PHOTOSYNTHESIS AND BIOFUELS
PHOTOSYNTHESIS AND BIOFUELS PRODUCTION: PROBLEMS AND PROSECTS ASHWANI KUMAR Energy plantation Demonstration Project Centre, Department of Botany, University of Rajasthan, Jaipur 302004 firstname.lastname@example.org. Phone 0141 2654100. Abstract Biomass contributes a significant share of global primary energy consumption and its importance is likely to increase in future world energy scenarios. Current biomass use, although not sustainable in some cases, replaces fossil fuel consumption and results in avoided CO2 emissions, representing about 2.7 to 8.8 % of 1998 anthropogenic CO2 emissions. Improved conversion efficiencies, besides a suitable management of biomass resources , could contribute significantly to reduce it unsustainable use, contribute a larger share of final energy demand and lead to a higher rate of fossil fuel substitution per unit of biomass energy. Also the global biomass energy potential is large, estimated at about 104 EJ/a. Hence, biomass has the potential to avoid significant fossil fuel consumption, of the current fossil energy consumption, potentially between 17 and 36 % of current fossil energy consumption and CO2 emissions potentially between 12 and 44 % of 1998 emissions. Modern biomass energy use can contribute to controlling CO2 emissions to the atmosphere while fostering local and regional development. There is significant scope then to integrate biomass energy with agriculture, forestry and climate change policies for example in the context of international measures directed at greenhouse gas emissions, such as clean development mechanisms. Utilization of biomass for energy and industry allows a significant quantity of hydrocarbons to be consumed without increasing the CO2 content of the atmosphere and thus makes a positive contribution to the Greenhouse effect and to the problems of “global change” as occurs in both industrialized and developing countries. Further the advantages from utilization of biomass include: liquid fuels produced from biomass contain no sulfur, thus avoiding SO2 emissions and also reducing emission of N0x. The production of compost as a soil conditioner avoids deterioration of soil and reduces pollution of waterways and groundwater. Improved agronomic practices well managed biomass plantations will also provide a basis for environmental improvement by helping to stabilize certain soils, avoiding desertification which is already occurring rapidly in tropical countries. Modern bio-energy technologies and bio-fuels are relatively benign from environmental view point and produce very little pollution if burned correctly and completely. The creation of new employment opportunities within the community and particularly in rural areas will be one of the major social benefits from the exploitation of biomass for energy, industry and environment. The specific research work carried out in the areas of biomass production and utilization in less fertile areas will provide satisfactory answers to the double challenge of energy crisis and forced deforestation in the country in general and semi-arid and arid regions of Rajasthan in particular. The possibility of conversion of biomass into strategic liquid fuels and electricity will make it possible to supply part of the increasing demand for primary energy and thus reduce demand for crude petroleum imports which entail heavy expenditure on foreign exchange. Family Euphorbiaceae ( Euphorbia antisyphilitica, E.tithymaloides, E. caducifolia E. royleana E. neerifolia etc and Ascelpiadaceae ( Calotropis gigantea and C. procera ) which have been worked out in previous years and will form the basis for further studies. Jatropha curcas is another potential plant for biofuel resources. INTRODUCTION Energy is a crucial and vital ingredient for the modern development of economic activities of our society. Although only one percent of the solar energy is fixed by the plants through the process of photosynthesis the annual biomass production is sufficient to meet global energy needs on renewable basis. Photosynthesis is the process required to convert the solar energy into chemical energy. The plants have developed C3 and C4 type of Carbondioxide fixation during course of evolution. C4 plants have been designated as more ‘efficient’ then C3. There is one family of moncots whereas 16 families of dicots which have C4 plants and sometimes a single family has C3 , C4 and CAM plants e.g. Euphorbiaceae. Plant tissue cultures provide an ideal technique to study the structure and function of photosynthetic apparatus in plants. Professor Dr Neumann while working in the lab of Professor F.C. Steward, FRS was first to demonstrate the presence of chloroplasts in plant tissue culture. Professor H.C. Arya, a great scientist with a broad vision gave me the research problem of greening of Arachis hypogaea callus cultures and its autotrophic growth. Though cultured cells developed chlorophyll but in most cases they were not able to grow atutotrophically and to raise autotrophic callus cultures was the biggest challenge of that time. When Professor Dr Neumann presented his pioneer work at International Plant tissue culture meeting at Leicester, (1974) I had an opportunity to listen to his lecture but several questions remained unanswered. Some of the questions which needed answer were (1) Do the plant cells in culture are able to develop the chloroplasts similar to the plant system ? (2) Do they have functional PS II and PS I activity. (3) What is the CO2 fixation pattern in cultured plant cells. Professor Dr Neumann invited me to work at his Institute of plant nutrition, Justus Liebig University, Giessen, Germany with financial support from Alexander von Humboldt Fellowship to find answers to some of these