Rice is the world's most important staple food, used by more than three billion people around the globe. The crop's production has doubled over the past 40 years and demand keeps growing. Now the Fraunhofer Institute - Europe's leading applied technology institute - has developed a highly efficient circulating fluidized bed combustion system that unlocks the energy potential contained in rice residues. Researchers from the institute's department of industrial automatisation are collaborating with scientists from the Hanoi University of Technology to test the system on a large and continuous scale after first tests in Magdeburg proved to be successful. For rice producing countries, the bioenergy potential from husks is considerable.
After paddy rice is processed, a large amount of biomass with a relatively high energy content (18 Gj/ton - higher heating value) is left over in the form of rice husks. According to the IEA's Bioenergy Task 33 on thermal biomass gasification, for each ton of processed rice, roughly 280kg of husks are left over, worth around 120 kWh[*.pdf]. Now consider that the world's total rice production in 2005 was 618 million tons (FAOStat), then it is not difficult to see the energy potential (if all this biomass were used in efficient gasification or combustion systems, it would yield roughly 266 Petajoules or 74 TWh of energy, which comes down to around 43.5 million barrels of oil - renewable energy from a waste stream).
For a country like Vietnam, which produced 36 million tons of rice in 2005 (FAOstat), such biomass combustion systems would mean a boost to its energy portfolio. That is why the collaboration with the Fraunhofer Institute is considered to be invaluable and has been sped up, since demand for energy in Vietnam is growing rapidly and high fossil fuel prices have become a real burden. Vietnam produces enough rice residues to provide 4.3 TWh of electricity, enough to satisfy the energy needs of around 1 million people for an entire year (for per capita energy consumption statistics, please visit the World Resources Institute's Earth Trends database).
Fraunhofer's 'circulating fluidized bed combustor' suspends the solid biofuel on upward-blowing jets of circulating air during the combustion process. The result is a turbulent mixing of gas and solids. The tumbling and circulating action, much like a bubbling fluid, provides more effective chemical reactions and heat transfer. The combustor reduces the amount of sulfur emitted in the form of SOx emissions as well as NOx. Fraunhofer's approach has been to study the exact combustion behavior of rice husks as they travel through the system. The combustor was then custom-designed to match those qualities. Dr.-Ing. Lutz Hoyer, project leader, explains the rationale behind the development of this system specifically for rice husks:
:: biomass :: bioenergy :: biofuels :: energy :: sustainability :: rice :: residues :: Vietnam ::
"These studies are very relevant to the market in Vietnam. Our aim is to deliver a competitive technology that can beat fossil fuels. Moreover, the environmental burden of burning fossil fuels is reduced with this biomass system that has universal appeal". His counterpart at Hanoi University of Technology, Dr. Pham Hoang Luong, adds: "Our university is currently investing in research and development. Fluidized bed combustion of biomass is one area where our future engineers will work on. Our collaboration with Fraunhofer is therefor much needed and appreciated."
After more tests in Magdeburg, Germany, the combustor will be transferred to Hanoi University in october to perform full-scale, long-term trials.
Fraunhofer: - Strom aus Reisschalen: Wissenschaftler aus Magdeburg und Hanoi erforschen Energiegewinnung aus Biomasse
Déchets: Les grains de riz, bientôt producteurs d'énergie? (August 14, 2006)