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Researchers at the University of California, Riverside led by Professor Charles Wyman, the Ford Motor Company Chair in Environmental Engineering, have developed a novel biomass pretreatment called co-solvent-enhanced lignocellulosic fractionation (CELF) to reduce enzyme costs significantly for high sugar yields from hemicellulose and cellulose—an essential development for the low-cost conversion of biomass to fuels.
As partners in the BioEnergy Science Center (BESC), the team from the Bourns College of Engineering Department of Chemical and Environmental Engineering and Center for Environmental Research and Technology (CE-CERT) have shown that CELF could eliminate about 90% of the enzymes needed for biological conversion of lignocellulosic biomass to fuels compared to prior practice. This development could mean reducing enzyme costs from about $1 per gallon of ethanol to about 10 cents or less, with an overall reduction in the cost of the production of cellulosic biofuels of 30% or more.
The findings by Wyman’s research group were outlined in a just-published paper in the journal ChemSusChem. Co-authors with Wyman are: Thanh Yen Nguyen, Charles M. Cai, and Rajeev Kumar, all of whom are students or research engineers in Wyman’s lab.
CELF employs THF miscible with aqueous dilute acid to obtain up to 95 % theoretical yield of glucose, xylose, and arabinose from corn stover even if coupled with enzymatic hydrolysis at only 2 mgenzyme gglucan−1. The unusually high saccharification with such low enzyme loadings can be attributed to a very high lignin removal, which is supported by compositional analysis, fractal kinetic modeling, and SEM imaging. Subsequently, nearly pure lignin product can be precipitated by the evaporation of volatile THF for recovery and recycling. Simultaneous saccharification and fermentation of CELF-pretreated solids with low enzyme loadings and Saccharomyces cerevisiae produced twice as much ethanol as that from dilute-acid-pretreated solids if both were optimized for corn stover.—Nguyen et al.
Diagram of a proposed biomass conversion process that integrates CELF pretreatment with Simultaneous Saccharification Fermentation (SSF) to produce ethanol. Source: UCR. Click to enlarge.
Research by the Wyman team focuses on turning lignocellulosic biomass into liquid transportation fuels. Lignocellulosic biomass is attractive because it is sustainable and abundant and inexpensive compared to oil. For example, lignocellulosic biomass costing about $60 a dry ton is equivalent in unit energy costs to oil at about $20 barrel. (Oil is currently selling for about $55 a barrel but has hovered around the $100 per barrel mark in recent years.) The challenge is to lower the cost of processing low cost biomass sources into fuels.
Biological processes favored for making liquid biofuels convert the hemicellulose and cellulose in biomass into sugars that can in turn be fermented into biofuels. However, the complex structure of lignocellulosic biomass makes it difficult for enzymes to release these sugars, and a pretreatment step using heat and chemicals is needed to reduce this recalcitrance enough to realize the high yields vital to economic success.
The lignin left in biomass after most pretreatments presents a particular problem by impeding enzyme access to hemicellulose and cellulose, thereby hurting product yields and requiring more enzyme at a substantial cost.
CELF, the pretreatment developed at UC Riverside, addresses those problems. In the ChemSusChem paper, the UC Riverside researchers outline laboratory results in which they compared the total achievable combined sugar yields between CELF pretreatment and dilute acid pretreatment, a current leading strategy, coupled with subsequent enzymatic hydrolysis in three timeframes with three levels of enzymes.
Using the dilute acid method, the sugar yield was only about 70% of the maximum possible after 14 days when two milligrams of enzymes were used. That percentage increased to about 85% in 14 days when 15 milligrams of enzymes were added.
By contrast, CELF pretreatment increased sugar yields to about 95% of the maximum possible regardless of whether two milligrams, five milligrams, or 15 milligrams of enzymes were added. Furthermore, the time required to reach these high yields dropped to five days when five milligrams of enzyme were used and two days when 15 milligrams of enzyme were used.
In addition, CELF is capable of dissolving and extracting up to 90% of the lignin in corn stover and even more for woody biomass. After pretreatment and enzymes release of the sugars from hemicellulose and cellulose, previous process strategies have focused on burning the residual lignin, which is a low value proposition. However, lignin has promise as a resource from which to make additional high value chemicals and fuels once it is extracted and depolymerized with CELF.
