Florida-based Biomass Investment Group (BIG), is embarking on a project using Arundo donax as an energy crop that will be grown on 20,000 acres (8000ha). The biomass will be converted into bio-oil, a heavy fuel oil, via a fast-pyrolysis process (for more on this process see previous post). This carbon-neutral oil will then be used in a power plant that will provide electricity to some 80,000 Floridian households.
The following points summarize the project:
-- Arundo donax, also known as the 'Spanish cane' is a giant reed native to the Mediterranean. Originally the grass species adapted from subtropical climates but is now found in Cool Temperate Wet through Tropical Dry to Wet Forest Life Zones. It arrived in the U.S. more than a century ago and was planted to control erosion in California stream beds. Since then, it has become a noxious weed in some zones, with large campaigns aimed at eradicating it.
-- The grass species is very hardy and needs virtually no fertilizers, nor any other means of protecting the crop with herbicides during its growth.
-- The grass's bamboo-like stems can grow up to 6 metres in height (18ft). Arundo is strongly rhizomatous which results in dense patches. Dry matter yields of up to 50 metric tonnes per hectare have been recorded and 75 tonnes in the tropics, but 25-30MT/ha is a more realistic estimate for average yields in more temperate climates (see the plant profile in The Handbook of Energy Crops).
--Assuming a dry matter yield of 30MT/ha/yr, at a gross heating value of 17.1GJ/tonne (see the Bioenergy Feedstock Characteristics at the ONRL's biomass website), then a hectare of Arundo yields around 84 barrels of oil equivalent. Grown in the tropics, twice that amount can be obtained.
-- BIG will grow about 20,000 acres (8000ha) of Arundo on a Florida farm. It will then convert the biomass into a liquid fuel (pyrolysis oil), and burn it in a gas turbine. The waste heat from the turbine exhaust then produces steam that churns out additional electricity in a steam turbine.
-- The resulting energy will be enough to power 80,000 homes on a continuous basis. Whitfield says the production process increases the facility's efficiency two-fold above current biomass methods. That will make it on target to produce energy at prices below what a conventional plant might produce.
-- Bob Niekum with Progress Energy Florida says the reed-driven energy facility will be carbon neutral — that is, it will have no net output of carbon dioxide, known to contribute to greenhouse gases.
Niekum says most environmental groups favor the project. But the Florida Native Plant Society and a other groups oppose it: Niekum and BIG say the reed's growth is easy to control, with a simple ditch around the farm. But Roger Anderson at Illinois State University isn't so sure. He says the giant reed can spread easily, clog waterways and even be a fire hazard. Anderson says many species proposed as biomass crops, including Arundo, are potentially invasive plants.
Source: Biomass Investment Group to plant Arundo donax for electricity, Biopact, Dec. 7, 2006