EFFECTS OF EXPERIMENTAL COALIFICATION ON TEXTURE, COMPOSITION AND COMPACTION IN INDONESIAN PEAT AND WOOD

Artificial coalification can fill a gap in our understanding of the pr ocesses of natural maturation of coal in a time frame reasonable for s cientific investigation. This study focused on two main aspects of the coalification process. These aspects were, first, the effects on carb onised components in peat and, second, the amount and location of comp action during coalification. It was found that the proportion of the c arbonised components increased during artificial coalification while t he proportion of amorphous matrix decreased. These relative changes in proportion of constituents may be the result of the differing reactiv ities of these components. Compaction during artificial coalification resulted in a 72% volume loss (Or a 5.7:1 compaction ratio). Most of t he volume loss was from a decrease in pore space (45%) between the par ticles of organic material, although compression of plant parts accoun ts for 17% of the volume loss. The remaining 10% of the compaction was from organic mass loss, in out-gassing and fluid expulsion. Finally, although it was observed that compaction of wood was of the order of 2 .5:1, it does not occur uniformly across all anatomical structures. Xy lem tracheids appear to have compacted little and the majority of wood compaction appeared in the ray parenchyma. However, the compaction ra tio in the rays was relatively low (1.5:1), considering that ray paren chyma should compress easily as they lack secondary cell walls and the cells thus have less inherent strength to withstand compression than xylem tracheids. However, it appears that the ray parenchyma are fille d with solid organic residues at or before the time of burial, which p revents the compression of cell lumens. This suggests that the tissue would have originated from the heartwood of trees where tannins and ot her waste products are stored in ray parenchyma cells. Although the ab ove observations are based on a limited sample set, the results do pos e interesting subject matter for further study. In particular it is es sential that different peat types be examined in order to understand t he changes in proportion of organic components during coalification. I t has also been demonstrated that compaction occurs mainly as a loss o f pore space between organic particles; however, the degree of materia l loss still needs to be documented in different peats of varying deco mposition states. Copyright (C) 1996 Elsevier Science Ltd