Puzzle No. 17: When?

The Haber-Bosch process, which synthesises ammonia from atmospheric nitrogen and hydrogen under high temperature and pressure, reached industrial scale when BASF's Oppau plant in Germany went on-stream on 9 September 1913. Building on Fritz Haber's 1909 laboratory demonstration of catalytic ammonia synthesis, the chemical engineer Carl Bosch and the catalyst researcher Alwin Mittasch overcame formidable problems of high-pressure reactor design, gas purification, and durable iron-based catalysts to make mass production feasible. The plant initially produced on the order of 20 to 30 tonnes of ammonia per day, providing a cheap, inexhaustible source of fixed nitrogen that had previously depended on limited Chilean saltpeter deposits and guano. By breaking this natural bottleneck, the process made synthetic nitrogen fertiliser abundant, dramatically raising agricultural yields and enabling the global population to expand from roughly 1.6 billion in 1900 toward 8 billion. The technology also had a darker dimension, supplying nitrates for explosives that sustained Germany's war effort in the First World War. Haber received the 1918 Nobel Prize in Chemistry and Bosch shared the 1931 prize, and the process remains the foundation of the world's fertiliser industry.

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