questions. Dr Ludwig Bender was also deeply involved in this work and he employed the technique of autoradiography coupled with GLC. Studies on the ultrastructural development of chloroplast, photosynthetic electron transport system elucidation of the path of carbon in cultured plant cells was carried out under able guidance of Professor Dr Neumann and I was able to establish the role of PEP carboxylase in photosynthetic carbon fixation in carrot as well peanut callus cultures. An oral presentation of results was made at International Photosynthesis conference held at Reading (U.K.) in 1977. It was a common assumption at that time that PEPcase is responsible of enriching the carbon for the subsequent fixation by RuBISCO in C4 and CO2 fixation by PEPcase in C3 plants could be a dark fixation. However by studying the ration of dark vs light fixation and employing the pulse and chase experiments using radioactive 14C labeling with carrot secondary phloem explants it could be demonstrated that light played significant role in initial 14C fixation which mainly recorded in C4 organic acids within a few seconds. A series of papers were published (Bender, Kumar and Neumann, 1985; Neumann 1995, Kumar et al. 1983a and b and 1984, Kumar and Neumann 1999 and Kumar et al., 1999 also see review Widholm, 1992). During Photobiology meet in USA (1980) noble laureate Professor Melvin Calvin invited me to visit his lab at University of California (Berkley Campus) and also introduced me to the topic of biofuel from biomass. Large number of plants belonging to family Euphorbiaceae and Asclepiadaceae were investigated for their potential to produce latex which could be converted in to petroleum products Attempts were made to increase hydrocarbon production upto 5 to 7 fold and proper agrotechnology was developed for their large scale cultivation (Kumar, 2008). During the recent visit I was thrilled to see Euro 1.27 per litre for biodiesel while diesel costed Euro 1.37 per litre at a petrol pump in Germany. Production and sale of biodiesel has become a reality in European countries. Rapeseed methyl ester is being used to produce bio-diesel. In European sub-continent. Recently Department of Biotechnology, Govt of India, has made significant progress through its micromission projects in developing agro-technology for large scale cultivation of Jatropha curcas our group has been actively involved in this research for several decades. The present paper reviews the photosynthesis, bio-fuels production problems and prospects. Energy is required for cooking, space and water heating, lighting, health, food production and storage, education, mineral extraction, industrial production and transportation. The energy consumption patterns largely determines the way in which people live their lives. It is estimated that biomass covers currently up to 15% of the world energy demand, almost 1/3 of all energy consumption in the Developing Countries. Some of the agricultural economy based countries which have around 70 percent of their population dependent on agriculture, utilize biomass and its products for getting energy. Burning wood is their primary source of energy. With increasing overall demand the bioenergy consumption is increasing in absolute terms. The great versatility of biomass as a feedstock is evident from the range of materials that can be converted into various solid, liquid, and gaseous fuels using biological and thermochemical conversion processes. Four broad categories of potential biomass feedstocks can be identified: (1) organic urban or industrial wastes; (2) agricultural crop residues and wastes including manure, straw, bagasse, and forestry waste; (3) existing uncultivated vegetation including stands of trees, shrubs, bracken, heather, and the like; and (4) energy plantations, which involve planted energy crops either on land brought into production for that purpose, land diverted from other agricultural production, or as catch crops planted on productive land. Due to the historically poor status of biomass-related R&D, and its neglect on the part of planners and development agencies, it has been very difficult to change biomass energy systems in terms of their production, harvesting, and energy conversion structures to changing socioeconomic and environmental pressures. Fortunately, this is now changing somewhat, so that there is an opportunity to use biomass efficiently for the production of modern energy carriers such as electricity and liquid fuels and to improve the lack of efficiency associated with traditional biomass fuels such as wood and charcoal. Ideally a successful biomass program should be sustainable and economical, taking into account all costs and benefits, especially spillover and indirect effects, including environmental and health aspects. The focus of this article is, exclusively, on liquid fuels. The term biofuel is used mainly to refer to liquid fuels. There are several reasons for biofuels to be considered as relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to the rural sector. Many of these aspects are discussed in this article. 