Agriculture Reference
In-Depth Information
industrial cellulose factories', then there is no intrinsic need for straight plantation grown
trees - though it no doubt remains more efficient to grow and harvest them as such. 6 While
there will always be a demand for sawlogs, there is now much more scope than there was
50 years ago for using timber from biodiverse semi-natural woodlands, at both ends of the
technological spectrum.
The other main product is forestry biomass, otherwise known as firewood, which comes
in a variety of shapes and forms that can be seen ranged down the dark side of Fig 4 . Short
rotation coppice (SRC), at the tame or intensive end of the spectrum, is most frequently of
willow, and under good conditions can attain yields of ten tonnes, or even 15, of oven dry
wood per hectare per year on suitable land. 7 Currently, in the UK it is mainly being tested
on an industrial basis, designed to benefit from economies of scale (though there is a tend-
ency for small scale permaculture settlers to plant a patch on their plot). Planting has so
far taken place mainly on flat, relatively high quality farmland, congenial to machinery and
close to a processing plant (although these have sometimes had problems securing plan-
ning permission). The corporate bias of research and development in the UK tends to steer
bio-energy production towards large-scale centralized schemes based mainly on biodiesel,
bioethanol and willow coppice, even though on-farm processing of biomass for local con-
sumption ought to be more efficient, because of the reduced distribution costs. 8
Traditional coppice and mature woodland are lower yielding, but they have other ad-
vantages. They can be planted and managed on poor land deficient in nutrients, on steep
slopes, and in areas too small for the machinery associated with industrial SRC to be used
efficiently. A proportion of the energy of a fully grown tree is invested in its permanent in-
frastructure - its trunk, roots and branches - which provides both timber and a carbon sink.
Full grown trees may not produce so much renewable energy as SRC, but they store more
carbon, allowing us to emit a bit of greenhouse gas with impunity.
Mature woodland also ranges in wildness between monocrop plantations and mixed spe-
cies woodland. Besides firewood, a well managed mixed woodland supplies timber, a wide
range of coppice wood, game, mushrooms, pig grazing, foliage etc - all of which will be
hard to find in an SRC willow plantation. And finally, in terms of the 'amenity' provided,
biodiverse woodland wins hands down over SRC. According to DEFRA more than 300
million day visits to woodland suggest that 'woodlands are the most popular land-based
destination for day visits'. 9 Few people would choose to take a walk through a field of fully
grown short-term rotation willow coppice; even a wheat field, which you can at least look
over, and which changes in hue and texture over the seasons, is preferable to an impenet-
rable eight foot tall curtain of monocultural biomass.
There is a place for SRC, though overemphasis could easily turn swathes of the coun-
tryside into a biomass factory. One likely place is on the 876 hectares allocated for bioen-
ergy in the Livestock Permaculture scenario in Chapter 9, where either SRC or Miscanthus
 
 
 
 
Search WWH ::




Custom Search