Submitted to: Characterization of the Cellulosic Cell Wall
Publication Type: Book / Chapter
Publication Acceptance Date: January 5, 2004
Publication Date: February 5, 2004
Citation: Inglesby, M.K., Wood, D.F., Gray, G.M. 2003. Non-conventional pulping effect on si02 in oryza sativa. Characterization of the Cellulosic Cell Wall. Interpretive Summary: Rice straw is an agricultural waste product; its burning has been banned in California. Consequently, nearly 1 million tons of this renewable resource, a low cost alternative to wood for many applications, are available in this state annually. However, only 3 to 5% are currently utilized for off-field uses. To increase rice straw utilization, easy-to-implement processing technologies will have to be explored. The challenge to overcome lies in the fact that rice straw contains large amounts of silicon dioxide, an inorganic component that interferes with many commercial wood-processing technologies, including pulping. Pulping processes remove undesired organic components from wood to recover cellulose, the most valuable component in wood. This study investigates the effect of chemical pulping treatments on the effect of silicon dioxide in rice straw. The results show that silicon dioxide can be removed or can remain with the cellulose component, depending on the treatment. Noteworthy is the fact that the ratio of inorganic/organic constituents can be deliberately adjusted. Consequently the findings encourage exploration of the idea that silicon dioxide may present a valuable fraction, either in its own right or in association with the cellulose component. That is, this work opens opportunities to utilize chemically treated rice straw for many applications, for example, to produce an array of unique reinforcement materials for composite applications.
Technical Abstract: In this study, rice straw and rice plant stems were subjected to non-conventional pulping / fractionation methods to investigate the treatment effects on the silica content and distribution of this substrate. The treatments included soda pulping, an acid-catalyzed ethanol, and a hydrogen peroxide catalyzed formic acid treatment. In addition, the Department of Energy, National Renewable Energy Laboratory, Golden, CO performed four exploratory clean-fractionation experiments on the rice straw. Total and acid insoluble ash contents of all samples were determined by modified Tappi methods. The final acid-insoluble ash fractions were submitted for elemental analysis to establish the amounts present of silicon and of other inorganic constituents. The soda pulping treatment reduced rice straw and stem silica contents to below 2% based on sample weights. For all other treatments it was shown that the silica remained with the solids fraction as was evidenced by apparent SiO2 content increases. The localization of SiO2 in untreated and treated rice stem tissue was determined by energy dispersive X-ray (EDX). 2-D elemental spatial distribution maps clearly showed the distinct localization of silicon in stem control samples. The formic acid treatment appeared to affect the silicon distribution in stem tissue. The use of FTIR as a rapid qualitative tool for the detection of SiO2 was explored.