According to the United States
Environmental Protection Agency
(EPA) and various large municipal
solid waste agencies, green
waste such as yard trimmings,
arborist cuttings and food
residuals constitute from
25 to 30 percent of the American
municipal solid waste stream.
That’s a lot of biomass going
to landfills that could otherwise
become useful, environmentally
beneficial compost, or feedstock
for ethanol production.
Green waste is widely used at
landfills as alternative daily
cover (ADC) as a substitute
for dirt and other material.
But there are many options
for ADC. For example, besides
green waste and compost, California’s
Integrated Waste Management
Board (CIWMB) approves ash
and cement kiln dust, treated
auto shredder waste, construction
and demolition waste, contaminated
sediment sludge and shredded
tires for ADC.
There are no current CIWMB restrictions
on landfilling with green
waste or using it as ADC,
but regulations are in place
to reduce landfill organics
by 50 percent by 2020. Landfill
operators in California are
only supposed to apply an
appropriate amount of green
waste at the end of the day
to cover garbage on the working
face of the landfill. Thickness
requirements are aimed at
reducing the abuse of green
waste as ADC.
Because green waste has high
carbon value, the last place
it should go is into landfills.
Composting green waste offers
the benefits of resource efficiency
by creating useful, natural
fertilizers and soil improvement
characteristics. High quality
compost is in high demand by
farmers because of growing consumer
demand for organic foods – people
who want to avoid ingesting
foods treated with chemical
fertilizers and prevent the
runoff of destructive chemicals
from farmlands into the water
supply.
But there are emerging national
problems associated with large-scale
municipal composting. In California,
the apparent worldwide leader
in implementing environmental
regulations, we may be seeing
the forerunners of composting
regulations to come in other
states. “Composting is starting
to be regulated by our Air Resources
Board because of the smell and
by the Water Board due to concerns
over ground water contamination,”
said compost information specialist
Charlene Graham at CIWMB. In
addition, air quality regulators
such as the South Coast Air
Quality Management District
and the San Joaquin air district
have rules that require the
reduction of volatile organic
compounds and ammonia which
are typically emitted from composting
operations.
Besides these concerns, even
the best managed outdoor composting
operation is challenged to achieve
and maintain temperatures over
131 degrees Fahrenheit throughout
the pile to ensure that all
seeds and pathogens are killed.
High quality compost has value,
while lower quality compost
has lower value.
That’s why the Inland Empire
Regional Composting Facility
(IERCF) in Rancho Cucamonga,
California may be a prototype
for the future of municipal
green waste and biosolids composting.
It’s all indoors and produces
consistent, high quality compost
which is in high demand within
its marketplace. And because
emissions are tightly controlled
with the use of a biofilter,
a plant of this type can be
located in an urban area, thereby
reducing trucking expenses to
remote sites.
IERCF’s 454,000 square-foot
facility (a former IKEA warehouse)
is fully enclosed and equipped
with a high tech air filtration
system. Its roof has a one megawatt
photovoltaic installation that
provides about half of the plant’s
electricity. Water used for
the composting process is supplied
by the adjacent Inland Empire
Utilities Agency’s recycled
water program. After water is
used for composing it is piped
back for re-treatment and re-use.
Thus, air and water problems
are solved and the solar system
significantly reduces its carbon
footprint, making it a synergistically
green recycling solution.
The plant is located in San
Bernardino County in a heavy
industrial section, just west
of Los Angeles County, and draws
its green and wood waste feedstock
from a 60-mile radius. Biosolids
come from the Inland Empire
Utilities Agency and the LA
County Sanitation District,
the partners that operate the
facility. Green waste consists
of brush, trees and yard trimmings,
bedding straw supplied by horse
stables and from municipal material
recovery facilities, as well
as tree and lawn services.
Annually, IERCF is now processing
approximately 60,000 tons of
green waste and 150,000 tons
of biosolids to produce 90,000
tons of high quality compost.
Biosolids consist of treated
wastewater, essentially water
and nutrients. “Green waste
is critical to our composting
process. To have a balanced
compost heap you have to have
carbon, nitrogen and oxygen.
The wood provides the porosity
for the oxygen to move into
the pile and the carbon makes
for a good carbon-to-nitrogen
ratio for the compost,” said
Jeff Ziegenbein, deputy manager
of Operations for IERCF.
To avoid smelling up the neighborhood,
biosolids, wood and green wastes
are delivered by tarp-covered
trucks that are unloaded indoors
after the loading dock doors
are sealed. Composting is done
through the EPA-approved Aerated
Static Pile (ASP) composting
method that mixes materials
in large piles, rather than
in traditional windrows that
places material in long piles
where they decompose naturally
over a period of several weeks.
