News and Trends
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Scientists from the Center for Agricultural and Rural Development, Iowa State University (United States) and INRA, UMR Economie Publique INRA-AgroParisTech (France) examine the factors which could determine "whether the necessary private investment will be available to allow a cellulosic biofuels industry to emerge." The results are published in the journal, Energy Policy (URL above).
Presently, cellulosic-ethanol research activities are looking for breakthroughs which could lower production cost, so that private sector investments can be induced to flow. Research areas include conversion technologies, feedstock logistics and feedstock agronomy. The authors mention that previous studies on the future of cellulosic biofuels mostly focus on feedstock supply and associated greenhouse gas emission issues. They say that the "necessary market conditions suitable for the emergence or the absence of second-generation biofuels were overlooked", hence the motivation for their study.
The paper discusses the market forces influencing US and EU future demand for cellulose ethanol, and the role of competition with conventional biofuel options and petroleum-derived fuels. They were able to demonstrate that market forces alone would not be able to induce private sector investment in cellulosic biofuels, because of "a high degree of competition and uncertainty caused by uncertain technologies and commodity prices." They also showed that "emergence of a cellulosic ethanol industry is unlikely without costly government subsidies, in part, because of strong competition from conventional ethanol and limits on ethanol blending."
Other results of the study can be obtained from the journal article at the Energy Policy journal website (URL above).
(full access to journal article may require subscription or payment) http://www.springerlink.com/content/1778925563137661/
The concept of "Polydispersity of Biomass Recalcitrance" (PPBR) has been introduced by an international team of scientists, as a parameter for assessing "processability" of lignocellulosic bioenergy crops into sugars for biofuel-ethanol production.
The main carbohydrate fractions of lignocellulosic biofuel feedstocks (cellulose and hemicellulose) are usually broken down (i.e. "pretreated/saccharified") into their component sugars (glucose and xylose), which are subsequently fermented to ethanol. Determination of the optimum conditions for the cellulose/hemicellulose conversion into sugars is usually done using the total sugar yield (i.e., the sum of glucose and xylose liberated) as the response variable. Thus, only one optimum condition is obtained for both cellulose and hemicellulose conversions.
However, the international scientific team (from the University of Wisconsin, The University of Florida, the Forest Products Laboratory of United States Department of Agriculture, and the South China University of Technology) believes that cellulose and hemicelluloses exhibit different responses to pretreatment, and must be optimized individually. Hemicelluloses require less harsher conditions for conversion into sugars, and easily degrade under more extreme conditions. Celluloses on the other hand are more difficult to break down, and require harsher conditions.
This difference in the "pretreatment/saccharification" response of cellulose and hemicelluloses can be considered as biomass property and has been given the term, "Polydispersity of Plant Biomass Recalcitrance" (or PPBR) by the researchers. In their study, they (1) explored ways to quantify the PPBR, and (2) evaluate the effects of PPBR on pretreatment optimization. The researchers were able to show that PPBR can be a useful predictor of the suitability of an energy crop for biochemical conversion to sugars.
The full results are published in the journal, Bioenergy Research (URL above).
Process monitoring and analysis of lignocellulosic-biomass conversion to biofuels often require long, costly and "destructive" procedures of biomass compositional analysis. The compositional analysis (which includes cellulose, hemicelluloses and lignin fractions) are often used (1) to estimate the ethanol yields of the biomass, or (2) to assess effectiveness of biomass conversion processes.
Researchers from the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) report the use of "Near-Infrared Reflectance Spectroscopy" (NIRS), as an inexpensive, less-complex and less-extensive method for analysis of biomass samples for quantitative evaluation of biomass-to-biofuel processes. NIRS is based on the "differential absorbance and reflectance of light at specific wave lengths" when the sample is subjected to near-infared light.
The (absorbance/reflectance) response of the sample to near-infrared light can be correlated (or "calibrated") with the properties of the biomass, including carbohydrate/lignin content or potential ethanol yield. In the study, the researchers developed NIRS calibration curves "for switchgrass biomass, that can be used to estimate over 20 components including cell wall and soluble sugars and also ethanol production as measured using a laboratory conversion and fermentation procedure".
Using NIRS-derived data for the biomass, they were able to demonstrate that switchgrass cultivars and experimental strains "differed significantly", in terms of biomass composition, and ethanol yields. The researchers also mentioned that "conventional analyses costs for this study would have exceeded $100,000 but with NIRS the costs of the analyses were approximately $3000 or about $10 per sample." The results of the study are published in the journal, Bioenergy Research (URL above).
Related information on Near Infra-Red Spectrospectroscopy (NIRS)
Energy Crops and Feedstocks for Biofuels Production
Australia is one of many countries aiming for a sustainable biodiesel industry, with a target production of 350 ML (million liters) by 2010. However data from the Australian Bureau of Agricultural and Resource Economics show that the 2005/2006 production of biodiesel was only 57 ML, or only one-fifth of the 2010 production target.
