Handbook of Biofuels Production

Processes and Technologies

Rafael Luque,James Clark

• Publisher: Woodhead Publishing
• Year: 2010
• ISBN:
  9780857090492
• Topic: Business
• Subtopic: Industria estrattiva di risorse naturali
• Index: Business

In response to the global increase in the use of biofuels as substitute transportation fuels, advanced chemical, biochemical and thermochemical biofuels production routes are fast being developed.Research and development in this field is aimed at improving the quality and environmental impact of biofuels production, as well as the overall efficiency and output of biofuels production plants. The range of biofuels has also increased to supplement bioethanol and biodiesel production, with market developments leading to the increased production and utilisation of such biofuels as biosyngas, biohydrogen and biobutanol, among others.Handbook of biofuels production provides a comprehensive and systematic reference on the range of biomass conversion processes and technology. Part one reviews the key issues in the biofuels production chain, including feedstocks, sustainability assessment and policy development.Part two reviews chemical and biochemical conversion and in turn Part three reviews thermal and thermo-chemical conversion, with both sections detailing the wide range of processes and technologies applicable to the production of first, second and third generation biofuels. Finally, Part four reviews developments in the integration of biofuels production, including biorefineries and by-product valorisation, as well as the utilisation of biofuels in diesel engines.With its distinguished international team of contributors, Handbook of biofuels production is a standard reference for biofuels production engineers, industrial chemists and biochemists, plant scientists, academics and researchers in this area.

• A comprehensive and systematic reference on the range of biomass conversion processes and technologies
• Addresses the key issues in the biofuels production chain, including feedstocks, sustainability assessment and policy development
• Reviews chemical and bio-chemical conversion techniques as well as thermal and thermo-chemical conversion, detailing the range of processes and technologies applicable to biofuels production

Part I

Key issues and assessment of biofuels production

1

Introduction: an overview of biofuels and production technologies

R. Luque and J.M. Campelo, Universidad de Córdoba, Spain

J.H. Clark, University of York, UK

1.1 Introduction

The urgency to identify a more sustainable way forward for society has become clear with alarming trends in global energy demand, the finite nature of fossil fuel reserves, the need to dramatically curb emissions of greenhouse gases (GHG) to mitigate the devastating consequences of climate change, the damaging volatility of oil prices (in particular for the transport sector) and the geopolitical instability in supplier regions. Currently, energy and the environment are two key hot topics present in all European challenges for the future. With oil prices fluctuating month after month, a cost-competitive and stable solution is needed, especially with an expected 60% increase in the demand of energy for transport by 2030 (the sector expanding in the US A and Europe and specially developing in the newly industrialised and emerging economies of China and India).¹ Transport has also shown the highest rates of growth in GHG emissions in any sector over the last ten years (20% global CO₂ emissions, 25% UK emissions), with a predicted 80% increase in energy use and carbon emissions by 2030.²

In order to avoid this dependence on oil and to meet the sustainability goals with regard to GHG emissions originally proposed in the 1997 Kyoto Protocol (confirmed by the European Union (EU) in 2002), clean, secure and affordable supplies of transportation fuels that involve low-carbon technologies are essential.³

In this regard, biofuels can make a significant contribution in the short-to-medium term,⁴ contributing to energy independence, mitigation of climate change and rural development, being reported as one of the most promising solutions (but not the only one) to help meet targets on the use of renewables and reduced emissions.⁵ However, thoughtful analyses of some first-generation biofuels (conventionally produced from ‘food’ crops, including wheat, maize, corn, sugar cane, rapeseed, sunflower seeds and palm oil) have been recently showing that such alternatives may be little better than traditional fossil fuels, at least, in terms of overall carbon footprint and environmental damage, despite some very promising figures reported in terms of CO₂ emission savings from sugar cane bioethanol use in Brazil.⁶

In contrast, preliminary figures on second-generation biofuels (defined as those produced from non-food sources and including dedicated energy crops such as perennial grasses, short-rotation coppice willow and other lignocellulosic plants as well as waste biomass from agricultural, forestry, municipal solid waste, etc.) in terms of GHG emissions savings, carbon footprint and environmental damage (e.g. deforestation, biodiversity threat, food vs. fuel, etc.) are showing that these can significantly improve on first-generation biofuels. Nevertheless, most technologies for the production of second-generation biofuels from biomass/waste are still in their infancy and those under development require pre-treatment of the feedstock in many ways (to reduce acidity, floating solids, etc.). So they are far away from being optimised, requiring more research efforts in the future.

