Paper Biotechnology JournaL Biofuels Overview Problems

Biofuels Overview: Problems, Challenges and Perspectives

José Osvaldo Beserra CariocaUniversidade Federal do Ceará (UFC)

Departamento de Tecnologia de Alimentos (DETAL)Campus do Pici, Bloco 858, Fortaleza, Ceará, Brazil

Keywords: Biofuels, bioresources, ethanol, biodiesel, biogas and biohydrogen

Correspondence should be addressed to:Professor Dr. José Osvaldo Beserra CariocaRua Monsenhor Catão, 1442 Apto.601 Dionísio Torres60135-000 Fortaleza - CEPhone/Fax: +55-85.3287.3455E-mail: [email protected]

ABSTRACT

Humanity progress goes from simple experiences to extended formal knowledge. This is a good lesson to be applied to biofuels development. The purpose of this paper is to point out bioresources concerns and perspectives to use properly biomass potential considering land availability with ethic practices and fair policies. To reach biofuels requirements attempting, it is necessary to count on solid scientific knowledge which comprises several technological advances like: photosynthetic yields increase; plant breeding and selection; good agriculture practices; processing plants components to achieve a positive net energy ratio inside biorefinery concept; preparing communities to achieve local and decentralized systems avoiding subsidies and competition among food, feed, fibers, fuels and biochemical products. This harmonized view and pragmatic strategy will contribute to gradually replacing fossil fuels which will still dominate the global markets in the next three or four decades, while biofuels development will reach environmental friendly standards. G. Ciamacian, in 1912, had a visionary idea that photochemistry would play a fundamental role in biochemical and biofuels supplying. Finally, a historical and general road map of processes analysis and biofuels production based on OECD-FAO agricultural outlook for 2008-2017 and prices are presented.

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SUMMARY

1. Introduction2. Energy, economy, and environment3. Bioresources concerns and perspectives

3.1 Biomass state of art3.2 Biomass potential and land availability3.3 Microalgae promise and challenge

4. Discussion of biofuels production systems4.1. Updated progress on biofuels 4.1.1. Bioconversion routes 4.1.2. Thermochemical routes 4.1.3. Ethanol integrated and sustainable systems: biorefinery

4.1.4. Starch and inulin based materials to ethanol production 4.1.5. Energy balance in ethanol production systems 4.1.6. Vegetable oils processing

4.1.6.1. Catalytic cracking of vegetable oils 4.1.6.2. Transesterification of oils

4.1.7. Anaerobic digestion 4.2. New generation of biofuels 4.2.1. Biological production of hydrogen 5. Biofuels (ethanol and biodiesel) regional potential and prices 6. Conclusions 7. References

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1. Introduction: This paper will discuss, initially, data and facts on clean energy trends to elucidate biofuels problems, challenges and perspectives. This approach allows a better overview and dimension of the biofuels role. According to the report on 2009-Clean Energy Trends, it is expected a continuous growth in this sector in the mid-to-long term. Data from this report shows that the global revenues for solar photovoltaic, wind power, and biofuels expanded from US$ 75.8 billions in 2007 to US$ 115.9 billions in 2008. For this first time, only the wind power sector had revenues exceeding US$ 50 billions, while biofuels, ethanol and biodiesel reached US$34.8 billion in 2008 and are projected to grow to US$ 105.4 billion by 2018.

Considering prices and markets, 2008 - OECD-FAO Agricultural Outlook Report 2008-2017 presented for the first time an especial edition offering an assessment of agricultural markets which included an analysis of the problems and projections for global biofuel markets, ethanol and biodiesel. What happened and what will happen? These are crucial questions due to bioresources uses and their competitiveness with other market sectors like food, feed, fiber and bioproducts. In reality, there is a great concern on world prices of grain maize, wheat and oilseed crops which practically doubled prices in nominal terms between 2005 and 2007 marketing years. Commodity market volatility will continue, and the direction of changes is uncertain. In the majority of the developing countries some non-commercial crops are being proposed as raw materials for biofuels production and many factors are involved concerning to their use and relationship with the environment, mainly for biodiesel production. There is a need to improve conservation and productivity to collaborate with the rural population involved with bioresources use, as well as the genetic improvements of species.

A wider study on energy security, trends, scenarios and policies, including fuels production and supply, their use and emissions was prepared by IEA, 2006 World Energy Outlook. The main conclusion of this study is related to the unsustainable energy future which is being created. It means that if we continue as before, the energy supply to meet the needs of the world economy over the next twenty-five years is too vulnerable. Since Brazil is not a member of the OECD countries, it was presented in this report a summary of the main directives and goals practiced by the Brazilian government through its energetic model, once Brazil is one of the fifth largest countries in the world by land area and population, and a unique energy economy, of a real worldwide significance. Brazil has an energetic matrix almost clean in comparison with the world shown in Table 1, according to IEA, 2006 World Energy Outlook and 2006 Brazilian National Energetic Balance. As it is observed, world biomass accounts with 10.5% of the total world primary energy

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(TPES), which totalize about 1,176 million of tones of oil equivalent (Mtoe), while this participation in the case of Brazil is 26.7%. The world average consumption (11,204 Mtoe) is more than five times (57%) of the total primary energy supply of Brazil (213.8 Mtoe).

Ethanol from sugar cane in Brazil has taken almost a hundred years to achieve the actual state of art; economically feasible and self sustainable production systems, now claiming for integrated systems [1]. Besides that, a new generation of technologies is coming to improve residues use and energetic yield [2], as well as the ethanol-chemistry, likes biopolymers, according to Associação Brasileira da Indústria Química-ABIQUIM (Responsible Care Congress-2008 São Paulo, Brazil). That is a real history which is positively impacting environment, transport systems and generating socio-economic benefits. What are the correspondent world wide histories and evolution from the other biofuels, like vegetable diesel, biogas, bio-methanol and biological production of hydrogen? However, it is necessary to point out that this paper does not contain data concerning experiments using human or animal studies. The whole text only involves data with plant experiments. The author believes that it is absolutely necessary to formulate a general view of biofuels problems and perspectives to optimize the efforts to achieve the biofuels potential as soon as possible.

