Economic and technical aspects of biogases and their injection, growth potential for biomass/biogas in Germany Uwe Klaas DVGW e.V., Bonn, Germany.

Economic and technical aspects of biogases and their injection,

growth potential for biomass/biogas in Germany

Uwe Klaas

DVGW e.V., Bonn, Germany

www.dvgw.de

European directive 2003/55/EC

Adopted on 26 June 2003 by the European parliament; Scope:

– natural gas

– liquefied natural gas

– biogas

– gas from biomass

– all other types of gases that can meet necessary quality requirements for access to the natural gas system.

Member States should ensure that, taking into account the necessary quality requirements, biogas and gas from biomass or other types of gas, are granted non-discriminatory access to the gas system, provided such access is permanently compatible with the relevant technical rules and safety standards.

www.dvgw.de

Gases within scope of the MARCOGAZ recommendation “Injection of Gases from Non-Conventional Sources into Gas Networks”

Gases from thermal or fermentation processes:– Biogas from agriculture;

– Sewage gas;

– Landfill gas;

Coal-bed methane and coal mine methane; Hydrogen-rich gases from gasification of e.g., biomass, or other

chemical processes– Gases (“Biosyngas”) from gasification processes based on biomass as

“energy plants”;

– But also the “classical” gasification of coal is a limit case: is that process still “conventional”?

Hydrogen produced from electrolysis (generally using renewable energy as e.g. hydro power, solar power or windmills).

www.dvgw.de

Indicative composition of different raw gases

Composition Units

Natural gas

(typical North Sea

H)

Biogas Coal-associatedgas

Biomassgasification

Anaerobic digester Landfill CMM CBM O2-fired Air-fired

Methane

mol%

88.8 (86.6 - 88.8)

65.0(50 - 80)

45.0(30 - 60) 65.0 90.0 15.6

(0 -18) 2.0

(1 – 10)

C2+ Hydrocarbons

8.3(8.3 – 8.5) - - 1.5 2.2 5.8

(0 - 5.8) (0 – 2)

Hydrogen - (0 - 2) 1.5(0 - 2) - - 22.0

(4 - 46)20.0

(10 – 25)

Carbon monoxide - - - - - 44.4

(13 - 70)20.0

(9 – 25)

Carbon dioxide

2.3(1.9 - 2.3)

35.0(15 - 50)

40.0(15 - 40) 16.0 3.3 12.2

(2 - 35)7.0

(7 – 16)

Nitrogen 1.1(0.9 - 1.1)

0.2(0 - 5)

15.0(0 - 50) 18.0 4.5 0

(0 - 7)approx.

50.0

Oxygen < 0.01 (0 - 1) 1.0(0 - 10) 0.5 - - -

Hydrogen sulfide

mg/m3

1.5(0 - 5)

< 600(100 - 10000)

< 100(0 - 1000) (0 - 5) (0 - 5)

Ammonia - 100(0 - 100)

5(0 - 5) - - - -

Total chlorine - (0 - 100) (0 - 800)

Total fluorine mg/m3 - 0.5(0 - 100)

10(0 - 800) - - - -

Siloxanes mg/m³ - 0 - 50 0 - 50 - - - -

Tar g/m³ - - - - - 0 - 5 0,01 - 100Source: MARCOGAZ recommendation

www.dvgw.de

Indicative properties of different raw gases

Properties Units

Natural gas

(typical North Sea

H)

BiogasCoal-associated

gasBiomass

gasification

Anaerobic digester

Landfill CMM CBMO2-

firedAir-fired

Gross calorific value (1)

MJ/m3 40 32 17 25 36 14 6

kWh/m³ 12 7 7 7 10 4 3

Net calorific value(1)

MJ/m3 35 22 21 23 32 13 9

kWh/m3 10 6 6 7 9 4 3

Wobbe Number (1)

MJ/m3 50 26 27 29 45 29 20

kWh/m3 15 8 8 8 13 8 6

Relative Density (1)

0.6 0.9 0.7 0.8 0.6 0.2 0.3

Density (1) kg/m3 0.7 0.8 0.8 0.8 0.7 0.3 0.3

MethaneNumber (2)

76 135 144 109 90 64 77

Sources: GERG-Report PC 1 "Biogas characterization WG 1.49" (2) calculated in accordance with AVL-List

