Small Drones Could Be Better for Climate Than Delivery Trucks, Says Study
By Zeke Hausfather
Automated, unmanned drones are poised to revolutionize the package delivery industry, with a number of companies already testing drone-based delivery methods.
A new study in Nature Communications looks at the climate impact of a shift from truck-based to drone-based package delivery. It finds that while small drones carrying packages weighing less than 0.5 kg would reduce greenhouse gas emissions compared to diesel or electric trucks anywhere in the U.S., the same is not true for larger drones carrying heavier packages.
Game of Drones
The cost of drones has fallen dramatically over the past decade. At the same time, improvements in battery energy storage and a reduction in battery costs have led to drones that can fly much larger distances. Advances in automation and computer vision has made it possible to conceive of drones that could deliver packages to individual homes without requiring a human operator.
The combination of these factors has led companies—including Amazon, Google, UPS, DHL and others—to start developing programs for drone-based delivery of packages. Due to their fast delivery speed, drones are a natural fit for same-day delivery of orders, something that a number of different companies have been pursuing in recent years.
While the commercial use of drones is strictly regulated today, both the U.S. Federal Aviation Administration and the European Aviation Safety Agency are developing regulations to allow the use of drones for delivery purposes.
Current in-city delivery of packages is primarily via diesel trucks in both the U.S. and Europe. Some companies are piloting electric delivery trucks. While their deployment to date has been fairly small, they are expected to take a larger market share in the future.
In most prototype programs developed by companies so far, the drones used for delivery have been relatively small battery-powered quadcopters or octocopters. These drones can only fly for around 10-15 minutes before their batteries are exhausted, limiting the range in which they can deliver packages.
The new study looks at the climate impacts of two specific types of drones: small quadcopters capable of transporting 0.5kg and large octocopters that can carry up to 8.1kg. Both types of drones are capable of carrying a single package up to 4km and returning to refuel before their battery runs out.
More Drones, More Warehouses
The limited range of drones compared to traditional diesel delivery trucks would require companies to build many drone-enabled warehouses in locations close to customers. The authors of the new study suggest that this would increase direct energy use by these additional warehouses, as well as require additional deliveries to these distributed warehouses.
The authors give an example of how warehouses for drone delivery in the San Francisco Bay Area might work, as shown in the figure below. As drones only have a range of around 4km, a warehouse would be needed every few kilometers to cover an entire region. They suggest that most of San Francisco itself could be supplied from only four warehouses given its density (left map), but that 112 warehouses would be needed to supply the entire San Francisco Bay Area (right map).
Example of optimal warehouse locations to supply most of the city of San Francisco (left map) and greater San Francisco Bay Area (right map) assuming a small quadcopter with a range of 3.5km. Taken from Figure 3 of Stolaroff et al 2018.
Small Drones Can Reduce Emissions
All types of delivery drones are much more efficient per mile travelled than diesel trucks. However, delivery trucks generally do not carry only one parcel. Thus, the energy used per package is considerably smaller. The researchers point out that "delivery trucks carry many packages, delivering on average 0.94 packages per km (1.51 per mile), and their impacts need to be allocated per package."
To account for this, the authors calculate the total greenhouse gas (GHG) emissions in grams of CO2-equivalent (CO2eq) per package from small drones, large drones, diesel trucks, natural gas trucks, electric trucks and petrol vans. They further examine how these findings vary across the different electricity generation mixes found in the U.S. You can see their main results in the figure below.
Greenhouse gas emissions (in grams CO2eq) per package for different delivery methods. Adapted from Figure 5 of Stolaroff et al 2018.
The authors find that small drones that carry packages lighter than 0.5kg have the lowest overall GHG emissions of any delivery system they examined. This is true both in places such as California (where electricity is relatively low-carbon), for the U.S. average grid mix and for areas of the U.S. with the most carbon-intensive electricity.
Small drones result in a 50 percent reduction in GHG emissions per package delivered compared to diesel trucks in California and 37 percent less carbon than diesel trucks on average across the whole U.S. In Missouri, which has among the most carbon-intensive electricity in the country, small drones still result in a 23 percent reduction in emissions.
