Responses: How effective are Garbage Enzymes?
by Bhavani Prakash
I’m very happy to note that the article on “How to Make and Use Garbage Enzymes” has stirred a lot of discussion and this has been an opportunity to clarify where the science lies.
I had endorsed Garbage Enzymes enthusiastically as I have personally heard gardeners speak of the positively about the results. These are from 1) Ground-Up Initiative at Bottle Tree Park, Singapore 2) Kampung Senang Charity Foundation in the Community Garden at Tampines, Singapore 3) Bandar Harapan Organic Farm in Malaysia and 4) Nanyang Technological University Community Medicinal Herb Garden (which I discovered after writing the article).
The sum and substance of the feedback is that Garbage Enzymes (the term itself may be a misnomer) can be used as a homemade vinegar for non-edible cleaning purposes. The efficacy of Garbage Enzymes as a fertiliser or pesticide or an air purifier is not yet verified by scientific research. Even less obvious is its ability to lessen greenhouse gases. There are varying views on its contribution to waste management – in the local context, is composting a better way to manage waste, instead of adding molasses? Or can this be considered as one additional way to manage waste that would otherwise go to the incinerator?
There are two detailed responses to this and we thank both the contributors for their time to clarify the science behind Garbage Enzymes.
The first response is from Dr Vinisha Khemani Kanjilal, who is a Singapore based scientist and runs science based educational programs for children at Green Dots
I read your piece on Garbage Enzymes (GE), and note a few things here:
- The process you describe without doubt is a natural fermentation/anaerobic oxidation whose products are alcohol (incomplete/partial fermentation) and acetic acid (complete fermentation). These are enzymatically performed by natural and mixed microbial cultures in the starting preparation (fruit dregs and vegetable trimmings).
- Fermentation has been used for time immemorial/centuries (and even before the science was clarified by Louis Pasteur) to produce wines and vinegars, sakes and arrack and other variants of these all over the world. Some native populations have preferred pure starting materials like rice bran or grapes, some have been clever to figure out anything with naturally combustible carbohydrates can be converted to sugars and be directed towards production of ethanol and/or acetic acid (aka vinegar). See Wikipedia on Fermentation.
- Thus GEs are not a new discovery by Dr. Rosukon Poompanvong or anyone else in recent times for that matter. Pubmed is a publically accessible repository of all original research published in peer reviewed journals – there is no mention of any work when a search is done on her. Also, the FAO link on her lists many of her achievements. However couldn’t find any English language literature on the internet of any credibility to all the GE uses you’ve listed out on the blog. She is perhaps to be credited for heightening the awareness around reuse of kitchen waste (traditionally discarded in Thailand?) towards production of vinegar via a method that can be simply executed by almost anybody.
- To the best of my knowledge neither the enzymes/biological catalysts from microbes (mostly proteins) nor the microbes themselves would survive the change in pH that happens during the course of a complete fermentation and none of the fruit based enzymes that I’m aware of viz: papain from papaya, bromelain from pineapple, etc. would function in the final and extreme acidic environment of approx.2 that would result when acetic acid is produced as in the GE method described.
- Thus the terminology GE is a bad one (even if but as a colloquial name) for the process described to recycle organic waste by fermentation (in no way attributable to EWTT), but just to be cautious in what it mistakenly connotes.
- In the scope of 3R principles even while trying to be vegetarian and all consuming there will be some organic waste generated. Whether that kitchen waste goes into composting or more pure vermiculture methods, to generate vinegar at home as a cleaner and by reproducing the process described or otherwise is immaterial. They are all effective as recycling methods and would have little to no difference in their pros and cons with respect to global warming, save the fact that an incomplete fermentation (as for example when yeast cultures are used to produce ethanol) actually produces a greenhouse gas as a byproduct viz: carbondioxide (CO2).
- In the same vein, directed waste management practices (See Wikipedia link on Anaerobic Digestion) that produce methane (an alternative source of energy and potent greenhouse gas) if not channelized towards use are effectively adding to global warming.
- Would not make any claims to use of vinegar whether produced by the GE process or otherwise as a fertilizer or pesticide at any concentration. There is no evidence for this whatsoever.
- Sometimes soils are more alkaline than required by plants to grow healthily…so diluted vinegar might help set the pH towards a more neutral or favourable setting…also just perhaps aid in soil loosening. This could be seen as largely beneficial but remains to be tested scientifically and would still not qualify GE as a natural fertlilizer.
- Likewise extreme environments would destroy most microbes so acetic acid like any other corrosive acid would kill some bugs on contact and if used carefully might be usable as a pesticide/insecticide. This potential benefit remains to be tested however in dose dependent studies.
In short would agree with John Cussman that the science presented and claims made on GE are flawed and somewhere effective microbial cultures that would be enzymatically rich (but which I’ve not done any homework on) are being confused with enzymatic byproducts.
Vinegar in Singapore is cheap especially the 1 SGD/- per litre bottles produced from rice bran. Green Dots uses these in numerous experiments. The cheap vinegar will be effective in glass cleaning, toilet bowls, stain removal on floors, etc just like housewives have known the deodorizing properties of sodium bicarbonate for a long time.
Since I recycle my organic kitchen waste into soups, food for my dog, vermiculture, composting in order of priority – have not felt a need to experiment with vinegar production at home – especially not at the cost of purchasing sugar or honey! However do think it makes a fabulously interesting experiment for children to do and learn from and test some hypotheses inhouse.
