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News and Trends
Lignin is the tough material component in lignocellulosic biomass which must be removed by pretreatment in order for the biomass to be processed into biofuel-ethanol. Breaking this so-called "lignin barrier" or "biomass recalcitrance" (i.e. "resistance to invasive change") is an important step toward more cost-effective bioethanol production from lignocellulosic biomass. Although many pretreatment methods have been tried in attempt to remove lignin from plant biomass, these have been tried on a partly empirical basis, because the chemical structure of lignin is not yet completely understood. Understanding these chemical mysteries of the lignin molecule can open new developments for more effective pretreatment methods of delignification. A recent study by researchers from the Department of Energy's Oak Ridge National Laboratory (ORNL, United States) has provided a closer look into the molecule that complicates the production of next-generation biofuels. In their study, they used a combination of neutron scattering experiments and large-scale simulations using the ORNL's Jaguar supercomputer, which is the first of its kind, to reveal the surface structure of lignin down to one angstrom, or ten billionth of a meter. They found that lignin forms aggregates in vivo and has a highly folded surface. These observations are said to pose a barrier to cellulosic ethanol production. The lignin aggregates and their highly folded surfaces can bind to the (saccharifying) enzymes and reduce the efficiency of the conversion. (Saccharifying enzymes convert the carbohydrate fraction of pretreated biomass into ethanol-fermentable sugars). The surface of the pretreated softwood lignin is characterized by a highly folded surface. The highly folded nature of the lignin molecule is reported to slow down enzymatic activity. The full report of the study are published in the journal, Physical Review E (URL above). . Energy Crops and Feedstocks for Biofuels Production
(complete access to journal article may required payment or subscription) Researchers from the Division of Environmental Science and Engineering, Faculty of Engineering, National University of Singapore, investigated the possible strains of marine microalgae which could be used in biodiesel production. Microalgae have been considered as the more sustainable feedstocks for biodiesel production (compared to terrestrial bioenergy crops) because of their high oil content and rapid biomass production. Marine microalgae are particularly considered to have an advantage over freshwater microalgae as biodiesel feedstocks, because they do not require freshwater during cultivation (i.e. lower "(fresh)water footprint"). In their paper, the researchers presented a screening procedure for the selection of the favorable microalgae cell biodiesel feedstock. First, microalgae cells were sorted using an automated flow cytometric cell sorting technique. The technique is based on the two-dimensional distribution of algal cells for red fluorescence (chlorophyll auto-fluorescence) against forward-light scatter (cell size) and red vs. green fluorescence. Using the technique, the researchers were able to isolate ninety six strains of marine microalgae with favorable characteristics (elevated biomass productivity and intracellular lipid content) from the coastal waters of Singapore. Further characterization for the selection of the best biodiesel feedstock was done with respect to cell growth rate, biomass concentration, lipid (total and neutral lipid) and fatty acid profile. The researchers reported that the Skeletonema costatum, Chaetoceros and Thalassiosira species have the highest growth rate. However, they found that the most promising species for biodiesel production were the Nannochloropsis strains, because these strains had the highest lipid content, ranging from 39.4% to 44.9% of the dry biomass. Biodiesel production from the transesterification of the lipids of the Nannochloropsis strains yielded 25-51% of fatty acid methyl esters (FAME). This translates to 11% to 21% FAME content of dry biomass. The full study is published in the free access journal, Biomass and Bioenergy (URL above). Related information on flow cytometry: http://probes.invitrogen.com/resources/education/tutorials/4Intro_Flow/player.html. Biofuels Processing
Scientists from the Department of Biological Systems Engineering, Washington State University (United States) obtained insights as to how termites might modify the lignin structural assembly in softwood tissues. Lignin is one component of plant biomass which gives the structural integrity to the plant; however, lignin also imparts "biomass recalcitrance" against non-extreme pretreatment methods for biofuel production. By looking at how termites deconstruct and degrade lignin in this type of lignocellulosic biomass, a better understanding of the critical mechanisms for plant cell wall degradation could be obtained. This could lead to better strategies for delignification pretreatment in the biofuel ethanol production process. The scientists compared the lignin structures of raw and termite-digested softwood tissues (in termite feces) using advanced analytical techniques. These techniques include "13C crosspolarization magic angle spinning and nuclear magnetic resonance (CP-MAS-NMR) spectroscopy, flash pyrolysis with gas chromatography mass spectrometry (Py-GC/MS), and Py-GC-MS in the presence of tetramethylammonium hydroxide (Py-TMAH)-GC/MS". The following are some highlights of their study: (1) the levels of one common component in the lignin structure (the "G unit") was found to increase, while at the same time showing evidence of cellulose degradation, The full paper is published in the open-access journal, Biotechnology for Biofuels (URL) above.
