Technologies for biogas utilisation: “Getting more energy for less effort in 5 steps”
Lems, R., Linnemans, M. and Dirkse, E.H.M., DMT Environmental Technology, The Netherlands
(free)
Abstract:
Biogas is one of the most promising energy sources for the future. Biogas is a product from e.g. landfill sites or digesters that can be applied as a green and renewable energy source with no global emissions on CO2 and hardly no local emissions on other pollutants. The only question is what is the best way of utilizing the energy captured in the gas.
The energy can be used direct and indirect as heat, (mechanical) movement and/or electricity. The gas can be burned in a boiler to produce process heat, in an gas engine to produce electricity or a CHP for electricity and heat. But it can also be upgraded to natural gas quality for injection in the gas grid or utilization as vehicle fuels.
Biogas can be converted to CNG in 5 steps. After each step the biogas can be utilized against a higher energy efficiency and/or high energy value. First step is drying of the gas making it suitable for e.g. simple boiler. Next step is desulphurization after which the gas can be utilized in a simple CHP. After the third step, siloxane removal, the gas can be used to produce electricity at the highest efficiency with sophisticated gas turbines. In the fourth step also the CO2 is removed from the biogas, resulting in almost pure methane with the same qualities as natural gas, which can be injected in the local gas grid. Finally the gas can be pressurized to 220bar at which it can be used as vehicle fuel as substitute for CNG.
In this paper for each step different technologies and their impact is attended. The figures are supported with operational plants like the Sulfurex® system, which is a two stage chemical scrubber that combines desulphurization and biogas drying. Biological desulphurization is possible with the Bio-Sulfurex® while siloxanes can be removed by e.g. activated carbon. Finally CO2 can be removed by gas selective membranes or pressurized water scrubbing with the CarbO2rex® systems.
Each step of biogas treatment and utilization will be illustrated with practical examples and field data.
Key words
Biogas utilisation, desulphurisation, drying, siloxane removal, upgrading, natural gas, pressurized water scrubbing, heat reuse, methane recovery.
