System Boundary

It is crucial to make clear cut-offs when defining a system, and its spatial, temporal and material boundary.

Figure 1 visualizes the socio-economic metabolism of Odense in a wider perspective, including its connection and dependency to the regional (and global to some extent) environment for securing resource and consumer goods supply. Embodied emissions first occur with the processes to provide materials, in agricultural processes, the extraction and processing of materials and the supply of water.

The materials then enter the municipality and are incorporated to the anthropogenic stock, i.e. built environment and mobile stock. In Odense´s metabolism, operational emissions are occurring while operating the stock and – to a lower extent – during the end-of-life (EoL) phase (waste management).

But since energy recovery and recycling are implemented in the waste management system of Odense, the EoL phase is also a secondary source for energy and material. Accordingly, those flows are returning to the use phase.

To quantify the embodied emissions caused by the city it is necessary to determine the material inflows of the urban metabolism and the city´s material stocks. Stock can here be thought of as, the accumulated materials within the city, that entered the system as material inflows in the past and are still within the city´s boundaries. The material outflows usually considered in an urban metabolism – solid waste, demolition waste and wastewater - are not quantified in this study (dashed symbols), since emissions from outflows are covered with the operational emissions occurring in the city.

Emissions which occurred during the construction phase, are not included in the estimation (dashed arrows). This is, due to the complexity of the estimation and furthermore it is assumed that it will contribute only marginal. (Stephan & Crawford, 2014) conclude in their study that the construction works contribute insignificantly with 1.3 % to the carbon replacement value.

To determine the embodied emissions in flows, first an economy wide material flow accounting is conducted at the municipality level or flows derived from the stock data through outflow and historic inflow modelling. Then data for emission intensities from existing LCA studies and databases are obtained and multiplied by the magnitude of the observed flows.

2.1.1 City of Odense

The case city Odense is the third biggest city in Denmark after Copenhagen and Aarhus and is located on the island of Funen in between the peninsular Jutland (west) and the island Zealand (east) with Denmark´s capitol. Since the island is surrounded by the Baltic Sea, the climate can be defined as mild.

Odense is a continuously growing city. In 2007 Odense´s population amounted to 186 745 people, ten years later in 2017 the city had 200 563 inhabitants. Over this period of ten years an average growth rate per year of 0.72 % could be documented. The growth of population accelerated the growth of economic activity and the city is willed to invest 34 billion DKK – converted around 5.18 billion US dollars- in urban development in the coming years (Odense Kommune, 2017b). Sustainability and efficiency are important factors considered in the plans of the municipality which is for example reflected by the initiative Smart City Odense, where aspects like better mobility by bike to reduce the CO2 emissions and more efficient energy and water use are considered, but also how to guarantee a clean urban environment (Odense Kommune, 2015).

Table 1 presents the recent general properties of Odense.

Table 1: Properties of Odense (References in Appendix 7.1) GDP: Gross Domestic Product, HDI: Human Development Index.

2016 2017 2018

Population 198 972 200 563 204 080

Population density [cap/km²] 657.4 661.8 667.8

GDP per Capita [USD/cap] 60670 61582

GDP growth rate [%] 1.5

HDI Value 0.928 and Rank 11 0.929 and Rank 11

Ave. Daily Temperature [°C] 8.4

Spatial Boundary

Even though, some of the outer areas of Odense´s municipality are rather rural, the municipal border is chosen to be the spatial boundary (Figure 2(Odense Kommune, 2018)). This is since statistical data is collected and documented for the whole municipality.

2.1.2 Stock Categories

Table 2 shows the material stock categories considered in this study. Railways are not considered in the transportation infrastructure. Data on pipe networks for drinking water, wastewater or heating was not available and as well no on cable networks.

Table 2: Material Stock Types

Category Type

Buildings - Residential

- Non-Residential

Transportation infrastructure - Roads

Mobile Stock - Vehicles

- Electronic Appliances

2.1.3 Urban Metabolism Inflows Following inflows of the UM are considered:

- Energy

- Construction Material - Food

- Water

- Consumption of Goods

o Including packaging, vehicles and electronic appliances 2.1.4 Temporal Boundary

Inflows into the municipality were gathered for the years 2010 to 2018. Unfortunately, data on energy consumption in the municipality could only be obtained for the years 2010 to 2015 as well as for packaging. Because of that, for the comparison of embodied and operational emissions the base year 2015 was selected.

The embodied emissions in the built environment respectively the CRV was estimated for the year 2018.

2.1.5 Emission Factors for Carbon Replacement Value and Embodied Emissions

The CRV reveals the amount of CO2 emissions resulting from erecting the whole built environment of Odense from scratch, under today’s status quo conditions and to provide the same level of services

through inflows. In order to calculate Odense’s CRV, data on emission factors for material or product are used.

In case of missing data, the embodied emissions were calculated with the current Danish energy mix applied on the electricity needed for providing the material.

(Energinet, 2018) states that, in 2017, the provision of one kWh caused 0,190 kg of CO2. The Danish Energy Agency (DEA) states a value of 0,290 kgCO2/kWh (Danish Energy Agency, n.d.). The difference between these two numbers can be explained by the difference in scope in the calculation of these values: while the DEA’s value represents the average emission of a produced kWh in Denmark (Danish Energy Agency, n.d.), Energinet also includes export and import of electricity. For these reasons, Energinet’s value was deemed the most relevant in depicting representative Danish conditions.