How agricultural residues are converted to hydrogen by microorganisms
In a world striving to move away from fossil fuels, hydrogen appears to be an ideal solution: when burned, it produces only water, and its energy density exceeds gasoline by 3 times. But where to get "green" hydrogen without CO₂ emissions? The answer hides in... waste.
Ukrainian scientists have proven that residues from corn and sunflower during bacterial fermentation release hydrogen in impressive volumes. This technology not only provides energy but also solves the problem of agricultural waste disposal!
Dark fermentation is a key biological process where anaerobic bacteria decompose organic matter without oxygen access. Unlike photosynthesis, light is not needed here, but the composition of raw materials is critically important:
The main reaction for hydrogen production:
Carbohydrates (cellulose, starch) are the main "fuel" for bacteria. The higher their concentration, the more active the reaction.
In 2016, the research group of N.B. Golub conducted a key experiment at the National Technical University "KPI", studying the effect of alkaline treatment on hydrogen yield from sunflower husks 2 .
Husks are crushed to fractions of 0.5-2 mm and treated with NaOH solutions (5%, 10%, 20%, 30%, 40%) for 1-3 hours.
Microbial association (Clostridium, Bacillus, Enterobacter) is added to the substrate in a 1:10 ratio. The process occurs in anaerobic reactors at 37°C and pH=5.5.
Hydrogen content in biogas is measured by gas chromatography. Volatile acid release is monitored by HPLC method.
Optimal conditions — 20% NaOH for 3 hours. This destroys lignin-cellulose bonds, increasing cellulose accessibility by 70%.
| Substrate | Cellulose Yield | Hydrogen Yield (ml/g) |
|---|---|---|
| Sunflower husks | 42% | 68.9 |
| Corn stalks | 48% | 72.3 |
| Wheat straw | 38% | 61.8 |
Corn stalks show the highest hydrogen yield, while wheat straw has the lowest efficiency among tested substrates.
The optimal value is 30:1. At C/N<20, bacteria synthesize proteins rather than hydrogen.
Terpenoids in sunflower husks reduce Clostridium activity by 15-20%. Alkaline pretreatment neutralizes them 1 .
Grinding to 0.5-2 mm increases surface area by 150%, accelerating fermentation.
| Reagent/Equipment | Purpose |
|---|---|
| Gas chromatograph | Determines volumetric fraction of hydrogen in biogas |
| NaOH solution (20%) | Lignin hydrolysis during pretreatment |
| Microbial association | Mixed culture (Clostridium + Enterobacter) |
| Anaerobic reactor | Ensures absence of oxygen |
| Phosphate buffer (pH 5.5) | Maintains optimal acidic environment |
Ukraine annually generates 25 million tons of agricultural waste. Their conversion to hydrogen will allow:
The technology is already being tested at pilot plants in Kyiv and Vinnytsia regions. According to the model developed by V.L. Chumak (NAU), the economic payback period of the project is 3-5 years 1 .
The technology could provide energy for heating a small village from processing waste of one agricultural complex.
Conclusion: Waste as Treasure
Research by Ukrainian scientists has proven: hydrogen from waste is not science fiction. The key to success is controlling the qualitative composition of raw materials and proper selection of microorganisms. Right now, the technology allows obtaining energy for heating a small village from processing waste of one agricultural complex. And in the future — it may become the basis of Ukraine's energy independence.