A BIM-Based Life-Cycle Carbon Emission Accounting and Optimization Method for Hydraulic Engineering Projects

To address the disconnection between carbon emission accounting and building information modeling (BIM), inconsistent accounting boundaries, the lack of systematic carbon optimization methods, and the absence of construction-stage tracking in hydraulic engineering projects, a BIM-based life-cycle carbon emission accounting and optimization method is proposed. A BIM carbon information model is established based on the IFC standard, with a three-level “component-material-emission factor” mapping that enables automatic extraction of material quantities and automatic updating upon design changes. An emission factor database covering four stages (material production, construction, operation and maintenance, demolition and recycling) is constructed and a life-cycle carbon accounting model with itemized, traceable calculation sheets is developed. Three-dimensional heat maps are used to visualize component-level carbon distribution. Taking life-cycle carbon emission and total project cost as objectives, the NSGA-II algorithm is employed to derive the carbon-cost Pareto front under structural safety, schedule and cost constraints. IoT-based real-time data enables dynamic carbon tracking during construction. A case study of a concrete gravity dam shows that the total life-cycle emission is 0.3945 MtCO2, with the material production stage accounting for 84.1% and cement production accounting for 72.4% of the total, making it the largest emission source. Substituting slag or fly-ash cement reduces cement-related emissions by 24.7%-28.8% (equivalent to 21.3%-24.8% of the material production stage). Rail-road combined transport and waterway-road combined transport cut aggregate transport emissions by 61.9% and 57.1%, respectively. NSGA-II yields 15 Pareto-optimal solutions; within the near-zero-cost interval, emissions are reduced by 19.8% at only 0.2% additional cost (unit abatement cost about 26 CNY/t), while the deep-decarbonization scenario reduces emissions by 33.5% with the marginal abatement cost rising to 559 CNY/t, revealing an increasing marginal abatement cost pattern. Dynamic tracking corrects the overrun deviation from +8.2% to +3.5%. The proposed method provides systematic technical support for low-carbon construction of hydraulic engineering projects.