###### Abstract
Footnote †: This article is an extended version of the awarded best paper published in the Resilient Materials 4 Life International Conference (RM4L2020), Cambridge, UK, 20-23 September 2021. Footnote †: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/)]([https://creativecommons.org/licenses/py/4.0/](https://creativecommons.org/licenses/py/4.0/))). Footnote †: This article is an extended version of the awarded best paper published in the Resilient Materials 4 Life International Conference (RM4L2020), Cambridge, UK, 20-23 September 2021. Recent studies have successfully proven the efficacy of numerous oils as promising, more sustainable alternatives for the design of encapsulated rejuvenators for aged asphalt, such as dense aromatic oil [5], waste cooking oil [6], mineral engine oil [7], sunflower oil [8] and, recently, bio-oil from liquefied agricultural biomass waste [9] and pyrolytic oil from waste tyres pyrolysis [10]. However, the polymers currently used for the encapsulation process, for example melamine-formaldehyde [6], can give rise to a potentially high environmental risk from the leaching of hazardous chemical compounds. Therefore, more sustainable capsules based on biopolymers are necessary to make this technology suitable for use in a new generation of asphalt pavements [11]. Sodium alginate is a biopolymer water-soluble polysaccharide extracted from the cell wall of various species of brown algae. Aspects such as great availability, low cost [12], high capacity to form a gel at low concentrations, nonoxicity, biocompatibility [13], and long-term stability [14] make sodium alginate a promising encapsulating material, reducing the negative environmental impact of typical polymers. Currently, the use of alginate as an encapsulating material of rejuvenators for asphalt has been explored by many authors. Experimental work was carried out by [PERSON] et al. in stone mastic asphalt [15] and a dense mixture [16]; the authors concluded that the addition of alginate-based capsules with sunflower oil and incorporated in a concentration of 0.5% per total weight of mixture significantly improved the healing capability of the respective mixtures. More currently, [PERSON] et al. [17] characterised alginate-biopolymer polynuclear capsules with virgin sunflower oil as a rejuvenator, proving that the strength of the capsules was influenced by the pore size of the calcium-alginate structure, and that the capsules could resist the temperature that is reached during asphalt mixing and compaction. Despite the urgent need to develop more sustainable and resilient construction materials, and the extensive diversity of renewable resource-based polymers for these purposes, the use of biomaterials in the civil engineering industry remains limited. Studies on the control and design variables for the correct synthesis of alginate-based capsules for asphalt self-healing purposes are still very limited in number. This study aims to synthesise and characterise polynuclear biopolymeric capsules for asphalt self-healing, where a sodium alginate biopolymer from the cell wall of brown algae _Laminaria hyperborea_ was used as the encapsulating material. Waste Cooking Oil was encapsulated in biopolymer as a potential rejuvenating agent to design more sustainable asphalt roads, because its content of light oil components is similar to that of bitumen. As an innovative approach, aspects such as (1) the adequate hydration of the biopolymer before encapsulation, (2) the control of the physical stability of the oil-in-water (O/W) emulsion, and (3) adequate height between the outgoing emulsion from the needle tip and the hardening solution are reported in this study. Figure 1: Concept of self-healing in asphalt using encapsulated rejuvenators.