Effective microorganisms (EM) are various blends of common predominantly anaerobic microorganisms in a carbohydrate-rich liquid carrier substrate (molasses nutrient solution) of EM Research Organization, Inc., Many of the so-called "pit additives" used for improving the performance of sanitation systems, namely pit latrines, septic tanks and wastewater treatment plants, are also based on EM. Despite the claims made by manufacturers, available studies which have used scientific methods to investigate these additives have come to the conclusion that long-term beneficial effects are not proven. Studies have stated that effective microorganisms (EM-A, EM-Bokashi) show no effect on yield and soil microbiology in field experiments as bio-fertilizer in organic farming. Possible constituents One trademarked product was originally (c. 1985) marketed as EM-1 Microbial Inoculant. Such EM blends include: Lactic acid bacteria: Lactobacillus casei Photosynthetic bacteria: Rhodopseudomonas palustris Yeast: Saccharomyces cerevisiae Others: beneficial microorganisms that exist naturally in the environment may thrive in the mixture. In his presentational essay "EM: A Holistic Technology For Humankind", Higa states:"I developed a mixture of microbes, using the very common species found in all environments as extensively used in the food industry–namely Lactic Acid Bacteria, Photosynthetic Bacteria an[d] Yeasts (..) EM (..) was developed by accident (..)" Background The pseudoscientific concept of "friendly microorganisms" was developed by professor Teruo Higa, from the University of the Ryukyus in Okinawa, Japan. He stated in the 1980s that a combination of approximately 80 different microorganisms was capable of positively influencing decomposing organic matter such that it reverts into a "life-promoting" process. Higa invoked a "dominance principle" to explain the asserted effects of his "Effective Microorganisms". He claimed that three groups of microorganisms exist: "positive microorganisms" (regeneration), "negative microorganisms" (decomposition, degeneration), "opportunist microorganisms" (regeneration or degeneration). Higa stated that in every medium (soil, water, air, the human intestine), the ratio of "positive" and "negative" microorganisms was critical since the synergistic symbiotic microorganisms followed the trend to regeneration or degeneration. Therefore, he claimed that it was possible to positively influence the given media by supplementing with beneficial microorganisms. Validation The concept has been challenged and no scientific studies support its main claims. This was acknowledged by Higa in a 1994 paper co-authored by Higa and soil microbiologist James F Parr. They conclude "the main limitation...is the problem of reproducibility and lack of consistent results.". Various experimenters have examined the use of EM in making organic fertilizers and investigated the effects of the fermented organic