Transforming a Demanding Goal into an Attainable Destiny: Use of Miscanthus as A Raw Material for Biomass

The United State’s Department of Energy and Department of Agriculture have recently focused their efforts on increasing biofuel production from biomass (Dohleman et al. 2009). The Departments’ goal to increase biomass production (and consequent biofuel production) will be more successful if an investigation first determines the most efficient raw material for the manufacturing of biomass. C4 grasses such as Miscanthus x giganteus (Miscanthus) and Panicum virgatum  (switchgrass) have particularly been targeted for their low anthropogenic inputs, higher net energy gains, and lower greenhouse gas emissions. The low anthropogenic inputs are partly attributable to the species’ symbiotic relationship with bacteria capable of nitrogen fixation, which diminish needs for nitrogen fertilizer, decreasing fossil fuel usage. Previous studies comparing Miscanthus and switchgrass have found that Miscanthus is more than two times as productive as switchgrass. — Alec Faggen 
Dohleman, F., Heaton, E., Leakey, A., Long, S., 2009. Does greater leaf-level photosynthesis explain the larger solar energy conversion efficiency of Miscanthus relative to switchgrass? Plant, Cell and Environment 32, 15251537

Dohleman and colleagues working at the University of Illinois and Iowa State University researched the hypothesis that this disparity in production can be attributed to Miscanthus’s higher leaf photosynthetic rates compared to switchgrass. The authors specifically investigated (1) leaf photosynthetic carbon dioxide (CO2) uptake under varying growing conditions; (2) the effectiveness of the plants’ water and nitrogen usage; and (3) energy loss during photosynthesis. This multi-phase study took place in central Illinois over 20 different days during 2005 and 2006, resulting in over 3300 recordings. The authors found that Miscanthus has a 33% higher leaf photosynthetic rate. In order to achieve this higher photosynthetic rate, Miscanthus must absorb higher levels of CO2 by opening its stomata more frequently and/or for longer durations of time. This increase in stomatal conduction, unfortunately, costs the Miscanthus a 25% loss of water.
The study explained the species’ higher leaf photosynthetic rate using various tests. The authors measured a 23% increase in whole-chain electron transport rate in Miscanthus compared to switchgrass. During transduction into whole chain electron transport, the authors found that light energy loss was significantly lower in Miscanthus. They also observed that leaf nitrogen and water use were significantly higher in Miscanthus. These findings all yield additional understanding as to the species’ higher photosynthetic rate.
These results, however, do not fully explain the higher productivity of Miscanthus. Other factors such as smaller root partitioning, decreased respiration, more extensive leaf canopy, and/or higher leaf area index must also contribute. Increased understanding as to the factors behind the greater productivity of Miscanthus will elucidate appropriate selection criterion for more successful biomass production. 

Revolutionizing Methane Production and Carbon Capture via Algal Biomass

Biomass production from food sources has been shown to increase greenhouse gas emissions and other pollutants through necessary land use changes (Stucki et al. 2009). In order to provide a sustainable source of biofuel in the future, biomass production must be enacted that does not substantiate the climate problems or compete with food production. Microalgae have recently been targeted as great potential sources for biofuel. The two main problems for this type of production are an efficient means to grow the algae and an efficient means to convert the algae into useful energy. One potential clean energy source is methane. New technologies are currently being explored to make methane production from algae more efficient. — Alec Faggen    
Stucki, S., Vogel, F., Ludwig, C., Haiduc, A., Brandenberger, M., 2009. Catalytic gasification of algae in supercritical water for biofuel production and carbon capture. Energy Environmental Science 2, 535541.

 Stucki and colleagues working at the Laboratory for Energy and Materials Cycles in Switzerland have revolutionized biofuel production via algal biomass. The authors employ a two-phase process in which they first grow the algae in a photobioreactor and later convert it into methane. The methane produced is pipeline quality synthetic natural gas.
The authors’ first process ameliorates the issue of climate change by using carbon dioxide emissions  for algae cultivation. The subsequent process converts this algae into biofuel via a catalytic hydrothermal gasification process in supercritical water. The hydrothermal process also succeeds in recycling the algal organic matter back into nutrients for algae growth. These processes are experimentally designed to be sustainable whereby all heat demands are satisfied by heat recovery or by combustion of some of the methane gas product.
This methodology successfully lessens fossil fuel dependence, without disturbing food production. It is especially useful because the yields do not depend on algal products such as lipids. A challenge to the procedure and area for future study is the protection of the catalyst from the toxic effects of the heteroatoms, which are present in the algal biomass. 

