Renewable Methane Leakage in Germany: Impact on Global Warming

Usage of 300 TWh/year of Renewable Methane to buffer Germany's fluctuating renewable electricity

by Joachim Gruber


Renewable energies, even when combined, need a buffer of about 15 %. When methane is used to buffer German renewable electricity production, methane leaking into the atmosphere will build up a stationary methane pool within approximately 25 years. Then the pool will contribute a constant total of 0.14 GtCO2e to the German Greenhouse Gas (GHG) footprint, i.e. 1.75 tCO2e per person. For comparison: the present annual GHG emissions per German individual are about 10 tCO2e per year and person.


Fig. 1: Compartment system (center, with mathematical representation on the right) modeling the German Greenhouse Gas (GHG) footprint (insert on the left) of a 300 TWh/a renewable methane industry buffering the fluctuations of German renewable electricity generation.

The size of the industry (300 TWH/a) is taken from e.g. scenarios 2.1 and 2.2, Sachverständigenrat für Umweltfragen (SRU), Wege zur 100 % erneuerbaren Stromversorgung, Sondergutachten, Januar 2011 (for more see Appendix). The Sabatier process takes the carbon it needs from the atmosphere. Methane leaking into the atmosphere while it is processed (a), transmitted and stored (b) and distributed (c) decays into CO2 with a half life T = 12 years. This CO2 is then reused by the Sabatier process. Thus the carbon system is closed, meaning that carbon neither leaves the system nor enters into it. Leakage data a, b, c are taken from the Argonne Natl. Laboratory's GREET1_2019 model (see Tab. 4, below).

Shaded Insert

GHG footprints compared

I. Data for 300 TWh/year compartment model (above Figure)

leakage pathway

GREET1_2019 Tab. 4 leakage constant (gCH4/(106 Btu))

leakage constant

for 300 TWh/year system




a = 9.83

transmission and storage


b = 60.0



c = 29.0

conversions used:

II. Sources


The climate implications of using LNG as a marine fuel


Nikita Pavlenko, Bryan Comer, PhD, Yuanrong Zhou, Nigel Clark, PhD, Dan Rutherford, PhD

Table 5: Methane leakage assumptions per unit consumption of natural gas (1 GJ = 778 kWh)

[note added by J.G.

natural gas contains from 50 to 90 % methane (depending on the source)

1 GJ natural gas = 18.6 kg natural gas ( = approx. 18 kg CH4


For this analysis, we used the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model (Argonne National Laboratory, 2018) to estimate upstream emissions for LNG and conventional marine fuels. GREET provides a robust dataset of emissions related to fuel production and breaks them into various life-cycle phases; there is also the option to supplement with user data to assess the impact of various assumptions on a fuel's full well-to-wake (WtWa) GHG emissions. GREET is used widely by government agencies, industries, and academia because it is transparent, flexible, and contains high-quality data.

II. 2 GREET Argonne National Laboratory (ANL)

page 5, Table 4: Summary of Differences .... in A. Burnham, Updated Natural Gas Pathways in the GREET1_2019 Model, October 2019



Projected Methane Production in Germany

Projected CH4 production and consumption in Germany is

Version: 23.3.2020

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Joachim Gruber