| COMPOST
IS NOT A |
DIRTY WORD
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As the state struggles with a mandate to reduce waste in
our landfills by 50 percent, cities and businesses search
for opportunities to comply. One significant contribution
to the cause is green waste recycling.
“The biggest problematic waste stream in California
is green waste and food waste,” said Mary Keil. “They
make up approximately 40 percent of waste in our landfills.”
Keil is an environmental protection specialist with the Solid
Waste Programs for Region 9 of the EPA (Environmental Protection
Agency).
While cities and counties deal with waste reduction on a
large-scale, some green businesses are quietly working on
small projects to help the state reach its goals. Not only
does the state benefit, but the businesses do too in the form
of reduced disposal costs. By avoiding the landfill, businesses
also avoid tipping fees.
According to the EPA, depending on the type of waste and
method of composing, average national savings over conventional
disposal (in landfills) vary from $9 to $37 per cubic yard.
The potential savings make the process worthwhile to businesses.
“San Diego has achieved approximately 48 percent reduction
in the waste stream,” said Stephen Grealy, recycling
program manager for the City of San Diego. Grealy is also
a board member of the California Organic Recycling Council.
“If we make a good faith effort, the state EPA will give
a three year extension,” Grealy said. “We may get
an additional two years if we still haven’t achieved
our goal. But by 2005 we must meet the mandate or it’s
a $10,000 a day fine.”
San Diego is number two in the state, tied with Oakland at
48 percent waste reduction. San Jose achieved 53 percent.
The EPA set 1990 as waste year baseline. “Some cities
were abnormally high that year, others abnormally low. That
was the single most significant influence on whether cities
are now meeting the goal,” Grealy said.
About 55 percent of the green waste collected comes from
landscapers, 45 percent comes from city collection. The city
started making a compost product in early 2000 to resell for
commercial use, Grealy said. They ran out quickly because
demand was so high. For businesses who create their own compost,
the supply can be steady.
SMALL SCALE EFFORTS
“We began composting about four years ago,” said
Alan Stockton, key accounts manager of Miramar Wholesale Nurseries.
“We started by cooperating with Landtrends, a sister
landscape maintenance company,” Stockton said. The initiative
was developed to support conservation and minimize dump fees.
It was a win-win program that enabled both environmentally
concerned businesses to save tipping fees and reduce ultimate
plant mix costs by recycling green waste. Additionally the
byproduct was used as a mulch on various Landtrends’
maintenance projects.
Together they developed the area’s sole in-house green
waste program dedicated to landscape and nursery usage. As
a result, in 1999 Landtrends received the Directors Award
in Green Waste and Recycling from the City of San Diego’s
Environmental Services Department.
TruGreen LandCare subsequently purchased both Landtrends
and Miramar Wholesale Nurseries. And while the composting
pile remains relatively small, the process continues. “TruGreen
is committed to protecting the environment,” said Tom
Smith, Southwest Region Manager of TruGreen LandCare. “Composting,
even on such a small scale, benefits the entire county, and
it helps us as well.”
Smith is right. Not only is composting a good idea ecologically,
it is also an excellent soil amendment and can have a major
impact on any garden. Like making lemonade from lemons, the
nursery and landscape company turn green waste into a useable
product they have confidence in. About two years ago Miramar
Wholesale Nurseries started mixing the compost into soil used
at the site to grow plants. A sifter and grinder filter trash
and chew the green waste into useable size. Small bits are
added to soil while larger chunks become mulch to use on top
of plantings. The compost acts as an enhancement to preserve
water and nutrients.
“This branch now recycles 95 percent of the green waste
generated on landscape maintenance projects,” said Larry
Neuhoff, San Diego maintenance branch manager for the Southwest
Region of TruGreen LandCare. “We pre-sort to remove non-recyclable
waste such as trash, palm fronds, and certain fibrous plant
that won’t readily breakdown or may clog the shredder.”