Source: MARCOGAZ recommendation

www.dvgw.de

Treatment

Depending on the utilization of the gas its treatment is required. This will generally include:

• Drying of the gas (always);

• Desulfurization (nearly always);

• Removal of inert gases as CO2 (nearly always);

• for gases deriving from fermentative processes eventually removal of biogenic substances by filtration (often not specially required, being a side effect of desulfurization);

• for gases deriving from thermal processes often methanisation (final products of many thermal gas production processes are for the best part hydrogen and carbon monoxide);

• Odorization

www.dvgw.de

Injection of biogases

Bio- and sewage gases may be treated to be used either as augmentation gas or as exchange gas for natural gas. The technical conditions shall be laid down on national base, e.g. in Germany by DVGW code of practice 262.

To achieve this, the relevant characteristics of the base gas (natural gas) in the pipeline in which shall be injected shall be regarded. In Germany, these would be the values for natural gas H or L as given in DVGW code of practice G 260.

The injection of biogases and other non-conventional gases shall be performed indiscriminative in accordance to the existing legislative requirements.

www.dvgw.de

Gas meets specs? Or doesn‘t?

Biogases may be added in two different ways: As exchange gas: the biogas is treated to a quality equivalent or

near the quality of the natural gas, i.e. fully substitutable. Such treatment is of course more expensive, but offers the possibility of access to several biogas producers as long as the pipeline capacity allows.

As augmentation gas: the biogas is not fully treated, i.e. does not meet the specification of the natural gas. Still, for a single producer access may still be possible if the resulting gas mixture meets the specification, depending on agreement between biogas producer and grid operator. However, addition of another biogas off specs might result in the entire gas mixture to become off specs; thus, a case of discrimination would result.

www.dvgw.de

In addition to the requirements for natural gas as stated in DVGW code of practice G 260, the following requirements exist for the injection of biogases :

• From DVGW G 262: max. 6 Vol.-% CO2,

max. 5 Vol.-% H2;

• from DVGW G 685 (Gas billing), 5.4.2: Variation of the gross calorific value of the gas mixture over a billing period in a grid with more than one gas quality not exceeding 2 %;

• Proof of hygienic harmlessness;

• Pressure at the level of the pipeline into which is injected.

Utilization in gas supply (German case)

www.dvgw.de

Criteria for biogas injection

• Continual injection of gas shall be possible Limitations by minimum gas sales (seasonal differences)

• Taking the local structure of the gas grid into account (Mixing zones and zones with floating zero point?)

• Good blending of biogas and natural gas / Plug formation at zones with floating zero point

• Local clients of the gas (Sensible industrial clients?)

www.dvgw.de

Adding propane/air ?

• In order to adjust the Wobbe index and the calorific value it may be necessary, depending on the local gas quality, to add propane and/or air (CO2 removal may not be sufficient)

• Questions arising from addition of propane:

• Is condensation possible?

• Will the methane number change for gas engines?

• Remuneration?

• If the law does not provide remuneration:

•a) How can the addition of propane be measured?

•b) Is this energetic part marketed separately?

• In the nearer future, many grids operated on natural gas L will be transformed to deliver natural gas H– when installing an injection plant this should be considered early.

www.dvgw.de

Examples for the injection of biogasesIn south-western Sweden some biogas plants are operated by the regional gas supply company Sydgas. The treated gas is completely injected into the gas grid.

A Swiss company (Kompogas AG) offers biogas plants comprising a closed fermenter using the content of the “green bin” as substrate. Some of these plants are operated in Switzerland, others in Germany and other countries. In the Zurich area, the gas of three such plants is treated to a quality comparable to the natural gas in the grid and injected into the local gas grid.

Since December 2006 also in Germany 2 plants comprising injection into the natural gas grid are in operation (Pliening/Bavaria and Straelen/North Rhine region). A further dozen of plants is either under construction or in planning, mostly, but not exclusively on initiative of local gas supply companies.

www.dvgw.de

Biogas plant Pliening

Source: Own pictures Uwe Klaas

www.dvgw.de

Biogas plant Pliening

www.dvgw.de

Biogas plant Laholm/Sweden

Biogas production/ Grid access pipeline

www.dvgw.de

Okay, now we‘ve got that stuff in the grid. How much to expect?

www.dvgw.de

BGW/DVGW – study“Analysis and Evaluation of possibilities for utilization of biomass in Germany“ - Objectives and basic questions