2. Technical Applications Biofuels in their liquid form, for the purpose of this article, can be classified as follows: 1. Vegetable oils • Unmodified vegetable oils • Modified vegetable oils 2. Alcohols • Bioethanol • Biomethanol 3. Oxygenated components 2.1 VEGETABLE OILS Pure vegetable oils, especially when refined and deslimed, can be used in prechamber, indirect-injected engines such as the Deutz model and in swirl-chamber diesel engines such as the Ellsbett diesel model. They are also usable when mixed with diesel fuels. Pure vegetable oil, however, cannot be used in direct-injection diesel engines, such as those regularly used in standard tractors, since engine cooking occurs after several hours of use. All engine types allow additions of vegetable oils mixed with fuels in reduced and small proportions, but residues and cooking negatively affect short-term engine performance. Some vegetable oils also find application as lubricants and as hydraulic oils. In addition, they can be used in saw machines. In general terms, it is possible to substitute mineral oils for vegetable oils provided that appropriate additives are included. BIOFUELS AS SUSTAINABLE TECHNOLOGIES Vegetable oil can be obtained from more than 300 different plant species. Oil is contained mainly in fruits and seeds, yet still other origins exist. The highest oil yields can be obtained from tree crops, such as palms, coconuts, and olives, but there are a number of field crops containing oils. Climatic and soil conditions, oil content, yields and the feasibility of farm operations, however, limit the potential use of vegetable oils to a reduced number of crops. Apart from the previously mentioned semirefined oils, vegetable oils can also be used in the esterificated form. Diesel engines malfunction if an excess of carbon is present in the combustion process. It becomes necessary to split the glycerides causing an excess in the carbon composition. This can be achieved by treating oil with alcoholtransesterification or by cracking procedures. Ideally, transesterification is potentially a less expensive way of transforming the large, branched molecular structure of the bio-oils into smaller, straight-chain molecules of the type required in regular diesel combusion engines. The so called biodiesel fuels are oil esters of a biological origin. Rape oil methyl-ester (RME) and sunflower methyl-ester (SME) are two biodiesels derived from their corresponding oil seeds. ALCOHOLS Ethanol is a volatile liquid fuel that may be used to replace refined petroleum. It can be obtained from different feedstocks. Among them are cereals, sugarcane, sugarbeet, and tubers as well as cellulose materials, namely, wood and vegetable remnants, although production in these cases is much more difficult . Attention has been focused lately on other plants such as Jerusalem artichokes, which contain inulin (a fructose polymer), and on converting lignocellulosic materials into glucose to obtain ethanol. The ethanol yield from these products depends mainly on the content in fermentable glucides and on per-hectare yields. Ethanol from biomass can readily be used as a blender in gasoline. To elaborate ethanol, the biomass feedstock is first separtaed into its three main components: cellulose, hemicellulose, and lignin. Cellulose is hydrolyzed into sugars, mainly glucose, which are then easily fermented into ethanol. Hemicellulose can also be converted into sugars, such as xylose, but it is difficult to ferment to produce alcohol. Lignin cannot be fermented, but it can be used to provide energy for fermentation processes. There is no chemical difference between ethanol derived from biomass and fossil origin ethanol. Another advantage of ethanol is that is can lower the production of aromatic products found in high octane gasolines. Ethanol is currently produced in two separate ways: synthetic ethanol produced from ethylene derived from hydrocarbon, which is perferred for industrial uses due to the pureness attained (which can reach values of 99.9% in alcohol), and ethanol obtained from the fermentation of plants rich in sugar or starch, a process that is clearly advantageous when using gasoline as a fuel. Concerning methanol, although it can be produced from a wide range of raw materials (namely, wood, dry biomass in general, coal, etc.), at present, it is mainly obtained by synthesis from natural gas or gasoline. The technology for the production of methanol consists of ‘‘gasifying the cellulosic raw material to obtain a synthesis gas followed by the traditional processes used for fossil fuels whereby the gas is purified and its composition is adjusted for the synthesis of methanol” Biomass sources are preferable for methanol, than for ethanol (unless ethanol is used for specialized sectors such as agriculture). The final energy result is more positive when producing methanol because ethanol is a high-cost, low-yield product with problems derived from storage and effects on soil. Also, methanol is less volatile, thereby less dangerous in case of a traffic accident. Unexpected combustion could be extinguished with water, it pollutes less, it has no sulphur content, and it could be tranformed into a high octane gasoline that may be used in countries not ready to employ engines that are fed directly with methanol. That transformation implies a cost, but it would not be excessive. However, the problem with the production of methanol from biomass remains the optimum size of the present manufacturing units, which, having been designed for fossil fuels, are not readily suitable for a very different raw material. OXYGENATED COMPONENTS European legislation exists to promote the use of unleaded gasoline in the European Union (EU), but one of the technical problems that this gasoline faces is its decreased octane due to the reduction in lead content. This reduction in octane coincides with a demand for higher octane fuels on the part of the consumer. One of the options for solving this is to use oxygenated components of mineral origin as additives that ‘‘are characterized by a high RON in relation to petrol and have a high sensitivity (RON– MON)” To compensate for their high volatility compared to gasoline, one of the elements of the mix has be eliminated (generally butane). This fact implies added costs for the refinery since it must separate the butane from the gasoline, the refinery being obliged to sell the butane in another market at a