Abstract
Purpose The goal of this study is to analyze the environmen-
tal improvement brought about by an alternative system for
waste management proposed by the Integral-b project, funded
by the European Union (EU). Its aim is to treat both used
cooking oil (UCO) and organic waste from the restaurant and
catering sector in Spain, by biodiesel production and anaero-
bic digestion, respectively. A cogeneration engine adapted to
use glycerin as a fuel is implemented.
Methods The functional unit (FU) is the management of the
UCO and organic waste from restaurants and catering produced
per person and year in Spain. The system proposed (scenario A)
is compared to a system consisting of the prevailing management
options for the same kind of waste (scenario B). Apart from
including biodiesel production from the UCO, this referencescenario assumes that the organic waste is allocated to different
streams, according to Spanish statistics. The systems under study
generate different coproducts and as such are complex; therefore,
system expansion is performed. Different scenario formulations
are set to analyze the influence of assumptions regarding co-
product credits in the results. Finally, Monte Carlo simulations
are carried out to analyze parameter uncertainty.
Results and discussion The environmental benefits caused by
scenario A are conditional on the choices regarding coproduct
credits. Scenario A causes a reduction of the impact (43655 %)
in most of the scenario formulations when the current levels of
UCO collection are considered. However, when higher levels of
UCO collection are taken into account for the definition of the
FU, scenario B performs better for half of the scenario formula-
tions, due to the increase in the environmental credits from
glycerin production. The only impact categories for which sce-
nario A performs unconditionally better than scenario B are global
warming and photochemical ozone creation. Parameter uncertain-
ty appears to influence the comparative results to a lesser extent,
mainly caused by the parameters involved in avoided processes.
Conclusions Although system expansion appears as an option
for dealing with the multifunctionality of waste management
processes, uncertainty caused by choices must be assessed.
Under our scenario assumptions, re-using the glycerol in the
system proposed by Integral-b can be detrimental, and the
reference scenario results in higher avoided burdens in some
scenario formulations. Including glycerin valorization in sce-
nario B should be considered if the biodiesel production keeps
increasing in Spain. Analyzing parameter uncertainty helps to
provide reliable results.
