Corn Stover Most Abundant Crop Residual that can be used for Vehicle Fuels, Electrical Energy and Chemicals

Corn stover is the residual crop material left over after the harvesting of corn which consists of the other parts of the corn plant which are the stalks, leafs, cobs and husks. Some of these plant residuals are left to lie on the corn fields to help mulch the soil before the next planting period. However, corn stover has been collected after corn harvests in the past and reused to produce other chemicals and products. For example, due to the fiber content of corn stover, some of it was processed as non-wood fiber pulping which can be converted into other products. Even currently, the fiber processed from corn stover is being considered as use in particleboard manufacturing. Under current farming conditions and practices, corn stover is collected or produced at around 100 million tons per year. According to the USDA and DOE, this figure could increase dramatically within the next decade if corn yields are increased and farming technology is improved. The government estimates that at least 170 - 256 million tons of corn stover could be produced every year according to the USDA billion ton study, corn stover would definitely be the largest plant crop residual renewable resource in the United States. There are certain obstacles that make the use of large amounts of corn stover not as realizable. For example, since corn stover can only be collected once per year, it must be transported and stored properly before it can be bioprocessed. One of the challenges involved is ensuring that it is dry. The use of corn stover has now expanded into energy and fuels production as well as the continued production of chemicals. This essay attempts to demonstrate some of the practical uses of corn stover. One method that corn stover can be stored and partially processed into useful chemicals or energy is the ensilage process. Ensilage packs corn stovers into silos and fermentation of the stover then proceeds with the natural microorganisms. Ensilage is a method that is being used to produce hydrogen for a 1.5 kW fuel cell power plant in Germany. The ensilage process allows the corn stover to be converted into biogas through anaerobic fermentation, the biogas is then converted into hydrogen. Ensilage is also a method that could produce adequate amounts of a chemical called lactic acid which can then be further converted into poly lactide plastics or ethyl lactate. This is usually done with regular corn starch which is full of sugars which lactic acid bacteria need to make lactic acid.

The ensilage process could also make large amounts of lactic acid if other enzymes from fungi are seeded with the corn stover. Fungi such as Trichoderma Reesei or Aspergillus Niger could be grown and placed with the stover as it is going through the fermentation process to ensure that sugars from its cellulose and hemicellulose content are hydrolyzed [ 1. Ren et al 2007 ]. PLA based platics are one of the fastest growing biobased plastics on the market made from lactic acid. Another valuable chemical that can be extracted from corn stover are furfurals. These compounds are oftentimes extracted from wood and other materials that have hemicellulose content where the pentose sugars are extracted and converted into furfurals through processes like steam distillation. Furfurals constitute a large subset of plastics that are made partially from natural sources. Furfurals are mixed with a number of other chemicals such as acetone, other ketones, alcohol, phenol and aniline to make furfural based resins [ 2. Brady 1991 ]. Corn stover can also be densified in the future to produce fuel and further power and heat known as combined heat and power (CHP). The University of Minnesota is working with densified corn stover which are in the form of pellets, to show it is a legitimate fuel that can be gasified to produce electricity and heat. Corn stover is also being experimented by the government in large bioethanol refineries that can produce multi million gallons of ethanol per year along with other sources such as switchgrass. Corn stover can also be used to produce butanol, which has been considered as another alcohol based fuel source for vehicles. Butanol can be made through a process known as ABE (Acetone Butanol Ethanol) Fermentation. Other companies may also use corn stover in order to gasify it as a Fischer-Tropsch process to make biobased alternative fuels such as jet fuel. Overall, there are numerous alternative products that corn stover can produce that have not been mentioned, the uses outlined in this essay are not an exhaustive list. It is meant to provide information on how useful corn stover will become in future generations to help produce electricity, heat & power, plastics and vehicle fuels - all areas in which renewable resources such as crop residues can help solve our alternative product and energy needs when replacements for petroleum are needed.

REFERENCES

1. "The impact of enzyme characteristics of corn stover fiber degradation and acid production during ensiled storage", Applied Biochemistry and Biotechnology Vol 137 pgs 221-238 [2007] by H. Ren, K. Moore

2. Materials Handbook 13th Edition [1991] pg. 361 by G. Brady, H. Clauser

Photos taken from one of NREL photo archives

KEYWORDS: corn stover, poly lactic acid, furfurals, ethanol biorefineries, butanol ABE fermentation, ensilage of corn stover, ensilage fermentation of corn stover with fungi, Fischer-Tropsch, Combined Heat and Power with corn stover, fuel cell power with corn stover, USDA billion ton study, crop residues as renewable resources, corn stover use for energy and fuel

Petroleum Coke is a good Resource for Electrical Energy Generation due to its Price, Availability and its Ability to Produce Hydrogen