Engineering the Perfect Combination: Methyl Halide Production from Renewable Carbon Sources in Engineered Yeast

An attractive method to satisfy the growing demand for fuel is the conversion of non-food agricultural resources into liquid fuels (Bayer et al. 2009). Specifically, methyl halides are useful reactants for gasoline production via a catalyst called Zeolite. Methyl halides show promise as a petroleum substitute because the compounds can be derived from renewable carbon sources. However, the feasibility of producing methyl halides remains a problem. Methyl halides are naturally produced from many organisms, including marine algae, fungi and halophytic plants, but it is time-consuming to harvest them and the yields are low. The enzyme responsible for this process is methyl halide transferase (MHT). Current research is exploring ways to transport MHTs into more industrially sound organisms for faster, more effective methyl halide production. Researchers are now employing a special technique called “synthetic metagenomics” to construct genetic sequences from DNA libraries based on functional similarities. The identified genetic sequences are then cloned into a vector for replication by Escherichia coli (E. coli) or yeast.Alec Faggen 
Bayer, T., Widmaier, D., Temme, K., Mirsky, E., Santi, D., Voigt, C., 2009. Synthesis of Methyl Halides from Biomass Using Engineered Microbes. Journal of The American Chemical Society 131, 65088615.

 Bayer and colleagues working at the University of San Francisco combined naturally producing MHT yeast and cellulolytic bacteria in order to effectively convert lignocellulosic biomass (such as switchgrass, poplar, corn stover, and sugar cane bagasse) to methyl halides. Eighty-nine MHT genes were initially selected after multiple BLAST searches on all putative MHT genes from the NCBI sequence database. These genes came from diverse sources of plants, fungi, bacteria, and unidentified organisms. New chemical synthesis techniques obviated the need for host organisms for cloning, which is especially beneficial because some of these genes are from unknown organisms.
Methyl halide production, using the synthesized MHT genes, was then tested on three ions in E. coli. The MHT from the halophytic plant, B. maritime, presented with the highest activity of all genes on each ion. The B. maritime MHT was then transferred to the yeast S. cerevisiae. Yeast is especially useful as a host organism for its natural resistance to the toxic effects of methyl halides up to high levels. Its productivity from glucose was found to be 12,000 times better than the best production rate from a culturable organism. A co-culture using this newly engineered yeast and the cellulolytic bacterium Actinotalea fermentans attained successful methyl halide production from unprocessed switchgrass (Panicum virgatum), corn stover, sugar cane bagasse, and poplar (Populus sp.). These results demonstrate the potential of producing methyl halides from non-food agricultural resources.

Gas Stations of the Future: Biodiesel Production from Used Cooking Oil on a College Campus

Biodiesel production has the potential to both reduce foreign dependence and environmental damage (Agnew et al. 2007). It is non-toxic, biodegradable, and has lower emissions of carbon monoxide, particulate matter, and unburned hydrocarbons as compared to petroleum-based fuels. It also has health benefits because biodiesel has no sulfur or carcinogenic components. Despite the environmental and health-related advantages, biodiesel from fresh oil is not economical in the short-term. Raw materials alone account for approximately 7095% of total manufacturing costs. Thus, studies are being conducted to evaluate the feasibility of converting used cooking oil into biodiesel.— Alec Faggen 
Agnew, R., Ming, C., Lu, M., 2009. Making Biodiesel from Recycled Cooking Oil Generatd in Campus Dining Facilities. Mary Ann Liebert, Inc 2, 303307.

 Agnew and colleagues working in the Department of Civil and Environmental Engineering of the University of Cincinatti participated in one such study using a transesterification methodology to convert methanol and fryer oil from campus dining halls into biodiesel (or methyl esters) and glycerol. They began by using an acid-base titration in order to determine the amount of catalyst (sodium hydroxide) needed for their oil supply and discovered a higher content of free fatty acids compared to the majority of waste oils described in the literature, a result of the hydrolysis of triglycerides during heating.  Later, they varied the catalyst in small-scale pilot tests to determine optimal catalyst usage for each batch of recycled oil. Recycled oil requires more catalyst and higher gelling temperatures than fresh oil because frying produces free fatty acids. Filtration is also necessary to remove any remaining food debris. The catalyst (NaOH) is dissolved into the methanol and mixed for over an hour with heated cooking oil. After settling for eight hours, the glycerin’s higher density separates it from the biodiesel, so the glycerin is drained from the bottom of the reactor. After multiple washings with water to remove the catalyst and a final filtration using hairnets, the biodiesel is ready for use in a diesel engine.
Since the start of the project in 2007, the University of Cincinnati has produced hundreds of gallons of biodiesel. The fuel has been successfully tested in a Jeep’s diesel engine, and it is in the process of being used by both delivery fleets and shuttle services.  The university has also signed an agreement to use 2% biodiesel in its utility plant plants, providing an example to both its own community and other universities by demonstrating the viability of a more environmental and economical means for energy production. 

