biofuels - production and methods

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Review of existing and emerging technologies

for the production of biofuels in

developing countries

Philippe Girard and Abigal Fallot

Biomass Energy Research Unit, Forest Department of CIRAD

Centre de Coopration Internationale en Recherche Agronomique pour le Dveloppement (CIRAD)

73, rue Jean-Franois Breton - TA 10/16 - 34398, Montpellier Cedex 5 - France

E-mail: [email protected]

The present energy crisis has reactivated worldwide the interest in biofuels, particularly in devel-

oping countries that are dependent on import of petroleum products and may have, in terms of

land availability and climatic conditions, the potential for large-scale biomass production. Various

routes are possible for converting biomass into transport fuel. Technologies and processes are de-

scribed and fuel properties compared to those of the fuels they are supposed to substitute. Emphasis

is given to the first generation biofuels, biodiesel and bioethanol, as the second-generation biofuels

using whole biomass are still at an early stage of development and would require long and strong

public support to be available on an industrial scale. A big consideration is biomass supply, as these

resources may affect land availability and competition with food and feed production. These aspects

are addressed in a separate paper. Small-scale stand-alone power generation is briefly discussed,

as is the possible use of straight vegetable oil (SVO). The main barrier to the development of biofuel

is economic. That is why cost considerations are developed. However, assessing the cost of biofuel

is not easy because the feedstock biomass accounts for the largest part of the total costs and therefore

the total cost depends greatly on national policy and subsidy frameworks. The paper concludes withsome socio-economic considerations and discusses opportunities for implementing transport biofuel

programmes in developing countries.

1. Introduction

World energy supply is largely dependent on conventional

petroleum products and most of the expected increases in

oil demand in the medium term will come from the trans-

port sector, with the largest growth from developing coun-

tries. Consequently, the transport sector will become

responsible for about one-third of the worlds future

greenhouse gas (GHG) emission growth [IEA, 2004] and

oil prices may reach dramatically high levels.A number of alternative fuels for transport are poten-

tially available and are currently being used or investi-

gated at different stages of development worldwide (see

Figure 1). Today, the term biofuels mostly refers to etha-

nol and esterified vegetable oil. New products such as

methanol, dimethyl ether, Fischer-Tropsch (FT) diesel and

ethanol from lignocellulosic feedstock, called second gen-

eration biofuels, are benefiting from active R&D pro-

grammes. Long-term investigation deals with third

generation biofuels, such as hydrogen for fuel cells.

Transport biofuel production pathways are numerous

and technology choices are closely linked to the biomasstype considered. Nevertheless, most biofuels can have the

interesting advantages of:

being compatible with existing vehicle engines, in con-

trast to compressed or liquefied natural gas; and

being amenable to blending with conventional fuels

within existing equipment and infrastructure.

Upstream, biomass is a local resource that can contribute

to the diversification of energy supply and potentially cre-

ate employment for cultivation, harvesting, transport and

fuel preparation. Well-managed, biomass yields carbon

emission-saving fuels when substituted for fossil fuels.

Amongst renewable energy sources, biomass appears to

be the most important in terms of technical and economicfeasibility. It is therefore today considered a major future

energy source for development and industry, arousing

growing interest worldwide, not only for use in transport.

Improving energy security and reducing CO2emissions

are primary goals for the development of alternative fuel

policies. In many developing countries, saving oil and in-

dependence from it may often take precedence as petro-

leum product imports are a major source of foreign

currency expenditure. Large natural gas reserves or the

availability of land for energy crops in a given region may

influence fuel and, consequently, technology choices. Dif-

ferent lobbies, including engine manufacturers and oilcompanies, do play significant roles favouring minimal or

no modification of the existing types of engine or refuel-

ling infrastructure. Government willingness to support lo-

cal industry and agriculture will also influence these

Energy for Sustainable Development Volume X No. 2 June 2006

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choices. As drivers for the development of alternatives to

conventional transport fuel are often not technical, it is

difficult to assess technology development trends solely

on the basis of their technical characteristics.

The developing world encompasses countries of very het-

erogeneous characteristics, particularly where biofuel pro-

duction opportunities are concerned. Indeed, population

density and dynamics, climatic conditions, available infra-

structure and capital, land ownership patterns, etc., vary

widely from country to country. However, some common

characteristics underlie the potential importance of biofuel

production and technology choices in developing countries.

The resource: developing countries with high levels of

biomass productivity are mostly tropical. In most de-

veloping countries, agriculture is the sector on which

the major part of the population depends.

The energy sector: energy consumption levels are low,or even very low, but they are increasing rapidly with

standards of living and industrialization. Therefore the

lock-in effect in favour of fossil fuel may be easier to

overcome for alternative energy sources, such as bio-

fuels. For this reason, the technology review presented

in this paper is not limited to first generation biofuels

such as ethanol from sugar cane or biodiesel from oil

crops. It also considers more innovative second gen-

eration biofuels offering wider prospects in the short

to medium term (within ten years) and possibly leap-

frogging, instead of following step by step, paths taken

by industrialised countries. Poverty challenge: given their immediate priorities and

levels of unsatisfied basic needs, developing countries

are probably not in a position to invest in very long-

term R&D from which results cannot be expected

before decades, even if some third generation biofuel

technologies may offer more definitive solutions to en-

ergy problems.

Accounting for these specificities, the purpose of this pa-

per is to give an overview of feedstock and process tech-

nologies for biofuel production with a focus on

established processes and considerations for emerging

technologies of potential interest to developing countries.

2. Biomass feedstock for biofuel processes

Biomass that can be converted to biofuels is of two dif-

ferent origins:

conventional agricultural products such as oilseeds and

sugar- or starch-rich crops; and

lignocellulosic products and residues.

A brief description of the most important feedstocks po-

tentially available in tropical countries is given in the fol-lowing sections. It should be noted that when taking into

account these resources some may have alternative uses

and their real availability for energy uses may be limited.

2.1. Conventional agricultural products

2.1.1. Sugar-rich crops

Ethanol is traditionally produced from the fermentation

of glucose (sugar) by yeast. Therefore sugar cane and

sugar beet, which both contain a substantial amount of

sugar, constitute the main source of ethanol production

worldwide, though the US production from maize is

nowadays almost as important in volume as that from

sugar cane in Brazil. Other suitable sources of sugar aremolasses (a by-product of the sugar industry) and sweet

sorghum. According to IEA [2004], about 60 % of the

worlds ethanol production comes from sugar crops and

molasses, mainly from sugar cane. The Centre-South

Figure 1. Production pathways for transport fuels from alternatives to crude oil, adapted from [Van Thuijl et al., 2003]. HTU (= hydrothermal upgrading)is a registered trademark for a new second-generation biofuel production process being developed in the Netherlands.


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region of Brazil, benefiting from good soils and adequate

rainfall, is the largest (80 to 85 % of the total Brazilian

production [Moreira, 2003]) region of sugar cane and

ethanol production with the worlds cheapest production

cost, where almost half of the sugar cane production is

transformed into ethanol.One advantage of sugar cane is that it is a well-established

crop in terms of cultivation, breeding, harvesting and proc-

essing. When operated at high efficiency, sugar cane mills

and associated distilleries can be a source of extra electricity

to be sold to the grid or contributing to rural electrification.

As access to electricity is also a major challenge for many

developing countries, sugar cane offers this opportunity of

polygeneration. Many developing countries are already pro-

ducing sugar cane. Therefore, the Brazilian production

framework is a potentially interesting object of replication.

However, crop requirements (water and soil) limit the land

available for sugar cane and land availability will certainlyconstitute a critical limiting factor.

Sugar beet is used in Europe [Poitrat, 2005], with a

feedstock cost much higher than that of sugar cane. The

uses of other sources of biomass such as fruits and to a

certain extent sweet sorghum (with present varieties)

might be limited by cost-effectiveness. Research is still

needed to develop their cultivation.

