Proceedings World Bioenergy 2010

USE OF ASHES AS A FERTILIZER IN REED CANARY GRASS (PHALARIS ARUNDINACEA L.) GROWN AS AN ENERGY CROP FOR
94 world bioenergy 2010
COMBUSTION
Eva Lindvall
Swedish University of Agricultural Sciences, Department of agricultural research for northern Sweden,
901 83 UMEÅ, Sweden
eva.lindvall@njv.slu.se
ABSTRACT: Use of reed canary grass (RCG) as biofuel for combustion produces relative high amounts of ash. Deposition
cost of ash negatively influences the economy of RCG production and is not very environmentally friendly. Therefore it
is of importance that RCG ashes, pure or in mixtures, can be recycled to the RCG field as a part of the nutrient supply.
Results from this field trail do not show any negative effects on crop or soil caused by the ash.
Keywords: reed canary grass, ash, heavy metals
INTRODUCTION
Reed canary grass (RCG) has been considered as the
most interesting perennial grass for energy purposes in
Sweden. RCG is high yielding and the root system is very
large which enables the plant to very efficiently absorb
nutrients from the soil. Stands of perennial grasses can
have a lifetime of more than 10 years and therefore
require less cultivation and have lower requirement of
pesticides (Wrobel et al, 2009, Kätterer & Andren, 1999).
Some of the machinery required for grass cultivation is
already available on many farms. Perennial grasses have
lower nutrient requirements than annual bioenergy crops
as some of the nutrients used of the shoots can be
remobilized to the roots during autumn.
One disadvantage when using RCG as biofuel for
combustion is the relatively high ash content (Burvall &
Hedman, 1994, Burvall, 1997). Deposition cost of ashes
negatively influences the economy of RCG production
and is not very environmentally friendly. Therefore it is
of importance that RCG ashes, pure or in mixtures, can
be recycled to the RCG field as a part of the nutrient
supply.
MATERIAL AND METHODS
One concern when using ash and other waste products on
agricultural land is the risk of enrichment of heavy metals
in the circulation from soil to plant and ash. A field trial
was established at SLUs field station in Umeå, Sweden in
the spring 2002. Three different fertilizer treatments were
applied. Treatment A was fertilized with an ash from
combustion of RCG together with municipal wastes,
treatment B an ash from RCG only and for treatment C
was only commercial fertilizers used. The total amounts
of nutrient each year applied in the trial were 100 kg ha -1
N, 15 kg ha -1 P and 80 kg ha -1 K. The amount of ash in
treatment A and B was calculated from the chemical
analysis of the ashes to be equal to the required amount
of P. The required amounts of N and K within these
treatments were complemented by commercial fertilizers.
The trial was harvested each spring from 2003 to 2009.
RESULTS
The dry matter yield showed large variation between
years but no significant differences between treatments
were detected. Samples of grass and soil have been
analyzed for heavy metal content some of the years. No
significant differences between the treatments were found
in the grass. When comparing samples from 2004 and
2009 the content was lower for most elements in 2009,
only Zn showed a significant higher level. Soil samples
were taken from 3 levels; 0-5 cm, 5-10 cm and 10-20 cm.
In the uppermost level there are significant differences
between treatments for Cd, Pb and Zn, with higher
contents in treatment A. The differences between levels is
mainly small, and compared to results from 2003 there
seems to be no tendency to enrichment during this period
of time.
CONCLUSIONS
We can conclude that the ash we used does not seem to
cause any harm to the growth of RCG, content of
undesired chemical elements in grass and soil and can be
used as a complement to commercial fertilizers.
ACKNOWLEDGEMENTS
This project was founded by The Swedish Energy
Agency through Värmeforsk (Thermal Engineering
Research Institute) and Bioenergigårdar i ett nytt
landskap, a project administrated by Västerbotten County
Administrative Board and financed by Kempestiftelserna
among others.
REFERENCES
Burvall J, 1997. Influence of harvest time and soil type
on fuel quality in reed canary grass (Phalaris arundinacea
L). Biomass Bioenergy 12, 149-154.
Burvall J. and Hedman B, 1994. Bränslekaraktärisering
av rörflen - resultat från första och andra års vallar.
Röbäcksdalen meddelar 5, 1-27. (in Swedish)
Kätterer T. and Andren O, 1999. Growth dynamics of
reed canarygrass (Phalaris arundinacea L.) and its
allocation of biomass and nitrogen below ground in a
field receiving daily irrigation and fertilisation. Nutrient
Cycling in Agroecosystems 54, 21-29.
Wrobel C., Coulman B.E. and Smith D.L. 2009. The
potential use of reed canarygrass (Phalaris arundinacea
L.) as a biofuel crop. Acta Agriculturae Scandinavica
Section B-Soil and Plant Science 59, 1-18.