The capitula of Cynara cardunculus contain hairs and pappi representing 7% of the total plant
biomass. These low density biomass components could be mechanically separated without
apparent losses using a whole-plant processing prototype. Hairs and pappi are filamentous
structures made up of longitudinally aligned fibre cells, without intercellular voids or pitting,
with the following dimensions regarding length, width and wall thickness: 1.35mm, 19.8,
and 4.8 m for hairs and 1.78mm, 10.4, and 2.9 m for pappi. Chemically hairs and pappi
have low content of ash (1.9% and 1.1%, respectively), extractives (5.4% and 6.0%) and lignin
(10.6% and 17.8%), and high content of holocellulose (77.5% and 72.8%) and -cellulose (55.2%
and 46.8%).
Pulps could be produced using a conventional kraft process with high yields and low
residual lignin, e.g. 63% at Kappa 7 for hairs and 48% at Kappa 11 for pappi, low coarseness
values (0.04 and 0.03mgm−1) and adequate pulp properties for paper (40 and 42Nmg−1
tensile index; 3.6 and 3.4 kPam2 g−1 burst index in unrefined pulps of hairs and pappi,
respectively). The results also indicated that there is scope for improving pulp quality by
optimising pulping conditions to this type of new raw materials. The differences between
hairs and pappi may also be further exploited namely the lower lignin content of hairs and
the higher slenderness and wall thickness of pappi fibres.
The utilization of hairs and pappi may strengthen the differentiated use of biomass fractions
of the Cynara plant and its potential as a bioenergy crop
