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- Characterization of Rice Straw as Substrate for Biomethanation
Characterization of Rice Straw as Substrate for Biomethanation
Thesis Abstract:
The different treatments examined exhibited varying degrees of effect on the six different components of rice straw.
The different treatments examined included chemical treatments using sodium hydroxide, ammonia, sodium hydroxide with neutralization using hydrochloric acid, potassium periodate, potassium permanganate, calcium hydroxide + sodium carbonate, sulfur dioxide, chlorine dioxide, neutral sulfite, and physical treatments such as grinding and steam pressure. The different components of rice straw (IR 36) studied were water solubles, hemicellulose, cellulose, lignin, alkali, soluble silica, and sand. The total loss in dry matter content due to each of the treatments was also noted.
Treatments using bases as well as those that involved boiling, like neutral sulfite and chlorine dioxide treatments, resulted in 35 percent and 39 percent loss in dry matter content, respectively. These treatments had great effects on the water solubles, hemicellulose, and lignin portions of the rice straw. In addition to these components, the bases also removed a considerable amount of the alkasli soluble silica.
The treatment using hydrochloric acid produced an 18 percent loss in dry matter content. The treatment removed about 35 percent and 48 percent of the water solubles and hemicellulose contents, respectively, while all the other components were barely affected.
Treatments using the oxidizing agents potassium periodate and potassium permanganate removed about 40 percent, 24 percent, and 12 percent water solubles, hemicellulose, and lignin content of the rice straw, respectively, with negligible effects on the other components. The treatments using potassium periodate and potassium permanganate resulted in 18 percent loss in dry matter content.
Calcium hydroxide + sodium carbonate-treated straw had a 97 percent increase in its water soluble content and a decrease in the hemicellulose, lignin and alkali soluable silica contents by 42 percent, 69 percent, respectively.
The sulfur dioxide treatment increased the water soluble content by 20 percent and decreased the lignin content by 33 percent.
The steam pressure treatment had negligible effect on the different components of the straw.
In all the treatments studied, cellulose and sand were the most resistant portions of the straw. The effect of each treatment on the rate of biogas production showed varying degrees of improvement. Treatments that used bases, neutral sulfite, ammonia, and sulfur dioxide showed marked improvements in their rate of biogas production.
The concentration of the biogas produced by volume methane fluctuated between 40 percent and 75 percent. Observable fluctuations occured during the first 30 days of the fermentation run. The gas composition stabilized as the fermentation systems became older. The biogas produced generated luminous blue flames which were very flammable.
All fermentations were run under neutral pH conditions. The regression equations showed positive coefficient for the water soluble, hemicellulose, and cellulose contents. Negative coefficients were noted for the lignin and alkali soluble silica fractions.