Active Microorganisms (EM) are an innovative biotechnology that harnesses the power of beneficial microbes to support sustainable practices in agriculture, animal husbandry, environmental management and human hygiene.

Table of Contents

  1. Introduction
  2. What are Active Microorganisms (EM)
  3. Mechanisms of action of EM
  4. Areas of application of EM
  5. Advantages of EM
  6. Limitations and concerns
  7. Conclusions
  8. Bibliography

1. Introduction

Active or effective Microorganisms (EM) are a mixture of beneficial microbes used as an ecological technology to improve a variety of biological processes. The concept was developed in the 1980s by Japanese professor Teruo Higa, with the aim of utilizing groups of “friendly” microorganisms to promote the health of the environment and organisms [1] [2]. Unlike traditional chemical agents, EMs offer a biological approach: instead of killing microbes indiscriminately, they introduce beneficial microorganisms into the ecosystem. Thus, they are currently applied in many areas, from soil and crop improvement, to waste treatment, animal husbandry, and even cleaning and hygiene [1].

2. What are Active Microorganisms (EM)

EMs consist of a combination of different species of microorganisms that coexist harmoniously in liquid solution. They are mainly naturally occurring bacteria and fungi that are not pathogenic. In particular, a typical EM solution includes lactobacilli (lactic acid bacteria), yeasts, photosynthetic bacteria, actinomycetes and other fungi, at high density (in the order of hundreds of millions of cells per ml) [1]. These microorganisms are usually cultured by natural fermentation using molasses (sugarcane) as a substrate, in an acidic environment (pH ~3.5) resulting from the fermentation [1]. It is worth noting that both aerobic and anaerobic species are combined, which is unusual and is achieved thanks to their symbiotic action.

3. Mechanisms of action of EMs

EMs affect the environment and organisms through a variety of biological mechanisms. First, they act in competition with pathogenic microorganisms: beneficial microorganisms contained in the mixture multiply and occupy available resources and space, thus preventing the growth of harmful microbes through competitive exclusion phenomena [ 1]. In addition, many EM species produce antimicrobial substances (such as organic acids, enzymes, bacteriosins) and thus directly inhibit pathogenic organisms. For example, lactobacteria produce lactic acid that lowers pH and acts antiseptically, inhibiting sepsis and the growth of harmful bacteria on the substrate.

Antioxidant action

At the same time, it has been observed that some EM microorganisms secrete antioxidants that bind free radicals and reduce oxidative degradation of organic materials [1]. Overall, the synergy between different groups (e.g. photosynthetic bacteria with yeast and lactobacteria) creates a microbial ecosystem where the products of one species can be utilized by others, forming a favorable environment for processes beneficial to plants, animals and materials [1].

Another key mechanism of action of EM is to accelerate the decomposition of organic matter and enhance the nutrient cycle. The micro-organisms in the mixture rapidly break down organic substances (food residues, manure, plant material) into simpler forms, converting them into useful products such as humus, carbon dioxide, methane or available inorganic nutrients. [1]. This helps to improve soil fertility by releasing nutrients (nitrogen, phosphorus, etc.) that can be taken up by plants. In addition, certain EM species (e.g. phototrophic bacteria) can harness solar radiation and synthesise bioactive substances, providing energy and additional metabolic products that enhance the growth of plants and other micro-organisms. In summary, through degradation, competition and co-production of beneficial substances, Active Microorganisms create conditions that promote the stability and health of the microbial ecosystem for the benefit of the environment and higher organisms [1].

4. Areas of application of EM

4.1 Agriculture

Agriculture was the first and main area of application of EM technology. Active Microorganisms are used as biological soil conditioners and biofertilizers to improve soil fertility, enhance crop growth and reduce the need for chemical fertilizers and pesticides. Numerous studies have been reported in the international literature on the effects of EM on plants. Summary reviews show that in ~70% of cases EM formulations have a positive effect on plant growth and yield [3].

This is attributed to the improvement of soil microbial life: the application of EM increases the diversity and activity of beneficial microbes in the root zone, which improves nutrient availability to plants and suppresses soil phytopathogens [3]. Thus, in many cases, better root system development, greater leaf area and ultimately higher yields of agricultural products are observed, especially when EMs are used in combination with organic matter (compost, manure) instead of conventional fertilizers [3].

