In December, Atlantic City officials announced construction of commercial scale solar project, and five commercial scale wind turbines working in conjunction to provide on-site power to their waste treatment facilities. How much potential do gasification and conversion processes have in the emerging energy economy?
Last May DOE awarded Abengoa $2.25M for development of bio-syngas to ethanol. In an article about a joint effort of Abengoa Bioenergy, UOP, Argonne National Laboratory (ANL), Pacific Northwest National Laboratory (PNNL), and Washington University, Green Car Congress notes that “the use of low-value biomass* and a simple process should lower the capital investment and total energy consumption.”
For one thing, the yield of a motor fuel from biomass should be higher for fuels produced by gasification / synthesis than by hydrolysis / fermentation. In the first technique, all the carbon can be pyrolized and converted to fuel; in the second, only carbon convertible to sugar can be used to produce fuel.
* Note: What is implied by the term, low-value biomass. is perennial feedstock harvested from marginal use areas having been grown without the benefit of fertilizer, irrigation, or pesticides, e.g., fast-growing hays like switchgrass and short-rotation woody crops like poplar.
The same article noted that Starbourn-Triton is building “two gas-to-ethanol plants—one in Columbus, Ohio, the other in the UK. The plants are expected to produce 25,000 to 50,000 gallons of ethanol per day. They claim that their proprietary process “can use a variety of alternative fossil-based or waste-sanitary biomass feed stocks to generate high-test ethanol at a greater volume and at almost 50% lower cost than current fermentation-based methods.” Chemical Processing in High-Pressure Aqueous Environments. 7. Process Development for Catalytic Gasification of Wet Biomass Feedstocks (.pdf, 599Kb)
As Jamais Cascio previously suggested, could you imagine if every municipal waste treatment plant could produce power? GCC tells us that Future Fuels, Inc. “recently announced plans and funding to build a 52-million-gallon per year biomass / waste-to-ethanol facility in New Jersey.”
While more development now is focussed on catalysts, GCC also has another article that focuses more on co-production of Fischer-Tropsch fuels and electricity. Thermal gasification of biomass also can yield biofuel and electricity.
The gasification / synthesis development now underway began some 20 years ago following the last set of oil crises. Nonetheless, developing economically and environmentally viable systems is complex; for example, one choice is how the actual gasification should proceed, i.e.,
- A one-step high-temperature path (used by Shell, Uhde, Future Energy, Chemrec and others) to push the feedstock straight up to its 1,300ºC temperature. This is similar in approach to coal-based gasification systems.
- Or, a two-step process (with a medium intermediate temperature (used by Choren, Värnamo/Chrisgas and others). This approach enables more optimization, and allows for intermediate gas cleaning, but also has its downsides (soot/coking).
Another decision to make is what feedstock to use:
The CO2 emission profile from these processes depends on the process technology, whether the energy source for conversion is biomass only or whether an external energy source is used, and whether the biomass is a waste product (e.g. straw) or an energy crop.