**Appendix A**


**Table A1.** Technology readiness level of alternative fuel production.


#### **Table A1.** *Cont.*


**Table A2.** Overview of literature studies investigating fuel production costs.

**Figure A1.** Cost intervals of H<sup>2</sup> and LH<sup>2</sup> production in Germany and abroad, transport costs, and taxes/levies. \* production, \*\* +transport, \*\*\* +taxes/levies. Source: Own elaboration based on (a) [92], (b) [89], (c) [85], (d) [4], (e) [87], (f) [6], (g) [90], (h) [108], (i) [106], (j) [105], (k) [88], (l) [34].

**Figure A2.** Cost intervals of SNG production in Germany and abroad, transport costs, and taxes/levies. \* production, \*\* +transport, \*\*\* +taxes/levies. Source: Own elaboration based on (a) [92], (b) [89], (c) [85], (e) [87], (h) [108], (m) [112], (n) [113], (g) [109].

**Figure A3.** Cost intervals of unspecified PtL fuel production in Germany and abroad, transport costs, and taxes/levies. \* production, \*\* +transport, \*\*\* +taxes/levies. Source: Own elaboration based on [6,85,89,92,108,112].

#### **Appendix B**

#### *Environmental Impacts of CNG/LNG*

Compared to the extensive use of petroleum-based fuels in the German transport sector today, CNG and LNG can help reduce environmental impacts. If the combustion of these gaseous fuels is taken into account, climate change impacts may be reduced due to their chemical compositions. For this reason, CNG and LNG are often referred to as bridging technologies. Thus, from an environmental perspective, vehicles that utilize natural gas-based fuels can bridge the gap between low- and zero-GHG fuels.

Due to the different states of aggregation, CNG and LNG offer different transport options. For CNG transport to the EU and Germany, transport by pipeline can be assumed. For example, an LCA publication by Heidt et al. [240] regarding the environmental effects of CNG for road transport in Germany considered a transport distance of more than 4000 km on average to the EU for the year 2013 and assumed a transport distance of 7000 km for the year 2030. Heidt et al. [240] determined the value of 17.3 g CO2eq/MJ as the WtT emission factor for CNG in the case of 4000 km as the transport distance. For a transport distance of 7000 km, 20.9 g CO2eq/MJ was calculated [240].

An established and well-known series of WtT studies of fuels with Europe as the geographical scope is the JEC WtT reports. In the most recent version, six CNG pathways were analyzed that differed in their assumptions along the pathways (transport distances, production, conditioning assumptions, etc.) [192]. The WtT GHG emissions for CNG vary between 11 and around 17 g CO2eq depending on the respective pathway. Production and conditioning is considered to be the first step in the pathways. A fixed WtT GHG emission of 4 g CO2eq/MJ for production and conditioning was assumed for all pathways. With respect to the transportation to market, as a next step of the pathways, major differences can be noted. Pathways that consider a typical natural gas EU mix with transport distances of only 1900 km to the EU border and average distances of 500 km within it demonstrate the contributions of the transport step being below WtT GHG emissions of 4 g CO2eq/MJ. In a pathway with greater transport distances (4300 km to the EU border and 700 km within it), WtT GHG emissions of just under 10 g CO2eq/MJ were calculated. Another essential contribution to environmental impacts was given by the step of conditioning and distribution, which also includes the compression of gas at service stations. For these steps, values of around 4 g CO2eq/MJ were identified [192].

The LNG supply is also multi-stage. Gas production is followed by a processing step. This is usually then followed by gas transport (e.g., by pipeline) before gas liquefaction occurs. The LNG produced in this process is usually then transported over longer distances (especially by ship). At the end of the chain, depending on the application option, regasification may be conducted. In the most recent version of the JEC WtT report, one LNG pathway is compared to the CNG ones [192]. Around 18 g CO2eq/MJ was calculated for this pathway. Compared to the CNG pathways, this one accompanies an additional noteworthy contribution. The contribution of around 4 g CO2eq/MJ is given by liquefaction. For LNG, an LCA study by Wachsmuth et al. [241] offers more versatile insights in the environmental performance of LNG pathways for Germany. This study considered the environmental impacts for five different cases. A broad range of climate change impacts was featured, spanning from nearly 15 g CO2eq/MJ up to around 29 g CO2eq/MJ. This large range is especially due to deliveries to Germany from regions of the world whose distances vary. The supply of conventional LNG from Katar under the considered conditions carries the lowest impacts. In contrast, the supply of unconventional LNG from Australia (Queensland) exhibited the highest. In the case of unconventional LNG sources, gas production was revealed to be the main contributor to upstream GHG emissions. Furthermore, transport distances revealed a major influence on environmental impacts.