Practical applications in agriculture

In addition to general improvements, specific examples have been documented where the use of EM has significantly benefited crops. For example, in studies with bean plants under salinity, the addition of EM to the soil helped the plants to cope with salt stress – increased growth, better nutrient uptake (nitrogen, phosphorus) and accumulation of osmolytes that protect cells under salinity conditions were observed [4]. In another case, the application of EM to a degraded mountain pasture led to a remarkable vegetation recovery: plant biomass increased, soil organic carbon and nitrogen content improved and microbial activity was enhanced, demonstrating that EM can contribute to the regeneration of poor or eroded soils [5].

In addition, there is evidence that the presence of beneficial microbes can reduce the occurrence of certain plant diseases. Although EM is not a pesticide, improving soil microflora and producing substances such as lactic acid and other antimicrobials can inhibit pathogenic fungi (e.g. Fusarium) and nematodes that damage roots [3]. Thus, in a well “inoculated” soil with EM, plants tend to be healthier and more resilient, with fewer infestations. Overall, the use of EM in agriculture falls within the framework of sustainable/organic agriculture: it reduces chemical inputs, improves the physical properties of the soil (e.g. structure, water holding capacity) and promotes the concept of regenerative farming, where the soil itself improves itself through biological activity [3] [4] [5].

Active microorganisms (EM), what are they, what do they do and where are they used?

4.2 Livestock farming

Animal husbandry is another important sector where Active Microorganisms are applied, aiming to improve the health and productivity of animals and the management of their waste. At the nutritional level, EMs are used as probiotic supplements in animal feed or in the drinking water of animals. By adding beneficial microbes to the diet, the balance of the gut microflora is improved, which can lead to better digestive function and nutrient absorption.

Research in laying hens showed that adding EM to their ration and water significantly increased egg production – hens receiving EM produced a higher number and heavier eggs, and showed an improved feed conversion ratio (less feed consumption per egg produced) compared to groups without EM [6]. Similarly, cases of improved growth rate in broilers and pigs have been reported when EM formulations were incorporated into their diets as an alternative to antibiotic starters.

Applications in the animal environment

In addition, EMs are also used in the farming environment and in animal waste management. In practice, this means that EM solutions are sprayed on stables, cages, floors and manure piles. The presence of beneficial microbes in these areas helps to reduce odours and flies associated with the decomposition of faeces. EMs accelerate the fermentation of manure in both aerobic and anaerobic ways, producing fewer odorous substances (such as ammonia and sulphur gases) and suppressing the septic bacteria responsible for the odour [1].

As a result, the rearing areas are kept healthier, with a reduced load of pathogens and insects. At the same time, the biostabilisation of manure with EM leads to a final product (compost or organic fertiliser) of higher quality for agricultural use. It has been reported that EM-fermented manure contains more organic matter, nitrogen in organic form and essential amino acids, making it a rich biological fertilizer for plants [1] [6]. Thus, in animal husbandry, EM technology contributes in two ways: on the one hand, it improves animal performance and health through probiotic action, and on the other hand, it solves environmental problems of the farm (odour, waste pollution) by converting waste into a useful product.

4.3 Waste and water treatment

One of the most important applications of EM is the treatment of liquid and solid waste, as well as the restoration of water quality in ecosystems. Active Microorganisms are used in biological wastewater treatment systems, in eutrophic lakes and rivers, but also in landfills or organic waste composting plants.

In the wastewater sector, it has been shown that the addition of EM can enhance biological treatment and reduce the pollutant load of the effluent. In a study of industrial wastewater treatment of sugar industry wastewater, the application of EM led to a significant reduction in chemical and biological oxygen demand (COD and BOD) of water – it was observed that more than 90% of organic load (COD) and more than 70% of total nitrogen were removed after bioreactor treatment with EM microorganisms [7].

At the same time, nitrate and phosphate concentrations in treated wastewater have been reduced, which helps to reduce eutrophication when this water is discharged into the environment [7]. In addition to wastewater plants, EMs have been used experimentally in natural water ecosystems: for example, in ponds or reservoirs where there was a problem of odour and high organic loads, ‘sludge pellets’ enriched with EMs were dropped. These micro-organisms, when released into the sediment and water, helped to degrade accumulated organic matter and odorous substances (e.g. volatile fatty acids), improving the odour and clarity of the water within a few weeks. In general, EM water bioremediation aims to restore microbial balance: beneficial bacteria consume excess nutrients (which feed the algae) and compete with pathogenic aquatic microorganisms, ultimately resulting in cleaner water and healthier aquatic ecosystems [1].