2.1.2. Starch-rich crops

Because starch is easily converted into sugars, the largest

part of ethanol produced in OECD (Northern) countries

comes from cereals. The potential feedstock includes

maize, wheat, potato, cassava, and sweet potato. Maize,

which accounts for 90 % of US ethanol production, is by

far the largest feedstock used for ethanol production

worldwide [ERFA, 2005]. In the conversion of grain to

ethanol, only the starchy part of the feedstock is used,

which represents a relatively small percentage of the total

plant mass, in particular when compared to the cellulosic

part (husk and straw for wheat). Even starchy grain alone

when used for ethanol production results in numerous co-

and by-products such as animal feed, gluten, high-fructose

maize syrups, and others.

2.1.3. Oilseeds

Vegetable oils can be extracted from several types of seeds

and fruit pulps. Rapeseed oil, palm oil and sunflower oilare the most common industrial feedstocks, particularly

for biodiesel production. Feedstocks are characterized by

the type and concentration of their fatty acids: generally,

saturated, mono-unsaturated, or poly-unsaturated. Choice

of the oils to be used depends on process chemistry and

economics. For the process itself, the main difference be-

tween different vegetable oils (or fats) is the amount of

free fatty acids that are associated with the triglycerides

as well as the content of other contaminants such as odour

compounds that can reduce the quality of the glycerine

produced. Free fatty acids present in oil will react with

alkali catalyst used to facilitate the esterification reactionto form soap, an undesirable reaction that deactivates the

catalyst. Feedstocks with similar compositions can be

used interchangeably in processes designed for those com-

positions, enabling the use of lower-cost feedstocks when

they are available. For biodiesel, the ideal feedstock is

composed of 100 % triglyceride because the triglyceride

will react with three molecules of methanol to produce

three molecules of methyl ester (biodiesel) and one mole-

cule of glycerol.

As with starchy crops, biofuel production from oilcrops results in co- and by-products, namely animal feed

from cake. This by-product is of importance for some de-

veloping countries, e.g., in many countries in Africa where

animal feed availability is problematic. In Burkina Faso

oil extracted from cotton seed is as cheap as or often

cheaper than cotton seed cake sold for animal feed. The

vast potential of biodiesel from oil biomass is under in-

vestigation in several countries such as India, which de-

cided in 2003 to aim at 20 % biodiesel blending by 2011,

or Brazil which launched its national biodiesel programme

in December 2004 [CenDoTec, 2004]. Concrete plans are

being formulated to use wastelands for tree-borne oilseedplantations such as Jatropha curcas and other interesting

native oil-rich plants as they do not compete with food

crops. Data on productivity are limited and to a certain

extent contradictory [Riedacker and Roy, 1998]. However,

plant selection and improvement of agricultural practices

are likely to increase productivity.

The amount of oil biomass potentially available for en-

ergy on a country-by-country basis is not a fixed estimate.

Indeed, production, demand, exports and prices greatly

depend on area actually planted, climatic conditions, per-

centage of oil extracted from seeds, food and feed de-

mand, competing uses, and even exchange rates.

2.2. Lignocellulosic products and residues

The main components of a plant are neither sugar nor

starch but cellulose, hemi-cellulose and lignin, as illus-

trated in Table 1. Lignocellulosic biofuel feedstocks are

potentially more abundant and cheaper than feedstocks

from conventional agriculture (e.g., seeds) because they

compete less directly with food crops. In principle, there

are numerous potential benefits from developing and im-

proving biofuel production from cellulose with second

generation biofuels: conflicts with land use for food pro-

duction are reduced, since residues can be used or plan-

tations can use set-aside land, incomes for farmers can be

improved through better use of by-products, potential andyield in terms of toe/ha (tonnes of oil equivalent biofuel

per hectare of land required) can be increased, and net

GHG emissions can be reduced, there are opportunities

to use set-aside land and poorer soils for energy planta-

tions such as short rotation and fast-growing tree species

(willow, poplar, eucalyptus), and there is the possibility

of using residues and municipal solid waste (MSW).

2.2.1. Wood

Woody biomass, including wood itself and forest and

wood-processing industry residues, accounts for the larg-

est fraction of renewable energy used globally today. It

represents more than 60 % of the total primary energyconsumption for many developing countries and can reach

up to 80 % or more for the poorest African countries

(Mali, Niger, etc.). Wood is a well-known product and

presents interesting characteristics such as relatively high


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density and a low level of impurities compared to other

kinds of biomass. It therefore constitutes a perfect feed-

stock for biofuel production. However, partly due to these

properties, it is also widely used for ther making other

products, e.g., paper, timber, particle board and fibre-

board, and consequently constitutes one of the most ex-

pensive feedstocks.

Wood residues, consisting of logging residues (tops,

branches) and process residues (off-cuts, sawdust) from

wood industries, and demolition wood, constitute a large

potential which might be available at lower prices com-

pared to logs. The availability of these resources depends

on the efficiency of the industry they come from. Typical

residue yield from a tropical sawmill for export is between

15 and 20 % of the total biomass (full tree), or 30 to

45 % of the actual biomass (e.g., logs) delivered to the

sawmill. These biomass types vary in composition, vol-

ume and quality (particularly moisture content from 12

to 55 % on a dry basis), depending on the processing

steps and soils of origin. Depending on particle size, the

bulk density may also vary significantly, which often re-quires a preliminary pre-treatment in order to make it ap-

propriate for downstream processing.

2.2.2. Energy plantations

Energy plantations are grown and harvested to specifically

provide energy. They are already well established, e.g., in

Brazil where eucalyptus plantations supply charcoal to the

steel industry [Claret, 2003] and logs to pulp/paper mills.

Plantations can be grown on lower-quality land, hence do

not necessarily compete with other agricultural activities

aimed at food production. They also require fewer inputs

(pesticides and fertilizers). However, particular attention

should be paid to species selection and large monocul-tures. In the long term, the highest potentials will result

from the use of local and mixed species together with

agro-forestry practices preserving biodiversity. The pro-

ductivity of a plantation varies according to many factors

relating to species and plant selection, plantation, and

maintenance techniques. In addition, the location plays a

large part in the productivity. When water is not the lim-

iting factor, tropical countries benefit from favourable cli-

matic conditions, allowing two to three times higher

productivity than in temperate countries. In Brazil [Lima,1996], significant gains in productivity were achieved

with the adoption of more intensive forestry techniques

(preparation of the soil, fertilization, breeding, etc.); from

an average 15 m3/ha/year productivity in 1967 to

21 m3/ha/year today. With the introduction of new mate-

rials and through clone selection, 40 m3/ha/year has been

achieved [Wichert, 2005].

If the full tree utilisation maximises the short-term

biomass yield, it can also mean greater removal of soil nu-

trients. If the nutrient balance is not carefully controlled, it

can affect wood yields and biodiversity. Thus, the plantation

sustainability would require an increasing use of fertilisers.It is therefore important to find an appropriate balance be-

tween high biomass yields and long-term fertility of soils.

Achieving such a balance is relatively easy in practice, since

the largest part of the hydrocarbon content of a tree is bound

in stems, while the majority of nutrients are contained in

leaves and branches. Hence, after felling, it is the common

practice in eucalyptus plantations in Brazil for example to

leave the whole tree on the ground for a couple of weeks.

During this period, along with a significant drop in moisture,

the leaves and small branches drop off, returning nutrients

to the soil [Kornexl, 2001].

Growing dedicated herbaceous crops for energy pur-

poses is also possible. However, information on various

aspects of their cultivation is still limited despite intensive

research, particularly in the USA and the EU. The main

herbaceous species considered for energy application are

miscanthus, switch grass and cane fibre. Compared with

short rotation forest plantation, herbaceous crops have

lower moisture content, from 10 to 30 %, but are bulkier

products, increasing transportation costs. Their ash con-

tent is higher (from 3 to 12 % for miscanthus and sun-

flower stalks, respectively [Agrice, 1998]); with a broader

composition, including some undesirable compounds

which may create rapid deactivation or poisoning of proc-

essing catalysts, as well as some corrosion and slag prob-lems with some high-temperature conversion processes

such as gasification.

2.2.3. Agri-based residues

Agriculture and agro-industries are currently large provid-

ers of biomass resources. The availability of residue by-

products depends on objectives pursued for the

corresponding main crop and on world market prices. By-

products do not exhibit autonomous market behaviour.

