biomass project

8/7/2019 biomass project

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INTRODUCTION

Life is but a continuous process of energy conversion and transformation. The

accomplishments of civilisation have largely been achieved through the increasingly efficient

and extensive harnessing of various forms of energy to extend human capabilities and

ingenuity. Lately there has been a growing concern about the negative environmental impacts

of fossil energy which drawn significant attention to renewable liquid biofuels as a way to

replace petroleum-based fuels (Krohn, McNeff, Yan, & Nowlan, 2010).Biomass is one of the

better sources of energy, large-scale introduction of biomass energy could contribute to

sustainable development on several fronts, environmentally, socially and economically

(hossain, Salleh, Boyce, chowdhury, & Naqiuddin, 2008). Biodiesel, a common term for long

chain alkyl esters, is a renewable, biodegradable, and non-toxic biofuel that shows great

promise to the environment (Lu, Zhai, Liu, & Wu, 2009). Biodiesel is derived from the

transesterification of mono-, di- and tri-acylglycerides (TAGs) and the esterification of free

fatty acids (FFAs) that occur naturally in biological lipids, such as animal fats and plant oils.

As a result, biodiesel has the potential to be a carbon neutral fuel (Krohn, McNeff, Yan, &

Nowlan, 2010). Furthermore, in comparison to petroleum diesel which is a major source of

greenhouse gas (GHG) (hossain, Salleh, Boyce, chowdhury, & Naqiuddin, 2008), biodiesel

emits lower levels of environmental pollutants including volatile organic compounds,

particulate matter, and sulphur-compounds during combustion (Krohn, McNeff, Yan, &

Nowlan, 2010). In this perspective, considerable attention has been given towards the

production of biodiesel as a diesel substitute.



Biomass Energy Biomass resources are agricultural and forest residues, algae and grasses, animal

manure, organic wastes, and biomaterials. The supply is dominated by traditional biomass

used for cooking and heating, especially in rural areas of developing countries. World

production of biomass, mostly wild plant growth, is estimated at 146 billion metric tons a

year worldwide (Demirbas, Chapter 9 Global Renewable Energy and Biofuel Scenarios,

2008). For fuels produced from biomass, various conversion routes are available that follow

from the different types of biomass feed stocks. These routes include direct conversion

processes such as extraction of vegetable oils followed by esterification (biodiesel),

fermentation of sugar-rich crops (ethanol), pyrolysis of wood (pyrolysis oil derived diesel

equivalent), and hydrothermal upgrading (HTU) of wet biomass (HTU-oil-derived diesel

equivalent). Another possibility is to produce liquid biofuels (methanol, DME, Fischer-Tropsch

liquids) from synthesis gas, which results from the gasification of biomass. In the future,

biomass has the potential to provide a cost-effective and sustainable supply of energy while at

the same time aiding countries to meet their greenhouse gas reduction targets.



Biodiesel

Properties of biodiesel

Biofuels are expected to reduce dependence on petroleum with its associated political

and economic vulnerability, reduce greenhouse gas emissions and other pollutants, and

revitalize the economy by increasing demand and prices for agricultural products.

Although most attention focuses on ethanol, interest in biodiesel is also increasing

(Demirbas, Chapter 9 Global Renewable Energy and Biofuel Scenarios, 2008) Biodiesel is the monoalkyl esters of long-chain fatty acids derived from renewable

feedstocks, such as vegetable oil or animal fat (Kakali Mukhopadhyay, 2005). It contains

very little sulfur, polycyclic aromatic hydrocarbons, and metals. Petroleum-derived diesel

fuels can contain up to 20% polycyclic aromatic hydrocarbons. For an equivalent number

of carbon atoms, polycyclic aromatic hydrocarbons are up to three orders of magnitude

more soluble in water than straight chain aliphatics. The fact that biodiesel does not

contain polycyclic aromatic hydrocarbons makes it a safe alternative for storage and

transportation (Palligarnai T. Vasudevan, 2008).

Advantages of biodiesel

Biodiesel can be used as a fuel for vehicles in its pure form, but it is generally be used

as a petroleum diesel additive to reduce levels of particulates, carbon monoxide,

hydrocarbons and air toxics from diesel-powered vehicles. Biodiesel is made from

biomass oils, mostly from vegetable oils.

It appears to be an attractive energy resource for several reasons. First, biodiesel is a

renewable resource of energy that could be sustainably supplied. It is understood that the

petroleum reserves are to be depleted in less than 50 years at the present rate of

consumption. Second, biodiesel appears to have several favourable environmental



properties resulting in no net increased release of carbon dioxide and very low sulfur

content. The release of sulfur content and carbon monoxide would be cut down by 30%

and 10%, respectively, by using biodiesel as energy source.

