Über die Autorin bzw. den Autor

Editors
Wim Soetaert,
Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium

Erick J. Vandamme,
Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium

Series Editor
Christian Stevens
Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium

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Biofuels

The use of biofuels is rapidly gaining momentum all over the world, and can be expected to have an ever increasing impact on the energy and agricultural sector in particular.

Biofuels covers the use and conversion technologies of biomass as a renewable resource to produce bioenergy in a sustainable way, mainly in the form of liquid and gaseous biofuels. It gives a broad overview of biofuel developments from both a technical and an economical angle. The different production technologies for biofuels that exist or are under development are extensively covered in depth, dealing with both first generation as well as second generation technologies. Market developments in the sector, including trends on prices, markets and growth are also discussed. The link between the technical and economical developments are indicated throughout the text. The interactions between the technical, economical and ecological aspects are clearly expressed in this volume and are actually covered here for the first time in a single comprehensive volume.

This comprehensive text will prove useful for chemists, biologists and engineers working in the emerging biofuels industry, for researchers and academics interested in the field, as well as for those active in conventional fuel companies. The book is also relevant to people active in policy or financing, either within the government, industry or academia. This volume offers an excellent source of useful information and allows reflection about the bio-based economy in general.

Topics covered include:

• Process Technologies forBio-ethanol Production
• Process Technologies for Biodiesel Production
• Bio-based Fischer-Tropsch Diesel Production
• Biomass Digestion to Methane
• Biological Hydrogen Production
• Feedstocks for Biorefineries
• Sustainability of Biofuels

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Biofuels

John Wily & Sons

Chapter One

W. Soetaert and Erick J. Vandamme Laboratory of Industrial Microbiology and Biocatalysis, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium

1.1 Fossil versus Renewable Energy Resources

Serious geopolitical implications arise from the fact that our society is heavily dependent on only a few energy resources such as petroleum, mainly produced in politically unstable oil-producing countries and regions. Indeed, according to the World Energy Council, about 82 % of the world's energy needs are currently covered by fossil resources such as petroleum, natural gas and coal. Also ecological disadvantages have come into prominence as the use of fossil energy sources suffers a number of ill consequences for the environment, including the greenhouse gas emissions, air pollution, acid rain, etc. (Wuebbles and Jain, 2001; Soetaert and Vandamme, 2006).

Moreover, the supply of these fossil resources is inherently finite. It is generally agreed that we will be running out of petroleum within 50 years, natural gas within 65 years and coal in about 200 years at the present pace of consumption. With regard to the depletion of petroleum supplies, we are faced with the paradoxical situation that the world is using petroleum faster than ever before, and nevertheless the 'proven petroleum reserves' have more or less remained at the same level for 40 years, mainly as a result of new oil findings (Campbell, 1998). This fact is often used as an argument against the 'prophets of doom', as there is seemingly still plenty of petroleum around for the time being. However, those 'proven petroleum reserves' are increasingly found in places that are poorly accessible, inevitably resulting in an increase of extraction costs and hence, oil prices. Campbell and Laherrre (1998), well-known petroleum experts, have predicted that the world production of petroleum will soon reach its maximum production level (expected around 2010). From then on, the world production rate of petroleum will inevitably start decreasing.

As the demand for petroleum is soaring, particularly to satisfy economically skyrocketing countries such as China (by now already the second largest user of petroleum after the USA) and India, petroleum prices are expected to increase further sharply. The effect can already be seen today, with petroleum prices soaring to over 90 $/barrel at the time of writing (September 2007). Whereas petroleum will certainly not become exhausted from one day to another, it is clear that its price will tend to increase. This fundamental long-term upward trend may of course be temporarily broken by the effects of market disturbances, politically unstable situations or crises on a world scale.

Worldwide, questions arise concerning our future energy supply. There is a continual search for renewable energy sources that will in principle never run out, such as hydraulic energy, solar energy, wind energy, tidal energy, geothermal energy and also energy from renewable raw materials such as biomass. Wind energy is expected to contribute significantly in the short term (Anonymous, 1998). Giant windmill parks are already on stream and more are being planned and built on land and in the sea. In the long run, more input is expected from solar energy, for which there is still substantial technical progress to be made in the field of photovoltaic cell efficiency and production cost (Anonymous, 2004). Bio-energy, the renewable energy released from biomass, is expected to contribute significantly in the mid to long term. According to the International Energy Agency (IEA), bio-energy offers the possibility to meet 50 % of our world energy needs in the 21st century.

In contrast to fossil resources, agricultural raw materials such as wheat or corn have until recently been continuously declining in price because of the increasing agricultural yields, a tendency that is changing now, with competition for food use becoming an issue. New developments such as genetic engineering of crops and the production of bio-energy from agricultural waste can relieve these trends.

Agricultural crops such as corn, wheat and other cereals, sugar cane and beets, potatoes, tapioca, etc. can be processed in so-called biorefineries into relatively pure carbohydrate feedstocks, the primary raw material for most fermentation processes. These fermentation processes can convert those feedstocks into a wide variety of valuable products, including biofuels such as bio-ethanol.

Oilseeds such as soybeans, rapeseed (canola) and palm seeds (and also waste vegetal oils and animal fats), can be equally processed into oils that can be subsequently converted into biodiesel (Anonymous, 2000; Du et al., 2003). Agricultural co-products or waste such as straw, bran, corn cobs, corn stover, etc. are lignocellulosic materials that are now either poorly valorized or left to decay on the land. Agricultural crops or organic waste streams can also be efficiently converted into biogas and used for heat, power or electricity generation (Lissens et al., 2001). These raw materials attract increasing attention as an abundantly available and cheap renewable feedstock. Estimations from the US Department of Energy have shown that up to 500 million tonnes of such raw materials can be made available in the USA each year, at prices ranging between 20 and 50 $/ton (Clark 2004).

1.2 Economic Impact

For a growing number of technical applications, the economic picture favours renewable resources over fossil resources as a raw material (Okkerse and Van Bekkum, 1999). Whereas this is already true for a considerable number of chemicals, increasingly produced from agricultural commodities instead of petroleum, this is also becoming a reality for the generation of energy. The prices given in Table 1.1 are the approximate average world market prices for 2007. Depending on local conditions such as distance to production site and local availability, these prices may vary rather widely from one place to another. Also, protectionism and local subsidies may seriously distort the price frame. As fossil and renewable resources are traded in vastly diverging measurement units and currencies, one needs to convert the barrels, bushels, dollars and euros into comparable units to turn some sense into it. All prices were converted into Euro per metric ton (dry weight) for a number of fossil or renewable raw material as well as important feedstock intermediates such as ethylene and sugar, for the sole purpose of a clear indicative cost comparison of fossil versus renewable resources.

From Table 1.1, one can easily deduce that on a dry weight basis, renewable agricultural resources cost about half as much as comparable fossil resources. Agricultural co-products such as straw are even a factor 10 cheaper than petroleum. At the present price of crude oil (> 90 $/barrel, corresponding to 400 [euro]/t in September 2007), petroleum costs about three times the price of corn. It is also interesting to note that the cost of sugar, a highly refined very pure feedstock (> 99.5 % purity), is about the same as petroleum, a very crude and unrefined mixture of chemical substances. As the energy content of renewable resources is roughly half the value of comparable fossil raw materials, one can conclude that on an energy basis, fossil and renewable raw materials are about equal in price. Also volume wise, agricultural feedstocks and intermediates have...