Depending on the criteria authors refer to, the total world

potential is enormous, varying from to 9.5 EJ/year [Vaitil-

ingom, 2005] to 55 EJ/year [Hall, 1993]. If these figures

appear significant, the real availability is much less inpractice, limited by a number of factors. China and India

by far present the largest agri-based residue potential. This

is mainly due to their rice by-products, straw and husk,

which represent 83 and 71 % of their respective agricultural

Table 1. Residues (lignocellulosic fraction) and dry weight ratio of

straw to grain for different crops [Lal, 2005]

Crops Residue amount on dry

weight basis (t/ha/yr)[1]Range of

straw/grain ratio[2]

Barley 4.3 0.82-2.50

Maize 10.1 0.55-1.50

Cotton 6.7 0.95-2.0

Rapeseed - 1.25-2.0

Soybean - 0.8-2.6

Rice 6.7 0.75-2.5

Sorghum 8.4 0.85-2.0

Wheat 5.0 1.10-2.57

Notes

1. These data are average figures that may vary over a wide range depending on soilfertility, the use of fertilisers and pesticides, and the quality and the variety of the seeds.

2. The lowest grain yield generally corresponds to the largest straw (residue) yield. It

results from the low quality of seeds typically used in several developing countries.


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residue potentials. Rice straw accounts for 56 % of the

global potential of the top ten residues, followed by ba-

gasse (15 %) and rice husk and cotton stalks at 10 %

each.

The net availability of residues per hectare depends on

the crop itself and its specific residues-to-crop ratio (seeTable 1) as well as on climatic conditions and alternative

uses. Residues are a source of fertiliser, sometimes the

only one. Thus an important fraction of the biomass is or

should be left or reintroduced on the soil. Farmers also

consume a significant fraction as bed material for live-

stock and animal feed. Due to bans on field-burning and

the development of more intensive livestock practices,

straw is largely available in industrialised countries. How-

ever, in tropical countries, alternative uses and the weak-

ness of infrastructure for transport currently limit its

availability. The same remark applies to cotton stalks,

corn cobs and other herbaceous feedstock. Nevertheless,it can be assumed that a significant share of the straw

would be available particularly in countries with econo-

mies in transition because the production in these coun-

tries generally results in greater availability than needed.

Cane trash and bagasse are produced during the har-

vesting and milling period of sugar cane, which normally

lasts 5 to 7 months. Cane trash consists of sugar cane

tops and leaves. Nowadays, it is mostly burnt in the field

as sugar mills are already largely self-sufficient in energy.

The bagasse produced is already used in existing sugar

mills to meet their own electricity and heat demand. How-

ever, existing milling and power generation equipment

have limited efficiency and a large part of this bagasse

could be available through energy efficiency programmes.

Of the worlds sugar mills, more than half have a potential

for electricity export generating capacity greater than 5

MWe(and in many cases much greater than 5 MW e). Ba-

gasse and cane trash constitute an important potential

source of biofuel feedstock. However, upgrading tech-

niques and equipment adequately might not benefit trans-

port fuel production because in many countries (India,

Thailand, Philippines, etc.) real incentives exist to produce

electricity, e.g., through independent power producer

(IPP) arrangements, but similar incentives for biofuel pro-

duction do not exist.Rice husk, the main by-product from rice-milling, ac-

counts for roughly 22 % of paddy weight, while the rice

straw-to-paddy ratio ranges from 1.0 to 4.3, depending on

the species. In general there is a large excess of rice husk,

whose disposal can add to the rice-millers costs. The type

and particularly the size of the rice mill affect the real

availability of rice husk. Indeed, large producers such as

Indonesia and to a certain extent India present industrial

sectors characterised by a large number of very small

mills spread all over the country. Despite a large potential

of unused rice husk, collecting this feedstock is often not

economically viable. When the industry is well estab-lished, the growing demand for parboiling rice increases

the use of rice husk to meet the heat needed by the mill.

Large CHP plants up to 10 MWeare in operation in Thai-

land and in India, fed by rice husk.

3. Biofuel conversion technologies: state of the art

The scope of this section is to describe the main supply

chains for the production of different biofuels in both

technical and economic terms. For each technology, the

required biomass characteristics and degrees of maturity

will be presented for discussion. Second generation bio-fuels will only be briefly presented as their maturity is

expected to be effective only in ten years time.

3.1. Bioethanol production

Ethanol can be produced from any feedstock that contains

sugar or compounds such as starch or cellulose that can

be converted into sugar.

3.1.1. Conversion technologies

3.1.1.1. From sugar, fermentation and distillation

The oldest way of producing ethanol is fermentation of

glucose recovered by soaking, crushing or chemical ex-

traction from a sugar-rich feedstock. Glucose is fermented

to alcohol using yeast and other micro-organisms. The fi-nal step purifies the alcohol by distillation to the desired

concentration. In most countries making ethanol, all the

water is removed to produce anhydrous ethanol (99.3 %

ethanol) that can be blended with petrol. In Brazil 60 %

of the ethanol is sold in hydrated form (93 % ethanol by

volume, 7 % water) for use as a neat fuel.

3.1.1.2. From starch, hydrolysis then fermentation and

distillation

Starch consists of a long chain of glucose molecules that

have to be broken down into simpler sugars by hydrolysis

before their fermentation. The first step of the hydrolysis

process consists of milling the grain to free the starch

from the raw material. This step can be dry or wet. The

starch is converted into sugar in hot dilute phase to dis-

solve the water-soluble starch and maintain the activity

of the yeast. The starchy material is converted continu-

ously into short-chain carbohydrates. For the development

of the yeast needed for the fermentation process, the so-

lution must be slightly acid (pH ~5.0). Therefore, hydroly-

sis can be achieved by the addition of dilute mineral acid

to the grain slurry before cooking (acid hydrolysis proc-

ess). Due to the presence of water, the ethanol produced

is dilute. Through a series of distillation and dehydratation

steps the ethanol is purified down to the desired concen-

tration. Figure 2 presents the dry milling process scheme.As in the case of sugar, these technologies are well es-

tablished.

3.1.1.3. From cellulose, saccharification, then

fermentation and distillation

For the conversion of cellulosic material to ethanol, two

key steps are necessary. At first, cellulose and hemi-cel-

lulose must be broken down into small carbohydrates.

This step results in a complex mixture of a wide variety

of sugars, making the second step quite challenging, since

different organisms are required to ferment different sug-

ars into ethanol. The first step is currently the subject of

intense R&D worldwide and particularly in the USA asit remains the major bottleneck in the development of this

route. The conversion (hydrolysis) of cellulose to sugar

can be realised using diluted acid, concentrated acids or

enzymes (cellulase). Enzymatic hydrolysis of cellulose is


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clearly preferred to acid hydrolysis from a process and

environmental point of view. However, this route is still

under development. There are numerous publications avail-

able on the subject [Sun and Cheng, 2002; NAL, 2005].

3.1.2. Conversion efficiency of bioethanol production

One of the main intrinsic drawbacks of bioethanol pro-

duction processes is related to the large CO2release into

the atmosphere as a result of energy consumed to run the

process. In conventional bioethanol plants based on sugarbeet or starch the processing into ethanol requires 80 %

of the total energy consumption (electricity 10 %, heat

70 %), while agricultural production accounts for only

20 % [ADEME-DIREM, 2002]. Bioethanol production

from cellulose using side products (lignin) for combined

heat and power generation would result in significant cost

reduction. Process efficiency on an overall basis is the

most important parameter to assess the performance of

options, as it will affect the net GHG emission reduction

as well as the cost. It would also have a considerable

impact on the plant capacity requirement, which most

probably will constitute one of the bottlenecks of someof the options.

Regarding efficiency, a large number of studies have

been carried out in the past 15 years, yielding a wide

range of figures, because:

the degree of maturity of the technology is not the

same and it is difficult to fairly compare actual figures

to expected results for promising technologies ex-

perimented with on a pilot-scale basis;

assessment methodologies have evolved since the first

work done on the subject, particularly life-cycle analy-

sis (LCA);

all studies do not take into account the same factors;

and the context of the study may also considerably affect

the impact on the process, e.g., fuel used for the gen-

eration of the electricity used (whether from coal, nu-

clear or any other source).