• Evaluation of the biomass potential in Germany 2006 till 2030

• Techniques of production, treatment and injection of biogas

• Possibilities of gasification of wood as a source of bio-methane

• Costs evaluation of the utilization of biogas for the production of either electric power, heat or vehicle fuel in comparison to other uses of biomass

• Environmental effects of the use of biomass

www.dvgw.de

Usable acreage till 2030

Total agricultural acreage : approx. 11,8 Mio. ha (roughly constant)

Solid fuels or substrates* for biogas

Bioethanol

Used as such

RME/Biodiesel

*These acreages may be used either for growing solid fuels or for biogas substrates

www.dvgw.de

The situation today•Biogas production almost exclusively by fermentation (recently ca. 3500 plants in Germany)

•Acreage for plant cultivation for the production of biogas: 550 000 ha

•This includes for corn (45 t/ha) with a biogas yield of 180 m³/t with 55 % methane in the raw biogas a potential of 2,4 Bill. m³/a methane = 24 Bill. kWh/a (86,4 PJ/a) by reproducible raw materials

•Total potential 72,2 Bill. kWh/a (260 PJ/a)

Industrial and commercial waste material

5%

Municipal waste

11%

Energy plants

33 %

Harvest residues,

manure, straw, grass

51%

Biogas potential distribution according to origin

www.dvgw.de

Development of the biogas potential until 2030(Results of biomass study)

0

50

100

150

200

2005 2010 2020 2030

Po

ten

zia

l B

iog

ase

rze

ug

un

g +

Ein

sp

eis

un

g g

es. [M

rd. kW

h/a

]

Biogaspotenzialgesamt

Nawaro max.

Nawaro

GŸlle

sonst. Reststoffe

Gülle

Approx. 10% of expected German natural gas consumption in 2030

Wuppertal institute expects that approx. 60% of the technical potential may

be realized. Development path rather dependant from fixed conditions and subsidizing.

Conditions:•Complete use of the biogas potential for grid injection

Reasons for growth:

•Technical progress at plant level

•Increased acreage efficiency in agriculture

•Optimized fermentation of biomass

Tot

al p

oten

tial b

ioga

s pr

oduc

tion

and

inje

ctio

n (B

ill. k

Wh/

a)

Source: Study of Wuppertal institute

Total biogas potential

Energy plants max.

Energy plants

Manure

Other waste material

www.dvgw.de

Future cooperation of agriculture and gas industry required

Biogas production

Bio natural gasBio natural gas

(treatment + injection)(treatment + injection)

CHP

Direct power production

BiogasBiogas

(Direct power (Direct power production)production)

Input:-manure, sewage-agricultural raw material (e.g. corn)-organic waste

Biogas treatment

Natural gas pipeline

New utilization pathsutilization paths:

Biomethane

Fuel sector

Heating market

CHP

Expected biogas potential

www.dvgw.de

Expected biogas potential

Acreage competition

Biomass action plan: +in the beginning, sufficient potential for further growth is present.

+ potential not used so far must be developed – as e.g. derelict land, small private forests

+ industrialized countries with a large population will depend on imports from other EU member countries and from countries outside the EU.

ALARM! Beer prices already increased in Bavaria – barley being used for biogas production!

www.dvgw.de

Bio-natural gas: markets of use

Heating market

Power market

Fuel market

EIL* / CHP law

no support

Taxadvantage

Markets for utilizationRemuneration in

accordance of use

*EIL: Energy injection law

Bio-natural gas

www.dvgw.de

Back-up Klaas Biogas Paris

www.dvgw.deSource: Biopact, Brussels

Scheme of an biogas production plant

www.dvgw.de

Potential additional hazards of biogases

The following kinds of hazard have to be taken into account: hazards on human health of end-users and for employees of e.g. the

gas industry:– direct toxicity in case of leak in a semi-confined environment;

– indirect toxicity by combustion products;

– water pollution in case of injection in subterranean storage;

– air pollution;

hazards on gas networks integrity:– Corrosion;

– clogging of pipelines and safety devices;

hazards to the safe operation of gas appliances:– Corrosion;

– clogging of safety devices

– undue change of combustion properties.

www.dvgw.de

Schematic example for the injection of gases from non-conventional sources into natural gas networks

Cleaning +

Treatment

V

H-Gasor

L-Gas

H-Gasor

L-Gas

Local utilization

Production

EN ISO 13686Methods of treatment

for the respective type of NCS

V

Laws,

directives,

technical rulesand literature

Componentsand

processes

Gas supply

|-------------------------------->

Blender

Compressor

Compressor Control devices

Exchange gas

Augmentation gas

System barrier

Control devices H-Gasor

L-Gas

H-Gasor

L-Gas

H-Gasor

L-Gas

Safety data sheet for

natural gas

www.dvgw.de

Desulfurization

Regeneratively produced gases may also be desulfurized using well established methods as e.g. the use of gas cleaning mass (iron ore).