Table 1: World and Brazil Total Primary Energy Supply-TPES (Mtoe) for the year 2004

Forms of Energy

World (a) Brazil (b)

TPES (%) TPES (%)I- I - Non-renewable 9,729 86.8 120.1 56.2

Oil 3,940 35.2 83.6 39.1 Natural Gas 2,302 20.6 19.1 8.9 Coal 2,773 24.8 14.2 6.7 Nuclear 714 6.4 3.2 1.5

II- Renewable 1,475 13.2 93.7 43.8 Hydro 242 2.2 30.8 14.4 Biomass 1,176 10.5 57.0 26.7 Other renewable 57 0.5 5.9 2.7

III- Total (Mtoe) 11,204 100.0 213.8 100.0

(a) International Energy Agency - 2006 World Energy Outlook (b) 2006 Brazilian National Energetic Balance

2. Energy, economy, and environment The world energy history reveals that natural resources for energetic purposes passed through well defined production cycles of wood, coal, oil and natural gas. Except for uranium, the main characteristics related to the

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use of these resources are associated with emissions produced during its use, mainly CO2. In 1912, Ciamacian [3], the prophet of solar energy, condemned the use of coal and proposed the use of solar technologies to improve environmental problems. Normally, these resources are used for the production of fuels and chemicals. However, it was Odum [4] the first researcher to develop the concept of “ecological engineering” which later became the basis for academic programs and companies processes.

Earlier, economic theories did not consider the relationship with the production systems and the environment. Some models considered the economic sector as an isolated system, where the environment had an unlimited quantity of natural resources, and it was a formal deposit to residues of economic systems. So, the idea of evaluating the environment impact caused by the economy activities was first examined by Commoner and Erlich [5] due to the oil shock in the beginning of the seventies. These authors are responsible for the expression (1) indicated below to quantify the environmental impact due to specific consumptions. According to this equation, the total human environmental impact (I) is evaluated by the product of three terms: the population (P); the per capita consumption (C); and the environmental burden created by unit of consumption.

I=PCB (1)

The need to drive the environmental problems to international level was reported by the Club of Roma, “Limits to Growth”, that was published in 1971 [5].

According to the modern economic theory [6] the environment is like a biological organism. The economic rises require increasing quantities of natural resources and consequently harmful residues are generated affecting the environment and the life quality into this system. So residues should be treated before coming back to the environment.

3. Bioresources concerns and perspectivesBiomass is the final product of the photosynthetic process in which

Nature stores solar energy in a great variety of chemicals. Great attention is required from science to improve yields and productivity, still considered low. A new green revolution is on the way since 1970. It promotes the intense use of advanced biotechnologies aiming at cell, protoplasts, tissue, and vegetable organs cultures through the use of genetic engineering to multiply species and plants and to create new ones more stable and resistant to diseases and plagues [7]. The photosynthetic capacity of each vegetal culture depends on the light intensity; the quantity of CO2 absorbed per unit of time of vegetal organism; their foliar surface; and also, the type of mechanisms (C3 or C4), involved in this process [8]. Of course, it depends on the temperature and CO2 availability, as well as on the amount of nutrients used. The conversion of radiant energy into chemical energy can be represented by the following equation, in which,

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8 photons

the chemical term [CH2O] represents one-sixth part of a glucose molecule [7].

CO2+H20 [CH2O] + O2 (2)In general, the maximum theoretical yield of the photosynthetic process is about 6.5% but the practical yield obtained is no more than 2.5% for sugar cane as well as algae, one of the best species in terms of photosynthesis yield, which depends on the availability of advanced strains and solar incident radiation in the plantation [9]. So, in tropical countries the solar radiation is available for long daily periods at higher temperatures, which still contribute to the productivity of the C4 plants, to be superior to C3 plants [8].

3.1 Biomass state of artEnergy and agriculture are two fundamental factors that affect

human progress and development. In the initial stages, agriculture not only provided food, but also met the household, agricultural, and industrial energy needs of the people through fuelwood, charcoal, crop and forest residues, animal dung, and so on. However, biomass is the only form of energy that can be used to produce liquid fuels substituting traditional fossil fuels. In this sense, tropical countries show a great potential to use biomass. According to Fernandes´s doctorate thesis (A gestão do conhecimento aplicada à biodiversidade com foco em plantas medicinais brasileiras, UFRJ, Rio de Janeiro, 2002), which presented data on the main potential of vegetable species by countries, where Brazil have the great number of species (57,000), followed by Colombia (45,000), Venezuela (24,000), Mexico (18,000), Peru (18,000), Australia (26,000), United States of America (22,000), Indonesia (18,000), Europe (12,000) and Japan (3,000). Clearly, Latin America region shows the biggest potential in terms of species that could be used to the production of food, fiber, chemicals and pharmaceuticals products.

Biomass can be used either for energetic and non-energetic needs. Non-energetic uses are associated with the biomass components characteristics and their separation to provide food, feed, fiber, as well as, drugs for medicine. The energetic use of biomass can be used in two different ways: in the first, denominated traditional, the biomass consumption is very high, inefficient and non-ecological, bringing severe consequences to health and economic development. This traditional use of biomass involves mainly burning to attend rural needs in developing countries. Today, about 2.5 billion of people use fuelwood, charcoal, agricultural waste and animal dung to meet their daily energy needs for cooking and heating. In many countries, these resources accounts for over 80% of the total household energy consumption. In the second way, denominated modern, biomass could be converted into biofuels or driven

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to electricity cogeneration in sugar cane ethanol units, pulp and paper factories, in district heating installations, or even as synthesis gas, as shown in Table 2, according to Goldenberg [10].

