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Overview of bio energy technologies
Cellulosic ethanol production

Cellulosic ethanol production

Global ethanol production for energy purposes is currently around 30 billion gallons per year. Among the leaders in this industry are two countries – the United States, which accounts for more than half of world production and Brazil, whose share in world production is about 30% [1,2]. However, with an overwhelming preponderance, these statistics demonstrate the production of first generation ethanol, the raw material for which is food grade agricultural plants - wheat, corn, sugar cane, etc. This raw material characteristic of ethanol production is at the heart of the ongoing criticism of first-generation technology and is driving the development of second-generation technologies that use non-food biomass as raw materials, such as agricultural, forestry or municipal waste.
Second-Generation bioethanol production statistics are still not uniform and are mostly based on information from manufacturers, which makes it difficult to assess the development of this industry. For some countries, generalized information can be found, for example, in [3,4]. In this section, it has already been noted that the production of second generation bioethanol from cellulosic biomass in China in 2018 was estimated at about 20 million litres, and in Brazil in 2017 at 85 million litres [4]. These are certainly insignificant volumes and do not correspond to the importance of cellulosic ethanol as a separate type of renewable energy fuel. Several problems of a different nature hinder the further development of the industry. First, the biochemical conversion of cellulosic biomass is a much more complex technological process than the processing of first generation raw materials; secondly, large-scale investments are required for the large-scale development of the production of second-generation bioethanol; thirdly, bioethanol ranks among other different types of fuel, including fossil fuels, and depends on them, competes with them, not always successfully; Finally, the industry, having an opportunity to produce fuel, based on simpler and more proven technologies, should be able to rely on understandable financial and legislative incentives for organizing more complex and costly production, which is not everywhere and not always the case.
Second-generation ethanol production refers to biochemical conversion methods based on enzymatic or microbiological processes. If conventional bioethanol is obtained as a result of alcoholic fermentation of biomass with a high sugar and starch content, then for the conversion of cellulosic biomass it is necessary to first isolate carbohydrates from cellulose and hemicellulose and only then ferment them into ethanol. Since cellulose is a very stable substance that is difficult to destroy even by acid hydrolysis; special enzymes have been developed, and the process itself is called enzymatic hydrolysis. The nature of these processes and the search for effective enzymes are the subject of serious and numerous studies carried out by chemical and energy companies and research institutes. Among the most popular fermentation methods are yeast fermentation, microbial fermentation via acetic acid, and microbial fermentation via farnesene [5]. In addition, methods of pre-treatment of cellulosic biomass have found wide application, including steam explosion, ozone oxidation, ammonia treatment, etc. Detailed information on the physicochemical bases of processing and conversion of cellulosic biomass can be seen in [5-7].
Today, there are several dozen commercial and demonstration projects for the production of second generation bioethanol in the world, some of them are shown in Fig. 1. The leader in this area is the United States, although in recent years a significant number of enterprises have appeared in China. In Europe, this technology is receiving special attention in Finland, Italy, Austria and Sweden.

Figure 1. Examples of Advanced Biochemical (2G Ethanol) Facilities and Patenting Activity in the World

More detailed information on projects for the production of liquid biofuels from biomass, including Bioethanol 2G, can be found in [8-10].
Since the choice of the optimal biochemical conversion technology, including pre-treatment and fermentation methods, is largely determined by the properties of the feedstock, most companies are guided by their own technologies. In addition, bioethanol 2G units are often part of larger conventional bioethanol plants. Unfortunately, many companies are experiencing serious difficulties in the commercial production of bioethanol 2G, even to the point of bankruptcy. Moreover, these difficulties are typical for several manufacturers.

