Page 177 - Materials Chemistry, Second Edition

162 A. Bjørn et al.

increase the supply of glycerol by 20 tonnes?” Being a supply oriented question,
we go directly to Step 3, where we are asked to identify products for which glycerol
can serve as a substitute, based on relevant functionality, technical quality, costs,
etc. Through analysing the biodiesel market, for example through biodiesel journals
and experts in the field, we find that glycerol from biodiesel can be used by
producers of chemicals, especially for the production of propylene glycol. Hereby
glycerol can, after distillation and processing, substitute other feedstock in the
production of propylene glycol. Having identified a substitute, we go to Step 4, to
identify the propylene glycol production technology affected by the change in
feedstock to glycerol. This procedure (not detailed here) allows us to include the
avoided production of propylene glycol in our LCI. When doing so, it is important
to identify the processes needed to convert the crude glycerol to propylene glycol
and remember to take into consideration the conversion rate.
Having considered both the substitution of diesel with biodiesel and conven-
tional propylene glycol with propylene glycol made from glycerol, we have now
considered all the downstream parts of the life cycle. However, our decision to
supply more poultry fat biodiesel will also create changes in the upstream part of
the life cycle: If we want to supply more poultry fat biodiesel, we need more of the
constituents included for producing the biodiesel. The demand for these con-
stituents thereby increases. In the concrete case, biodiesel is made from poultry fat
and methanol, which are brought to react using a strong base, often sodium
hydroxide. For the sake of simplicity, we will here only consider the increased
demand for poultry fat and methanol.
Thus, we return to Step 1 and ask: “What happens if I increase the demand for
poultry fat?” As this is clearly a question that relates to demand, we go to Step 2.
The first part of the decision tree in Step 2 (Fig. 9.4) asks us to consider whether
the production of the product is constrained. In this case, this is actually the case,
since poultry fat is a low value by-product from the production of other poultry
products, mainly meat. The production of poultry fat therefore follows the demand
for poultry meat, and additional demand for poultry fat will not result in an addi-
tional supply of poultry fat. As the assessed decision will lead to an increase in the
demand for poultry fat, and as market analysis shows us that poultry fat is already
used to the extent the constraint of being a co-product allows (in other words, no
poultry fat is wasted), we go to Step 3, to find out which product can substitute our
use of poultry fat. Poultry fat is mainly used in the feed industry and through
contacts to feed producers we find that they are able to use palm and soybean oil in
a certain relationship instead of poultry fat. This implies that if we decide to
produce more biodiesel from poultry fat and thereby demand more poultry fat, we
will not increase the supply of poultry fat but rather increase the demand for palm
and soybean oil. To identify the consequences of the increased demand for these
oils, we go through the relevant Steps 2–3 for each of these, but to keep this
example relatively simple, we will not go further into documenting these steps.
Assuming that we have now fully outlined the processes that change as a result
of our increase in demand for palm and soybean oil, we turn to the other main
constituent of biodiesel, namely methanol. As noted above, we also increase the