Energy Crop Sweet Sorghum Breeding and Energy Conversion Technology
on Ethanol production from Sweet Sorghum Stem

Mr.Wang Mengjie Research fellow; Mrs.Sun Hong Senior Agronomist; Mr.Xiao Mingsong Senior Engineer
P.R. China

During the 9th Five-Year-Plan period (1996~2000), we completed the Research Project on Energy Crop-Sweet Sorghum Development and Comprehensive Utilization for the State Science and Technology Commission. During the 10th Five-Year-Plan period (2001~2005), we completed the Project on Energy Crop "C Sweet Sorghum Breeding and Energy Conversion Technology Research and the Project on Ethanol from Sweet Sorghum Stem for National Hi-Tech Research and Development Program (863 Program)

The results of the projects are: develop 5 hybrid species (Chuntian Series: #1~#5) from single sweet sorghum species in order to suit the plantation in different areas and circumstances. Under normal conditions and scientific management, sweet sorghum stem production is about 60 t/ha, and seed 4.5 t/ha. In Huhehaote, stem production is 75 t/ha, and seed 7.5 t/ha; in Heilongjiang, stem 90 t/ha, seed 6 t/ha; in Xinjiang, stem more than 105 t/ha, seed more than 3.75 t/ha; and in West Hunan, stem 112.5 t/ha, seed more than 7.5 t/ha. Brix of the stem juice is more than 18%, and sweet sorghum stem of 1/4 hectare can produce 1 ton of ethanol. Solid residue after ethanol production can be used in various ways.
Even planted in bad soil such as salt and alkali land, Chuntian-Series sweet sorghum grows well in North Jiangsu and Dongying of Shandong. (See photos and the local farmers' words)

Technology on ethanol from sweet sorghum stem includes two core techniques: solid fermentation of sweet sorghum stem and liquid fermentation of stem juice.

Solid fermentation of sweet sorghum stem:

1. Based on the rational transportation radius of sweet sorghum stem, dispersedly construct breweries with capacity of 2,000 t/year. Mechanically crush and knead the stem to about 2cm, braise (depending on the temperature), mix with bacteria, and ferment. Then, original alcohol with concentration of 60~65% is produced. Finally, transport the original alcohol to the central plant and rectify into fuel ethanol. The simple equipment, low investment, the short factory construction period, and easy operation make it very convenient to disseminate. It is labor-intensive, and in line with the guideline of China distributed energy base construction.
2. Distributed original alcohol production and centralized rectification enable the high utilization rate of equipment. The more important advantage of the technology is that the process of original alcohol production does not produce any waste water and pollutant and that the waste water from rectification is mainly the clean water in the original alcohol.
   

Liquid fermentation of sweet sorghum stem juice:

1. Squeeze the sweet sorghum stem to produce juice, adopt fixed-yeast multi-pole continuous-fermentation technique, and then rectify into fuel ethanol. The technology is suitable for high-tech, high-efficiency, and large-scale industrialized construction.
2. The large area of contact of fixed-yeast carrier and the juice improves the reaction speed: the fermentation period is 6~10 hours. The capacity of alcohol production is much improved, and the fermentation speed is 4~6 times of the single-concentration batch fermentation technology.
3. Because the yeast is proliferated inside the carrier, it is not easy to age, and life of the yeast is prolonged. Thus, less preparation of yeast liquid is needed, and organic waste disposal decreases. The production process decreases much amount of waste water disposal compared with traditional technology of ethanol from food crop.
4. The technology adopts multi-pole in-series continuous-fermentation equipment. Its small volume, high efficiency, and small land occupation can decrease investment on infrastructure construction. By calculation, investment for such a plant is less than an ethanol plant from food crop with the same capacity.
5. Automation production is easy applied to this technology. Perfect monitoring and controlling system can ensure the quality of the product and save human resources and energy consumption. At present, the middle-scale experiment of the technology has be completed. It can be industrialized after the financing condition matures.
6. Currently, there are 5 demonstration projects in China, with the total production capacity of over 10,000 t/year, and in Heilongjiang, Xinjiang, Shandong, Liaoning, and Inner Mongolia, respectively. Years of operation shows the production cost of fuel ethanol averages 4,000 yuan/t, approximately equaling to the price of oil in the international market (70 dollar/barrel). We believe, after the Renewable Energy Law of the PeopleˇŻ Republic of China come into effect in 2006 and the fuel ethanol market opens, the industry of ethanol from sweet sorghum stem will grow vigorously, and the fuel ethanol in line with the national standards will have wide market.

Meanwhile, solid residue after alcohol production can be used in production of forage for cow and sheep, gasification and electricity generation, pulp production and paper making, pollution-free fiberboard production, and bio-diesel production. The benefit of comprehensive utilization of sweet sorghum is remarkable. For farmers, plantation of sweet sorghum can earn 100~150 yuan more than plantation of corn. One ton of fuel ethanol can replace one tone of fuel oil; replacement of one ton of fuel oil means reduction of 3 tons of CO2 emission, which may be support by the CDM mechanism. Application of fuel ethanol can decrease the pollutant emission from vehicles and thus improve the atmosphere environment. The technology is formally included in the National Medium- and Long-Term Plan of Renewable Energy Development.

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