Table 2: World’s Biomass Energetic Use: Present Status

Forms ofBiomass Use

Energetic Use (Mtoe)

I-Traditional 950.0II- Modern 216.0 Bioethanol 16.0 Biodiesel 1.6 Electricity 32.0 Heat 166.0III-Total 1,116.0

Source: [10]

3.2 Biomass potential and land availabilityIt is now convenient to evaluate the availability of biomass and land

to attend biofuels world demands. In these sense, the study proposed by the European Renewable Energy Council-EREC, 2006, concerning to Renewable Energy Scenario to 2040 presents two scenarios for the insertion of renewable energy in the world’s energy matrix up to the year 2040. Quite similar to the strategy adopted in the IEA study, The World Energy Outlook,2006, EREC authors proposed the Advanced International Policy–AIP scenario, that assume already regions active involvement, while, in the second, called Dynamic Current Policy–DCP scenario, considered less internationally cooperative, but intensive in national policies, specially in developed countries. In Table 3 data on the DCP scenario shows a relevant participation of renewable energy in the world’s primary energy supply. According to this scenario, renewable will almost double its participation up to 2040, and biomass will contribute with almost 16% of the total primary energy, corresponding to 60% in relation to 2004 contribution, thus being the most representative renewable participation. Meanwhile, wind and other forms of solar will grow faster than today’s patterns.

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Table 3: Renewable Energy Future Scenario according to EREC (c)

(DCP-Scenario on Millions ton of oil equivalent – Mtoe)

Types of Renewable Energy 2001 2010 2030 2040 (%)

on 2040I-Total Primary Energy Supply

10,038 11,258 15,347 17,690 100.0

1- Biomass 1,080 1,291 2,221 2,843 16.07 2- Conventional hydro 223 255 296 308 1.75 3- Small hydro 9.5 16 62 91 0.51 4- Wind 4.7 35 395 580 3.28 5- Solar PV 0.2 1 110 445 2.51 6- Solar thermal 4.1 11 127 274 1.55 7- Solar thermoelectric 0.1 0.4 9 29 0.16 8- Geothermal 43 73 194 261 1.47 9- Ocean 0.05 0.1 2 9 0.05II-Total renewable 1,364.5 1,682.5 3,416 4,844 -III- % Renewable 13.6 14.3 22.0 27.4 27.4

(c) European Renewable Energy Council - EREC

According to data on land availability presented by Leal and Leite [2] and available on FAO-statistics site, the total world land used today is about 13,400 Mha, from which the main uses are: arable land=1,400 Mha; perennial crops=136 Mha; under grass land=3,400 Mha; under forests=3,900 Mha. A considerable portion of the unused land is not suitable for cultivation, like deserts, iced-land, urban areas and mountains, leaving some 3,300 Mha for rain-fed cultivation.

Considering these numbers, IEA study proposed two distinct scenarios to evaluate future land required for biofuels in 2030. In the first, named Reference Scenario-RS, it is considered that biofuels will meet 4% of world road-transport fuel demand at 2030, up from 1% today. It accounts with 35.5 million of hectares which represent about 2.5% of arable land. In the second scenario, named by Alternative Policy Scenario-APS, it is assumed that biofuels production rises much faster, and biofuels will meet 7% of world road-transport fuel demand, and it accounts with 52.8 million of hectares, which represent around 3.8% of the arable land. Finally, considering the evolution of lignocellulose technologies, another study is called the Second Generation Biofuels Case. It accounts with 58.5 million of hectares, which represents 4.2% of arable land. If the second generation technologies based on lignocellulose biomass were widely commercialized before 2030, arable land requirements could be less per unit of biofuels output. The lignocellulose based technologies should start on large scale pushing the share of biofuels globally in road-transport demand to 10%, in 2030. It means that a significant share of the additional biomass needed, could come from regenerated and marginal land, currently used for crops or

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pasture, as well as from agricultural and forest residues and waste. Additionally, second generation technology has a higher conversion efficiency.

3.3 Microalgae promise and challengeMicroalgae cultivation in large scale could diminish considerably

land use, mainly, arable land, since biofuels production could come from arid and semi-arid land, in which microalgae could be cultivated. This alternative has not been considered in IEA studies. It is the opportunity to increase biofuels share in road-transport sector without competition with land for food production. Furthermore, microalgae present a much higher productivity than terrestrial crops and forest. They are present through out the biosphere and grow under the widest variety of conditions, ranging from freshwater to environments with extreme salinity, and are the most productive biochemical factories available.

The idea of producing microalgae in large-scale was first considered in Germany in the forties where it was developed the microalgae diatoms cultivation, which showed the capacity to store large quantities of lipids in laboratory scale with nitrogen deficit. At that time it was also studied the cultivation of the green algae, chlorella, which showed a faster rate of biomass productivity when used in high light intensity. Also, using the same approach it was achieved high protein yields, of about 50%, dry weight. These practices aimed to reproduce the same productivity either in laboratory and large scale [11]. Around 1951, it was developed a pilot experiment on microalgae cultivation in Massachusetts under the support of the Carnegie Institute of Washington. A large number of experiments were made and are registered in the book; “Algal Culture: from laboratory to pilot plant” [12].

A resume of the state of art [13] of the industrial capacity to produce add-value biochemicals products from microalgae reveals that until the year 2000, the large number of plants were located in Asia, where around 110 commercial producers of microalgae, cultivated several species like: Chlorella, Spirulina, Dunaliella, Nanochloris, Nitzschia, Crypthecodinium, Schizochytrium, Tetraselmis, Skeletonema, Isochrysis and Chaetoceros. These industrial units were responsible for half of the world’s biochemical production with an annual production capacity ranging from 3 to 500 ton. The Figure 1 shows how versatile microalgae are to attain society demand in terms of add-value products like, biological active components, pigments, proteins, as well as biofuels. Actually, it is estimated a productivity of approximately 70 ton/ha/year of algae when compared to 15 ton/ha/year of terrestrial plants. Chisti [14] presented an interesting review related with the microalgae potential to produce biodiesel, where he emphasizes that microalgae appear to be the only source of renewable biodiesel able to meet the global demand for transport fuels. Microalgae can be grown in both open-culture systems such as ponds, lakes and race ways, or in highly controlled closed-culture systems, similar to those used

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in commercial fermentation processes known as Photo-Bioreactor (PBR) [15].

Figure 1: Types of Biochemical’s Obtained from Microalgae.

