Boulder Vermicomposting

Interview: Commercial Compost Tea Production

December 21st, 2008

I had the good fortune to interview Dan Matsch, who works at Eco-Cycle here in Boulder.  They sell compost tea made from worm castings, and he and I had a great conversation ranging in topic from the benefits of compost tea to his experiences in home worm keeping to where Eco-Cycle gets feedstock for the worms.  The entire interview is below.

Dan Moore: What is your position at Eco-Cycle?

Dan Matsch: Manager, Center for Hard-to-Recycle Materials (CHaRM) and Compost Dept.

Moore: How long have you been involved with vermiculture?

Matsch: ~20 years personally and professionally.

Moore: Do you care to elaborate on your 20 years of experience–that’s a long time!

Matsch: Prior to my career at Eco-Cycle I was an organic vegetable farmer for 13 years and always had a variety of vermicomposting projects going, mostly using the castings as part of a potting mix for my greenhouse transplants.  And I’ve kept worms for my kitchen scraps at home for many years.

Moore: Are there any special challenges to vermicomposting in the Colorado area, as opposed to other parts of the country?  Or is it all pretty much the same?

Matsch: Worms like 70 degrees F, high humidity within their living media and darkness.  That doesn’t exactly describe Colorado’s climate, but the worms are native to a large part of North America including Colorado.  They can fend for themselves in their native environment, but if you constrain them to a box and expect them to eat and reproduce at a certain level year-round, you have to monitor their habitat very closely.  That’s why I always recommend to backyard composters that they use or build a bottomless worm bin that sits on top of – or better yet, is built into the ground.  If the worms can escape adverse conditions by burrowing down, their survival and your success as a vermicomposter increases greatly.

Moore: Do you have any advice for small scale worm keepers?

Matsch: Keep them in the ground [as mentioned above].

Moore: Do you still keep worms at home?

Matsch: Yes, we have a 4’x8’ concrete block lined worm bed built into the ground in our back yard that produces about a cubic yard of castings every spring.

Moore: What has been your greatest success?

Matsch: Our Eco-Cycle high-tech compost tea worm farm is very fun, but I think the greatest reward is creating a closed-loop nutrient cycle at home because it’s so tangible.  All our organic waste from kitchen scraps to yard waste go to the worms (the yard waste gets ground up first in a shredder).  The worms and all the associated organisms break it down into castings, and that becomes the fertilizer for our gardens, which grow most of our food.

Moore: What kind of worms are used to create the compost tea?

Matsch: Eisenia Fetida.

Moore: How many worms?

Matsch: Our capacity is for about 150 lbs.

Moore: Is Eco-Cycle’s compost tea operation profitable?

Matsch: It’s within the realm of Eco-Cycle’s model of ‘cost + 10%’; however, we are doing it to raise awareness that food waste is a liability in the landfill, while a valuable soil amendment when composted or used to make high-value soil amendments like compost tea.

Moore: Where is [the tea] sold?

Matsch: Boulder Farmers’ Market on Saturdays, Eco-Cycle CHaRM on Wednesdays, April through September.

Moore: What kind of equipment is used to house the worms?

Matsch: We have a ‘flow-through worm digester’ that harvests castings from the bottom of their space, and we have a fiberglass  worm farm that was originally manufactured by one of those ‘get rich quick growing worms’ scams that actually works quite well.

Moore: What kind of processing is needed to create the tea?

Matsch: Castings from the digester are ready to go with a turn of the harvest wheel; castings from the fiberglass farm must be hand-harvested, then screened, then formed into a cone in bright light to drive remaining worms to the bottom and slowly harvest castings from the sides.  The brewing itself is much like brewing a pot of tea, except the water temperature is 70 degrees and the process is 24 hours.  A better analogy of what is really happening, though, is a Petri dish:  favorable conditions are made for the beneficial soil microbes, already in abundance in worm castings, to reproduce millions of times over in the water culture.  So you are literally pouring microbes onto your soil when applying the tea.

