Biobutanol (C4H10O) or butyl alcohol is a second generation biofuel that can be produced from biomass and can be used either as an industrial chemical or as a transportation fuel. Biobutanol can run in any gasoline engine with no modifications and, like ethanol, has a higher octane rating than normal gasoline. It has the additional advantages that it has a higher energy density than ethanol, can be transferred in our existing pipelines, and can be used as an additive in either gasoline or diesel fuel.
Like ethanol, biobutanol is fermented by microorganisms from sugars, which are broken down from raw feedstocks and mixed with water. For the butanol process, the microbes have been genetically modified to produce an alcohol with a longer chain of hydrocarbons. The fermentation step is followed by a separation step in which the alcohols are separated from the fermentation steep. Since butanol doesn’t mix with water at high concentrations, the finished fuel can be stored easily and transported within existing gasoline pipelines.
Since the cost of the feedstock is the major cost factor, the ability to use low cost non-food feedstocks is a major challenge to cost effective butanol production and much work is being done to develop microbes that can be used with a variety of feedstocks.
The other key research challenge that must be resolved is that butanol production inhibits microbial growth even at low concentrations. The result is that the maximum butanol concentration in the steep of a conventional (ABE) process is about 1.3 % butanol. The overwhelming majority of the fermentation broth is water and an energy-intensive distillation step has traditionally been used for separation of the butanol from the water. This has caused the production of industrial butanol by fermentation to be abandoned. Much research is now being done to develop microbes are sustainable in higher concentrations of butanol, so as to reduce the power consumption of the separation process. At the same time, separation process are being developed that are less energy intensive.
Cobalt Biofuels, Mountain View, California, recently announced that it has raised $25 million in equity to accelerate the commercialization of biobutanol. The Series C equity round was co-led by LSP and Pinnacle Ventures and included both new and existing investors.
"With this round of funding Cobalt Biofuels will move aggressively toward commercial production of cost effective, non-food based biobutanol,” said Pamela Contag, President and CEO of Cobalt Biofuels. New Energy and Fuel reported that Cobalt is using these funds to expand from laboratory scale production to a pilot scale facility with a capacity of 35,000 gallons of fuel per year .
Cobalt has proprietary technologies in microbial physiology, strain development, fermentation and low-energy fuel separation, which they claim make possible a new generation of fuels that burn cleaner, are more cost-effective, and enhance environmental sustainability.
According to Cobalt, biobutanol is a next generation biofuel that can be used as a standalone transportation fuel, as an additive to gasoline or diesel fuel and as an additive to improve the properties of ethanol. Unlike ethanol, biobutanol can be used at full strength in today’s automobile engines and can be distributed through existing pipelines.
Cobalt technology will change the biofuel industry by:
- Allowing production of biofuels from local feedstocks based on regional agricultural priorities, including plants that are not subject to food price fluctuations
- Increasing the rate of biofuel production through continuous fermentation
- Improving yield by optimally pairing fermentation organisms with a diversity of feedstocks
- Its patented vapor compression distillation separation system significantly reduces energy and water requirements
Cobalt claims that their process can produce biobutanol from a broad range of non-food feedstocks, as well as more traditional feedstocks including corn and sorghum, thus reducing the risks associated with reliance on a single crop. As a result, they should be able to site their facilities in a wide range of geographies and use the feedstock available locally.
The cost of feedstock dominates the overall cost of producing biofuel, and the efficiency of biomass conversion (yield) is greatly dependent on the microorganism utilized in the biofuel production process. Cobalt is developing and patenting a high-throughput process to identify the optimal microbe for any selected plant substrate. This technology will allow them to efficiently match organisms to each regionally appropriate feedstock.
They are developing and patenting key production monitoring technologies that will enable the fermen-tation process to run continuously. Their fermentation process differs significantly from the traditional batch processes used today to convert starch to alcohol fuel. Their patented reaction management technology maintains their continuous fermentation process at peak production rates and an optimal concentration of butanol in the steep, for extended periods of time.
The concentration of befoul, in the fermentation steep determines the cost of the energy intensive separation process. Cobalt’s patented fluid separations technology (termed vapor compression distillation, or VCD) removes alcohol from the fermentation steep using one-half the energy required for typical separation techniques.
The concentration also determines the overall water usage of the biorefinery. Cobalt’s technology has the additional advantage of drastically reducing water usage. By capturing, filtering, and recycling the VCD-water back into the fermentation process, it minimizes requirements for fresh water resources and eliminates disposal of large quantities of waste water,
While details of the process have not been revealed, Cobalt seems to be addressing the technical limitations of traditional fermentation process for production of ethanol. Their ability to develop microbes that can be used with a variety of feedstocks enables wide geographic use of their process as well as enabling the use of low cost feedstocks. Continuous fermentation may enable higher butanol concentrations in the fermentation process and their engineered microbes may be able to withstand a higher concentration in the steep. Their use of vapor compression distillation (VCD), which I am very familiar with, having developed and implemented such a process, is a major energy reduction element which can also eliminate the use of a fuel for heating, the necessary heat coming from the energy input in the compression step. Their closed loop approach to water usage is a major environmental improvement.
All in all they seem to be addressing the important limitations of conventional processes. Their ability to raise capital in the present "credit crunch" environment is a testimony to their ability to pass the due diligence of the investors. Only time will tell whether their "improvements" are sufficient to enable a reliable, cost effective process.