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The
project is a 15 MW biomass waste-to-energy
plant to be located at a sugar mill in the
southwestern portion of the country where
the electricity transmission system is
well established. The plant will be owned
and operated by Biomasa-Generacion
Nicaragua for the purposes of generating
electrical power for sale to ENEL. The
primary fuel for the plant will be bagasse
from an existing sugar mill, with residual
biomass from within the region used to
supplement the fuel supply. This residual
biomass will come from sources that are
plentiful throughout the region,
particularly logging residues, sawdust,
and waste wood. During the sugar cane
off-season, the deficit of biomass
feedstock will be offset by a dedicated
biomass energy crop so that gross power
output will remain constant throughout the
year. The project is expected to reduce
approximately 2.3 million metric tons of
CO2 emissions equivalent over the project
life (20 years).
The
two sugar mills being considered for the
Bio-Gen Nicaragua project have capacities
of 7,000 and 12,000 tons of cane per day.
Bagasse is generated in great quantities
in sugar processing, with about 30% of the
harvested sugar winding up as bagasse
after it is crushed. Since all sugar mills
require electric power and steam, they
generally burn the bagasse (very
inefficiently) in order to meet their
energy requirements. The Bio-Gen Nicaragua
plant will burn the bagasse in a highly
efficient manner, thus generating excess
power that will be sold to the public
utility to help meet Nicaragua?s growing
energy demand.
The
woody biomass used as a supplemental fuel
will come from various stages of the
timber and wood products industries. Wood
waste from timber harvesting is generally
left behind in the forest, where it can be
collected and transported for use as a
fuel for the project. Solid pieces of
residual waste from saw mill operations
are also widely available, but have other
competing uses and are subsequently more
expensive. Unlike the larger saw mill
wastes, sawdust is a serious disposal
problem for most saw mills and thus can be
purchased cheaply as a fuel source.
Based
on a detailed fuel study and conservative
assumptions, the two potential project
sites have between 300,000 and 600,00 tons
per year of biomass waste available within
an economic hauling radius. Long-term
contracts for the supply of biomass wastes
and for the harvest from an energy crop
such as eucalyptus will ensure adequate
fuel availability and a stable fuel cost,
and a Power Purchase Agreement between
Bio-Gen Nicaragua and ENEL will guarantee
revenues.
At
the waste processing facility, fuel will
be dropped into a receiving hopper and
conveyor where it will pass through an
electro magnet to remove ferrous scrap
materials. Fuel will then be passed
through a screen which will separate
larger pieces of fuel for processing into
the correct size. Accepted fuel will be
funneled through a chute and spread evenly
onto a conveyor. A covered fuel house will
provide short-term storage (approximately
24 hours) and overflow will be transported
to a long-term storage pile. The fuel
preparation system will be designed to
supply the plant with fuel for continuous
operations at 110% load.
The
plant is expected to operate for a minimum
of 7500 hours per year, combusting wood
waste to generate electricity for sale to
ENEL. The proposed boiler will be designed
for 155,000 pounds per hour of steam at
750 psig, 830 °F at the superheater
outlet. This steam flow expands through a
multi-stage turbine, condensing under
vacuum and driving a 15 MW net generator.
Electricity will be sent to and from the
plant via transmission lines
interconnected with the existing ENEL
transmission system.
Many
operating saw mills in Nicaragua burn
their unusable waste with low constant
fires that release uncontrolled air
emissions, and it is common practice to
locate these piles at the edge of natural
water courses, contaminating them as well.
Thus, current disposal practices damage
the environment and represent the loss of
a valuable indigenous fuel resource. The
Bio-Gen Nicaragua project will help the
region around the site to address these
issues, with the exception of the energy
crop that is deliberately planted to
generate an additional fuel supply, none
of the biomass feedstock will come from
trees cut specifically for electrical
power generation. Instead, the project
will provide reliable electric power
through the efficient use of a valuable
but untapped indigenous fuel source.
Furthermore, the added generation capacity
will offset the need to build additional
power plants, many of which are utilizing
highly-polluting and carbon-rich fossil
fuels. |
