Dimethyl Ether is Becoming a Viable Diesel Fuel Alternative in Europe and Asia

In the future, there should be a need for more efficient heavy duty vehicles used for mass transit and transporting goods across a country. In addition these vehicles should be able to perform better (ie increased gas mileage and lowered emissions). One fuel that has been tested since 1995 in diesel type vehicles is Dimethyl Ether, which has been proven to meet fuel emissions standards and perhaps fuel efficiency ones as well. DME (dimethyl ether) can operate in diesel engines with minor modifications to the fuel injection system. Just as interesting, DME can also be mixed with LPG (Liquefied Petroleum Gas) to operate in ignition combustion engines (ie gasoline based). DME can be mixed at 30 % as an additive to LPG and engine modifications might also be needed such as new engine designs that incorporate spark and compression ignition (called Homogeneous Charge Compression Ignition Engine - HCCI [ 1. K. Yeom et al 2009 ]. The chemical structure of DME is shown in the image above. DME has favorable engine performance characteristcs because of its chemical/physical properties such as a low boiling point & high cetane number. DME also combusts very clean or in other words it is Sootles, meaning little to no smoke or particulates are emitted. DME also has projected lower combustion emissions of carbon dioxide, since it has a high oxygen content, it also more easily meets 2007 nitric oxide diesel engine standards due to more exhaust recirculation [ 2. L. Savadkouhi et al year ]. Another interesting fact is that DME can be produced at affordable prices using synthesis gas obtained from natural gas. According to the International DME Association, DME maybe at least 1.5 times cheaper to produce than diesel fuel and can also be simulataneously produced with methanol or converted directly from methanol.

The need to have a fuel distribution network and a good heavy duty vehicle infrastructure based on DME in Europe created a joint effort collaboration called the AFFORHD Project. In fact, there should also be heavy demands for DME trucks and buses in Japan and China. This has prompted companies like Nissan and Volvo to built diesel vehicles that can operate on DME. Nissan based trucks have already been built and have been tested by the National Traffic Safety and Environmental Laboratory where they passed US 2010 heavy duty vehicle emission standards. Increased pressure to have cleaner burning vehicles across the world has already got Europe and Asia pivoted to mass produce DME vehicles between the years 2015 - 2020. Dimethyl ether also has other similar uses to the petrochemical industry where it can serve as a energy production fuel or used as a chemical feedstock for making plastics. DME can be combusted in Gas Turbines for Electric Power Generation. It can be used as chemical feedstock to produce Polypropylene plastics. DME can also be mixed with LPG in order to be used a heating fuel in homes. It is usually mixed at about 20 % with LPG. Other physical properties that make DME a favorable fuel for multiple uses is its low viscosity, high cetane number and low octane number. Overall, DME can serve as a legitimate diesel fuel substitute with the advantage of having better fuel characteristics, performance and lower emissions. Vehicles such as these on the American Highways would be favorable since they may more easily pass more recent American fuel efficiency and emission standards as mentioned above.

REFERENCES

1. "Knock Characteristics in Liquefied Petroleum Gas (LPG) - Dimethyl Ether (DME) Homogeneous Charge Compression Ignition Engine", Energy Fuels vol 23 no 4 pgs 1956-1964 [2009] by K. Yeom and C. Bae

2. "Performance and Combustion Characteristics of OM314 Diesel Engine Fueled with DME : A Theoretical and Experimental Analysis" Journal of Engineering for Gas Turbines and Power vol 132 no 9 pgs 92801-92806 by L. Savadkouhi, S.A. Jazayeni, N. Shahangian, J. Tavakoli

Photos taken from the Picassa Web Album

KEYWORDS: Dimethyl Ether, Diesel Fuel Substitutes, Nitric Oxide Emission Standards, Liquefied Petroleum Gas, Simultaneous Methanol and Dimethyl Ether Production, Cetane Number, Viscosity, Homogeneous Charge Compression Ignition Engine, Gas Turbine Fuel, Home Heating Fuel, National Traffic Safety and Environmental Laboratory, AFFORHD, Nissan & Volvo DME trucks, Sootless emissions, low carbon dioxide emission fuels

