Rice Straw Ethanol

After rice is harvested from the paddy and processed, there is a large amount of biomass waste. Previously noted was the conversion of agricultural waste from rice farming into useful energy. In the previous post, the focus was upon using rice husks as feedstock.

The focus for this post is on rice straw as feedstock. Gasification yields Syngas and by weighting the gaseous products in the reformer, i.e., regulating the ratio of H2 to CO, the Fischer-Tropsch process yields ethanol. Between 2002-2004 NREL (National Renewable Energy Laboratory) operated1 a pilot plant gasifier, testing Syngas conversion.

Thermal polymerization is a thermal conversion process that occurs in a high-temperature, sub-stoichiometric environment, i.e., insufficient oxygen is present in the reaction to convert all organic carbon to carbon dioxide. In the case of converting municipal solid waste to oil, Wikipedia explains that it is done under high heat (e.g., 250C) and very high pressure (40 MPa). Liquefaction is similar to thermal gasification. However, in the case of liquefaction, the reactions are shifted in favour of a high yield of liquid byproducts.

More needs to be known about the environmental consequences of the gasification of bio-solids, before the relative risks become overshadowed by the need for energy.

Mike Millikin2 relays a report from The Nikkei that in fiscal year 2008 the Japan Ministry of Agriculture, Forestry and Fisheries plans to start experimenting with rice-straw derived biofuel. Since FT technology is well-established and the machinery is set on the “Syngas Spin cycle”, development of “ceeoh” from rice straw will focus on the bollocks making the process commercially viable with emphasis given to collection and preparing the straw for pyrolysis. One might imagine that, similar to the Best Energies process, part of the Syngas will go toward drying and carbonification.

The Fraunhofer Institute - Europe’s leading applied technology institute - is developing a highly efficient circulating fluidized bed combustion system that unlocks the energy potential contained in biomass residues.

I became interested in BTL (Biomass To Liquid fuel) processes since, theoretically, a plug-in, flex-fuel vehicle could use the electricity generated to re-charge on-board batteries and the ethanol in the range extender.

The Syngas can fuel a gas turbine generator and the heat from the process powers a separate HRSG (Heat Recovery Steam turbine Generator). IGCC (Integrated Gasification Combined Cycle systems) could mean better efficiency, yet the as significant challenge is to achieve less CO2. while the production of “Syngas” by the gasification of carbon-bearing feedstock does well in an economic analysis, it does less well environmentally, i.e., in terms of aggregate increases in greenhouse gases or toxins.
Similar Posts: Plasma Arc Gasification Integrated Biofuel Production - Part 1 Forestry Waste to Syngas via High Temperature Gasification Combined Heat and Power from Rice Husks Catalytic Gasification of Wet Biomass

1Gridley Ethanol Demonstration Project Utilizing Biomass Gasification Technology (PDF) 2Japan Plans to Export Production Process For Rice-Straw Cellulosic Bioethanol
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