The role of fungi in biofiltration of livestock emissions: Full-scale and bench-scale observations

Background/Question/Methods

The impact of livestock production and manure management on air quality is an increasingly recognized and significant problem.  Wood chip biofilters (WCBs) have the potential to treat these complex emissions, but removal efficiencies are variable.  Expanding the capabilities of WCBs and developing effective management practices requires a better understanding of how microbial communities affect emissions reductions.  Most research investigating the link between ecology and function in WCBs has been focused on prokaryotes, neglecting the potential importance of fungi in these systems.  We hypothesize that fungi are crucial to WCB performance due to their filamentous, web-like growth and tolerance to desiccation.  Using wood chip baits of known surface area incubated in a full-scale biofilter, we are adapting microbial biomass measures successfully applied in other systems to develop a monitoring tool for fungal biomass in WCB biofilms.  Fungal ergosterol and total microbial biomass, determined by the chloroform fumigation extraction (CFE) technique, are being used to measure biomass ratios.  Additionally, the performances of fungal dominant biofilters are being tested at bench-scale.  Biofilter assemblies packed with different inoculated systems are continuously filtering field relevant manure emissions.  Routine monitoring of full- and bench-scale WCB inlet and outlet emissions is used to determine performances. 

Results/Conclusions

Early efforts to apply biomass measures to WCBs identified the need to remove biofilms from wood chip baits prior to analysis and to increase sample size through pooling.  For both ergosterol and CFE, at least 100 mg of biofilm must be used for repeatable results with larger sample sizes further reducing variability.  Preliminary field data demonstrates fungal:total biomass ratios change across location and time and are effected by abiotic conditions of the WCB media.  In bench-scale WCBs, fungal dominant systems better capture ammonia during the start-up phase.  Following an intentional desiccation stress on the system, fungal WCBs begin to outperform other treatments in capture of the hydrophobic gas methane.  Differences between treatments are also being observed with other emissions.  As bench-scale results are identifying importance of fungi in these systems, we continue to collect field data with our adapted technique to explore their role in full-scale biofiltration of livestock emissions.