How hydrogen could clean up the chemicals industry

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Imagine if you put everything in the universe on your bathroom scale. 75 percent of that weight comes from the smallest atom on the periodic table: hydrogen. How is such a light, tiny atom responsible for so much of everything around us? Hydrogenโ€™s high bonding potential makes it the key building block of many items that surround us, from soap and shampoo, to paints and building materials and the plastics and packaging we use daily. Each of these manufactured materials are chemicals, built up from combinations of hydrogen, carbon, and other elements to create useful products for society.

Chemical plants produce these products; they take hydrogen and combine it using the correct amounts, temperatures, pressures, and conditions to make the desired molecules. In the United States today, we produce 10 million metric tons of hydrogen each year โ€” the same mass of natural gas used in Iowa in 2022 โ€” and over 90 percent of it is used as feedstock for chemical products. As we look ahead in the energy transition, we see the demand for petrochemicals, including plastics, continuing to rise, resulting in further hydrogen demand and production around the world.

In 2019, hydrogen production for chemicals accounted for approximately 130 million tons of CO2 equivalent emissions โ€” almost half of the chemical sector emissions in the United States. Today, most hydrogen is derived from natural gas (methane) and is converted through the steam methane reforming reaction to generate hydrogen, with significant CO2 emissions and heat requirements. ย Thankfully, there are cleaner, lower emissions pathways to producing hydrogen, such as converting water into hydrogen from renewable energy. By replacing the feedstock in the manufacturing process with this lower-emission hydrogen, the overall emissions associated with chemical production can be reduced. Further emissions reductions can be achieved by addressing process heat โ€” through direct electrification, efficiency improvements and some uses of hydrogen as fuel in high temperature applications.

When we talk about chemicals, we often refer to โ€œprimaryโ€ chemicals as the few chemicals that are made and then converted into virtually every chemical product that exists in society. This list of chemicals can vary, but for this article we will discuss five primary chemicals: ammonia, methanol, ethylene, propylene, and benzene. Since hydrogen is a fundamental building block of many chemicals and can be used as an energy source in the high temperature processes found in these facilities, its production emissions play a critical role in the chemicals sector. To reduce emissions from the chemicals sector, we need to reduce emissions from hydrogen production itself, address process heat requirements and sourcing, and address emissions associated with feedstock extraction and processing.

Hydrogen Production and Uses in Chemical Plants

Hydrogen can be used in the manufacturing process for primary chemicals in two main ways: as a feedstock for the chemical reaction, or as an alternative process heat source instead of using natural gas.

This section explores the potential impacts of replacing a hydrogen feedstock with lower emission hydrogen and replacing natural gas heat with hydrogen firing.

Scenario 1: Existing hydrogen feedstock is replaced with lower emissions hydrogen

Clean hydrogen, such as electrolytic hydrogen, which uses renewable electricity and water as a feedstock to generate hydrogen can be swapped into the chemical manufacturing process to reduce emissions. This is being pursued with the Star e-methanol project, which received funding from the US Department of Energyโ€™s (DOE) Industrial Demonstrations Program to produce methanol from electrolytic hydrogen and CO2 and reduce emissions by more than 90 percent compared to conventional marine fuel.

If all feedstock hydrogen for primary chemicals (ammonia, methanol, ethylene, propylene and benzene) is replaced with renewable, electrolytic hydrogen the total emissions from the production of these chemicals could be reduced by up to 32 percent, with the bulk of this reduction in emissions coming from the hydrogen and hydrogen-derived molecules (ammonia and methanol). High-value chemicals (ethylene, propylene, benzene), use very little feedstock hydrogen and therefore see small benefits from a feedstock source switch.

Scenario 2: Existing natural gas heat is replaced with lower emissions hydrogen

Today, most heat input in chemical plants comes from the combustion of natural gas, like gas stoves in some household kitchens. When natural gas is combusted, it produces CO2 and heat. However, when hydrogen is combusted, it produces water vapor which has much less impact on the environment. Heaters in chemical plants can be replaced with electrified options (heat pumps, direct electrical heating), rendered more efficient, or sometimes retrofitted to accept hydrogen as a heat source rather than natural gas. Although this can be costly, it can also have huge impacts on reducing emissions from these facilities.