The Total Picture: The Benefits of a Switchgrass Biorefinery System after Analysis using the Life Cycle Assessment

Switchgrass (Panicum virgatum) is a type of prairie grass that has been proposed as a valuable crop for bioenergy, bioethanol, and biochemical (phenol) manufacturing (Cherubini and Jungmeier, 2009). The grass’s attractiveness arises from its minimal nutrient intake, its high overall energy production, its habitat diversity, and its ability to sequester carbon. Biomass energy has been considered most efficient while using a biorefinery approach in which multiple technological approaches are used conjointly.— Alec Faggen
Cherubini, F., Jungmeier, G., 2009. LCA of a biorefinery concept producing bioethanol, bioenergy, and chemicals from switchgrass. The International Journal of Life Cycle Assessment 15, 5366.

Cherubini and Jungmeier working at the Norwegian University of Science and Technology and at the Institute of Energy Research used a Life Cycle Assessment (LCA) methodology to compare a biorefinery system to a fossil reference system. The biorefinery approach used switchgrass to produce bioethanol (instead of gasoline), heat from biomethane (instead of natural gas), electricity, heat, and phenols. The LCA calculates the total magnitude of contributions from all inputs and outputs throughout production. The authors were especially focused on green house gas (GHG) emissions and fossil energy usage because high demands for sustainable energy and climate change mitigation are the primary dictators of biorefinery progression.
     The biorefinery technique of switchgrass decreased GHG emissions by 79% and saved about 80% of non-renewable energy. The energy output of the system is 3.6 times the non-renewable energy input. During the first 20 years, the soil sequesters a large amount of atmospheric carbon before it reaches a new equilibrium. These years contribute heavily to the decrease in GHG emissions for both carbon dioxide and methane. After these first years, the GHG emissions were produced mainly from switchgrass pellet production (85%). The biorefinery system also decreased all other investigated environmental impacts during the first 20 years, except for the impacts in the areas of acidification and eutrophication which increased.
Nitrous oxide (N2O) has a 298 times greater global warming potential than carbon dioxide, making N2O an important variable to study in terms of nitrogen fertilizer use and organic matter decomposition in soil. Although the biorefinery system released more N2O into the atmosphere, the emissions varied considerably depending on variables such as soil type, climate, and tillage methods. 

When Life Gives You Lemons: How Waste from Biofuel Production can be Converted into a Possible Energy Source

As biodiesel manufacturing continues to skyrocket, glycerol, previously a sought-after by-product has become an increasingly threatening waste crisis (Sabourin-Provost and Hallenbeck, 2009). The most commercially used process in biodiesel production is the base-catalyzed trans-esterification of oil, which produces about 10 kg of glycerol per 100 kg of biodiesel. As demands for biodiesel multiply in order to reduce petroleum dependence and greenhouse gas emissions, the development of a feasible method to convert glycerol into a usable resource becomes increasingly critical. Fuel is one of the only viable resources that fulfills this long-term demand. Therefore, conversion of glycerol into either ethanol or hydrogen has been deemed the most apt solution. Ethanol production from crude glycerol has been met with many setbacks such as low yields and impracticality. Thus, current research looks to hydrogen, which is currently being investigated as a future fuel, to resolve the glycerol crisis.—Alec Faggen

Sabourin-Provost, G., Hallenbeck, P., 2009. High yield conversion of a crude glycerol fraction from biodiesel production to hydrogen by photofermentation. Bioresource Technology 100, 35133517.

 Sabourin-Provost and Hallenbeck working in the Department of Microbiology and Immunology at the University of Montreal found that the purple non-sulfur photosynthetic bacterium, Rhodopseudomonas palustris, photoferments glycerol to hydrogen via an active nitrogenase. The authors of the paper were able to collect 6 moles of hydrogen gas/mole of glycerol, (almost 75% of theoretical calculations). Although not required for synthesis, the addition of a nitrogen source maximized hydrogen formation. Crude glycerol and pure glycerol had about the same yields of hydrogen production.
A number of benefits to hydrogen manufacturing exist. Hydrogen is a water insoluble product; thus, it is relatively easy to collect in comparison to water-soluble products such as ethanol. Furthermore, necessary dilutions, in order to counter possible contaminant complications, are not as consequential if producing a gaseous product like hydrogen.
     Nonetheless, many obstacles subsist before hydrogen synthesis from glycerol can be efficient. An economic photobioreactor where the reactions can take place is yet to be constructed. The photobioreactor must be transparent so light can catalyze the reactions and also hydrogen-impermeable so the hydrogen gas can ultimately be collected. In addition, R. palustris is inefficient at utilizing light, and future research should investigate optimal light intensity for these organisms. 

