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ANDRITZ MeWa installed a Bio-QZ pretreatment
system at the Unterer Lindenhof research station
in Germany (shown here). After several months of
operation, the results showed very positive results:
an increase in specific methane yield of up to 40%
when using Bio-QZ pretreatment in front of the
fermentation process.
FEED IN,
electricity out?
Study confirms potential for horse
manure as biogas source.
This article may just give new meaning to
the term “natural resource.” A research
project funded by the BMU (the German
ministry of the environment, nature conservation, construction, and nuclear safety)
at the University of Hohenheim (Stuttgart)
uncovered the potential of the “natural resource” horse manure as a source for biogas production. This perhaps offers biogas
plant operators an interesting alternative for
an additional resource stream.
How big is that stream? In Germany alone
there are an estimated 8,000 biogas plants.
There are also about one million horses
“generating” about 15 million tonnes of
manure. A small part of this is put on fields
as fertilizer – the rest is incinerated just to
get rid of it. Disposal is a challenge for horse
farms and local operators.
Aids biodiversity
Most biogas plants are using corn silage as
the “fuel” due to its availability and energy
content. NGOs the world over have pointed
out that too much corn is being cultivated,
creating a lack of biodiversity. While horse
manure contains only 60% of the energy of
corn silage, it offers certain advantages. For
example, if the 15 million tonnes of German
horse manure were converted to biogas,
80,000 ha of corn could be replaced.
The research team at Hohenheim was led
by Dr. Hans Oechsner. The team concluded
that incinerating horse manure was a great
waste of a natural resource. Using it as
fertilizer also negates the calorifi c value.
Their suggestion was to use the manure
to produce biogas. After all, pig, cow, and
chicken manure have all been successfully
employed as fuel for biogas plants, why not
horses?
The projections are actually quite interesting. The annual “output” of a single horse
can cover the electricity requirements of a
three-person-household. That means the
one million horses of Germany could be
electrifying about one million households.
Not bad.
Overcoming the challenges
While horse manure offers potential as a
biogas source, it can only be exploited with
the proper pretreatment. And, that is where
ANDRITZ MeWa comes in.
handle the fibrous material, and consumes
more power for the recirculation process.
Horse manure is composed of about 50%
straw (from partially digested feed and also
the bedding in the stables that gets intermixed with the manure). This straw has a
high lignin content making it difficult for the
standard enzymes in a biogas plant to digest and ferment the straw. This requires
extremely long residence times in the fermenter. The density of the material makes
it more difficult for biogas to rise into the
dome of the biogas plant. Also, the agitator
in the fermenter has to be more rugged to
The ANDRITZ MeWa Bio-QZ is adept at
preparing raw materials, including horse
manure it turns out, for the fermentation
process. More than 100 farms and municipalities use the Bio-QZ. It was originally designed for recycling electrical and electronic
waste, which means it is very rugged. Its
principle of operation is like a kitchen mixer
– only on a much larger scale. Incoming raw
material is crushed by chains which rotate
around a vertical axis at about 1,200 rpm.
The filling, crushing, and retention time can
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be adjusted to optimally pretreat every conceivable material.
Pretreatment and yield
A Bio-QZ was installed at the Unterer
Lindenhof research station in Germany in
front of one of the two fermenters at the
station. This was done for comparison purposes, so data could be collected on the
gas yield obtained from fermenter only and
a fermenter equipped with pretreatment.
Feed and composition of the incoming raw
material was identical.
After several months of operation, the results showed very positive results for the
pretreatment and fermentation configuration.Scientists measured an increase in
specific methane yield of up to 40% when
using the Bio-QZ.
The mechanical pretreatment of the horse
manure crushes the straw to the extent
that the agitator can dissolve the “cover”
in the fermentation tank so that biogas can
release freely. The impact of the chains on
the straw breaks up the lignin so that the
enzymes can carry out their fermentation
work without long residence times.
Three years of operational experience at
Unterer Lindenhof show that the Bio-QZ
reliably treats traditional – and newer nontraditional raw materials. The research continues to establish empirical values for these
non-traditional materials to gather insight,
identify potential for improvement, and ultimately restore the diversity of nature.
Horse manure is composed of about
50% straw, making it difficult for the
standard enzymes in a biogas plant
to digest and ferment the straw.
Pretreatment is required.
CONTACT
Claus-Peter Boor
[email protected]
The ANDRITZ MeWa Bio-QZ is adept at preparing raw materials for fermentation. It operates like a giant kitchen mixer. Incoming material
is crushed by chains which rotate around a vertical axis at about 1,200 rpm. More than 100 farms and municipalities use the Bio-QZ.