Renewable curtailment for energetic reasons in Brazil increased from 4.4 TWh in 2024 to 20.2 TWh in 2025, while the national freight system remains dependent on diesel-fuelled road haulage. This work evaluates the contribution of mini distributed generation (mini-DG) to energetic curtailment and provides a techno-economic and geospatial assessment of a decentralized green hydrogen production and refuelling network for heavy-duty road transport in Southeast Brazil. Semi-hourly ONS curtailment data (2024–2025) were combined with the ANEEL mini-DG registry, PVGIS irradiance, EPE self-consumption factors and DNIT road and traffic data over a 1,850-hexagon grid. Curtailment was reallocated to mini-DG units according to their injected surplus and then distributed homogeneously across cells, after which PEM electrolyzers and hydrogen refuelling stations (HRS) were sized per cell under five operating strategies. Mini-DG could account for about 3% of national and up to 17% of Southeast/Midwest energetic curtailment. Curtailment-driven configurations yielded a levelized cost of hydrogen (LCOH) of 26.44–50.92 $/kg, dominated by low utilization rates (12–23%) and electrolyzer CAPEX, whereas a grid-extended full-load operation reached 10.57 $/kg at the cost of 29.7 TWh of additional demand. The resulting hydrogen could cover 39–56% of the reported internal Southeast freight distance and the full demand under extended operation, avoiding up to 6.82 MtCO2/year. Feasibility nonetheless remains conditional on complementary revenue, namely oxygen valorisation and the PHBC fiscal credit programme.