Biological hydrogen is a short-lived by-product of various metabolic activities mediated by microorganisms. The production process harnesses nature, utilizing those microorganisms to convert organic matter into hydrogen — a clean, versatile fuel. This gas is central to a low-carbon future compatible with existing energy systems.
George Crabtree — a senior scientist at Argonne National Laboratory and the director of the Joint Center for Energy Storage Research — insists solely using renewables is not feasible and that an alternative like hydrogen is crucial for a carbon-free power grid. He states,
“Experts say that we could probably convert the grid 80% to renewable — that’s wind and solar — without having to deal with this long-duration storage problem … If you want to do the other 20%, you’re going to have to solve that problem of storage, you know, long-term storage for the grid, days in a row.”
As more countries turn to sustainable energy, biological hydrogen production (BHP) solidifies its role as a promising solution by offering long-term viability and a circular bioeconomy — a system in which waste reuse generates valuable products without draining resources. This article explores its mechanisms, advancements, economic implications and future perspectives.
The Mechanisms of Biological Hydrogen Production
BHP is characterized by the biochemical processes known as biophotolysis and biological fermentation. The latter is a promising emerging avenue of research. It converts various organic materials — crop residue, wood pulp, livestock manure, fallen leaves and municipal solid waste — into hydrogen gas.
In photofermentation, photosynthetic bacteria use light to convert volatile fatty acids and monosaccharides — simple sugars — into hydrogen. In contrast, dark fermentation converts organic matter into hydrogen and volatile fatty acids without light. It is defined by a high yield and a short processing time compared to photofermentation.
Typically, photofermentation yields 0.5 to 2 moles of hydrogen per mole of substrate. With dark fermentation, 3.8 moles of hydrogen per mole of monosaccharide is achievable. When combined to form a two-step process, these methods result in higher substrate conversion efficiency and shorter production times.
The Science Behind Biological Hydrogen Production
Microorganisms are fundamental to BHP. Their efficiency varies substantially depending on environmental conditions like pH, temperature, and substrate type.
The Types of Microorganisms Involved
In photolytic biological systems, microorganisms are key. One such microorganism is planktonic algae, also known as microalgae. It is one of the three primary types of algae. Various species can produce hydrogen via direct biophotolysis, using sunlight and the catalyst enzyme hydrogenase to split water into its base atoms.
Other essential microorganisms include various strains of Clostridium and Enterobacterium bacteria. Notable ones include C. butyricum — known for its high hydrogen yield regardless of substrate type. However, most strains produce spores, enabling survival even at high temperatures. This is a critical characteristic for producing hydrogen from organic waste.
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Sourcing Feedstocks for Biological Hydrogen Production
Most feedstocks are burned for heat, used in low-value applications or landfilled, releasing methane. According to the Environmental Protection Agency, this greenhouse gas is up to 36 times more potent than carbon dioxide at trapping heat over 100 years. This is of particular concern because landfills are the third-largest source of human-caused methane emissions in the United States.
For this reason, diverted organic waste is promising economically and sustainably. These feedstocks provide a cost-effective substrate source for BHP and contribute to eco-conscious waste management practices, facilitating a circular bioeconomy.
Jason Weller — the current Global Chief Sustainability Officer for JBS USA and the former Chief of the Natural Resources Conservation Service at the U.S. Department of Agriculture — is helping lead efforts to divert organic waste from landfills for biogas production. He states,
“One opportunity we’re particularly excited about is biogas, converting beef and poultry byproducts into renewable natural gas. Just recently, we announced a partnership with GreenGas USA to collect biogas from our food processing plant wastewater streams and purify that biogas into high-quality renewable natural gas. This builds on JBS’s existing methane capture capabilities while helping us improve local air and water quality and displace fossil fuel usage.”
He says this biogas conversion at three of their facilities in Utah, South Carolina and Nebraska will offset the annual greenhouse gas emissions equivalent of 60 million miles driven by a car, or 26 million pounds of coal burned.
“Repurposing waste streams into renewable energy is critical to helping us meet the challenges of climate change and food security. And this adds to our 25 other projects around the world to eliminate or capture organic waste methane emissions, including anaerobic-to-aerobic systems conversion and generating renewable electricity with biogas.”
Technological Approaches for Enhancing BHP
While BHP is still an emerging field, several technological advancements are helping stimulate adoption and accelerate research and development.