In an effort to boost production, the potential of harnessing marginal agricultural regions in Australia (estimated at 20 million hectares to 30 million hectares), for the cultivation of two "exotic biodiesel crops" was proposed. These are: (1) perennial pongam (Pongamia pinnata) and (2) annual Indian mustard (Brassica juncea). Researchers from the Faculty of Agriculture, Food and Natural Resources at the University of Sydney (Australia) explored the potential suitability (and economic viability) of cultivating these crops in marginal land areas under different climate change scenarios. The effect of climate change over time was considered a factor in assessing potential suitability, because data from 1950 to 2003 show that the average temperature in Australia has risen by 0.9 degrees Celsius.
Some highlights of the study are: (1) "total area suitable for growing pongam between 2040 and 2070 is substantially different from the suitable area under current climate", (2) there is greater variation in suitability projections for Indian mustard, but cropping options are flexible, and economic viability may depend on the crop's ability to receive renewable energy certificates and certified emission reductions, (3) "opportunities exist for sustainable pongam agroforestry to supply biodiesel to regional towns, cattle stations and mines in northern Australia". The full paper is published in the journal, Bioenergy Reseasrch (URL above).
Related information on pongam and Indian mustard:
(full access to journal article may require subscription or payment) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V24-51TYF04-
Scientists from the Audubon Sugar Institute, Louisiana State University Agricultural Center (United States) report the "first ever" study on the use of "energy cane" bagasse as feedstock for cellulose-ethanol production. "Energy-cane" is said to have a higher fiber content compared to "regular" sugarcane. Many studies on the use of "regular" sugarcane bagasse as bioethanol feedstock are abundant in literature, but there is no reported study yet on the utilization of "energy cane" bagasse for ethanol production.
The processing technology includes pretreatment of the bagasse by dilute ammonia to remove the lignin, followed by enzymatic hydrolysis to convert plant celluloses/hemicelluloses to component sugars, and ethanol fermentation of the sugars.
Results showed that ammonium hydroxide pretreatment (using a 28% v/v solution, at 160 degrees Celsius and 0.9 MPa to 1.1 MPa pressure) resulted in a delignification efficiency of 55%, a cellulose loss of less than 10%, a cellulose digestibility of 87%, and a glucose yield of about 37 ± 2.3 g glucose per 100 g dry biomass. Ethanol fermentation of the liberated sugars by Saccharomyces cerevisiae resulted in the attainment of 78% of the theoretical ethanol yield, (23 ± 1 g of ethanol per100 g of dry biomass). The full results are published in the journal, Bioresource Technology (URL above).
Related information on Energy Cane:
In the production of the cellulose-ethanol, "cell wall degrading enzymes" (CWDE) are usually used to break down the carbohydrate components of plant cell walls. The bulk of CWDE's are usually cellulose and xylan degraders, called cellulases and xylanases, respectively. The main target of this enzymatic step is the production of ethanol-fermenable sugars.
For many years, most of the cellulases have been sourced from fungi belonging to Trichoderma sp. In order to find potentially new and more effective CWDE's for cellulose-ethanol production, "enzyme prospecting" activities are being initiated by research institutions. Scientists from Cornell University and the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) report the CWDE potential of some plant-pathogenic and non-plant pathogenic fungi.
They found many interesting results, among which are: (1) several plant pathogens were found to have an "abundance of CWDE's" compared to Trichoderma reesei, based on genomic analysis, (2) plant pathogenic fungi were found to have higher hydrolytic activity compared to non-plant-pathogenic fungi (in majority of the test substrates), (3) "among the pathogenic fungi, greater hydrolysis was seen when they were tested on biomass and hemicelluloses derived from their host plants (commelinoid monocot or dicot)", (4) natural isolates of the test fungi had a greater activity on xylan compared to T. reesei, but T. reesei had a higher activity on cellulose. The results showed the potential of plant pathogenic fungi for producing "tailored' CWDE's for cellulose-ethanol production.
The complete paper is published in the open-access journal, Biotechnology for Biofuels (URL above).
Biofuels Policy and Economics
(full access to journal article may require subscription or payment) http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2W-51J7CMD-
An international team of researchers (from the University of North Carolina at Chapel Hill (United States), the King Monkut's University of Technology (Thailand) and the Center for Energy Technology and Environment of the Thailand Ministry of Education) conducted an economic analysis "to contextualize and monetize the various effects" of attaining biofuel policy targets in Thailand. The "net cost" of the Thailand biofuels program was an objective.
Adoption of national policies for the development and use of biofuels in many countries usually take the form of "government incentive structures" (such as mandatory blending or tax exemptions/subsidies). There are both positive ("benefits") and negative ("cost") factors involved when implementing biofuel development programs. The positive factors include job creation, income generation, stabilization of crop prices to farmers, and reduction in greenhouse gas (GHG) emissions. The negative factors include increased emissions of volative organic compounds which could adversely affect public health, adverse land-use changes in pursuit of higher feedstock demands, and biodiversity loss.
Many of these factors are important for policy/decision making, and are usually not included in many economic computations. The researchers attempted to "contextualize and monetize" many of these factors in their study. Some of their findings include the following: (1) domestic biofuel production in Thailand (valued at about 317 million US dollars) is calculated to be more expensive than importing the equivalent amount of petroleum fuel; however, ‘domestic production allows virtually all of the money to stay within the Thai economy, as opposed to being sent abroad, (2) "significant uncertainty in future petroleum prices could strongly influence the direction of Thai policy with respect to biofuels".
The complete paper is published in the journal, Energy Policy (URL above).