Legal, economical and technical preconditions for the feed-in of biogas into the Austrian natural gas grid
This project deals with the legal, economical and technical preconditions for a successful introduction and market development of fermentation gas feed-in to the Austrian natural gas grid.
Austria has a technically usable fermentation gas potential of approximately 1 billion cubic meter (24 Petajoule) per year, this corresponds to 6,7 % of the annual natural gas consumption of about 9 billions cubic meters. In case of using the whole Austrian fermentation gas potential the CO2-emissions could be reduced by 1,18 mio. tons per year. Those reduction is nevertheless 1,6 % of the annual Austrian CO2-emissionens.
However, the investigations done within this study showed, that present quality requirements for gas feed-in are due to historical reasons oriented at the quality of natural gas. The specialities of fermentation gas, in particular the lower energy content of fermentation gas, are not taken into account. As a result, fermentation gas has to be upgraded on the quality of natural gas before it can be fed-in into the gas grid. The required upgrading process is very cost expensive.
The range for the specific total costs of the fermentation gas feed-in amounts for a plant of medium size (300 m3/h) to about 3.1 to 5.7 €cent/kWh. The upper cost level corresponds to a fermentation gas facility, which uses energy crops as substrate and feeds into the low pressure gas grid (grid level 3). The lower cost level results in the case of sewer gas.
To avoid expensive methane enrichment (2,5 €cent/kWh), also cleaned (but not methane enriched) fermentation gas can be fed in to the grid as so-called "admixture gas". The energy content per cubic meter of the resulting gas mixture depends on the on the mixing ratio of fermentation gas, the so-called "admixture gas" and natural gas. However, the value of (lower) calorific value of the gas at the consumer has to be kept relatively constant. Therefore, a reduction of the minimum permissible calorific value down to about 10 kWh/m3 within a new quality directive for mixture gas is strongly recommended.
A further substantial obstacle for an attractive fermentation gas marketing is the present "duty" for the usage of the gas grid. This so-called "gas system usage tariff" (the Austrian "Gassystemnutzungstarif") is a fix tariff an calculated in a very disadvantages way for fermentation gas feed-in. Even if the gas grid for fermentation gas transport is used for only short distances, e.g., a few hundred meters, the full "duty height" has to be charged. This calculation method must be replaced a calculation method strongly based on a the real, distance depending usage of the gas grid for transport. A fair cost, distance-depending tariff system is thus a further substantial condition for an economically attractive fermentation gas feed-in.
DI Dr. Dieter Hornbachner
HEI | Hornbachner Energie Innovation
Währinger Str. 26/1/3, A-1090 Wien
Tel.: +43 (0)1/3190354 - 20
Fax: +43 (0)1/3190354 - 22
Institute: HEI | Hornbachner Energie Innovation
DI Dieter Moor (Werkvertragspartner)