Comparison with the conventional system and contribution

from the reference scenario, all scenario formulations for the scenarios replacing grid mix (A) and coal electricity (C) perform better in all impact categories but POF and AP. The scenarios replacing wind electricity (B) perform worse in most categories. In general, the greatest savings are observed for the impact categories of EP and HT, which show values that are between 14-27 times lower in scenarios options A and 56-94 times lower in scenario options C. Savings in the CC category are still notable, associated with impact values around 2.1 (A) and 4 (C) times lower relative to the reference scenario. Generally, the worst-case scenarios as for co-product credits in the PtF system generate the greatest savings relative to conventional methanol production, and the other way round. The best-case scenarios, i.e. scenario options B, only show improvements compared to conventional methanol production in terms of CC and FD. This is due to the fact that neither electricity nor heat nor fertiliser credits are high enough to offset the impacts by the system. Impacts are between 0.01-19 times higher than the reference scenario.

The contribution of each sub-process to the overall impacts from the proposed PtF scenarios is shown in Figure 5.6 (for all values see Table A 10 in appendix A)for those categories that deliver greater savings as compared to the reference scenario, namely EP (freshwater as an example) and HT; CC and FD are also included, since these are the two impact categories to be potentially improved by a renewable fuel production system. AP is shown, as an example where the highest credits of the fertiliser replacement can be achieved and POF because of its significant contributions caused by the CHP. The remaining categories are included in Figure A 4 in appendix A. It holds for all scenarios that the share of electricity credits from the CHP is greater when the electricity from the average mix (A) and electricity from coal (C) are considered. In scenario options B, environmental credits of the heat from CHP and from digestate become more important in most categories. In terms of HT, EP and AP, the effect of the heat credit is negligible for all scenario options, being even smaller than credits from replaced fertiliser production.

Electricity credits play an important role in all impact categories. Fertiliser credits, on the other hand, are small in most categories and negligible as compared to electricity credits. As most grid electricity is required for methanol production, followed by electricity for the biogas plant and CO2 recovery, impacts are the highest for methanol production followed by the two others in all categories.

In terms of credits, electricity credits associated with CHP production account for 28-39% of the overall impacts in the CC in scenario options A and for shares of 53-54% in options C and thus make a significant contribution. The share of electricity credits is however much lower in B, i.e. 1.4%. CO2-eq. credits from heat production account for 30-32% of the impact and are therefore the most important co-product credits in these scenario options. They also play a big part in FD with 44-48%. A relevant impact in CC is made by the combustion of biogas in the CHP (around 14% in A, 22-23% in B and 11% in C) caused by the CH4 emissions to air.

The impacts from biogas production are comparatively low but become more important in scenario options B, where credits are in general lower. In freshwater and marine EP, impacts are very small and outweighed by the electricity credits for scenario options A and C. The same applies for HT. Usually, electricity for H2

production makes relatively small contributions comparable to those of the electricity production taking electricity from the grid mix. However, impacts to HT by wind electricity for H2 generation become more relevant with contributions of 15-16% in scenario options A and in B even higher with 31-40%. This is due to the release of mostly zinc and some other metals to freshwater. In EP, the contribution by the wind electricity is also slightly higher with >10%, though barely mentionable (<5%) in A and C. EP and HT emissions that are caused by grid electricity

production also become more important in B. Electricity for methanol production contributes 10-13% of emissions in scenario options A and around 5% in C. In B, the production is relevant for 39-50% of kg P-eq. emissions, 20-26% of kg 1,4-DB eq. emissions to HT and 37-43% of kg N-eq. emissions. The kg NOx-eq. and kg SO2-eq. emissions generated by the CHP unit, i.e. through the combustion of biomethane, account for between 73% to 86% of POF and 30% and 55% of AP across scenarios. Biogas production also contributes to AP through NH3 emissions to air, although its contribution is with <10% relatively small in all scenarios. The waste water treatment and activated carbon production do not make relevant contributions to any of the categories.

Figure 5.6: Contribution analysis of the processes included in the expanded system for the impact categories climate change (CC), fossil depletion (FD), freshwater eutrophication (EP), photochemical ozone formation (POF) acidification (AP) and human toxicity (HT).

Caption: CHP = Combined heat and power plant.

-5.00 -4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00^A1

CC [kg CO₂eq.]

Credits from single superphosphate production, EU Credits from potassium chloride production, EU Credits from urea production, EU Treatment of wastewater

Heat for biogas plant Electricity for methanol production Electricity for H2 production Electricity for CO2 recovery Electricity for biogas plant Credits from CHP heat production Combustion of biogas in the CHP plant Biogas production

Activated carbon production Credits from CHP electricity production

-5 -4 -3 -2 -1 0 1 2

3 ^{A1 A2 A3 B1 B2 B3 C1 C2 C3}

Climate change (CC) [kg CO2eq.]

-1.75 -1.50 -1.25 -1.00 -0.75 -0.50 -0.25 0.00 0.25

0.50 ^{A1 A2 A3 B1 B2 B3 C1 C2 C3}

Fossil depletion (FD) [kg oil eq.]

-0.010 -0.008 -0.006 -0.004 -0.002 0.000

0.002 ^{A1 A2 A3 B1 B2 B3 C1 C2 C3}

Freshwater eutrophication potential (Freshwater EP)[kg P eq.]

-8.0E-03 -4.0E-03 0.0E+00 4.0E-03 8.0E-03 1.2E-02 1.6E-02 2.0E-02 2.4E-02 2.8E-02

A1 A2 A3 B1 B2 B3 C1 C2 C3

Photochemical ozone formation (POF) [kg NOx eq.]

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 1 2 3

A1 A2 A3 B1 B2 B3 C1 C2 C3

Human toxicity (HT) [kg 1,4-DB eq.]

-1.2E-02 -8.0E-03 -4.0E-03 0.0E+00 4.0E-03 8.0E-03

1.2E-02 ^{A1 A2 A3 B1 B2 B3 C1 C2 C3}

Acidification potential (AP) [kg SO2 eq.]

In the reference system for fossil-based methanol production, electricity production accounts for the largest share of the impacts of EP and HT. While heat production makes the greatest contribution to CC and ODP, NG production accounts for the largest shares of FD, POF, and AP (see Figure 5.7). The NG production is assumed to be from Russia, as most NG is imported from there, and thus also encompasses losses from transport. Although the BMWI (2020) predicts Germany to be highly dependent on NG imports in the future, one may suggest that NG could also be produced from German NG. Therefore, NG coming from German fields is shortly considered in a complementary LCA simulation to present another potential NG source. However, the results only show small improvements. The CC category notes the highest improvements due to the avoided CH4 losses, while other categories also perform slightly better. There appears to be a trade-off, as the German production achieves 34% less emissions of kg CO2-eq., but causes 34%

more emissions of kg SO2-eq. and 16% more of kg NOx-eq. Hence, it cannot be concluded that it is less polluting to take German NG for methanol production. The results for this case are shown in Table A 11 in appendix A.

Figure 5.7: Contribution analysis of the reference scenario for the impact categories climate change (CC), fossil depletion (FD), freshwater and marine eutrophication (EP), acidification (AP) and human toxicity (HT).

0 10 20 30 40 50 60 70 80 90 100

% Reference scenario

Methane leakage Electricity for methanol production Heat for methanol production Natural gas production