Bioenergy is currently the fastest growing source of renewable
energy. Cultivating energy crops on arable land can decrease dependency
on depleting fossil resources and it can mitigate climate change…
Using industrial hemp for the production of bioenergy has been promoted by enthusiasts for a long time.
ShutterstockBioenergy is currently the fastest growing source of renewable energy. Cultivating energy crops on arable land can decrease dependency on depleting fossil resources and it can mitigate climate change.
But some biofuel crops have bad environmental effects:
they use too much water, displace people and create more emissions than
they save. This has led to a demand for high-yielding energy crops with
low environmental impact. Industrial hemp is said to be just that.
Enthusiasts have been promoting the use of industrial hemp for
producing bioenergy for a long time now. With its potentially high
biomass yield and its suitability to fit into existing crop rotations,
hemp could not only complement but exceed other available energy crops.
Hemp, Cannabis sativa, originates from western Asia and
India and from there spread around the globe. For centuries, fibres were
used to make ropes, sails, cloth and paper, while the seeds were used
for protein-rich food and feed. Interest in hemp declined when other
fibres such as sisal and jute replaced hemp in the 19th century.
Abuse of hemp as a drug led to the prohibition of its cultivation by the United Nations in 1961. When prohibition was revoked in the 1990s in the European Union, Canada and later in Australia, industrially used hemp emerged again.
This time, the car industry’s interest
in light, natural fibre promoted its use. For such industrial use,
modern varieties with insignificant content of psychoactive compounds
are grown. Nonetheless, industrial hemp cultivation is still prohibited
in some industrialised countries like Norway and the USA.
Energy use of industrial hemp is today very limited. There are few
countries in which hemp has been commercialised as an energy crop.
Sweden is one, and has a small commercial production of hemp briquettes. Hemp briquettes are more expensive than wood-based briquettes, but sell reasonably well on regional markets.
Large-scale energy uses of hemp have also been suggested.
Biogas production from hemp could compete with production from maize,
especially in cold climate regions such as Northern Europe and Canada.
Ethanol production is possible from the whole hemp plant, and biodiesel
can be produced from the oil pressed from hemp seeds. Biodiesel
production from hemp seed oil has been shown to overall have a much lower environmental impact than fossil diesel.
Indeed, the environmental benefits
of hemp have been praised highly, since hemp cultivation requires very
limited amounts of pesticide. Few insect pests are known to exist in
hemp crops and fungal diseases are rare.
Since hemp plants shade the ground quickly after sowing, they can
outgrow weeds, a trait interesting especially for organic farmers.
Still, a weed-free seedbed is required. And without nitrogen
fertilisation hemp won´t grow as vigorously as is often suggested.
So, as with any other crop, it takes good agricultural practice to grow hemp right. Hemp
has a broad climate range and has been cultivated successfully from as
far north as Iceland to warmer, more tropical regions. Flickr: Gregory Jordan
Being an annual crop, hemp functions very well in crop rotations.
Here it may function as a break crop, reducing the occurance of pests,
particularly in cereal production. Farmers interested in cultivating
energy crops are often hesitant about tying fields into the production
of perennial energy crops such as willow. Due to the high self-tolerance
of hemp, cultivation over two to three years in the same field does not
lead to significant biomass yield losses.
Small-scale production of hemp briquettes has also proven
economically feasible. However, using whole-crop hemp (or any other
crop) for energy production is not the overall solution.
Before producing energy from the residues it is certainly more
environmentally friendly to use fibres, oils or other compounds of hemp.
Even energy in the fibre products can be used when the products become
waste.
Recycling plant nutrients to the field, such as in biogas residue,
can contribute to lower greenhouse gas emissions from crop production.
Sustainable bioenergy production is not easy, and a diversity of
crops will be needed. Industrial hemp is not the ultimate energy crop.
Still, if cultivated on good soil with decent fertilisation, hemp can
certainly be an environmentally sound crop for bioenergy production and
for other industrial uses as well.
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