Transportation Biofuels

Pathways for Production

Alwin Hoogendoorn, Han van Kasteren

• Publisher: Royal Society of Chemistry
• Year: 2020
• Print ISBN: 9781788015042
• eBook ISBN: 9781839160172
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Biotechnology
• Index: Biological Sciences

The transportation industry is still largely reliant on fossil fuels, whose use and extraction have significant environmental costs. Biofuels produced from renewable resources biomass offer a more sustainable alternative. However, it is important that production methods should be energy efficient and that feedstocks should not compete with food sources. Biofuels that meet these criteria are sometimes referred to as second-generation biofuels.

The new edition of this book provides updates on the three previously discussed non-conventional pathways for second-generation biofuels, including new experimental results and pilot plant studies. It also includes a completely new chapter looking at developments in combining renewable electricity with fuel production and possible future directions for the transportation industry.

It is a useful read for researchers and industrialists working in biofuel development as well as postgraduate students studying fuel alternatives.

CHAPTER 1

Introduction

The transportation industry is still largely reliant on fossil fuels, whose use and extraction pose significant environmental costs. Biofuels produced from renewable resources like biomass offer a more sustainable alternative and their production currently amounts to 143 billion litres on a yearly basis. However, it is important that production methods should be energy efficient and that feedstocks should not compete with food sources. Biofuels that meet these criteria are referred to as second-generation biofuels.

Since approximately 2012, the EU Commission has introduced new policies aimed at starting the transition from conventional (crop/food-based) biofuels to biofuels from non-food feedstock that deliver greater climate benefits. In 2015, the EU parliament also set a 6% limit for the maximum contribution of first-generation biofuels and bio liquids to energy consumption in transport for the year 2020.

During the last decade, financial stress in the European transportation biofuels industry has been seen. There are huge differences between EU installed production capacity and actual EU production in both the fuel ethanol and the biodiesel industries (see also Section 2.1 and 4.1).

However, a positive side effect of this current financial situation is that innovation in industrial processes has been stimulated and transitions towards second generation biofuel production, along with improved efficiency and better financial results, may succeed more easily.

According to the authors, both the prospect of (future) declining oil production and unattractive profit margins for current production processes have resulted in the urgent need for new and more energy efficient production pathways for transportation biofuels.

With this book, we intend to provide insights into promising new and innovative pathways for the biological production of the current main transportation biofuels: biodiesel, ethanol and methane. The pathways we intend to describe are non-conventional and should provide higher product yields, less stringent feedstock specifications, lower chemical additive demands, lower waste production and much better energy balances when compared to the more traditional production methods for biodiesel and ethanol.

The two pathways described in Chapters 2 and 3 are both based on the biological conversion of syngas into either ethanol or methane. These two pathways are intended to have amongst other characteristics higher product yields, high energy production efficiencies, less complicated syngas cleaning and they can be produced from various kinds of lignocellulosic biomass. For these two pathways, a lot of attention is given to technological and engineering aspects like gasifier selection, syngas cleaning, process design, reactor configuration and product upgrading (be it either ethanol distilling and dehydration or biogas purification).

Enzymes can be used as catalysts in order to produce biodiesel that consists of 100 wt-% methyl- or ethylesters. The pathway described in Chapter 4 involves the use of enzymes in the production of biodiesel, which has the advantage of being more efficient, producing less glycerol waste and obtaining a 10% higher product yield. In addition to this, the biorefinery concept is also introduced in this book, where a biodiesel is produced in combination with valuable chemicals, which improves the economic benefits of the process, making it more feasible and efficient.

Chapter 5 focusses on biomass availability and biofuel sustainability, and additionally describes novel production pathways and transportation fuels that look promising for replacing existing processes and/or fuels in the future. Hydrogen produced via either electrolysis or water splitting is combined with CO₂ to form either conventional fuels or new promising fuels like formic acid. Lastly, the use of metals like iron is also discussed for application as future fuels for heavy trucks.

