There are numerous environmental concerns with the production and use of shale oil. Virtually every step of the process of production of energy from oil shale is fraught with hazards.
From the very beginning of the oil shale process, the effort of getting it out of the ground, environmental issues arise. Oil shale is commonly mined through surface mining techniques.
Removal of the overburden to begin the mining process can disrupt delicate ecosystems. All plant life in the vicinity of the mine is virtually eradicated. Digging and crushing create dust and noise. Exposure of buried rocks allows oxidation processes to take place which results in acidic runoff.
Surface mines are commonly reclaimed and left in a situation that is little different from the original. However, once the rock is disturbed the volume is increased and cannot be completely disposed in the original mine.
Mining also disturbs the groundwater patterns in the area. Water tables may be lowered and runoff is redirected. This can have an impact on the ecosystems in the area. As many oil shale deposits are in desert areas, such as the Western US and Israel's Negev desert, water disturbances are of particular concern.
Extraction of fluids from oil shale has many environmental impacts. Extraction uses large amounts of water, from one to five times as much water as fluid produced. This water can be highly contaminated with organic and inorganic compounds and provides a serious ecological hazard.
Along with the dust from mining and crushing, burning of oil shale produces a wide variety of air pollutants. Similar to those produced by burning coal, these effects can be ameliorated through careful handling of flue gasses but must be taken into consideration. Fly ash, nitrogen oxides, sulfur oxides and hydrochloric acid are of particular concern.
Like all fossil fuels, the emission of greenhouse gasses is of concern in the use of shale oil. Since energy is required to extract usable oils from the rock, greenhouse gas production can be many times that from conventional fossil fuels such as natural gas, crude oil and coal.
Extracting usable liquids and gasses from the oil shale while in the ground, or in situ processing can reduce all of these concerns. Mining issues are almost completely eliminated using such methods while other environmental concerns are reduced by as much as 90%. However, there is still a concern with damage to aquifers as the resulting rock following such processing is more porous and can leach pollutants into groundwater.