Coal is up to 100 times more polluting than fracking, new study claims
A new study has found that electricity generated from coal could release between 10 and 100 times more toxic chemicals into the air, soil and water than that generated from natural gas extracted with fracking.
A team at the University of Michigan conducted the research and concluded that extracting coal was far more damaging to human health despite the negativity that frequently surrounds fracking in the media.
The findings suggest that as the US energy market continues to shift from coal to natural gas, the overall “toxicity burden” of the electricity sector will decrease, said study author Shelie Miller.
“This analysis does not imply that concerns associated with shale gas production are unfounded, only that the overall toxic load of coal is definitely greater,” she said.
“And while the study doesn’t address this directly, we should be pursuing renewables more aggressively if we really want to decrease the human toxicity burden of our energy system.”
The comparative study, called a lifecycle impact assessment, used Pennsylvania as the point of origin for both shale gas and coal, since both energy sources are abundant in the state.
For the coal system, the study estimates the toxicity associated with air pollutants emitted during power generation, as well as toxic chemical releases during the coal-mining process from acid-mine drainage and coal-ash impoundment.
The air pollutants analysed for the coal system included particulate matter (soot), mercury, volatile organic compounds, nitrogen oxides and sulphur oxides.
For the hydraulic fracturing system, the study estimated the toxicity of the fracturing fluid chemicals used to crack rock and release natural gas, as well as the wastewater associated with shale-gas extraction. The researchers also looked at air pollutants emitted during both shale-gas extraction and electricity generation.
In both systems, particulate matter released into the air from power plants during electricity generation was the dominant toxicity contributor and outweighed chemical releases that may occur during extraction.
The harmful air emissions from coal-fired power plants were found to be much worse than those from cleaner-burning natural gas plants, Miller said.
“We looked at the total mass of emissions released per unit of electricity generated throughout the lifetime of both systems, and the overall toxic load is much greater for coal,” she said. “Emissions of particulate matter pumped into the air every single day by coal-fired power plants have greater potential human health impacts than any of the other chemicals we examined.”
The study by Miller and her colleagues is believed to be the first head-to-head comparison of coal and shale gas from the resource extraction phase through electricity generation.
While the results provide a comparison of relative toxicity between the two systems, large uncertainties and lack of data precluded a full-blown risk assessment.
Much of the uncertainty relates to the hydraulic fracturing process. The chemicals used in hydraulic fracturing fluid are considered proprietary, and the magnitude and frequency of water-contamination events are not well-documented.
When faced with uncertainties about the chemicals used in the hydraulic fracturing process, the researchers deliberately overestimated the amount of toxic chemicals that would reach the environment to ensure they weren’t minimizing fracking’s health impacts, Miller said.
Even in a seemingly implausible accidental-release scenario in which all of a well’s hydraulic fracturing fluid and untreated wastewater were discharged directly into surface waters for the lifetime of the well, shale-gas electricity had a lower lifetime human toxicity impact, or HTI, than coal electricity, according to the study.
To calculate the health impacts of particulate matter from power plants, the researchers collected emissions data from 23 natural gas and 13 coal-fired power plants in Pennsylvania. Data from 2,900 hydraulically fractured wells in the state were used to estimate potential releases of fracturing fluid chemicals and wastewater.
The first test fracking procedure in the UK is taking place this month after operator Third Energy overcame local opposition to the plans.
Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.