The content of this book provides not only a reflection of extended desk research but also shows practical experimental results from an engineering perspective. For each of the pathways, there is a comparison made to competing production methods (research and patents), bacteria/enzymes (types, metabolism, reactions, inhibition, and cultivation), process designs, and pilot or laboratory experiment results (when available), a discussion of fuel specifications and demands, and a balanced discussion of the general financial and technical feasibility.

Therefore, it is the authors’ intention to create a book that is appealing to scientists and students for educational purposes as well as professionals within the current biofuels industry with a special interest in innovation and novel pathways.

CHAPTER 2

Biological Conversion of Syngas into Ethanol

2.1 First Generation of Ethanol Production

Alcoholic beverages often containing 5–10 vol.% ethanol have been produced by mankind for thousands of years. Alcohol distillation in order to obtain a higher alcohol concentration is also known to have existed since ancient times.⁵¹ The world ethanol production amounts to 108 million m³ per year (2018 data;⁶⁸) with both Brazil and the USA (approximately 50% production share) as the main producing countries. The overwhelming majority of this 108 million m³ of ethanol production is used for transportation purposes. New fuel ethanol production plants are being built every year.⁵² The yearly production capacities of these new plants are often in the range of 100–400 million litres of ethanol in order to obtain the benefit of relatively lower operational and investment costs at large scale production plants.

The main EU feed stocks for alcohol production are molasses, starch, beets, C-sugar, wheat, and corn.⁴⁹ France, Germany, the UK and Spain are considered to be the EU's largest producers.

The current EU application of ethanol for transport fuel is around 80% of the total EU ethanol production, and equals about 5.3 million m³ per year (2017 data;⁵⁰). The total installed EU fuel ethanol production capacity amounts to 9.3 million m³,⁵² which means that many EU ethanol production plants are either temporarily out of operation or not reaching full capacity. A similar situation of financial stress can also be observed within the first generation biodiesel industry (see also Chapter 4). However, a positive side effect of this financial situation is that industrial process innovation has been stimulated and the transition towards a second generation of biofuel production, which provides better production and financial efficiency, may succeed more easily.

Starch containing feedstock will need to be treated using liquefaction and hydrolysis steps in order to produce sugars prior to fermentation. The residence time in the fermentation tanks where the ethanol is produced is often around 3 days (batch processes). The ethanol content after fermentation commonly varies around 65–80 g litre⁻¹. From this, an average ethanol production of 20–27 g litre⁻¹ fermentor volume per day can be derived.

2.2 Introduction of Biological Conversion of Syngas into Ethanol

This chapter describes a joint effort by the authors, Ingenia, Telos and Wageningen University, which was sponsored by the Dutch Senternovem NEO EOS programme. The project started in January 2007 and finished in December 2008 and was a follow up to an earlier desk top feasibility study that was executed in 2006.²⁸

The aim of this project was to develop a process for ethanol production by fermentation of syngas obtained by gasification of plant (residues) and waste materials. A lot of R&D effort is currently focussed on alcohol production by fermentation of sugars obtained by enzymatic hydrolysis of (hemi)cellulose. Drawbacks of this enzymatic pathway are still the enzyme costs. The main advantage of the syngas route compared to the enzymatic route is that it also allows for conversion of non-biodegradable feedstock components (e.g. lignin) into ethanol.

We calculated mass and enthalpy flows for ethanol production from lignocellulose via gasification and syngas fermentation, and hydrolysis and yeast fermentation (Figure 2.1). The gasification and syngas fermentation route consists of gasification (57% C to CO, 43% to CO₂, 100% H to...

Table of contents

• Cover
• Title
• Copyright
• Preface to the 2nd Edition
• Preface to the 1st Edition
• Contents
• Chapter 1 Introduction
• Chapter 2 Biological Conversion of Syngas into Ethanol
• Chapter 3 Biological Conversion of Syngas into Methane
• Chapter 4 Enzymatic Biodiesel
• Chapter 5 Sustainability and Future Directions
• Chapter 6 Concluding Remarks
• Subject Index