::: 80 



"5 



'c 



0) 



60 



- 40 



20 



Legend: 



Treated 



Dead 



Green 



C 



•ullllllOllilll, 



_L 



100 



200 



300 



Temperature °C. 



400 



500 



Figure 4. --TGA curves in air for guava with an initial sample of 10 mg. 



Small-scale burning tests also showed the treated fuel to be the least flammable. 

 The weight-loss curves are shown in figure 5. Maximum and average weight-loss rates 

 were lowest for the treated fuel. The rate of weight loss and rate of energy release 

 are presented in figures 6 and 7. The energy-release rate was computed by multiplying 

 weight loss and heat content. The relationships of the curves in the two figures are 

 not identical because the heat content of each fuel is different. This difference 

 accentuates the differences in burning rates of the three fuels. The assumption that 

 heat value remains constant during burning is not valid, but it probably can be used in 

 this comparison among treatments. 



Discussion 



The herbicide treatment apparently changed three parameters of the foliage: the 

 heat value decreased, ether extractives decreased, and ash content increased. These 

 changes reduce the flammability of the treated sample. 



The decreased heat value of the treated foliage is due to a reduction in the 

 amount of ether extractives and a reduction in the heat content of the extracted fuel. 

 The average heat contents of green and dead extracted fuel differ by only 44 cal./g., 

 or less than 0.6 percent. The heat content of the treated extracted fuel is about 150 

 cal./g. lower than the other two. This difference might be due to a more rapid decom- 

 position of the treated foliage, with accompanying reduction in heat content level. 

 The mass change associated with decomposition would also help to account for the high 

 ash content of the treated sample. 



5 