Irradiating the Future of Biofuel: Using Electron Beam Irradiation Pretreatment to Improve Cellulosic Biofuel Production

Cellulose’s abundance makes it an obvious choice as a raw material for biofuel production (Bak et al. 2009). Specifically, enzymatic hydrolysis of lignocellulose, which is composed of cellulose, hemicelluloses, and lignin, has been studied to satisfy the demanding ambitions to reduce gasoline usage from groups like the United State’s Department of Energy. Unfortunately, complications arise during cellulosic biofuel manufacturing because the cellulose in lignocellulose is not normally accessible to hydrolytic enzymes. Many physical and chemical pretreatments have been suggested to improve access to the cellulose in order to produce higher glucose yields. The majority of the proposed chemical processes generate byproducts that inhibit enzymatic hydrolysis of the cellulose, establishing a need for costly, resistant enzymes. Many physical pretreatments, such as the milling process, have been deemed inefficient and energetically costly. Instead, electron beam irradiation (EBI) of lignocelluloses was proposed for its low yields of harmful byproducts and for its functionality in the absence of extreme temperatures. —Alec Faggen
Bak, J., Ko, J., Han, Y., Lee, B., Choi, I., Kim, K., 2009. Improved enzymatic hydrolysis yield of rice straw using electron beam irradiation pretreatment. Bioresource Technology 100, 12851290.

      Bak and colleagues working at the Korea University and Korea Atomic Energy Research Institute evaluated the efficacy of EBI to improve enzymatic hydrolysis of cellulose for biofuel production.  The authors of the paper pretreated a type of lignocellulose called rice straw with EBI and determined its subsequent enzymatic digestibility and physical composition. Multiple trials were performed using varying crystallinity indexes of cellulose, EBI currents, and EBI dosage to determine optimal levels for pretreatment. The authors also varied the concentration of hydrolytic enzymes, resolving that no concentration of enzymes could effectively hydrolyze the lignocellulose without proper pretreatment. Scanning electron microscopy and X-ray diffraction verified that the EBI was causing the physical changes in the rice straw. 
Compared to the control samples of untreated rice straw, EBI-treated rice straw increased glucose yields from 5.1% to 43.1% after hydrolysis for 24 hours, and from 22.6% to 52.1% after hydrolysis for 132 hours.  However, these yields were lower than other physical and chemical pretreatment methods such as dilute-acid, ammonia fiber explosion, and soaking in aqueous ammonia, documented in previous literature. 

Microalgae: potentially the most efficient raw material for biofuel production

Alternatives to fossil fuels such as biofuels have shown promise in not only reducing harmful gaseous emissions, but in facilitating the return of the Earth’s atmosphere to equilibrium (Gouveia and Cristina, 2009). Although oleaginous crops are normally used to produce biofuels, recent research has concluded that microalgae can be 1020 times more efficient than oleaginous seeds or vegetable oils. In addition, microalgae fix carbon dioxide and thus help to decrease greenhouse gases in the atmosphere. After oil is extracted from the algae, the remaining product can be further processed to create fertilizer, feed, biogas, or high value chemical compounds.— Alec Faggen
 Gouveia, L., Oliveira, A., 2009. Microalgae as a raw material for biofuels production. Journal of Industrial Microbiology & Biotechnology 36, 269-274.

Gouveia and Cristina at the Instituto Nacional de Engenharia compared six species of microalgae to determine the algae with the fastest growth rate and highest oil content with adequate composition. Nannochloropsis sp. and Neochloris oleabundans have high oil contents and under nitrogen depletion, increase oil quantity by about 50%. The oil content is characterized by iodine value. Careful comparisons of these values demonstrate that these microalgae have better quality oil than some vegetable oils. Although neither Nannochloropsis sp. nor Neochloris oleabundans alone can produce biodiesel, when used in conjunction with other microalgal oils and/or vegetable oils, they are viable. Although its oil quantity is smaller, Scenesdesmus obliquus has the best fatty acid profile and is feasible without other algae or oils.
Microalgae are especially promising sources for biofuel due to their fast growth rate, their high photosynthetic efficiency, their high biomass productivities, their ability to be harvested daily, their minimal need for water, and their capacity to grow in infertile land. However, cell lipid content must be monitored during production, which, in addition to being time consuming, produces harmful wastes if not properly distilled. Advances in biorefinery and photobioreactor engineering will help to resolve these limitations. As the biodiesel market speedily expands, microalgae is arguably the only potential source of renewable biodiesel that does not disrupt food production.—Alec Faggen