Characterization and Comparison of Trace Metal Compositions in Natural Gas, Biogas, and Biomethane

Biogases are a renewable energy source intended to facilitate the energy transition from natural gas in various domains such as heat and electricity production. The composition of biogas and biomethane is well-known in terms of major compounds, which include methane, carbon dioxide, and hydrogen sulfide. However, the trace element composition of these gases is poorly documented. For the first time, trace metal composition of biomethane produced from agricultural waste and biogas generated at a nonhazardous waste landfill and intended to produce electricity by cogeneration is presented in this work and is compared to the trace metal composition of natural gas. A dedicated high-pressure bubbling sampler was used to sample gas at different operating pressures ranging from 1 to 40 bar. Multiple wide-ranging screenings of metals and metalloids were conducted regarding the elements Se, Cd, Ni, Sb, As, Zn, Pb, Sn, Cr, Ba, Al, V, Mo, Cu, and Ag. The metal concentrations in the sampled natural gas and biomethane were found to be at the same order of magnitude and ranged from 10–1to 102ng/N m3, although some differences in the details were observed. Compared with the metals in those two gases, the metals in the biogas were at higher concentrations, ranging from 1 to 103ng/N m3.