Several processes have been developed to remove CO2 from the gaseous effluent of conventional coal-fired power plants. In the USA, these power plants are responsible for about 35% of the gas emissions coming from fossil fuels [16]. Some of them involve methods Flue Gas Desulphurization (FGD) which present cost ranging from US$ 35 to US$ 264 per ton of CO2 according to the data available at IEA Greenhouse Gas R&D Programme 2007. A pioneer study was made to apply in the Askelon power plant the use of photosynthetic process to capture the CO2 through microalgae cultivation systems after an adequate pre-treatment, before entering in the atmosphere. The relatively high content of CO2 in the fossil burning flue gas of approximately 14%, when compared to the 350ppm in the ambient air, has significantly contributed to increase the growth rates of certain species of microalgae Therefore, the photosynthetic system provides critical oxygen renewal along the recycling of carbon into potentially beneficial biomass [17].

So, according to Figure 2, instead of using expensive pure CO2 to grow microalgae, as in traditional technologies, it is possible to feed flue gas containing 14% of CO2, directly in the cultivating systems. Besides that, some NOx and SOx can be effectively used as nutrients for microalgae. These facts contribute to the process economics yields.

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Figure 2: Comparison of Marine Microalgae Productivity Using Coal Flue Gas: Pure CO2; Flue gas+ 0.1% SO2; IEC Flue Gas; Flue gas (by tanks).

4-Discussion of biofuels production systems Renewable resources are better distributed on earth than coal and

oil, and their exploration and uses involve a more complex situation concerning to rural communities way of life, mainly in developing countries, where many people still live under unacceptable life conditions. Central questions are concerned with land-use, farmers, commodity prices and their sustainability. Developing countries usually practice two types of agriculture: survival-agriculture [18], to supply rural families’ basic needs, using the worst agricultural practices concerning the environment and productivity; and modern-agriculture [19] characterized by intensive use of capital, pesticides and technology, which impacts negatively soils and a great number of species. In most of the tropical countries, genetic technology is still far away from the required standards used in developed countries.

Sustainability of the production systems seems to be a good strategy to achieve biofuels production without subsidies and regional protection. This situation reveals a profound lack of policies related to the use of natural resources.

Science has established the fundamentals related to the use, practices and yields of plant material. From the other side, fuels energetic markets are characterized by large sizes and low prices practices, which can only be achieved through large units, with economic scale. This is a challenge at the present moment for the agro-industrial production systems in many developing countries. Before that, certain principles should be observed concerning to agronomic yields of species, infrastructure facilities for proper land use, adequate use of agronomic residues and industrial wastes, evaluation of the energetic yields on the field and industrial activities, which is established through the methodology of Net Energy Ratio–NER [2]. These principles are observed inside a general concept called biorefinery which emerged in the seventies inside

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the wood American sector [20]. It has been applied to wheat in Europe. Since the first oil shock in 1973, two big problems were raised related to biomass conversion into chemicals: the economic competition of synthetic petrochemical products, versus the need to breakdown the lignocellulose complex to obtain the same products derived from oil. These processes are based on two different technological routes; bioconversion and thermochemical [2], which is shown in Figure 3. This Figure presents a general road map of agricultural materials and correspondent technological processes and steps considered for the production of biofuels and bioproducts, especially prepared to this paper.

The discussion on biofuel progress will be made in two different subsections: 4.1 updated progress on biofuels and 4.2 new generation of biofuels.

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Figure 3: Possible Routes and Processes for Biomass Refining

4.1 Updated progress on biofuels4.1.1. Bioconversion routes:

According to Figure 3, sugars, starch, inulin, cellulose, and hemicelluloses can be converted into ethanol, biogas and biohydrogen via bioconversion routes. The lignin component could be used to chemical purposes, as well as to attend process energy demand. These products can be considered the main components of several classes of agricultural products present in sugar cane, potatoes, wood and lignocellulose residues, as well as algae. Bioconversion routes involve basic technological unit processes like alcohol fermentation, hydrolysis, anaerobic digestion and fermentation, described in technical book reviews and publications [21]. Certainly, lignocellulose biomaterial is present in the biosphere in great quantity and it has a large potential to the production of biofuels. Its main components are, cellulose, hemi-cellulose and lignin, which should be separated through pre-treatments processes in order to convert cellulose and hemicellulose into sugars (C6 and C5), either by enzymes, acid, or combined process before its transformation into biofuels. Pre-treatment procedures are fundamental tools to achieve high separation yields of these components. Unfortunately, physical, chemical, and biochemical pre-treatments processes did not achieve the desirable performance to promote a high yield of the enzymatic hydrolysis process [22]. Also, the enzyme cost is still high.

4.1.2. Thermochemical routes: According to Figure 3, vegetable oils and lignocellulose feedstock

can be converted into biofuels and chemical products using thermochemical processes. Concerning to lignocellulose, they can be pulped, carbonized, gasified or liquefied through pyrolysis units, after that they can be converted into, chemicals (methanol, acetic acid, phenols, tars) biofuels and electricity. Pyrolysis consists in heating woody-like materials to temperatures slightly above 1000C to start thermal decomposition. A more active decomposition takes place above 2500C, and for industrial applications temperatures up to 5000C may be used. Above 2700C, thermal decomposition does not require any external heat source because the process becomes exothermic [23]. Since the beginning of the twentieth century, petrochemicals have substituted the use of wood pyrolysis for economic reasons. However, the shortage and the cost of fossil fuels have created new interests in the possibilities of wood pyrolysis, mainly to process municipal solid wastes.

The use of thermal processes like Biomass-to-Liquids (BTL) also is considered to produce hydrocarbons via Fischer-Tropisch, using synthesis gas from biomass. Concerning to the gasification process, the main difficulty is the great variety of cellulose residues and their low density, which require a large gasifier. So, it is necessary a biomass pre-treatment

unit linked with an adequate gasifier to produce and adjust the ratio H2/CO to feed the Fisher-Tropisch reactor through a shift reactor [24]. Two basic types of liquid products can be manufactured, namely, hydrocarbons and oxygenates, such as methanol. Furthermore, dimethyl eter (DME), which has a high cetane number, can also be obtained when methanol undergoes dehydration. An additive to provide lubricity to synthetic diesel was developed by Carioca [25], where a patent is in progress. Thus, advances in agriculture and biotechnology have made possible to produce lignocellulose biomass at costs that are significantly lower than the crude oil, about US$ 15 per barrel of oil energy equivalent.

