Open AccessChemical and Toxicological Properties of Emissions from a Light-Duty Compressed Natural Gas Vehicle Fueled with Renewable Natural Gas
Author(s) -
Yin Li,
Jian Xue,
Joshua Peppers,
Norman Y. Kado,
Christoph F.A. Vogel,
Christopher P. Alaimo,
Peter G. Green,
Ruihong Zhang,
B. M. Jenkins,
Minji Kim,
Thomas M. Young,
Michael J. Kleeman
Publication year - 2021
Publication title -
environmental science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.851
H-Index - 397
eISSN - 1520-5851
pISSN - 0013-936X
DOI - 10.1021/acs.est.0c04962
Subject(s) - compressed natural gas , natural gas , waste management , environmental science , methane , exhaust gas , diesel fuel , renewable natural gas , chemistry , environmental chemistry , fuel gas , engineering , combustion , organic chemistry
Biogas consisting primarily of methane (CH 4 ) and carbon dioxide (CO 2 ) can be upgraded to a transportation fuel referred to as renewable natural gas (RNG) by removing CO 2 and other impurities. RNG has energy content comparable to fossil compressed natural gas (CNG) but with lower life-cycle greenhouse gas (GHG) emissions. In this study, a light-duty cargo van was tested with CNG and two RNG blends on a chassis dynamometer in order to compare the toxicity of the resulting exhaust. Tests for reactive oxygen species (ROS), biomarker expressions (CYP1A1, IL8, COX-2), and mutagenicity (Ames) show that RNG exhaust has toxicity that is comparable or lower than CNG exhaust. Statistical analysis reveals associations between toxicity and tailpipe emissions of benzene, dibenzofuran, and dihydroperoxide dimethyl hexane (the last identification is considered tentative/uncertain). Further gas-phase toxicity may be associated with tailpipe emissions of formaldehyde, dimethyl sulfide, propene, and methyl ketene. CNG exhaust contained higher concentrations of these potentially toxic chemical constituents than RNG exhaust in all of the current tests. Photochemical aging of the vehicle exhaust did not alter these trends. These preliminary results suggest that RNG adoption may be a useful strategy to reduce the carbon intensity of transportation fuels without increasing the toxicity of the vehicle exhaust.