(complete access to journal article may required payment or subscription) Researchers from the Department of Chemical Engineering, Institute for Chemical and Environmental Technology (ITQUIMA), University of Castilla – La Mancha (Spain) have explored a new innovation in the production of biodiesel from sunflower oil. In the conventional method, the oils are reacted with methanol, using sodium hydroxide as catalyst. The products are the biodiesel (a mixture of methyl esters) and a by-product called, glycerol. Instead of using the conventional methanol for the chemical process of biodiesel production, the researchers investigated the use of methyl acetate with potassium methoxide as catalyst to produce the biodiesel. Among the findings of their study were: (1) the optimum conditions that created a compromise between the product yield, reaction kinetics and methyl acetate recovery were found to be a methyl acetate-to-oil molar ratio of 50 and a catalyst-to-oil molar ratio of 0.10; The full study is published in the free-access journal, Biomass and Bioenergy (URL above). Biofuels Policy and Economics
(complete access to journal article may required payment or subscription) A recent study by researchers from the School of Chemical Engineering, Engineering Campus, Universiti Sains (Malaysia) analyzed the feasibility of a unified ASEAN biomass-based energy system with the incorporation of the clean development mechanism (CDM). (ASEAN is the Association of Southeast Asian Nations composed of 10 member-countries from Southeast Asia). ASEAN is a region of high economic growth, and consequently, the region has a high energy consumption which is dominantly fuelled by fossil fuels. An alternative energy supply source is necessary to achieve sustainable energy support for the region. The researchers first explored the potential and advantages for an ASEAN investment in the supply, processing and distribution of the biomass-based bioenergy emphasizing on the regional collaborations. Then, they assessed the project if it could be placed under the CDM. The Clean Development Mechanism is one of the "flexibility mechanisms" that is defined in the Kyoto Protocol which allows emission-reduction projects in developing countries to become more attractive by giving it credits which translates to economic value. Finally, they investigated the cross-border implementation and operational challenges in terms of political, economic, technical and sustainability concerns of the energy scheme. The researchers hope that this project could serve as a prime example for regional partnerships in achieving sustainable development for the energy and environmental sector in the future. The full paper is published in the journal, Biomass and Bioenergy (URL above)
(complete access to journal article may required payment or subscription) An international team of scientists from Canada (the Semiarid Prairie Agricultural Research Centre and China (Renmin University of China, Ningxia Municipal Commission of Development and Reform Commission, and the Low Carbon Research Centerna) applied the Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis to diagnose and identify the economic, environmental and social impacts from bioenergy production on marginal land. Marginal lands are considered an attractive option for the cultivation of bioenergy crops. The main advantage is that these lands do not threaten food security since productive lands are used for food production. In their paper, the researchers defined marginal land on the basis of a set of physical criteria (including lands that are bare/herbaceous, with soil problems, and with moderate to steep slopes) plus other factors. With this definition, they identified the strengths, weaknesses, opportunities and threats of bioenergy production on marginal land. The strengths include large land supply potential and strong energy crops adaptability. The weaknesses include possibly low economic viability, uncertainty about environmental impacts, and equity/gender concerns. Security of food supply, and the acquisition of renewable energy supply are seen as opportunities. Among the identified threats are the rise in fuel price, higher labor cost, and natural hazards/crisis. The full paper is published in the journal, Energy Procedia. |
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