Subject: LOW-TECH, HIGH-QUALITY ON-FARM COMPOST

From: Joel Gruver <[email-masked]>
Date: Fri, 28 Feb 2003 16:16:12 -0500

Hello SANET folks,

The following fact sheet includes a nice discussion of the benefits of
having **both** anaerobic and aerobic microorganisms active in composting
systems.

Joel

Joel Gruver
Dept of Soil Science
NC State University
[email-masked]

http://www.uvm.edu/vtvegandberry/factsheets/compost.html

LOW-TECH, HIGH-QUALITY ON-FARM COMPOST
by Vern Grubinger
Vegetable and Berry Specialist
University of Vermont Extension
(Adapted from information presented at workshops by Dr. Will Brinton, Woods
End Lab, Mt. Vernon, Maine.)

Anywhere you go, there are waste products that are totally useless in
farming that can be made into a useful product if proper compost recipes are
developed. Some of these materials are more challenging than others, such as
fish or paper mill waste, while others are easier to compost, like dairy or
poultry manure plus bedding. On-farm wastes and yard wastes tend to be
relatively free of contaminants compared to municipal wastes. With off-farm
wastes, total source separation that results in "clean" residues is
essential if the end-product is to be used in farming. Otherwise, a variety
of contaminants may accumulate in the farming system over time. Composting
for waste disposal and composting for production of a soil amendment can be
conflicting approaches.

A book that is helpful with compost recipe development, compost siting, and
compost marketing is On Farm Composting, available from the Northeast
Agricultural Engineering Service, Riley Robb Hall, Ithaca, NY 14853, as well
as from many Extension offices.

To succeed in making the highest quality compost with the least investment
of time and equipment, it is important to understand that there are 4
different groups of  microbes involved in composting. Obligate aerobes are
strict oxygen consumers that die off when oxygen is lacking. Facultative
anaerobes are versatile organisms that can be simultaneously aerobic and
anaerobic - in other words they adapt to the oxygen level of their
environment. Aero-tolerant anaerobes grown anaerobically in the presence of
oxygen - they don't use it but they can tolerate it. Obligate anaerobes are
limited to oxygen-free environments and die off if it is present.

All of these organisms have a contribution to make to the compost process -
there are no "good guys" and "bad guys". Contrary to popular belief, it is
not optimal to manage composting as an entirely aerobic process - obligate
anaerobes do not normally dominate until the end of the compost process
unless extreme measures are take to aerate the pile, such as frequent
turning or forced ventilation, which are expensive and unnecessary. Obligate
anaerobes do generate heat, which is important if the compost ingredients
are unsanitary (ie sewage sludge), and they work fast, which is helpful if
you are in a rush for compost. But the facultative anaerobes are just as
important to on-farm composting, because they function at lower oxygen
levels, minimizing the need for manipulating the pile, and they are also
responsible for generating the disease-suppressing abilities that have been
observed with certain composts.

Some degree of anaerobic respiration during composting is also advantageous
because it results in less loss of carbon than a fully aerobic process,
which in theory converts everything to the end products carbon dioxide and
water, although in practice a small amount of microbial biomass, or humus,
also results. Because anaerobic respiration results in the production of a
variety of end products such as organic acids and alcohol, the rapid loss of
carbon as CO2 is avoided, and there is greater opportunity for conversion of
the original carbon to humus.  Although the products of anaerobic
decomposition can be toxic to plants, as the compost process continues and
oxygen levels rise, aerobes will readily decompose these materials.

In other words, the extra metabolic steps that non-aerobic decomposition
contributes to the compost process leads to more microbial biomass and
byproducts to be generated, and these are the high molecular weight
compounds that comprise finished compost or humus. The result is that
carbon, and plant nutrients such as nitrogen, are more effectively recycled
than with highly aerobic, "clean-burning" composting.

All of the microbes required for a healthy compost process are already
present in most wastes that can be composted, and therefore the utility of
adding compost inoculant is limited. A notable exception can be food wastes,
which are often cooked (ie sterilized). In a study that examined the effect
of inoculants, added microbes could not subsequently be found in dairy
manure compost, apparently because the existing microbes excluded introduced
organisms.

