Agriculture Reference
In-Depth Information
Figure 38. Possible mechanism of biodegradation of NR-g-St in soil.
In addition, the oxirane groups of ENR can play an important role in enhancing the
biodegradability (Yew et al., 2006). In addition, the biodegradation of ENR cured for 20 min
was lower than that cured for 30 min due to the higher crosslinking in the sample. These
results agree with the swelling result. Samples of the NR-g-St were buried in soil and water
was sprayed onto the soil every 5 days. The weight of the samples was then measured every 7
days to establish the reduction in weight. The effect of the St content on degradation is shown
in Figure 37. It was found that the degradation increased with an increasing St content
because St is a biopolymer, which allows it to easily degrade naturally. It is obvious that the
rate of biodegradation of NR is low compared to St. The NR used in this experiment was
obtained from the latex of
Hevea brasiliensis,
which is a high molecular weight polymer of
cis
- 144
- polyisoprene as described above
.
It is apparent that the degradation of the NR-g-St
was greater with a higher St content as observed from both the weight loss and the color
change. The rate of degradation of the NR-g-St increased dramatically within 1 month.
However NR, which degrades in nature due to the action of specific microorganisms, is a
slow process and the growth of bacteria utilizing rubber, as their sole carbon source is also
slow. The possible mechanism of degradation of NR-g-St is represented in Figure 38. The
enzyme from microorganisms first destroy the chemical structure of the modified NR that
provide the short polymer chains, which are enough to permeate through the cell walls to be
utilized as carbon and energy sources, namely Depolymerization. After the end of
biodegradation, the by-product of biodegradation of the specimen is CO
2
and H
2
O, or
methane if the process is anaerobic, and also results in an increase in microbial biomass. The
different end by-product that occurs depends on the degradation pathways as shown in
Figure 38.
C
ONCLUSION
Between 40-70% of the nitrogen fertilizers applied to agriculture fields are lost from the
farmlands. This could be significantly reduced by the use of slow release nitrogen fertilizers.
Thus, the encapsulation technique, using a modified NR, may help to solve this problem.
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