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miércoles, 26 de abril de 2017

Corn fiber ethanol – Examining 1.5G technologies

Publication date: 26/04/2017
Last update: 26/04/2017

Introduction [1,2,3]

A first generation (1G) facility produces bioethanol by fermenting sugars from sugar cane, sugar beet or cereals seeds, whereas a second generation (2G) facility uses sugars found in lignocellulosic biomass (agricultural residues, lignocellulosic crops…). It is said that the hybridization of existing 1G facilities with 2G technology is the future hope for 2G biofuels in countries who currently have developed a strong bioethanol infrastructure. The hybridization allows to produce a more cost-competitive ethanol using agricultural residue that previously had no value as a feedstock and integrating the whole value chain.

In this context, there is a special mode of hybridization that take advantage of the cellulosic sugars hidden in the corn kernel fiber. Known commonly as 1.5 Generation (1.5G), the ability to convert corn kernel fiber to ethanol seems to bridge the gap between the production of ethanol from corn and cellulosic ethanol.

Corn fiber ethanol technologies are being rapidly adopted by corn ethanol refiners in USA who are attracted by the rise of ethanol and corn oil yields as well as the cellulosic incentive tax credits. In accordance with data provided very recently by Syngenta, there are approximately 12 million tons of corn kernel fiber feedstock already available at US dry grind ethanol plants each year that could produce a potential 1.5 billion gallons of cellulosic ethanol. However, many consider that this issue is simply boosting support for unsustainable conventional biofuel production from food. Is 1.5G the transition to cellulosic biofuels or a lifejacket for corn ethanol refineries?

This post will try to explore in an unbiased manner the conversion process, the controversy in the USA and the market technologies.

The basis of the corn kernel fiber conversion [4,5,6,7]

Corn ethanol is made from the fermentation of starch. Although it is a straightforward process, the significant energy inputs and the use of two different enzymes (starch hydrolysis and fermentation) raise the operating costs. Cellulosic ethanol is far more difficult and expensive to produce. Glucose must be liberated from cellulose before it can be fermented. Hemicelluloses are easier to break apart than cellulose but their sugars cannot be fermented by the same microorganisms that are used to ferment glucose. Adding to these difficulties, both cellulose and hemicelluloses are intertwined in complex structures that contain other molecules (primarily, lignin).

Figure 1. Corn Kernel anatomy (extracted from DuPont web page)

Corn kernels consist mainly of starch, but they also contain 10-12% fiber, as well as some protein and fat. The fiber consists of cell walls that contain cellulose and hemicellulose, together with a small amount of lignin. It also contains some starch. Fewer steps are needed to convert that fiber into cellulosic ethanol than corn stover and other lignocellulosic materials. This is because the feedstock is clean and homogenous (free from gravel and other impurities) and the corn kernel fiber contains little lignin to be separated from cellulose and its nature is less recalcitrant. In this sense, Novozymes has presented experimental results showing that equal conversion of corn fiber is achieved with one-third the enzyme dose compared to corn stover.

It is possible to distinguish two general techniques to transform the fiber into ethanol: processing it separately from the bulk of the starch or using unconventional pre-treatment methods of the whole corn kernels before fermentation. Below, in the section about technologies, representative examples of this two kind of techniques can be found.

The controversy in USA [4,5,6,7]

When implementing the expanded RFS (Renewable Fuel Standard) program in 2010, US Environmental Protection Agency (EPA) did not take into account cellulosic ethanol from parts of corn kernels. In a 2014 rule, it allowed the cell walls of the corn kernel (fiber) to qualify as a cellulosic biofuel. The cell wall was categorized by EPA as an agricultural residue. Facilities that are adding this cellulosic ethanol technology to existing corn ethanol facilities are able to produce not only corn ethanol, but also smaller amounts of corn fiber-based cellulosic ethanol to receive the cellulosic producer tax credit and qualify for cellulosic RINs in the RFS.

However, some sources sustain that corn kernel fiber is undeniably a food-based biofuel, as it comes directly from the edible part of the feedstock, even if it is not the whole kernel. Therefore, this cellulosic production would be supporting traditional corn ethanol, which has food price and land-use impacts.

Other point of the controversy is related to the starch that adheres to the fiber. The rule allows ethanol derived from that starch which adheres to the fiber to be classed as cellulosic (only in the case where the fiber is processed separately from the bulk of the corn starch). The EPA considers that it accounts for typically less than 5% of the mass of the fiber. Other sources cite much higher figures and some voices claim that starch is being lumped into the fiber category.

Market technologies

D3MAX [8,9,10]

D3MAX, LLC is a startup technology company created by BBI International in 2015 to develop and license BBI’s corn fiber-to-ethanol technology to ethanol plants in the US, Canada and other countries. BBI began developing the technology in 2007 and received a patent in 2012. The patent is now owned by D3MAX.

