**2. Bio binder's definition and resources**

#### **2.1. Definition**

Bio-binder is an eco-friendly asphalt binder alternative obtained from non-petroleum-based renewable resources, which should not rival any food material. From the definition, biobinder can be described as dark brown, high flow, organic liquids that are comprised mainly of highly oxygenated compounds [7–10].

#### **2.2. Bio-binder material sources**

A range of different vegetable oils has been investigated in recent times, through the application of scientific research and development, to determine their physical and chemical properties to study their applicability to be used as bio-binders in the pavement industry [11–13]. Bio-oils are produced from plant matter and residues, such as municipal wastes, agricultural crops, and byproducts from agricultural and forestry [8]. Other biomass sources include molasses and rice, sugar, potato starches and corn, gum resins and natural tree, vegetable oils and natural latex rubber, cellulose, lignin, waste oil of palm, peanut oil waste, coconut waste, potato starch, canola oil waste, dried sewerage effluent, and others.

Utilize this bio-binder can be a great potential as a modifier for asphalt binder because of similar chemical properties when compared with crude petroleum as shown in **Table 1**.

Currently, bio-binder is the second leading renewable energy in the nation after hydropower [14, 15].


**Table 1.** Typical characteristics of wood-based bio-oils.
