PEER-REVIEWED ARTICLE bioresources.com Limhengha et al. (2023). “Ash as filler for latex foam,” BioResources 18(3), 5585-5598. 5585 Properties and Cost of Natural Rubber Latex Foam Using Biomass Ash Filler from Agarwood Pellets Suphatchakorn Limhengha, a, * Narong Chueangchayaphan, a Seppo Karrila, a Nasron Madmaeroh, a and Hassarutai Yangthong b The purpose of this work was to add value to biomass ash, which is a waste product from combustion of agarwood pellets as fuel. Ash was used as filler in accordance with the Bio-Circular-Green economy model to reduce the cost of manufacture of natural rubber latex foam (NRLF) produced with the Dunlop technique. The agarwood pellet biomass fuel was heated in an incinerator at 700 to 750 °C for 6 h to start the process. The mixture was then passed through a 120-mesh sieve after ball milling for 72 h. The next step involved dispersing 10% agarwood pellet biomass ash (APBA) at 0, 1.5, 2.5, 3.5, or 4.5 phr loadings in latex. This was followed by other actions such as visual inspection of the foaming and gelling stages. The influence of APBA loading on density, hardness, compression set and morphological properties of NRLF were investigated, and also the cost of production was estimated. The findings revealed that NRLF with 1.5 phr of APBA exhibited good physical properties, having a smooth surface and small foam cells. Moreover, the compression set properties of NRLF with 1.5 phr APBA comply with the Thai Industrial Product Standard (TIS 173-2529) for NRLF (Industrial Product Standard Act, 1986). Regarding the production costs, they were below those of filler- free NRLF by 0.03 USD/kg. DOI: 10.15376/biores.18.3.5585-5598 Keywords: Cost; Filler; Ash; Agarwood pellets; Natural rubber latex foam Contact information: a: Faculty of Science and Industrial Technology, Prince of Songkla University (PSU) Surat Thani Campus, Surat Thani 84000, Thailand; b: Specialized Center of Rubber and Polymer Materials in Agriculture and Industry (RPM), Department of Materials Science, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand; * Corresponding author: suphatchakorn.l@psu.ac.th INTRODUCTION Bio-Circular-Green economy (BCG) is a modern model that adjusts the economic system to become balanced and sustainable, which can be pursued through employing science, technology, and innovation to conduct capability enhancement in the sustainable competition. Particularly, circular economy can effectively help in solving various major global issues, as it is focused on utilizing available resources for the highest benefit, as well as making use of material waste in order not to make the waste become a burden to society and environment. At the same time the waste, such as the ash left over from processes generating industrial energy, can be turned into new products that subsequently create economic value. Agarwood Pellet Biomass Ash (APBA) is the residue from burning agarwood pellets, a form of biomass fuel. Limhengha et al. (2021) disclose that after the burning, about 3% of ash remains. Such residues from generating of industrial energy become