In agricultural biogas plants the major fraction of the sulfur is precipitated by injection of a certain volume of air into the gas volume of the fermenter.

More professional and applied in many smaller treatment plants is the reaction of hydrogen sulfide with oxygen and iodine doted active charcoal to result in elementary sulfur. However, after some time the charcoal needs replacement and safe disposal.

Another method applied is the dry desulfurization of the gas by reaction of hydrogen sulfide with iron hydroxide and oxygen which also yields elementary sulfur.

www.dvgw.de

Methane enrichment/ CO2-removal

Most applied methods are the pressurized washing with either water or organic solvents, and the pressure swing absorption (PSA).

Dry methods utilize molecular sieves, active charcoal or membranes for the removal of the inert gas components.

www.dvgw.de

Drying of the gas

For nearly all applications the gas needs to be dried, depending on the choice of the other treatment methods – if dry or wet method – either at the beginning or at the end of the treatment process. For smaller plants, often cryogenic methods are applied, for larger ones e.g. glycol washes.

www.dvgw.de

Additional potential hazards associated with landfill gas and countermeasures applied

Product SourceHazardous

componentsHazard for health

Hazard related to transmission,

distribution and useCountermeasure

BiogasLandfill gas

Halocarbons

Production of dioxins and furans under burner conditions

Corrosion

Sampling and analysis for halocarbons. Exclusion of sources of known halocarbon content.

Biological agents

Possible presence of pathogenic agents (need to be demonstrated)

Biocorrosion of gas networks

Hygienization of the substrateLong digester retention timeFiltration (see note below).

SiloxanesProduction of silica under burner conditions

Sampling and analysis for siloxanes. Exclusion of sources of known high silicon content. Removal of siloxanes from product.

Ammonia Toxic gas Corrosion Removal of ammonia

Polyaromatic hydrocarbons (PAHs)

Toxic, carcinogenAffects plastic and elastomere material; sooting when burnt

Permanent monitoring and removal

Source: MARCOGAZ recommendation

www.dvgw.de

Additional potential hazards associated with biogas and countermeasures applied

Product SourceHazardous

componentsHazard for health

Hazard related to transmission,

distribution and use

Countermeasure

BiogasDigester gas

SiloxanesProduction of silica under burner conditions

Sampling and analysis for siloxanes. Exclusion of sources of known high silicon content. Removal of siloxanes from product.

Biological agents

Possible presence of pathogenic agents (need to be demonstrated)

Biocorrosion of gas networks

Hygienization of the substrateLong digester retention timeFiltration (see note below).

Ammonia Toxic gas Corrosion Removal of ammonia

Halocarbons

Production of dioxins and furans under burner conditions

Corrosion

Sampling and analysis for halocarbons. Exclusion of sources of known halocarbon content.

Source: MARCOGAZ recommendation

www.dvgw.de

Development of energy potential of reproducible raw materials till 2030

• Assumed increase of productivity: 2% p.a.

• Acreage for the production of bio diesel is assumed as more or less constant (Cultivation of rape seed for the production of bio diesel)

• Acreage increase for the cultivation of wheat for the production of bio ethanol up to 250 000 ha until 2020

Renewables wood/straw corn rapeseed wheat others

total acreage Germany

acreagetsd. ha

potentialbill.

kWh/a

acreagetsd. ha

potentialbill. kWh/a

acreage potentialbill.

kWh/a

acreagetsd. ha

tsd. ha tsd. ha

thermochemical biochemical physicochemical

pausing acreageactive acreage 2005

550 28as thermo-chemical 24

342400 150 14 100

11.825 tsd. ha1.200 ha

pausing acreageactive acreage 2020

1.150 79 68400400 250 21 200 2.000 tsd. ha

pausing acreageactive acreage 2030

1.600 14 115400400 250 26 350 2.600 tsd. ha

www.dvgw.de

Specific requirements for NCS gas injection Austria France Germany Netherlands Sweden Switzerland

