Volume 5, Issue 2 (2026) Knowing Where the Margin Is

Engineering seldom fails for want of a good idea. It fails at the margin — the last few millimetres of clearance, the last surviving ligament of a bad weld, the last dollar per tonne that separates a working technology from an unaffordable one. The seven papers in this issue were written independently, yet together they trace how such margins are calculated, eroded, and too often merely assumed.

Two papers ask whether a sound system can pay for itself. Siringoringo, Muthia and Purwanto model CCS retrofitted to the Punagaya 2×100 MW coal plant, capturing 98.72% of CO₂ but raising the levelised cost of electricity from 0.059 to 0.161 USD/kWh — and showing that storage distance, not capture chemistry, decides viability. Pesonagrata and Indianto reach a parallel conclusion for waste-to-energy at Pulogadung, where the cost falls from 0.79 to 0.09 USD/kWh only once capacity reaches 500 MW. Feasibility lies in tariffs, distances and scale as much as in the equipment.

Two others examine substitution at the level of the material. Kinasih and colleagues show that red palm oil does not simply replace petroleum plasticisers in SSBR/BR tread compounds but alters the vulcanisation chemistry around it. Gonera, Kalsum and Heraningsih find that their shrimp-shell chitosan membrane rejects iron and organic matter best at 1 bar, above which flux keeps rising while selectivity falls — a reminder that the optimum is an interior point.

Azzura, Syahrial and Kartika clear the 8 m benchmark for a 33-to-66 kV uprating by 70 mm, and say candidly that creep, heating and wind were not modelled. Buana and Winarto make the selection method itself auditable, ranking AISI 1040 first through declared, contestable weights. Fawwaz, Ulum, Soedarsono and Pratesa close the issue with an eye bolt that failed because every margin — specification, fabrication, coating access — had gone uncalculated.

Our thanks to the reviewers who gave their time, and to the authors who took their comments seriously. Submissions remain open at scholarhub.ui.ac.id/jmef.

Editor-in-Chief Journal of Materials Exploration and Findings Faculty of Engineering, Universitas Indonesia