In 2015, DuPont commissioned one of the largest second generation bioethanol plants in the state of Iowa, US with a capacity of 30 million gallons per year. The company has developed a wide range of original enzymes for different stages of production of SPEZYME®, OPTIMASH®, DISTILLASE® and others. Generally, DuPont technology includes pre-treatment of the feedstock (remnants of corn plant stems and leaves)
– grinding and additional splitting; then the first stage of fermentation is carried out – saccharification to break down complex carbohydrates into simple sugars for fermentation; then the next stage of fermentation by means of patented strains of microorganisms; finally, during distillation, ethanol vapours are captured and condensed into liquid ethanol [11-13]. Despite the successful launch of the enterprise, two years later DuPont sold the plant in Iowa to the German company VERBIO, which announced its conversion to produce synthetic methane, and the fermentation technology was sold to Petron Scientech [14-15]. According to [3], there is no information on ethanol production by VERBIO in 2019. Thus, this project has apparently ceased to exist.

According to [16], Abengoa Bioenergy Biomass sold its Hugoton cellulosic ethanol plant in Kansas, USA to Synata Bio. As the buyer specializes in gas-to-liquid conversion, there is reason to believe that the plant will also be refurbished. At least [3] Synata Bio has no data on ethanol production. This loss may be most significant as the plant was built under US government guarantees and was seen as a flagship 2G bioethanol plant.
Beta Renewables, one of the largest cellulosic ethanol plants in Europe, was launched in 2013 in Crescentino, Italy. The raw materials for the production here are wheat and rice straw, as well as the local flower cane Arundo donax. The technology is based on the patented Proesa ™ technology and enzymes from Novozymes [9, 17]. In 2018, following bankruptcy, the owner of the Beta Renewables plant, Mossi & Ghisolfi Group, sold it to a subsidiary of the Italian oil and gas giant Eni [18].

Perhaps a more stable situation has developed in Brazil, where the production of cellulosic ethanol in large quantities is established by GranBio and Raízen using their own technologies on parallel lines of plants producing conventional ethanol. In particular, Raízen's technology includes the full chain of ethanol production and use, from growing sugar cane to selling ethanol at city gas stations.

Figures 2-3. Sugarcane cultivation (left) and harvesting (right), Brazil

After the raw materials are transported by trucks to the receiving and unloading point, a quantitative assessment of the sugar content is analysed, and then the sugar cane is crushed, heated in containers to 105oС and the juice is separated from the pulp. Following this, the components are separated into two streams  raw materials with a high sugar content, which are sent directly to fermentation, and the bagasse, which is subjected to additional hydrolysis. In addition, part of the bagasse is burned to generate electricity. After fermentation, the first and second generation ethanol is distilled, purified, and then distributed through the distributor network [19].

Figures 4-5. Raízen 2G Ethanol Plant in Piracicaba, Brazil

     Raízen 2G Ethanol Plant in Piracicaba, Brazil

Information on other technologies for the production of ethanol 2G can be found in [20-22].
Table 1 lists the top ten patent holders for cellulosic ethanol production over the past 10 years (2009 -2018), as well as their shares in the intellectual property register in relation to all patent holders. About 1650 patents prepared by 1011 applicants from 40 countries and issued in 33 patent offices around the world were selected for analytical assessment. Patents were selected where the authors indicated that the proposed technical solutions belong to technologies for the production of cellulosic ethanol at any stage of the production process, including the preparation of raw materials, fermentation, hydrolysis, distillation, etc.

Table 1. Leading patent holders on the subject related to the production of bioethanol 2G for the period from 2009 to 2018 and their shares in the register of intellectual property in relation to all patent holders

ratio, %
involvement, %
CompanyUSXyleco Inc.28.7598.1728.22
CompanyDKInbicon A/S2.3292.342.14
CompanyNLDSM IP Assets B.V.
OrganizationFRIFP (École Nationale Supérieure du Pétrole et des Moteurs)1.9561.861.21
CompanyUSVerenium Corporation1.8285.981.56
CompanyNLShell Internationale Research Maatschappij B.V.1.57981.54
CompanyUSCargill Incorporated1.4482.281.18
CompanyUSPoet Research, Inc.1.2676.250.96
CompanyUSBASF Enzymes LLC1.1991.231.09

