Biogas Production for Energy in Germany -Residues from Food Industry-

1. Biogas Production for Energy in Germany-Residues from Food Industry- Prof. Dr. Bernd Stephan University of Applied Science Bremerhaven, Germany

2. Anaerobic Digestion: Biogas History • History in Germany starting with utilization of „marsh gas“ in the 19th century: gas tight drums with an diameter of about 2 to 3 meter were placed upside down into the wet lands for gas collection and gas utilization for cooking – similar to the Indian Gabor Gas Plant • Beginning around 1920 trucks of public services were operated with compressed biogas from digestion of sewage sludge – in the fifties ot the 20th century this was given up due to low cost mineral oil • In the fifties last century some farmers build biogas plants for the treatment of aninmal wastes – the technology was based on different principles • The oil price crisis in the seventies stimulated broad activities on the research and implementation side of agricultural biogas plants and resulted in optimized plant design and process performance. About 200 plants were bulit and operated at that time, but could not compete with the market prices for gas or liquid hydrocarbons. • The energy policy of German Federal Government now subsidies the utilization of renewables – a result the market for big biogas plant goes up (most of them are connected to cogeneration plants)

3. Basics Substrates must be degradable Substrates must/should be available at a constant mass/volume flow Substrates should have a nearly constant composition Concentration of organic dry matter should be higher than 2 % Substrates should be a liquid slurry Digester volume should be more than about 100m3

4. Biogas Production process: the main steps • Collection and (pre)treatment • Producing a slurry with balanced composition (e.g. water-content, total organic solids. C/N ratio) • Feeding of reactor with constant rate • Keeping fermenter at nearly constant temperature of about 33o Centigrade • Mixing of substrate during fermentation • Gas collection, purification, utilization (heat and electricity) • Collection and utilization of fermented slurry e.g as high value organic fertilizerer

5. Animal excreta 4.5 Vegetable residues from agriculture 3.0-5.3 Wastes from Industry 0.3-0.6 Waste from parks and gardens 0.3-0.6 Organic municipal waste 0.6 Energy crops 3.7 TOTAL 12.7-15.3 (billion m3/a) total (PJ/year) electric. (TWh/a) 96.5 7.2 65-113 4.9-8.5 6.4-12.2 0.5-0.9 6.4-12.2 0.4-0.8 12.5 0.9 78.7 5.9 265.1-324.9 19.8-24.2 Potential of Biogas (Wilfert, R. et al., Institut für Energetik und Umwelt Leipzig, 2002)

6. Food industry with suitable substrates – some examples • Slaughterhouses • Canneries • Diaries • Distilleries • Breweries • Starch production • Sugar industry • Big restaurants/kitchens

7. Biogas plant implemention in Germany (1) • Today nearly all biogas plants in Germany designed and operated for residues of food industry use mixed substrates as feeding material cofermentatation of agricultural waste, effluents with organic load from food industry and similar facilities, energy crops, organic residues from the households • Plant size and technology depend on the specific substrate mixture and pattern of energy utilization and waste management • Nearly all plants produce electricity and use the excess thermal energy for specific purposes

8. Biogas plantimplemention in Germany (2) • The number of plants increased during the last years from about 190 in 1992 to about 2000 in 2004 • Installed electrical capacity increased from 50 MW per year in 1999 to about 270 MW per year • In North-East Germany 70 % of the plants treat more than 7500 m3 of slurry per year, the average treatment capacity in Germany is in the range of 1000 to 2000 m3 per year

9. Biogas plantimplemention in Germany (3) • Plant design depends on substrate properties • Typical patterns are: mesophilic fermentation of a slurry, normally with a pretreatment facitity (collection unit with mechanical components for mixing) and a storage tank for the fermented material • Fermenters are totally mixed air-tight reactors with integrated heating systems and thermal insulation, in some cases (e.g. low content of organic matter) up-flow reactors are used or flotation as pretreatment (concentration of organic matter) • The collection tank usually has a storage capacity for some days of operation • Retention time for fermentation is in the range of 20 to 30 days • Power station to produce electricity (gas engine coupled with generator)

10. Low pressure gas storage, integrated into the fermenter (gas cap) or separated Gas consumption directly after production Biogas is dewatered and desulfurized before combustion Most of the engines (70 %) are modified diesel engines, which use a jet of gas oil for ignition of biogas Excess heat is used to warm up water for specific purposes e.g. heating of the fermenter, buildings, process water for cleaning or for food processing Biogas plantimplemention in Germany (4)

11. Planning Data 1 (general) Biogas potential: total organic solids (%) m3 CH4/m3 substrate Waste water, municipal 0.05 0.15 Waste water, food industry 0.15 0.5 Sewage sludge 2 5 to 10 Cow manure 8 20 to 30 Pig manure 6 to 8 30 to 50

12. Planning Data 2: effluent of slaughterhousesSubstrate: mixture of cow manure and slaughterhouse waste waterQuantity: 50 m3 per daycontent of organic matter: 4%gas producion per day : 1000 to 1500 m3Energy production: 6000 to 9000 kWh per day,1/3 electrical, 2/3 thermal energyRetention time: 20 daysDigester volume: 1000 m3

13. Contributions of Biogas for Energy Supply 2004 • The potential of biogas for producing electricity comes to 4% of the annual consumption of electric energy (public grid) • The contributions today comes to 0,002 % of the potential only – great potential

14. Reasons • Regional pattern of substrate availability and of (local) energy demand • Distribution cost • Biogas technology had its great start up since 2000 • Internal utilization of electricity

15. Installed electrical capacity (MW)1999 502000 752001 1102002 1602003 2202004 2702005 350 (estimated)

16. Example of Implementation- a typical cluster - • Biogas plant using agricultural waste, slaughterhouse waste and sewage sludge • Thermal energy used for slaughterhouse • Electrical energy sold to the public grid at subsidies prices

17. Biogas plant „Brensbach“

21. Basic Data(plant under construction, some figures estimated) • Digester volume 4 800 m3 • Mesophilc process 33-35 oC • Retention time 20 days • Input (organic dry matter) 9 600 to 14 400 kg/day • Treated slurry 80 000 m3/year • Sludge utilization liquid fertilizer • Energy output 3000 to 4500 m3/day 6 to 9 million kWh/year electrical 2 to 3 million kWh/year thermal 4 to 6 million kWh/year

22. Some aspects • Great market potential • Cost reduction for plant components with increasing implementation • Positive effects by standardization, increasing skillness/experience and competition of biogas-companies • Cost of substrates/cosubstrates will go up • Energy crops from East Europe? • Phosphate recovery from fermented sludges?

23. Some Aspects for Future Biogas Development in Thailand • Analysis of Potential for implementation • Cofermentation (are there „biogas clusters“?) • Energy demand electrical and thermal in agro industry • Gas Separation CH4/CO2: e.g. compressed methan as fuel for automotives; CO2 for industriy (e.g.beverages) • Improvement of fertility of soil • Used oils from kitchen and residues of restaurants • Future environmental policy for cities should focus on biogas too as a decentralized system for waste treatment