*2.3. Alternative Pathways*

Four pathways have been devised for buildings and transport infrastructure, describing di fferent future trajectories of technological developments in the supply chains of buildings and transportation infrastructure in Sweden, two with a focus on bio-based measures together with CCS and two with a focus on electrification:


The second of the two within each focus explores the role material e fficiency measures may play in the low-carbon transition. Details of the emissions reduction measures applied over the timeline for the di fferent pathway scenarios are displayed in Table 2.

For cement, the bio/CSS pathway adopts post-combustion carbon capture with amine scrubbing, which is the technology tested by HeidelbergCement in Breivik in Norway [135]. In all pathways, a progressive realization of cement clinker substitution and cement demand reduction from optimization of concrete recipes is assumed.

For primary steel production, the bio/CCS pathways adopt process modification enabling top gas recycling combined with carbon capture and storage, while the electrification pathways pursue a hydrogen direct reduction (H-DR/EAF) steelmaking process. Current electric arc furnaces for scrap-based secondary steel production are being refurbished and upgraded at a continuous rate in all pathways, alongside partial bioenergy substitution in the bio/CCS pathways.

Separate pathways have also been devised for construction equipment and heavy transports, while other materials follow a common decarbonization pathway (based on, e.g., Reference [37,41,74,83,108,130,136]).

The pathway portfolios are predominantly based around reaching the medium-high range of the emission reduction potentials for each selected abatement measure when fully implemented (as per Figure 5) with measures and timelines largely compatible with roadmaps and pathways developed within the EU Commission long term climate strategy (combination of electrification and hydrogen scenarios), along with relevant industry roadmaps developed within the Fossil Free Sweden project [48,137].


**Table 2.** Details of abatement measures applied across pathways with percentage figures depicting the di ffusion of the specific mitigation option.


**Table 2.** *Cont.*

Sensitivity Analysis

The main assumption in the model is a constant construction demand up until 2045. However, this assumption is uncertain and different sources provide diverse interpretations of how the demand for building and transport infrastructure construction will develop. For example, the Swedish Energy Agency, in its long-term prognosis, predicts the energy use of the building construction sector to increase until 2020 due to extensive construction of new housing and to then fall back to previous lower levels after 2025 [138]. This would imply reductions of around 20% to 2030 and 30% to 2045 based on 2020 levels.

On the other hand, Boverket estimates that, by 2025, Sweden needs 600,000 new dwellings, implying a level of construction not anticipated in the prognosis of the Swedish Energy Agency [7,139]. Further, a grea<sup>t</sup> need for renewed transport infrastructure has been identified to enable the climate transition of the transport network to be realized while meeting increased transport demands, including the anticipated but heavily discussed construction of a highspeed railway network [140,141].

Consequently, a scenario analysis has been performed to test the implications of reductions/increases in construction demand of ±20% to 2030 and ± 30% to 2045.
