EcoSolutions Inc., a manufacturer of bio-based plastics, operates a combined heat and power (CHP) plant that provides both electricity and steam to their production facility. The CHP plant also supplies excess electricity to the local grid. During a Life Cycle Assessment (LCA) following ISO 14044, the LCA practitioner, Anya Sharma, faces the challenge of allocating the environmental burdens associated with the CHP plant between the bio-plastic production, the electricity supplied to the grid, and the steam used internally. Anya has considered several approaches, including allocating based on the market value of electricity versus steam, the energy content of the electricity and steam, and the mass of fuel input to each process. She also considered simply ignoring the allocation problem altogether. Given the requirements of ISO 14044, which allocation method should Anya prioritize, assuming system expansion is not feasible due to data limitations and modeling complexity?