A: feedstock use varies per pulp type.
Virgin pulps have higher feedstock use, but the bio-energy produced
during pulping is also accounted for. A tree ‘saved’ due to
recycling is not accounted for in this approach as there is no limit
to the amount of resources that can be used.
B: feedstock use is preset.
Because of the increasing pressure on biomass, we model a system
with resources constraints (wood). Virgin feedstock use is therefore,
for all three pulp types, preset at the same fixed level (the amount of wood needed when all paper would be produced via
chemical pulping). Surplus feedstock not used for paper production
is assumed to be converted into bio-energy. This method gives
extra CO2 credits to mechanical pulping and recycling of paper, as
surplus biomass is assumed to be converted into bio-energy.