Microbial Pretreatment of Biomass
Chemical, microbial, physical and biological pretreatment methods exist to enhance the hydrolysis of biomass. Lignocellulosic biomass — dry plant matter composed of the polymers lignin, cellulose and hemicellulose — is typically used in BHP because it is among the most abundant organic materials on the planet. However, it is complex and difficult to work with.
Enzymes and microorganisms cannot break down lignocellulose because of its firm structure. Microbial pretreatment is a promising yet understudied avenue for BHP from lignocellulosic biomass. In one study, this method increased the yield by 312% compared with the control.
Nanoparticle Utilization
Studies indicate nanoparticles can significantly enhance production in dark and photofermentative processes because they have suitable chemical and physical properties. While the biological compatibility of metal particles is of concern — silver nanoparticles (AgNps) have known antimicrobial activity — the results are surprisingly promising.
Research from 2017 shows an AgNP concentration of 10 to 20 nanometers in a mixed culture dominated by C. butyricum enhances production rates. Improvements increase exponentially until tapering off at 200 nanometers. The maximum production rate is 2.48 moles of hydrogen per mole of glucose — a 67.6% improvement compared to the control’s 1.38 moles.
Bioreactor Design and Optimization
Bioreactor design plays a crucial role in maximizing BHP efficiency. Kinetic modeling is one such innovation — it translates the biological processes of substrate degradation and biological hydrogen production into mathematical equations to improve system performance. Continuous flow systems and optimized light supply strategies are other notable advancements.
To scale BHP, research and development teams must find a way to commercialize and industrialize bioreactors. Currently, they conduct most photofermentation projects at the laboratory scale, with capacities ranging from 100 milliliters to 10 liters. Pilot-scale systems designed for a combination of dark and photofermentation achieve a volume of 3,000 liters.
Economic and Environmental Implications of Production
The implications of industrialized BHP are far-reaching. It could reshape how countries think of sustainable energy production, waste management and circular economies.
Economic Viability
Extracting white hydrogen — naturally occurring hydrogen — typically costs $6 to $12 per kilogram on average. It would have to cost just $3 per kilogram to be financially feasible at scale. Ongoing efforts to make this approach more affordable are slow-going, making the fast-growing BHP field the ideal alternative.
While BHP is still in early development, it presents a potentially lower-cost alternative to steam reforming — today’s most cost-effective method, with a production cost of approximately $2.27 per unit of hydrogen. Moreover, organic waste is inexpensive and abundant, further enhancing economic feasibility.
Environmental Benefits
Hydrogen gas is inherently sustainable fuel — its sole by-product is water vapor. Utilization produces electricity without emitting greenhouse gases. Moreover, BHP contributes to carbon dioxide sequestration by converting organic waste into clean power rather than allowing it to decompose in landfills, further reducing emissions.
BHP is even more environmentally friendly than other hydrogen production methods. Conventional electrolysis requires an incredible amount of electricity to split water into hydrogen and oxygen. A typical system is just 50% to 60% efficient, requiring 50 kilowatt-hours of energy to produce 1 kilogram of hydrogen.
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Future Perspectives on Biological Hydrogen Scalability
Scaling BHP is possible, but it faces several financial, technical and regulatory challenges. Ongoing research into strain selection, process optimization and biomass effectiveness is essential for overcoming these hurdles. This clean power solution can only address global demand with collaborative efforts.
Dr. Alexander Krajete is the chief executive officer of Krajete GmbH and an academic at the University of California. He states,
“Climate laws are essential for steering us towards a sustainable future, but they needn’t always be perceived as financial burdens. Instead, the laws can present a unique opportunity for innovation and growth. Whether it’s electrification or hydrogen technology, there is a way to turn environmental challenges into profitable ventures. For example, in my own research, I’ve found that it’s possible to take the dangerous exhaust gas emissions from petrol and diesel vehicles and turn them into safe and useful fertilizers for crops.”
He believes that by investing in green technologies, businesses not only comply with regulations, but also gain a competitive edge in a rapidly evolving market.
“It is imperative to shift our perspective from viewing climate laws as obstacles to seeing them as catalysts for innovation. Harmony between environmental responsibility and economic viability is not just possible, it is essential.”
Initiating the Switch to Biological Hydrogen Production
Biological hydrogen production is an impressive development in the world of sustainability. By melding innovative engineering with microbial technology, it fits the bill of consistent clean electricity.
