**4.1 Life cycle impact assessment (LCIA) on GHGs emission in the production of mature rubber tree from immature rubber stage**

The total GHGs emission value in maintaining the healthy growth of one immature rubber tree for a year for this study is 1.08 kgCO2eq as shown in **Figure 2** and **Table 3**. The highest contributor which represented 51.6% from the total GHGs emission value in maintaining the healthy growth of one immature rubber tree for a year is the emission of nitrous oxide from the usage of ammonium sulfate at 5.60E−01 kgCO2eq (**Figure 2**).

While the second highest contributor to the total GHGs emission value in maintaining the healthy growth of one immature rubber tree for a year is ammonium production with the percentage of 22.4%. Meanwhile, glyphosate production was recorded as the third highest contribution at 17.7% (**Figure 2**). The remaining three processes are considered as insignificant contributors towards the total value of GHGs emission to maintain the healthy growth of one immature rubber tree for a year (**Figure 2**).

**Figure 2** obviously showed that the reduction in the usage of ammonium sulfate and glyphosate will definitely reduce the total GHGs emission value in maintaining the healthy growth of one immature rubber tree for a year. This can be achieved through the reduction in the immaturity rubber stage period and through incorporating the manual weeding method in weed management.

The GHGs emission value in maintaining the healthy growth of one immature rubber tree for 6 years duration during the immature rubber stage is 6.51 kgCO2eq and this represent 14.6% from the total value of GHGs emission for the cultivation of one rubber tree from cradle to gate of 44.68 kgCO2eq.

The GHGs emission in maintaining the healthy growth of immature rubber trees in Malaysia per year which based on 0.379 million hectares of immature rubber area in Malaysia at the average stand of 410 rubber trees per hectare and with 51.8% of this area is fertilized at the recommended dosage is summarized in **Table 2**.

Based on **Table 2**, as compared to the Malaysian 2011 GHGs emission of 290,230 GgCO2eq in [30], the GHGs emission value from the perspective to maintain the healthy growth of immature rubber trees in Malaysia for 6 years, immature rubber stage and 1 year average for immature rubber stage is considered as insignificant.

The GHGs emission value of 524.69 GgCO2eq with duration of 6 years for immature rubber stage in maintaining the healthy growth of immature rubber trees in Malaysia is very low and represent only 3.3% from the 2011 Malaysian agricultural sector GHGs emission of 15775.3 GgCO2eq (**Table 2**). The GHGs emission value of 87.45 GgCO2eq based on the average 1 year for immature rubber stage is considered

### *Climate Change and Agriculture*

as insignificant as compared to the GHGs emissions value from Malaysian agricultural sector in 2011 (**Table 2**).

**Table 3** shows the list of GHGs emission and its corresponding values in contributing to the total GHGs emission value in maintaining the healthy growth of one immature rubber tree for a year.