If it is assumed that the alternative to drone delivery is electric delivery trucks rather than diesel trucks, small drones reduce GHG emissions by 26 percent in California and 33 percent for the whole U.S. Interestingly, for the current U.S. electricity grid mix, electric trucks result in about the same emissions as diesel trucks.
The picture is quite different for large drones, which carry packages up to 8.1kg. While they still reduce emissions in "low-carbon" California, they only result in a 9 percent reduction compared to diesel trucks. In the U.S. as a whole, their emissions are actually 24 percent. This will change in the future as the U.S. grid mix becomes cleaner.
In general, drones have a large potential for reduced transport emissions, while potential carbon reductions for diesel vehicles are more limited.
Breaking Down the Sources
The paper further breaks down emissions from each delivery option based on the portion that comes from transporting the packages, energy used for storing packages in warehouses, and the producing batteries used in drones and electric trucks.
The figure below shows the breakdown for various delivery options for the average U.S. grid mix.
Greenhouse gas emissions (in grams CO2eq) per package by source for a subset of different delivery methods. Adapted from Figure 5 of Stolaroff et al 2018.
Small drones have a remarkably low transportation-related electricity use, with almost all their emissions coming from the additional warehouses that need to be built. By contrast, large drones require much more electricity. Their emissions per package delivered is higher, with their combined transport electricity and battery production emissions roughly equal to the diesel fuel emissions from conventional diesel delivery trucks for the U.S. average grid mix. Electric trucks also show similarly high transportation-related emissions.
While reducing the carbon intensity of electricity generation would reduce both large drone and electric truck emissions compared to diesel trucks, the authors say there is little reason to prefer large drones over electric trucks for package delivery due to the extra warehouse-related emissions that large drones require.
Overall, the researchers find "significant promise in the use of drones to reduce energy use and greenhouse gas emissions." However, they also warn that "there are plausible scenarios where drones lead to overall higher energy use and greenhouse gas emissions compared to ground vehicles."
As Dr. Costas Sampras, the director the Center for Engineering and Resilience for Climate Adaptation at Carnegie Mellon University and one of the authors of the paper, told Carbon Brief:
"Our research finds that small package delivery by drones likely has lower GHG emissions than diesel trucks, even when accounting for the potential additional warehouse space needed. For larger packages, we found that it's probably better to use electric vans or electric trucks rather than large drones.
However, if warehouses to support urban drone delivery are constructed, they are likely to be used by both small and large drones—presenting a challenge for reducing GHGs from package delivery.
To maximise the climate benefits, firms should focus on smaller drones and an electrified ground fleet, while policy makers should focus on continued decarbonisation of electricity, as well as improved energy efficiency in buildings."
Reposted with permission from our media associate Carbon Brief.
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By Karen Charman
When President Donald Trump visited California on September 14 and dismissed the state Secretary of Natural Resources Wade Crowfoot's plea to recognize the role of climate change in the midst of the Golden State's worst and most dangerous recorded fire season to date, he gaslighted the tens of millions of West Coast residents suffering through the ordeal.
