Abstract This paper maps where and how much primary biomass from dedicated lignocellulosic crops can be produced under stringent sustainability guardrails, and how unit costs evolve as production scales up. We assemble a harmonized 5 arc minutes global grid of marginal lands screened for food security and environmental constraints, and couple two complementary methods. First, we construct regional and global capacity–cost envelopes by spatially ranking grid cells by farm-gate unit cost and cumulatively aggregating potential. This descriptive step identifies the least-cost clusters and provides transparent orders of magnitude for planning. Second, treating each pixel as a decision unit (exploitation), we estimate parsimonious cubic total-cost functions with region and country effects to recover average(AC) and marginal (MC) cost schedules and the efficient scale Q∗ , thereby deriving micro-founded supply behavior. Results show strong spatial heterogeneity and a systematic divergence between “capacity leaders” and “cost leaders.” Capacity–cost envelopes highlight extensive low-cost clusters in Sub-Saharan Africa, Europe & Central Asia (with concentration in Central Asia), and North America, with additional but smaller clusters in East Asia & Pacific, Latin America & Caribbean, the Middle East & North Africa, and South Asia. Pixel-level econometrics reveals that: (i) in Europe & Central Asia and in Latin America & Caribbean, MC typically remains below AC over wide ranges, indicating persistent economies of scale; (ii) in North America, AC curves are U-shaped with steep MC rises beyond Q∗ , signaling pronounced diseconomies at high output; (iii) in South Asia, most crops exhibit declining AC across the observed range (strong economies), while Miscanthus shows a mild U-shape; (iv) in Sub-Saharan Africa, Miscanthus displays exceptionally flat and low AC at small efficient scales, whereas other crops face early diseconomies; and (v) in East Asia & Pacific, only MC is identified, serving as the regional supply curve. Across regions, Miscanthus and Switchgrass often anchor the lower cost envelope, while Eucalyptus, Poplar, and Willow tend to occupy higher cost segments. Therefore, policy and investment decisions should be sequenced: use capacity–cost envelopes for strategic targeting and portfolio sizing, then rely on pixel-level AC/MC and Q∗ to guide fine-grained siting, contracting, and risk-aware scaling