High-efficiency methane capture by living fungi and dried fungal hyphae (necromass).

Fungi can hasten microbial degradation of hydrophobic compounds by enhancing capture and dissolution into biofilms. For methane (CH4 ) released from natural soils and agricultural systems, prokaryotes are ultimately responsible for oxidation and degradation; however, in many cases Henry's law of gas dissolution, not oxidation, is rate-limiting. Given that fungi can improve capture and bioremediation of other hydrophobic compounds (e.g., toluene), we tested fungi for CH4 capture. We used a batch system of CH4 -flooded vials to screen candidate fungi. We found 79% removal efficiency by Ganoderma lucidum relative to activated carbon. In a follow-up, we found comparable efficiency in other Ganoderma species (G. applanatum, G. meredithae). However, these efficiency gains by Ganoderma species could not be sustained when inoculated wood substrates were placed in "live" soils. Substrates colonized naturally, without preinoculations, performed similarly to those deployed with (native) test strains, likely because inoculated fungi were outcompeted and displaced by native colonizers. Instead of rescreening using more combative fungi, we tested an alternative way to present fungi with high single-strain efficiencies for filtration: in dried form as dead biomass (necromass). In dried biomass trials, dried G. lucidum biomass performed better than when testing living biomass, again with the highest strain-specific removal efficiencies (84% of activated carbon). These results demonstrate the potential for G. lucidum, commonly used in biomaterial production, in a variety of indoor and outdoor biofiltration scenarios. It also implies an overlooked, potentially large role for fungi and their soil necromass in capturing and reducing CH4 emissions from soils in nature.