Using biodiesel as energy source, the gas generated during combustion could be

reduced, and the decrease in carbon monoxide is owing to the relatively high oxygen

content in biodiesel. Moreover, biodiesel contains no aromatic compounds and other

chemical substances which are harmful to the environment. Recent investigation has

indicated that the use of biodiesel can decrease 90% of air toxicity and 95% of cancers

compared to common diesel source. Third, biodiesel appears to have significant economic

potential because as a non-renewable fuel that fossil fuel prices will increase

inescapability further in the future. Finally, biodiesels better than diesel fuel in terms of

flash point and biodegradability (Moser, 2009). Sources of biodiesel

Crude Palm Oil (CPO)

Based on few criteria, palm oil is the most potential vegetable oil which can be used as raw

material to manufacture biodiesel (Surawidjaya & colleagues, 2003), and on the other hand the usage

of CPO consider to be the most wanted palm oil products for its cheap price and readiness for

downstream processing.

CPO is meant to anticipate oversupply. In the year of 2005, oversupply of CPO in Malaysia

reached 0.40 million tons. It is estimated that this amount will keep rising reaching 1.3 million tons in

2010. The data of 2007 shows that from about 3 million hectares of palm tree plantations, 6.7 million

tons of CPO is produced. Besides that, if the fuel subsidy is no more available, PAME (palm oil

methyl ester ± processed CPO which can be used as 100% biodiesel or a blend with other fuels) can

be able to substitute diesel oil that is readily available to be marketed with a competitive price. Figure

1 shown the average prices of the 4 quarters of the year 2006 and also the total average price of



di

¡ ¢ ¡ £ t¤

¡ ¥

¡ ¢ ¦ l § ¦ l¨ © il ¢ ¦

§ ¢ © duct¤

i £ compare to ot

er t pes of oil and fats in t

e nor t

estern

Europe market; C

recorded t

e lowest value af ter tallow wit

sli

t difference between t

em (478

and 451, respectivel

It is to be noted t

at t

e average pr ices of t

e 4t

quar ter increased rapidl

especiall

in

November it might due to the beginning of the winter in which the dependency on oil and fats as diet

and fuel for heat that increases the demand against the supply or it might be related to the end of the

economical year of the oils and fats market; in any case, the C

did not show rapid increase and

decrease in its value which show high sustainability with higher percentage for pr ice prediction and

this another advantage for C

along with its low pr ice and high yield which is not seen only in the

European region but also in the Malaysian region which is consider the leader in producing,

processing and expor ting palm oil & C

(Figure 2 and 3).

Figure 1: Average Pr ices of Selected Oils & Fats for 2006

(Nor th West Europe Market ± US$/Ton)

Note: R BD: Ref ined, Bleached & Deodorized.

Figure 2. Production of CPO for Malaysian Sates Year 2006 & 2007 (Year ly)

ource: MPOB

0200400600800

10001200

1st Quar ter Average

2nd Quar ter Average

3rd Quar ter Average

4th Quar ter Average

Total Average

Crude Palm OilRB! Palm OilRB

"

Palm OleinRB

! Palm Stear inPalm Kernel OilSoyabean OilCotton Oil

# roundnut Oil

Sunf lower Oil

T

ons



Talk ing about another aspect of CPO; fresh fruit bunches have to be harvested and

transpor ted to factor ies and have to be extracted within 24 hours. Otherwise the quality of extracted

palm oil will deter iorate. Given this fact, the factor ies have to be located close to the palm growing

areas. Crude palm oil (CPO) supplied by extracting factor ies has to be ref ined to obtain pure palm oil

suitable for consumption or for use as raw mater ial by the downstream industry. The palm oil, which

has undergone the ref ining process, is called RB$

oil (ref ined, bleached and deodor i% ed oil).

The requirement of petroleum in the country increased due to economy development, increase

population, and also the selling pr ice of petroleum product, which is relatively cheap. For that, if CPO

has to be used as diesel substitute, pr ice of the CPO should be considered along with the pr ices of the

Figure 3:

Production of

CPO for

Malaysian

Sates Year

2006 & 2007

(Monthly)

&

ource: MPOB



operational factors and material used in the process in comparing with the ones of the conventional

diesel.

Properties of CPO

The properties of the CPO alkyl ester (Table1) are found to be comparable with those of

petroleum diesel. The densities at 40ºC of methyl, ethyl and isopropyl esters of CPO were 0.855±

0.857 kg/L and, therefore, slightly higher than petroleum diesel, which slightly exceeds 0.820 kg /L.

This, however, is not important, as this would only cause a slight increase of fuel consumption.

The sulfur content of these esters are very low; a 0.04 wt% maximum as compared with 0.2

wt% presently found in Malaysian petroleum diesel. The exhaust emissions will therefore contain

very little SO2. The viscosities at 40ºC of alkyl esters of CPO were in the range of 4.4x10-6

± 5.2x10-6

m2/s, slightly higher than petroleum diesel fuel (4.4x10-6 m2/s). However, they are still in an

acceptable range and able to flow under warm weather conditions.

