Renewable CNG with Combined Heat and Power Provides Flexible End Use for Biogas

Beneficial use of biogas has for many years looked to combined heat and power (CHP) projects to maximize the use of biogas energy. However, public utilities and private enterprises are now looking at fuel production to get a better return for biogas produced and to provide flexibility in the end use for biogas. It is now economical to upgrade biogas by removing carbon dioxide (CO2) at a scale applicable small to and medium size producers of biogas; including many wastewater treatment plants, industrial anaerobic treatment systems, and organic waste digesters. Biogas is separated into a product gas with a methane content from 95 to 99 percent creating a renewable CNG vehicle fuel.CNG is used worldwide as a vehicle fuel. There are currently more than 13 million CNG vehicles in use. Research done by the Argonne National Laboratory suggests that compressed natural gas (CNG) produced from biogas has the lowest greenhouse gas (GHG) potential of any vehicle fuel; lower than ethanol and biodiesel.Concentration of the methane in the product gas also yields an off-gas that contains a portion of the methane. The off-gas can be managed to obtain energy value in combined-heat and power systems such as microturbines or engine-generators. Off-gas can be recycled to the intake, blended with natural gas or blended with additional biogas to obtain a gas with sufficient energy content to operate a generator.Vehicle fuel is generally the highest value end use for biogas. High electric rates can also product significant revenue. But the production vehicle fuel has the additional benefit for price stability compared to petroleum-based fuels.This presentation will provide 2 examples of gas treatment systems providing a total solution for biogas utilization.