The work of testing and developing Rudolf Steiner's Agriculture Course of 1924 was an international enterprise coordinated by Pfeiffer at the Natural Science Section of the Goetheanum.

[5] Pfeiffer’s most influential book 'Bio-Dynamic Farming and Gardening' was published in 1938 simultaneously in at least five languages, English, German, Dutch, French, and Italian.

[9] As a result, Pfeiffer was invited to the U.S. in 1937 to work at the Hahnemann Medical College in Philadelphia[10] While in the U.S., he continued to consult with those interested in biodynamic farming and helped to form the Biodynamic Farming & Gardening Association in 1938. in 1940 he immigrated to the U.S. from Switzerland with his wife Adelheid, escaping the advance of German troops into France.

One of his students, Paul Keene, who worked and studied with Pfeiffer there for two years and shortly thereafter co-founded Walnut Acres, recalls: "he helped bring all of life together for us in a definite coherent pattern".

[12] His copper chloride sensitive crystallization theory brought him an honorary degree of Doctor of Medicine from Hahnemann Medical College and Hospital in Philadelphia in 1939.

[13] In 1961, at his home in Spring Valley, N.Y., he suffered from a series of heart attacks, lingering for several days, but ultimately was not given the proper medical care and died.

[14] A technical difficulty with the resulting compost, that it would not spread readily with the commonly used fertilizer spreader, could not be overcome and the project ultimately failed.