Náttúrufræðingurinn - 1987, Page 61

SUMMARY
Binding of solar energy
in agriculture and its
utilization
by
Hólmgeir Björnsson
Rannsóknastofnun Landbúnaðarins
Agricultural Research Institute
Keldnaholti
112 Reykjavík
The potential of crops for binding solar
energy is discussed with regard to Icelandic
growth conditions and the possibilities of us-
ing plant material as fuel instead of fossil solar
energy.
In Iceland large amounts of energy per cap-
ita are consumed and in 1977, 54% of the en-
ergy came from fossil fuel. During the sum-
mer, growth rate of the most productive
plants (Table 3, Fig. 1) is similar to what is
commonly found for C3-plants in other agr-
icultural areas, but the growing season is
shorter.
The main crop in Iceland is hay. A rough
estimate is that the animal products that are
marketed account for only about 5% of the
solar energy fixed by grass. More than one
third of the energy is commonly left in the
manure (Table 4). Part of this energy can be
utilized, either directly as heat, or the manure
can be fermented to produce gas rich in
methane.
In recent years considerable research has
been devoted to the cultivation and utiliza-
tion of plants as an energy source in the Nor-
dic countries, with the exception of Iceland.
Wood is being used more as fuel than when
fuel prices were lowest. Straw is collected
locally and burnt in heating centers. Hay,
harvested late in the summer when yield is at
maximum but nutritional value has become
low due to lignification, can also be used as
fuel. With the present fuel prices this would
not pay.
Plant oils (as well as fish oil) can replace
diesel oil and other heavier fuels. Plant
products rich in sugar or starch can be used to
produce alcohol for use as fuel. It is forsee-
able that lignified plant material can be used
for the production of light fuels as well.
Finally, hydrogen can be used as an energy
source to replace fossil fuels. Its production
requires other energy sources such as hydro-
electric power, which is plentiful in Iceland,
and a carbon source. In Iceland peat,
however, has the disadvantage of being rich
in ash, rarely less than 18%, due to airborne
volcanic products.
In Iceland there are extensive areas that
could be turned into productive cultivated
land. With increasing fuel prices and new
technological developments there is a pot-
ential in Iceland for replacing the use of fossil
solar energy with currently bound solar
energy.
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