The pour points of alkyl esters of CPO range from 6 to 18.8 ºC. Pour point is defined as the

lowest temperature that the product still can be poured by gravity. Ethyl and isopropyl esters provide

better cold flow properties when compared to methyl esters.

Table1: Typical Fatty Acid Composition

of Alkyl Esters of CPO

Fatty acid composition (%) Alkyl esters of CPO

C12 0.3

C14 0.8

C16:0 44.3

C16:1 0.2

C18:0 5.0

C18:1 39.1

C18:2 10.1

C18:3 0.1



Production of Biodiesel Two major steps are necessary in order to produce biodiesel from microalgae. The

first step entails extraction of oil from microalgal cells, while in the second step the extracted

oil is transformed through reaction into biodiesel (hossain, Salleh, Boyce, chowdhury, &

Naqiuddin, 2008)

Oil Extraction Extracting oil from microalgae requires drying as the first step to reduce the water

content. Several methods have been employed to dry microalgae where the most common

include spray-drying, drumdrying, freeze-drying and sun-drying. Because of the high water

content of algal biomass sun-drying is not a very effective method for algal powder

production and spray-drying is not economically feasible for low value products, such as

biofuel or protein. After drying it follows the cell disruption of the microalgae cells for release of the

metabolites of interest. Several methods can be used depending on the microalgae wall and

on the product nature to be obtained either based on mechanical action (e.g. cell

homogenizers, bead mills, ultrasounds, autoclave, and spray drying) or non-mechanical

action (e.g. freezing, organic solvents and osmotic shock and acid, base and enzyme

reactions). Although different methods have been studied the best results were obtained from

autoclaved and mechanically disrupted biomass, with yield 3 times higher than with other

methods (Mata, Martins, & Caetano, 2010). Solvent extraction can be used along with expeller /press method, in which case more

than 95% of total microalgal oil can be extracted. According to Lu, Zhai, Liu, & Wu (2009)

the supercritical fluid extraction is more efficient than the other methods being able to extract

100% of microalgal oil

In supercritical fluid extraction method liquefied CO2 is used as the solvent for oil

extraction. The liquefied CO2 fluid is prepared by liquefying CO2 under pressure, and heating



it to the point that it has properties of both a liquid and a gas (Halim, Gladman, Danquah, &

Webley, 2011)

Patil, et al (2010) were able to directly convert wet algae paste (10% solids) to

biodiesel under supercritical methanol conditions. The single-step process favours the energy

requirements for biodiesel production by eliminating the needs for drying and extraction of

algal biomass and has the potential to provide an energy efficient and economical route to

algal biodiesel production.

Conversion of Oil to Biodiesel There are a number of ways to produce biodiesel from animal fat and vegetable oil.

Direct conversion, micro-emulsification, pyrolysis transesterification are the four techniques

applied to solve the problems encountered with the high fuel viscosity (Demirbas,

Comparison of transesterification methods for production of biodiesel from vegetable oils

and fats, 2008) Direct conversion The direct usage of the oils as biodiesel is possible by blending it with conventional

diesel fuels in a suitable ratio and these ester blends are stable for short term usages. The

blending process is simple which involves mixing alone and hence the equipment cost is low.

But direct usage of these triglyceric esters is unsatisfactory and impractical for long term

usages in the available diesel engines due to high viscosity, acid contamination, and free fatty

acid formation resulting in gum formation by oxidation and polymerization and carbon

deposition.



Pyrolysis Pyrolysis refers to chemical change caused by application of heat to get simpler

compounds from a complex compound. The process is also known as cracking. Vegetable

oils/animal oil can be cracked to reduce viscosity and improve cetane number. The products

of cracking include alkanes, alkenes, and carboxylic acids. Soyabean oil, cottonseed oil,

rapeseed oil and other oils are successfully cracked with appropriate catalysts to get biodiesel.

According to Milford & Fangrui (1999) using this technique resulted in good flow

characteristics because of the reduction in viscosity. Disadvantages of this process include

high equipment cost and need for separate distillation equipment for separation of various

fractions. In addition, the products obtained are similar to gasoline containing sulfur which

makes it less eco-friendly (Milford & Fangrui, 1999). Microemulsification Microemulsification is another technique that has been reported to produce biodiesel

and the components of a biodiesel microemulsion include diesel fuel, vegetable oil, alcohol,

surfactant and cetane improver in suitable proportions (Milford & Fangrui, 1999). Alcohols

such as methanol, ethanol and propanol are used as viscosity lowering additives, higher

alcohols are used as surfactants and alkyl nitrates are used as cetane improvers. Viscosity

reduction, increase in cetane number and good spray characters encourage the usage of

microemulsions but prolong usage causes problems like injector needle sticking, carbon

deposit formation and incomplete combustion ( (Milford & Fangrui, 1999) Transesterification The triacylglycerols are esters of long chain carboxylic acids combined with glycerol.

