Concentrated acid hydrolysis will transform virtually any cellulosic feed into fermentable sugars. BlueFire Ethanol, located in Irvine, California, has developed an advanced, proprietary version of this process which they believe could make them the first company to deploy a commercial scale cellulose to ethanol refinery that generates a return to its investors.
The process relies on reusing more than 96% of the sulphuric acid that is used to initially break down the cellulose from the lignin, as well as using the lignin to provide up to 70% of the total plant’s energy requirements. Although from the diagram (below) it doesn’t appear BlueFire’s process is simple, in reality it is one of the most straightforward and proven cellulose to ethanol processes known. BlueFire has adapted and improved a process that was used in WWII era Germany at an industrial scale to refine vast amounts of ethanol from cellulosic feedstock, and pilot plants already operated by BlueFire have successfully refined ethanol from sorted municipal solid waste, wood chips, as well as rice and wheat straw.
In summary, the process might be described as follows: Waste biomass, ground and dried, is mixed with sulphuric acid and reduced to a paste and heated in the 1st stage hydrolyser – depending on the feedstock this process may be repeated in a 2nd hydrolyser. The hydrolyzed cellulose and hemicellulose, along with the acid, is then separated from the lignin in a plate and filter press. The lignin is used for fuel for process steam, feedstock drying, and plant power. The acid and sugar solution that has been separated from the lignin is itself separated, with 96% of the acid being extracted for reuse. The sugar solution is then fermented with yeast and distilled, with the water captured for reuse and the ethanol collected for distribution.
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CONVERSION OF CELLULOSE TO SUGARS USING CONCENTRATED ACID HYDROLYSIS
A proven method, reusing the acid and water inputs, and using the waste lignin
to generate most of the energy required, makes BlueFire’s technology an
attractive contender to be first to commercially refine ethanol from cellulose.
(Photo: BlueFire Ethanol)
One convincing aspect of this process regards the synergy created by using the lignin for heat energy and the cellulose for ethanol fuel. If all of the biomass were burned to create electricity, the energy efficiency would be about 25% – that is, an efficient biomass plant will require 13,000 BTUs of biomass feedstock to generate one kilowatt-hour, which is about 3,420 BTUs. At 15.0 million BTUs per ton (on the high side) of biomass and at a wholesale electricity price of $.07 per kWh a biomass electricity plant operating at a 25% efficiency will earn $77 per ton. But using BlueFire’s process, each ton of biomass can be refined into 70 gallons of ethanol, which at $2.00 per gallon earns nearly twice as much, $140 per ton – and, the manufacturing costs are lowered because the lignin from the feedstock is still used to provide most of the energy requirements of the refinery.
BlueFire Ethanol has already received DOE funding and a conditional use permit from Los Angeles County to begin construction of a commercial scale refinery to produce ethanol from biowaste. Sited next to a landfill in Lancaster, California, this plant will be able to use municipal waste feedstock for which there is already a preexisting collection and delivery. One of the advantages of processes such as BlueFire’s, that can use municipal solid waste as feedstock, is the yield of waste relative to the territory surrounding the plant is quite high, and already serviced anyway. But instead of going into the landfill, the BlueFire’s Lancaster facility will divert 125 tons per day into the refinery to produce 3.2 million gallons of ethanol per year.