Organic waste treatment

In terms of solid organic waste treatment, EMs are often used in composting – i.e. the biological degradation of organic materials (such as food waste, agricultural residues, manure) to produce compost. By adding an active microbial inoculum to the waste pile, the aim is to accelerate and optimise fermentation. Several studies have examined whether EMs improve the outcome of composting. In several cases, it has been reported that the final compost from piles sprayed with EM shows higher maturity and quality – e.g. higher content of stabilized organic matter (humus), higher concentrations of available nutrients (nitrogen, potassium) and lower presence of pathogens [1].

EMs can reduce emissions of unpleasant gases (such as ammonia) during composting, because they promote faster fixation of nitrogen in the microbial biomass or material, instead of it evaporating as ammonia. This leads to fewer odours and at the same time limits nitrogen loss, resulting in a more nutrient-rich compost [1]. Significantly, in home composting experiments, the addition of EM resulted in compost reaching maturity faster and with better fertility characteristics compared to compost without EM [8].

Of course, efficiency may vary depending on the type of waste and conditions (e.g. carbon/nitrogen ratio, humidity, aeration), but the use of EM in waste treatment is considered a simple and low-cost practice that can improve both the speed and quality of composting. Finally, EMs are also being applied to landfills or garbage bins to control odours – spraying EM solutions onto accumulated organic waste significantly reduces odour and insects as decomposition processes are shifted to more fermentative (non-smelly) pathways [1].

4.4 Health and hygiene

EM applications are also expanding into the health and hygiene sectors, although here they are still mainly at the research and pilot testing level. In the health sector, the use of EMs as probiotics for humans has been investigated, as well as their potential antimicrobial activity against certain pathogens. Since many of the bacteria in the mixture (such as Lactobacillus and yeasts) are common probiotics found in fermented foods or dietary supplements, it has been suggested that consumption of EM solutions could improve gut microflora and immune response. However, at present the evidence in this area is mainly anecdotal and more clinical research is needed.

Nevertheless, some in vitro experimental studies have shown interesting results: for example, researchers tested the effect of EM solution on cysts of the Acanthamoeba parasite (an amoeba pathogen that can cause serious eye and brain infections) and observed that EM treatment reduced the viability of cysts and caused morphological changes in them [9]. This suggests that EMs contain microbial substances that may act against certain resistant pathogenic stages. Also, in the veterinary field, faster wound healing has been reported in animals when cleaned with EM solutions, probably due to the reduction of infections by the competing beneficial bacteria. However, the use of EM for medical purposes is still in its infancy and is not part of conventional therapy.

Hygiene and cleanliness

In the field of hygiene and cleanliness, the EM philosophy has led to the development of alternative bio-cleaning methods. Instead of strong chemical disinfectants that indiscriminately kill microbes (and sometimes favour the development of resistant strains), the use of ‘probiotic cleaners’ is proposed: i.e. cleaning products containing live non-pathogenic micro-organisms (such as bacilli and lactobacilli of EM). These, when applied to surfaces, colonise the surface microbial ecosystem with beneficial microbes, which then compete with the pathogens and prevent their re-establishment [10].

In a hospital setting, where the issue of resistant microbes and hospital-acquired infections is critical, trials have been conducted with such probiotic cleaners. In a multicentre study in hospitals in Italy, the introduction of daily cleaning of floors and surfaces with a solution containing Bacillus bacterial spores (similar to those of EM) resulted in an approximately 90% reduction in the load of dangerous pathogenic bacteria (such as methicillin-resistant Staphylococcus aureus, Pseudomonas, etc.) compared to cleaning with conventional disinfectants [10]. In addition, a reduction in the rate of hospital-acquired infections was recorded in the wards where the probiotic cleaning system was applied [10]. Although these results need further confirmation, they suggest that the “clean with good microbes” strategy may be a complementary or alternative to conventional disinfection, especially in areas where absolute sterility is not feasible. EM cleaning products for household use are already commercially available, promising clean surfaces without killing all microbes but with the establishment of ‘friendly’ microorganisms that maintain pathogen control. Thus, the application of EM in hygiene incorporates the modern understanding that complete sterilisation of living spaces is not necessarily beneficial, while the existence of a balanced microflora may better protect against dangerous microbes.

4.5 Domestic use

Active Microorganisms have also found a place in simple everyday applications in the home, helping families to adopt greener practices. A popular home use is the composting of household waste using the “Bokashi” method, which is based on EMs. In this method, organic kitchen scraps (peelings, food, etc.) are placed in an airtight bin and each layer of scraps is sprinkled with an EM-infused bran. The micro-organisms carry out anaerobic fermentation of the waste instead of rotting. Thus, within 10-14 days, the residues are fermented without rotting or smelling bad [8].