Foxes Guarding the Henhouse<p>Before he assumed power, Trump attacked regulations as unnecessary barriers to freedom and economic prosperity. Since taking office, he has targeted anything enacted by the administration of his predecessor, Barack Obama, and taken steps to withdraw the U.S. from the Paris agreement, the international effort to combat climate change. He has also staffed heads of key agencies with climate deniers of various stripes, forced out career public servants and created a hostile work environment for those who don't profess loyalty to his deregulatory agenda.</p><p>Like Trump himself, some of his cabinet choices displayed an audacious penchant for <a href="https://www.nytimes.com/interactive/2020/09/27/us/donald-trump-taxes.html?action=click&module=Spotlight&pgtype=Homepage" target="_blank">self-dealing</a> and abusing their positions of authority. 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Like Pruitt, Trump's first Interior Secretary Ryan Zinke aggressively attacked environmental regulations, <a href="https://www.washingtonpost.com/news/energy-environment/wp/2017/05/07/epa-dismisses-half-of-its-scientific-advisers-on-key-board-citing-clean-break-with-obama-administration/" target="_blank">ditched more than 200 advisory panels</a>, and pushed to open up vast swaths of public land to oil and gas drilling. Described by one environmental group as "<a href="https://www.washingtonpost.com/national/health-science/interior-secretary-zinke-resigns-amid-investigations/2018/12/15/481f9104-0077-11e9-ad40-cdfd0e0dd65a_story.html" target="_blank" rel="noopener noreferrer">the most anti-conservation Interior secretary in our nation's history</a>," Zinke was forced out after numerous highly publicized conflict-of-interest scandals.</p><p>The DOI is now run by Zinke's deputy secretary, David Bernhardt, another longtime Republican Washington insider and former oil industry lobbyist who has also been the subject of <a href="https://slate.com/news-and-politics/2020/05/this-is-still-happening-david-bernhardt-trump-lincoln.html" target="_blank">several government ethics complaints</a> for various violations favoring polluting industries.</p><p>More recently, longtime climate change denier David Legates, a climatologist at the University of Delaware previously <a href="https://insideclimatenews.org/news/19032015/u-delaware-refuses-disclose-funding-sources-its-climate-contrarian" target="_blank">funded by fossil fuel interests</a>, was hired for a <a href="https://www.npr.org/2020/09/12/912301325/longtime-climate-science-denier-hired-at-noaa" target="_blank" rel="noopener noreferrer">top job</a> advancing weather modeling and prediction at the National Oceanic and Atmospheric Administration (NOAA). 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The Damage So Far<p>A September 17 <a href="https://rhg.com/research/the-rollback-of-us-climate-policy/" target="_blank">report</a> by the Rhodium Group calculates that 1.8 billion tons more greenhouse gases will be released over the next 15 years as a result of climate change rollbacks the Trump administration has achieved so far. These include repealing Obama's main climate policy, the Clean Power Plan, which was intended to reduce dirty emissions from power plants; increasing pollution from cars by rolling back fuel economy standards and challenging California's longtime authority to set stricter emissions standards; targeting controls on hydrofluorocarbons, powerful greenhouse gases used mainly in refrigerators and air conditioners that also destroy the Earth's protective ozone layer; and allowing unreported and unregulated emissions of methane, another potent greenhouse gas, by oil and gas companies.</p><p>Besides these measures, Trump is also trying to gut core environmental statutes like the Clean Air Act, the Clean Water Act, the National Environmental Policy Act and the Endangered Species Act, all of which were enacted to protect human health and preserve a livable world.</p><p>The Paris agreement aims to keep the rise in average global temperatures at less than 2 degrees Celsius above pre-industrial levels and hopefully cap it at 1.5 degrees C or lower. We are now at approximately 1.2 degrees C and counting.</p>
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It wasn't so long ago that the issue of climate change was poised to play a huge – possibly even a decisive – role in the 2020 election, especially in the race for control of the U.S. Senate. Many people supporting Democratic candidates saw a possible Democratic majority as a hedge against a potential Trump re-election … a way to plug the firehose spray of more than 100 environmental regulation rollbacks and new anti-climate initiatives by the administration over its first term.