Carboxylic acids can be converted to methyl esters by the action of a transesterification

agent. The parameters affecting the methyl esters formation are reaction temperature,



pressure, molar ratio, water content and free fatty acid content (Georgogianni, Katsoulidis,

Pomonis, Manos, & Kontominas, 2009). Demirbas (2008) observed that increasing the reaction temperature had a favourable

influence on the yield of ester conversion. The yield of alkyl ester increased with increasing

the molar ratio of oil to alcohol. Transesterification consists of a number of consecutive,

reversible reactions. The triglyceride is converted stepwise to diglyceride, monoglyceride

and finally glycerol as shown in equestion 1-4 in which 1 mol of alkyl esters is removed in

each step.

Figure2.1: The Step Stepwise Conversion to Alkyl Ester

The formation of alkyl esters from monoglycerides is believed to be a step that

determines the reaction rate, since monoglycerides are the most stable intermediate

compound. Transesterification of fats and vegetable oils for biodiesel production, free fatty acid

and water always produce negative effects, since the presence of free fatty acids and water

causes soap formation, consumes catalyst and reduces catalyst effectiveness, all of which

result in a low conversion. Demirbas (2008) observed that by increasing the reaction

temperature, especially to supercritical conditions, it has a favourable influence on the yield

of ester conversion. The yield of alkyl ester increased with increasing molar ratio of oil to

alcohol



Table 3 shows a comparison between several methanolic Transesterification methods Table 3: comparison of various methanolic transesterification methods

Method Reaction Reaction temperature

(K) Reaction time(min) Acid or alkali catalytic

process 303±338 60±360

Boron trifluoride-methanol 360-390 20-50 Sodium methoxide-

catalysed 293-298 4-6 Non-catalytic supercritical

Methanol 523-573 6-12 Catalytic supercritical

Methanol 523-273 0.5-1.5 The transesterification is an equilibrium reaction, and the transformation occurs

essentially by mixing the reactants. In the transesterification of oils, a triglyceride reacts with

an alcohol in the presence of a strong acid or base, producing a mixture of fatty acids alkyl

esters and glycerol. The stoichiometric reaction requires 1 mol of a triglyceride and 3 mol of

the alcohol. However, an excess of the alcohol is used to increase the yields of the alkyl

esters and to allow its phase separation from the glycerol formed.

Alk ali catalytic Transesterification methods

In the alkali transesterification process sodium hydroxide (NaOH) or potassium

hydroxide (KOH) is used as a catalyst along with methanol or ethanol. Initially, during the

process, alcoxy is formed by reaction of the catalyst with alcohol and the alcoxy is then

reacted with any oil to form biodiesel and glycerol. Glycerol being denser settles at the

bottom and biodiesel can be decanted. This process is the most efficient and least corrosive of

all the processes and the reaction rate is reasonably high even at a low temperature of 60 °C.

There may be risk of free acid or water contamination and soap formation is likely to take

place which makes the separation process difficult (Demirbas, Comparison of

transesterification methods for production of biodiesel from vegetable oils and fats,

2008;Milford & Fangrui, 1999).



Acid catalysed transesterification methods Any mineral acid can be used to catalyze the process; the most commonly used acids

are sulfuric acid and sulfonic acid. Although yield is high, the acids, being corrosive, may

cause damage to the equipment and the reaction rate was also observed to be low (

(Demirbas, Comparison of transesterification methods for production of biodiesel from

vegetable oils and fats, 2008)).

Enzyme catalyzed processes It has been found that enzymes such as lipase can be used to catalyze

transesterification process by immobilizing them in a suitable support. The advantage of

immobilization is that the enzyme can be reused without separation. Also, the operating

temperature of the process is low (50 °C) compared to other techniques. Disadvantages

include inhibition effects which were observed when methanol was used and the fact that

enzymes are expensive (Ranganathan, Narasimhan, & Muthukumar, 2008).

The non-catalytic supercritical methanol transesterification The transesterification process can be carried out even without catalyst but with

considerable increase in temperature. Yield is very low at temperatures below 350°C and

therefore higher temperatures are required. However at temperatures greater than 400 °C

thermal degradation of esters occurred (Demirbas, Comparison of transesterification methods

for production of biodiesel from vegetable oils and fats, 2008). Recently it has been found

that alcohols in their supercritical state produce better yield and researchers have

experimented this process with methanol in its supercritical state.



Of all the methods mentioned above for production of biodiesel, only the alkali

process is carried out in an industrial scale.

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