The natural mix of organisms in compost makes the process very resilient to
varying environment is extremely low in oxygen for extended periods of time,
the result can be strong odors, a slow process, and the accumulation of
phytotoxic compounds. To avoid this situation without having to turn
frequently, compost piles should be built so that they are self-aerating.
This is accomplished by using materials with sufficient porosity, managing
moisture content to avoid soaking, and keeping windrows small enough to
avoid internal compaction. Then, the natural oxygen demand of the compost
process will assure a steady, low level of oxygen as it diffuses into the
windrow to replace the oxygen that is consumed by the microbes.

Although most farmer-composters do not monitor the oxygen levels of their
windrows, it is instructive to understand how these levels vary during the
compost process. Immediately after raw materials are mixed together, the
oxygen levels in compost are just below the ambient (outdoor) level of 22%
but drop off very rapidly as aerobic decomposition takes off. The process
soon shifts to a mixture of aerobic and anaerobic decomposition as oxygen
levels drop down and then fluctuates between about 2% and 5%, which is a
healthy range for facultative anaerobes. This level can be naturally
maintained in a windrow with sufficient porosity. Toward the end of the
compost process, oxygen levels start to climb back up, nearing ambient once
the compost is mature and decomposition slows to a halt. That's because as
internal oxygen demand subsides, diffusion of oxygen into the pile can catch
up.

However, the porosity of a windrow tends to decrease as materials are
decomposed, and for a short period of time, when oxygen demand is still
high, a windrow may go excessively anaerobic until diffusion of oxygen can
catch up. In many cases the best thing is to leave the windrow alone until
it re-equilabrates. But if the pile is not porous enough, or its core is
wet, then diffusion may be too limited, requiring turning to aerate the
pile. The key is not to over-do it, because aggressive turning further
reduces the porosity by breaking down the aggregates or small clumps of
composting materials, increasing the need for subsequent turning. In other
words, the need for frequent turning becomes a self-fulfilling prophecy.

In conclusion, some turning is usually needed to facilitate the compost
process. The use of sufficient bulking material and low-impact turning
methods (like a bucket loader versus a compost turner) can allow a windrow
to remain self-aerating with a minimum of  turning.  At the outset, raw
materials with sufficient porosity must be mixed together to distribute
carbon, nitrogen, moisture, and oxygen evenly through the windrow. Then,
after the initial burst of decomposition and oxygen consumption, a gentle
turning can help keep the pile sufficiently aerated. Finally, as the process
nears completion, turning helps homogenize the finished compost and mixes in
materials on surface that have not been fully decomposed.

Windrow height, after settling, should be no more than 3 to 5 feet unless
large amounts of porous materials like straw are being composted, otherwise
the core will become compacted. Keeping the windrows small also avoids
high-heat conditions which encourage the loss of moisture. The windrows must
be kept moist with irrigation if necessary. If rains threaten to saturate
the windrows, they must be covered.

Under this type of low-tech, "minimum tillage" management system, dairy
manure or similar materials should compost to maturity in 4 to 5 months. The
cost to produce compost using a bucket loader to turn 3 times is about $7
per ton. Obviously this figure will vary depending on material and labor
costs.

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From: Joel Gruver <[email-masked]>
Date: Mon, 3 Mar 2003 12:30:33 -0500

Hello Elaine,

Thanks for your thoughtful comments.

Perhaps I was rash in posting the fact sheet to SANET.
As I have already posted, I find some of the statements to be questionable.

I am familiar with much of the current literature on the formation of humic
substances. Humic acids and fulvic acids are artifacts of a purely chemical
alkali extraction process and are no longer investigated by most scientists
currently evaluating the ecological significance of organic matter.

The stability of OM in soil is the interactive effect of biochemical
recalcitrance, chemical interactions with mineral surfaces and physical
protection (within aggregates). Current research results suggest that
biochemical recalcitrance may the easiest hurdle for the soil food web to
overcome.

I appreciate your public acknowlegement of the ecological importance of
"aerobic, intermediate aerobic - anaerobic, and true anaerobic conditions"
in soils and compost.

