Synthetic coal and methods of producing synthetic coal from fermentation residue

Abstract

The invention herein describe a novel process for producing a novel synthetic coal product from fermentation residues, such as, the waste materials from fermentation based ethanol production. The fermentation residue is subject to a hydrothermal carbonization process in an aqueous solution at a temperature and at a pressure sufficient to form a synthetic coal solid and a liquid component. This process does not require drying of the fermentation residue which provides for a more energy efficient method of processing thereof. The synthetic coal solid has a high heat content combustive material. The liquid component has nutrient value so that it can be recycled thereby permitting the sustainable recycling of such nutrients and the water in which those nutrients are dissolved.

Description

BACKGROUND OF THE INVENTION[0001]A major pollution problem concerns the effect of carbon dioxide, a greenhouse gas, being released into the atmosphere as the result of burning fossil fuels. Currently, approximately 70 million tons of carbon dioxide gas enters the earth's atmosphere every day due to the worldwide burning of coal, oil, diesel fuel, kerosene, gasoline, natural gas and the like. This fossil fuel use causes a concentrating of an unnatural amount of carbon dioxide in the atmosphere. Carbon dioxide is able to absorb heat energy that radiates from the earth and thereby captures and retains heat energy within the earth's atmosphere. Thus, the overwhelming majority of climatologists agree that the burning of fossil fuels is the major contributor to the current warming of the earth's atmosphere. For this reason, there will be increased regulation of fossil fuel-based carbon dioxide gas emissions and a proportional increased interest in finding alternative renewable, nonpolluti...

AI Technical Summary

Benefits of technology

[0015]Thus, it was surprisingly discovered in the present invention that HTC could be applied to fermentation residues and result in a char product. This was surprising because the prior art taught that the production of chars required the use of high cellulosic content substrates. It was also surprising that a char was formed because the makeup of WDG, for example, is completely unlike that of wood, or other cellulosic biomasses that consist primarily of cellulose, hemicelluloses and lignins. For example, as stated above, corn based WDG consists of a small amount of residual fermentable dextrins and yeast, less than 20% by dry weight of cellulose, unfermentable dextrins, protein, fat, low concentrations of metal salts, and water.

[0016]The invention herein produces a coal-like char product that is similar to natural bituminous coal in terms of percent carbon content and energy equivalency while at the same time containing relatively low levels of sulfur and contaminant heavy metals. The char produced by the process of the present invention can be used as a fuel and burned to provide an energy source comparable to bituminous coal in terms of BTU's produced per unit weight. However, unlike natural coal and other fossil fuels that are formed by the sequestration of carbon over millions of years, when the char of the present invention is burned no “new” carbon is added to the atmosphere. As is well understood, carbon dioxide from plant biomass is formed through photosynthesis. Thus, as the particular substrate is grown, e.g. corn, the carbon is extracted from the atmosphere and that same carbon is then returned to the atmosphere when the ethanol is burned. That carbon returned to the atmosphere is then extracted again in a subsequent corn growing season resulting in a carbon neutral process having no net addition of carbon thereto. The process of the present invention can also include the step of sequestering the char produced thereby by burying or storage thereof. Alternatively, the coal product of the invention can also be utilized as a soil additive to improve moisture retention and provide nutrients for plant growth. The coal product of the invention may also be useful for the production of industrial chemicals such as methanol, acetic acid and ethylene glycol, as well as preparing hydrocarbon fuels through gasification. The coal or char can further be utilized as a carbonaceous starting material for the production of coke used for the manufacture of steel. The coal / water mixture could also be employed directly into a fuel cell operated at low temperature. Furthermore, the aqueous solution by-product from the process herein can be used as a nutritive fermentation supplement and as a fertilizer. Furthermore, it has been discovered that much of the nitrogen and phosphorous contents of the fermentation residue processed through hydrothermal carbonization becomes transformed into water-soluble compounds. These compounds are found dissolved in the aqueous solution after the char has been separated therefrom. The phosphorous and nitrogen can then be used as a nutrient source for the growing of further grain crops that provide fermentable substrate materials such as corn. The aqueous solution can also be combined with a fermentation substrate prior to its fermentation thereby recycling and reducing the amount of water used in the production of ethanol.

Problems solved by technology

Of course, it is this very chemical nature that makes it difficult for these plant structural materials to be chemically or enzymatically attacked and broken down.

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