Moore: How much tea is produced weekly?

Matsch: Currently we can brew 125 gallons twice a week, though we may expand by next season.

Moore: What are the benefits to the tea?

Matsch: The tea builds the population of beneficial soil microbes once applied.  This improves a plant’s ability to uptake nutrients, since nutrients are exchanged by microbes at a plant’s root hairs.  So with more microbes in the soil, more nutrients are exchanged with the root hairs.

Moore: Are you aware of any scientific studies testing the benefits?

Matsch: As with most organic soil amendments, funds for studies through land grant universities are very limited.  The previous statement about the benefits is simple logic but has been confirmed at a basic level by Dr. Clive Edwards and his colleagues at Ohio State University.  Beyond that, most studies I’ve read focus on whether tea can function effectively against various common plant diseases.  Steve Scheuerell and Walter Mahaffee of Oregon State University conducted a literature review in 2002 called, “Compost Tea:  Principles and Prospects for Plant Disease Control” which is widely quoted.  They have since published several other reports.

As with compost, though, I think it’s difficult to understand what is happening with compost tea through the scientific method of reduction.  Tea is not a fungicide.  It works in several ways to outcompete leaf-borne disease organisms for food or space on the leaf surface, and it works to bolster a plant immune system.  Like studies done on holistic medicine, applying scientific technique to the study of a specific disease creates many variables and therefore variable results.  It’s like the old story about 10 different people getting drastically different results examining parts of an elephant in the dark.

Our own greenhouse trials have focused on how compost tea affects seedling plant growth.  Control and test are always comparable until some kind of stress is introduced.  Then it is quite clear that the test plants have a stronger immune system that powers through the stress with less – if any – check in growth.

Moore: What happens to the vermicompost after tea is made?

Matsch: It is still inoculated with soil microbes, so we let excess moisture evaporate for a week or so, aerate it, and mix it with worm food the next time we feed.

Moore: I’m curious about that, as it seems you’d just accumulate more and more vermicompost/castings, and eventually you’d need to clean out the digester and worm farm.  Eventually, you end up with a mass of castings, don’t you?  What happens to that?

Matsch: The baskets that hold the castings in the brewer are about 1/3 full after the tea is brewed, so a majority of the castings dissolve into the tea.  Eventually we will produce a surplus of castings as the worm population maximizes, but both our worm farms get harvested pretty heavily during tea season and the boxes don’t have a lot in them by fall.

Moore: How much waste goes into the process?

Matsch: Theoretically the worms should be able to process half their weight daily.  In reality, they are eating about 250 lbs per week.

Moore: What type of waste is it?

Matsch: Half food waste, half crushed dried leaves by volume.  For the most part, it is organic vegetable kitchen scrap, but we give the worms a mixed diet.  They have had a lot of apples this fall from a program in Boulder that picks up fallen apples from people’s yards to try to mitigate their attractiveness to bears.

Moore: How is waste collected, and from where?

Matsch: I either cherry pick from some of our Zero Waste Services restaurant or grocery store customers, or from material brought to our food waste drop-off at the CHaRM.  We have some people bringing clean vegetative food waste specifically for the worms now…they may need their own collection dumpster soon!

Moore: What is the long term sustainability of people driving to drop food off for the ecocycle worm composters?  Where does home vermicomposting fit into this picture (if at all)?

Matsch: Backyard composting is by far the most efficient way to handle organic waste – meaning kitchen and yard waste – and I strongly believe that worm composting is the best fit for the vast majority of people who want to backyard compost.  Curbside collection of organics for commercial composting is the second-most efficient.  The City of Boulder is slowly rolling that out for their residents, it’s an option for unincorporated county residents, and Eco-Cycle has collections for our commercial customers.  But that doesn’t cover everybody, and not everybody can backyard compost.  So a variety of solutions is necessary to keep organics out of the landfill.

Entry Filed under: Uncategorized