Global energy systems are in the midst of one of the largest changes in recent history. Reducing costs of renewable energy, electric vehicles, and an overarching social and cultural drive to reduce carbon emissions and enhance sustainability are driving rapid change from fossil-based energy sources to electricity-based systems. The oil and gas industry is particularly sensitive to this global change, and there is a notion that we are entering an era of “peak demand” for oil and hydrocarbons as a result of the global energy transition. Interestingly, estimates from energy agencies suggest that the global production of oil and hydrocarbons is set to increase during the energy transition, even in aggressive carbon drawdown scenarios that aim to avoid the worst of the damages from global climate change. However, it is clear that a “business as usual” approach will not be tractable for this industry as it experiences mounting pressure to defossilize. As a result, oil majors are investing heavily in carbon capture, carbon-free hydrogen, and bio-based feedstocks to reduce their greenhouse gas emissions while still meeting the rising demands for hydrocarbon products (chemicals, fuels, plastics, etc.). Membrane technologies will play a pivotal role in the success of these three approaches.
Membrane materials can selectively partition and separate chemicals and ions based on small (electro)chemical driving forces. Moreover, membranes can be packaged into high surface area modular devices, which are highly advantaged in distributed and footprint-limited energy production systems. Membranes are typically driven electrically, whether by mechanical pressure, or via the creation of an electrochemical potential gradient, and thus are easy to adapt to renewable energy system. This – in addition to the fundamentally good separation efficiency that a membrane offers – helps improve energy and carbon efficiency at global-scale refineries by providing incremental capacity additions to thermally-driven separations (ie membranes, because of their modular nature, provide the ability to fine tune refinery throughput when compared to the massive step change – and capital expense – that is associated with installing a new distillation column).
There is an urgent need to reduce carbon emissions associated with the oil and gas industry. A significant fraction of current oil emissions comes from distributed fuel combustion, while the rest of the carbon emissions are associated with the processing of the oil into its final products. Meanwhile, the majority of carbon emissions from natural gas processing occur in centralized combustion facilities (eg power plants, refineries etc). While the distributed carbon emissions are difficult to abate, the centralized carbon emissions from oil refineries and natural gas plants can and must be captured. Permselective gas separation membranes – such as the Polaris membrane from Membrane Technology Research – can enable the purification and recovery of CO2 from streams with higher CO2 partial pressures; examples include certain refinery flue gases and steam methane reforming systems. Lower CO2 concentrations may require the use of alternate technologies, such as liquid absorption, but here too membranes can help reduce capital costs via the use of hollow fiber membrane contactor systems.
The oil and gas industry utilizes significant amounts of hydrogen, and this hydrogen is produced via the reforming of natural gas, which produces CO2 as a byproduct. A notable alternative production method is via the electrolysis of water (so-called “green hydrogen”), which is essentially carbon-free. Indeed, there is a strong push – particularly from the US Department of Energy – to develop a global hydrogen economy. Green hydrogen is a central piece of this vision but is currently too costly. Conventional alkaline water electrolysis systems are mature, but suffer from hydrogen gas crossover within the electrolyzer, which reduces efficiencies and leads to safety concerns. Membrane-based systems, such as proton exchange membranes and anion exchange membranes, can improve electrolyzer efficiency and safety, thus reducing electrolyzer capital costs (one of the key cost drivers in the production of green hydrogen). Anion exchange membranes in particular capture the key advantages of alkaline electrolysis (namely the use of non-platinum-group metal catalysts), but currently the durability and ion conductivity of these membranes is insufficient for global-scale deployment. Beyond hydrogen generation, a global hydrogen economy will require distributed gas separation and purification equipment for hydrogen processing, which is another opportunity for modular and efficient gas separation membranes to make an impact.
Another way to reduce carbon emissions in the production of fuels, chemicals, and plastics is via the use of bio-derived feedstocks into conventional refining equipment. This is already happening around the world, albeit at small scales, via the blending or utilization of canola and vegetable oils into existing crude oil processing systems. These types of bio-derived oils are compatible with conventional reactor and separator equipment, but do not scale-up reasonably well. Next-generation solutions based on the conversion of woody biomass residue or bacterial cultures can potentially match the enormous scales of the oil industry. Converting these raw feedstocks into simple CxHy hydrocarbons is an energy- and carbon-intense process. Many bio-driven refinery concepts instead focus on upgrading these feedstocks to CxHyOz compounds. Water is created during this process and is often fully miscible with the new “bio crude” product. Both the rejection of water, and the separation of the CxHyOz compounds will be new challenges for oil refiners. Importantly, the separation of CxHyOz is especially difficult, as many of these compounds are not stable at the temperatures required to operate continuous atmospheric distillation. This is a new opportunity for membrane technologies to solve this class of difficult separations problems. Indeed, graphene oxide membranes are currently being scaled up to process water- and organic-laden black liquor streams at Kraft paper mills,, and there is potential for membranes such as these to address the separation of bio-crude and its derivatives in a bio-based oil refinery.
Overall, it is a time of tremendous change and uncertainty for the oil and gas industry, but also a time of opportunity for innovation and emphasis on sustainability. There is the expectation that we will continue to use key products from fossil fuels throughout the energy transition and beyond. Current commercial and emerging membrane technologies will enable a more sustainable and lower carbon production of these products – it is an exciting time to be involved with membranes, whether as a scientist, technologist, or entrepreneur in the membrane business!