To limit distortions caused by the various sources listed

above, information provided in Table 2 comes from the

most recent studies. It shows that one energy unit of etha-

nol requires respectively 0.5 to 0.6 and 0.9 to 1.0 units

of fossil energy for its production from maize and wheat,

respectively. The production efficiency varies between

346 and 398 l ethanol/dry t feedstock. It represents, for

maize, a productivity between 2570 and 3113 l/ha, withcrop yields considered between 5.65 and 7.97 t/ha.

Ethanol from sugar cane in Brazil shows the best per-

formance in terms of both energy efficiency and net GHG

emissions. This is due to the high productivity of the

Figure 2. Ethanol production from grain dry milling [Reith et al., 2001]

Table 2. Ethanol production efficiency (adapted from [IEA, 2004; Moreira, 2003; Wang, 2001; Levelton, 2000])

Biomass ethanol production Cane Beet Maize Wheat Cellulosic biomass

Technology route Fermentation, distillation Hydrolysis/fermentation,

distillation

Wood Straw Maize

residues

Process efficiency

(energy in/energy out)

0.12

0.098

0.64

0.56

0.54 (dry mill)

0.75 (wet mill)

0.98

0.81

1.90

1.20

1.12 1.10

Ethanol production efficiency

(l/dry t biomass feedstock)

73

90

54.1

101.3

387.7

372.8

348.9

346.5

N.a.

288

330 345

Well-to-wheels GHG emission compared

to petrol (%) reduction/km travelled

N.a.

92

50

56

32

25

29

47

51

107

57 61

Note

Process energy includes both biomass and non-biomass energy sources. The table gives when possible the range of estimates reported in the papers.


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tropical crop and the high degree of integration of the

plant where bagasse can largely cover the plant energy

needs. However, in many sugar industries worldwide, in-

cluding Brazil in the North-east region, additional fossil

energy is required as the process design or the equipment

is too old. Nevertheless, it can be expected that the highestefficiency achieved in the best Brazilian mills will become

the average value in the short term for all Brazil as well

as several other countries (Thailand, India, etc.). Indeed,

increasing oil prices have prompted countries to elaborate

policies in favour of biofuels. In India, the government

declared the use of 5 % ethanol blend in petrol mandatory

in nine states and four Union Territories (areas adminis-

tered by the federal government) by the end of 2003.

There are limited opportunities for further energy balance

improvement or cost reduction for these routes.

Most of the research and development nowadays fo-

cuses on the lignocellulosic route where it is expected, asin sugar cane conversion, that lignin and other uncon-

verted products would supply the energy process require-

ments and may produce additional electricity [Sims, 2004;

USDOE, 1999]. The main drawback of this option may

concern the type of feedstock used and the total fossil

fuel required for the collection and the transport of large

volumes of biomass (straw for example), or in fertilizer,

depending on the type of biomass, the situation and the

size of plants.

3.1.3. Economics of bioethanol production

As is the case with other biofuels, the largest bioethanol

cost component for sugar or starch-based production (as

illustrated in Figure 3) is the feedstock (58 to 65 %), al-

though typically about 50 % of this cost can be paid back

by sale of co-products. The plant size also has a major

impact on the cost. For instance, tripling the size of maize

mills, dry or wet, would result in cost reductions of 0.05

to 0.06 US$/l: 40 % on specific investment and 15 to

20 % on operating costs [Moreira, 2003].

Ethanol production from lignocellulosic material is

more capital intensive than conventional sugar/starch

plants due to the complexity of the process. Enzymes are

also very expensive (0.12 US$/l) [Wooley et al., 1999]

and the hydrolysis step is long (48 to 72 hours). A study

carried out by NREL for the IEA Bioenergy implementingagreement gives estimates of investment and production

costs of ethanol from poplar in the US and Canada. It

shows that for a 2000 t/day plant capacity (198 Ml/year),

the estimated investment cost ranges between US$ 205

and 234 million and that it is expected to go down to US$

159 million by 2010 [IEA, 2000]. These figures represent

a specific capital cost between 0.139 and 0.177 US$/l,

compared to 0.05 from corn (maize) in the US, between

0.06 and 0.1 from wheat or beet in the EU and 0.05 from

cane in Brazil. Because bioethanol from cellulose can also

benefit from cheap feedstock, it is expected to be com-

petitive by 2010.3.2. Vegetable oil for straight use (SVO) or biodiesel

Vegetable oil can be used as fuel in a variety of ways:

directly as a fuel in a boiler or a stationary genset or car

or tractor engine, processed into biodiesel (fatty acid

esters) or processed into bio-distillates through refinery

technology.

3.2.1 Straight vegetable oil (SVO)

Fuel properties (freezing point, cetane number and viscos-

ity), hence suitability of SVO as a transport fuel in a con-

ventional car, vary with fatty acid composition and thepresence of minor compounds such as sterols, antioxidants

and phosphatides. To overcome problems and allow the

use of a wider range of vegetable oils on a large scale

without engine modification and with environmental im-

pact improvements, oils (triglycerides) are transformed

into smaller molecules by means of esterification with al-

cohol, mainly methanol (see below).

3.2.1.1. Conversion technologies and efficiency

Extraction techniques are well known worldwide and most

of the equipment used in several industries is manufac-

tured in developing countries.

Extraction of vegetable oil from seeds can be done me-chanically or by a solvent such as hexane, for both SVO

and esters. The latter results in a higher yield and is gen-

erally applied for biodiesel production. If we consider that

approximately on average one litre of biomass oil plus

10 % methanol are needed to make 1 litre of biodiesel

and 350 g of glycerol, the biofuel production yield is

high. However, oil yields per hectare greatly vary, as il-

lustrated in Table 3. Palm oil is certainly one of the most

productive crops. However, this production is deeply re-

lated to climatic conditions (rainfall) and the quality of

the soil.

Direct use of vegetable oil in an indirect injection en-

gine is possible. However, to avoid deposit and dust for-

mation the engine should be hot, which will require

double injection: once with diesel for start-up and once

for SVO. Often the SVO injection is pre-heated to reduce

its viscosity (4.2 cSt and 77 cSt at 20C respectively for

diesel and rapeseed oil). With modern direct injection en-

gines, modification of the piston is required to increase

the combustion temperature and avoid deposits and un-

burnt oil. Several kits can be purchased, particularly in

Germany [ELSBETT, 2005], with guidelines for their use

online [ROULEMAFLEUR, 2005]. Their cost is approxi-

mately between US$ 700 and 2000 per unit. A quality

standard has been set up specifically for SVO from rape-seed: DIN UA 632.

Vegetable oils are mixtures of triglycerides from vari-

ous fatty acids. The composition of vegetable oils varies

with the plant source. Therefore, the chemical and physi-

cal properties of oils and the esters derived from them

vary with the nature of the fatty acids. Table 4 shows the

relative impact of biomass oil composition on fuel prop-

erties. Several documents report specific data on these

properties for various types of feedstock as well as fatty

acid esters [USEPA, 2002a].

3.2.1.2. Economics of SVO

Worldwide, the direct use of vegetable oil in tractors, carsor stationary engines for water-pumping, power genera-

tion etc., is relatively common, although not widely

spread. In New Caledonia, a project aiming at using copra

oil to supply energy in Ouvea island resulted in the large


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use of copra oil for 600 kWeof power generation, a sea-

water desalination unit and several water-pumping units

as well as for cars and pick-ups of the cooperative [Vaitil-ingom et al., 2000]. The use of SVO allows farmers to

avoid oil taxes and large price fluctuations. However, the

feasibility of such a route is probably difficult for indi-

vidual farmers considering the investments required for

oil extraction, filtration, and storage, engine modifications

as well as seed prices. Feasibility and economic attrac-

tiveness are much higher on the cooperative or village

scale, where investments can be shared and relate to larger

SVO volumes. Pilot units are under development in Bra-

zilian Amazonia using mainly palm oil [CENBIO, 2004].

The present world SVO consumption level is not well

known. In several, particularly developing, countries,SVO is or has been used on a project basis (palm oil in

Malaysia, Jatropha in India). However, the use of SVO

may not be compatible with some standards on emissions,

for instance the European EN590 standard (see Table 5).

Compared to diesel, because combustion temperature is

lower, NOx emission is reduced by 25 % for SVO in a

modern diesel engine. However, CO emission can betwice as high [Hemmerlein et al., 2002]. Measurements

are still needed as very few documents report data.

