More Guest Blogs
By EDGAR HERTWICH, ANDERS ARVESEN, SANGWON SUH, and THOMAS GIBON
There are a number of available low-carbon technologies to generate electricity. But are they really better than fossil fuels and nuclear power?
To answer that question, one needs to compare not just the emissions of different power sources but also the health benefits and the threats to ecosystems of green energy.
Production of electricity is responsible for about a quarter of global greenhouse gas emissions, and demand is poised to rise as underserved populations connect to the grid and electronics and electric vehicles proliferate. So stopping global warming will require a transformation of electricity production.
But it is important to avoid various environmental pitfalls in this transition, such as disrupting ecosystems and wildlife or causing air pollution.
In a research paper, we analyzed the impact of electricity generation from renewable sources, nuclear fission power plants, and fossil fuels, with and without COâ‚‚ capture and storage (CCS) technology for separating COâ‚‚ and storing it underground. We accounted for the environmental effects associated with the production, operation, and dismantling of facilities, as well as the production, transport, and combustion of fuels. We then compared a baseline scenario to a low-carbon electricity scenario that would prevent global average temperatures from rising more than 2°C above preindustrial levels by 2050 – the point climate scientists say will avoid dangerous climate change.
Our study emphatically confirms that fossil fuels – mainly coal – place a heavy burden on the environment and that most renewable power projects have lower pollution-related impacts on ecosystems and human health. Nonetheless, no energy source is without adverse environmental side effects. Power plant siting, project design, and technology choice are critical issues that investors and governments should consider very carefully.
Solar shines
Replacing fossil fuel power plants with renewable energy sources, including solar, wind, hydropower, and geothermal power, would reduce diverse types of pollution. The magnitude of difference in pollution between fossil and some renewable energy options is stunning. For example, we found that the entire process of manufacturing, setting up, and operating photovoltaic panels causes less pollution than only delivering fuel to a coal-fired power plant when mining is included.
What about the environmental footprint of actually making renewable energy systems?
Photovoltaics (PV) comes out very well in our analysis. Today, the production of PV cells uses much less energy than previously. The carbon emissions per unit of PV electricity is one-tenth or less of even the most efficient natural gas power plants. Human health problems, such as respiratory disease from particulate matter exposure, are around one-tenth of those of modern coal-fired power plants with advanced pollution control equipment. Similar conclusions hold for water and soil pollution on ecosystems, we found.
But solar panels require much more space to generate the same amount of power as fossil fuel or nuclear power generators. Shouldn’t covering huge areas with solar panels be a problem? Not necessarily. The amount of land needed to generate a kilowatt-hour from PV is comparable to that of coal power, when the land associated with mining coal is accounted for. And about half of the PV installations in our future scenario in 2050 could be placed on rooftops.
Producing PV panels does require various metals, many of which are produced only in limited locations. Some of those metals are highly toxic. Waste treatment and recycling, which we did not include in our assessment, are therefore important.
PV, of course, delivers electricity only when the sun shines. However, a different solar technology — concentrating solar-thermal (CSP) power, which concentrates light to make heat — may be a viable way forward as it delivers a similar performance in terms of pollution reduction yet offers the option to store heat and thus generate electricity in the evening. We assumed CSP technology, which currently has very low adoption compared to PV, would provide one quarter of solar electricity in our low-emissions scenario.
Impact of hydropower varies
Environmental effects from hydropower vary widely, we found. Some dams cause significant climate impacts through the emissions of methane from the decomposition of biomass in reservoirs. Other dams cause equally serious ecological problems through habitat destruction. They can also block the migration of aquatic species and reduce sediment flow and nutrient transport, which affects floodplains and deltas. On the other hand, reservoirs form new habitats for birds and other species.
Hydropower offers a good illustration of the importance of site selection and project design. Some projects may be economically viable but ultimately should not be realized if society considers the environmental degradation they can cause. For other projects, the impacts can be limited by mitigation strategies such as environmental stream flow and fish ladders, which provide a detour for migrating fish around a dam.
