Greenhouse Gas Emission and Groundwater Pollution Potentials of Soils Amended with Different Biochars.

The objective of this research is to study the greenhouse gas emission impacts, effect on native soil organic matter (SOM) degradation, and groundwater pollution potentials of soils amended with various biochars using different biomass feedstocks and production conditions.  Small pots were set up in triplicate with treatments as follows: 1) control soil consisting of Histisol and Entisol and 2) soils amended with different biochars at a rate of 5 g kg^-1 (10 ton/ac).  Biomass feedstocks for different biochars include bagasse, switch grass, macadamia nutshells, wood chips and pellets, and swine solids.  Individual and blends of these biomass feedstocks are processed via both dry and hydrothermal carbonization techniques.  After the biochars are mixed into the soil, its moisture in the laboratory experiments is maintained gravimetrically at 10% (w w^-1) by replenishing with D.I. Water.  After 30 days of incubation, the pots will be leached with 1.2 to 1.3 pore volumes of deionized H₂O to simulate flushing.  The leachates will be collected and analyzed for oxygen-demanding water quality parameters (e.g., BOD, COD, TOC), nutrients (N, P, K, Na, Ca, Mg, Mn, Fe, B), and heavy metals (Cd, Cr, Cu, Ni, Zn).  Soil samples from the initial set up along with samples at the end of the incubation study will be extracted with reagents to provide plant available nutrient concentrations. Emissions of greenhouse gases (CH₄, CO₂, and N₂O) and other volatile compounds (VOCs) (e.g. ehtylyene, ethane, or acetylene) will be assessed through additional sets of sealed soil incubations at 10% (w/w) gravimetric moisture (slurry) with and without biochar amendments.   Data on water quality of leachates, water retention capacity, and GHG emission from the soils pots will be presented at the meeting.