3.2.2. Esterification for biodiesel production

Europe has largely contributed to the development of bio-

diesel, mainly from rapeseed.

3.2.2.1. Conversion technologies and efficiency

Methyl ester is generally produced through catalytic trans-

esterification of the oil with methanol. Oil molecules are

broken apart and reformed into esters and glycerol, which

are then separated from each other and purified. These

processes are well known and well documented [IPEF,

2005; Van Gerpen et al., 2004; USEPA, 2001]. While avariety of esterification types exists, most processes fol-

low the same scheme. Depending on the biomass oil, ad-

ditives might be used to adjust properties and

characteristics. Pre-treated oils and fats are mixed with

Figure 3. Comparison of bioethanol low and high production costs breakdown, compared to gasoline on a volume basis; figures from Europe, the USAand Brazil in $/l [IEA, 2004; Laydner, 2003; Enguidanos et al., 2002]

Note

In the case of petrol full cost (mid-2004) is given for comparison. Low and high prices correspond to different world market prices. These figures are only indicative as great variation

occurs and because cost breakdown is not always provided. The largest part of other cost is capital cost. Finally, costs shown do not reflect direct subsidies. Biofuel sectors are often

heavily subsidised. Differences observed between the EU and the US can be partly explained by the difference in subsidy schemes in agriculture.


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the alcohol and the catalyst, as illustrated in Figure 4. Esteri-

fication is highly efficient, with yields exceeding 99 %.

Processes are batch or continuous. A batch system is us-

able in smaller units. The technology may appear simple but

its control under industrial conditions to match transport fuel

standards requires appropriate technology which may be dif-

ficult to handle for small producers even if there are no

downsizing limits in principle. In Brazil, where the produc-

tion of biodiesel started with seven producers, only two were

able to respect the local quality standards adapted from the

EU standards. Steam requirements, the use of catalysts, and

quality control do not favour small-scale biodiesel plants.

The lower size limit for feasibility is also very dependent

on national economic contexts and oil prices. For small-scale

consumption in villages or small-city stationary applications,

SVO appears more favourable because total investment costs

remain limited.

For esterification, methanol offers better process effi-

ciency than ethanol, given ethanols affinity with water.

The kinetics of the esterification process with ethanol are

also slower, increasing specific capital costs.New routes are under investigation in Canada and the

US, particularly to convert biomass oil into hydrocarbon

fuel, using conventional existing petroleum refinery tech-

nology with minor modification. This approach would al-

low significant cost reduction as existing infrastructure

could be used. However, technical limits in terms of feed-

stock quality requirements and the share of biomass oil

in refining volumes are still unclear.

3.2.2.2. Economics of biodiesel production by

esterification

The cost of seeds represents the largest part of biodiesel

production costs from 60 to 80 % of the total cost [IPEF,2005]. Seed production costs vary widely depending on

where the crop is grown: quality of soils and seeds, cli-

mate, quantity and prices of fertilizers and pesticides, etc.,

are all elements that will affect yields and production

costs. For a 150 to 200 Ml per year conventional plant,

total non-feedstock production costs will be less than

0.05 US$/l of biodiesel, representing only 7 to 15 % of

the total production cost.

Glycerine is an unavoidable co-product of biodiesel. At

current glycerine market prices, glycerine credit reduces

biodiesel costs by US$ 0.05 to 0.1/l of biodiesel in the

EU. A large biodiesel expansion would flood the interna-

tional market with glycerine. Only the development of

new applications for glycerol would allow a rapid growthof the biodiesel industry. The amount and value of the

co-products play a critical role in the seed oil prices as

the price of oilseeds, cake and oil are intrinsically bound

together. Producing or crushing seeds of high oil content

is not necessarily cheaper than producing or crushing

seeds with a lower oil content, all other things being equal

depending on the credit that co-products offer.

Some systems use fixed catalysts, reducing variable

costs but raising fixed costs. Some systems are catalyst-

free, which might save as much as US$ 0.05/l in proc-

essing costs, but raise capital and energy costs because

these systems tend to use high pressure and temperature[Reith et al., 2001]. Even if non-feedstock costs could be

reduced by half, the savings are generally not enough to

make biodiesel competitive with diesel fuel because of

feedstock costs, as Figure 5 illustrates.

Table 3. Yields and some properties for vegetable oil and biodiesel per ha [Van Gerpen et al., 2004; CYBERLIPID, 2005; JATROPHAWORLD,

2005; Ballerini, 2006]

Crop Seed yield

t/ha

Viscosity at 40C

(mm2/s)

Cetane number Oil content

wt %

Litres SVO

per ha

Litres biodiesel

per ha

Soybean 2.67 33.1 38.1 18 481 524

Cottonseed 1.05 33.7 33.7 19 200 216

Canola 1.54 40 616 665

Sunflower 1.52 34.4 36.7 40 608 657

Peanut 3.40 40.0 34.6 25 850 920

Rapeseed 1.47 37.3 37.5 40 588 638

Mustard (spice) 1.04 40 416 452

Jatropha 2 49.9 40-45 37 740 701

Palm oil 20

(fresh fruit bunches)

63.6 42 49 2760 3000

Note

The very high yield of palm oil corresponds to Asian figures (Malaysia, Indonesia) and is due to generally very favourable climatic conditions, which unfortunately are not common in

Africa or Latin America.

Table 4. SVO composition and impact on fuel properties

[Thyson et al., 2004]

Saturated Monounsaturated Polyunsaturated

Cetane number High Medium Low

Cloud point High Medium Low

Stability High Medium Low

NOx emissions Reduction Medium increase Large increase


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Table 6 presents investment costs as a function of plant

capacity. It shows that economies of scale are much larger

from small to medium scales than from medium to large.

Costs might be lower with biodiesel produced from

waste oils or fats. However, limited availability of this

feedstock would limit the volume of biodiesel production

and probably result in small-scale implementation with

higher non-feedstock production costs.

3.3. Advanced biofuel synthesis (second generation)

Promising routes to convert biomass into liquid are by

means of gasification followed by syngas conversion. All

biomass compounds hemi-cellulose, cellulose and lignin can be converted into a H2/CO rich syngas. Among ob-

tainable fuels are methanol, diesel and petrol through Fis-

cher-Tropsch (FT) synthesis and dimethyl ether (DME).

Several comprehensive and well-documented publications

have been recently released on the subject by IEA

[Moreira, 2003], ECN [Van Thuijl et al., 2003], and the

European joint research centre ISPRA [Kavalov and

Peteves, 2005]. They do not focus on developing countries

but constitute a major source of technical information.

The following review draws on these publications. The

general scheme of this process, also known as biomass-

to-liquid (BTL) route, is summarized in Figure 6.

The thermochemical routes start from a biomass feed-

stock, which is converted into a syngas by means of dif-

ferent steps consisting of:

1. pre-treatment/upgrading of biomass;2. conversion of the biomass feedstock to a gas rich in

CO and H2;

3. gas-cleaning and -conditioning; and

4. synthesis.

Table 5. Emission limit values (g/kWh) according to the engine power rate (kW) [EU, 2002]

Power range (kW) 18-37 37-75 75-130 130-560

Compliance dates for 2000/25/EC 31-12-2001 31-12-2003 30-06-2003 30-06-2002

CO (g/kWh) 5.5 5.0 5.0 3.5

HC (g/kWh) 1.5 1.3 1.0 1.0

NOx(g/kWh) 8.0 7.0 6.0 6.0

PM (g/kWh) 0.8 0.4 0.3 0.2

Figure 4. General conversion process for biodiesel production from vegetable oil [Poitrat, 2004]


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First steps of the process are quite similar whatever the

final product. Only the gas-conditioning to modify the

H2/CO ratio and particularly the synthesis will be specificto the targeted fuel, i.e., methanol, FT diesel or DME.

As LNG or CNG would require adaptations of both the

vehicle engine and the refuelling infrastructure, its poten-

tial interest would probably be limited to countries already

equipped for LNG or CNG consumption (Italy for in-

stance). Since the biomass route will hardly compete with

natural gas, we shall not go into further detail on

LNG/CNG from biomass.

