Life cycle optimisation for negative emission technologies in electricity generation

•This research aims to quantify the contribution of NETs in reducing carbon emissions with minimum cost to achieve net-zero emissions.•Life cycle optimisation study provides an optimal solution by optimising the system's life cycle impacts.•DACCS shows a different economic performance when different comparison basis is used.•Minimum carbon emission is achievable with minimum system cost.•The resulting NETs portfolios provide a new benchmark for selecting an optimal carbon removal approach.