How many benefits can one technology have? When it comes to agricultural drones, quite a few. Agribusinesses buy them because they save a lot of money and increase crop yield, as I pointed out in a companion piece on the subject. Companies like Hylio don’t bother to tout their green credentials because they sell themselves on more farm profits, as founder and CEO Arthur Erickson told me when I talked with him recently. The green benefits are a fringe benefit the rest of us will appreciate more and more.
So what problems does agriculture have that agricultural drones address?
Let’s start with the obvious ones. Imaging and sensor platform drones from companies like DJI, AgriExpo, and eBee AG fly over fields and grab high resolution images with and without crops. They enable agribusinesses to determine the state of the soil, the state of irrigation, and the status of crops throughout the year. The data pours into products like Pix4D, a SaaS platform that synthesizes the data into actionable farming insights.
These drones are overwhelmingly tiny, light, and electric. Most sensor drones are fixed wing simply because they can cover a lot more ground with a lot less energy. Think semi- or completely autonomous radio controlled airplanes with electric motors. They can fly for 45 or 50 minutes and take images with a resolution of a square inch or 2.5×2.5 centimeters. They can carry infrared and multispectral cameras that provide enormous amounts of data about the status of a field or crop. They can be launched by hand, thrown into the air before winging their way over a pre-mapped route.
So why is this a green benefit? Well, the first and most obvious benefit is that they are displacing piloted aircraft of various descriptions. Yes, lots of agribusinesses have been hiring airplanes with pilots and cameras for decades to fly over their fields. One source I saw suggested $1,000 for a single pass, while a good imaging drone costs that much and will fly all year long for years with minimal service and cheap electricity.
Pushing a tiny drone through the air takes a lot less energy than pushing a light aircraft through the air. A small Cessna 150 burns about 6 gallons of avgas per hour at 21.1 pounds of CO2 per gallon. One imaging flight might be 2-3 hours, so 250-380 pounds of CO2e. Multiply that by the perhaps 25% of the US that’s under cultivation. Then multiply it by a few passes a year.
And then throw all of that away because agribusiness are using electrically powered drones instead. Just as drones are eating the bottom out of the civilian helicopter market and allowing aerial photography to be accessible to everyone, so too are mostly fixed wing imaging drones eating the bottom out of the crop imaging market and making it accessible to vastly more farmers.
Then there are crop dusting drones like those offered by Hylio, DJI, and John Deere. A couple of the big ones cover as much ground as massive John Deere tractors weighing tons. A mid-sized John Deere 7R 270 diesel tractor consumes about 13.25 gallons an hour. That turns into about 300 pounds of CO2. Crop dusting drones don’t eliminate the need for tractors, but they can replace four to eight passes over every field during the year for applying herbicides, pesticides, fungicides, and fertilizer. A good sized tractor can manage about 100 acres per hour, and two big drones like Hylio’s AG-272 can do the same, but they run on electricity instead of diesel.
And the drones aren’t pushing tons of tractor across the ground with the product, they are lifting, in the case of the AG-272, 150 pounds of drone and 200 pounds of product. They have to fly back to the battery swap and product filling trailer regularly, but they are still using vastly less energy, and increasingly lower carbon energy to do so. Electric cars are much more efficient than internal combustion cars, but electric skateboards are orders of magnitude more efficient than either, and that’s the comparison to make between ag drones and tractors.
But crop dusting drones are also replacing fixed wing and helicopter crop dusting. Once again, drones, although not so tiny at 14′ in diameter and 350 pounds fully loaded, are displacing full-sized aircraft with pilots, along with all of their fuel requirements. More CO2 savings.
So a great deal less CO2 is coming from tractors and aircraft in agriculture as a result of drones, and their use has been increasing rapidly over the past decade. In 2017 and 2018, surveys found 63% and 75% of US farmers were using or planning to use drones, so the traditional aerial imagery and crop dusting concerns are finding contracts lighter on the ground and their revenues will likely plummet in the coming years. At least, unless they saw the writing on the wall and pivoted their services to drones, as I’m sure some did.
