Biochars as Potential Adsorbers of CH4, CO2 and H2S

Abstract

Methane gas, as one of the major biogases, is a potential source of renewable energy for power production. Biochar can be readily used to purify biogas contaminants such as H 2 S and CO 2 . This study assessed the adsorption of CH 4 , H 2 S, and CO 2 onto four different types of biochars. The adsorption dynamics of biochars were investigated in a fixed-bed column, by determining the breakthrough curves and adsorption capacities of biochars. The physicochemical properties of biochars were considered to justify the adsorption performance. The results showed that CH 4 was not adsorbed well by the subjected biochars whereas CO 2 and H 2 S were successfully captured. The H 2 S and CO 2 breakthrough capacity were related to both the surface adsorption and chemical reaction. The adsorption capacity was in the following order: perilla > soybean stover > Korean oak > Japanese oak biochars. The simultaneous adsorption also leads to a competition of sorption sites. Biochars are a promising material for the biogas purification industry.

Pilot-Scale Testing of Non-Activated Biochar for Swine Manure Treatment and Mitigation of Ammonia, Hydrogen Sulfide, Odorous Volatile Organic Compounds (VOCs), and Greenhouse Gas Emissions

“…Carbon dioxide and N 2 O emissions resulted in no significant difference over any of the trials. The lack of reduction in emissions of CH 4 is in agreement with Sethupathi et al [30], where it was reported that tested biochar capacities to adsorb CH 4 were little to none. Sethupathi et al [30] also reported the CO 2 adsorption capacity for the same biochar discussed earlier in regards to H 2 S adsorption, with a low capacity when tested as a mix of gases.…”

“…The lack of reduction in emissions of CH 4 is in agreement with Sethupathi et al [30], where it was reported that tested biochar capacities to adsorb CH 4 were little to none. Sethupathi et al [30] also reported the CO 2 adsorption capacity for the same biochar discussed earlier in regards to H 2 S adsorption, with a low capacity when tested as a mix of gases. This low CO 2 adsorption capacity in the presence of other gases equates to <1 h before the biochar's capacity is reached under conditions observed in this study at all biochar doses.…”

“…Reduction of H 2 S was also Sustainability 2017, 9, 929 8 of 17 observed during Trial 3 at a biochar dose of 1.14 kg·m −2 over 9 days (30%), but this was not significant. Sethupathi et al [30] determined adsorption capacities for H 2 S on various biochars such as Japanese oak biochar produced at~500 • C (the closest biochar to this study). Sethupathi et al [30] reported adsorptions of 5.69 mg H 2 S·g biochar −1 when H 2 S was tested alone and 0.613 mg H 2 S·g biochar −1 when H 2 S was tested in a gas mixture with CO 2 and CH 4 .…”

“…Sethupathi et al [30] determined adsorption capacities for H 2 S on various biochars such as Japanese oak biochar produced at~500 • C (the closest biochar to this study). Sethupathi et al [30] reported adsorptions of 5.69 mg H 2 S·g biochar −1 when H 2 S was tested alone and 0.613 mg H 2 S·g biochar −1 when H 2 S was tested in a gas mixture with CO 2 and CH 4 . The reported biochar adsorption capacity for H 2 S when mixed with CO 2 and CH 4 equates to~311 days, at a biochar dose of 4.56 kg·m −2 , of H 2 S emissions observed in this study.…”

The experimental study of biogas production when digesting chicken manure with a biochar additive

“…Pine biochar contains more carboxyl groups and fewer oxygen groups, which confirms the assumption that this biochar is a suitable material for immobilizing of microorganisms in pores and on the surface of biochar. Scientists have investigated the use of a biochar additive made of various plant species for adsorbing CH 4 , CO 2 and H 2 S from single gases and multi‐component gas mixtures . The studies have shown that the considered biochar additive has the highest capacity of adsorbing CO 2 and H 2 S, while its capacity of adsorbing CH 4 is the lowest in the case of adsorption from single (pure) gases.…”