Petroleum coke is the residual material from the processing of heavy oils at refinery plants. The petroleum coke is a byproduct of the oil cracking process which converts the heavy oils into further fuels or products. However, in addition, sometimes the heavy oils must be pre-processed by other manufacturing stages known as Flexicoking or Delayed Coking unit operations [ 1. Trommer et al 2005 ]. The use of Petroleum Coke used as fuel in electrical power plants has been steadily increasing since 1995 according to the figure shown above [ 2. EIA 2009 ]. In fact, the use of petroleum based liquids such as distillate oils or diesel has declined markedly during this time period also, maybe due to the fact that alternative carbon based power sources are being used instead. The combustion of petroleum liquids causes more pollution, carbon dioxide emissions and particulates than other means of electrical generation such as Gasification. Although petroleum coke does have some metal content as well as a good amount of sulfur content (~ 5 %), but is still good to use due to its in gasification technology along with calcinization that may help to alleviate the high sulfur content. Coal and other carbon sources have been used in cleaner electrical generation from the use of Circulating Fluidized Bed CFB Boilers. Petroleum coke has also been used in mills such as Pulp and Paper as well as Cement and Brick kilns [Same Internet Reference as Above]. In order for Petroleum Coke to be used effectively in CFB units it must be sold in its Pulverized form, like what is required with coal to operate in CFB's. Even though Petroleum Coke may not be considered a renewable resource by many since it is produced by the Petroleum industry, it is cheap carbon source that should be taken advantage of to produce electrical power.

Like coal, Petroleum Coke may usually be transported by rail not far from the place of its generation. In fact, it appears that only around less than 20 states implement the use of Petroleum coke for power generation according to the EIA. This may mostly be due to the fact that it is not transported far from the places of its generation, which are oil refineries. Petroleum coke also has the advantage in that it can be used to generate hydrogen for electrical fuel cell generation, which is also a cleaner renewable energy based technology. In most of these systems, petroleum coke would also be gasified and then steam reformed into synthesis like gas where hydrogen is then produced. Hydrogen produced from the synthesis gas from petroleum coke has been experimented with solar reactors as well as molten carbonate type of fuel cells [ 3. Trommer 2005 & Cherepy et al 2005 ]. There has also been mention for the use of petroleum coke based power plants in sequestering carbon dioxide by putting it underground near oil wells. This would help to replenish an existing oil well that is partially depleted. Since many oil refineries may be near oil wells, it may make sense to use petroleum coke as an energy source near oil wells and oil refineries. An advantage of petroleum coke is that it is a cheap source of energy and it may be abundant. It is said that petroleum coke is less expensive as an energy source than natural gas. It is uncertain by the author what other products petroleum coke is used as other than electrical energy generation. It is known that coal based coke is used in producing other types of products, somewhat from the tars that are generated. Even though petroleum coke is derived from the petroleum industry, it is a potential energy source that can be used in electrical energy generation, whether it drives turbines or produces hydrogen for fuel cells. The fact that it is cheap and abundant makes it an ideal energy source to help solve our sustainable energy needs.

REFERENCES

1. "Hydrogen Production by Steam-Gasification of Petroleum Coke using Concentrated Solar Power - I. Thermodynamic and Kinetic Analysis", International Journal of Hydrogen Energy Vol 30 No 6 pgs 605-618 [2005] by P.Trommer, F.Noembrin, M.Fasciana, D.Rodriguez, A.Morales, M.Romero, A.Steinfeld

2. "Net Generation by Energy Source", Energy Information Administration (EIA) [2009]

3a. Same as Reference #1

3b. "Direct Conversion of Carbon Fuels in a Molten Carbonate Fuel Cell", Journal of the Electrochemical Society Vol 152 issue 1 pgs A80-A87 [2005] by NJ Cherepy, R. Krueger, AF Jankowski, JF Cooper

KEYWORDS: Petroleum Coke, Sulfur and Metal Content in Petroleum Coke, Hydrogen Generation from Petroleum Coke, Heavy Oil Refinery, Carbon Sequestration in Underground Wells, Solar Generators of Synthesis Gas, Price and Abundance of Petroleum Coke, Circulating Fluidized Beds, Pulverized Petroleum Coke, Pulp and Paper Mills, Cement and Brick Kilns, Products from Petroleum Coke, Electrical Generation from Petroleum Coke

Photos taken from Picasa and graph generated from EIA source 2009 data

Three types of Biofriendly Solvents can use Renewable Resources, are Biodegradable or are Good Cleaning Solvent Candidates

