Luca Herbert
Master Thesis - Environmental Engineering - 2019
Cities occupy just three per cent of the Earth’s land, but account for 60-80 % of energy consumption and 75 % of carbon emissions. Accordingly, there is the need to investigate a city’s energy demand and sources of emissions to reveal climate mitigation options. Several studies did account emissions of cities or nations, though those mostly concentrated on estimating the operational emissions, which are occurring during operation respectively the use of stock. To give a holistic overview of the emissions caused by a city, embodied emissions have to be considered, too. They occur in material processing and production and are then embodied in the material and imported into the city. The greatest part of embodied emissions is incorporated in the built environment – the interface of a city.
In this thesis project the total greenhouse gas (GHG) emissions – embodied and operational - caused by the City of Odense were estimated. Furthermore, the carbon replacement value (CRV) of the built environment in Odense, meaning the emissions it would cause to erect the built environment stock using current technologies, was quantified. Here, CO2-emission factors from the literature were applied on the material stock data of the city, which was quantified in a bottom-up fashion. Additionally, the CRV of mobile stocks was considered.
In 2015 the municipality emitted 1 167 kt CO2 in total. Thereof 840 kt CO2 (73 %) were operational emissions and the residual 327 kt CO2 based on consumption and embodied in inflows. The consumption of food contributes highest to the total of embodied emissions with 64 %.
Furthermore, the CRV of the material stock of Odense amounted to 6 039 kt CO2 in 2018 which is equal to 24.8 tCO2 per capita.
Most of the carbon is embodied in residential buildings and non-residential buildings, since the majority of the materials are erected in the built environment. Nevertheless, mobile stocks contribute with a total of 16 % to the total CRV. This finding is very interesting because mobile stocks account for 0.4 % of the total material weight of all stock only. This emphasizes the high energy requirements to provide goods like vehicles and electronic appliances.
The essential take-aways from that thesis project are, that the CRV is an important parameter, since it can be used to estimate future GHG emissions which will occur with rising population and economic development. It is therefore important for policy making.
Moreover, GHG inventories should, for a more holistic study, include embodied emissions as well.