# Petroleum Sector-Driven Roadmap for Future Hydrogen Economy
## 2 Hydrogen Technology: How to Produce, Transport, and Store
Based on that, CCS appears to be a vital part of the hydrogen economy, so its realization will lead to a superior focus on CCS in conjunction with hydrogen [27]. Because CCS is essential for blue hydrogen, an analysis on its feasibility in deferent regions  
Figure 1: The blue hydrogen process flow: SMR and ATR. Figure 2: The green hydrogen schematic. is necessary [14]. The most important geological storage options are depleted oil and gas reservoirs, and offshore and onshore deep saline formation, where CO\({}_{2}\) can be used for enhanced oil and gas recovery (EOR), as well as coal mines, where CO\({}_{2}\) can be used for enhanced coal bed methane recovery. Alternative CCS and CCU (i.e., carbon capture and utilization) processes are illustrated in Figure 3[28; 29]. A comprehensive feasibility study conducted in 2016-2017 concluded that CO\({}_{2}\) capture is technically feasible at three selected industrial sites in Norway: Norem's cement factory in Brevik owned by Heidelberg Cement, Yara's ammonia factory in Porsgrunn, and the Fortum Oslo Varme's energy recovery plant in Oslo [30; 31]. As the projects were based on transportation by ship, the storage site could also be accessible for other European countries. A successful demonstration could also be inspiring for the GCC countries. From a techno-economic perspective, 50-70% CO\({}_{2}\) capture with around 0.135-0.146 Euros/m\({}^{3}\) levelled production cost of H\({}_{2}\) could be seen in the SMR technique without capturing flue gas (which means about 0.037-0.060 Euros/kg CO\({}_{2}\) tax reduction), while these amounts for ATR technology are 90%, 0.143 Euros/m\({}^{3}\), and 0.048 Euros/kg, respectively [14]. A new SMR scenario with capture from flue gas or hydrogen as combustion fuel for heating offers up to 90% CO\({}_{2}\) capture and 0.165 Euros/m\({}^{3}\) levelled cost of H\({}_{2}\)[24]. After hydrogen production, its transport via the existing natural gas infrastructure and/or a new hydrogen grid can be considered as two feasible scenarios. For the first option, different chemical properties between CH\({}_{4}\) and H\({}_{2}\), the regulation and safety, the integrity of the pipelines, and the availability of capacity are among the important challenges to be addressed. Other important parameters are number of compression stations, characteristics of measurement instruments, replacement of critical components, and degradation of existing pipelines/grid. For instance, a feasible implementation strategy can determine the impurities and process parameters based on the largest consumers' need, and then on-site purification and compression can be implemented if needed [14]. More studies are required to determine which parts of the existing infrastructure are applicable to the hydrogen transport and which ones must be replaced. The related social concerns and economic issues are discussed in the next section of the paper. At the same time, one major key to wholly developing a hydrogen economy is safe, compact, light and cost-efficient hydrogen storage [32]. Storage of hydrogen is needed to compensate for a mismatch between supply and demand on timescales from minutes to seasons in a way that flexibility and security in delivery and purchase can be ensured [14]. Figure 3: The CCUS schematic diagram. Various hydrogen storage methods and their challenges are presented and briefly discussed by several researchers, for example in [33; 34]. For the blue hydrogen case, it will be vital to determine the cumulative demand flexibility and the related storage volume/pattern, which will determine the selection of the storage method [14]. The most important identified methods for blue hydrogen storage are [35]: (a) Line packing (daily storage in the gas network), (b) tanks for compressed gas (daily small-scale storage in cylinders), (c) liquid hydrogen (daily small- and large-scale storage in tanks of LNG), (d) salt caverns (daily and seasonal large-scale storage), and (e) depleted gas fields (seasonal very large-scale storage).