16
Hemp or wood: potential substitutes
V.S. Krotov
The Ukranian Pulp and Paper Research Institute, 18/7 Kutuzovstreet, Kiev 252133, Ukraine
Introduction
Three major factors
are restraining the development of the pulp and paper industry of Ukraine:
1. The capital costs for the construction
of new production facilities are high, with payback time often exceeding the normative
service life of the main process equipment.
2. The current obsolete equipment causes
environmental problems, as it has a high consumption of raw materials, water and energy
and a relatively low yield of finished products. Over 10 % of the raw materials, the
pulping chemicals, and almost all bleaching agents are discharged into the environment.
3. Ukraine is sparsely wooded, and a lack
of traditional raw materials hampers the development of its pulp and paper industry.
Forests take up only 13.2 % of its territory, and logging covers about one third of
its pulp requirements. At the same time, Ukraine's agriculture generates millions of
tons of fibrous products: cereal straw, sunflower and corn stems, flax, hemp and others.
In this paper fibre hemp as a raw material for
paper pulp will be compared to poplar.
Pulping of non-wood raw materials
In principle, all fibre-containing
by-products can be used for pulping, but their processing in the pulp and paper industry
is more expensive than the processing of wood. Agricultural by-products are more
bulky and dispersed over larger territories than wood, making their transport and storage
more costly. Other factors increasing the costs of pulping of non-wood raw materials
using existing technologies are:
- heterogenous morphology of the raw material
containing stems, leaves, spikes, seeds etcetera, and the presence of non-fibrous
impurities (e. g. soil),
- high ash content of raw materials and
especially the presence of silicon compounds,
- lower pulp yield as compared to wood pulping.
The negative effect of these factors on
production and environmental safety can be minimized by additional expenses for the
preparation of raw materials, the removal of silicon and the disposal of wastes.
However, the extra costs involved would make non-wood pulp more expensive than wood
pulp.
Poplar or hemp?
The development of a competitive pulp
industry in sparsely wooded countries requires:
1. Setting up plantations of fast-growing
plants with a high yield of fibrous raw materials,
2. The development of a new technology
adapted to the specific characteristics of local raw materials, including agricultural
by-products.
For the conditions of Ukraine, the choice of
plants to be grown on plantations and to be used for pulp and paper is limited to
fast-growing poplars or hemp. The technology for growing poplar in short rotation
(12 years) plantations has been developed by one of the Ukrainian Research Stations.
In the south of Ukraine, Toropogritsky's poplar is recommended for growing.
The annual increment of such poplar plantations on irrigation areas of the Kherson
Region varies from 20 to 40 m3/ha,
depending on fertility, planting pattern and irrigation practice. Taking an average
annual increment of 30 m3/ha, and a
poplar wood density of 420 kg/m3,
we obtain an amount of wood of 12.6 ton per ha per year. A feasibility study for
such poplar plantations has shown that the costs of the wood were four to five times
higher than those of aspen wood logged and delivered to the Kherson Pulp and Paper Mill
from Central European regions of Russia.
Hemp is promising as a raw material for pulp
and paper. Southern hemp is most suitable for growing under the conditions of
Ukraine, since it is hardy, suffers little damage from pests and diseases, and can be
grown in monoculture for many years. At present its yield of dry stems is 8-10
ton/ha in many areas, which is four to five times more than the average annual increment
in Ukranian forests and approaches the increment of the most productive plantations of
fast growing poplars.
Perspectives
The Ukranian Institute of Bast Crops
(UIBC) at Glukhov, Sumy Region, has bred hemp cultivars containing practically no
psychoactive components. Until the present the hemp selection was aimed at breeding
varieties for the textile industry, i.e. the selection work took into account the bast
portion of the stem, as well as the content of THC. In the pulp and paper industry,
the entire stem can be used. Based on its large experience, the UIBC expects it can
breed cultivars yielding 12-14 ton/ha of dry stems. In this case the stem yield is
comparable to the wood yield of the best polar hybrids. As opposed to hardwoods such
as poplar, hemp can meet all the requirements of the paper industry for short- and
long-fibred pulps for practically any paper or board grade.
In 1992, UIBC compared the labour costs of
growing and harvesting hemp to those of poplar. Proceeding from the present average
yield of 6 ton/ha for hemp and from an annual increment of poplar of 12.6 ton/ha, the
costs were comparable. Thus, hemp plantations are more efficient than poplar
plantations as a source of raw materials for the pulp and paper industry. However,
the advantages of hemp can be realized only if a new technology allowing pulping of the
entire stem is developed. Such a technology has been developed at the Ukrainian Pulp
and Paper Research Institute. Its basic concepts are summarized in a research
proposal (page 28) and will be presented more in detail in a
future paper.