4.1.3. Ethanol integrated and sustainable systems: biorefineryThe ethanol production from sugar cane in Brazil is a commercial

technology practiced which yields about 6000 liters of ethanol per hectare with a cost of about US$ 0.20 per liter. The conversion of sugar cane residues, like bagasse, leaves and straw through a hydrolysis unit coupled to the ethanol traditional plant is being considered as the second generation technology to increase ethanol production to about 13,000 liters per hectare [2]. In Russia, hydrolysis of wood is practiced in large scale using diluted sulfuric acid [23]. The use of acid shows a lower conversion of cellulose into sugars, besides the fact that its effluents cause environmental impacts.

In Figure 4, it is shown a new concept of biorefinery system to ethanol production integrated with microalgae cultivation and biodiesel production, which is being developed by the author. This concept attends to all the principles discussed in this paper. The first results of the modeling evaluation demonstrate that the NER-coefficient for this system [26] is about 16, higher than the traditional one, which is 8.32 calculated for the traditional ethanol distillery, later considered in this paper. It seems much more attractive; economically, energetically and environmental friendly.

Boiler and Turbo-generator

CO2

Effluent

HydrogenEthanol,

Methanol,Hydrocarbons

Vegetable oilsor

Biodiesel

ElectricEnergy

Feed

FinalEffluent

Microalgae Cultivation

Microalgae Processing(High flexibility)

Sugar CanePlantation

Alcohol Distillery

SolidResidues

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Figure 4: New Concept for Ethanol Biorefinery Conjugated with Algal Biomass

In Table 4 it is presented a comparison between three different processes for biomass conversion according to the second generation technologies discussed. They are: Biomass Integrated Gasification with Gas Turbine–BIG/GT, thermochemical and bioconversion.

Table 4: Products and efficiencies comparisons in converting one dry ton of biomass according to second generation technology

Products BIG / GT Thermochemical Biochemical

Ethanol (litres /ton, DM) -- 333 246Electricity (kWh/ton, DM) 1750 606 226Total efficiency (%) 35 50 33

Source: [2]

According to these data, thermochemical processes are not only more efficient in processing biomass, but also, much more flexible in terms of final products: ethanol, methanol, higher alcohols, diesel, gasoline, wax and other chemicals [2].

4.1.4. Starch and inulin based raw materials to ethanol production Starches are the major source of carbohydrates of great economic

importance. They come on industrial scale from grains, tubers, and roots and are consumed as food and feed for centuries. Starch occurs in granules constituted by different components: amylose and amylopectin, varying in relative amount among different source of starches [27]. Starch hydrolysis, using diluted acids, enzymes or a combination of these catalysts is required to obtain a large number of products which can be classified in three major groups: unmodified starch (high amylose starch, common starch, fine starch, pearl starch, and high phosphate starch); modified starch (acid modified, bleached, oxidized, cross-linked and stabilized); derived products (glucose, fructose, maltodextrin, maltose and dextrins). However, breadmaking and fermented beverages are among the early technologies of human civilization [28].

After the oil crisis in 1973, corn and cassava have been considered to the production of ethanol in the USA, in some Asian and Latin American countries, where sugar cane production is not suitable. Maize (Zea mays L. ssp.) known as "corn" is a cereal grain domesticated in Mesoamerica and spread throughout since Canada to the Andes. Hybrid maize, due to its high grain yield is preferred by farmers over conventional varieties. Cassava or manioc (Manihot esculenta) is a woody shrub of the Euphorbiaceae (spurge family) native from South America extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root. Cassava is the third largest source of carbohydrates for human food in the world, where Africa is the largest

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center of production. According to Figure 3, these biomaterials should be milled and the starch extracted before the main hydrolysis step is conducted. Normally, amylases enzymes are used to the liquefaction and saccharification of different types of starches, depending on the amylose and amylopectin contents. Starch hydrolysis is a well industrial established technological process [27] that requires a pre-gelatinization procedure to impart starch the capacity to form paste in cold water.

Actually, the USA is using about 20% of their corn to produce ethanol. However, the 20 billion liters represent only a little above 2% of the gasoline consumption, on the energy use [2]. China is the third largest ethanol producer in the world, with annual production around four billion liters, mostly from corn (maize), according to data from 2008 World Fuel Ethanol Production, prepared by Renewable Fuel Association-RFA, Washington, DC. India has a large sugar cane industry, and relies on it to produce almost two billion liters of ethanol a year. Thailand produced 300 million liters of ethanol in 2006. Thailand has seven ethanol plants with a combined capacity of approximately one million liters per day, just less than 360 million liters per year. Government policy calls for 1.1 billion liters per year around the year 2011. Japan produced around 114 million liters of ethanol in 2006. The Japanese Environment Ministry is requiring of all new cars to be able to run on a blend of 10% ethanol starting in 2010. Currently, petrol with 3% ethanol is allowed. Japan has already signed an agreement with Brazil to cooperate on ethanol use. Philippines produced 83 million liters of ethanol in 2006. The Philippine Senate approved the Biofuel Act of 2006 which promotes the use of native biofuels. The bill makes it mandatory for vehicle owners to use two kinds of biofuel: ethanol (E10) or biodiesel (B1), produced from sugarcane and coconut respectively.