1. Description of the process and key features
D3MAX technology is a “bolt-on” solution for corn ethanol plants. The process can be installed without significant downtime or interruption of ethanol production. The feedstock is the wet cake that has been previously “cooked” by the ethanol plant resulting in low pretreatment temperature and pressure. The process converts the cellulose, the hemicellulose and the residual starch in the wet cake to sugars which are then fermented to ethanol. It requires low cellulase enzyme dose due to low lignin in wet cake and high conversion of cellulose to glucose in pretreatment. After fermentation, the fluid is distilled and dehydrated in the same manner as ethanol generated from corn starch. Water containing protein, lignin and other non-fermentables is removed from the bottom of the beer column and processed to produce a low fiber, high protein DDGS. Converting the fiber and residual starch in the wet cake to ethanol reduces the volume of DDGS by about 20%. The protein concentration is increased to about 40%. This kind of DDGS is suitable for feed for monogastric animals including swine and poultry.

Figure 2. D3MAX process (extracted from Reference 9)

2. Improvement indicators
- Overall ethanol yield is increased from 2.8 anhydrous gal/bu to 3.11 gal/bu (11%).
- Corn oil available for recovery is increased from 1.0 lb/bu to 1.5 lb/bu (50%).
- Dryer energy use is reduced by 20%.

3. Status
D3MAX finished the fabrication of a pilot system in February 2017. It was designed and constructed by Ohio-based AdvanceBio Systems based on the patent and the conceptual design provided by D3MAX. The skid-mounted pilot system has been delivered and installed at Ace Ethanol facilities in Stanley (Wisconsin, USA). The testing of the corn fiber-to-ethanol process and technology is currently underway with trials to be completed by June. After analyzing first pilot test data, the process has demonstrated better than expected results. Because of this, D3MAX plans to begin designing its first commercial-scale plant this summer with construction expected to begin this fall.

Figure 3. D3MAX pilot system installed at Ace Ethanol (extracted from Reference 9)

DuPont [11]

1. Description of the process and key features
OPTIMASH® enzymes developed by DuPont are specifically optimized to hydrolyze corn kernel fiber from different processes and various pretreatment conditions. These enzymes can be used for saccharification of fiber before fermentation or for simultaneous saccharification and fermentation (SSF) process to convert corn fiber into ethanol. When paired with pretreatment, they break down the chemical bonds in corn fiber to produce fermentable C5 and C6 sugars. Depending on the process, this additional ethanol may qualify as cellulosic under current US EPA guidelines.

2. Improvement indicators
With this technology, a typical 100 million gallons per year (MGPY) facility can produce 6-10 MGPY of additional ethanol and 30-40% more corn oil.

Edeniq [12,13,14,15,16,17,18]

Edeniq was founded in 2008 and is headquartered in Visalia (California, USA) with a field office in Omaha (Nebraska, USA). The company has developed processes for producing low-cost cellulosic sugars and cellulosic ethanol. It started to merge with Aemetis but the merger agreement was lawfully terminated in August 2016. Recently, Edeniq announced that it has filed a cross-complaint against Aemetis for fraud and negligent misrepresentation among other claims.

1. Description of the process and key features
Edeniq’s Pathway process is an integrated platform to produce cellulosic ethanol in existing corn ethanol plants. The platform combines the Cellunator with an enzyme cocktail to break down corn kernel fiber, releasing cellulosic sugars into the fermentation process. The Cellunator is a proprietary colloid mill jointly developed with IKA. It increases enzyme access to starch and pretreats corn kernel fiber for the cellulase action.

Figure 4. Integration of the Edeniq’s technologies into an existing plant (extracted from Reference 13)

2. Improvement indicators
- Edeniq’s Pathway Technology using existing fermenter and distillation equipment has produced up to an additional 2.5% of cellulosic ethanol yield.
- It has potential to increase yearly profits for a 120 MGPY plant by $7.0M from additional ethanol and corn oil and cellulosic credits.

3. Status
Edeniq’s technologies has been successfully implemented and approved in multiple corn ethanol plants:
- Pacific Ethanol. It began producing cellulosic ethanol using Edeniq’s technologies at its Stockton plant (California) in December 2015. It received its cellulosic ethanol registration in September 2016. According to recent news (see post), they will be also installed at Madera plant in California. Works are expected to be completed in the third quarter of 2017.
- Flint Hills Resources. US EPA approved registration of its 120 MGPY ethanol plant Shell Rock (Iowa, USA) for cellulosic ethanol production using Pathway Technology in December 2016.
- Little Sioux Corn Processors. US EPA approved registration of its 150 MGPY ethanol plant in Marcus (Iowa, USA) for cellulosic ethanol production using Pathway Technology in January 2017.
- Siouxland Energy Cooperative. It has successfully installed Cellunators and has started production of cellulosic ethanol using Pathway Technology at its 60 MGPY ethanol plant located in Sioux Center (Iowa, USA) in March 2017. With Edeniq providing technical support, SEC is preparing to file a registration with the US EPA for D3 RINs.

ICM [19,20]

ICM is a privately-held company established in 1995 and headquartered in Colwich (Kansas, USA) that provides innovative technologies, solutions and services in the sector of renewable fuels.