With ASP, air is pulled through
the composting material during
a four-step process of mixing,
active composting, screening
and curing. Air is constantly
circulated through a massive
biofilter to remove odors and
regulated compounds before it
is exhausted to the atmosphere.
Up to 12 air changes per hour
occur within the facility. Exhaust
fans are automatically controlled
by temperature sensors in the
piles.
The IERCA plant also incorporates
recycled wood in its biofilter
system. This consists of 50,000
cubic yards of a special blend
of wood chips covering a 3 acre
area, approximately 8 feet deep.
The wood chips are placed on
a perforated, ground level floor.
Air is piped into the perforated
floor where it slowly passes
through the media before exhausting
to the atmosphere. Every two
to four years the wood chips
in the biofilter are replaced.
The wood blend is a combination
of fruit and nut tree woods
and recycled wood from trees
destroyed by bark beetles. A
sprinkler system above the filter
keeps the wood chips wet. Air
handling pipes constantly suck
air from the facility into a
giant header, 12 feet in diameter
and 1,000 feet long located
under the biofilter. “Inside
of the composting building it
smells like compost, but you
can walk by the biofilter and
there is no perception of odor,”
Ziegenbein commented. The air
is then pushed through the eight-foot
layer of damp wood chips where
it is treated before being exhausted
into the atmosphere. Air emissions
are monitored by the South Coast
Air Quality Management District,
which has some of the most stringent
air quality standards in the
country. Plant operations are
also inspected by Cal EPA and
the California Integrated Waste
Management Board.
Active composting takes approximately
22 days before the pile is screened
and moved into curing. Larger
pieces screened from the compost
are recycled back to the mixing
operation and processed again.
During curing, which takes between
30 to 38 days, the material
stabilizes and is ready for
distribution. Load out of finished
compost is also done indoors
in a sealed environment.
“Our high quality compost is
wholesaled out in bulk to about
75 local customers who use the
product as a soil conditioner,
a top dressing or bag it,” said
Ziegenbein. The product is sold
under the name SoilPro Premium
Compost (a brand name registered
by IERCA) in retail outlets
such as Home Depot. It also
has many commercial turf applications,
such as for golf courses and
soccer fields. According to
Ziegenbein, SoilPro is a well
decomposed, stable and weed-free
source of organic matter containing
a full spectrum of micro-nutrients
necessary for healthy plant
growth, and has a pleasant earthy
odor. Unlike many composting
operations, SoilPro appears
to be supported by a well designed
marketing plan with distinctive
logotype, detailed product information
for resellers, including a guaranteed
minimum nutrient analysis, a
list of product benefits and
application coverage data.
“The good news about our operation
is we use all recycled water,
a significant portion of renewable
energy and the compost has a
high value that’s helping our
rate payers,” Ziegenbein said.
Before IERCA opened this plant,
it trucked biosolids from Southern
California to Arizona where
it was applied on farms raising
non-food crops such as cotton.
Besides reducing high trucking
expenses and related transport
pollution, IERCA now has a value-added
product that has had all weed
seeds and pathogens destroyed
in the composting process. SoilPro
can be used for non-food as
well as food crop applications.
By using high quality compost,
growers can reduce or eliminate
the use of chemical fertilizers
that have high solubility that
tend to leach into groundwater
and contaminate it with phosphates,
nitrates and other harmful chemicals.
Since SoilPro compost is a wood-based,
nutrient-rich soil conditioner
it can be used in a variety
of applications to provide many
benefits. While its primary
mission is to improve soil quality
and plant growth, it helps controlling
sediment runoff and erosion
and revitalizes compacted or
sandy soil. Compost also benefits
water conservation by acting
like a sponge, holding water
until plants need it.
The real cost driver for IERCA
is treating biosolids, but the
plant needs the appropriate
amount of green waste to do
it properly. IERCA can work
with MRFs if they can separate
out a clean, green stream that
works in its operation. More
operations like IERCA can allow
MRFs to have another reliable
recycling outlet that helps
keeps green waste out of landfills.
“We are a test case. We believe
this type of operation can be
located in many urban areas.
Right next to us we have a very
large correctional center. That’s
rather challenging because you
have a lot of people who don’t
want to be there in the first
place. If we had odors or complaints
about health concerns, they
could become a tough neighbor.
But we have had zero issues
because we have a very good
biofilter with a team monitoring
it to ensure that it functions
properly with no odor issues.
We’ve had no complaints. Something
like this could be sited almost
anywhere,” Ziegenbein concluded.
