From Excreted Manure to Deployable Circular Resources: Energy, Exergy, Nitrogen, and Climate Constraints on Livestock-Waste Biorefineries in Latin America

Regional assessments of livestock manure often treat excreted organic matter as available feedstock and methane volume as an unequivocal climate benefit. This study builds a four-level resource cascade (theoretical, collectable, recoverable, and deployment-constrained methane) for 20 Latin American countries from 2024 FAOSTAT inventories of cattle, pigs, and poultry with IPCC-consistent parameters, and evaluates each level across energy, exergy, nitrogen, and climate. The theoretical envelope of 73.88 × 109 m3 CH4 a−1 contracts by 82.1% to 13.22 recoverable and to a deployment corridor of 6.74 (95% interval 5.05–9.27); cattle fall from 85.4% of the theoretical to 32.5% of the recoverable resource, whereas poultry rises to 40.4%, a share conditional on controlling ammonia inhibition. Energy and climate hierarchies diverge: pigs hold 27.1% of recoverable methane yet deliver all positive manure-management mitigation (+29.14 Mt CO2eq a−1 at 5% leakage), and the central net balance including grid displacement is +43.96 Mt CO2eq a−1, with a production-based break-even leakage of 15.00%. On an exergy-equivalent basis (81.52 TWhx a−1), recovered nitrogen (25.26 TWhx; 3.77 Mt N a−1) exceeds useful heat (10.24 TWhx). Monte Carlo propagation (20,000 iterations) identifies cattle collectability as the dominant resource uncertainty (Spearman ρs=0.774) and digester leakage as the dominant climate uncertainty (ρs=−0.613; 99.4% probability of positive management mitigation). Intensification scenarios raise recoverable methane to 16.97–20.73 × 109 m3 a−1 by 2035, and published techno-economic evidence shows that profitability depends on scale, incentives, and coproducts. Abundance, recoverability, climate effectiveness, and economic viability are four distinct quantities that must be evaluated jointly.