Sulfuric acid is the most widely used chemical in the global economy by volume, reaching an estimated 230 million tonnes of production in 2025. Its use in minerals processing, metals recycling, battery manufacturing, phosphate fertiliser production, and water treatment industries is set to expand significantly to 2040, driven by the global energy transition, economic development, and increasing populations. Within minerals processing, sulfuric acid is a foundational, largely non substitutable reagent across the critical minerals sector, including in the production of nickel (via high-pressure acid leach), copper (via solvent extraction-electrowinning), lithium, rare earth elements, cobalt, uranium, zinc, and manganese. Reflecting this importance, sulfuric acid is often reported as a distinct operational cost category, and recent price volatility has already placed financial pressure on these producers. Currently, around 60 per cent of global sulfuric acid supply is sourced via de-sulfurisation processes during fossil fuel refining, required to meet fuel sulfur limits and local sulfur dioxide emissions regulations. The remaining 40 per cent is produced as a by-product of non-ferrous metal smelting and pyrite roasting. This by-product dependency on the fossil fuel industry gives rise to an emerging structural vulnerability for global sulfur and sulfuric acid supply, as the industry faces declining output in several regions due to a combination of heightened geopolitical tensions and tightening climate policy. Concerningly, this likely structural shift in supply – and the potential for shorter-term disruption – remains largely unaddressed within industrial chemical and critical mineral risk assessments and supply forecasting. Given this future supply uncertainty, this study investigates the scale of future sulfuric acid supply from alternative means, with specific emphasis on supply as a by-product of copper. The study uses the open-source Primary Exploration, Mining and Metal Supply Scenario (PEMMSS) model (Northey et al, 2023) to explore how much sulfuric acid could be supplied from the copper industry across a range of long-term scenarios. Unlike conventional by-product systems, sulfur grades are rarely reported, and sulfur is treated as a contaminant to be removed, rather than recovered, during mining and beneficiation stages. However, during high-temperature smelting, exothermic oxidation of sulfur in concentrates provides useful heat to the system, and the resulting sulfur dioxide gas is recovered to produce sulfuric acid. As a result, sulfur supply from the copper sector is governed not by ore grades or geological constraints but by concentrate compositions, mining-to-smelting trade networks, and smelter blending requirements and emissions limits. Modelling demonstrates that base metals industries could play a significant role in future sulfur supply markets, offsetting declining fossil derived sulfur supply, but the scale of this contribution is highly uncertain and dependent on future primary copper supply scenarios, smelter configurations and regulatory trajectories. Understanding these system dynamics becomes essential for ensuring sufficient sulfur supply and economic security. Given this, consumers of sulfuric acid in the critical minerals sector should seek to evaluate risks in their specific sulfuric acid supply chains, while also exploring opportunities to increase rates of sulfur recovery at smelters.