These findings are very significant because they establish a new pretreatment process that can dramatically reduce enzyme loadings and costs, thereby improving the competitiveness for biological conversion of lignocellulosic biomass to fuels. Understanding the mechanisms responsible for achieving these intriguing results can also suggest even more powerful paths to improving the economics of converting non-edible biomass into sustainable fuels.—Charles Wyman
The National Science Foundation contributed to making this project possible through their Graduate Research Fellowship Program. Initial application of CELF to biological conversion was supported by the UC Riverside Research and Economic Development Office of Technology Commercialization and the University of California Transportation Center.
The UC Riverside Office of Technology Commercialization has worked with the inventors to file a patent on the invention. CELF is now exclusively licensed by partners from CogniTek in Northbrook, Ill., who will be working with Cai and Wyman to launch a new spin-off company, MG Fuels, to commercialize the technology.
The BioEnergy Science Center is a US Department of Energy Bioenergy Research Center focused on enhancing science and technology to reduce the cost of biomass conversion through support by the Office of Biological and Environmental Research in the Department of Energy Office of Science.
Nguyen, T. Y., Cai, C. M., Kumar, R. and Wyman, C. E. (2015), “Co-solvent Pretreatment Reduces Costly Enzyme Requirements for High Sugar and Ethanol Yields from Lignocellulosic Biomass” ChemSusChem doi: 10.1002/cssc.201403045
At the Autostadt in Wolfsburg, Germany, Volkswagen showcased the new Touran MPV. The completely redeveloped Touran is the first MPV to be based on the modular transverse matrix (MQB); it offers a range of six new economical engines and an extensive line-up of assistance and infotainment systems. The public premiere of the new Touran will take place in the coming week at the Geneva motor show.
Being based on the MQB brings many advantages as far as design and construction are concerned, such as a distinctive long wheelbase with very short body overhangs allowing a groundbreaking use of space. Despite an increase in overall vehicle length and greater demands on safety and comfort it has still been possible to achieve a weight reduction of 62 kg compared to the previous model. This, together with improvements to the vehicle's aerodynamics, has resulted in a drop in fuel consumption: the engines, three gasoline (TSI) with 81 kW / 110 PS; 110 kW / 150 PS; 132 kW / 180 PS and three diesel (TDI) with 81 kW / 110 PS; 110 kW / 150 PS; 140 kW / 190 PS; are now up to 19% more economical. All models feature Stop/Start and battery regeneration (brake energy recuperation) systems as standard.
The third generation Touran has a distinctive new sporty look, thanks to a powerful and precise design that picks up on the reductive clarity of the previous model while adding a lightness and sporty feel. The interior has been given a makeover too. The space can be configured in a variety of ways with its newly developed fold-flat seating system, which also features ISOFIX anchor points on all seats. A luggage space of 1,040 liters (when loaded to roof height up to the second seat row) and a total of 47 storage compartments make the new Touran convenient for everyday use. The optional Pure Air 3-zone automatic air conditioner with anti-allergen filter ensures that the air inside the vehicle stays fresh and clean.
The wide range of new assistance and infotainment systems are pioneering features in this vehicle class. Along with Automatic Post-Collision Braking System as standard, the family-friendly best-seller (1.9 million units so far) is also available with the adaptive cruise control system ACC and Front Assist with City Emergency Braking; Traffic Jam Assist; Pre-Crash proactive occupant protection; Side Assist with Rear Traffic Alert and Trailer Assist, the trailer maneuvering system. New features in the Touran include an electric tailgate open/close mechanism; the automatic Easy Open tailgate function (activated by a movement of the foot); driving profile selection and high-performance LED headlights.
No fewer than five radio and radio navigation systems are available for the new Touran. DAB+ digital radio is available for all these systems. For the three top devices, Volkswagen will also be offering AppConnect with CarPlay (Apple) and Android Auto (Google) and MirrorLink for the first time, enabling a wide array of apps to be mirrored in the infotainment system display. The Touran has another optional item available, one that will particularly appeal to families: electronic voice amplification. This system uses a microphone in the front passenger area to relay speech to the rear seat rows via the speakers installed in the rear.
Southwest Research Institute (SwRI) has been awarded a five-year, $20.16-million contract by the US Environmental Protection Agency (EPA) to provide testing and analytical services related to vehicle emissions and fuel consumption.
