BIOFUELS SUPPLEMENT
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A bi-weekly summary of world developments on biofuels, produced by the Global Knowledge Center on Crop Biotechnology, International Service for the Acquisition of Agri-biotech Applications SEAsiaCenter (ISAAA)
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September 23, 2011
In This Issue:
News and Trends
- Techno-Economic Impacts of Pretreatment Options in Cellulose-Ethanol Production from Model Grass Analyzed
- Researchers Develop Cellulose-Ethanol-Production Yeast Strain Which Tolerates Furan-Inhibitors from Preteated Biomass
Energy Crops and Feedstocks for Biofuels Production
- Hydrologic Cycle Alterations Caused by Land Conversion for Bioenergy Crops under Climate Change
Biofuels Processing
- Engineered Yeasts for the Simultaneous Fermentation of Galactose and Cellobiose in Seaweed Hydrolyzates
- Hydrotreatment of Vegetable Oils for Biodiesel Production
Biofuels Policy and Economics
- Global Status Report from the Renewable Energy Network Policy for the 21st Century (REN21)
- Updated Study on the Opportunities of Biofuel Growth in the United States
* NEWS AND TRENDS *
Techno-Economic Impacts of Pretreatment Options in Cellulose-Ethanol Production from Model Grass Analyzed
http://www.biotechnologyforbiofuels.com/content/4/1/27/abstract
The production of ethanol from lignocellulosic biomass usually involves three sequential processes: (1) pretreatment, for lignin removal and liberation of complex carbohydrates in the biomass, (2) saccharification, for the conversion of the liberated complex carbohydrates into simple sugars, and (3) fermentation of simple sugars to ethanol. The pretreatment step offers the most number of technological options. Common pretreatment methods include the use of dilute acid, dilute alkali, hot water (hydrothermal treatment) or steam explosion treatment.
Cost-effectiveness is the primary consideration for the selection of a good pretreatment method, but techno-economic comparisons among different pretreatment options have been difficult. This difficulty has been attributed to the fact that process models have been developed only for individual pretreatment process, without looking at the "overall picture" of the cellulose-ethanol production process. A "lack of a consistent process modeling framework for the underlying ethanol production process" reportedly makes comparison difficult.
Researchers from Oregon State University (United States) attempted to develop process models for four common pretreatment processes under a "consistent underlying framework", in order to investigate "economic feasibility, compare energy consumption and sensitivity of the ethanol price to process parameters". Using a grass-based, tall fescue (Festuca arundinacea Schreb) straw as the model feedstock, they compared the techno-economic factors for the following pretreatment methods: dilute acid, dilute alkali, hydrothermal and steam explosion.
Among the highlights of the study are: (1) hot water (hydrothermal) pretreatment had the lowest unit ethanol production cost, due to non-use of chemicals while achieving comparably reasonable pretreatment efficiencies, (2) the capital cost of an ethanol production plant was lowest for steam explosion, due to a "high solids loading assumption" during pretreatment and hydrolysis, (3) ethanol production cost was shown to be sensitive to pentose fermentation efficiency, (4) energy from lignin residue was found to be sufficient to supply total steam requirement for the production plant (for all pretreatment options), (5) water use in the production process using steam explosion, (6) potentials for reducing ethanol production cost are in increasing pentose fermentation efficiency and reducing the costs of biomass (feedstock) and enzyme. The full article is published in the open-access journal, Biotechnology for Biofuels.
One of the effectsof lignocellulosic biomass pretreatment in cellulose-ethanol production is the generation of "furan-inhibitors", which can inhibit the ethanol-fermenting yeasts. Furan-inhibitors furfural (2-furaldehyde) and HMF (5-hydroxymethyl-2-furaldehyde) are by-products from the degradation of sugars during biomass pretreatment. These inhibitors are reported to damage yeast cell walls and membranes, disrupt yeast genetic material, and interfere with yeast enzymes' fermentation abilities.
Recently, researchers from the National US Department of Agriculture, USA developed a yeast strain that is more tolerant to inhibiting compounds present in bioethanol production. From their study, the researchers found out that the NRRL Y-50049 strain of Saccharomyces cerevisiae was capable of fermenting plant sugars into cellulosic ethanol in the presence/interference of inhibitory compounds. The researchers attributed the tolerance of the yeast strain to a specific gene in the yeast cell. The tolerance to furfural and HMF was attributed to YAP1 gene which provided the yeast's resistance to these compounds. More information can be obtained at the USDA website (URL above).
In order to meet increasing bioenergy demands, significant land areas are being converted to bioenergy crop plantations. These land conversions can contribute to changes to the ecosystem of the area, specially its hydrologic cycle. The hydrologic cycle can be affected since a bioenergy crops' high productivity is strongly linked with its water use.
Recently, researchers from the University of Illinois (USA) and Max-Planck-Institut für Biogeochemie (Germany) investigated the effect of bioenergy crops on the hydrologic cycle, with considerations for climate change. For their study, the researchers focused on the effect of two second generation bioenergy crops (miscanthus and switchgrass) on the hydrologic cycle of the Midwestern United States.
By using a "mechanistic multilayer canopy-root-soil model", the researchers were able to capture the eco-physiological acclimations of bioenergy crops under climate change, and predict how hydrologic fluxes are likely to be altered from their current magnitudes. Also, observed meteorological data and Monte Carlo simulations were used to characterize the variability range of their predictions. Using maize as a basis (since most land conversion to bioenergy crops plantation are from maize plantations), the researchers observed that miscanthus and switchgrass utilized approximately 58% and 36% more water, respectively, for total seasonal evapotranspiration under present conditions. This can reportedly lead to an altered hydrologic cycle for the region. Accounting for climate change, the increase in atmospheric CO2 decreased the evapotranspiration; however, the increase in air temperature and reduction in rainfall leads to a net increase in evapotranspiration due to climate change, which leads to the further alteration of the hydrologic cycle of the region. The full paper is published in the journal, Proceedings of the National Academy of Sciences of the United States of America (PNAS) (URL above).