Joel

Joel Gruver
Dept of Soil Science
NC State University
[email-masked]

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From: Elaine Ingham <[email-masked]>
Date: Mon, 3 Mar 2003 11:04:47 -0500

Hi Joel -

Please read some of the published work about how humic acid is produced.

I think we all agree that humic acids are very long-term carbon compounds.  Their half life is on the order of several hundred years.  There are several very good books on the subject of humic acid production.  Those books very clearly show that SOME humic acids are produced aerobically, SOME are produced in minimal oxygen conditions, and SOME are produced in low oxygen conditions.

For anyone to claim that high molecular weight compounds are only produced in anaerobic conditions is silly.  Any scientist should be able to see through that claim in a second.

Good compost has good aggregate structure, and the insides of aggregates can be anaerobic.  As shown by the pioneering work of Sexstone and Tiedje at Michigan State University quite some number of years ago, and by quite a number of other people since the time they published that work, the insides of such aggregates can have very low oxygen concentrations, as low as 1 or 2 ppm, or less.

Thus, good aerobic compost has anaerobic microsites.  BUT, as the anaerobic metabolites such as ammonia, hydrogen sulfide, acetic acid, putrescine, etc diffuse and volatilize out of the aggregates, they reach aerobic zones, where the plant toxic materials are converted to aerobic products.  When these anaerobic microsites are broken open, aerobic organisms re-colonize.  It is important for the diversity of foods in a good compost that BOTH aerobic and anaerobic organic material is present.  Diversity is the key.

In well-aggregated composts, N, S, P, etc, are not lost because the anaerobically produced materials are captured by the aerobic organisms before those gases leave the pile.  Look at the work by Malcolm Beck, for example.

In completely anaerobic material, fertility will be lost. N will be lost as the gas, ammonia.  S will be lost as the gas, hydrogen sulfide.  Both can easily be identified by the human nose.

If for no other reason, you can't allow your compost, compost tea, or soil to go anaerobic, because you lose the nutrients you are trying to conserve.  You lose the nutrients that will result in good plant production.

The maximum production of "soil glue" occurs in aerobic conditions.  Note the recent work on glomalin from the researchers at the USDA.  These materials are produced by mycorrhizal fungi.  Mycorrhizal fungi are STRICT aerobes.  They cannot tolerate anaerobic conditions.

Check the work of Dick Wiebe at Univ of Georgia.  Spartina is mycorrhizal when it grows outside the riparian zone, but is not colonized when it's roots are in anaerobic mud.  when your soil goes anaerobic, the mycorrhizal fungi are lost.  And thus we lose what the USDA is terming the most important binding material in the soil.  Do you think that is not high molecular weight material?  According to the USDA researchers, it is.

The people at the the University of Vermont who wrote those factsheets perhaps need to rely less on a single opinion.  Check things out before sending things like that out.

When we are working on the cutting edge of technology and science, and there is no scientific literature on a topic, we are faced with a different situation.  But there is quite a scientific literature on production of high molecular weight materials in soil.  Humic acid production has been reasonably well researched, although there is quite a bit more we would like to know.  To maximize the production of humic and fulvic acids, and other complex compounds, we want a mix of aerobic, intermediate aerobic - anaerobic, and true anaerobic conditions.

In 24 hour compost tea, we do not want that mix of conditions, because it is in anaerobic conditions that some quite toxic materials can be produced.  In anaerobic teas, you must allow a significant period of time for the truly toxic anaerobic by-products to be consumed in aerobic conditions before using the tea.

That's why anaerobic compost teas have such long brewing times.  They require two to three weeks before they can be used, because if you go anaerobic, and have Clostridium botulinum grow and produce toxin in the brew, you have to allow time to let that toxin decompose before you apply that tea.

There is a massive difference in the metabolic products  produced in aerobic versus anaerobic teas, I'll stand side-by-side with Wil Brinton in saying that.

BUT, the reason I don't recommend anaerobic tea is for the reason that many anaerobic by-products are deadly toxins.  If you don't understand what you are doing, brewing an anaerobic tea can be really bad news.

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com