To convert a biomass feedstock into a suitable gas for

the synthesis of transport fuel, a gasification process is

applied, either air/oxygen gasification, steam gasification

or more advanced processes such as gasification in super-critical water. The gasification process yields a CO/H2-

rich gas. Depending on the oxidation agent (steam or

air-oxygen), the overall maximum stoichiometry of the re-

action of biomass will drive the overall gas composition.

Typical hydrogen yields are 170 kg H2 per tonne (t) of

biomass for steam reforming and 140 kg H2/t of biomass

for oxygen gasification followed by a shift.In the case of direct gasification processes, the heat nec-

essary for the process is produced by the internal sub-

stoichiometric combustion of part of the biomass fed into

the gasifier. Both air-blown and pure oxygen biomass

gasifiers are used for direct gasification. When oxygen is

used, a nitrogen-free synthesis gas is produced, but the

use of oxygen leads to higher operating costs and lower

global energy efficiency.

Indirect gasification processes use heat that is generated

by burning part of the biomass outside the gasifier or that

comes from an external source of energy. The heat is gen-

erally fed to the gasifier with steam. Using steam in-creases the hydrogen content in the raw gas. However,

due to the low temperatures applied, the tar content in the

gas is still rather high. For several decades, different types

of reactors have been developed for biomass gasification,

Figure 5. Biodiesel production cost breakdown (Europe, USA and India) in US$/l [Faaij, 2002]

Notes

Diesel oil costs are full cost fluctuation depending on the oil price (mid-2004). Long-term cost of biodiesel is an estimate on the basis of better use of co-products, particularly glycerol,

enabled by lower glycerol cost such as polymers and ethers, and the integration with biorefineries [Thyson, 2004].

Table 6. Capital cost estimates as a function of scale [Kearney, 1998, cited in Thyson et al., 2004]

Plant size

(Ml/year)

Low High

Total investment cost

(million US$)

Specific investment cost

(US$/l/yr)

Total investment cost

(million US$)

Specific investment cost

(US$/l/yr)

4 1.9 0.475 3.1 0.775

60 9.5 0.158 15.8 0.263

150 19.7 0.131 32.8 0.218


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such as fixed beds, fluid beds and entrained beds. It is

important to consider that many of the gasification con-

cepts were originally developed and optimized for the pro-

duction of electricity for which the syngas quality

requirements are less strict than for synthesis applications.R&D is still needed on upstream technologies for

biomass gasification/gas clean-up that are not quite ready,

and a number of process configurations are being experi-

mented with. Nevertheless, the gasification route for syn-

gas production is already demonstrated by:

SVZ Schwarze Pumpe GmbH (Germany) producing

methanol from different types of biomass and coal;

and

SASOL (South Africa) for Fischer-Tropsch synthesis

from coal, among others [SASOL, 2005].

Benefit should be expected from these industrial plants

(particularly SASOL) even if the use of biomass entailsdifferent constraints on gasification and gas-cleaning com-

pared to coal.

The number of projects aiming at producing syngas

from biomass by thermochemical processes is limited but

significantly increasing in the past couple of years in a

number of countries, particularly Germany. New advanced

systems are being developed with a complete biofuel pro-

duction scheme, e.g., the BTL demonstration activities of

Choren GmbH supported by EU (including Daimler-Chrysler AG and Volkswagen among others) produced the

first quantities of BTL fuels from wood chips in 2004

[Kavalov and Peteves, 2005].

The synthesis gas resulting from any thermochemical

biomass conversion system contains carbon monoxide,

carbon dioxide, hydrogen, methane, water and possibly

nitrogen. The composition of syngas varies, depending on

raw biomass composition and operating conditions, as

illustrated in Table 7. Typically syngas would need further

cleaning as it is contaminated by impurities, and condi-

tioning such as shift reaction to adjust its composition in

terms of H2 and CO. Basically, these operations are simi-lar to those of existing coal- or natural gas-based systems.

Thus, gas quality requirements are the same.

One aspect of special importance is the presence of tar

in the raw gas, with a much higher concentration and a

Figure 6. General biomass gasification conversion scheme to biofuels

Table 7. Main components and properties of gases obtained via different gasification concepts [Van Thuijl et al., 2003]

Gas composition

vol. % dry

Air-blown atmospheric

CFB

O2 atmospheric

CFB

O2 pressurized

CFB

H2O atmospheric O2 pressurised

entrained flow

CO 19.3 26.9 16.1 42.5 46.1

H2 15.6 33.1 18.3 23.1 26.6

CO2 15.0 29.9 35.4 12.3 26.9

CH4 4.2 7.0 13.5 16.6 0.0

N2 44.5 0.7 12.3 0.0 0.4

C2 1.4 2.4 4.4 5.5 0.0

Net calorific value

(MJ/m3)

5.76 8.85 8.44 13.64 7.43

H2/CO ratio 0.81 1.23 1.14 0.54 0.58


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wider composition when biomass has been gasified rather

than coal. During the last two decades, enormous efforts

have been put into the development of tar removal/con-

version technology, with limited success.

The gas also contains other contaminants such as small

char particles, chlorides, sulphur, alkali metals and nitro-gen compounds, as illustrated in Table 8. These contami-

nants must be removed, since they would decrease the

catalyst activity in the gas reformer, the shift and synthesis

reactor and may cause corrosion and fouling problems in

heat exchangers and pipes.

Impurities can be removed using conventional cold gas-

cleaning trains including cyclones and scrubbers. How-

ever, the very strict requirements of the synthesis catalysts

make gas-cleaning the major challenge for the coming

years. More advanced and efficient, but still not proven,

hot gas-cleaning devices using hot gas filters and catalyst

are being pursued.After being cleaned, the syngas is conditioned. Further

steps then include processes such as CO2 removal and

reforming. During the conditioning step, the gas hydro-

carbons are converted by steam reforming to H2and CO,

over a nickel catalyst. Auto-thermal reforming is preferred

as it is cheaper to operate. However, coking may occur,

the prevention of which would require higher steam con-

sumption. H2 and CO must be available in the ratios of

2 for methanol production and 2.1 for FT synthesis. As

Table 7 shows, the proportion of hydrogen in the raw gas

is usually lower than required. This is why the proportions

of these two components must be adjusted via a water-gas

shift reaction. The CO reacts with water to produce CO2and H2. The CO2 is removed afterwards by means of

chemical or physical absorption. The synthesis gas is com-

pressed and transported to the final synthesis reactor. Bio-

fuels produced by gasification and synthesis processes are

very clean fuels as the syngas cleaning and conditioning

steps are very demanding.

For the production of 1 t of FT diesel about 8.5 dry t

of wood are necessary, representing a yield of about 150 l

of FT diesel per t of wood [Boerrigter et al., 2002]. In-

creasing efficiency is expected and 200 l/t should be

reached through advanced gasification technology that is

able to achieve a more appropriate H2/CO ratio. With suchperformance, fast-growing plantations under tropical cli-

matic conditions found in various developing countries

would considerably reduce FT diesel production cost.

Though it can be noticed that feedstock cost will be lower

than for first generation biofuels, comparing cost figures

is difficult because gasification and gas clean-up technolo-

gies needed for FT production are only at an R&D or

pilot-demonstration stage of production and application

and main data are estimates from natural gas plants.

3.4. Biofuel end-use

Most biofuels present great potential in comparison with

other transport fuel alternatives due to their ability to beblended with current fuels. Blended forms require almost

no modifications, either to engines or in infrastructure.

Low percentages of ethanol such as 5 to 10 % are already

common as blends with petrol in many countries world-

wide. This is also true for biodiesel (esters). They both

might be used pure with minor engine adaptations. TheFT fuels are so close to conventional diesel that they are

fully adequate to any blending percentage or can even be

used pure. Table 9 lists biofuel properties, in comparison

with those of diesel and petrol.

These properties partly determine the engine emission

levels. Compared to the fossil fuels they substitute, bio-

fuels generally lower emissions of carbon monoxide, hy-

drocarbons, sulphur dioxide and particulates. Their impact

on NOxis limited. However, due to the lack of experience

with biosynfuels (second generation), few data are avail-

able so far regarding their potential for reducing engine

emissions.

GHG emissions can definitely be reduced by biofuels.