Related information on Monte Carlo Simulations: http://www.palisade.com/risk/monte_carlo_simulation.asp
Seaweeds are considered as potential feedstock for biofuel production due to their high growth rates. The major sugar components in seaweeds which can be fermented to ethanol are glucose and galactose. However, in the fermentation of these sugars to bioethanol using current strains of yeast, galactose is only consumed after the glucose is depleted; thus, making the process inefficient.
Researchers from the University of Illinois (USA) recently engineered a new strain of Saccharomyces cerevisiae that is capable of simultaneously fermenting galactose and cellobiose (i.e. a dimeric form of glucose). In their study, the researchers introduced to the yeast, a gene which expresses a new sugar transporter and an enzyme that breaks down cellobiose at the intracellular level. Coupled with a modified process for the hydrolysis of seaweeds that produces cellobiose (instead of glucose) and galactose, biofuel production from seaweeds using this new yeast strain could become more efficient. This discovery, according to the researchers, greatly enhances the economic viability of marine biofuels for commercialization. The full paper is published in the journal, Applied and Environmental Microbiology (URL above).
Researchers from the National Institute of Advanced Industrial Science and Technology (Japan) and Instituto Politenico Nacional (Mexico) developed an alternative way of producing biodiesel from vegetable oil through the use of a method called hydrotreatment. In this process, hydrogen gas is used for the simultaneous hydrogenation of the C=C bonds in the vegetable oil and deoxygenation of the free fatty acids and triglycerides. This process, under the presence of the Ni-Mo/SiO2-Al2O3 catalyst, leads to the production of biodiesel and to a lesser extent, liquefied petroleum gas (LPG).
In their study, the researchers determined the feasibility of using the hydrotreatment process to produce biodiesel from three vegetable oils: (1) jatropha oil, (2) palm oil, and (3) canola oil. From their experiments, they found that hydrotreatment is feasible for the production of biodiesel. Among the three vegetable oils, the jatropha oil produced the highest biodiesel yield of 83.5% (wt.) with a corresponding 4.9% LPG yield. It was followed by palm oil with a biodiesel yield of 82.1% and LPG yield of 5.4% and finally, canola oil with 81.4% biodiesel yield and 5.7% LPG yield. The full paper is published in the journal, Energy Fuels (URL above).
The Renewable Energy Network Policy for the 21st Century (REN 21, an international multi-stakeholder organization promoting the "wise use of renewable energy worldwide") recently released its global renewable energy status report, "Renewables 2011". This yearly report tracks the global developments in renewable energy during the preceding year (2010), and provides an integrated perspective based on these developments.
The keyword associated with worldwide renewable energy developments in 2010 is: "continued growth". About 16% of the world's final energy consumption is said to be provided by renewable energy. In China, renewables are reported to account for "about 26% of the country's total installed electric capacity, 18% of generation, and more than 9% of final energy consumption in 2010". Emerging and developing economies have also been observed to have an increased share of "policies, investment, supply and use" of renewable energy.
In the Bioenergy/Biofuels sector, the report highlights the following" (1) about 2.7% of global transport fuels were powered by liquid biofuels in 2010, (2) The main players in biofuel ethanol are Brazil and the United States, accounting for 88% in global ethanol production; the United States has also overtaken Brazil as the leading ethanol exporter, (3) The European Union (EU) remained the "center of biodiesel production, but due to increased competition with relatively cheap imports, growth in the region continued to slow, (4) advanced biofuels industry continued to grow with the participation of a wide diversity of players. The "Renewables 2011" report also features a "Renewables Interactive Map" (URL below) which can be used as "a research tool for tracking the development of renewable energy worldwide". The full report can be downloaded at the REN21 website (URL above).
Related information: REN 21 renewables Interactive Map (tracks global developments in renewable energy) http://www.ren21.net/REN21Activities/InteractiveTools/RenewablesMap/tabid/5444/Default.aspx
The United States Department of Agriculture (USDA) investigated the opportunities for growth in the biofuel industry in the United States of America. This study was an update from their 2005 study with added in-depth production and cost analyses and sustainability studies. In their report, the researchers identified the biomass resources which could be used to produce clean, renewable bioenergy as three types: (1) Forest Biomass and Wood Waste Resources; (2) Agricultural Biomass and Waste Resources; and (3) Biomass Energy Crops.
For each biomass resource, comprehensive country-level data and analysis based on rigorous models are presented in order to provide an insight on the biofuel growth potential in the USA. Among the highlights of their report are: (1) the feedstock resources identified could produce about 85 billion gallons of biofuels, which are sufficient to replace approximately 30 per cent of the nation's current petroleum consumption; (2) increases in biomass-derived energy sources can be produced in a sustainable manner through the use of widely-accepted conservation practices,such as no-till farming and crop rotation; and (3) biomass resources could be increased from a current 473 million dry tons annually to nearly 1.1 billion dry tons by 2030, under a conservative set of assumptions about future increases in crop yield.
With their report, the researchers aim to help the public and private sector grow the bioenergy industry and help achieve the goals of dramatically expanding renewable energy resources and developing alternative fuels for America's transportation sector. The full report is available online (URL above).