Preface

Alcohol fuels have been utilized from the 1970s to replace crude oil. Alcohol fuels have been actively used in Brazil and US. Their role and quantity were expected to increase dramatically during the high oil price period of the early 2000s when the crude oil price jumped from US\$20 to US\$140 per barrel. Unfortunately, the expected widespread usage was not accomplished due to several reasons, such as drops in oil price, feedstock limitation of edible resources, and resistance from existing energy infrastructures, etc. Brazil has been the key role model until now through many ups and downs in price and availability. US has also been actively involved in alcohol fuels by using locally abundant corn. Besides these two countries, the progress in market expansion in other areas of world is not active. In this sense, when considering whether the supplying capacity of alcohol fuels has been fully utilized worldwide, most people will agree that it's not the case and more efforts should be exercised to meet the demand for replacing fossil-fuel based liquid fuels with environmentally benign and non-food resources. Since alcohol fuels started to replace crude oil, the oil price dictates the market scale. With crude oil costing less than US\$80/barrel, alcohol fuels remain a niche market fuel source instead of one of the primary energy sources.

Alcohol fuels rely heavily on governmental allocated rations to add to the current petroleum-based liquid fuels. The current market has been dominated by cornbased and sugarcane-based alcohols in US and Brazil. The feedstock change from these 1st generation resources to lignocellulosic-based (2nd generation) and algaebased (3rd generation) resources, which are non-food feedstock, has not reached a mature level for wide acceptance in the market. The requirement for feedstock of non-food origin becomes a key part for the future alcohol fuels. Unfortunately, however, the non-food feedstock inherently exhibits heterogeneous characteristics in the converting process. Simply put, it's expensive than the product obtained from mass-produced rather-simple feedstock like corn or sugarcane.

World energy and the liquid fuel market has changed dramatically since the availability of cheap shale gas and shale oil. Although it seems irrational, there might come a time when it is no longer normal to guarantee the free procurement of liquid fuels through long ship lanes in some countries. Utilizing the available feedstock that has not been properly regarded as a legitimate resource due to economic and social reasons should be a focal point as a possible resource for alcohol fuels, with the additional benefits of reducing cost in energy imports and helping local economy. Lignocellulosic biomass and algal species are the feedstocks that suit the purpose. As described in this book, these 2nd and 3rd generation feedstocks are far away in proper economic competition with the 1st generation alcohol fuels, which have advantages in price and mature technologies. In most countries, simply importing the alcohol fuels made in US or in Brazil can be much cheaper than trying to manufacture it using local feedstock like molasses or cassava.

Whether alcohol fuels can compete with clean gaseous fuels such as shale gas and even with hydrogen or synthetic natural gas produced through excess electricity of wind/solar renewable sources may be an interesting topic of the future. For the time being, alcohol fuels should compete with fossil liquid fuels as well as with the 1st generation alcohol fuels that are easily available in the world market.

The current worldwide energy trend focuses on key conditions such as CO2 reduction in coping with climate change and increasing the use of renewable/ sustainable energy resources in an environmentally benign way. In addition to these conditions, alcohol fuel requires another condition that asks to use non-food feedstock rather than food resources. The current trend succinctly depicts more use of renewable resources like biomass and abundant ocean algae, which are typically in low energy density and difficult to convert.

The future of alcohol fuels could be classified as negative as was expected decades ago. Liquid fuel is being switched to clean gas or electricity in many transportation applications through CNG cars or electric cars. In addition, electricity generation from renewable energy like wind and solar is being pushed as a strategic energy policy by many OECD countries. The hydrogen society is now more realistic than the methanol society. In reality, however, it will take at least several decades to transform liquid fuels to other energy forms for transportation applications.

But even after reflecting all these adverse situations, when considering the poor availability of environmentally benign liquid fuel resources in most developing countries, it is clear that alcohol fuels should be pursued from 2nd and 3rd generation feedstocks, which are typically not utilized properly and are locally available in large quantities. The current technology level for the future types of alcohol fuels is not cheaper than petroleum-based or 1st generation feedstock. Technological breakthroughs are in great need in this aspect. In the development of the 2nd generation alcohol fuel technologies, in particular, pretreatment and enzyme technologies are key areas that need a major improvement for cheaper and reliable production. It can be said that finding the cheap feedstock was the most important factor in the 1st generation alcohol fuels, while finding a cheap enzyme is the key factor in the 2nd generation alcohol fuels.

