*2.9. Biodegradation of the Samples*

In this test, the samples were landfilled beneath 10 cm gardening soil in glass vases. Some samples were placed into the soil before exposure to UV and the others were exposed to UV up to 500 h first, weighted and then landfilled horizontally. It should be noted that the samples were placed into an incubator at 40 ◦C. During the procedure, the water content was preserved at about 20%. The weight loss test evaluated the biodegradation rate of the samples. Every two weeks, the samples were removed from the soil, rinsed with distilled water and dried for 10 h at 70 ◦C; after weighing the samples, they were returned to the soil.

The rate of biodegradation (Q0 ) was calculated based on Equation (5) as follows:

$$\mathbf{Q}' = \frac{\mathbf{W}\_1 - \mathbf{W}\_2}{\mathbf{W}\_1} \times 100\tag{5}$$

In this respect, W<sup>1</sup> and W<sup>2</sup> (Equation (5)) are the weights of samples before and after landfilling at different time intervals, respectively.
