Methodology for assessing carbon footprints of horticultural products

waste processing following disposal of the product. 11 In section 5.1 we defined a number of allocation
principles for final processing. These are worked up in more detail here. The most important principle is that
we compensate for feedbacks to the chain via recycling of materials and energy. We therefore calculate a net
demand for materials and energy from the primary demand by compensating for feedbacks.
Materials recycling
The method used to compensate for feedbacks into the chain is proposed by various materials producers in
different countries (WRAP UK, World Steel Association) and also forms the basis for the calculation of the
carbon footprint of packaging in the Netherlands (Bergsma 2004; Sevenster et al. 2007). The materials
producers in particular emphasise the importance of this approach, because the use of primary and secondary
materials in the production of a product and the recycling of materials after disposal vary widely depending
on the use of the product. For example, minimal amounts of secondary materials are used in the manufacture
of the steel used to make cans, whereas after disposal most of this steel is recovered for use in other products
with other product requirements. The question is whether analyses of the production of packaging steel
should be based on the actual use of materials or the loss of materials associated with the specific use of the
product, which has to be made up by the introduction of new primary materials into the materials cycle. We
illustrate the importance of this using an example calculation. In the first instance, a steel container is
produced mainly from primary raw materials in a blast furnace. A small amount of scrap metal (four percent)
is added for the purpose of conditioning in the furnace, but the steel is produced mainly from iron ore,
limestone and coke. Based on this actual situation, the carbon footprint of packaging steel is about 2.7 kg
CO2eq per kg packaging steel. However, if the calculation is based on the primary production needed to
compensate for the loss of steel from the chain, the carbon footprint turns out to be much lower, at about 1.1
kg CO2eq per kg steel. This difference arises from the big difference between the greenhouse gas emissions
from the primary and secondary production pathways.
Table 5.14 Greenhouse gas emissions from the use of steel, accounting for primary and secondary raw materials inputs and
allocated to material production and product [based on WRAP and Ecoinvent]
Production emissions
(kg CO 2eq/kg)
43
Carbon footprint
(kg CO 2eq/kg)
Actual input of primary raw materials 96% 2.8 2.7
Actual input of scrap metal 4% 0.3 0.0
Total 2.7
Loss of steel from the chain
compensated for by primary production
30% 2.8 0.8
Production from collected scrap metal 70% 0.3 0.2
Total 1.1
PAS 2050 states that when materials recycling is involved the calculation of emissions should be based on the
actual use of primary and secondary materials. It does not use the method of compensating for the use of
primary materials due to materials recycling in the chain. In principle this approach requires relatively few
data because the fate of the material after recycling does not have to be considered. The disadvantage is that
recycling efforts in the chain are not revealed, or only to a very limited extent. 12 Moreover, we question
whether this recommendation in PAS 2050 is consistent with the recommendation to use the compensation
method in cases where electricity is produced by CHP.
11 Except the materials in capital goods and the materials that make a very small contribution to the carbon footprint
12 What is revealed is the avoided waste processing, but the effect of this is negligible for non-combustible materials such
as steel, glass and aluminium.