Life cycle assessment of natural gas fuelled power plants based on chemical looping combustion technology

Highlights: • LCA comparison of different natural gas combustion processes including CLC. • First LCA study based on real data from operating CLC pilot units. • GCLC-CC does not add negative environmental impact to those in current natural gas combustion. • An improved Fe-based oxygen carrier seems the most promising material for GCLC-CC. -- Abstract: Among the different Carbon Capture and Storage (CCS) technologies being developed in the last decades, Chemical Looping Combustion (CLC) stands out since it allows inherent CO₂ capture. In the CLC process, there is a solid oxygen carrier circulating between two reactors in a cycle that allows providing the oxygen needed for combustion. In one of the reactors, named as fuel reactor, the fuel is introduced and combusted while the oxygen carrier reduction takes place. In the second reactor, named air reactor, the oxygen carrier is reoxidized in air. Different materials based on copper, nickel and iron oxides have been proposed as oxygen carriers for the CLC process. This work presents an environmental evaluation of the CLC process for natural gas based on Life Cycle Assessment (LCA). Five different oxygen carrier materials already tested in pilot plants were considered and the results compared to the conventional natural gas combustion in a gas turbine in a combined cycle without and with CO₂ capture using postcombustion capture with amines. In view of the results, lower impact of the CLC process compared to the base case is expected without and with CO₂ capture. The influence of several variables on the results was considered, such as temperature in the air reactor, lifetime of the oxygen carrier and possibility of recuperation of the depleted oxygen carrier. The nickel-based oxygen carriers were identified as the most adequate to be used in natural gas combustion. However, due to their toxicity, several analyses were also performed in order to identify improvements in the known oxygen carriers that can qualify them to replace nickel-based materials.