Inulin producing crops have attracted very much interest of European countries because of its potential use as raw material for non-food application. In addition to that, European governments have decided to look for new alternatives to solve problems such as surplus production, narrowing of crop rotations, soil contamination and farmer subvention [29]. Inulin can be obtained either from microbial sources or from plants such as chicory (Cichorium intibus) and Jerusalem artichoke (Heliantus tuberous L.), which is a crop from tropical countries [30], cultivated in Europe, Canada, USA and Latin America (Brazil and Peru), due to its economical potential to be a source of inulin and fructose. An extensive study concerning to a selection of suitable yeast for fermentation and enzyme production for inulin hydrolysis was done by Laguna in his doctorate thesis, on “Genética e melhoramento de leveduras para bioconversão de extratus de Helianthus tuberosus L”, 1986, ESALQ, Piracicaba, Brazil . Among different yeasts tested, K. marxianus, K. Fragilis and C. pseudotropicalis were considered to be adequate for Jerusalem artichokes extracts fermentation. They were achieved in 12 hours with selected yeast and 9.78 0GL of ethanol production and a yield of 96.56%. Volumetric

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productivity reached 7.86g.l-1.h-1 and the specific productivity of 2.35g.g-1.h-

1. Pilot experiments are now confirming the bench scale data obtained. 4.1.5. Energy balance in ethanol production systems

In Table 5, it is presented data on energy balance in ethanol distilleries based on maize, switch-grass and sugar cane, considering the concept of NER. It involves the relation between the renewable energy output and fossil energy input considering the whole production chain. This parameter gives a clear idea of the how much fossil energy will be substituted through the use of a specific agro-industrial system.

Table 5: Ethanol distilleries energy balance using different feedstocks

ProcessesCharacteristic’s

MaizeGJ / ha. year

Switch-grassGJ / ha. year

Sugar CaneGJ / ha. year

Agricultural energy consumption

18.9 17.8 13.9

Biomass energy 149.53 220.2 297.14Energy ratio in agriculture 7.9 12.3 21.3Energy consumption in distillery

47.9 10.2 3.4

Ethanol energy content 67.15 104.4 132.56Net energy ratio (NER) 1.21 4.43 8.32

Source: [2]

In Table 5, it was considered data on the economic technology for ethanol from sugar cane and corn. Concerning to switch-grass only an estimative analysis was made, considering that lignocellulose will be a future important raw material for ethanol production. Clearly, the data reveals that the NER varies considerably depending on the feedstock, from 1.21 for corn to 8.32 to sugar cane, besides the fact that for sugar cane, biomass presents the highest energy content and the lowest energy consumption in distillery. These combined facts are responsible for the best NER for sugar cane. Starch and grasses requires additionally to sugar cane, a lot of energy in the pretreatment and hydrolysis steps. These data do not include corn stover and top leaves from sugar cane for ethanol production, as well as credits for co-products, but includes 8% surplus of bagasse.

4.1.6. Vegetable oils processing Vegetable oils were first used at war time when two technologies were

launched to the production of biofuels to substitute diesel oil. They were the cracking of vegetable oil soaps developed in China [31], and the transesterification processes developed in Belgium, named biodiesel [32]. Nevertheless, vegetable oils seem to be a valuable raw material with a multiple use in the food and chemical sectors. Oil-chemistry development is an alternative to replace a large proportion of petrochemicals [33], since they are renewable, biodegradable and free of toxic components.

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Vegetable oils are constituted of fatty acids, which are used to produce a large number of add value products used in the chemical industry, especially in the cosmetics and laundry sectors. Examples of these products are: synthetic detergents and lubricants, emulsifiers, paints and varnishes (drying oils), heavy metal soaps, soaps or fatty acids derivatives like: ethoxylated fatty alcohols, ethoxylated fatty esters, alkanolamines and ethoxylated alkylphenols.Additionally, two large recent uses of vegetable oils with great markets are synthetic lubricants and dielectric oil for electric transformers. They will impact the vegetable oil market bringing more competition due to environmental constrains. Just to give a quantitative idea, in some European countries, about 15% of the car lubricants use vegetable oils derivatives and the market for isolation oils are of about 10 million of gallons [34]. These applications will interfere drastically with the biodiesel market. Presently, there are three American patents (US Pat. 5,949,017; US Pat. 6,037,537; and US Pat. 6,159,913) and another one was submitted in Brazil (PCT/BR 2008/000223), concerning to vegetable oils substitutes to paraffinic and naphthenic dielectric oils .

4.1.6.1 Catalytic cracking of vegetable oilsDuring the world war, China Vegetable Oil Corporation [31] made a

pioneer study on the pyrolysis of vegetable oil soaps to produce hydrocarbons motor fuels, using tung oil. Reported data on soy yields to equivalent vegetable products per ton of crude oil were: 0.73ton of diesel oil, 60 gallons of gasoline and 0.05ton of tar. In Brazil, these experiments were repeated to evaluate the yields and chemical composition of the distillates under request of the Mines and Energy Ministry. Other extensive studies on catalysts have been made by Nunes in his doctorate thesis on “Hydrocraquage de l’huile de soja sur des catalyseurs au rhodium et au ruthenium supportes”, 1984, Paris, to break-down vegetable oils into hydrocarbons, as well as the elastomers present in the Hevea rubber tree which consist of approximately one-third hydrocarbons emulsion in water. As result of these researches, it was proposed to use catalyst to obtain small hydrocarbons fractions equivalent to gasoline and diesel components [35]. These results motivated the Brazilian Oil Company, Petrobras to run tests at REMAN-refinery in Manaus to use the Fluid Catalytic Cracking – FCC unit to catalytically process a blend of 10% of soy oil with gasoil at 4820C. Reported yields are: approximately, 10.71% of combustible gas, 11.64% of GLP, 31.50% of high octane gasoline, 37.50% of diesel and 8.65% of tar. It means a yield of approximately 69% of liquid fuels, almost equivalent to the result obtained from China Vegetable Oil Corporation [31]. These results made possible Petrobras to install a pilot unit to develop a new patented process named H-Bio [36].

4.1.6.2 Transesterification of vegetable oils

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Rudolph Diesel used straight vegetable oil when he invented the diesel motor. As shown in Table 6, triglyceride oils like canola have high viscosity as compared to diesel oil. To avoid this problem, during the wartime, Belgium researchers [32] proposed the use of transesterified oil, where a simple alcohol molecule, like methanol or ethanol can substitute an equivalent quantity of glycerol present in the triglyceride oil. A pioneer work was made to reproduce this process in laboratory scale, demonstrating the improvement of the transesterified soy oil properties comparatively to natural vegetable oil, as shown in Table 6, according to previous experiments made in our laboratory at Federal University of Ceará, Brazil.