Similar lessons hold for wind power, where habitat destruction during construction should be minimized and operations adjusted in order to reduce collisions with raptors and bats. Also, wind power resources vary widely across locations, which argues for choosing locations where wind resources are more abundant.
Bioenergy threatens biodiversity
Biomass energy, or burning plant material for power generation, plays a central role in most plans to limit global warming to 2°C above preindustrial levels. Unlike PV and wind, it provides on-demand renewable power.
When combined with COâ‚‚ capture and storage, it can scrub carbon from the atmosphere and place it underground. Burning short-rotation coppice, such as willow and miscanthus, to produce power can also lower the net greenhouse gas emissions of biopower. In these ways, the health effects of burning biomass can be reduced.
Yet the land use required to grow even these fast-growing plants dwarfs the land use of other power sources. This has significant ecological implications. As measured by species lost per kilowatt-hour generated, we found that the ecological damages of biomass are comparable to that of coal and gas.
So while it does deliver benefits from reduced greenhouse gas emissions, biomass power becomes more favorable to ecosystems only when used with carbon capture and storage, we concluded.
Climate mitigation strategies can provide a rare opportunity to reduce not only carbon emissions but also a wide range of environmental problems. However, deployment of low-carbon technologies should avoid sensitive habitats in order to fully realize their environmental benefits without triggering unintended consequences.
While most people recognize that solar and wind are low-carbon energy sources, bioenergy and carbon capture and storage also have an indispensable role in basically all scenarios where countries rapidly reduce carbon emissions. Our results indicate that we need to search for ways to use these technologies while minimizing the harm to ecosystems. It is not just about whether we employ clean energy, but what technologies, where and how.
Edgar Hertwich is a professor of ecology at Yale University. Anders Arvesen is a researcher in energy and process engineering at Norwegian University of Science and Technology. Sangwon Suh is a professor in industrial ecology at the University of California, Santa Barbara. Thomas Gibon is a Ph.D. candidate at the Norwegian University of Science and Technology. This post originally appeared at The Conversation.
Weekly Newsletter
Get building science and energy efficiency advice, plus special offers, in your inbox.
8 Comments
Why oh why was disposal/recycling not considered???
"Producing PV panels does require various metals, many of which are produced only in limited locations. Some of those metals are highly toxic. Waste treatment and recycling, which we did not include in our assessment, are therefore important."
Disposal/recycling can potentially can potentially become a large problem just as it already is with high capacity batteries (Hello Tesla).
Detractors of solar will view this as the "dirty secret" under the premise that it wasn't considered because it would make Solar look less favorable or maybe even on par with other forms of energy generation. At that point Solar turns into another big gov't subsidy financed on the backs of the taxpayer.
Dirty secret?
The article makes the unremarkable point that there is no energy source that is without some negative aspects. But a solar panel that sits on a roof for thirty years and then gets dumped in a landfill(which is highly unlikely) will have a lower environmental impact than an abandoned coal mine or fracked gas well. Of course nuclear energy's long term impact is orders of magnitude worse.
Considering all environmental impacts is very difficult
Remember, some of the probable environmental impacts of a continued dependence on fossil fuels include the flooding of most of the world's coastal cities, mass extinctions of species on a scale that can only be compared to extinctions seen in the fossil record, huge waves (in the millions) of climate migrants, and the possible end to human civilization.
Care to put a price on those "externalities"?
-- Martin Holladay
I disagree with biomass and
I disagree with biomass and carbon capture being necessities, and notice how they completely ignored pumped hydro, batteries and other energy storage methods.
Also they should account for solar metal impacts, naysayers will seize on this because their ideology demands they oppose progress. Also do all solar panels have the same unaccounted for impacts or does it vary by technology?
Modern nuclear tech must be considered
Nice analysis, but completely ignoring advances in nuclear technology leaves out a probable key portion of the solution. Nuclear waste can be used to fuel modern, fail safe, nuclear plants that create CO2 free electricity while reducing environmental liability of accumulated nuclear waste. We just need to be able to see past old, well earned, negative stereotypes from older nuclear power plants.
