Techno-economic and environmental assessment of renewable hydrogen import routes from overseas in 2030

Converting renewable electricity via water electrolysis into green hydrogen and hydrogen-based products will shape a global trade in power-to-x (PtX) products. The European Union's renewable hydrogen import target of 10 million tonnes by 2030 reflects the urgent need for PtX imports by sea to early high-demand countries like Germany. This study evaluates the cost efficiency and greenhouse gas (GHG) emissions of four hydrogen carrier ship import options considering a reconversion to H2 at the import terminal for a final delivery to offtakers via a H2 pipeline network in 2030. This includes ammonia, a liquid organic hydrogen carrier (LOHC) system based on benzyltoluene (BT) and a novel CO2/e-methane and CO2/e-methanol cycle, where CO2 is captured at the reconversion plant and then shipped back to the PtX production site in a nearly closed carbon loop. The GHG emission accounting includes well-to-wake emissions of the marine fuels and direct emissions of the carbon capture plant. Two GW-scale case studies reveal the impact of a short and long-distance route from Tunisia and Australia to Germany, whereas the specific PtX carriers are either fuelled by its PtX cargo as a renewable marine fuel or by conventional heavy fuel oil (HFO). Ammonia outperforms the other PtX routes, as the total hydrogen supply cost range between 5.07 and 7.69 for Australia (low: NH3 HFO, high: LOHC HFO) and 4.78-6.21 <euro> per kg H2 for Tunisia (low: NH3 HFO, high: CH4 HFO), respectively. The ammonia routes achieve thereby GHG intensities of 31 % and 86 % below the EU threshold of 3.4 kg CO2(e) per kg H2 for renewable hydrogen. LOHC though, unless switching to low-emission fuels, and the CO2/e-methanol cycle exceed the GHG threshold at shipping distances of 12,300 and 16,600 km. The hydrogen supply efficiencies vary between 57.9 and 78.8 % LHV (low: CH4 PtX-fuelled, high: NH3 HFO) with a PtX marine fuel consumption of up to 15 % LHV for the Australian methanol route, whereas high uncertainties remain for the ammonia and methanol reconversion plant effi- ciencies. The CO2 cyle enables a cost-efficient CO2 supply easing the near-term shortage of climate-neutral CO2 sources at the cost of high GHG emissions for long-distance routes.