That’s just the tip of the iceberg. As I noted in the initial article, an upcoming study is likely to show 30% to 50% less product being sprayed on fields. Likely that comparison is to traditional crop dusting, as modern tractors have precision agriculture GPS and control systems that apply only the amount required in every area. Aircraft, however, dump a lot of product and a lot of it falls off the sides of the fields, ending up in waterways and on roads.
Let’s pick at two points here: ammonia-based fertilizers and phosphates.
Ammonia is an amazing chemical. It’s made up of one nitrogen atom and three hydrogens. When it’s applied to fields, it goes through a couple of transformations and leaves much of the nitrogen behind in the soil. That’s good because plants need nitrogen. Farmers used to rotate crops and plant clover in fields that were fallow to fix nitrogen from the air into the soil on off-years for the field. Now they can apply ammonia-based fertilizers and keep the fields in operation every year, with obvious productivity benefits.
That’s part of the Green Revolution that’s keeping us all fed, so we should be grateful for it. But it comes with a big downside, CO2e emissions. The hydrogen in fertilizers is still coming from natural gas (mostly) or coal. Every ton of hydrogen comes with 8-35 tons of CO2 emitted from the steam reformation and coal gasification processes which make it. And the natural gas and coal gas are mostly methane with its high global warming potential, and the world’s natural gas and coal gas systems leak a lot of it every year, adding another CO2e debt to the hydrogen and hence the fertilizer.
But that’s not all. As I noted, when ammonia-based fertilizers are applied, most of the nitrogen stays in the soil. But a bunch doesn’t. Instead it turns into nitrous oxide, N2O, with a global warming potential about 265 times that of CO2 per IPCC 6. When I spoke with Karsten Temme of Pivot Bio about this in late 2021, that resulted in every ton of ammonia-based fertilizer having a carbon debt of around ten tons of CO2e.
Global ammonia fertilizer demand was about 180 million tons in 2020, so that’s perhaps 1.8 billion tons of CO2e annually. And the world is only putting about 40 billion tons of excess CO2 into the air every year, so that’s around 4.5% of global warming emissions. Addressing greenhouse gas emissions from fertilizer use is a massive climate wedge, in other words.
And crop dusting drones can reduce it quite a bit. Typically 4-5 passes with fertilizer occur at different times of year. The big one is with tractors — once again increasingly precision, GPS-guided, carefully controlled tractors — after harvest. Hundreds of pounds per acre potentially. But the other 3-4 passes can apply dozens of pounds each, and more in needy spots.
Let’s play with some numbers as a scenario. Let’s take the average US farm of 445 acres. Let’s assume 3 passes with fertilizer after the big one. Let’s assume 50 pounds per acre per pass. That’s about 67,000 pounds of fertilizer or 33 tons. That turns into about 330 tons of CO2e just from the fertilizer from a single farm. Given the 1.2 billion or so acres in the US that are cropland, that’s a lot of CO2e from agriculture. The numbers globally that I remember are about 20% of land mass is for crops, so the scale is huge.
Now let’s cut that CO2e by 30% to 50% because we use drones instead. Big climate win.
But agriculture also has an excess phosphates problem. They run off the fields and into waterways, or overspray lands in water ways. And then they accumulate and cause algal blooms that kill fish, foul waterfowl spots and make stinking messes out of recreational areas. Excess nitrogen is complicit here as well.
Precision drone spraying that uses a lot less product and keeps it on the fields where it will be useful is clearly an environmental advantage.
There are more. A big one is soil compaction, which not only leads to crop productivity losses ranging from 9% to 55% per a 2019 study, but also means more water runs off the fields during irrigation and rain storms. And guess what happens when water runs off of fields? It takes useful herbicides, fungicides, pesticides and fertilizers with it. Tractors cause compaction. Drones don’t. More use of drones means more water and agricultural products stay on the field and help crops that feed us grow.
And while some farmers care deeply about all of this, the ones that are buying drones or having drone services provide them with data and crop spraying are doing it because it saves them money and increases their yields. We all win with agricultural drones. Well, except for the services that operated the light planes and helicopters.
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Source: Clean Technica