In this book, we aim to provide an overview of the different processes and technologies available and those under development for the production of biofuels, with special emphasis on second-generation biofuels produced from biomass. The various biofuels currently produced and/or under development can be grouped according to the processes and technologies employed for their preparation. These include chemical, biological and thermo-chemical conversion.⁷

In the first introductory chapters, details on policies, and socio-economic and environmental implications of the implementation of biofuels (Chapter 2) as well as on life cycle analysis (LCA) (Chapter 3) and the different biofuel feedstocks (Chapter 4) will be presented. The rest of the book is aimed to give a balanced overview on key technologies and processes for the production of biofuels, from first to later generation, as outlined in the next few sections.

1.2 Development of (bio)chemical conversion technologies

Chemical conversion involves a number of widely known and extensively employed processes since the nineteenth century. In fact, the chemical process currently in use for the preparation of biodiesel from biomass (transesterification of oils) is the same as has been used for many years. Feedstocks utilised for the preparation of biofuels are also very similar, with peanut, hemp, corn oil and animal tallow been partially replaced by soybean, rapeseed, recycled oil, forest wastes, trees and sugar cane.

First-generation biodiesel is currently the most common example of a biofuel prepared by chemical conversion. It is currently the most widely developed biofuel in Europe. In 2007, 19 biodiesel plants in the new EU member states were starting operations or were under construction/planning. Relatively large plants (with capacities of 100 000 tonnes/year) can be found in Lithuania, Poland and Romania.

The conventional methodology for the production of biodiesel involves the transesterification of triglycerides (TG) from vegetable oils (palm, corn, soybean, rapeseed, sunflower, etc.) with short-chain alcohols, including methanol and ethanol, to yield fatty acid (m)ethyl esters (FAM/EE) and glycerol as by-products (Scheme 1.1).

Scheme 1.1 Mechanism of the transesterification process to produce biodiesel.

However, non-edible feedstocks, including Jatropha, Brasicca species and microalgae oil, are becoming increasingly important nowadays for the production of biodiesel and are considered to be an important asset for future biodiesel production. The methods of biodiesel preparation can be classified into three types: chemical catalytic (base or acid catalysis: homogeneous and/or heterogeneous), biocatalytic (enzyme catalysis: homogeneous and/or heterogeneous) and non-catalytic processes. Several reviews on the preparation of biodiesel from different feedstocks utilising various technologies can be found in the literature.^8–12

The production of related biofuels via chemical processes (i.e. (trans)-esterifications) has also been reported. These biofuels have been specifically developed in research institutions, and commercial processes for their implementation as transport fuels are still under development (see Chapter 7 for more details). For more specific details, the readers are referred to Part II of the book (Chapters 5 and 6 as well as some related content in Chapter 22), in which more detailed information about processes, technologies and biofuels produced will be given.

1.3 Development of biological conversion technologies

Biological conversion technologies for the production of biofuels cover a range of fermentative and biological processes. These basic technologies have also been employed for decades in the production of ethanol (e.g. wine) from sugars via a two-step process of saccharification (hydrolysis of sugars)/fermentation using yeast (Scheme 1.2), followed by distillation of the alcohol produced to obtain a higher degree of alcohol purity.

Scheme 1.2 Production of bioethanol via fermentation of hydrolysed sugars from energy crops.

Bioethanol is therefore the most common biofuel prepared by biological conversion.¹³ It is the most employe...