Microbial electromethanogenesis powered by curtailed renewable electricity

Renewable energy storage provides a severe challenge for transitioning to a renewable energy economy. Power-to-methane technology, including the microbial electromethanogenesis (MEM) platform, reduces CO2 with electricity to methane, an energy-dense fuel with vast storage capacity and existing infrastructure. To exploit the full potential of MEM technology, efficient conversion of intermittent, otherwise curtailed, renewable electricity is essential. Thus, microorganisms need to respond rapidly to fluctuations in electricity supply while converting electrical energy into chemical energy. Here, we demonstrate that methanogens in a continuous MEM system resume methanogenesis rapidly after current interruptions and convert intermittent electricity to methane with high Coulombic efficiency (CE). For over 4 months, MEM converted intermittent current to methane with 90% average CE. Further, MEM converted California curtailed solar electricity profiles with >96% CE. Therefore, MEM could play a decisive role in a future integrated energy grid by converting excess renewable power into the storable, high-density fuel methane.