There are a growing number of environmental
problems directly related to large scale production farming
methods. Europe is beginning to address many of these issues
and North America will have to follow in the very near future.
Along with the apparent expansion of certain bacterial and
viral pathogens, we are seeing serious concerns about the
growth of prionic diseases. As well, production farms produce
extreme amounts of animal manure that cannot be absorbed
into the biosphere as was the practice in earlier times.
Excessive nutriation of farm fields is leading to major
problems in watershed systems worldwide and the damage has
started to dangerously and negatively affect all oceanic
systems. Pollution from agricultural practices is quickly
catching up to industrial pollution as a primary cause of
environment degradation.
The Brookes process (U.S. patents #5,611,289
& #6,116,168, European patent EP0815392B1) is designed
to eliminate all organic structure, and thus, all potential
pathogens including prions, from a bio-mass. This system
is presently being used in Scotland to destroy bovine carcasses
and SRM material in an effort to eradicate the prion that
causes BSE (mad cow disease). This ash residual is tested
on an ongoing basis to confirm that no amino acids (the
building blocks of proteins) survive the process. Click
here for photos of the BSE units showing the carcass
material and the residual remaining after gasification.
The Brookes system can destroy materials
that are extremely wet through to wastes that are essentially
dry. BGP systems have been used to gasify wood, paper, medical
wastes, pure blood, whole animals, carcass material and
most recently, pig manure. The units can be custom sized
for large scale operations (20 metric tones)
PROCESS DESCRIPTION
The following gives more detailed information
specifically related the application of this technology
to animal carcasses,
The proposed waste material is maccerated
or ground-up animal, meat and bone meal, and other possible
wastes from the rendering process. In all cases, each batch
of waste will be pumped into the gasifier through ports
in the top of the primary chamber.
The one design capacity would be for 10
tonnes of macerated animals per cycle with a cycle time
from load to re-load of approximately 24 hours. The cycle
time may vary somewhat depending on the type and condition
of the animals and their fat content. The load capacity
for other materials will be different and will depend on
the density and the energy content of the waste.
The basic process is as follows;
A batch of waste is pumped into the sealed
primary chamber (P.C.). The secondary chamber burners are
on during the loading procedure and the set point temperature
in the secondary chamber is a minimum of 850 C. The dwell
time is adjustable, but for this type of material in most
jurisdictions require 2 seconds. This is determined by the
position of the thermocouple related to the maximum velocity
of the gases as they travel through the secondary chamber
(S.C.).
Immediately after the waste has been loaded,
the P.C. temperature is somewhat above ambient. It climbs
slowly over a period of about 12 to 14 hours until it eventually
reaches or exceeds the secondary chamber set point. The
waste is essentially evaporated (gasified) by direct heat.
The maximum gasification rate for the macerated animal load
is 850 kg/hr. The secondary chamber is designed for this
maximum flow condition.
When the waste is first loaded into the
P.C. the temperature is cool and the gasification rate is
low. As the P.C. temperature rises the gasification rate
increases to about the maximum. After the hydrocarbons are
evaporated out of the material the cycle is close to complete.
The remaining phase is called the carbon cycle and this
occurs when the P.C. temperature is peaking. At this point
the carbon is being removed from the ash residual bleaching
it to a greyish white colour. This stage of the process
eliminates all complex organics from the ash leaving it
inert and free of any possible infectious agents including
prions.
During the gasification process the off-gases
or fume travel into the mixing chamber and then into the
afterbuming section of the S.C. The S.C. burners modulate
to hold the temperature at the set point while excess air
is added to cause oxidation of the fume. The fume predominantly
consists of hydrocarbons which oxidize to form carbon dioxide
and water. This is an exothermic reaction and in the Brookes
system this process occurs immediately under the P.C. It
is this energy from the oxidation reaction that helps heat
up the P.C. This approach allows for a very stable and predictable
combustion process and a very fuel efficient method to completely
destroy the organic content of any potentially biohazardous
waste. Note that during the main gasification stage the
secondary chamber burners are modulated to a very low fire
position. The energy driving the process is almost exclusively
derived from the waste.
Because this is a very quiet method whereby
the waste mass is virtually undisturbed, the particulate
emissions are almost negligible. Also, the special design
of the Brookes secondary chamber gives very high resolution
oxidation so that the CO and VOC levels are extremely low.
This helps to prevent the formation of pesticide structures
such as dioxins and furans.
Once the gasification process is completed
the system will automatically shut down and initiate a cool
down cycle. The ash is removed by a vacuum system after
which the burners are restarted and the unit is re-loaded
for the next cycle.
The main advantages of the Brookes
process are;
o Minimal particulate emissions.
o Very low CO and VOC emission levels.
o No odour (closed loop process).
o Inert and harmless ash residual containing no potential
infectious agents.
o Excellent fuel efficiency.
o Minimal maintenance due to the simplicity of the system.
