The case study has shown that the proposed models can be used for analyzing the current situation of the maintenance
process with respect to the transportation effort and the resulting cost for transportation and disposal. It is also found that
the city government would benefit from allowing new facilities to be established. The provided results can be used for identifying
the number and locations of those facilities that provide the largest benefit to the municipality. From the perspective
of transportation, establishing new facilities at central locations is most attractive. Nevertheless, we have found that also
sites in the periphery become attractive if they offer disposal capacity at low cost. For this purpose, we have analyzed the
competitive environment of a set of facilities with regard to the offered capacities, various disposal cost rates, and the penalties
that are charged if the municipality does not meet contracted capacity levels. The results reveal that facilities strictly
demanding a certain amount of biomass throughout all months of a year are very unattractive from the perspective of the
municipality, because the city cannot deliver such constant amounts due to the strong seasonality of green waste formation.
Therefore, municipalities should preferably cooperate with facilities that allow flexible capacity bookings, which may be violated
at a certain penalty. In particular, the results show that the height of the penalty rate has only a minor impact on the
solutions, such that the municipality should keep open this option to cope with fluctuating amounts of green waste. Under
such conditions, the least cost transport flows can vary strongly throughout a year and they no longer just depend on the
transportation cost rates. Hence, the decision making should be supported by approaches like the one proposed here.
Furthermore, although not elaborated in this case study, the presented models can also be used for evaluating the impact
of changes of maintenance standards. For example, a municipality may consider transforming the size of a green space or the
type of vegetation. Such modifications can be reflected in the models by changing those parameters that characterize a green
space. With altered parameter constellations, a municipality can rerun the models to evaluate how the modifications change
the amount of green waste and the cost. The municipality can even assess the effect of establishing new green spaces or of
abandoning existing green spaces by adding or removing places to/from the model data.
To summarize, we have shown how to support a municipality in deciding how to organize the disposal logistics, how to
determine and book the required disposal capacities, how to select the most appropriate disposal facilities to cooperate with,
and how to assess future modifications of a city’s green spaces. Thereby, the proposed models guarantee a best possible trade
off of the involved cost while respecting various ecological factors of biomass formation and relevant labor issues.