Page 236 - Materials Chemistry, Second Edition

ACCOUNTING FOR ECOSYSTEM GOODS AND SERVICES 223

MJ of non-renewable fossil fuel energy
required to make 1kg of 1,3-propanediol

Fossil-based
I Bio-based

Process LCA EIO-LCA Eco-LCA
Figure 9.1 Calculating the fossil energy required for manufacturing 1,3-propanediol from
fossil fuels and biomass varies when using process LCA, EIO-LCA and Eco-LCA (updated
from Urban & Bakshi 2009).

the economic model to predict that the 1,3-propanediol would require less
energy that it actually does.
Certainly though, no matter which method of LCA is used, the same trend
is seen with the fossil-based 1,3-propanediol having a much higher use of the
non-renewable fossil fuels than the bio-based. However, the ecosystem goods
and services traditionally included in LCA, which are energy requirements,
water withdrawals, and emissions, are not the only valuable ecosystem goods
and services that should be considered. This is the difference between Eco-
LCA and the other types of LCA investigated here. Figure 9.2 shows a graph
of different minerals needed to create the same 1kg of 1,3-propanediol. This
information comes from Eco-LCA only, as other methods of LCA do not tradi-
tionally account for minerals.
This comparison of the minerals required illustrates how some resources are
better for one feedstock while other resources will be better for the other feed-
stock. If only the fossil fuel consumption had been found, then the bio-based
feedstock would have been the better option; however, by including the miner-
als it is seen that if the more important resources are many of the nonmetallic
minerals, then the fossil fuel-based feedstock will be the better option.
While there are many studies that look at the carbon footprint of various
products, an area that is just starting to receive attention and concern is the
nitrogen footprint. In fact, it has been found that many products that have
a favorable carbon footprint may have a very unfavorable nitrogen footprint
and vice versa (see Figure 9.3). In order to address both of these current areas
of concern, Eco-LCA contains both carbon and nitrogen cycle information. The
following graph shows the carbon and nitrogen footprints for both the fossil
fuel-based and bio-based feedstocks for 1kg of 1,3-propanediol.