Kitchen waste recycled vis vermiculture or composting will undoubtedly have a lower carbon footprint than being deployed with sugar (its manufacture has its own carbon footprint) to produce vinegar and anaerobic gases including CO2 by yeast!
Here’s a link to some recent articles (Article 1 and 2) for producing enzymes and methane from organic waste. Pure cultures of specific fungi have also been used in fermentations to produce antibiotics.
Have known of a scientist from the National Chemical Laboratory (NCL) who was tinkering with more scientific composting methods and using lemon peels for effective pH management 20+ years ago. So also Gandhi’s nature cure ashram in Uruli Kanchan has for last several decades been recycling organic wastes. Such methods that make local and contextual sense have been around for a long time in the world
GE is definitely not well researched at present, so little technical information can be found about it. More testing or literature reviews would be required to further support my preliminary views, and this account is by no means exhaustive and conclusive.
The purpose of molasses or brown sugar is to provide “simple” carbon source or energy for the microorganisms to first feed and grow. When growth is sizeable, the microbes may then turn their attention to the additional food source (the waste materials) that is harder to digest due to the complexity in their molecular structures. This process is usually energy consuming for the microorganisms, and the added sugar may provide them the extra energy needed for this. The airtight container is necessary to promote fermentation (minimize oxygen), and biogases will be produced as by-products of the anaerobic breakdown of the sugars (usually hydrogen, CO2, and less likely methane). Thus, releasing the gases produced, especially during the initial stages, is essential.
Can’t find the rationale for the stipulated “3 months”, but I guess this is based on past experiences. Definitely, longer durations would be more ideal to ensure a more complete fermentation process, where there will be none (or little) sugars left, and higher concentrations of products could be achieved. Also, the lack of food and the low pH levels would most likely kill/deactivate the microorganisms present (safer for handling).
Based on the preliminary test using gas chromatography, the major component of a newly prepared GE is acetic acid (in high concentrations), or “vinegar”. Slight ethanol (or “alcohol”) and propionic acid are also found in older GE samples. Do note that the machine used is calibrated to measure the presence and concentration of certain alcohols and fatty acids, and thus, may miss out several other important components (e.g., enzymes, sugars, amino acids, vitamins, etc.) that may also be present in the liquid. The pH measured for freshly prepared GE is ~4.4, and for the older sample is ~3.1, which will vary depending on the materials used.
With regards to the enzymes present, it is rather difficult to comment, as I do not have the right equipment at hand. One of the comments made is somewhat true, in the sense that microorganisms possess intracellular enzymes within the cells that may not be easily dislodged into the solution. However, there are microorganisms that secrete extracellular enzymes into the external environment to allow the waste to be broken-down outside the cell. Also, the enzymes here may refer to the enzymes present in the waste material itself. For instance, pineapples and papayas are known to contain bromelain and papain enzymes used for tenderizing proteins, respectively. Therefore, the acidic condition and the fermentation process may allow such enzymes to be extracted from the waste materials into the solution.
The high acetic acid concentration and low pH could be the main reasons for the many purposes of GE, as vinegar is well known to be used a cleaning agent, odor removal, preventing drain blockages, etc. Ethanol is known to have antiseptic properties, while propionic acid is used in food preservation. These substances may allow GE to act as an anti-microbial agent, insecticide and pesticide. When diluted, it could provide nutrients to plants due to the “growth hormones”, minerals, enzymes and/or other organic compounds extracted directly or converted from the waste materials. The highlight of GE is that it is organic and can be homemade at low costs, as compared to other products that contain synthetic chemicals (may be toxic to human health or environment) and consume high energy in their production.
On the contrary, please be careful of the white, black or brown layer formed on top of the liquid. Well, it could be yeast, as certain yeast prefers oxygen, thus forming a top layer in contact with the air in the container; but not all yeast strains are harmless. Similar to moonshine production, GE making involves the growth of the “unknowns”, so it is best not to have long direct contact/exposure with this layer or used for consumption purposes.
CO2 and methane:
Not much is being researched in terms of the CO2 production, but it is definitely there. Theoretically, aerobic processes would generate more CO2 than anaerobic processes, due to the more complete degradation of the carbon sources. Methane will only be produced in the presence of methanogens (certain kind of bacteria that are mostly found in swampy areas). Since the microorganisms present in GE are likely to be found naturally on the waste itself, airborne from the surrounding air, from the container or tap water added, chances of methane-forming bacteria to be present would be low.
This is surely more controversial. Ground-level ozone is known to be an air pollutant, causing adverse health effects, and should not be confused with the ozone layer in the upper atmosphere protecting us from the radiation. The low level ozone is generally formed from hydrocarbons and nitrogen oxides in the presence of sunlight. So, don’t think we are able to generate ozone through the fermentation of GE (shaded, and not much nitrogen oxides present); but if we do, it will be very scary… Therefore, those who claimed the benefits of ozone and its formation through GE should further substantiate their points.
Solid waste management:
Rather than to be disposed and incinerated, these waste materials can further serve additional purposes through GE, and subsequently be composted into organic fertilizer. This will surely help in preventing or reducing all forms of pollutions from the improper solid waste management and incineration, as well as to “close the waste loop” and promote recycling of waste back into the earth. Fruit and vegetable wastes are generated in huge amounts from both households and commercial/industrial sectors, and large-scale GE production would help to put these wastes into better uses.
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