Jenbacher Biogas Engine
Jenbacher biogas engines use the biogas from anaerobic fermentation of organic waste from agriculture, foodstuff or feed industries. This fuel can substitute for fossil fuels.
The global installed base of almost 1,300 GE Jenbacher gas engines running on biogas has the capacity to generate more than 6.8 million MWh of electricity per year without burning fossil fuel, equivalent to the annual electricity demands of over 617,000 US households, over 1.6 million European households or over 1.5 million urban Chinese households.
One GE Jenbacher J420 gas engine running on biogas has the capacity to generate almost 11,000 MWh of electricity per year without burning fossil fuel, equivalent to the electricity generated by the combustion of more than 15,300 barrels of oil, more than 2.7 million cubic meters of natural gas, or over 3,400 metric tons of coal based on typical generation efficiencies.
Milk and power
Disposal and treatment of biological waste represent a major challenge for the waste industry. For a wide range of organic substances from agriculture, foodstuff or feed industries, anaerobic fermentation is a superior alternative to composting. Biogas – a mixture of methane and carbon dioxide - is created during anaerobic fermentation and serves as a fuel that can be used as a substitute for fossil fuels. Biogas-fueled gas engines improve waste management while maximizing the use of an economical energy supply.
Generation of biogas
Biogas results from anaerobic fermentation of organic materials. As a metabolic product of the participating methane bacteria, the prerequisites for its production are a lack of oxygen, a pH value from 6.5 to 7.5 and a constant temperature of 15 degrees C (psychrophile), 35 degrees C (mesophile) or 55 degrees C (thermophile). The fermentation period is approximately 10 days for thermophiles, 25 to 30 days for mesophiles and 90 to 120 days for psychrophile bacteria. The fermentation systems of today operate largely within the mesophile temperature range.
The Jenbacher concept
The process of biogas generation is divided into three steps:
- Preparation of the bio-input
- Post-treatment of the residual material
At the start, the organic material is collected in a primary pit, sterilized to remove harmful germs and moved to the digester. The biogas produced in the digester is collected in a gas storage tank to ensure a continuous supply of gas independent of fluctuations in the gas production. Finally, the biogas is fed into a gas engine. For safety reasons, the installation of a gas flare is recommended so that excess gas can be burned off in the event of excessive gas production. The end product from the fermentation of the biomass can be utilized as fertilizer. The gas mixture produced in the digester consists of 60 percent to 70 percent methane (CH4) and 30 percent to 40 percent carbon dioxide (CO2). This composition makes biogas well suited for combustion in gas engines.
The generated electrical energy can be utilized for the treatment plant as well as to supply the public power grid. The thermal energy can be used for heating the digester or to offset the heat requirements of the treatment plant.
Suitable organic materials
Among others, the following organic materials are suitable for the generation of biogas. The figures in brackets show the biogas yield in Nm³ per ton of moist material:
- Liquid manure, solid dung (20 – 70)
- Separately collected biowaste from households (10 – 200)
- Secondary-growth raw materials, e.g., corn silage, non-food grains (180 – 300)
- Sewage sludge and grease sludge (80 – 150)
- Old grease (1,000)
- Grass, e.g., from EU set-aside areas (150 – 200)
- Biowastes from slaughter houses (100), breweries and distilleries (20), fruit and wine press houses (30), dairies (25), the cellulose industry or sugar production (40 – 60)
The dung of approximately 2,500 cows, 15,000 hogs or 300,000 laying hens is required to operate a cogeneration plant with an electrical output of 500 kW – corresponding roughly to the demand of 200 households. Wood is not suitable for biogas production because the lignin it contains is indigestible to methane bacteria. Pesticides, disinfectants and antibiotics also have a negative effect on the bacteria and on biogas formation.
- Alternative disposal of dung, liquid manure and biowaste while simultaneously harnessing them as an energy source
- High potential for reduction of greenhouse effects (biomass is a CO2-neutral, renewable energy source)
- Biogas is a substitute for conventional fuels
- Highly efficient for on-site power and heat generation
- The remaining substrate from the digester can be used as high-quality, agricultural fertilizer:
- The corrosive effect (e.g., of liquid manure) is neutralized by the higher pH value
- The fermentation waste is nearly odorless
- Plant nutrients are retained, resulting in good fertilizing properties
Jenbacher cogeneration technology fueled with biogas enables maximum economic and ecological benefits to be realized. Currently more than 290 Jenbacher Biogas systems with a total electrical output of over 180 MW are in operation worldwide. Continued development of anaerobic fermentation applications are leading to greater opportunities for the utilization of Biogas for energy production.