The resulting product is not fully compost, but a fermented material that can then be buried in the soil or added to a composting pile to complete its degradation. This practice allows household biowaste to be recycled even in apartments, without the odour or insect problems normally associated with composting in small spaces. With the Bokashi system, families can reduce their garbage and produce a nutrient-rich liquid extract (the “Bokashi tea”) that is diluted and used as a liquid fertilizer for plants. Studies have shown that Bokashi fermentation converts food waste into a material with high organic carbon and available nitrogen suitable for soil enrichment [8].

Use in cleaning

In addition, EMs are used in domestic cleaning and maintenance for the physical management of odours and microbes. For example, there are EM formulations that can be sprayed on waste bins, drains or toilets to reduce unpleasant odours. Beneficial microorganisms accelerate the breakdown of organic residues in pipes and manholes, preventing rot and odours. In aquariums or garden ponds, small doses of EM can help control algae and maintain clean water by harnessing the action of photosynthetic bacteria that consume algal nutrients. Even in laundry, some users add porous ceramic shells impregnated with EM in the belief that they improve water quality and act as chemical-free cleaners (although these results are mostly anecdotal). Finally, household cleaners with probiotics (along the lines of hospital probiotic cleaning) are available for kitchen, bathroom surfaces, etc., offering cleanliness with the power of “good microbes” instead of strong disinfectants. Although these products are not ubiquitous, they represent a new trend in household practices, where Active Microorganisms are harnessed to create a healthy microbial environment in the home, friendly to humans and the environment [10].

5. Advantages of EM

Active Microorganisms technology has a number of important advantages that make it attractive as an alternative in various fields.

  1. It is an environmentally friendly solution: EMs are natural organisms and their use reduces the need for chemical fertilizers, pesticides, antibiotics or disinfectants, thus helping to reduce chemical pollution of soil and water [1].
  2. EMs are safe for humans, animals and plants – they consist of non-pathogenic species that are either neutral or beneficial, so their application does not pose any risks of toxicity or residues in food. This makes them suitable for organic farming and livestock production, where non-harmful substances compatible with the ecological cycle are required [1].
  3. They have a multidimensional effect: a single EM mixture can simultaneously improve soil fertility, promote plant growth, reduce manure odours, contribute to wastewater treatment and act as a surface cleaner. This multifunctionality means that EMs can be integrated into integrated management systems (e.g. agri-business, where animal waste with EMs is returned to plants as fertiliser), saving resources.
  4. The implementation of EM is relatively simple and cost-effective. EM formulations are available in concentrated form and can be activated/modified in situ by the user with cheap materials (molasses, water), producing large quantities of final product. Their use (spraying, mixing in soil or food, etc.) does not require complex equipment.
  5. Finally, an indirect advantage is that EMs are aligned with the idea of a circular economy: they use by-products (e.g. organic waste) and convert them into useful resources (fertilizer, clean water), enhancing the sustainability of ecosystems and human activities [1].

6. Limitations and concerns

Despite the promising advantages, the use of Active Microorganisms is accompanied by certain limitations and concerns, especially with regard to the scientific documentation of their effectiveness under all conditions. The results of EMs are not always stable or reproducible. Cases have been documented where the application of EM has not led to improvements and the benefits have been zero or negligible. Typically, in a four-year experiment in an organic field in Switzerland, researchers found that EM did not improve crop yields or soil microbiological indicators compared to non-EM controls – any small effects were attributed to the nutrient substrate (molasses) accompanying the formulation rather than to the microorganisms themselves [11]. This study showed that under the specific climatic-territorial conditions (temperate climate of Central Europe), EM were not ‘effective’ and did not produce measurable benefits in the medium term.

One reason for this variability is that the action of EMs is strongly dependent on environmental conditions. These micro-organisms are only effective if they find in their environment the right conditions to grow and prevail: sufficient organic material as food, humidity, appropriate pH and temperature [12]. In poor soils without organic matter or in very cold/dry climates, EMs may fail to establish and simply perish without effect. In contrast, in warm humid conditions with abundant organic matter (such as in tropical environments where they first appeared), they are more likely to have a positive effect [12].

Then it is important to get it right: EMs are living organisms, so if they are stored or used incorrectly (e.g. at very high temperatures or in combination with chemicals that kill them), they will have no effect. For the user, this implies that the instructions (dissolution, temperature, time of use after activation, etc.) must be strictly followed, otherwise the result is not guaranteed.