Property UnlimitedInjection

Limitedinjection

CH4> 96 % / - 85% >97% >96% >50%

CO2< 3 % <2,5% 6% / <3% <4% <6%

CO <2% / / / / /Total S < 10 mg/m³ < 30mg/m³ 30 mg/m³ <45 mg/m³ < 23 mg/m³ < 30mg/m³ < 30mg/m³

H2S < 5 mg/m³< 5 mg/m³

(H2S+COS) 5 mg/m³ < 5 mg/m³ 10 ppm < 5 mg/m³ < 5 mg/m³

Mercaptans < 6 mg/m³ <6 mg/m³ 15 mg/m³ / / / /O2

< 0,5 % <0,01% <0,5% <0,5% <1% <0,5% <0,5%

H2< 4 % <6% 5 % / <0,5% <5% <5%

H2OWater dew point

-8°C/40 barWater dew point<-5°C at MOP

Water dew point:Ground

temperature<32 mg/m³ <32 mg/m³ <60% <60%

Hydrocarbon dew point 0°C at OP <-2°C (1-70 bar) Ground

temperature / / / /

Wobbe index 13,3 – 15,7kWh/m³

13,64-15,7 kWh/m³ for H gas

12,01-13 kWh/m³ for B gas

10,5 – 15,7 kWh/m³ 43,6-44,41 MJ/m³

45,5-48,5 MJ/m³ 13,3-15,7 kWh/m³ /

Pressure Pressure of pipeline to be injected into

Gross calorific value

10,7-12,8kWh/m³

10,7-12,8 kWh/m³ for H gas

9,5-10,5 kWh/m³ for B gas

/ 35,1 MJ/m³ / 10,7-13,1 kWh/m³ /

Relative density 0,55-0,65 0,555-0,70 / / / 0,55-0,70 /

OdorantGas to be

odorized at consumer

15-40 mg THT/m³ Gas to be odorized at consumer

Gas to be odorized at consumer

/ 15-25 mg THT/m³ 15-25 mg THT/m³

Impurities Technically pure Technically pure Technically pure Technically pureHalogenated compounds 0 mg/m³ < 1 mg Cl /m³

< 10 mg F /m³ nil < 25 mg Cl/m³ / /

Ammonia Technically pure / / <3 mg/Nm³ <20 mg/Nm³ / /

Dust Technically pure / No dust No dust

Mercury < 1 μg/m³ / / / / /

Benzene

Siloxanes < 10 mg/m³

www.dvgw.de

Gas quality requirements in different countriesAT BE DK DE FR IT NL4 ES UK

Reference Temperature, °CVolumeEnergy

025/0 0

25/0025/0

025/0

00/0

1515/15

025/0

00/0

1515/15

GCV X X X X X X

Wobbe index X X X X X X

Density X X X X

Methane number

Hydrocarbon dew point X X X X X

Water dew point X X X X X X

Sulfur

Total X X X X X X X

H2S X X X X X X X X

Odorant2, 3 X X X

Mercaptan X X X

COS X

Other indices1

Comb. Potential

Lift Index

ICF X

Soot index X

CO X

Carbonyl metals

Impurities (liquids, solids) X X X X X

CO2X X

N2X

O2X X X X

H2X X

Aromatics5

NH3X X

Hg5 X

Source: MARCOGAZ recommendation

www.dvgw.de

Advantages of bio-natural gas in comparison with other regenerative energy resources

Sustainability The production of bio-natural gas offers a closed material circuit.

Low pollutant emissions Bio-natural gas burns just like natural gas and offers adequate emission advantages: very low NOx and CO values, no fine dust.

Versatile utilization The flexibility in the areas of utilization traffic, heating market and power production is outstanding.

Highest efficiency in traffic application

Compared with other biogenic fuels bio-natural gas offers the highest fuel harvest per acre. With bio-natural gas from 1 acre the mileage is triple than that of the bio diesel to be gained from an acre.

Suitable for base load The bio-natural gas from a biogas plant delivers steady energy for approx. 8.000 hrs/a.

Storable In conjunction with the natural gas grid and storages bio-natural gas becomes a storable energy.

Controllable Opposite to solar or wind power bio-natural gas is a controllable energy.

