Biofuels Production and Processing Technology

M.R. Riazi, David Chiaramonti, M.R. Riazi, David Chiaramonti

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781351651103
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Fossil Fuels
• Index: Technology & Engineering

The importance of biofuels in greening the transport sector in the future is unquestionable, given the limited available fossil energy resources, the environmental issues associated to the utilization of fossil fuels, and the increasing attention to security of supply. This comprehensive reference presents the latest technology in all aspects of biofuels production, processing, properties, raw materials, and related economic and environmental aspects. Presenting the application of methods and technology with minimum math and theory, it compiles a wide range of topics not usually covered in one single book. It discusses development of new catalysts, reactors, controllers, simulators, online analyzers, and waste minimization as well as design and operational aspects of processing units and financial and economic aspects. The book rounds out by describing properties, specifications, and quality of various biofuel products and new advances and trends towards future technology.

1
Introduction

Biofuel Production and Processing Technology

M.R. Riazi and David Chiaramonti

CONTENTS

1.1Introduction

References

1.1Introduction

The term “biofuel” refers to a liquid or gaseous transport fuel, such as ethanol, biodiesel, hydroprocessed vegetable oils and lipids, upgraded bio-pyrolysis oil (bio-oil), or biogas-derived biomethane, produced from biomass and renewable resources, such as lignocellulosic plants, starch or sugar crop plants, and the organic fraction of municipal or industrial wastes. The term “bioliquid” is instead used to indicate a liquid fuel used for energy purposes other than for transport, including electricity and heating and cooling, produced from biomass. As energy resources from fossil fuels (such as oil, natural gas, and coal) are being depleted or discouraged due to the associated greenhouse gas (GHG) emission and impact on global climate, the production and use of sustainable biofuels is considered crucial to fully deploy potential energy resources in the future. The International Energy Agency (IEA) projected that petroleum resources will be depleted around 2060. According to the IEA, currently about 2% of world energy needed for transportation is being produced from bioenergy. It is expected this figure will be increased to 27% by 2050 (IEA, 2016). The U.S. biodiesel production increased from 343 million gal in 2010 to 1.278 billion gal in 2014, an increase of 272% during this 5-year period (AgMRC, 2016). The World Economic Forum in Davos recommended that 515 billion dollars a year be spent globally on clean energy development (including sustainable biofuels) between now and 2030 (Russia Today, 2009). Lowering CO₂ emission and increasing world energy security represent further cornerstones of biofuels in a global sustainable energy scenario. Main feedstocks for the production of biofuels include lignocellulosic biomass, starch, sugar, lipids, and wet biomass. Major products from these feedstock materials include syngas, bio-oil, bioalcohols, hydroprocessed vegetable oil, biodiesel, glycerol and biomethane, and pyrolysis oil as an intermediate energy carrier to be further upgraded downstream into transport fuels. Processes that may be used to convert the feedstocks into the products may include gasification, pyrolysis, liquefaction, fermentation, hydroprocessing, and transesterification.

Biofuels are often classified into four groups: first, second, third, and fourth generations. First-generation biofuels (also called conventional biofuels) are those produced from food-based land-using feedstocks such as sugar, starch, and lipids/fats. The main criticisms against this type of biofuel relate to their rather limited average biofuel yields per hectare and the potential negative impact on food production, as they require agricultural land for their production. Nevertheless, examples of efficient and sustainable biofuel production chains through conventional (i.e., first-generation) technologies also exist, as it is, for instance, the case of sugarcane chain in Brazil, or other sustainable crops in Europe, or the integrated production of food and fuel and the development of innovative crop rotation schemes. These shortcomings stimulated the development of second-generation biofuels, which are mainly produced from nonfood feedstocks such as straw, bagasse, forest and agricultural residues, and purpose-grown energy lignocellulosic crops. Nevertheless, the “land use” issue remains a key element to make these biofuels advanced according to the current European Union (EU) legislation, with the use of residues clearly promoted before agricultural land-consuming crops. Third-generation biofuels are based on the production and conversion of algal biomass and are presently under extensive research to maximize yields and lower production costs. Fourth-generation biofuels are carbon-negative ones and are still in the research and development stage for direct conversion of solar energy into fuel using cheap and widely available raw materials (Aro, 2016). At present time, more than 99% of biofuel production relates to first- and second-generation biofuels, which are the topics covered in this book. A schematic of possible biorefinery processes is shown in Figure 1.1 (from Chapter 19). Details on biofuel classifications, types, and chemical compositions of raw materials and products are given in Chapter 2. The chapter also briefly reviews various processing technologies for the conversion of different raw biomaterials to various products.