Yeast Cultivation can also Produce Biodiesel from Renewable Waste Resources

The production of biodiesel from algae and microorganisms is a viable alternative to the usual methods of production which include crushed oilseeds and waste vegetable oil (WVO). Most people already know about the use of algae that is currently being developed for a number of different types of biofuels, another possible source of fatty acids for biodiesel that hasn't received much attention can be cultivated using microorganisms or yeast cells. Microorganisms or algae could be the favorable choice in biofuel production due to the theoretical high yield amount of biomass per acre as compared to conventional energy crops which usually include oilseeds such as soybeans. It is estimated that alternative biomass sources such as algae produce 30 times more energy value than these conventional crops. Several yeast cell varieties that have been experimented in with in the past can produce high fatty acids amounts per cell and along with high lipid yeilds. Three types of yeast varieties, those being Cryptococcus Curvatus, Lipomyces Starkeyi & Rhodotorula Glutinis can attain a cell lipid percentage of up to 60 - 70 % [ 1. X. Meng et al 2009 ]. An advantage with the cultivation of yeast cells for biofuels is that they can be grown using dark fermentation. Dark Fermentation is a term that usually applies mostly towards the production of biohydrogen from microrganisms. However, similar fermentation conditions and even carbon feedstocks work for the cultivation of yeasts even though they are not the same choice of microorganisms that usually make hydrogen. However, the same type renewable waste resources used for biohydrogen production can also be applied towards the cultivation of yeast cells towards lipid production. These type of renewable waste sources include wastewater sources, dairy wastes, starch hydrosylates, lignocellulosic wastes and even biodiesel glycerine waste.

Yeast cells also have the advantage of attaining high biomass yields in a short period of time. The growth rate of yeast as well as the actual conversion rate of a carbon source into lipids are very good. For example, with batch style fermentation, yeasts attain cell density yields of around 100 - 150 grams cells per liter, while lipid production rates are around 0.2 - 0.5 grams lipid per liter * hour and a carbon conversion rate of up to 30 % [ 2. P. Measters et al 1996 ]. High lipid yields can be attained by providing an excess amount of carbon feedstock as well as providing a lower nitrogen content in the growth media. In other words having a high carbon to nitrogen (C/N ratio) - (a similar concept in producing a good compost) and other factors such as favorable Temperature, pH and oxygen content provide higher lipid yields [ 3. L. Azocar et al 2010 ]. Companies are already using yeasts to produce biofuels although not towards the manufacture of lipids. One company currently cultivates yeast cells to make isoprenes. Isoprenes represent a large class of natural compounds produced by many organisms, of which plants usually produce a large subset of these compounds called terpenoids. Isoprene, which is a related compound can also be produced by microorganisms. It is used to make materials like rubber. The cost of producing biofuels from microorganisms or algae have some obstacles to overcome, such as processing and refining methods, costs and associated technology improvement needs. Production of biofuels from algae, microorganisms or yeasts may still be a favorable method of choice due to the possible availability of renewable waste resources as carbon sources to produce lipids. The production of biodiesel itself has the potential to manufacture even more biodiesel from the cultivation of yeast cells from the glycerine waste that may accumulate in large quantities as more biodiesel is produced. For example, it is estimated that for every 10 kg of biodiesel produced from certain oilseeds around 1 kg of waste glycerine is made. It is also estimated that even at the current production rate, the pharmaceutical industry only needs 1/3 of the glycerine produced to help manufacture drugs.

REFERENCES

1. "Biodiesel Production from Oleaginous Microorganisms", Renewable Energy vol 34 pg 1-5 [2009] by Xin Meng, J. Yang, Xin Xu, L. Zhang, Q. Nic, M. Xien

2. "High Density Cultivation of the Lipid Accumulating Yeast Cryptococcus Curvatus using Glycerol as a Carbon Source", Applied Microbiology & Biotechnology vol 45 pgs 575-579 [1996] by PAEP Measters, GNM Huijbents

2. "Biotechnological Processes for Biodiesel Production Using Alternative Oils", Applied Microbiology & Biotechnology vol 88 No 3 pg 621-626 by L. Azocar, G. Ciudad, HJ Heipieper, R. Navia

Photos taken from the Picasa Web Album

KEYWORDS: Cryptococcus Curvatus, Lipomyces Starkeyi, Dark Fermentation, Renewable Waste Resources, Biodiesel Glycerine, Isoprenes, High Production Biomass, Yeast based Biodiesel, High Lipid Percentage per cell, Rhodotorula Glutinis, Starch & Whey Hydrosylates

Photos taken from the Web Album of Picasa

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