No additional logistics Bio-natural gas may be transported through the natural gas grid in a safe, environmental friendly and at reasonable costs. Means of transport as e.g. lorries are not required.

No depreciation of investment

The entire natural gas infra structure and the equipment at the user’s premises may be used without limitation. Thus, no investment depreciation.

Immediately useable The market penetration with efficient techniques of utilization enable already today the unrestricted use of bio-natural gas without additional investment for the natural gas/bio-natural gas client.

Low space requirements A storage for e.g. wood pellets or chippings at the user’s premises is not required. To store the energy content of 100 l heating oil in shape of wood chippings approx. 1 m³ is required.

Defined quality Bio-natural gas offers the same defined, constant quality as natural gas and shows no variation of quality as wood, wood chippings or pellets.

www.dvgw.de

Bio-natural gas for CHP - Specific greenhouse gas emissions in 2010

Power from mix

Power from natural gas

Power from biogas

Heat from mix

Heat from biogas

www.dvgw.de

Bio-natural gas: markets of use

Heating market

Power market

Fuel market

EIL* / CHP law

no support

Taxadvantage

Markets for utilizationRemuneration in

accordance of use

*EIL: Energy injection law

Bio-natural gas

www.dvgw.de

Bio-natural gas as vehicle fuel

Sustainability with bio-natural gas in traffic:Achievable kilometreage with the energy of one hectare

*Bio-natural gas from by-products (rapeseed cake, slurry, straw) vehicle fuel consumption: Otto engine 7,4 l/100 km, Diesel engine 6,1 l/100 km

BtL (Biomass-to-Liquid)4.030 l

Bio-natural gas3.560 kg

Rapeseed oil1.480 l

Bio diesel1.550 l

Bio ethanol (from grain) 2.500 l

Source: Fachagentur Nachwachsende Rohstoffe

www.dvgw.de

Bio-natural gas: markets of use

Heating market

Power market

Fuel market

EIL* / CHP law

no support

Taxadvantage

Markets for utilizationRemuneration in

accordance of use

*EIL: Energy injection law

Bio-natural gas

www.dvgw.de

Bio-natural gas as heating carburantSpecific costs of bio-natural gas to avoid CO2-emissions are significantly lower for new buildings

Specific costs to avoid CO2- emissions

Energy requirement/ Insulation level

Example: House equipped with natural gas recondensing boiler

Insulation: very high additional investments, long durability

Environmental heat (solar, heat pump): significant additional costs

Bio-natural gas: lowest costs despite higher carburant costs

www.dvgw.de

The German gas industry and biogas

The German gas industry is, in cooperation with agriculture, committed to create a competitive biogas market. This is also expressed in the declaration of commitment issued by the BGW, the German Association of the German gas and water industries, on 24 August 2007.

The objectives set by the politicians are: the share of renewables in energy supply of new private homes

shall be 20 %; the dependency from natural gas imports shall decrease; the emission of greenhouse gases shall be significantly reduced; the development of energy production from renewables will create

some 100.000 new jobs in the country.

www.dvgw.de

Bio-natural gas market – Preliminary conclusion

• Market predetermined by politics

• Fast growth possible

• Economical viable

• Existing support systems improvable

• Risk of political misguidance

www.dvgw.de

Biomass potential in Germany:systems

Biogeneticprimary energy Conversion Secondary energy Final utilization of

energy

Technical energy carrier potential Possible contribution of biomass to the supply of Energy

PressingEsterization etc.Rape seed Bio diesel (RME) Use as

vehicle fuel

Waste wood Chipping Wood chipsHeat production

MaisFertilization Biogas Power production

Examples:

Corn

Manure

www.dvgw.de

BGW/DVGW – study“Analysis and Evaluation of possibilities for utilization of biomass in Germany“

In January 2006 a study initiated by the associations of the German gas and water industry BGW and DVGW was published. The steering committee comprised besides representatives of the gas industry also the German biogas association (Fachverband Biogas e.V.), the German farmers association (Deutscher Bauernverband), the federal German ministry for the environment, the federal German ministry for consumer protection and agriculture and the states ministries for agriculture and for the economy and energy of Bavaria. The study was performed under conduct of the Wuppertal institute, split into work packages, by the institute for energetics (IE Leipzig), the Fraunhofer institute for the environment, safety and energy techniques (UMSICHT, Oberhausen) as well as the gas heat institute (Gaswärme-Institut GWI, Essen)