able ▁energy ▁source . The ▁process ▁of ▁obtain ing ▁this ▁energy ▁is ▁emission ▁free - ▁there ▁is ▁absolutely ▁zero ▁carbon ▁used ▁when ▁it ▁comes ▁to ▁the ▁production ▁of ▁this ▁type ▁of ▁power . ▁The ▁procedure ▁can ▁clean ▁out ▁sul fur ▁that ▁may ▁have ▁generally ▁been ▁dis charg ed ▁from ▁other ▁processes . ▁Ge oth erm al ▁energy ▁has ▁the ▁smallest ▁land ▁foot print ▁of ▁any ▁major ▁energy ▁source ▁in ▁the ▁world . ▁ ▁Water ▁is ▁also ▁used ▁in ▁obtain ing ▁this ▁type ▁of ▁energy . ▁Depending ▁on ▁the ▁cool ing ▁technology ▁used , ▁ge oth erm al ▁plants ▁can ▁require ▁between ▁ 1 , 7 0 0 ▁and ▁ 4 , 0 0 0 ▁gall ons ▁of ▁water ▁per ▁meg aw att - hour ▁of ▁energy ▁produced . ▁However , ▁most ▁ge oth erm al ▁plants ▁can ▁use ▁either ▁ge oth erm al ▁fluid ▁or ▁fresh water ▁for ▁cool ing , ▁and ▁using ▁the ▁prior ▁has ▁a ▁significantly ▁less er ▁environmental ▁impact . ▁There ▁are ▁both ▁open - loop ed ▁and ▁close - loop ed ▁ge oth erm al ▁systems , ▁and ▁open - loop ▁systems ▁emit ▁small ▁amounts ▁of ▁hydro gen ▁sul f ide , ▁carbon ▁dio x ide , ▁am mon ia , ▁m eth ane , ▁and ▁bor on . ▁ ▁H ydro elect ric ▁energy ▁▁ ▁H ydro elect ric ▁power ▁includes ▁both ▁massive ▁hydro elect ric ▁d ams ▁and ▁small ▁run - of - the - river ▁plants . ▁H ydro elect ric ▁plants ▁emit ▁fewer ▁green house