Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
Options
island, albeit at higher cost. The decline of the sugar industry in Hawaii represents a
good opportunity to develop new energy crop farms. Although some former sugar land
has been put to new uses (such as coffee and cattle), these generally use only a small
portion of the land formerly in sugar production. As stated in a recent report, “Large
quantities of productive and well-developed agricultural lands presently exist in Hawaii
in ‘ready to plant’ condition.” 6
Energy crop options for Kauai generally consist of woody crops and grasses.
Research trials have identified banagrass as one of the more promising energy crop
options. Banagrass is a fast-growing variety of elephantgrass with yields projected to
range from 18 to 22 dry tons per acre, per year. Banagrass could be grown on land
currently zoned for agriculture and possibly also conservation land. Total land zoned
agricultural in Kauai is about 140,000 acres, although only a fraction of this is currently
farmed. 7 Banagrass has a heat content of approximately 16 MBtu/dry ton. Theoretically,
if all 140,000 acres were used to grow banagrass yielding 20 dry tons per acre per year,
approximately 2.8 million dry tons of banagrass could be harvested per year. This would
be enough to generate over 3,000 GWh/yr from a plant capacity of 440 MW. If only 20
percent of this land was available to grow banagrass (an amount equal to 28,000 acres,
less than the amount of land used for sugarcane in the mid-1990s) this would be enough
to generate over 600 GWh/yr from a plant capacity of about 90 MW. Banagrass alone
could supply all the electricity needs of Kauai, while substantially reinvigorating the
island’s agricultural industry.
There is good potential from a variety of biomass sources on the island. It is
possible to design a biomass facility to accept a diverse fuel mix, possibly even including
imported coal. Given the uncertainty about future availability of biomass on the island,
such an approach is advisable. The developable potential for biomass is summarized in
the following table.
6 Charles Kinoshita and Jiachun Zhou, “Siting Evaluation for Biomass-Ethanol Production in Hawaii”,
available at: http://www.hawaii.gov/dbedt/ert/bioethanol/ch10.html, 1999.
7 Kinoshita and Zhou.
21 March 2005 3-9 Black & Veatch