Page 126 - Materials Chemistry, Second Edition

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Sustainable Development and Industrial Ecology
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purified wastewater as well as its cooling water to the Asnaes power station, it
thereby saved a total of 3 million cubic meters of water per year (instead of
2 million) as the same water was being “used twice”. In 1976, the Novo Nordisk
plant started materials flows by supplying sludge from its processes as well as
from the fish farm’s water treatment plant to be used as a fertilizer for a nearby
farm. This sludge exchange totalled over 1 million tons per year. In addition,
surplus yeast from the produced insulin was sent to farmers as animal food.
Enzyme production is based on fermentation of raw materials such
as potato flour and cornstarch. The fermentation process generates about
150,000 cubic meters of solid biomass as well as 90,000 cubic meters of liquid
biomass. Through proper repositioning of this waste, farmers have been using
it as fertilizer, thus reducing the consumption of commercial fertilizers.
Another waste transformation is the yeast which is used in the pro-
duction of insulin. Through the addition of sugar water and lactic acid it is
converted into animal food. The insulin production builds on a fermenta-
tion process in which some of the main ingredients are sugar and salt, which
are converted into insulin by adding yeast. After a heating process, the yeast,
a residual product in this production, is converted into a much appreciated
feed: yeast slurry. Sugar water and lactic acid bacteria are added to the yeast,
making the product more attractive to animals (800,000 pigs).
The Asnaes power station is coal fired and operates at about 40% thermal
efficiency producing huge amounts of energy. It uses salty seawater for its
cooling needs saving the Lake Tisso water, and at the same time supplies the
heated seawater to the 57 nearby fish ponds producing 200 tons of trout and
salmon on a yearly basis.
In 1981, Asnaes began to supply the districts with steam for heating
which replaced about 3,500 oil furnaces and significantly reduced air pollu-
tion. In addition, it provided steam to both Novo Nordisk and Statoil for
their heating processes. After Statoil treated its excess gas by removing sul-
fur to comply with regulations on sulfur emission, it became possible to use
the gas at the Asnaes power plant. Statoil’s desulfurization plant reduces the
sulfur content of the refinery gas whereby SO 2 emissions are reduced signif-
icantly. The byproduct is ammonium thiosulphate, which is used in the pro-
duction of approximately 20,000 tons of liquid fertilizer roughly corresponding
to the annual Danish consumption.
In 1992, the Asnaes power plant began using the treated gas from Statoil
in place of coal. Statoil also supplies gas to Gyproc as its source of energy. In
addition, the removed sulfur is sold as a raw material for the manufacture of
sulfuric acid at Kamira. In 1993, the Asnaes power station added a desulfur-
ization unit that removes sulfur from its gases and produces calcium sulfate
as waste which is known as synthetic gypsum. The desulfurized fly ash is used
by a cement company while gypsum is supplied to Gyproc as the main raw
material for the manufacture of plasterboard instead of importing natural
gypsum from Spain. In 1998, approximately 190,000 tons per year of synthetic
gypsum were available from the power station.