Volume ratio - share of applicant documents in total number of documents
Ownership ratio - applicant's participation share in total number of documents
Market involvement ratio (bubble size) - volume ratio multiplied by ownership ratio

Source: Advanced Energy Technologies

As follows from the data above, the American Xyleco Inc. is the undisputed leader in this area, with American companies dominating among the first ten applicants.
It is obvious that cellulosic ethanol technology has a difficult history, and the prospects for further development are still unclear. Much here will depend on future breakthrough technical solutions if they contribute to the commercialization of the technology by reducing the cost of processes. The level of state support for projects will certainly play an important role. A detailed review of barriers to the development of cellulosic ethanol can be found in [23].

Cellulosic ethanol production. References

[1] Ethanol fuel by country / Wikipedia /
[2] Renewable Fuels Association /
[3] Focusing Forward. 2020 Ethanol Industry Outlook (PDF) / Renewable Fuels Association /
[4] Global Agricultural Information Network (GAIN) /  United States Department of Agriculture Foreign Agricultural Service (FAS) /
[5] Status of Advanced Biofuels Demonstration Facilities in 2012 / Bacovsky Dina, Ludwiczek Nikolaus, Ognissanto Monica, Wörgetter Manfred / A REPORT TO IEA BIOENERGY TASK 39 / 18 March 2013 /
[6] Biomass Fractionation Technologies for a Lignocellulosic Feedstock Based Biorefinery / Edited By Solange I. Mussatto / 2016, Pages xxiii-xxv /
[7] Bioethanol Production From Agricultural and Municipal Wastes Chapter / R.B. Nair, P.R. Lennartsson, M.J. Taherzadeh / Swedish Centre for resource recovery - University of Borås / September 2016 /
[8] Database on facilities for the production of advanced liquid and gaseous biofuels for transport /
[9] Cellulosic Ethanol (CE) An introduction to cellulosic ethanol technology / European Technology and Innovation Platform Bioenergy (ETIP Bioenergy) /
[10] Liste des principales unités de production de biocarburants avancés en Europe (PDF) / Frédéric DUPONT/ Juin 2013 / ValBiom /
[11] DuPont Celebrates the Opening of the World’s Largest Cellulosic Ethanol Plant / NEVADA, IOWA (PRWEB) OCTOBER 30, 2015 / CISION PRWeb /
[12] Innovative products designed to fuel your business forward / DuPont /
[13] Reform Energy: DuPont Cellulosic Ethanol / DuPont /
[14] VERBIO to transform DuPont’s Iowa cellulosic ethanol plant into a renewable natural gas facility / De BioRefineries Blog - noviembre 12, 2018 /
[15] DuPont divests its cellulosic ethanol technology / by Marc S. Reisch / October 26, 2019 | APPEARED IN VOLUME 97, ISSUE 42 / Chemical & Engineering News / https://
[16] Hugoton cellulosic ethanol plant sold out of bankruptcy / By Dan Voorhis, DECEMBER 09, 2016 / McClatchy /
[17] Beta Renewables Cellulosic Ethanol Biorefinery, Crescentino / Chemicals Technology /
[18] Versalis buys Biochemtex, Beta Renewables / By Erin Voegele | September 27, 2018 / Biomass Magazine /
[19] Ethanol / Raízen /
[20] Cellulosic ethanol commercialization / Wikipedia /
[21] 2G Ethanol Production 2G Ethanol production is direct, robust and reliable / GranBio /
[22] 2ND GENERATION ETHANOL / Praj Industries /
[23] What is still Limiting the Deployment of Cellulosic Ethanol? Analysis of the Current Status of the Sector / Monica Padella, Adrian O’Connell and Matteo Prussi / Applied Sciences 2019, 9(21), 4523 /