Some heaters in chemical plants face high near-term barriers to economic electrification due to the high temperatures required for the reaction, and for these, hydrogen is a powerful solution for emissions reduction. For example, the DOE Industrial Demonstrations Program awarded a project to reduce emissions from an olefins (ethylene and propylene) producer by retrofitting natural gas-fired equipment to use hydrogen to avoid 2.5 million metric tons of carbon emissions per year. If all the natural gas currently being used to produce heat at chemical plants was replaced by either direct electrification with renewables or electrolytic hydrogen made using renewable energy, the total emissions for the chemicals sector could be reduced by up to 28 percent. (RMI CI model). High-value chemicals (ethylene, propylene, benzene) see a potential 33 percent reduction in emissions, and hydrogen-based chemicals (ammonia and methanol) see a potential 21 percent reduction.

Replacing existing natural gas derived hydrogen production with less emissions intensive production has the potential for significant emissions reductions when used either as a feedstock or a process heat source. Depending on the manufacturing process for each chemical, higher emissions reductions are seen from a feedstock switch or a fuel switch. We must have a clear understanding of each manufacturing process to determine where hydrogen should be deployed as an emissions reduction lever to have the highest impact.

Benefits and Barriers

To reduce emissions from the chemicals sector, we must pull on multiple threads โ€” feedstock extraction and processing emissions reduction opportunities, efficiency improvements, direct electrification of processes and heat, process heat fuel switching, alternative process development, and new material discovery. When it comes to hydrogen, there are two key factors that make hydrogen an advantageous decarbonization lever for chemicals manufacturing: 1) It is a critical component of chemicals production as a core building block of countless chemicals 2) It is already being widely used in the chemicals industry and therefore has more opportunity to expand its role in emissions reduction. For chemicals where hydrogen is a key reagent, swapping offsite grey hydrogen for cleaner hydrogen can reduce emissions without any on-site modifications or capital expenditure. Further, sites that use hydrogen are already familiar with appropriate handling procedures, safety risks, and leak mitigation. Although clean hydrogen accounts for only about 1 percent of total global hydrogen production today, there is policy momentum to encourage its production. Thus, the availability of low-emission (blue and green) hydrogen is projected to increase to 38Mt by 2030, and at a lower price.

Currently, one key barrier to transitioning to clean hydrogen is the cost; hydrogen produced via electrolysis from water is more expensive than hydrogen produced via steam methane reforming from natural gas. Measures to reduce the cost of producing clean hydrogen and create a market for lower-emissions chemicals can help drive increased flows of green hydrogen to the market. These include the availability of renewable energy, advancement of electrolysis technology, coupling supply with demand, policy incentives, and increased industry demand. Additionally, the upstream natural gas leakage rates for SMR hydrogen with carbon capture can erase all GHG benefits from the installation of carbon capture if they are high and left unmitigated. Methane certification programs exist to measure and provide solutions to reduce methane leakage to ensure a lower emissions product is produced.

Making the change to cleaner hydrogen should be weighed against other decarbonization opportunities such as direct electrification and enhanced energy efficiency. Continued focus on innovation and alternative production routes for chemicals will help accelerate emissions reductions even further as new technologies and production routes are discovered with lower energy demands.

Utilization of hydrogen produced through lower emissions routes, via feedstock or process heat, shows incredible promise for reducing greenhouse gas emissions from the chemicals sector. To maximize emissions reductions, it is critical to identify the most efficient applications within the chemicals sector and support initiatives/policies that encourage the widespread deployment of clean hydrogen.

Authors:ย Tania Evans, Catherine Huyett,ย ย Joseph Fallurin,ย ย Tessa Weiss

This article was originally published by the RMI and is republished with permission through theย Creative Commons CC BY-SA 4.0 license.

Disclaimer: The articles expressed in this publication are those of the authors. They do not purport to reflect the opinions or views of Green Building Africa or our staff. The designations employed in this publication and the presentation of material therein do not imply the expression of any opinion whatsoever on the part Green Building Africa concerning the legal status of any country, area or territory or of its authorities.

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