methyl acetate by the esterification of methanol with acetic acid in a reactive distillation column.

This company claimed the first commercial plant of reactive distillation (Zoeller, 2009). As illustrated by figure 7, in the reactive distillation there are three sections in the column, water/methanol stripping zone in the bottom, a reaction zone in the center, and methyl acetate enriching at the top. Descriptively, methanol (b. p. 65°C) is added at the bottom of the reaction zone and acetic acid (b. p. 118°C) and acid catalyst are added at the top of the reaction zone.

As methanol ascends up the column it encounters a consistently richer acetic acid concentration, which drives the equilibrium toward the products and prevents methanol from leaving column. Likewise, as acetic acid descends down the column, it also encounters a continuously enriched stream of methanol, which also pushes the equilibrium toward products and prevents acetic acid reaching the bottoms of the column. However, the acetic acid also serves as extractant for water, breaking the various azeotropes. A short section is left at the base of the distillation column to strip all the methanol and a short section is added at the top of the column to enrich methyl acetate and prevent acetic acid from being entrained as the product is distilled overhead in the column. By properly balancing the addition rates, the reaction provides methyl acetate in 100% yield based on both acetic acid and methanol.

Enerkem Inc. has focused on the new gas phase approach to the carbonylation reaction. As acetic acid is not the desired end product of the carbonylation, the reaction conditions have been tailored to favour the methyl acetate directly according to the equation:

2CH3OH + CO = CH3COOCH3 +H2O -138.08 KJ/mol (19)

This is advantageous for Enerkem Inc. since it reduces by one step their process leading to ethanol. Forcing the reaction towards methyl acetate also facilitates a strategy based on gas phase reactor. In the process, the methanol carbonylation is carried out maintaining methanol in the vapor phase using a fixed bed packed a rhodium-based catalyst. The methanol is vaporized under pressure and mixed with the CO-rich gas prior to flowing through the reactor. The methanol to CO molar ratio is comprised between 1 and 4. Methyl iodide (co-catalyst and mediator) is added to the system at a suitable mol ratio relative to methanol. The operating conditions are such that the GHSV (based on CO) varies up to 2,000 h-1. At temperature comprised between 170 to 300°C and total pressure from 10 to 50 atm, it is found that the CO is converted at rate near 100% when the methanol:CO ratio is up to 2 (Chornet et al., 2009).

Lope Tabil1, Phani Adapa1 and Mahdi Kashaninejad2

1Department of Chemical and Biological Engineering, University of Saskatchewan 2Department of Food Science & Technology, Gorgan University of Agricultural

Sciences and Natural Resources Gorgan,

1Canada

2Iran

1. Introduction

1.1 The need for densification

Agricultural biomass residues have the potential for the sustainable production of bio-fuels and to offset greenhouse gas emissions (Campbell et a!., 2002; Sokhansanj et al., 2006). Straw from crop production and agricultural residues existing in the waste streams from commercial crop processing plants have little inherent value and have traditionally constituted a disposal problem. In fact, these residues represent an abundant, inexpensive and readily available source of renewable lignocellulosic biomass (Liu et al., 2005). New methodologies need to be developed to process the biomass making it suitable feedstock for bio-fuel production. In addition, some of the barriers in the economic use of agricultural crop residue are the variable quality of the residue, the cost of collection, and problems in transportation and storage (Bowyer and Stockmann, 2001; Sokhansanj et al., 2006).

In order to reduce industry’s operational cost as well as to meet the requirement of raw material for biofuel production, biomass must be processed and handled in an efficient manner. Due to its high moisture content, irregular shape and size, and low bulk density, biomass is very difficult to handle, transport, store, and utilize in its original form (Sokhansanj et al., 2005). Densification of biomass into durable compacts is an effective solution to these problems and it can reduce material waste. Densification can increase the bulk density of biomass from an initial bulk density of 40-200 kg/ m3 to a final compact density of 600-1200 kg/ m3 (Adapa et al., 2007; Holley, 1983; Mani et al., 2003; McMullen et al., 2005; Obernberger and Thek, 2004). Biomass can be compressed and stabilized to 7-10 times densities of the standard bales by the application of pressures between 400-800 MPa during the densification process (Demirbas and Sahin, 1998). Because of their uniform shape and size, densified products may be easily handled using standard handling and storage equipment, and they can be easily adopted in direct-combustion or co-firing with coal, gasification, pyrolysis, and utilized in other biomass-based conversions (Kaliyan and Morey, 2006a) such as biochemical processes. Upon densification, many agricultural biomass materials, especially those from straw and stover, result in a poorly formed pellets or compacts that are more often dusty, difficult to handle and costly to manufacture. This is caused by lack of complete understanding on the natural binding characteristics of the components that make up biomass (Sokhansanj et al., 2005).

Patanjali Varanasi1,23, Lan Sun123, Bernhard Knierim12, Elena Bosneaga24, Purbasha Sarkar24, Seema Singh13 and Manfred Auer124 1Joint BioEnergy Institute, Physical Biosciences Division Lawrence Berkeley National Laboratory, Emeryville, CA 2Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 3Sandia National Laboratories, Biomass Science and Conversion Technology Department, Livermore, CA 4Energy Biosciences Institute, UC Berkeley, CA

United States

1. Introduction

The decreasing availability and the increasing demand for fossil energy sources as well as concerns of irreversible climate change have sparked a quest for alternative energy sources, including carbon-neutral transportation fuels. One such alternative to fossil fuels is biofuel produced from currently unused plant biomass. Since lignocellulosic biomass — unlike corn­starch — cannot be used as a food source for humans it constitutes an ideal source for the production of biofuels. Currently, the production of biofuels from this unutilized biomass is not economically viable and crippled due to high costs involved in the conversion of biomass to sugars, and the limited repertoire of current generation microbes to produce a host of necessary transportation fuels beyond the simple fermentation into ethanol. Recently extensive research efforts are underway to overcome the bottlenecks for an economically viable lignocellulose biofuel industry. Advances must be made in the area of feedstocks engineering, optimization of deconstruction processes, including chemical, enzymatic or microbial pretreatment and saccharification approaches, as well as in the area of fuels synthesis, and require a variety of biophysical approaches, some of which are discussed here in more detail.

2. ThermoGravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC)

Thermogravimetric analysis is a thermoanalytical technique that measures the change in mass of a substrate as a function of temperature. The temperature of the sample and a blank are increased/decreased at a constant rate and the change in weight is measured as a function of sample temperature. As these experiments are highly temperature sensitive they are conducted in highly insulated chambers. The sample holders used in TGA experiments have to be highly conducting to avoid any lag between temperature measured outside and

inside the sample holder. There is practically no sample preparation required and the technique can be used for solids or liquids or a mixture of both. A small mass of the sample (<10 mg) is weighed and its mass change is measured against the mass change of an empty sample holder. The sample holders come with and without a hole in the lid thus allowing (or not) the flow of gases. The TGA experiments may be conducted under either inert (Nitrogen or Argon) or under oxidative conditions (Oxygen or Air). The decrease or increase in weight of the sample as the temperature is increased may indicate the loss of the material due to vaporization, decomposition or oxidation. The weight loss curve generated by the TGA instrument is representative of this mass loss (or increases) as a function of temperature changes. A derivative of the weight loss curves is usually used to easily read the TGA curves. The differential thermogravimetric (dTG) curves are useful for finding the temperature of vaporization or decomposition of both pure compounds and mixtures. TGA curves taken under different temperature ramp rates are used to find the order and activation energies of the decomposition reactions. TGA curves may also be used to find the total moisture content of the samples based on the weight loss in the region where water evaporates (80°C to 120°C). TGA/DSC techniques are particularly useful for mixtures with different constituents. Based on the temperature at which each of the constituents decompose or vaporize we may define weight loss region for each of the constituents. We may then use weight percent loss in each region to find the composition changes of the individual constituents in the original sample.

Differential scanning calorimetry (DSC) is also a thermoanalytical technique and is often used in conjunction with TGA. It measures the energy required to increase or decrease the sample temperature against a blank. Like TGA this technique also requires minimum sample preparation and can be used for solid, liquids or a mixture of both. Similar sample holders and similar sample weights are used in DSC as in TGA. Experimental conditions like, temperature ramp rate and gaseous atmosphere can be changed based on the kind of analysis. A DSC cure is highly data-rich as it gives us crucial information such as enthalpy of melting, boiling, decomposition and oxidation. By comparing both TGA and DSC curves one can determine the temperature at which the system boils, decomposes or oxidizes. An endothermic mass loss can be attributed to boiling or endothermic decomposition. An exothermic mass change is usually due to exothermic decomposition or oxidation of the substrate. Thus, DSC data is also used to find the caloric value of the decomposition and oxidation reactions. DSC data is used to find the endothermic energy required for dehydrating a sample in the moisture loss region. Such data may be used to find if the moisture is physically absorbed to the substrate or is chemically complexed with the substrate. In case of polymer substrates, DSC curves may also be used to find the glass transition temperatures and thus degree of polymerization of the samples (DP) (Couchman 1981). Amorphous to crystalline transitions can also be determined based on the temperature of weight loss and the enthalpy of decomposition. Amorphous substrates decompose at lower temperature when compared to crystalline substrates of the same material (Kim, Eom, and Wada 2010). Amorphous materials undergo crystallization before melting. Based on ratio of the energy required for crystallization and the energy required for melting we may also find the percent crystalline material in the sample.

TGA/DSC techniques are particularly useful for biomass characterization as biomass is a complex mixture of polymers (cellulose, hemicelluloses and lignin). Serapiglia et al. (2008); Kaloustian et al. (2003); Jaffe, Collins, and Mencze (2006) have shown that the dTG curves
from biomass can be divided into three weight loss regions for hemicelluloses followed by cellulose and lignin. TGA is a very sensitive technique and can be used to differentiate between mutants of similar kinds of feedstocks. Serapiglia et al. (2008) have used high throughput TGA to find the differences between various mutants of shrub willow. TGA was also used to find the total lignin content of various feedstocks (Ghetti et al 1996). TGA/DSC curves were used to differentiate and understand the effects of dilute acid steam explosion on Eucalyptus (Emmel et al. 2003). They reported that lignin fragmented and recondensated during the process. A decrease in softening temperature was reported for steam exploded bamboo lignin (Shao et al. 2009), resulting in a lower molecular weight polymer. DSC was also used to differentiate between hardwoods and softwoods, based on the glass transition temperature of the lignin extracted from the woods (Kubo and Kadla 2005). Lignin decomposition by white-rot fungi was studied using DSC (Reh et al. 1987). They show that as lignin-carbohydrate bonds are broken the peaks in each region separate and become sharper. The differences between lignin carbohydrate linkages in biomass can also be found using DSC (Reh et al. 1987; Tsujiyama and Miyamori 2000). Along with these kinds of qualitative measurements, TGA and DSC can be used to calculate the enthalpy, activation energy (Flynn and Wall 1966; Paul et al. 2010) and the order of the reaction as well as the percent cellulose crystallinity of the samples.