**3. Materials and Methods**

Dried *S. bigelovii* (whole plant) were obtained from ISEAS farms in Abu Dhabi. Dried *P. dactylifera* leaves were also obtained from a farm in Abu Dhabi. All feedstock were shredded, milled and filtered through a sieve to obtain particle sizes below 0.5 mm. A sample of *S. bigelovii* and *P. dactylifera* were milled together in the ratio 1:1 for co-pyrolysis. Thermogravimetric analysis was conducted with a Netzch STA 449F3 STA449F3A-0625-M instrument and an aluminum crucible (Al2O3) under a Nitrogen atmosphere. The mass loss of biomass (*α*) was observed over a temperature program from 283 K to 1073 K. For each test, the mass loss (*α*) was performed in triplicates. The heating rate was kept constant at 10 K/min. Isothermal conditions were created at the start and end of the temperature program to eliminate noise. The heating rate was then varied at 15 K/min and 5 K/min respectively for both biomasses.

### *3.1. Isoconversional Methods for Kinetic Parameter Estimation-Theory*

The pyrolytic reaction of biomass converts biomass to char, oil and gases. The kinetics of the reaction can be described by defining a degree of conversion and using the Arrhenius equation. The isoconversional method is based on the fact that activation energy and pre-exponential are not constant throughout the decomposition but depend on the degree of conversion. Data points at the same conversion are gathered for different heating rates and each isoconversional curve is used to estimate the kinetic parameters at that conversion.

If *mi* is the initial mass of sample placed in the crucible, and *mf* is the mass of sample left after pyrolysis, a degree of conversion (*α*) for a given sample mass *m* at any temperature *T* during the process can be defined as:

$$\alpha = \frac{m\_i - m}{m\_i - m\_f} \tag{1}$$

From the Arrhenius equation,

$$k(T) = A\mathfrak{e}^{\frac{-\mathbb{E}}{RT}} \tag{2}$$

where *k* is the reaction rate constant (varies with temperature), *E* is the activation energy, *A* is the pre-exponential factor, *R* is the gas constant, and *T* is temperature in Kelvin.

The rate of decomposition can then be defined as a function of conversion and temperature:

$$\frac{d\alpha}{dt} = f(\alpha)k(T)$$

*f*(*α*) can be expressed as:

$$f(a) = (1 - a)^n,$$

where *n* is the reaction order.

Since the temperature program was run with a constant heating rate from 298 K to 1073 K, the temperature at any time t can be written as:

$$T = T\vec{\imath} + b\vec{\imath}$$

where *T* = initial temperature = 298 K and *b* is the constant heating rate.

The rate of decomposition can be written as:

$$\frac{d\alpha}{dt} = (1 - \alpha)^n A e^{\frac{-E}{kT}} \tag{3}$$