Nevertheless, estimating the net impacts of using biofuels

on GHG emissions is a complex issue and requires a full

understanding of the fuel chain on a LCA, from biomass-

growing to final use (well-to-wheels approach). Most

studies concern ethanol and biodiesel in the US or EU

contexts, but only few analyse the ethanol from sugar

route and the developing countries. We shall not present

any result here, but we refer the reader to another article

on this topic [Larson, 2005].

3.4.1. First generation biofuels

Ethanol can be used in current spark ignition engines. The

octane number of ethanol is higher than that of petrol,hence ethanol has better anti-knock characteristics. This

quality of the fuel can be exploited only if the compres-

sion ratio of engines is adjusted accordingly. The oxygen

content of ethanol also leads to higher efficiency, which

results in a cleaner combustion process at relatively low

temperatures. Compatibility problems between ethanol

and some components of the engines such as some types

of plastics or metals are well known and have been progres-

sively solved. As the concentration of ethanol increases,

adaptation problems may also increase, depending on both

the biofuel type and the engine specificities. In Brazil new

cars can run indiscriminately on fuel with from 0 to al-most 100 % ethanol.

It is also possible to blend some ethanol into diesel.

However, its low cetane number has limited its use in

compression engines. The main research goal in diesel-

Table 8. Syngas impurities content and maximum concentration

allowable in syngas for catalytic synthesis conversion

Contaminant Concentration

(wt %)

[Hamelinck, 2004]

Estimated gas

specification

(ppb)

Particles 1.33 0

HCN & NH3 0.47 20

H2S & COS 0.01 10

Alkalis 0.1 10

HCl 0.1 10

Pb & Cu Trace Not known

Tars (g) 0.05 to 5 0


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ethanol technology is to identify additives that would helpethanol to ignite by compression. Progress is reported in

this area, particularly in the USA.

Regarding engine emissions, the well established im-

provement is on CO emissions, which can be reduced by

25 % or even more when ethanol is blended at 10 % with

petrol [USEPA, 2002a]. Other pollution impacts of etha-

nol are less clear.

Esterified biomass oils are suitable for application in

diesel engines as their viscosity, density, and cetane num-

ber are similar to those of diesel. Table 9 indicates a

higher cetane number for rape methyl ester (RME) com-

pared to regular diesel. This results in a good ignition

quality, which means higher engine efficiency and a better

prospect for emission reduction. RME density is slightly

higher than that of diesel, compensating for the reduced

energy content (in MJ/kg) of RME to some extent. Energy

content per unit volume for RME and diesel are closer.

The lower energy content of RME is due to its much

higher oxygen content compared to diesel. Because vehi-

cles using RME have, on an energy basis, the same fuel

consumption as those running on diesel, this lower energy

content leads to larger volume of fuel consumption.

Biodiesel can be easily used in existing diesel engines in

its pure form or in any blending ratio (more commonly in

5 to 20 % blend). Like ethanol, the use of biodiesel in pureform requires only minor engine modification to satisfy

compatibility with some types of synthetic and natural

rubbers.

The properties of biodiesel are related to the oil it

comes from. Though pure biodiesel can be used in un-

modified diesel engines, blending offers the best commer-

cial potential because of better performance and lower

costs up to now. RME and soy methyl ester present better

freezing point properties than palm oil methyl ester, for

instance. Biodiesels have similar properties to diesel.

However, they show better lubricity, no aromatic or sul-

phur contaminants and higher cetane number, which makefor lower emissions of most of the pollutants common

with petroleum products. The US Environment Protection

Agency (EPA) reported that the potential for reduction of

emissions of a fuel is almost linear with its biodiesel con-

centration, with the exception of NOx [USEPA, 2002b].One of its major advantages over fossil diesel is its ability

to reduce SOxemissions. Sulphur, which increases the lu-

bricity of diesel can be replaced by a small quantity of

biodiesel.

3.4.2. Second generation biofuels

Methanol can be applied in almost any vehicle type and

can be used as a neat fuel or mixed with other hydrocar-

bons. As Table 9 showed, methanol has a low cetane num-

ber, indicating poor ignition quality, which means that, as

for ethanol, its use in compression ignition engines will

be difficult. Methanol density is higher than that of petrol.

However, the calorific value is 50 % lower than that of

petrol. Because it is poisonous, extra precautions are

needed, making its use difficult. An existing petrol or die-

sel tank at a refuelling station can be retrofitted to handle

methanol for US$ 20,000 to 32,000. The capital costs of

adding methanol storage and dispensers to an existing pet-

rol station would be between US$ 55,000 and 100,000

[CEC, 1999]. Methanol is considered a potential hydrogen

carrier for on-board reforming in fuel cell technologies in

the long term.

FT diesel is a high-quality and clean transportation fuel

with favourable characteristics for application in diesel

engines. FT diesel is similar to fossil diesel with regard

to energy content, density, viscosity and flash point. Itpresents a higher cetane number. Moreover, it has a very

low aromatic content, which leads to cleaner combustion.

This means that particles and NOxexhaust emissions are

lower. Finally, sulphur emissions are avoided, because FT

diesel is sulphur-free due to synthesis requirements. It can

be used in current diesel engines and the existing diesel

distribution infrastructure without any modifications.

DME can be produced directly from syngas in a slurry-

type reactor similar to the one used for methanol synthe-

sis. It is estimated that approximately 3 t of wood are

required to produce 1 t of DME [Van Thuijl et al., 2002].

DME can also be produced from methanol, but the directproduction route should be more efficient as it involves

one process instead of two. Before being used as a fuel,

DME was used primarily as a propellant in spray cans.

This is still its primary application. It is also used as

Table 9. Biofuel properties compared to those of conventional fuels

Fuel properties Ethanol ETBE RME Methanol FT diesel Diesel Petrol

Chemical formula C2H5OH C4H9OC2H5 - CH3OH C15-C20 C12H26 C8H15

Octane number 109 118 - 110 - - 97

Cetane number 8-11 - 51-58 5 70-80 50 8

Vapour pressure at 15C 16.5 28 - 31.7 - - 75

Density (kg/l) at 15C 0.80 0.74 0.88 0.79 0.78 0.84 0.75

LCV (MJ/kg) at 15C 26.4 36.0 37.3 19.8 44.0 42.7 41.3

LCV (MJ/l) at 15 C 21.2 26.7 32.8 15.6 34.3 35.7 31.0

Stoichiometric air/fuel ratio (kg air/kg fuel) 9.0 - 12.3 6.5 - 14.59 14.7

Boiling point (C) 78 72 N.a. 65 72 77 30-190


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an ignition improver in methanol engines. Even if the In-

ternational DME Association expected large, economical

supplies of natural gas-derived DME by 2005, it is still

at an experimental stage for vehicle use. Being gaseous

at ambient temperature, it would require large engine ad-

aptation unless it is considered for blending with LPG foruse in LPG engines. Increased use of DME for energy in

the near term will be as a substitute for LPG in domestic

(household) applications.

4. Concluding remarks

Technology plays a central role in energy resource char-

acterisation and in the assessment of potentials as well as

of relative interests of competing supply chains. It inter-

venes at the level of exploitation, transport, conversion

processes and final consumption (energy service). Tech-

nology can increase energy efficiency, enlarge possibilities

in terms of resource valuation, and reduce risks and en-vironmental impacts, if such objectives are sought. Nev-

ertheless, aiming at those objectives with biofuel

technology requires a clarification both of the objectives

and the contexts in which they are pursued.

In most developing countries, energy needs are consid-

erable and linked to economic development, which at

some point may be obstructed unles greater access to en-

ergy can be guaranteed under controllable conditions. To

what extent can biofuel technologies offer the opportunity

to reduce vulnerability towards international energy mar-

kets while increasing the value of local resources and gen-

erating employment?

The answer needs to take into account that local

biomass resources are specific to a context and might be

different from those already used for biofuels. Moreover,

the demand for liquid biofuels might also follow different

patterns in developing countries than those in industrial-

ised countries. Unless those specificities are taken into

account, biofuel technologies might fail to efficiently

serve developing countries interests. The more capital-in-

tensive biofuel industries would require large investments,

the availability of which are largely dependent on domes-

tic priorities.

