Although it is well-established that hydraulic fracturing affects human health to a greater extent, an innovative research performed at University of Michigan has revealed that the lifetime emission of toxic chemicals during coal-generated electricity is 10-100 times more than the emission from electricity produced using natural gas acquired through fracking.
Illustration of a shale-gas electricity system (left), including hydraulic fracturing operations and electricity generation. At right, sketch of a coal electricity system, including coal mining and electricity generation. CREDIT: Lu Chen, Shelie A. Miller and Brian R. Ellis, “Comparative human toxicity impact of electricity produced from shale gas and coal,” in Environmental Science & Technology.
The research is a comparative investigation of the hazardous impacts of electricity produced from coal and shale gas on human health. The study analyzes the amount of toxic chemicals emitted into the soil, air and water at the resource extraction as well as electricity generation stages of both technologies and consummates that the prospective effects of electricity generated from coal on human health are considerably greater.
According to Shelie Miller, corresponding Author of the study who is an Environmental Engineer and an Associate Professor at the UM School for Environment and Sustainability’s Center for Sustainable Systems, the outcomes of the study indicate that because the energy market in the US has been continually changing over from coal to natural gas, the net “toxicity burden” of the electricity sector will be reduced.
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. 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.
Shelie Miller, corresponding Author of the study and Associate Professor,
Center for Sustainable Systems, School for Environment and Sustainability
The research was reported online in the Environmental Science & Technology journal on October 10
th, 2017. Brian Ellis from the UM Department of Civil and Environmental Engineering and Lu Chen, a recent graduate of the U-M School for Environment and Sustainability, were the other Authors of the study.
Recently, the integration of horizontal drilling with hydraulic fracturing, or fracking, has assisted in unearthing extensive reserves of natural gas in shale formations. Ever more generation of shale-gas led to prosperity in specific parts of the country. However, it has also culminated in worries related to prospective contamination of drinking water and probable effects of hydraulic fracturing on human health.
In relation to these worries and the continuing changeover to shale gas, Miller and her team considered that it is important to place the prospective effects of shale gas on human health, as against coal, into the right context. In the comparative analysis, known as a lifecycle impact assessment, the Scientists used Pennsylvania as the point of origin in the case of shale gas as well as coal. This is because both these energy sources are plentiful in the state.
In the case of coal, the research evaluates the toxicity related to air pollutants released in the course of power generation and also the emission of toxic chemicals due to acid-mine drainage and coal-ash impoundment during coal-mining. Nitrogen oxides, particulate matter (i.e. soot), volatile organic compounds, mercury and sulfur oxides were the air pollutants investigated for the coal system.
In the case of hydraulic fracturing, the toxicity of the fracturing fluid chemicals employed to crack rock and extract natural gas and also the wastewater produced during shale-gas extraction were evaluated. The team also analyzed air pollutants released as part of shale-gas extraction as well as electricity generation.
For both systems, particulate matter emitted from power plants into the air at the time of electricity generation was the most powerful toxicity contributor and exceeded chemical emissions that take place in the course of extraction. According to Miller, the release of hazardous chemicals into air from coal-fired power plants was considerably greater when compared to those emitted from cleaner-burning natural gas plants.
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. 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.
Miller, corresponding Author of the study and Associate Professor, Center for Sustainable Systems, School for Environment and Sustainability
The analyzes by Miller and her team are the first direct comparison of shale gas and coal from the resource extraction stage to the electricity generation stage. Although the outcomes offer a comparison of relative toxicity of the two systems, huge ambiguities and inadequacy of data hinder a comprehensive risk assessment.
A major part of the ambiguities is associated with the hydraulic fracturing procedure. The chemicals mixed in the hydraulic fracturing fluid are contemplated to be proprietary, and the frequency and magnitude of water-contamination incidents are not documented enough.
Miller stated that to deal with the ambiguities associated with the chemicals used in the hydraulic fracturing procedure, the team purposefully overestimated the quantity of toxic chemicals liberated into the environment to ascertain that health impacts of fracking were not underestimated.
It was seen that even in an apparently improbable inadvertent-release condition in which the entire hydraulic fracturing fluid and untreated wastewater from a well were directly released into surface waters for the well’s lifetime, the lifetime human toxicity impact (HTI) of shale-gas electricity was lower when compared to coal electricity.
In order to evaluate the effects of particulate matter from power plants on health, the team gathered emissions data from 13 coal-fired and 23 natural gas power plants in Pennsylvania. Data acquired from 2900 hydraulically fractured wells in Pennsylvania were adopted to evaluate potential emissions of fracturing fluid chemicals and wastewater.
Two distinctive assessment techniques were adopted to evaluate the health impacts. A range of statistical investigations were performed to corroborate the outcomes, indicating 90% confidence in the comprehensive outcome that the HTI of shale gas is considerably lower than that of coal.
The University of Michigan Water Center, U-M’s M-Cubed program, and a grant from the National Science Foundation supported the study.