In a broad sense, hydrogen and electricity will eventually replace liquid fuels. But it looks like this will take several decades for full societal adaptation even in the developed OECD countries. With the recent new crude oil production in Canada, Norway, Brazil, and Guyana, in addition to already stabilized world oil supply, an era of cheaper oil might come instead of peak oil. According to IEA, Southeast Asia has already become a net oil importer of 4 million bpd in 2018. Thus, attaining energy security should be a factor in considering alcohol fuels. Overall bioenergy including biomass-based alcohol fuels and syngas, biogas should be promoted in parallel. More specifically, the future direction of alcohol fuel, especially in developing countries, should be to maximize the utilization of biomass and wastes that are locally abundant but are not effectively used as resources for alcohol fuels. The reason is clear. There have not been adequate and economic converting technologies that can compete with cheap oil and with imported alcohol fuels. It should be noted that soils and climates in much of Africa have similar characteristics for biomass production to those in Brazil where the bio-alcohols infrastructure is well established. Africa and South America have great potential in increasing bio-energy products including alcohol fuels.

For the 3rd generation algae feedstock, recent concerted national efforts in Netherlands to transform the North Sea into an energy- and raw-material-generating region provide an important benchmark to the future of bio-fuels including alcohol

fuels. Increasing the macroalgae (seaweed) growth productivity and utilizing it for liquid fuels as well as for useful high-value compounds are the primary technical targets. Bio-butanol is one of the key target products that can replace diesel. It has been reported that sea-grown algae can yield the oil yield of more than 20 times the land-grown plants, which require vast land, water, and longer cultivation time. Algae is an essential future source of liquid fuel that can meet the renewable, sustainable, and CO2-minimizing standards.

The last few decades have seen maintenance of a stable energy supply chain worldwide. There might be an argument whether the future decades can lead to a time of energy supply chain disruption. When it comes to dealing with the worst-case scenario in securing liquid fuels, it's not a bad choice to make alcohol fuels that are made by locally available cheap resources. It has to be emphasized again that an important factor for alcohol fuels must be the technical/social capability in developing countries where no expensive energy infrastructure is available during the upcoming years.

The book was prepared with many depths on broad views on alcohol fuels that are not activated as predicted before. Nowadays active roles of renewable energy and hydrogen energy are more emphasized than the conventional alcohol fuels that are replacing transportation fuels. Due to more concerns on CO2 and environmental issues such as fine dust, society seems to go towards options that are more fundamental in changing the current liquid fuels infrastructure. Even though they are the final goals to achieve, there exists firm barriers before the actual implementation. Technical maturity and economic sustainability in renewable energies and in hydrogen economy are in the process of producing some successful cases, but are not yet fully realized in a widespread way.

Biological conversion methods are well documented in human history through brewing ethanol liquor, but the technological level cannot be said that it has reached the maximum efficiency with full accommodation in environmental aspects. A large-scale, environmentally benign, and economical way still needs to be found.

When the book concept was initiated, the title was chosen ambitiously as 'Alcohol Fuels – Current Technologies and Future Prospects'. The book intended to cover the various recent development areas with more than ten chapters. After reviewing the manuscripts for chapters, several authors withdrew to finally yield just seven chapters. Then there needed to be a decision whether to maintain the original title with only the seven chapters that cannot cover the recent advancement in many parts on alcohol fuels. In the end, it was decided to keep the original title since the key aspects are at least noted although they are not included in as detailed a description as hoped.

The book contains seven chapters with three sections. The first section deals with the technology status on alcohol fuels and its future direction. The second section talks about the ethanol production from lignocellulosic biomass, which should replace the 1st generation corn-based feedstock. The third section involves three chapters on the process and application of alcohol fuels. The book provides a brief introduction regarding the recent advances in alcohol fuel field that is in constant challenge from recent issues on CO2, shale oil, power-to-gas, and hydrogen. etc.

I'd like to thank all authors who shared their ideas and results for this book, and Ms. Marina Dusevic who helped with the entire reviewing/editing process during the

last nine months. The product might not be a marvelous work, but it can be a small signpost in the journey to reach the sustainable liquid fuel production in the form of alcohols.

> **Dr. Yongseung Yun** Institute for Advanced Engineering, Yongin, Republic of Korea
