Special Focus: Advances in Hydrogen Production
R. KRAMER, Purdue University Northwest, Hammond, Indiana
Food is a valuable and essential resource, and its production is a critical function necessary to sustain life. A large portion of produced food internationally is wasted. An efficient way to minimize the loss of the value of this wasted food is to use it as a source of energy through biological green hydrogen (H2) production, an inherently environmentally friendly energy source. Nearly half of the fruit and vegetables produced each year are wasted. In the U.S., 30% of food is thrown away each year with a value of $48.3 B. Additionally, it is estimated that half of the water used to produce food is also wasted.
The author’s company has executed an agreement with energy companies to develop and commercialize a new process for biological H2 production from food waste. This new process uses food waste to biologically produce H2 that can be used as a sustainable energy source to produce electricity, chemical and industrial processes or as a transportation fuel. Green H2 is light, storable, transportable and energy-dense, producing no direct emissions of pollutants or greenhouse gases (GHGs). This process uses what would otherwise be wasted food to produce H2 biologically. As efforts to decarbonize the world progress, a clean energy medium will be needed, and H2 is well-placed to play this role.
In previous research sponsored by the U.S. Department of Energy (DOE), the process to produce H2 was optimized using a method based on bacteria from various types of organic waste. This new process has increased H2 production levels by at least a factor of 10. Due to its high H2 production capability and simplicity, this process now has the potential to provide an economically viable and technologically feasible means to produce H2 from biomass in the form of food waste.
This process requires minimal preprocessing of the food waste, and the operating conditions are greatly simplified during H2 production. The developed, optimized process significantly reduces production time, greatly reduces process complexity and decreases processing and operating requirements. Food waste is added to a low-pressure sealed reactor tank constructed from fiberglass or other conventional tank materials, operating slightly above atmospheric pressure, along with ordinary tap water and various inexpensive additives. Temperature is controlled with a simple thermostatically controlled heater, and pH is controlled using an inexpensive technical grade of sodium hydroxide.
The waste material slurry is agitated with a simple apparatus. The values of the optimized reactor operating conditions and the associated control scheme were developed using statistically based response surface methods and are critical to obtaining high productivity levels. It is envisioned that the system can be operated in a batch or continuous mode. The H2 produced at a facility using this process will be transported for sale to outside markets by truck or pipeline if such access is available. It could also produce electricity onsite and meet local process needs.
Biological H2 production offers a sustainable method to produce an environmentally friendly fuel with simultaneous waste minimization. By using this H2 in a fuel cell or a reciprocating engine-driven generator, the end products would be electricity, water and heat. H2 has potential as a versatile and clean fuel; however, technical and economic concerns with conventional H2 production and storage methods remain, potentially reducing its near-term viability.
Previously, H2 production from biomass has had limited application, but this process enhances the economic and technical viability of H2 production from food waste. The optimal operating conditions for the process were developed using multivariate analysis and statistical design of experiments.1,2 A central composite response surface design was employed with optimal factor selection determined by the Simplex method.3
Most H2 is produced within 24 hr after a 4 hr–6 hr latency period. Conventional processes for producing methane (CH4) from organic waste can require weeks of fermentation time, and previous efforts to produce H2 from organic waste required roughly double the time. The short production time will significantly increase productivity and value, allowing for an associated reduction in production facility size, complexity and cost. Additionally, methane has a Global Warming Potential (GWP) that is 28–36 compared to carbon dioxide (CO2), which has a GWP of 1, making CH4 a more active GHG.
Using organic wastes for the bio-production of H2 has the potential to generate cost-effective renewable energy and can reduce pollution. A key aspect of this technology involves operating the process at specific conditions that optimize H2 production instead of producing CH4 or ethanol (C2H6O). H2 produced from biomass sources represents only 8% of current H2 production. H2 produced from hydrocarbon sources (e.g., natural gas, petroleum, coal) represents 48%, but H2 produced by hydrocarbon refining is neither renewable nor carbon neutral.
The author's company has received three grants from the U.S. DOE and two grants from the Purdue Research Foundation to develop the science and technology that led to this process (FIG. 1). Two patents have been issued for this effort, and a third patent is in the final stages of approval. Over the next 9 mos, a scale-up test will be conducted. Based on test results, it is anticipated that construction could start on the first commercial prototype within 1 yr.H2T
1 Box, G. E. P., J. S. Hunter and W. G. Hunter, Statistics for experimenters: Design, innovation, and discovery, 2nd Ed., Wiley, 1978.
2 Box, G. E. P. and N. R. Draper, Empirical model building and response surfaces, 2nd Ed., Wiley Series, 1987.
3 Stat-Ease, “Design expert version 13.0.12,” 2022.
ROBERT A. KRAMER is a Professor of physics at Purdue University Northwest. Dr. Kramer is involved in developing research programs in energy utilization and efficiency, building energy efficiency, electric power, reliability, electric transmission and renewable energy sources, including H2 production from biomass, coal and biomass gasification to produce liquid transportation fuels and fertilizer. He is a certified Energy Manager, Demand Side Manager and Energy Auditor with the Association of Energy Engineers. Before employment at Purdue University Northwest, Dr. Kramer was the Chief Scientist for NiSource Energy Technologies.