## 1 Introduction  
Mineral mining practices have contributed to potential toxic metal (PTM) pollution of soils worldwide [1]. Stamp milling was a common method used for extracting minerals from host rock. It is a process in which large mineral containing rock is crushed, or stamped, into smaller pieces for mineral extraction [2]. The fragmented rock, or mine waste product is called _stamp sand_ because of its sand-like properties. Stamp sand has elevated levels of many PTMs, low organic matter, low water content, and does not support most vegetative growth [3]. In the Upper Peninsula of Michigan, during the Cu mining boom period of late 19 th and early 20 th centuries, millions of tons of stamp sand were disposed of into Lake Superior and surrounding areas [4]. The sites that contain the mine waste are now considered marginal land, containing elevated levels of PTMs including Cu, Pb, Zn, As, Fe, Ni, Cd, Ag, Hg, Cr, Al, and Mo [5]. Due to the lack of vegetative cover, Cu contaminated stamp sands are eroding back into the lakes, thus affecting the aquatic ecosystem.  
A potential remedy to make use of marginal, metal-contaminated land includes the application of phytoremediation; the use of plants to accumulate or stabilize contaminants. Following harvest, the contaminated biomass is conventionally disposed of at landfill sites or incinerated [6]. Depending on the nature of the plant species used for phytoremediation, the biomass harvested after phytoremediation could potentially be used as a second- or third-generation biofuel feedstock for sustainable land management.  
Vetiver (_Chrysopogon zizianioides_ [PERSON]) grass is a lignocellulosic species that has been reported to be tolerant of various xenobiotics [7]. It has been classified as a hyperaccumulator of metals such as Pb and Zn [7,8]. It also accumulates many other PTMs [7]. Vetiver is non-invasive, has high biomass and an extensive root system [9,10]. Its biomass composition is low in lignin and rich in xylose, a highly fermentable pentose sugar [11,12,13]. Specifically, its lignocellulosic composition consists of 34.4% (m/m) cellulose, 39.4% (m/m) hemicellulose, and 7.9% (m/m) lignin [14,15]. The cellulose and hemicellulose composition make bioethanol production possible by yeast fermentation. The lignin content of vetiver is less than that of miscanthus and switchgrass, common second-generation bioethanol feedstocks [16,17]. We hypothesized that these characteristics would make vetiver a practical feedstock for bioethanol production.  
In the current study, vetiver grass was grown in a greenhouse in columns containing stamp sand collected from the Torch Lake area in Upper Peninsula, Michigan. Metal uptake and leaching from the columns was monitored for a period of 60 days. At the end of the experiment, biomass was harvested and used for bioethanol extraction. The objectives of the study were to (1) evaluate the potential of vetiver grass to grow in stamp sand containing elevated levels of Cu, (2) evaluate the effectiveness of vetiver roots to control stamp sand erosion, (3) investigate the effects of PTM exposure on the lignocellulosic composition of the grass for downstream fermentation, (4) optimize the fermentative processes for vetiver biomass, and (5) study the effects of Cu exposed biomass on bioethanol yield.