Quote from Sir David King, former (UK) Government Chief Scientific Adviser:
“[Fourth-generation reactors and nuclear-waste recycling] …makes geological disposal much less of a challenge (and arguably even unnecessary) and nuclear waste a minor environmental issue compared to hazardous wastes produced by other industries.”
The top 10 emerging technologies for 2013, World Economic Forum blog, February 14, 2013
Consider, but don't count on it (@ Mitchell Costa)
There are no credible 4th generation nukes that can use spent fuel rods for fuel. Designs that made that claim (notably Transatomic's MSR) have not held up under peer review scrutiny. Best-case is that it could process the spent fuel rod with some net gain, but only if using some other primary fuel to keep the reactions going.
The more significant problem is the dearth of real proof-of-concept designs already built and operating. Getting it even from one full-scale proto to a fully commercial product built in any volume will take more than a decade, and it'll be at least another decade to develop a robust track record, including the real cost numbers. It's a promising technology, but promises in that industry have a history of being broken. The world has to forge on without it, for now, but governments can/are/should finance the development of at least the prototypes, if not the commercialization.
In the mean time smarter grids of PV & wind firmed by storage are already cost-competitive with incumbent generation technologies at the utility scale, and small & medium scale will be too in less than a decade, and that's a good thing, since distributed resources takes the load off the grid, freeing up capacity. The Australian grid operator is anticipating that by 2035 70% of all electricity customers in that country will have behind-the-meter generation (typically)PV, and 50% of all customers will have behind the meter storage.
https://www.greentechmedia.com/articles/read/battery-storage-is-booming-in-australia-says-network-operator
Will there even be a full scale prototype of a 4th generation nuke by then?
Place your bets, folks!
Last year NREL published a Technical Potential assessment that demonstrated ~50% of all power use in the US coujld be sources from existing rooftops (no new real-estate required). While it's clear that less than half of that would ever get built, depending on how badly policy makers in the US screw it up the US may follow the Australian model (that includes some cutting the cord, which isn't a great outcome for those who don't or can't.)
http://www.nrel.gov/docs/fy16osti/65298.pdf
The financial reality at that time of full commercialization of a 4th generation nuke (when, 2040? 2050?) will dictate that nuke plus the grid to deliver it will have to be cheaper than PV/wind + batteries, which is going to be pretty tough hurdle to clear, even if the prototypes were already up and running right now. The cheap renewables & cheap storage train has already left the station, and is picking up speed on it's own financial merits independent of strong policy support.
Author Ignores that Solar and Wind are not Grid Compatible
The author blithely ignores the fact that solar and wind are intermittent and highly variable sources of power and that nuclear is a baseload (24/7/365) power source compatible with the grid and compatible with the way we use electricity; i.e. we expect it to be available whenever we want to use it. When variable and intermittent power sources are added to the grid, the utility typically uses gas turbines to buffer power delivery because they respond to grid demands quickly. This balancing act uses more natural gas than it would if there were no intermittent sources of power. The more solar and wind added to the grid, the greater the problem in balancing the power.
Response to Jay S
Jay,
The authors (not author) do not "blithely ignore the fact that solar and wind are intermittent and highly variable sources of power," as you assert.
In fact, their "mitigation scenario" (the one including renewables -- compared to the so-called "IEA baseline scenario") has this mix of energy sources: "a diversified portfolio of hydro, wind, solar and nuclear power accounts for 4.3 TW, gas supplies 3 TW, of this 0.3 TW with CCS [carbon capture and storage], coal 0.7 TW mostly with CCS, and biomass and waste contribute 0.4 TW."
You may have reasons to quibble with this scenario, but the scenario includes a substantial natural gas component as well as a nuclear component.
For an example of a grid that is approaching 50% PV, see this article: A Caribbean Island Transitions to PV.
-- Martin Holladay
Log in or create an account to post a comment.
Sign up Log in