MULTITASKING MISCANTHUS GIGANTEUS: PHYTOREMEDIATION/PHYTOMINING OF MARGINAL, METAL-CONTAMINATED LAND COUPLED WITH BIOETHANOL PRODUCTION

Marginal land is classified as unusable due to the inability to sustain permanent agriculture without regular investment of land or water resources. The ineffectual use of this marginal land in Michigan’s Upper Peninsula is due to heavy metal contamination as a result of mineral mining. Phytoremediation is a process that utilizes living plants to remediate contaminated soil and sediment. Lignocellulosic plant species with extensive root systems have been characterized as heavy metal hyperaccumulators, functional for use in phytoremediation. Currently it is common practice to incinerate the contaminated biomass after successful phytoextraction to reduce the volume of contaminated matter. There are a few shortcomings of burning heavy metal-contaminated biomass, including volatilization, formation of metal oxides, and lack of conventional ash disposal. Another inadequacy of incineration following phytoremediation is the burning of valuable carbon present in the harvested plant biomass. In addition to the consideration and acceptance of some lignocellulosic species as metal hyperaccumulators, some lignocellulosic plant species have also been identified as viable feedstocks for renewable fuel. Carbohydrate polymers are abundant in lignocellulosic biomass, which can undergo chemical and enzymatic hydrolysis and microbial fermentation to produce bioethanol and provide feedstock for renewable energy. Miscanthus giganteus, a lignocellulosic grass is currently used as a feedstock for biofuel production. In this study, the capacity of Miscanthus to remediate heavy-metal contaminated sands was investigated. A 60-day uptake study was performed in a greenhouse setting, using native stamp sands. The plant-containing columns were maintained at an 80% water-holding capacity throughout. Plant growth parameters, chlorophyll content, lignin and carbohydrate composition, and metal concentrations (Cu, Al, Fe, Pb, and Ni) for soil, root, and shoot were analyzed at day zero and day-60. Leachate samples were collected at regular intervals throughout the 60-days and analyzed for metals to obtain the final mass balance. The efficiency of Miscanthus as a candidate for phytoremediation, and the effect of metal uptake on lignin and carbohydrate composition were evaluated.