Ever wanted to produce nitrogen fertilizer like they did in the 1900s? In that case, you’re probably looking at the Birkeland-Eyde process, which was the first industrial-scale atmospheric nitrogen fixation process. It was eventually replaced by the Haber-Bosch and Ostwald processes. [Markus Bindhammer] covers the construction of a hobbyist-sized, fully automated reactor in this video.

It uses tungsten electrodes to produce the requisite arc, with a copper rod brazed onto both. The frame is made of aluminium profiles mounted on a polypropylene board, supporting the reaction vessel. Powering the whole contraption is a 24 VDC, 20 A power supply, which powers the flyback transformer for the high-voltage arc, as well as an air pump and smaller electronics, including the Arduino Uno board controlling the system.

The air is dried by silica gel before entering the reactor, with the airflow measured by a mass air flow sensor and the reaction temperature by a temperature sensor. This should give the MCU a full picture of the state of the reaction, with the airflow having to be sufficiently high relative to the arc to extract the maximum yield for this already very low-yield (single-digit %) process.

Usually, we are more interested in getting our nitrogen in liquid form. We’ve also looked at the Haber-Bosch method in the past.