7. Conclusions

As presented, EMs consist of a diverse mix of living microorganisms that work together to improve the microbial ecosystem of soil, water or even a surface, competing with harmful microbes and enhancing natural processes of nutrient degradation and recycling. Their use has shown impressive results in many cases: increased agricultural yields, healthier animals, cleaner water and efficient composting of waste, while reducing pollution and odours. In addition, they offer an environmentally and human-friendly approach, in line with the principles of ecological balance.

However, the adoption of EMs should be done with knowledge of their potential limitations. They are not a ‘miracle solution’ for every situation – their effectiveness varies and depends on the circumstances of implementation. Science recognises the benefits, but also underlines the need for further research and careful evaluation. Active Micro-organisms, when used correctly and in appropriate environments, can be a valuable ally in a range of activities, making them more sustainable and efficient. With continued study and improvement, EM technology has the potential to make a significant contribution to the transition towards practices that respect and cooperate with nature, harnessing the tiny but powerful forces of the microbial world.

8. Bibliography

[1] Safwat, S.M. & Matta, M.E. (2021). environmental applications of Effective Microorganisms: a review of current knowledge and recommendations for future directions. Journal of Engineering and Applied Science, 68:48. DOI: 10.1186/s44147-021-00049-1.
[2] Higa, T. (1991) Effective microorganisms: a biotechnology for mankind. In J.F. Parr, S.B. Hornick & C.E. Whitman (eds.), Proceedings of the First International Conference on Kyusei Nature Farming, USDA, Washington, DC, pp. 8-14.
[3] Olle, M. & Williams, I.H. (2013). Effective microorganisms and their influence on vegetable production – a review. Journal of Horticultural Science & Biotechnology, 88(4): 380-386. DOI: 10.1080/14620316.2013.11512979.
[4] Talaat, N.B., Ghoniem, A.E., Abdelhamid, M.T. & Shawky, B.T. (2015). Effective microorganisms improve growth performance, alter nutrients acquisition and induce compatible solutes accumulation in common bean (Phaseolus vulgaris L.) plants subjected to salinity stress. Plant Growth Regulation, 75(1): 281-295. DOI: 10.1007/s10725-014-9948-5.
[5] Li, J., Wei, J., Shao, X., Yan, X. & Liu, K. (2024). effective microorganisms input efficiently improves the vegetation and microbial community of degraded alpine grassland. frontiers in microbiology, 15: e1330149. DOI: 10.3389/fmicb.2023.1330149.
[6] Atsbeha, A.T. & Hailu, T.G. (2021). The Impact of Effective Microorganisms (EM) on Egg Quality and Laying Performance of Chickens. International Journal of Food Science, 2021: 8895717. DOI: 10.1155/2021/8895717.
[7] Embaby, A.A., El-Shahawy, M., Abd-Allah, M.A. & Dawoud, I.A. (2010). Application of effective microorganisms in treatment of wastewater of beet sugar factory at Bilqas, Dakahlia Governorate, Egypt. Journal of Environmental Sciences, 39: 151-158.
[8] Van Fan, Y., Lee, C.T., Klemeš, J.J., Chua, L.S., Sarmidi, M.R. & Leow, C.W. (2018). Evaluation of Effective Microorganisms on home scale organic waste composting. Journal of Environmental Management, 216: 41-48. DOI: 10.1016/j.jenvman.2017.04.019.
[9] Sampaotong, T., Lek-Uthai, U., Roongruangchai, J. & Roongruangchai, K. (2016). Viability and morphological changes of Acanthamoeba spp. cysts after treatment with Effective Microorganisms (EM)Journal of Parasitic Diseases, 40(2): 369-373. DOI: 10.1007/s12639-014-0511-x.
[10] Tarricone, R., Rognoni, C., Arnoldo, L., Mazzacane, S. & Caselli, E. (2020). A Probiotic-Based Sanitation System for the Reduction of Healthcare Associated Infections and Antimicrobial Resistances: a Budget Impact Analysis. Pathogens, 9(6): 502. DOI: 10.3390/pathogens9060502.
[11] Mayer, J., Scheid, S., Widmer, F., Fließbach, A. & Oberholzer, H.R. (2010). How effective are “Effective microorganisms (EM)”? Results from a field study in temperate climate. Applied Soil Ecology, 46(2): 230-239. DOI: 10.1016/j.apsoil.2010.08.007.
[12] Hidalgo, D., Corona, F. & Martín-Marroquín, J. (2022). manure biostabilization by effective microorganisms as a way to improve its agronomic value Biomass Conversion and Biorefinery, 12: 4649-4664. DOI: 10.1007/s13399-022-02428-x.

Founder of Zeolife.gr. Architect and civil engineer, in full engagement with natural zeolite and Greek aluminous diatomite from December 2013.

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