Process temperature greatly affects the surface area of pyrolysis products. In one study,
surface area was shown to increase from 120 m2g-1 at 400°C to 460 m2g-1 at 900°C (Day et
al., 2005). This effect of temperature has led to suggestions that biochar created at low
temperature may be suitable for controlling the release of fertiliser nutrients (Day et al.,
2005), whilst high temperature biochars would be more suitable for use as activated carbon
(Ogawa et al., 2006). The surfaces of low temperature biochar are, however, hydrophobic
and this may limit the capacity to store water in soil.