1. Description of the process and key features
ICM’s patent-pending Generation 1.5 Grain Fiber to Cellulosic Ethanol Technology (Gen 1.5), integrates a process for converting corn fiber to cellulosic ethanol with existing ethanol plants. The pathway to cellulosic ethanol is accomplished by combining mechanical, chemical and biological processes. It starts with ICM’s patented technologies, Selective Milling Technology (SMT) and Fiber Separation Technology (FST). SMT selectively grinds corn slurry to make the starch and oil more accessible in the entire process. With the further addition of FST, the fiber is separated from the stream by counter flow washing steps. The fiber stream is subjected to a dilute acid pretreatment that breaks down the fiber and releases the cellulose. The cellulose stream is converted to sugars with a state of the art enzyme cocktail and then the C5 and C6 sugars are transformed into cellulosic ethanol with advanced proprietary yeast. Gen 1.5 process was developed through collaborations with two world-leading biotechnology companies. Novozymes provided the enzyme cocktail which converts the cellulose stream into accessible sugars. DSM developed yeasts that ferment both the C5 and C6 sugars. The process also produces a high protein DDGS.

Figure 5. Integration of the ICM’s technologies into an existing plant (extracted from Reference 19)

2. Improvement indicators
This process increases ethanol yield up to 10% and corn oil yield up to 20%.

3. Status
The technology has been proven in both pilot (15,000 gal) and production (585,000 gal) fermentors in runs up to 1000 hours. ICM announced the construction of a state-of-the-art biorefinery next to its headquarters showcasing its cutting-edge technologies in March 2017 (see post). There, Gen 1.5 will produce up to 5 million gallons of cellulosic ethanol per year.

Quad County Corn Processors (QCCP) and Syngenta [2,21]

Formerly known as Adding Cellulosic Ethanol, Cellerate is a collaboration between Syngenta and Cellulosic Ethanol Technologies, LLC, a wholly owned subsidiary of Quad County Corn Processors.

1. Description of the process and key features
Cellerate does not suppose big changes of the conventional starch ethanol process. Pretreatment breaks down fiber, allowing mild whole stillage fiber treatment with pH low enough to prevent starch degradation. This reduces the time, chemicals and energy required. It allows the plant to load significantly more solids and capture residual starch, sugars and cellulosic component in a second fermentation process. In addition, Syngenta developed Enogen corn enzyme technology, an in-seed innovation that enhances ethanol production and delivers alpha amylase enzyme directly in the grain.

2. Improvement indicators
Performance results achieved at QCCP to date include: a 6% yield increase (from converting corn kernel fiber into ethanol) plus a 20% throughput increase (by combining Cellerate with Enogen) in ethanol production, higher protein feed co-products and improved oil yield.

3. Status
In 2014, QCCP was the first commercial cellulosic facility using corn kernel fiber as feedstock and achieved EPA certification to generate D3 RINs. To date, QCCP has produced more than 5.5 million gallons of cellulosic ethanol.
1 E. Ortega: “Hybridization: the evolution of 1G in Brazil”. The energy of change, Abengoa. Accessed on 19th April 2017.
3 S. Mueller: “Kernel of Opportunity: Corn Fiber-to-Ethanol”. Ethanol Producer Magazine, 21st January 2014.
4 S. Karpf: “Land and Food Risks of Cellulosic Biofuels”. ActionAid USA, October 2016.
5 A. Ernsting: “Subsidy Loopholes for “Cellulosic Ethanol” Promote Corn Profits, But Not Energy Independence”. In these times, Rural America Blog, 11th August 2016.
6. “RFA Pleased with EPA Approval of Corn Fiber as Cellulosic Feedstock”. Renewable Fuels Association, 2nd July, 2014.
8 Accessed on 20th April 2017.
9 M. Yancey: “D3MAX Technology Deployment Update”. D3MAX presentation.
10 “D3Max pilot test results at ACE Ethanol exceed expectations”. By BBI International in the Ethanol Producer Magazine, 12th April 2017.
11: “OPTIMASH® Enzymes Enabling New Advancements in Production of Renewable Fuel”. DuPont web page. Accessed on 19th April 2017.
12 Accessed on 20th April 2017.
14 “Edeniq brings fraud and other cross-claims against Aemetis”. Edeniq press release, 23rd March, 2017.
15 “Pacific Ethanol To Produce Cellulosic Ethanol at its Madera Plant”. Edeniq press release, 22nd March, 2017.
19 “Generation 1.5: Grain Fiber to Cellulosic Ethanol Technology”. ICM web page. Accessed on 21st April 2017.
20 “ICM advances pathway to cellulosic ethanol”. Ethanol Producer Magazine, 17 th June, 2016.
21 J. Schroeder: “Cellerate + Enogen = More Ethanol Production”. AgWired, 26 th April, 2016.

1 comentario :

  1. Product exhibits endo-cellulase, β-glucanase activity and β-mannase activities when assayed using insoluble AZCL-linked substrates as well as exo-cellulase and cellobiohydralase activities. cellulase