When the crews return to the compound at the end of the day,
the green waste is separated into two piles by size. Grass
clippings, leaves and other material under one-half inch is
in one pile, everything over one-half inch goes in a separate
pile. “The larger items are shredded to reduce the particle
size,” Neuhoff said.
The nursery grows more than 2.5 million plants on approximately
350 acres, so a steady supply of quality soil amendments is
a great benefit. “Quality control is a big issue,”
said Suzie Wiest, branch manager of the nurseries. “Because
we use the compost as a supplement to our soils, we like knowing
what is in it. This is a voluntary, internal operation that
provides us an organic soil amendment and reduces waste. It’s
worked well for us and should work well for other landscape
organizations too.”
CONVENIENCE VS COMMERCIAL
As long as the project remains small, the “backyard”
recycling program is effective for businesses. Larger operations
can require special permits. “A compost pile that’s
less than 2,500 cubic yards should be exempt from permits,”
said Matthew Cotton, a technical consultant who specializes
in developing and permitting compost sites. “The regulations
can be a little vague, so always check the local zoning laws
to be certain.”
But 2,500 cubic yards is a pretty big compost pile. According
to Cotton, that averages up to 10 feet wide by 100 feet long
by 5 feet high.
Additional permits may be required if the business wants
to resell the compost or mulch. Cotton said size is again
a factor, that if a company is producing compost on a large
scale and reselling it, another permit may be necessary. Projects
like the nursery/landscape company partnership are very effective
— both benefit, yet neither is burdened with the need
for permits.
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| Not all green waste needs to compost.
Large pieces of woody material may be dried and processed
through a grinder to create mulch. |
The EPA does not discourage businesses with large green waste
output from pursuing a permit to process and/or resell compost.
In fact, it lists the potential saving from reduced disposal
cost and revenue generated from the sale of compost, mulch
and soil blends as direct benefits to businesses.
“Another way to reduce waste is by grasscycling,”
Grealy said. “Many landscapers use this practice. It’s
using a mower that chops the clippings so fine that they don’t
have to be collected — the clippings remain on site.
This process can cut waste, cost and fertilizer use. No one
has to stop mowing to dump bags or cart the waste anywhere.
We do this in all golf courses (except greens) in San Diego
and in all city parks and recreation departments.”
The city collects green waste at 146,000 homes and process
90,000 tons of it into compost and mulch. San Diego has won
awards from U.S. Conference of Mayors, Keep California Beautiful,
and the California EPA for its green waste recycling program.
After collection, the city creates and distributes compost
at the Miramar Landfill Greenery. “We’re very careful,”
Grealy said. Like Wiest at Miramar Wholesale Nurseries, Grealy
said quality of green waste is paramount. “The main idea
is be consistent with quality. We compost everything to kill
weed seeds and pathogens and diseases. And are very strict
about no trash.”
Vigilance is important to the quality of the product. “Businesses
who want to develop their own compost facility should be aware
of the work involved in maintaining quality control,”
said Joshua Dake, inventory control manager at Miramar Wholesale
Nurseries. Dake offered the following tips on maintaining
a composting operation.
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| A loader mixes fine organic compost and
soil. |
THE PROCESS
Compost is highly regarded for its ability to improve soils,
which greatly enhances plant growth. Because of its lack of
nutrients, compost alone cannot grow plants. However it is
beneficial to the soil, improving the soil’s structure,
water penetration, and moisture holding capacity. It can help
prevent erosion and weed germination, while increasing the
overall productivity of the soil. A good composting operation
depends on several factors: materials, moisture, carbon/nitrogen
balance, air flow, and temperature. Any one of these factors
can greatly affect the success of the operation and the quality
of the product.
MATERIALS
The incoming green waste is, obviously, the single most important
element in production of quality compost. At Miramar Wholesale
Nurseries, the greens that are used are a combination of grass
clippings, leaves, foliage, and wood. A staff member is located
at the dumping site to direct the waste into the appropriate
window. This is to ensure that the material is free of trash
and that the proper ratios of Carbon and Nitrogen can be monitored.
