The Dangers of Worm Farming

You are aware of some of the benefits and even joys of worm farming, but you also need to understand the dangers and responsibilities of the business of working with worms. Good intentions and warm fuzzy feelings are not enough! Worm farmers are generally responsible and conservative people, who are all well intentioned. But there are a few who are prepared to take severe environmental risks or gamble their entire assets at short odds, whether through ignorance or recklessness. Aerobic composting, anaerobic digestion and vermicomposting are all roads to the stabilisation of organic matter, but they follow very different routes. You know about vermicomposting but, to understand the dangers of worm farming, you need a little appreciation of these two other means of organic waste stabilisation.

Stabilisation is a process whereby the C:N ratio of the waste is reduced below 20:1 (refer to the Best Practice Guidelines on page 207 onwards). Of the three methods of stabilisation, aerobic composting includes the built-in safety factor of heat production as a consequence of the process. The bio-generated heat reaches temperatures high enough to pasteurise the compost and kill off most seed fertility and pathogens. (A temperature of 60oC is regarded as high enough to achieve this.)

Anaerobic digestion takes place in the absence of oxygen and usually at temperatures not exceeding 45oC. Uncontrolled anaerobic decomposition is what goes on at landfill tips, and is generally to be condemned and avoided. However, in controlled conditions, where the process is enclosed and the methane gas can be captured and put to good use such as electricity or simple heat generation, anaerobic digestion has a place in the treatment of our organic wastes.

A valuable secondary product of anaerobic digestion is the rich, solid, black humus residual after the process is completed and the black odorless liquid from which even more humus (as opposed to compost) can be extracted. Humus is invaluable as a soil ameliorant. The black liquid itself, which is rich in benevolent humic and fulvic acid, can be applied directly to soils and is used by biological farmers to improve soil quality.

Modern anaerobic digesters use what is termed a ‘split system’, with two digester cylinders. In the first, the bacteria generate an environment of around pH 2.8, so that all plant pathogens and seed fertility are destroyed, as are all known pathogenic bacteria and most viral populations.Despite its black color and relatively unsavory production process, the humus derived from anaerobic digestion is as pure as the driven snow. While it is rich in bacteria, you may well argue (given the smell of the anaerobic process) that these anaerobes are not soil-benevolent. But most bacteria are facultative, which means that they can change from anaerobic to aerobic very rapidly, according to their environment (see also ‘Puree’ on page 174). Therefore, applying humus (which is derived from an anaerobic process) to aerobic soils is quite proper.Vermicomposting is a process you are already familiar with. It is the means whereby worms convert organic waste into vermicast (i.e. they stabilise it). During this process, which is in an aerobic environment, antibiotics that destroy most pathogenic bacteria are generated. But, because the temperature is below 30°C, seed fertility is not destroyed.

CAUTION: Note that not all pathogenic bacteria are destroyed during vermicomposting, so take care in handling the vermicast. If the originating material can be expected to be high in pathogen levels, assume there will still be a population in the vermicast. That population will be diminished, effectively trampled to death by the benevolent bacteria, but there could still be sufficient to cause harm. A warning notice on the retail package would be a wise precaution.I like to quote Robin and Frank  Dowdle  of  Camphor Creek Worm Farm, Nana Glen, New South Wales. They apply vermicast not only to their farm pastures, but also to personal cuts and abrasions. For this medicinal application, they use thoroughly aged castings that have a very low possibility of carrying pathogens. They vow that the rate of repair is rapid and scar tissue minimised to nil. I quote this purely as an example of one of the more unusual (and remarkable)uses of vermicast and do not recommend it for general application.

Fertile Seed

Not only can seeds be ingested by worms, they can be passed through their digestive systems and redeposited (wrapped in castings) in the soil without suffering harm (Lee, 1985). Specific testing has shown that they remain fertile.We have already seen that vermicast is the ideal seed germinator and the best seed-raiser known. Any fertile seed deposited in vermicast has every chance of germinating successfully and growing into a reproducing plant. If this seed-bearing vermicast is subsequently packaged and sold, the seed will travel in that package in a medium that guarantees it the greatest chance of surviving and thriving wherever the vermicast is ultimately used.

Murphy’s Seed Laws:

  1. Any seed transported nationally in a bag of vermicast will be that of a noxious weed.
  2. Any noxious weed seeds in vermicast will always germinate successfully and thrive.
  3. Any noxious weed seed found germinating in vermicast will be of a type not found previously in the surrounding district.
  4. Any noxious weed seed germinating in vermicast will be devastating to the surrounding natural environment.

If a vermicast producer is dealing with a national chain store, the potential damage from fertile seeds is frightening.

