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Hemp (Cannabis sativa L.) production and uses in Ireland
J. Crowley and B. Rice
Teagasc - Crops Research Centre, Oak Park, Carlow, Ireland
Introduction
Historical records
indicate that hemp was grown in Ireland during the 18th century, but no
commercial enterprise was established. Some hemp was grown during the 1938-45
period for bird seed. The first scientific evaluation of hemp took place from
1960-66, using the varieties Fibrimon 21, 24 and 56. Stem yields of 10 t/ha and
fiber yields of 2.5 t/ha were achieved. The quality of yarns and twines produced
were shown to be slightly inferior to British Standard specifications. It was
concluded that, at the prices then prevailing, hemp could not be regarded as an
economic source of raw material for paper manufacture (Neenan 1969).
As with most European countries, the
search for alternative non-food crops has been underway in Ireland since the
late 1980’s. The high yields and long list of possible industrial uses for
hemp (Herer 1995) prompted a limited re-examination of the crop in Ireland
starting in 1995.
Two objectives were set in this
re-evaluation: (a) to establish the yield potential of the low-THC varieties and
(b) to identify possible domestic end-users. With no paper industry in Ireland,
two optional uses for the whole unprocessed stem were considered: (a) burning to
generate energy and (b) fiber board manufacture. Either option would require a
large production area to achieve economic viability. If this were established,
it could serve as a stepping stone towards constructing a fiber extraction
facility.
Renewable energies in Ireland
Ireland has been a late starter
in promoting renewable energy technologies. There are no environmental or CO2
taxes to stimulate renewable energy development. Since 1995, an Alternative
Electricity Requirement (AER) scheme has been operated by the Electricity Supply
Board (the national procurer) in which enhanced prices were paid for electricity
generated from renewable sources. Three rounds of this scheme have now been
completed. The successful tenders have been mainly for a wind plant, with a
number of land-fill and hydro projects, one 30 megawatt (MW) municipal
waste-to-energy plant and only one small biomass (biogas) project. In the most
recent round of tenders, wind-power has been offered at very competitive prices,
between 2 and 3 pence per kilowatt-hour (kWh). This is likely to depress the
prices offered for electricity from biomass projects in future rounds.
Energy from biomass
Only about 1% (5 petajoules) of
Ireland’s primary energy demand comes from biomass at present. This is mainly
wood-waste used for home heating and industrial drying in the wood processing
industries. Raw material procurement is the predominant cost component in all
biomass-to-energy systems. To produce energy at a cost approaching that of
conventional mineral fuels, stable supplies of low-cost raw materials are
essential. At present, these are most likely to be residues or wastes for which
competing uses are either low-value or non-existent (Rice et al.. 1997).
Opportunities for the use of arable
crops as fuels have been virtually ruled out at present by reductions in
set-aside land and uncertainty surrounding its future. The ‘Agenda 2000’
proposals now taking shape may well offer somewhat better prospects for non-food
production. However, investors will need firm assurance of supply continuity as
well as raw material costs in the new regime, before they can be expected to
commit funds to bio-fuel plants.
Variety | Total dry matter yield |
Percentage leaf dry matter |
stem dry matter yield |
Percentage dry matter left as stubble |
||
(t/ha) | (t/ha) | 1st 10 cm | 2nd 10 cm | |||
|
'Fedora' |
23.2 |
29.7 |
16.3 |
8.1 |
7.3 |
'F19' | 21.6 | 31.4 | 14.8 | 8.1 | 7.3 | |
'F34' | 19.6 | 24.2 | 14.9 | 8.6 | 8.8 | |
'F74' | 20.5 | 19.6 | 16.5 | 7.9 | 7.7 | |
'Fasamo' | 21.2 | 17.7 | 17.4 | 8.3 | 8.3 | |
Mean | 21.2 | 24.5 | 16.0 | 8.2 | 7.9 | |
Standard Error | 1.5 | 5.32 | 1.8 | - | - |
Hemp varieties and agronomy
The results of one trial of five
varieties indicate the yield levels achieved over the last three years (Table
1). The crop established quickly and smothered any developing weeds. Despite the
height of the crop (up to 3 meters), no lodging occurred. Apart from Botrytis
cinerea, no other pests or diseases were recorded. Crops flowered around
mid-August and were cut with a disc mower in early September. Despite the large
volume of green matter, the stems dried to 85% dry matter over a period of 7 to
10 days. The dried stems were wind rowed and baled without difficulty. While total biomass dry
matter yield has been very high at 21.2 t/ha, the percentage of non-stem material was very high at 24.7%.
Also, each increase of 10 cm in stubble height reduced the stem yield by approximately 8% (Table 1).
Since the traditional focus of hemp agronomy has been to produce
maximum yields of high-quality fiber, the effect of seeding rate on yield and stem dimensions was examined
(Table 2). Reducing seed rate from the traditional 50 kg/ha to 20 kg/ha led to a significant increase in stem
yield, due in part to a significant reduction in the number of extremely thin dwarf plants, a decrease in
Botrytis-infected stems and an increase in stem diameter (Table 2).
|
Seeding rate |
Stem dry matter yield |
Stem diameter |
(kg/ha) | (t/ha) | (mm) | |
50 |
16.1 |
7.90 |
|
40 |
16.2 |
9.83 |
|
30 |
16.7 |
10.23 |
|
20 |
18.2 |
10.55 |
|
Standard Error |
+1.05 |
+1.01 |
|
The main disadvantages are:
References