CARBON/NITROGEN BALANCE
Carbon provides energy to bacteria, fungi, and other microorganisms,
which make the decomposition process happen. The major sources
of Carbon to the compost pile are leaves and foliage, with
a Carbon to Nitrogen ratio (C:N) of between 40 — 80:1,
and woody materials with a C:N ratio of 100 — 130:1.
Nitrogen expedites population growth of these microorganisms.
Therefore, if there is too little Nitrogen, the populations
will not grow to their optimum size, slowing down the rate
of decomposition.
On the other hand, excessive Nitrogen will cause an accelerated
rate of microbial growth and rapid decomposition of the material.
This rapid decomposition will generally result in overuse
of oxygen in the pile, creating an anaerobic situation, and
serious odor problems will occur. Grass clippings are the
main source of Nitrogen in the compost pile with a C:N ratio
of 19:1. The ideal C:N ratio is around 30:1.
MOISTURE
Moisture also needs to be monitored and managed carefully.
Moisture content should never be below 40% and never above
70%. If a pile is too dry, decomposition slows because the
microorganisms do not have sufficient moisture to thrive.
If a pile is too wet, anaerobic conditions occur because the
water fills up all available pore space and does not allow
sufficient air to flow. To prevent this excessive moisture,
the pile should be turned on occasion to let the wetter material
on the bottom of the pile dry out, and to get air to the bottom
of the pile. Because of the arid climate of Southern California,
it is a good idea to make the top of the pile concave to trap
whatever moisture is available.
AIR FLOW
Composting is an aerobic process. That means that oxygen flow
is crucial to a properly functioning compost pile. If the
percent of Oxygen in the pore space falls below 10, the pile
can become anaerobic and methane gas will be produced resulting
in an odor. In a large pile, Oxygen naturally circulates through
the pile by entering through the bottom and sides, while the
hot air rises from the hot core and exits through the top.
However, it is a good practice to consistently turn the piles.
This will create a more uniform rate of decomposition, increase
temporary Oxygen to the pile, and loosen the pile to promote
better natural Oxygen flow.
TEMPERATURE
Temperature is the final element in the composting operation.
When temperatures exceed 160 degrees Fahrenheit (71 degrees
C), beneficial organisms are killed off. Below 90 degrees
Fahrenheit (32 degrees C), the decomposition process is slowed
down considerably. Ideally, temperatures should be kept between
90 and 140 degrees Fahrenheit.
The temperature in the compost pile is determined by two
factors, the heat produced by microorganisms, and the heat
lost on the surface area. After a pile heats itself, temperatures
will drop because there is less material for the microorganisms
to decompose. By turning the pile, temperatures will rise
again due to a rejuvenation of decomposable material. Therefore,
the pile should be turned as temperatures rise above 140 degrees,
or fall below 90 degrees. Eventually all of the decomposable
material will be consumed and the pile will stop heating.
Once the pile reaches a steady temperature of around 70 degrees,
the composting process is done.
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A screen sifts the compost and sorts
it into piles by size.
Compost is loaded into the screen, which sifts and sorts
by size.
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The final product is run through a screen, which separates
the particles by size. The smaller particles are put in one
pile, which is a fine organic compost that may be mixed with
soil to create a planting mix. The larger particles, a mixture
of large pieces of bark and woody materials, can be used as
a topper in planter beds, adding an attractive texture around
the base of the plants.
Composting is just one method to recycle green waste. Reducing
green waste before it is created is also beneficial. Grasscycling
is one option, but landscapers can also help reduce green
waste by educating clients before an installation project
begins. Some types of work are more wasteful than others,
such as planting a hedge or planting a tree under power lines.
Both require frequent trimming. Xeriscaping is by nature a
resource-saving technique. For more information about reducing
and/or green waste, contact the San Diego recycling department.
Brochures and other educational materials are available, as
well as advice.
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