The study shows that Gorlov HEE is less impactful across almost all environmental indicators than small hydropower. Nonetheless, the study should be viewed as a rough basis for estimating the life-cycle environmental impact of HEE. The data used for this study came primarily from estimates, as opposed to from a case study. Additionally, many considerations were not taken into account: fish and local river ecology health was not taken into account, though Miller et al. suggest that a new LCIA category could be created and this impact could be calculated using estimated fish passage from HEE computational fluid dynamics and fish swimming data. The authors did not consider in their assessment the variety of fiberglass types used for turbine blade construction. Furthermore, the study did not account for negative environmental effects of dam construction, such as changes to overall water flow and temperature differences, or the benefits of hydropower, such as its reliability as a renewable source of energy and the benefit of creating a reservoir.
Miller et al. (2011) used life-cycle assessment methods to evaluate environmental impacts of hydrokinetic energy extraction (HEE), which have not previously been quantified. The authors established a baseline methodology for doing so, and compared their LCA findings for HEE with other energy systems across a variety of environmental indicators. HEE is considered an environmentally benign form of renewable energy, and by harnessing kinetic as opposed to potential energy, avoids the sediment movement and impact to ecosystem of conventional hydroelectric power generation. HEE collects energy from the kinetic movement of water without constructing a dam, and therefore avoids large ecosystem disruptions and changes to water flow and volume associated with hydropower electricity generation. In this study, the authors focus on HEE from rivers, as opposed to tidal flow or waves. They focus on the Gorlov system, which uses a helical crossflow turbine. Miller et al. found the Gorlov system compared closely to small hydropower and to have the lowest life-cycle impact of all energy systems considered.—Lucy Block
Miller, V., Landis, A., and Schaefer., 2011. A benchmark for life cycle air emissions and life cycle impact assessment of hydrokinetic energy extraction using life cycle assessment. Renewable Energy 36, 1040-1046.
Veronica B. Miller, Amy E. Landis, and Laura A. Schaefer of the University of Pittsburgh employed the Tool for the Reduction and Assessment of Chemical and other environmental Impacts (TRACI) to conduct their Life-Cycle Impact Assessment (LCIA). They considered upstream and downstream impacts of HEE, small hydropower, coal, natural gas, and nuclear power. The small hydropower considerations included the dam structure, tunnel, turbine, generator, plant operation, and dismantling. The calculation of coal plant impact included the coal production and preparation, coal processing, storage and transportation, and the calculation of natural gas impact included gas field exploration, natural gas production, gas purification, long distance transportation, and regional distribution. The HEE LCIA included raw materials used to construct the Gorlov system, transportation, assembly, operation, and decommissioning.
Miller et al. compared different energy systems to each other across many environmental indicators to calculate which energy source implies the most environmental impact, and more specifically, how Gorlov HEE and hydropower compare to one another, but they do not mention how they controlled for the variable of energy output between different types of electricity plants. The authors found that among all energy systems considered, coal and gas power plants had the highest environmental impacts related to global warming, acidification, eutrophication, ecosystem disruption, and smog formation. Nuclear power was most the most impactful energy system in terms of ozone depletion. Gorlov HEE and small hydropower had negligible global warming impacts compared to the other energy systems. A comparison of Gorlov HEE and small hydropower showed that small hydropower was more impactful than Gorlov HEE across all indicators but respiratory effects and acidification. The authors attribute these impacts to the production of copper, which is used for the Gorlov HEE generator, though they mention that methods of SO2-free copper production are currently being investigated. The ecotoxicity of Gorlov HEE was shown to be less than 2% of that of small hydropower.
 The authors neglect to mention whether their data for the impacts of natural gas production have been updated to reflect recent developments in natural gas extraction from the use of horizontal hydraulic fracturing. Nonetheless, the impacts of this technology have not yet been thoroughly studied, so it is safe to assume they have not.