Table 6: Diesel oil, canola oil, vegetable diesel and transesterified soya oil properties. Experiments developed at LDPP-UFC (d)

Main Properties DieselOil

CanolaOil

VegetableDiesel

TransesterifiedSoya Oil

Density (g/ml), 20º C 0.83 0.92 0.84 0.88Calorific value (MJ/litter)

38.3 36.9 38.0 33.3

Viscosity (mm2/s), at 37.8º C

3.86 37 3.5 4.7

Sulphur Content (%) 0.15 0.0012 0.007 0.001Cetane Index 48 48 50.1 44.6

(d) Product and Process Development Laboratory at Federal University of Ceará.

Even though this process has been practiced in large scale, a great number of problems related with the use of acid or basic catalyst are still being observed [37], [38]. This fact brings some environmental and economic limitations to this technology, which is nowadays receiving subsides everywhere. Certainly, the food market; the price and the low productivity of vegetable oils; and the lack of market for the glycerin produced as a biodiesel byproduct are the main constrains for the use of vegetable oils for the economic replacement of diesel oil.

4.1.7. Anaerobic digestion Under oxygen free conditions, anaerobic microorganisms convert

organic material (vegetable, animal or microbial) into biogas, an useful biofuel, rich in methane. Anaerobic digestion is the microbial conversion of degradable material into methane and carbon dioxide through an anaerobic treatment process optimized to reach a desirable result at a minimal cost. This type of treatment takes advantage of these facts and indeed is an attractive method to stabilize several types of organic waste and wastewater, manure, as well as plant material like microalgae. A considerable effort has been made to develop the biochemistry and the microbiology of anaerobic digestion, as well as new advances concerning

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to hydrogen production, according to the data on “Biohydrogen production by anaerobic digestion of organic waste, from Krupp and Widmann, at University of Dulsburg-Essen, 2009. Researchers worldwide made possible large improvements in scientific aspects of this process, like microorganism’s selection and characterization, in the biochemical kinetics, and also in the reactors engineering aspects to increase sludge retention and yields, mainly for wastewater treatment. Organic wastes differ widely in the relative concentration of organic materials and water. From one side, municipal sewage contains mostly water; from the other, forest and agricultural waste have a very high content of organic material. In Figure 5, the main steps involved in the anaerobic digestion of waste materials are shown: Hydrolysis and fermentation, acetate fermentation and methanogenesis.

Figure 5: The Main Steps of the Anaerobic Digestion

In spite of the current development related to the use of microalgae to produce biodiesel [39], [40], it is necessary to consider the use of anaerobic digestion to process microalgae for biogas production, and consequently, methane and methanol, as shown in Figure 3. This approach seems more adequate than biodiesel production, once it does not require microalgae drying, which consumes a lot of energy, reducing the NER-coefficient of the productive system.

The use of family biogas digesters with a capacity around 4 to 10 m3 was considered of great importance to achieve rural energy supply in China, around the seventies [41]. Since that time, China, as well as India, intensified the use of small biodigesters to process human wastes and animal manure. The rapid expansion of family biogas units made possible the development and construction of relatively simple biodigesters. This fantastic experience also made possible the development of large community biodigesters, ten times larger, aiming at to run processing machinery and also to generate electricity for the villages. Besides that, this technology undoubtedly makes possible the production of an excellent

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organic fertilizer. As a result of this effort, this technology has spread out all over the world, but still needs Government supports.

4.2 New generation of biofuels4.2.1. Biological production of hydrogen

Biological production of hydrogen is the most challenging area of biotechnology concerning environmental problems, because its combustion produces water. In this sense, biological hydrogen has been regarded as the future energy carrier due to its renewable character, which does not produce “greenhouse gas” CO2 in combustion due to its main consumption on fuel cell. Besides that, hydrogen has a high content of energy per unit weight. It requires low energy consumption in comparison with the hydrogen produced by electrochemical and thermochemical processes. This could be named as third generation technology of biofuels.

Gaffron, in 1939, made the first observation of hydrogen metabolism in the unicellular green algae upon illumination [42]. Since that time, research activity on this area has greatly increased. Light absorption by the photosynthetic apparatus is essential for the generation of hydrogen because the light energy promotes the decomposition of water molecules, releasing electrons and protons, and the transport of these electrons to ferredoxin [8]. It is important to observe that the photosynthetic ferredoxin (PeF) serves as the physiological electron donor to the Fe-hydrogenase and, thus, links the Fe hydrogenase to the electron transport chain in the chloroplast of the green algae [43]. Unfortunately, molecular oxygen is a powerful inhibitor of the Fe hydrogenase [44]. In the late 1999, Melis [45] discovered that the green algae, Chlamydomonas reinhartdtii could be forced to produce hydrogen under sulphur-free anaerobic conditions jointly with researchers at National Renewable Energy Laboratory-NREL, Golden, Colorado, which developed a preliminary cost analysis. Subjected to this condition, this alga switches from oxygen production (normal photosynthesis), to the hydrogen production. Melis found that hydrogenase is the enzyme responsible for this reaction, but this enzyme activity lost its function in the presence of oxygen. Thus, the procedure of the NREL researcher’s laboratory was to grow the algae under light with a normal sulphur-containing growth media, then centrifuge and wash the cells in growth media that did not contain sulphur. Based on these data, they developed a system using two continuous-stirred tank reactors for producing hydrogen continuously, where in reactor-1 cells are grown in a media with a minimal level of sulphur. PS-II is slowed and oxygen production remains lower than oxygen consumption for cellular respiration, but by bubbling the solutions with carbon dioxide and a small amount of oxygen, the cells are able to remain in reactor-1 indefinitely, obtaining some energy from photosynthesis and some energy through respiration of acetate in solution.

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Cells from reactor-1 are transferred to reactor-2, which is maintained under anaerobic conditions. Cells entering reactor-2, already have suppressed PS-II systems, so they will not cause reactor-2 to go aerobically as shown in Figure 3. Any residual oxygen is quickly consumed by the algae in reactor-2. All of these developments still require advances in genetic engineering to improve the efficiency of the photosynthetic process, now understood as performed in two stages.

