Abstract

Preserved wood is commonly found in solid waste. Among the different types of
preserved wood, CCA wood has received much attention due to the scale of usage and its
significant role in soil and water contamination after disposal. As the ash of CCA wood is
hazardous, it cannot be burned, and the best available disposal method is thus landfilling.
Leaching of the metals from disposed CCA wood in landfills pollutes the environment.
To reduce the contamination of CCA, treatment before landfilling is required.
Nowadays, ethanol is seen as a promising source of energy. Lignocellulosic materials
such as wood are resources for ethanol production. This research focuses on the
possibility of producing ethanol from CCA wood. It suggests that production of ethanol
will not only be a solution to the disposal but will also generate a clean fuel.
The results showed the existence of copper, chromium and arsenic did not have a
negative effect on the fermentation, and producing ethanol from CCA wood is feasible.
The copper removed by sulfuric acid completely precipitated during the hydrolysis and
iv
neutralization. In addition about 50% of the chromium (VI) and also 60% of the arsenic
(V) were removed from the leachate by yeast during fermentation.
TCLP tests of the hydrolyzed wood leached less than 4 ppm of arsenic while minimal
amounts of chromium and copper remained in the hydrolyzed wood which makes
landfilling of hydrolyzed wood acceptable.
Baker's yeast behaves selectively by uptaking arsenic (V) and chromium (VI) but not
arsenic (III) and chromium (III). There is competition between copper and chromium
sorption by yeast. The kinetic model for removal of copper and chromium is a zero order
model while the appropriate model for uptaking arsenic by yeast is a first order model.
The kinetic models confirm that there are different mechanisms of uptaking metals by
yeast, a diffusion mechanism for removal arsenic and a surface adsorption mechanism for
copper and chromium.
As an overall conclusion of this study, using discarded CCA wood as the feed for ethanol
production is a sustainable method for disposal of CCA treated wood.