Key areas of support include emissions characterization and technology assessment. SwRI can develop test procedures and equipment for regulated and unregulated emissions in light- and heavy-duty vehicles and components as well as marine, railway, aircraft, small engine, and other non-highway propulsion systems.
The scope of this contract is quite broad. It encompasses 25 areas, from fuels and lubricants to engine and emissions characterizations, as well as economic studies, general rule-making support, and coordinating peer review meetings. —Patrick Merritt, principal scientist in the Engine, Emissions, and Vehicle Research Division
SwRI can evaluate all types of fuels and additives, including conventional and reformulated gasoline and diesel fuels; alternative fuels such as methanol, ethanol, compressed natural gas (CNG), liquefied natural gas (LNG), liquefied petroleum gas (LPG), hydrogen and blends of hydrocarbon fuels; and electricity (supplied from batteries or fuel cells) for electric, partial electric, and non-electric hybrid vehicles.
The contract also calls for evaluating vehicles to ensure compliance with current emissions and other regulatory requirements and safety testing powertrains, batteries, and emission control systems. Technical services include evaluating prototype vehicle propulsion systems and related control, data acquisition, and sampling systems.
The contract through the EPA’s Office of Transportation and Air Quality (OTAQ) Assessment and Standards Division (ASD) uses SwRI’s expertise in its Office of Automotive Engineering — the Engine, Emissions, and Vehicle Research Division and the Fuels and Lubricants Research Division. Since its inception in 1947, SwRI has been engaged in the automotive industry and has performed contract work for federal environmental endeavors even before the EPA came into existence in 1970.
New testing guidance from EPA. On 23 February, the EPA issued a new guidance letter to manufacturers to refine and to clarify the procedures to be used by vehicle manufacturers in establishing vehicle road-load force and dynamometer settings for emissions and fuel economy testing. Road-load is the force imparted on a vehicle while driving at constant speed over a smooth level surface from sources such as tire rolling resistance, driveline losses, and aerodynamic drag.
This new guidance is effective beginning with the 2017 model year. Prior to MY 2017 the road-load confirmation procedures specified in Advisory Circular 55c (issued in 1988) will continue to be used.
When a vehicle is tested for emissions and fuel economy on a chassis dynamometer, the load from aerodynamic drag, friction, and tire losses associated with road operation must be simulated. Dynamometer settings are determined in two stages. First, actual on-road operation must be characterized, which is referred to as the road-load force specification. Second, a road-load derivation is performed to determine how much load the dynamometer will need to apply to simulate the road-load measured during the on-road test. EPA has previously established test procedures for both steps.
The method a manufacturer elects to use to characterize the road-load force is optional; however, the manufacturer is responsible for the accuracy of the road-load force specification and dynamometer settings. It is also the manufacturer’s responsibility to insure that the vehicles it produces conform to the road-load specification reported in the application for certification and used for certification and fuel economy testing.
EPA may test, or require the manufacturer to test, production vehicles to verify the accuracy of the manufacturer’s reported road-load specification and dynamometer settings. If specifications or settings are found to be inaccurate, EPA may require the manufacturer to retest the affected emission certification vehicles, retest fuel economy data vehicles and recalculate fuel economy label values, recalculate the GHG emissions and CAFE fleet averages, and correct the ABT credit reports.
The road-load force specification for all vehicles covered by a certificate of conformity and dynamometer settings used during emissions testing are required to be reported in the application for certification. EPA may deny, suspend, or revoke certificates of conformity where it finds that production vehicles have road-load forces that differ substantially from the road-load specification in the application for certification. Manufacturers failing to provide accurate vehicle road-load specification information in their applications for certification may also be subject to enforcement action, including civil penalties.
A number of automakers have had to reduce their fuel economy ratings for certain models over the past several years; the new detailed guidelines for EPA are designed to prevent these sort of changes.
EPA recommends the procedures found in SAE J2263 as revised 12-2008, and J1263 as revised 03-2010 (the test procedures in J1263 are applicable however the data must be analyzed in such a way to determine a 3 term equation of force) and J2264 as revised 01-2014.
EPA then provides specific guidance on vehicle preparation; the road or track facility; the road-load force specification and accompanying vehicle configurations; road-load force confirmation testing; EPA road-load force confirmation criteria; and corrective actions for revising the road-load force specification.