Carbon dioxide emission rates for conventional and synthetic fuels

With rising concern about the increasing atmospheric concentration of CO₂ and its potential impact on global climate, there have been suggestions that the CO₂ emission rates be considered in selecting among fuel-producing technologies. Many previous comparisons have been inadequately drawn. We discuss criteria for carefully drawn comparisons and compute CO₂ emission rates in kgC/10⁹ joules for a variety of conventional or synthetic fuel processes. Although the total CO₂ release per joule is on the order of 1.8 (±0.2) times as much for burning liquid fuels from coal as for liquid fuels from crude oil, useful comparisons among synthetic fuel processes are not easy and the results are subject to changes in boundary conditions of resource availability, plant location, environmental requirements, output slate desired, economics, etc.