Potential Climate Voters<p>In a September 1 memo on climate and the election, Andrew Baumann, vice president of the consultants Global Strategy Group, wrote: "Few issues have seen as dramatic a shift in public opinion as climate change has over the last few years. Only marriage equality and the recent shift in views around racial justice outpace the rapid growth in the salience of climate change as an issue."</p><p>Calling it a "winning political issue" the memo says: "First, it is clearly a motivator for both younger and Latinx voters. Second, it has the power to move swing voters, particularly center-right white women."</p><p>Baumann points to a finding that when a group of such women were asked generic ballot questions, Democrats trailed by nine percentage points. But when the question was revised as a choice between:</p><p>"A Democrat who supports taking strong government action to combat climate change.<br>A Republican who opposes taking strong government action to combat climate change."</p><p>… the result was a 29 percentage point shift, putting Democrats ahead by 20 percentage points among that same group.</p><p>"I think it is playing a role," says Senator Sheldon Whitehouse, D-RI, a longtime outspoken climate activist who is on the Senate Environment and Public Works Committee and also on the Senate Democrats' Special Committee on the Climate Crisis. If Democrats win back the Senate, he stands to play an even more pivotal climate role as part of the majority. He is not up for re-election this year.</p><p><span></span>"I think from the Democratic side it's playing a role in generating enthusiasm – particularly making younger voters feel that they have a real stake in this election. On the Republican side, I think things have moved enough that candidates can no longer get away with simply scoffing about climate change."</p>
Climate a Top Concern for Youths, Latinx<p>So who's still thinking climate? Mostly young voters – 18 to 25 or 29 and Latinx voters.</p><p>Climate and the environment are the top concern among young voters, just above racism and healthcare according to <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank" rel="noopener noreferrer">CIRCLE</a>, the Center for Information and Research on Civic Learning and Engagement at Tufts University, which focuses on the political life of young people in the U.S. For Latinx youth, it drops a bit but remains in the top three.</p><p>The issues young people care about have an impact on how they volunteer their time, says Kristian Lundberg, an associate researcher at CIRCLE. He says that's played out most notably through the Sunrise Movement, which focuses on climate change and the environment along with other key activist groups such as Black Lives Matter and March for Our Lives.</p><p>He points to polling this summer that showed that 83% of 18-to-29-year-olds felt they had the power to change things. "Young people feel much more empowerment than in 2016 and 2018," Lundberg says. "It's intentional these movements are carving out space for young people. It's an important strategy."</p><p>In positions of power in these organizations, young people have developed peer-to-peer outreach on activism. And Lundberg says young people have made the leap that connects activism to voting as a lever for change. "In the past in very close races, young people breaking heavily have provided the margin of victory," he says.</p><p>CIRCLE is highlighting 10 U.S. Senate races as ones in which young voters can be decisive. Several of them have notable climate or environmental components – most prominently the Colorado and Montana races.</p><p>The Republican incumbents in each state – Cory Gardner in Colorado and Steve Daines in Montana – are running against a popular Democratic governor – John Hickenlooper in Colorado, now out of office — and Steve Bullock, still the governor of Montana. Both governors have had to balance their state's fossil fuel economic interests with supporting climate change solutions.</p>
Tying Climate Change to the Economy<p>In August, Data for Progress, a progressive research think tank, released polling on climate change – including in the battleground Senate elections in Arizona, Iowa, Maine, and North Carolina – showing voters back a Senate candidate supporting strong climate action.</p><blockquote>Climate change as 'mobilizing issue … key persuasion issue.'<br></blockquote><p>It also showed that linking climate change to the economy may be key. That means talking about clean energy and jobs together, says Danielle Deiseroth, climate data analyst for <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank">Data for Progress</a>. She says that in addition to jobs, climate change issues include climate justice and economic equality – both of heightened interest because of fallout from western wildfires.</p><p>"Climate change, we've observed over the last year or so, is a key mobilizing issue and a key persuasion issue," she says. "Climate issues can only grow support for Democratic candidates.</p><p>"I think it's pretty naive to say climate is the key issue for voters. For a lot of voters it really exemplifies so many things that are wrong with the Trump presidency," Deiseroth says.</p><p>So a factor among others. Helpful, but pivotal only in narrow circumstances.</p><p>At the League of Conservations Voters, a progressive environmentalist organization putting a lot of money and effort into the 2020 races, Senior Director of Political Affairs Craig Auster says: "I'll push back that climate change doesn't matter or isn't registering."</p><p>"It's still showing up in several Senate races. It's been playing a role in almost all of them."</p><p>Candidates are still talking about it, he says, pointing to Colorado, Montana, Iowa, and other states where ads are addressing climate and environmental issues. That shows the candidates believe their opponent is vulnerable on the issue or they're strong on it, he says.</p><p>Like others, Auster calls climate a motivator.</p><p>"Climate change matters," he says. "We have proof point after proof point about what's happening, whether it's a hurricane, a superstorm, derechos in Iowa, or wildfires out west.</p><p>"Pre-COVID it was top tier for Democratic voters along with healthcare. If COVID didn't happen I think climate would be a big deal."</p>
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