Consider the following scenario . . .A vermicast producer gets a big order from a national chain store. Because he can’t produce enough himself, he buys in from various other operators in his district. One of these operators is producing vermicast from cow manure, in an area that was quarantined a few years ago because of an outbreak of anthrax. All the cattle on the affected farms were destroyed and burnt, so the product drawn from that area should be safe – or so our producer thinks.But, he hasn’t thought very deeply. Anthrax is transmitted by touch, aerosol and ingestion. It is excreted by the host animal in saliva, urine and dung. It affects some animals not at all. Worms may be amongst these, but nobody knows because no research has been done on anthrax and worms. Anthrax bacilli might actually flourish in worms – we simply don’t know.The anthrax spores form a protective shell about the bacteria’s genetic components and lie dormant in the soil, waiting for the right conditions to dissolve the shell, when they become animated. (So, an outbreak can occur years after a previous one.) The bacilli attach themselves to grass and are ingested by cattle or sheep. Some forms of anthrax are deadly. There is no cure. Symptoms are not displayed until the bacilli are well established within the newly afflicted animal (which can be human) – sometimes only about an hour before death.Our producer receives vermicast from his various suppliers and mixes it all together to make a reasonably standard product before bagging and delivering to his customer. He does not carry out pasteurisation. Trials clearly demonstrate that plant pathogens of various types can be passed through a worm’s digestion without harm. If manure containing the anthrax bacilli has been ingested by the supplier’s worms, our producer could be packaging, delivering and selling not just vermicast, but also anthrax and weeds. The bacteria might even have thrived and multiplied in the worms’ guts, resulting in the excretion of many anthrax spores in the vermicast.

The point I’m making is that some pathogens survive vermicomposting and, as they are micro-organisms, you can’t see them – so you won’t know whether they’ve survived or not. Therefore, no producer of vermicast can distribute their product secure in the knowledge that they are not also distributing trouble unless the product is pasteurised or the feed stock origin can be warranted free and clean (see pages 219–21 for information on pasteurisation). Vermicast, by its very nature, contains huge numbers of micro-organisms and they may not all be good. Any person selling unpasteurised vermicast commercially is a gambler. They are betting all their assets. But worse, they are betting our assets – our environment and that of our children.

In the case of a small producer selling into a niche market, the potential damage is confined in area. But, as the business grows, so do the dimensions of the problem. The more widely the product is  distributed,  the  more  serious  the  potential damage. (Vermicast produced and used on the same property, at home or on a farm, is another matter. Anything undesirable that may be there stays there.)

Pathogen destruction

I stated earlier that pathogens do not thrive in a worm-dominated environment. Orange County (Florida) Environmental Protection Division undertook structured trials of vermiculture as a medium for pathogen destruction in sewage sludge. This was done in cooperation with the American Earthworm Company and the United States Environmental Protection Agency, or USEPA. (In fact, when asked for criteria and standards for pathogen destruction, USEPA was found to have none and so criteria were developed specifically so that the trial could proceed.)Two systems were set up: one with vermiculture and the other without, for comparison. Both were deliberately inoculated with pathogens listed below. The vermiculture system was seeded with Tiger worms (Eisenia fetida).   Dr. Clive Edwards ran a similar but more extensive trial, reported on Bio-Cycle somewhere around the early 1970s.  His results also demonstrated the effectiveness of WORM POWER !!

Vermiculture control of pathogens

The more rapid destruction of each pathogen in the vermiculture system evident in the table above was credited entirely to the worm-induced environment, while the destruction in the system without vermiculture was credited to natural mortality in the aerobic environment – meaning it wasn’t destruction at all but attrition (Eastman, 1999).

This trial could well have been set up using Worm Tea and Worm Bed Leachate.  The difference is obvious and to even the untrained eye it should now be clear that if you  trap and use leachate you are taking grave risks – and I’ll show you just how grave below, so read on – but if you make your worm tea as it should be made, with vermicast, your risks are greatly reduced and given a little more time, probably eliminated.

The Victorian Institute of Horticulture ran a series of tests at the Melbourne Wholesale Fruit and Vegetable Market in February 1996.   Here is a list of the various fungi found on fresh fruit and vegetables.    This fresh fruit and veg. is bought at the market and sold in suburban fruit shops and in supermarkets and we all take it home and eat it.     If you eat the skins, then you ingest some of these fungi.    If you don’t eat the skin but have a worm driven waste disposal unit, most and even all of these fungi go into your worm bed.

Now, one of the preferred food of Compost Worms is fungi, and they will do an eager worm pounce on the fungi loaded skin waste you give them.   Given a little time, they will eat all of the fungi which will be destroyed in it’s passage through the worm’s gut.        Here’s the list of fungi Horticulture Victoria found. 

Melbourne Markets Waste

So, you have two examples here.   The first with the participation of the USEPA showing that worms are a credible force in the destruction of pathogenic bacteria and an example of the fungi on fruit, vegetables and herbs over the months of November & December 1995 and January 1996.     Nothing will have changed since then, and if you use leachate, you will be spreading some or all of these fungi around your garden, and never risk selling it or giving it away to friends – or even to enemies and people you don’t like !   The potential damage just isn’t worth the risk.


Gardening Australia.

On Friday night (February 22, 2019) I watched an edition of Gardening Australia.  I’m a fairly faithful watcher of this program and I can’t recall ever before seeing a foolish and irresponsible sector.  Sadly Friday night showed a demonstration of how to establish a worm farm, including the adding of some manure, and a demonstration of how to deliberately make leachate which was of great benefit to the garden.   I tried to ring the ABC but have not been able to find a phone number. They need to show a retraction and give the reasons for it.  And they should repeat this on more than one program.  Also demonstrated was how to bury a perforated bucket containing some appetising worm food, in the garden so that you could trap some hungry rascal lumbricids.  So prolific would these hungry little devils be that you won’t need to buy any worms !   More incorrect information, but happily of a type that can’t do any harm.  It’s just incorrect as we know. I don’t think I’ll ever understand why people, however well intending, but without knowledge or experience, seem to think they are experts in worm farming.   In this case, so far as any knowledgeable worm farmers watching are concerned, this presenter (whose name escapes me) lost all her credibility.