These commercially available technologies have proven to be both technically and economically feasible. Lars-Evert Karlsson, global product line manager for Bremen, Germany-based Purac Puregas, which designs and delivers biogas upgrading plants, says biogas production is growing around the world and there is an increasing demand for upgraded biogas to be used as vehicle fuel or injected to the natural gas grid. “To enable the efficient use of biogas in these applications, the gas must be upgraded—for example, the carbon dioxide, which constitutes a large part of the raw biogas from the digester, must be separated from the methane,” he says. “Methods commercially available today include amine scrubbers, water scrubbers, pressure swing adsorption (PSA) units, organic scrubbers and membrane units.” Ricardo Hamdan, management consultant for Greenlane Biogas Limited, Vancouver, British Columbia, says amine and cryogenic methods are also used, but are less common than water scrubbing, pressure swing absorption and membranes due to their higher cost. A recent Swedish Gas Technology Centre (SGC) report written by Fredric Bauer, Christian Hulteberg, Tobias Persson and Daniel Tamm shows that for midscale applications, the most common options are all viable. “The scrubbing technologies all perform well and have similar costs of investment and operation,” says Karlsson, who contributed to the SGC report. “The simplicity and reliability of the water scrubber has made this the preferred choice in many applications, but the high purity and very low methane slip from amine scrubbers are important characteristics.” The SGC report finds that the investment costs for PSA and membrane units are about the same as they are for scrubbers, yet recent developments of the membrane units have made it possible to reach low methane slips. Hamdan and Greenline contributed to the recent American Biogas Council’s interactive report, “Biogas to Biomethane/Renewable Natural Gas,” which explains how each of the methods work. “It is an OPEX vs.
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