Comparative Analysis of Stove Pyrolysis Performance of Donut Briquettes from Bus Wood Waste at Density Variations with and Without Used Oil Injection

Received: 24 October 2025 Revised: 7 January 2025 Accepted: 16 January 2026 Available online: 28 February 2026 This study evaluated the performance of a multilayer pyrolysis stove using donut briquettes from Bus Wood waste ( Melaleuca viridiflora) at a density of 3, 4, and 5 Mpa , with and without the injection of used oil. The briquettes are arranged vertically in an annular reactor and monitored with nine thermocouples. The test was carried out by measuring the internal temperature distribution and the Water Boiling Test (WBT). The results show a consistent radial temperature gradient; The highest temperature is detected at the inner edges of the briquettes (T3, T6, T9), reaching 650–800 ℃, while the outer edges are below 300–320 ℃. Increasing density from 3, 4, and 5 MPa results in a more stable high temperature and a longer pyrolysis duration. Injection of used oil increases the core temperature, albeit only slightly, at the useful energy of WBT, from 3.7 –4.2 to 3.8–4.3 MJ/h. The combination of briquettes with a density of 40 –50 bar and injection of used oil is considered the most prospective for the conversion of solid-liquid waste into household heat energy and biochar production in South Papua.