Effective microorganism

An effective microorganism (EM) refers to any of the predominantly anaerobic organisms blended in commercial agricultural amendments or for environmental applications such as for septic tanks. EM technology is purported to support sustainable practices in farming, improve composting operations, and to reduce environmental pollution.

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 effective microorganisms. 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.

Possible constituents

One trademarked product was originally 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.

Background

The concept of "friendly microorganisms" was developed by Professor Teruo Higa, from the University of the Ryukyus in Okinawa, Japan. He reported in the 1980s that a combination of approximately 80 different microorganisms is capable of positively influencing decomposing organic matter such that it reverts into a "life promoting" process. Higa invoked a "dominance principle" to explain the effects of his "Effective Microorganisms". He claimed that three groups of microorganisms exist: "positive microorganisms" (regeneration), "negative microorganisms" (decomposition, degeneration), "opportunist microorganisms". In every medium (soil, water, air, the human intestine), the ratio of "positive" and "negative" microorganisms is critical, since the opportunist microorganisms follow the trend to regeneration or degeneration. Therefore, Higa claimed that it is possible to positively influence the given media by supplementing with "positive" microorganisms.

Validation attempts

The concept has been challenged and no scientific studies support all of its 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.".

Parr and Higa mention soil pH, shading, soil temperature and flooding as factors affecting the interaction of EM with local microorganisms and with each other. The approach that Higa and Parr recommend is maintaining pH and soil temperature within conditions known to be detrimental to negative microorganisms as well as the addition of EM to tip the balance of positive and negative microorganisms in favor of the former.

They dismiss inoculants that include only a single microorganism as generally ineffective due to the uncertainty about the conditions in which a single microorganism would be effective. They cite the acknowledgment by the scientific community that multiple microorganisms (as in the case of Bokashi, invented and marketed by Higa) in coordination with good soil management practices positively influence plant growth and yield.

Various researchers have examined the use of EM in making organic fertilizers and investigated the effects of the fermented organic fertilizer on soil fertility and crop growth. The resulting effects on crop growth depend upon the organic fraction, direct effects of the introduced microorganisms, and indirect effects of microbially-synthesized metabolites (e.g., phytohormones and growth regulators).

The use of EM in the bokashi-intensive composting process for home kitchen waste has been in use in Christchurch, New Zealand for years, encouraged by the local city council and the regional council for people with little space.

Due to the fact that only very few studies exist which have used scientific methods to investigate additives based on EM, any claims made by manufacturers regarding long-term beneficial effects need to be treated with care.

Use to reduce environmental pollution

• In India, effective microorganisms have been used in an attempt to clean up some sewage-polluted lakes in Bangalore in 2015.
• After the Bangkok floods of 2011 EM was used to clean up polluted water.