Compost Feedstock
The Second Nature Compost Facility accepts processed yard trimmings
(mulch) from the SWA's
Woody Waste Recycling
Facility and wastewater residuals from the City of West
Palm Beach and others. The mulch is transported to the compost
facility by 100-cubic-yard tractor trailers
(similar to the ones used at the transfer stations) and discharged onto
the tipping floor area.
Wastewater residuals are delivered to
the compost facility in 30-yard tractor trailers with
dump bodies. SWA Compost Operators receive the wastewater
residuals and load all delivered mixed residuals and mulch into the
compost reactors during the same workday.
Next to the tipping floor is the mixing
area where the processed yard trimmings and wastewater residuals are
combined to produce the feedstock mixture. Two stationary batch
mixers (capable of handling approximately 16 cubic yards of material
at a time) stand side by side. Typically, the operator mixes a 50:50
yard trimmings/residuals combination (by weight) in the batch mixer
to obtain a targeted final mixture.
Once the feedstock mixing is completed,
it is individually fed into one of the 36 compost reactors using
a rubber tire loader.
Each of the 36 composting reactors is
separated into six aeration zones. They vary in length, with
shorter zones toward the mixing end where the composting process is
initiated. Each zone of each reactor is designated a single
temperature sensor and a single aeration blower to allow individual
temperature control and aeration. The zones are designated with
letters beginning with "A" and proceeding through the alphabet from
the mixing end to the finished end. Process control includes
continuous temperature monitoring and automatic control of the
aeration system.
There
are nine agitators in the compost facility that enhance the
composting process by turning and moving the material through the
compost reactor. The agitators move on tracks mounted above the
reactors to allow them to service every zone in each reactor. Each
agitator services 4 reactors and the material is turned at least once every
day.
The compost facility utilizes three
12,000 square-foot “biofilters”, each servicing 12 reactors.
The biofilters contain a media that consists of a 4-foot deep mixture of 50%
southern pine chip and 50% southern pine mulch, with 6 inches to 1
foot of southern pine mulch on top to optimize moisture conditions.
The exhaust air from the compost building is passed through the
biofilters to eliminate odors.
The composting system is equipped with an exhaust system that
ventilates the interior of the enclosed compost building. Twelve, 60-horsepower fans control the
movement of odorous air from the compost facility to the biofilters.
The
compost mix remains in the bays for a minimum of 14 days (during the
summer retention may be as long as 21 days). The compost facility
has a curing area, screening system, and product storage area.
Finished compost remains on site for a minimum of two months, during
which time it is tested
for pathogens, vector attraction reduction and stability.
Stability, monitored with carbon dioxide respiration testing, shows
a stable to very stable rating upon discharge from the bays.
Stability tests on the product when it is actually distributed show
similar results. The SWA's compost meets
federal and state standards for unlimited use.
Summary
The SWA composting facility is an excellent example of the best of
all composting systems incorporating windrow/in-vessel and static
pile (air going through material) technologies. In 1994, the Second
Nature Compost Facility received the American Society of Mechanical
Engineers Award for Resource Recovery.
For information pertaining to bulk
sales please contact Mr. Mike Russell by email
or phone 561.640.4000 x4890.
The Authority would love to have the
opportunity to make this quality product available for your bulk
needs.
Composting at Home
SWA Distribution Procedures
Back to
Composting
