Industrial Crops and Products 11 2000 119 – 128
Different plant parts as raw material for fuel and pulp production
K. Pahkala , M. Pihala
Agricultural Research Centre of Finland, FIN-
31600
Jokioinen, Finland Accepted 8 October 1999
Abstract
Reed canary grass Phalaris arundinacea L., meadow fescue Festuca pratensis Hudson, tall fescue Festuca arundinacea Schreber and goat’s rue Galega orientalis L. were harvested at seed ripening stage and in the following
spring when the plants were totally dry. The amounts of different plant parts grasses: stem, leaf sheaths, leaf blades and panicles; goat’s rue: stem, leaf blades and pods were measured and the composition of ash, silica SiO
2
, iron Fe, manganese Mn, copper Cu and potassium K was analysed for each plant fraction. Plant species, plant part
and harvesting time affected the mineral composition; grasses contained more SiO
2
and K, but less Cu than goat’s rue. The mineral concentrations were highest in leaf blades. In each species, stem fractions had the lowest ash, SiO
2
, K, Fe, and Mn contents. The proportion of stem was highest in reed canary grass and goat’s rue when harvested in
spring. The K concentration was clearly lower in plants harvested in spring than at seed ripening stage in autumn. However, the concentrations of SiO
2
, Fe, Cu and Mn were highest at spring harvesting. Spring harvest of reed canary grass yielded clearly higher fibre contents for each plant fraction than harvesting in autumn. Of the species studied,
reed canary grass suits best for raw material, if the leaf blades are removed and harvesting is done in spring at senescence stage of plants. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Grass species; Goat’s rue; Plant fractions; Mineral composition; Fibre www.elsevier.comlocateindcrop
1. Introduction
Non-wood plant species have been found to be potential sources for fibre production Nieschlag et
al., 1960; Nelson et al., 1966; van Dam and Shannon, 1994 and raw material for energy pro-
duction Burvall, 1993. In northern Europe, espe- cially reed canary grass Phalaris arundinacea L.
has aroused interest as an energy crop Burvall, 1993; Leinonen et al., 1998 and in recent years as
raw material for paper Berggren, 1989; Paavi- lainen and Torgilsson, 1994. Also other grasses,
such as tall fescue Festuca arundinacea Schr. Janson et al., 1994, and cereal straw Atchison,
1988; Lo¨nnberg et al., 1996 can be used for paper production. In central Europe, elephant grass
Miscanthus sinensis Anderss. has been studied as a raw material for paper and energy Walsh, 1998.
Corresponding author. Tel.: + 358-3-41881; fax: + 358-3- 41882437.
E-mail address
:
katri.pahkalamtt.fi K. Pahkala 0926-669000 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 6 - 6 6 9 0 9 9 0 0 0 5 0 - 3
When herbaceous species are pulped for paper- making or used for bioenergy, most frequently,
the whole plant with all plant parts is used as raw material. Except for fibrous material from cell
walls, this biomass contains inorganic elements, which are essential or useful for plant growth and
development. However, these mineral substances have a negative effect on the pulping and combus-
tion processes, so their quantities should be as low as possible Keitaanniemi and Virkola, 1982; Il-
vessalo-Pfa¨ffli, 1995; Obernberger et al., 1997. Silicon Si, potassium, manganese, copper and
iron are harmful for the pulping process Keitaan- niemi and Virkola, 1982 and undesirable in fuel
use Obernberger et al., 1997. In papermaking, silicon wears out the installations of a factory
Watson and Gartside, 1976, lowers the paper quality Jeyasingam, 1988 and complicates the
recovery of chemicals and energy Ranua, 1977; Keitaanniemi and Virkola, 1982; Ulmgren et al.,
1990. In combustion, high alkali metal concen- trations decrease the melting point of ash and
cause deposits and damage in boilers Burvall, 1993; Obernberger et al., 1997.
The concentration of each particular mineral substance varies depending on the plant species
and the plant part Rexen and Munck, 1984; Petersen, 1988; Theander, 1991. The plant age or
stage of development when harvested and the concentration of other minerals have also a sig-
nificant influence Tyler, 1971; Gill et al., 1989; Marschner, 1995; Landstro¨m et al., 1996. The
main botanical components in a grass plant are stem nodes, internodes, leaf sheaths, leaf blades
and panicles, in legumes stem, leaves and pods or flowers, respectively. The weight distribution of
these components varies within and between plant species Salo et al., 1975; Petersen, 1988. Harvest-
ing at different stages of development also affects the stem to leaf ratio in the biomass. There are
differences in the chemical composition of stem and leaves Muller, 1960; Salo et al., 1975; Buxton
and Hornstein, 1986; Albrecht et al., 1987; Pe- tersen, 1988 which also cause variations in the
mineral content of the harvested biomass.
In the early 1990s, the Agricultural Research Centre and the University of Helsinki together
with the Finnish Pulp and Paper Institute set out to search for the most promising crop species for
raw material of papermaking Pahkala et al., 1995. In those studies, reed canary grass, tall
fescue, meadow fescue and goat’s rue were chosen for further studies, including field experiments to
determine the proper harvesting system and fertil- isation level for biomass production. The fibre
and mineral compositions of the total yields have been reported in an earlier study Pahkala et al.,
1994. In the present study, we wanted to find out whether the quality of the raw material could be
improved by screening for the plant fraction, which is most appropriate for the pulping and
combustion processes.
2. Material and methods
