Hydrogen production – Frontis Energy

With global population growth and the resulting increase in environmental stress, the need for sustainable wastewater treatment is becoming ever more urgent. Traditional methods focus on removing pollutants but often overlook the opportunity to recover valuable resources. One such resource is ammonium. This nitrogen-containing molecule promotes growth and is a key component of fertilizers. When mishandled, such as through over-fertilization, ammonium becomes one of the main contributors to nitrogen pollution.

A promising solution lies in bioelectrical systems. This umbrella term refers to innovative technologies that not only purify wastewater but also recover resources like ammonium. At the same time, bioelectrical systems generate clean energy such as electricity or biogas. The technology is based on galvanic cells, where the two cell chambers are often separated by a membrane. High-performance cation exchange membranes enable precise ion transport and system stability. The premium product among cation exchange membranes is Nafion, such as our Nafion 115 membrane.

At Frontis Energy, we have demonstrated that bioelectrochemical systems can remove ammonium from wastewater, offering an energy-efficient alternative to the energy-intensive Haber-Bosch process. To validate this concept, we developed microbiological electrolysis cells populated with microorganisms from oxygen-deprived marine sediments off the coast of Namibia. These sediments are naturally rich in ammonia and low in organic carbon, ideal conditions for microbes capable of anaerobic ammonium oxidation. For comparison, we also used conventional municipal wastewater to populate the electrodes.

Maintaining anoxic conditions was crucial to avoid nitrification, a process that transfers electrons directly to oxygen, bypassing the anode and resulting in energy loss and reduced hydrogen production. Instead, we regulated the anode potential between +150 mV and +550 mV, well below the redox potential required for water oxidation (+820 mV). This configuration enabled the oxidation of ammonium to nitrogen gas (N₂) at the anode, while hydrogen (H₂) or methane gas was produced at the cathode.

Central to this process is Nafion 115, a membrane made of perfluorosulfonic acid polymers (PFSA polymers). Its exceptional proton conductivity, chemical resistance, and mechanical robustness make it ideal for demanding wastewater environments. Nafion 115 acts like a selective gate, allowing ammonium ions (NH₄⁺) to migrate from the anode to the cathode while blocking competing ions and maintaining anoxic conditions. This selective transport, driven by electric field gradients and concentration differences, ensures efficient nutrient recovery and stable performance of the bioelectrical system.

A practical validation of this technology comes from our earlier report, in which researchers developed a two-chamber, anoxic bioelectrical reactor that continuously removed ammonium at a rate of about 5 g/m³/day. Their system converted over 97% of the ammonium directly into nitrogen gas. This transformation occurred without the formation of harmful byproducts like nitrite or NO_x gases. Particularly impressive was the energy consumption, just 0.13 kWh per kilogram of nitrogen removed. That is a 35-fold reduction compared to conventional aeration, which typically requires around 5 kWh/kg.

These results highlight the transformative potential of bioelectrical systems. As mentioned earlier, significant energy is used to remove nitrogen from wastewater, only to make it available again via the Haber-Bosch process, accounting for 1–2% of global energy consumption. Bioelectrical systems offer a circular alternative: by coupling ammonium oxidation with hydrogen production, wastewater treatment plants could become net energy producers. The generated hydrogen and biogas can be used directly for electricity generation and ultimately to reduce greenhouse gas emissions.

With the right biofilms, well-controlled electrode potentials, and robust membranes like Nafion 115, ammonium can serve as a clean, resource-efficient alternative to water electrolysis. This underscores the potential of bioelectrical systems to build a circular water economy, where waste is treated as a resource.

This technology reflects Frontis Energy’s commitment to promoting clean, efficient, and circular solutions that turn ecological challenges into sustainable opportunities.

Image: Wastewater treatment plant Bern

Hydrogen (H₂), produced using renewable energy, has emerged as a possible alternative to fossil fuel. This versatile molecule can serve as an energy carrier, an efficient storage solution, and a sustainable feedstock for transportation, chemical processing, and energy systems worldwide.

Unlike fossil fuels, hydrogen produces no harmful emissions when used. It can be generated using electrolyzers running on renewable energy and abundant water as feedstock. It then becomes a renewable and sustainable energy source, reducing reliance on depleting fossil fuel reserves, helping combat climate change. Consequently, hydrogen production has become a key priority on the political agenda of numerous countries.

However, the water used in electrolyzers must be ultrapure in order to protect the electrodes of electrolyzers from poisoning and avoid chloride oxidation to chlorine. Abundant seawater adds several challenges when directly fed to electrolyzer plants for hydrogen production, making highly pure water, specifically ultrapure water, an expensive necessity. Ultrapure water is produced in a series of steps, including pretreatment to remove suspended solids and desalination to eliminate salts, organics, and colloidal particles. Polishing techniques such as deionization, degasification, and ultraviolet treatment are then used to achieve the required quality. Among these processes, desalination is particularly critical for removing most impurities.

Reverse osmosis, especially seawater reverse osmosis, is a widely used desalination technology but has notable drawbacks, such as requiring high-pressure operation (high energy consumption), intensive pretreatment, and producing concentrated brine, which can harm marine ecosystems when discharged. Membrane distillation has gained attention as an alternative for producing high-quality water and supporting recovery applications. It operates at lower temperatures and has the ability to utilize waste heat.

Membrane distillation is a thermal separation process where a vapor pressure difference across a hydrophobic membrane causes liquid particles to phase change and pass through as gas. Operating at ambient pressure and utilizing low-temperature heat sources (<90 °C), membrane distillation offers significant advantages. However, research on membrane distillation as a viable alternative to reverse osmosis for ultrapure water production remains limited, particularly in areas such as module design and techno-economic analysis.

A group of researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, has explored the potential of membrane distillation as a cost- and energy-efficient alternative to reverse osmosis for producing ultrapure water for proton exchange membrane (PEM) electrolyzers. The findings were recently published in the Desalination Journal. They introduced membrane distillation as a possible alternative to reverse osmosis for ultrapure water production. But here is the twist: the membrane distillation system ingeniously taps into waste heat from a 5 MW proton exchange membrane electrolyzer, transforming what would typically be an efficiency liability into an asset for sustainability. So far, their results are impressive—membrane distillation not only produces exceptional distillate (<3 μS/cm) but does so at a cost ranging from €2.33 to €2.85 per ton of distillate, compared to reverse osmosis’s €2.80 to €5.51. Using membrane distillation, seawater desalination could be 50% or more cheaper.

Economic analyses highlight that membrane distillation’s cost-effectiveness is driven by its low electrical energy requirements and optimized short-channel module design. Its impressive energy efficiency, enabled using low-grade thermal energy, establishes membrane distillation as a highly versatile and environmentally friendly solution that aligns seamlessly with the vision for renewable hydrogen production. This study positions membrane distillation as more than just an alternative to reverse osmosis: it is a smarter and greener approach to ultrapure water production.

Their findings have the potential to reshape the industrial approach to ultrapure water production. By demonstrating an efficient use of waste heat and providing a more economical solution, it offers industries a pathway to lower operational costs while advancing sustainability. This aligns particularly well with sectors striving for greener operations, such as renewable hydrogen production and other energy-intensive applications. Moreover, the adoption of membrane distillation could catalyze innovation in system design and integration, encouraging industries to optimize processes and reduce dependence on traditional, energy-intensive methods. This shift can contribute to broader sustainability goals and improve the economic feasibility of renewable energy initiatives.

At Frontis Energy, we are committed to advancing sustainable and green energy solutions by embracing innovative technologies like membrane distillation, bringing us closer to a sustainable future.

Image: Pixabay

Tag: Hydrogen production

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