Several types of alternative solvents may be favorable in the future due to environmental factors, practical applications and the use of renewable resources that could be used to produce them. Many different types of solvents can be made from renewable carbon based feedstocks, but overall it comes down to economics or whether bio-based solvents can be made just as cheaply. Many years ago, this wasn't even a consideration as biobased solvents cost at least several times more than petroleum based solvents. Advancements in process technologies and materials are allowing bio-based solvents to be made a bit more cost competitive. In this essay, three types of eco-friendly alternative solvents are examined towards practical applications that will be very much in demand. These solvents are also compared as to their biodegradability and reuse of renewable resources. These three types of solvents are proplene carbonate, ethyl lactate and methyl soyate. The first two can be made from renewable resources and the last is made from plant sources. While the last two are mainly biodegradable, therefore their practical usage could be meant for cleaning purposes with solvents. Soy esters and ethyl lactate can be used in formulations for various types of cleaning products, where usually just a component is made from one of these types of biosolvents. Products using these solvents are sold on the markets, the other day I found cleaner advertised to contain ethyl lactate that was an epoxy & adhesive cleaner. Ethyl lactate could be used in more cleaning products but it's cost of production is fairly high compared to other cleaning solvents. For example, methylene chloride costs around 30-35 cents per pound while it costs around $1.50 - $2.00 per pound to make ethyl lactate [ 1. K. Watkins 2002 ]. Of course, this was several years ago and it has been claimed that improvements in technology are cutting these costs by close to half. Ethyl lactate can be made with carbohydrate renewable resources that produce lactic acid from fermentation. Ethyl lactate is very non-toxic and friendly towards the environment and human health. For example, even though it is a volatile organic chemical it would not cause atmospheric pollution such as ozone depletion, in addition, the FDA considers Ethyl Lactate so non-toxic for human consumption that it could be used as an ingredient in food products [ 2. S. Aparacio et al 2009 ].

Soybean based esters like those used in biodiesel are made from crushed soybean oil. Soy esters like Methyl Soyate can then be produced and be used in a number of cleaning product formulations such as those used in cleaning applications like degreasing parts, concrete & graffiti surface cleaners, ink & adhesive removers and parts washing. Since methyl soyate is made directly from soybeans it is not considered as produced from renewables, but it is an attractive solvent because it has low eco-toxicity and may have other environmentally friendly applications such as it's use as a specific lubricant. Propylene carbonate is a solvent that can be partially made from renewable sources. It has many favorable properties as use for a solvent such as a high boiling point. Propylene carbonate can be made from the combination of an epoxide and carbon dioxide produced over a catalyst [ 3. Z. Bu et al 2010 ]. Carbonates in general could be used in helping to make products from organic synthesis reactions when used as a supporting solvent or even chemical feedstock. For example, DMC (dimethyl carbonate) - can replace Phosgene in chemical synthesis reactions. Phosgene is known as a toxic chemical. Carbonate solvents themselves can serve as starting materials for the production of plastics called polycarbonates which are used in a large number of goods which include automotive materials and electronic parts [ 4. J. Parrish et al 2000 ]. Most of the these eco-friendly can be used in a variety of applications such as those mentioned for carbonate solvents. In fact, several types of carbonates are used as electrolyte material in batteries. Ethyl lactate also has a variety of purposes in the semiconductor and electronics industry, as it can be used to exclusively clean electronic parts replacing the need to use halogenated type solvents it can also be used as a solvent to produce various electronic devices. These environmentally friendly solvents can help drive forth the use of renewable resources towards the end of sustainable products which do not solely rely on petroleum resources. The practicality towards their use comes down to overhead costs and experimental imagination towards their practical application. For example, the biomedical and pharmaceutical areas also have great if not greater needs to implement the use of 'Green Solvents' towards production. A large goal of these industries is to become very eco-friendly in a matter of decades. The use of soybeans for alternative products other than food products becomes a questionable issue, however, the author feels that they should be acceptable for overall use until better natural products are invented towards similar product purposes.

REFERENCES

1. "A Solvent Business: Ethyl Lactate Seeks to Replace Work horses like Acetone and Methylene Chloride" Chemical and Engineering News vol 80 no 2 pgs 15-16 [2002] by K. Watkins

2. "The Green Solvent Ethyl Lactate : An Experimental & Theoretical Characterization" Green Chemistry vol 11 pgs 65-78 [2009] by S. Aparacio, R. Alcalde

3. "Synthesis of Propylene Carbonate from Carbon Dioxide using trans-dichlorotetrapyridine-ruthenium III as catalyst" Applied Organicmetallic Chemistry vol 24 issue 11 pgs 813-816 [2010] by Z.Bu, Z.Wang, L.Wang, S.Cao

4. "Perspectives on Alkyl Carbonates in Organic Synthesis", Tetrahedron vol 56 pgs 8207-8237 [2000] by J.Parrish, R.Salvatore, KW Jung

KEYWORDS: Ethyl Lactate, Methyl Soyate, Soybean Ester Solvents, Propylene Carbonate, Dimethyl Carbonate, Carbon Dioxide used to Produce Solvents, Cleaning Solvents, Degreasing and Parts Cleaning Solvents, Solvents in Electronic Industry, Polycarbonates, Production of Solvents using Renewable Resources, Eco-friendly Solvents, Biodegradable Solvents, Non-Ozone depleting Solvents

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