5. Biofuels (ethanol and biodiesel) regional potential and pricesAccording to 2008 - OECD-FAO Agricultural Outlook Report 2008-

2017, a world summary of biofuels productions, ethanol and biodiesel is presented in Table 7, showing both a significant increase in recent years. The ethanol and biodiesel production in the USA (North America), and Brazil (Latin America) are the largest ones; however, some other regions and countries started producing ethanol from corn or cassava, in this period, as well. As referred in this table, global ethanol production should reach about 126 billion liters in 2017. Concerning to biodiesel it shows a higher production in the same period, while the Western Europe (EU 27) countries present the highest production. Biodiesel is expected to reach almost 24 billion of liters. Note that according to OECD-FAO studies the biodiesel prices are expected to remain above fossil fuels production costs.

Table 7: Ethanol and Biodiesel Production Data (2008-2017) and Average (2005-2007)

WorldRegions

Ethanol (Million of liters)

Biodiesel (Million of liters)

Average2005-07

Est.2008 2017

Average2005-07

Est.2008 2017

North America 22,240 39,777 55,174 1,475 2,224 2391Western Europe (EU27) 2,049 4,402 11,883 5,095 6,580 13,271Oceania developed 63 156 1,004 199 911 994Other developed 410 369 683 - - -Sub-Saharan Africa 80 91 145 7 19 123Latin America and Caribbean 17,684 22,629 41,347 168 978 2,907

Asia and Pacific 7,757 9,631 16,624 666 1,561 4,671TOTAL 50,283 77,055 126,860 7,610 12,273 24,357 Source: [2]

Concerning to biofuels prices, Schmidhuber, a Senior Economist with the Global Perspective Studies Unit of FAO made, in 2006, an important analysis on the impact of the rising demand for bioenergy on agricultural markets and prices, “Impact of an increased biomass use on agricultural markets, prices and food security: A longer-term perspective” which are presented in Figure 6. The analysis is based on the parity price

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among crude oil, petrol (gasoline) and ethanol concerning to various feedstocks and farming production systems (sugar cane, maize, cassava, lignocellulose, palm oil). The point where total costs for biomass-based energy production are covered by revenues from sales of bioenergy (ethanol, biodiesel, as well as other) is referred to as the parity price of given feedstocks. In Figure 6, it is shown the parity prices for a selection of agricultural feedstocks, farming systems and fuels (ethanol, diesel, BTL). According to Schmidhuber, the shaped diagonal line reflects a parity price line for the conversion from crude oil to petrol (gasoline) which allows mapping feedstocks parity price for crude oil into feedstocks parity prices for refined petrol.

Figure 6: Data on Parity Prices: Crude oil – Petrol – Ethanol

6-ConclusionsThe world is facing an unsustainable energy future due to the high

fossil fuels consumption in road-transport and power generation sectors. Thus, biofuels investments need to receive high priority and accomplishments. Biofuels are closely associated with bioresources uses and social development. It is absolutely necessary to harmonize biofuels development with the efficient use of fossil fuels which will still dominate the global markets in the next three or four decades. It is important to consider the actual stage of vegetable oils use to attend food and chemical sectors, which are much more economically attractive, as well as the use of starch for the production of fine chemicals instead of its uses for energy purposes.

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According to Schmidhuber, a parity price line which allows mapping feedstocks indicates that the break-even points, stays at US$ 28/bbl for sugar cane producers in Brazil’s south-centre region, the most developed; at US$ 35 / bbl for the average, in Brazil; at 38US$/bbl for large scale cassava-based ethanol production, in Thailand; at US$45/bbl for palm oil-based biodiesel, in Malaysia; at US$58/bbl for maize-based ethanol, in the United States and up to nearly US$100/bbl for BTL production, in Europe.

According to IEA scenarios three distinct proposals were established concerning land required for biofuels production in 2030 to meet world road-transport demand: In the first, biofuels will achieve 4%, using 35.5 million of hectares (about 2.5% of arable land); in the second, 7%, using 52.8 million of hectares (about 3.8% of the arable land); and in the second generation biofuels case, 4.2% of arable land using 58.5 million of hectares (about 4.2% of arable land). In this last case, arable land requirements could be less per unit of biofuels output, since a significant share of the additional biomass needed could come from regenerated and marginal land, currently used for crops or pasture, as well as from agricultural and forest residues and wastes. Additionally, second generation technology has a higher conversion efficiency. So, arable land is a limited resource to attend world biofuels demand.

Based on this preliminary set of data, it is possible to establish the following technical scenarios for biofuels: Before 2030, four main technological routes should be considered: 1) To use as much as possible liquid effluents and solids residues to generate energy (heat, electricity) and biofuel (biogas), mainly in rural areas to avoid deforestation; 2) To develop microalgae cultivation systems in areas with high insulation rates, since microalgae offer a much higher productivity than terrestrial crops and forest, changing considerably the need for arable land use for energy; 3) To focus on the recycle of residues and the capture of CO2 from power plants and alcohol fermentation units to grow microalgae to produce biodiesel, minimizing the environmental impacts; 4) Investments should be focused on R&D to become viable the second generation of technologies to convert lignocellulose materials into ethanol through bioconversion, as well as lignocellulose material into hydrocarbons through thermochemical Fischer-Tropish process (BTL). After 2030, great effort should start from now to become viable the biological production of biohydrogen before 2040, considered a future energy carrier due to its high energy content and no production of “greenhouse gas” CO2 in combustion systems. So, a deep effort is required to biofuels achieve a desirable participation on world fuels demand.

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[32] Chavanne, C.G. Procede de transformation d´huiles vegetales em vue de leur utilization comme carburants. Patente BE 422,877. Bélgica, 1938.

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José Osvaldo Beserra Carioca, graduated in chemical engineering at Federal University of Ceara, (1969); received his M.Sc. (1972) and D.Sc.(1976) degree in applied thermodynamics at (UFRJ/COPPE). He made his post-doctorate studies in Germany (1978), Birmingham - England (1989), Israel (2000). He used to be member of the Editorial Board of the magazines, Biomass (1980-1990) and Bioresource Technology (1991-1999) - Elsevier Applied Sciences-England. He is consulting for process evaluation from the Environment Ministry and full Professor at Federal University of Ceará.

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