FIGURE 1.1 General schematic of biorefineries for both energy-driven and product-driven categories. (From IEA, Bioenergy: Sustainable biomass supply chains for biorefineries—IEA task 42 update, Fourth International Forest Biorefinery Symposium, Maria Wellisch, Agriculture and Agri-Food Canada, Montréal, Quebec, Canada, February 3, 2014, http://www.iea-bioenergy.task42-biorefineries.com/upload_mm/3/9/d/0b150a14-ebfe-49b5-bad5-daaa507b065f_IEA%20Task%2042%20Feb%202014%20MW%20Montreal.pdf.)

Statistical data on production of biofuels, trade, and demand are presented in Chapter 3. Global production and consumption of various types of biofuels in different parts of the world over the last 15 years is also presented in this chapter. Estimation of biomass potential over the next three decades until 2050 is presented as well. Economy of biofuel production, price change with time, and comparisons with fossil fuels are discussed with extensive data and 36 figures along with environmental issues and GHG mitigation potential of biofuels.

Process development and design/operation of units for the production of biofuels largely depend on the physiochemical properties of the raw materials as well as the products for each process. In addition, safety and utilization of biofuels require certain properties and specifications. These properties are discussed in Chapter 4 for biogas, biohydrogen through the fermentation process, liquid biofuels such as bio-oil from woods, as well as solid biofuels and biomass raw materials. Elemental analysis (C, H, O, S, N, etc.); content of major elements in solid fuels (Al, Ca, Fe, Mg, P, K, Si, Na, and Ti) and minor elements; standard test methods; measurement of heating value; specifications for liquid biofuels as recommended by American Society for Testing and Materials (ASTM) standards for physical properties such as flash point, Ca and Mg contents, alcohol control, water and sediment contents, viscosity, density, ash, cloud point, carbon residue, acid number, oxidation stability, glycerin content, and P, Na, and K contents; thermal stability; as well as distillation data are presented in Chapter 4.

As said, a wide range of raw materials can be used to produce biofuels through different processes. Availability of feedstocks in different parts of the world is an important factor in choosing the most appropriate local options for biofuel production. This is the topic covered in Chapter 5, which discusses various types of raw materials, including sugar and starch energy corps, grass, oil crops, palm oil, soybean oil, jatropha curcas oil, croton nut oil, cocoa, rubber tree waste, industrial waste, forest residues, animal wastes, rice straw, wood-like residues, and other types of biomass that can be used as potential raw materials for biofuel production. A large amount of crop residues remains unused or burnt in the fields. In the absence of adequate collection mechanism, a considerable quantity of urban waste is disposed of without any utilization, while its disposal by burning contributes to increase the environmental pollution, as noted in Chapter 5.

A general overview of processes for the production of different types of biofuels under various geographical locations and environments as well as the classification of production routes such as physicochemical, biochemical, or thermochemical conversions is presented in Chapter 6. In this chapter, the process information and technology characteristics of the most important biofuel options are discussed, providing fundamentals for the following chapters in this book that deal with much more details. Processes such as transesterification, fermentation and digestion (anaerobic fermentation), and hydrothermal (carbonization, liquefaction, and gasification), pyrolytic (carbonization, slow or flash pyrolysis), electrochemical, and gas to liquid (Fischer–Tropsch [FT] process) processes are among the many processes analyzed in this chapter for various types of biofuels and feedstocks. In addition, mechanical pretreatment and feedstock preparation (pressing, washing, and drying) as well as the final product treatment of produced biofuels such as gas cleaning and conditioning are examined in Chapter 6.

Chapter 7 discusses standards and quality of various biofuels in conjunction with properties discussed in Chapters 4 and 9. The principal documents for quality determination are subdivided into three groups—regulations, standards, and codes—and discussed in detail in this chapter. The chapter begins with the introduction of the various standard organizations in the United States and the EU, followed by regulations issued by governments for safety in the use of biofuels. Biofuels’ quality specifications according to ASTM standards in the United States are introduced. Similarly, the quality specifications according to EN test methods for biofuels use in the EU are presented. These specifications include impurities and limits of concentrations according to various fuel quality standards in addition to important properties, such as acidity, appearance, and conductivities.

Chapter 8 discusses the production of bio-based hydrocarbons and chemicals (such as alkenes and aromatics) using biomass feedstocks. The focus has been on the introduction of commercial and industrialized processes using both thermochemical and catalytic conversions, with description of process conditions, reactor design, and kinetic models. Triglycerides and fatty acids are converted to bio-derived hydrocarbons through hydrodeoxygenation and catalytic cracking/isomerization, while lignocellulosic materials are converted through fractionation, fast pyrolysis, torrefaction, or gasification (to maximize syngas) to bio-oil, biochar, or biogas (syngas). Syngas is then converted to liquid hydrocarbons through the Fischer–Tropsch process or other catalytic steps. Bio-derived hydrocarbons can then be converted into aromatics or alkenes through a steam cracking process. Torrefaction is an anaerobic thermal process that converts biomass into a kind of coal-like material (torrefied biomass) with higher energy density than the original feedstock. In this process, heating of biomass is carried out in the absence of oxygen: the weight loss is nearly 30%, while energy loss is abou...