Energy and Greenhouse Gas Emissions of Renewable Natural Gas as Vehicle Fuel

Abstract

Today more than 300 million standard cubic feet per day of natural gas and 1,680 MW of electricity are produced from the decomposition of organic waste at 541 U.S. landfills. Since landfill gas (LFG) is a renewable resource, this energy is considered renewable. When used as a vehicle fuel, LFG-based compressed natural gas (CNG) consumes up to 1,100 Btu of fossil fuel and generates up to 120 g of carbon dioxide equivalent (gCO2e) greenhouse gas emissions per mile on a well-to-wheel basis. This amount compares with about 7,500 Btu and 500 gCO2e per mile for CNG from fossil natural gas and 8,000 Btu and 650 gCO2e per mile for petroleum gasoline. Liquefying the LFG consumes another 400+ Btu of fossil fuel and 30+ gCO2e per mile if grid electricity is used for the process. However, if some of the LFG is used to generate electricity for gas cleanup and liquefaction (or compression), liquefied natural gas (or CNG) produced from LFG can have no fossil fuel input and only minimal CO2e emissions on a well-to-wheel basis. This renewable natural gas is among the lowest carbon fuels in compressed or liquid form.