|BRI Process schematic. Click to enlarge.
BRI Energy, a company that ferments gasified waste, biomass or hydrocarbons such as coal into ethanol (earlier post) announced tentative plans to build one or two gasification-fermentation facilities in Oak Ridge, Tennessee.
BRI hopes for federal loan guarantees for part of the funding of both projects: one to convert western coal to ethanol, and the other to convert burnable municipal waste (paper, plastic, garbage, leather) to ethanol.
The coal gasification facility would cost $25 million, and the company is seeking a $20-million federal loan guarantee. The municipal waste facility would require $62.5 in private investment and a $250-million federal loan guarantee.
The BRI process utilizes a culture of anaerobic acetogenic bacteria (Clostridium ljungdahlii) that ingests syngas and emits ethanol at a yield of some 75 gallons or more per dry ton of biomass. From used tires or hydrocarbons it can yield approximately 150 gallons or more per ton.
The first stage of the process uses established gasification or plasma arc technologies to generate a carbon monoxide-rich syngas. During the gasification process, the temperature and access to outside air is controlled and restricted in two sequential chambers. Because of this, the air emissions are minimal.
The carbon monoxide gas exits the gasifier at temperatures up to 2,200°F, then must be cooled to 100° before being fed to the microorganisms. This process generates an immense amount of waste heat that can be used to create high-temperature steam to drive electric turbines.
In the second stage of the process, the C. ljungdahlii bacteria ingest the carbon monoxide gas and produce ethanol, acetic acid, hydrogen and water.
There are a number of anaerobic bacteria in addition to C. ljungdahlii that can utilize the components of synthesis gas (CO, CO2, and H2) as carbon and energy sources : Clostridium thermoaceticum, Clostridium autoethanogenum, Peptostreptoccus productus, Eubacteriam limosum, Butyribacterium mehylotrophicum, and Clostridium acetobutylicum.
The basic chemistry of the conversion of syngas to ethanol and acetic acid by C. ljungdahlii is as follows:
6CO + 3H2O → CH3CH2OH [Ethanol] + 4CO2
2CO2 + 6H2 → CH3CH2OH + 3H2O
4CO + 2H2O → CH3COOH [Acetic acid] + 2CO2
2CO2 + 4H2 → CH3COOH + 2H2O
The last step is to separate the ethanol from the hydrogen and water. This is accomplished through the same distillation process that is currently being used in traditional corn and sugar to ethanol plants.
BRI expects to develop modular plants the capacities of which can be expanded. The company envisions a single module combining two gasifiers, each with a capacity of approximately 125 tons of feedstock per day, and two fermenters.
BRI President William Bruce is testifying before the Senate Energy and Natural resources Committee today in a hearing on Coal Gasification.