Compost tea has 'come a long way', especially in the last 10 years, and mostly (in my opinion) due to the efforts of Dr. Elaine Ingham .
I study compost tea microbilogy under Dr. Ingham and attend her headquarters seminars in Corvallis, Oregon each year to ensure that I'm using the latest information and techniques in my ROI Laboratory where I analyze the microbiology of soil, compost and tea for my commercial clients.
There are a LOT of different products that purport to have microbes in them - but most have VERY FEW, based on inspection with my microscope at 400x - and many of the microbes that I do find in the products are not the right kinds. Buyer Beware!!
There are also many kinds of compost teas, and as many recipes for tea as there are tea machine (brewer) manufacturers and people who experiment with recipes in their home brewers.
But let's be very clear about one very important issue. Unless you view compost tea at 400x with a light microscope, it's all just guesswork - which is NOT the right way to assess a microbial product.
As long as you're just guessing, you should NEVER sell your tea to anybody, because doing so would open you up to serious liability consequences if someone were to become ill, or your product has a detrimental effect on plants.
I'm not saying that your tea would, or even could make somebody sick. But supposition is what drives lawsuits. Unproven possibilities and probabilities can cost you your entire life's savings in a court battle to prove your innocence. That's life, in today's screwed-up world.
And not just looking at all the 'critters' growing and reproducing in your tea - but being able to recognize what you are looking at. Is that microscopic creature a bacteria or a protozoa? Is it a 'good' guy or a 'bad' guy?
Could you recognize an E.coli microbe if you saw one? That takes some training, which I highly recommend.
Start by obtaining a copy of Dr. Ingham's book: "The Compost Tea Brewing Manual, 5th Edition", and her book: "Qualitative Assesment of Microorganisms". I also recommend her book: "Compost Tea Quality: Light Microscope Methods".
Not just any microscope will do. Must be one with a powerful light source. A good one can be purchased for $1,500 (with supplies) but the better ones cost in the $2,500 range. No, you don't need the best ones - they are in the $25,000 range.
And consider the issue of food for microbes. If you don't use microbe food in the water to make tea, then chances are the microbes won't reproduce much, and you may be breeding the 'bad guys'. Food recipes for composting and/or tea brewing should select for beneficial microbes.
There is still a lot of misinformation about using molasses in compost and tea. Molasses is almost pure carbon. Sugar is an energy food, and has very little value in exponential microbial reproduction which requires nitrogen in PROTEIN form.
And of course you know that putting too much food in the water can keep the water from reaching the MINIMUM 6ppm level.
Yes, it takes a high level of oxygen. More oxygen than it takes for fish to survive in an aquarium tank powered by a dinky airstone aerator dropped into a 5-gallon bucket. If the water does not contain MORE than 6 ppm (6 mg/l) of DISSOLVED oxygen, exponential reproduction of microbes will not happen, and you'll mostly breed anaerobic microbes, many of which can be pathogenic ('bad guys').
How does one determine if the compost tea has at least 6 ppm dissolved O2 in it? A dissolved oxygen meter. A hand-held unit can be purchased for $400 - the best ones are in the $1,200 range. It is also necessary to monitor water temperature and pH in tea.
And remember the primary issue. Compost tea is made with compost. And the tea made with the compost will NEVER be any better than the quality of the compost you start with.
If the compost you use to brew tea is not tea-quality compost, you're NEVER going to have very good tea. Why? Because there's more to tea than how many microbes are in the tea. The other side is DIVERSITY. How many DIFFERENT KINDS of microbes are growing in the tea. How does one grow a diverse population of microbes? By using a diverse set of foodstocks to make the compost.
Even if you started with tea-quality compost, if you just fill a sock or bag with the compost and drop it into a tank to steep - the microbes are going to stay in the compost. In case you didn't know, microbes make a sticky substance (exudate) so they stick to what they grow on.
Unless the microbes get violently SHAKEN into the open water, outside the containment, exponential reproduction is simply not going to occur - even with the right kinds and amounts of foods - unless you brew for several days.
The word 'violent' pertains to a microbe perspective. The other word used is 'agitated'. As in forced away from where they were stuck. Forcing air and water THROUGH the bag that holds the compost is one of the keys to successful tea brewing - mainly because you would not be willing to sit at tank-edge and constantly squeeze a bag of compost for many hours.
How long does it take to brew a good batch of tea? Considering that all other factors are optimized, the GENERALLY-ACCEPTED minimum time for a high-bacteria brew is 24 hours. This brew is usually called a "concentrate".
Double the brew-time to 48 hours (which means adding more microbe foods of certain types, in certain amounts, at certain times) provides greater opportunity for protozoa and fungi to reproduce. This brew is called a "super-concentrate".
At this writing, the longest brew time that I work with for AACT (Activated Aerated Compost Tea) is 72 hours. I call this "super-ex concentrate". The longest period of time that I have personally brewed compost tea? 8 days. That was to innoculate the water a newly-dug rainwater harvest pond in solid gumbo clay.
Brews longer than 24 hours can get complicated, because there are specific criteria which must be checked by electronic devices and a microscope, at set intervals; food levels must be controlled and oxygen must be maintaining the correct oxygen levels continuously is critical.
It is extremely important that such a brew NEVER be permitted to go anaerobic. Not even for a few minutes. In any brew, there are ALWAYS faculative microbes that can live in either an aerobic or anaerobic environment, which will attack aerobic microbes if the solution becomes even slightly anaerobic.
This kind of commercial-level tea is extremely powerful. Thousands of times more powerful than solid compost.
I'm not finished with trials at this writing, but it appears that this kind of tea is capable of curing a virus infection on a vegetable plant. Previously unheard of.
I'm working with a Texas County Agricultural Extension Agent in a trial of tomato plants that have been confirmed with Beet Curly-Top Virus. Texas A&M University has not released data yet from their lab tests, but already we've seen a 100% recovery rate of plants that had NO normal leaves - severe 'clubbing' - to full recovery with blossoms and fruit only two weeks after tea application. I'll provide a report after the A&M results have been published.
A lot of work is also being done to extend tea shelf-life. At this writing the accepted shelf life of compost tea in a sealed container is 4 hours, and that's with only filling the container 50% - and leaving a 50% air space. Why? Because the high concentration of microbes in the tea rapidly consume the oxygen in solution, which drives the liquid into anaerobic condition.
The more air in the container, the longer the microbes are capable of surviving. Many bacteria can simply "go dormant" when the oxygen level gets low - but many microbes (particularly fungi and protozoa) die because they are attacked by, and eaten by the faculative bacteria which suvive and thrive in anaerobic conditions.
This is a consideration when sending tea samples into a lab for analysis too. No matter how large the container, NEVER fill the container with tea, to more than 1/2 of capacity. ALWAYS leave a 1/2 air space.