lower price. Table 1: World Energy Consumption pattern. Table 1 : World Energy Consumption pattern. Energy used Biomass share Percent Total World 9.6 Bio TOE 1-1.5 Bio TOE 11-15% Asia 2.3 Bio TOE 0.6-0.8 Bio TOE >30% Africa 0.4 Bio TOE 0.2-0.27 Bio TOE >50% The proportion of bioenergy is particularly high in Africa (Table 1). In most sub-Saharan countries biomass counts for over 80% of all energy needs. As it is mostly used for cooking, fuel wood is almost exclusively used. A large biomass resource of straw and agricultural residues remains untapped. Biomass has a role to play in the current attempt to save the world’s climate and to find ways and means to implement the “Kyoto agreement”. The prospect that developing countries are going to increase substantially their greenhouse-gas (GHG) emissions is leading to global debates on the environment protection and bio-energy use. Highest growth rates are expected in Asia and Latin America. By 2020 the proportion of people living in cities in the developing countries are expected to double. Accordingly, energy consumption in the cities will grow over proportionally. In general cities and towns will see their energy needs quadruplicating over the next 20 years while it will grow by a “mere” 50% in the villages. United Nations is playing key role in planning and development of bio-energy programmes at the global level. FAO’s bioenergy programme bases its operations on the following concepts: a) bioenergy can stimulate diversification of agricultural and forestry activities; for example, through establishment of energy plantations with trees and crops; b) biofuels can provide locally the necessary energy to improve agriculture and forestry productivity; and c) bioenergy can attract investments to rural areas where most of the biofuels are produced. However, several barriers must be properly addressed and removed for the full utilisation of bioenergy potential. One of the main concerns is the availability of land for food and biofuel production. This issue is particularly important in developing countries where food security deserves the highest priority. The population growth rate is highest in the developing countries. Table 2 Summarizes the population growth scenarios. Table 2 : Future Trends of Population Growth (in Billion People) 1990 2020 World 5.2 7.9 European Union 0.36 0.38 Developing countries 4 6.4 The fact that nearly 90 percent of the worlds population will reside in developing countries by 2050 probably implies that local solutions for energy needs will have to be found to cope up with the local energy needs on one hand and environment protection on the other hand. Accordingly energy demand on global basis is higher in the developing countries. The energy consumption growth is shown in Table 3. Table 3: Future Trends of Primary Energy Demand (in Billion TOE) 1990 2020 European Union 1.3 1.6 Developing Countries. 2.5 7.3 Bioenergy systems Biomass conversion into energy carriers (biofuels) consists of a network of several stages and operations regarding multidisciplinary aspects such as: The process of photosynthesis and biofuel production, biofuel supply sources (such as forests, industries, farming activities, etc.), trade and market issues and energy conversion devices. The combination of all these processes and operations is generically called “bioenergy system”. There can be land competition between food and biofuel production and a proper analysis of local conditions is essential for developing an effective energy system. There are many technical, political, economic, environmental and social implications that must be properly understood to have bioenergy systems integrated into agriculture and energy policies and strategies. In general, the bioenergy systems are very site--specific and complex. At micro level, supply sources of a simple bioenergy system can include a single farm and the main biofuel produced is just fuelwood for charcoal-making to be sold in urban markets. In these cases, a’ simplified charcoal making scheme includes, among others, the following main unit operations: growing the fuelwood, harvesting the wood; drying, and preparation of wood for carbonization; carbonizing the wood to charcoal, screening, storage and transport to warehouse and distribution to the market points. On the other hand, the layout of wood “energy systems at macro level (such as provincial and/or national level) can be generically represented by the woodfuel balance scheme. In practice, field studies of area-based biofuel flow show that bioenergy systems are even more complex where different supply sources for biofuel production and different biofuel types are converted into energy. COMPARISON OF BIOENERGY WITH OTHER RENEWABLE ENERGY SYSTEMS: Advantages Significant environmental benefits as far as pollution concerns High potentiality (large areas of crop¬land - marginal land - semiarid land) Sufficient competitiveness of biomass as energy resource in comparison with hydrocarbon Possibility to penetrate all energy market (heat power - transport - chemicals) Possibility of bioenergy systems on very small scale (few KW) - or very large scale (hundred of MW) Positive effects on employment in rural areas for the biomass resource production Disadvantages * Need of supplying expensive energy feedstock * Difficulty in the identification of the most promising systems * Optimization of bioenergy activity requires very deep knowledge of wide sectorial competence (~100 sectors) * Need to adopt horizontal and vertical integration of sub-systems to improve the economic basis of bioenergy complexes * Water, soil, climatic, environmental constraints limiting the biomass productivity and the choice of plants optimization of the yields for different climatic regions.