4.1. Energy for development

Large international sponsors, in relation to the UN Mil-lennium Development Goals [AdO, 2004], more and more

often mention the locally established energy-poverty link.

At the macro-economic level, growth in developing coun-

tries goes hand in hand with a strong increase in energy

needs, which puts further pressure on energy resources

and prices, specifically of fossil fuel.

Therefore development is commonly associated with

the substitution of firewood and other traditional forms of

biomass by fossil energy. However, the vulnerability of

developing countries without domestic fossil fuel re-

sources is high. The price levels to be reached and the

fluctuations to be expected are difficult to predict, butthere is a global consensus that the oil price will remain

high, because the growing demand will soon exceed pro-

duction capacities.

At their present stage of development, however, except

for very favourable contexts (e.g., in the Centre-South

region of Brazil) biofuels do not appear competitive

against fossil fuels, especially second generation biofuels

that would use resources not directly competing with food

supply. Few countries may expect to reach low production

costs in the short term. Moreover, it would not be fair atthe current levels of North-South disequilibrium regarding

wealth and energy consumption to put pressure on devel-

oping countries to make costly energy choices for the sake

of international energy price stability and of the global

environment.

The relevance of biofuel energy choices for develop-

ment is not trivial. Several points require discussion and

further investigation. ESMAP (the World Banks Energy

Sector Management Assistance Program) recently publish-

ed a report which addresses these issues with a particular

focus on Brazil [Kojima and Johnson, 2005].

Lock-in effects in favour of oil technologies hamperbiofuel competitiveness. For many decades, they have

benefited from learning and scale effects, making the

adoption of alternatives costlier than further improve-

ments in oil fuel supply chains.

The question for biofuel technologies relates to what

scale and learning effects investments in developing coun-

tries might generate. To what extent could costs decrease

through technological progress but also logistical and or-

ganisational improvements within a supply chain? At what

oil price levels will biofuels break even? Or, by what time

horizon could a biofuel technology learning curve (giving

fuel costs as a function of volume produced and time)

possibly meet fossil fuel cost curves?

The Brazilian case is a reference point for the produc-

tion of ethanol from sugar cane. However, sugar cane is

a water-intensive crop, which means its replication poten-

tial is restricted. The 2004 drought, which affected India

and Thailand among other countries, has seriously frozen

the interest of sugar millers in bioethanol programmes de-

spite government incentives and the setting-up of appro-

priate policies.

Whatever the oil price, some situations in small islands

or land-locked countries with inadequate transport infra-

structure to access ports or pipelines make investments in

biofuel production profitable in the short term, particu-larly if crops and biofuel production can be located close

to consumption centres. In Burkina Faso, cotton oil, al-

ready suffering from slight overproduction, might be at-

tractively used as fuel. Its conversion into ester rather than

being used as crude oil to fuel stand-alone power genera-

tion facilities needs to be questioned and investigated.

Table 10 establishes the land areas needed to meet the

10 % criterion for each biofuel in European countries.

This shows that land availability might be a real con-

straint. Land potentially available for biofuel production

is mainly to be found in tropical areas [Les Echos, 2004]

that are in developing countries. These lands are poten-tially available because food crops would not need them

under most probable agro-demo-economic scenarios and

because climatic conditions are often favourable.

However, land availability depends on the attractiveness


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of biofuel plantations vis--vis other land uses. To what

extent and in what conditions do biofuel plantations sus-

tainably generate value for the local population? Are they

the best route to development compared with other uses

of land, water and workforce?

By (co-)providing local energy services (for irrigation,

post-harvest value-adding activities, etc.), biofuel produc-

tion may stimulate domestic agricultural production and

expand markets for agricultural products. However, for

reasons of scale economies and proximity to large-scale

fuel demand, biomass supply may need to be centralisedfor fuel conversion in biorefineries located near transport

infrastructure. External demand being possibly strong,

how would incentives compare for the satisfaction of local

energy needs and that of external demand? Where are the

complementarities (integration of a variety of feedstocks,

simultaneous production of a variety of products, cogen-

eration of BTL route contributing to improving local ac-

cess to electricity, etc.)? Under what conditions would

complementarities hold under growing external demand

at higher prices than local demand can afford?

Whatever the availability of resources, biofuel devel-

opment schemes need to be clarified in terms of valueenhanced by different options under consideration, not

only monetary value generated instantly but also within

the longer term considering basic needs and development

strategies.

A frequently cited benefit of biofuel production is job

creation, especially in rural areas. Coelho et al. [2004]

claim that the Brazilian sugar cane sector is employing

around 700,000 people, responsible for around 3.5 million

indirect jobs, corresponding to the production of 350 Mt

of cane (not solely for the production of biofuels).Depending on the type of feedstock and the technolo-

gies used to convert it into fuels, the employment gener-

ated by a biofuel supply chain in rural areas would be

more or less important. Biosynfuel production associated

with fast-growing trees such as eucalyptus offers the best

opportunity in terms of employment as it would mix low-,

medium- and highly-skilled workers. Similarly to Brazil-

ian plantations for charcoal for the steel industry, a better

social impact should be expected as the ratio between

skilled and unskilled labour is rather high.

However, workforce availability might be an issue. The

countries where the highest potentials lie in terms of landare not necessarily endowed with large populations. For

instance, the Central African Republic has large unculti-

vated land and good climate conditions but the density of

the population is below 10/km2 in those areas.

4.2. Appropriate biofuel technologies for developing

countries

The first generation biofuels in developing countries will

suffer from the same handicap as in industrialised ones;

the production of oilseeds or sugar/starch-rich plants will

necessitate large availability of good soils and the use of

fertilisers and pesticides, competing with food and feed

crops. For this reason, their contribution will remain in

most cases limited and costly. However, the technology

is mature and could be readily implemented.

The best prospects both in terms of land availability

[Fallot and Girard, 2005] and yields per hectare (Ta-

ble 11) are in developing countries, with biofuel technolo-

gies differing from those currently used in industrialised

countries with agricultural surpluses.

Clearly, potential is higher with second generation fu-

els, presenting a potential contribution larger than con-

ventional biofuels. Therefore, the maturity of the

technology is certainly the weak point, as only conven-

tional biofuel technologies are operational on a large scale

today. The most promising routes in terms of productivityper hectare, which may at the same time use a wider range

of biomass types including lignocellulosic biomass, are

not yet proven on large scales and still require intense

research. Among all routes discussed earlier, FT diesel is

the only one that can be readily used and which benefits

from real large-scale applications, from coal up to now.

Obtaining a high-quality synthesis gas from biomass for

further transformation into biofuels (see above, Section

2.2.5 on pre-treatment) appears to be the crucial step in

the biomass-to-liquid route.

The development of second generation biofuel tech-

nologies would need significant government support,which is already aavailable in Europe and North America.

It is important for developing countries that will not de-

velop these technologies on their own to be associated

with this development, as this offers the best opportunities

Table 10. Land needed to produce feedstocks for biofuels under the

10 % substitution scenario: European data on yields,

1999 total world cropland [IEA/AFIS, 1999]

Short term Long term

Mha % Mha %

Methanol from cellulose 56 4 8040 6

Ethanol from cellulose 97 7 147 10

Ethanol from starch (wheat) 103 7 160 11

Ethanol from sugar beet 37 3 56 4

Biodiesel 120 8 170 12

Table 11. Biofuel yields per ha (l/ha and GJ/ha)

Generation Biofuel l/ha GJ/ha

First Sunflower biodiesel 1,000 35

Soybean biodiesel 500-700 17-25

Rapeseed biodiesel 1,200 42

Wheat ethanol 2,500 53

Maize ethanol 3,100 65

Sugar beet ethanol 5,500 116

Sugar cane ethanol 5,300-6,500 110-140

Second FT biodiesel eucalyptus

plantation

13,500-18,000 470-620

Methanol eucalyptus

plantation

49,500-66,000 770-1030

DME eucalyptus

plantation

45,000-60,000 8501130


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to acquire knowledge about second generation biofuel pro-

duction. Otherwise, there is indeed a risk that developing

countries end up exporting large volumes of raw biomass

to be further processed in industrialised country harbour

facilities with very limited impact on development. To

avoid this, investment patterns require forward-lookinginvestigation.

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Documents

biofuels - production and methods