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Why are some betting on hydrogen power for ag?

jack dewitt

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Is there a hydrogen-powered tractor in your future? Hydrogen-powered trucks are already on the road in Europe. Switzerland is leasing 1,600 class 8 trucks (heavy duty trucks weighing 33,000 pounds or more) from Hyundai. Hyundai has been manufacturing fuel-cell-powered electric cars for six years, and is now applying the technology to heavy trucks.

Why fuel cells and not batteries? Fuel cells are lighter, and a car can be refueled with hydrogen in five minutes. For large trucks, batteries that would supply juice for a long haul just weigh too much and take too long to recharge. A trucker with an electric power train and an on-board fuel cell and hydrogen tanks could travel 500 miles and fill up again in 15 minutes. The only emission from the trip would be water.

Cummins Inc., known to farmers and truckers for its venerable diesel engines, announced in November 2020 a partnership with Navistar to develop a class 8 electric truck powered by hydrogen fuel cells. Cummins is betting heavily on a hydrogen powered economy and is building fuel cells and electrolyzers for all kinds of applications around the world, including boats, trains, and stationery installations.

What is an electrolyzer and how does a fuel cell work? Think of a car battery with positive (anode) and negative (cathode) electrodes immersed in an electrolyte, sulfuric acid. When the battery discharges, sulfur from the acid accumulates as lead sulfate on the electrodes, leaving water behind in the electrolyte. When charging, the sulfur reacts with the water in the electrolyte reforming sulfuric acid. Lead oxide reforms on the anode and pure lead on the cathode.

Electrolyzers and fuel cells have an anode and a cathode separated by a solid electrolyte membrane. In the electrolyzing reaction, water is fed into the electrolyzer and electricity is applied to the electrodes, causing the water to split into hydrogen and oxygen. The oxygen collects at the anode and is vented to the atmosphere or collected in tanks for commercial use. The hydrogen collects on the cathode and is vented off to storage. Energy from the electric current has bonded hydrogen atoms into gaseous molecules (H2), energy that will be released when the bond is broken.

A fuel cell reverses the process and releases the stored energy. Hydrogen is fed into the anode and air into the cathode. A catalyst embedded in the anode strips the hydrogen atoms’ electron from their proton nucleus. The protons migrate through the electrolyte to the cathode, while the electrons are diverted through an external circuit, creating a flow of electricity on their way to the cathode. At the cathode, they reunite with the protons and oxygen to produce water.

If the electrolyzer is powered by renewable energy or nuclear power, the hydrogen is considered “green.” If the hydrogen comes from fossil fuel and the carbon is released to the atmosphere, it is called “grey.” At present, 95 percent of world hydrogen production is grey, produced by steam methane reforming (SMR). In this process, a mixture of steam and natural gas at high pressure (200-600psi) is heated to a high temperature (1600 F) in the presence of a nickel catalyst. The methane (CH4) in the natural gas breaks down, and the hydrogen is collected and stored while the carbon is oxidized to carbon dioxide (CO2) and released to the atmosphere. If the CO2 is captured and stored for industrial use or injected underground the resulting hydrogen is “blue.”

Another possible industrial pathway being researched for disposal of carbon from fossil fuel is methane pyrolysis. This method results in solid carbon which could be sent to landfills or used in various industrial products. Hydrogen produced from this process is called “turquoise.” The methane source would be natural gas. Heated to 1065 degrees C (nearly 2000 F) in an oxygen deprived atmosphere the four hydrogen atoms in methane split from the carbon atom without resulting in oxidation of the carbon to CO2.

Hydrogen has many industrial uses — making ammonia, refining oil, steel production, food processing, etc. The price of producing green, blue, and turquoise hydrogen will have to come down some to make them competitive with fossil fuels, but expect hydrogen to be a major transportation fuel by 2030.

Back to farm tractors. A farm tractor equipped with hydrogen powered electric motors that will pull heavy machinery all day is not hard to imagine, while the only emission coming from the exhaust is water. And at the end of the day, the farmer pulls up to his/her hydrogen storage tank — supplied from an electrolyzer powered by solar panels — and refills with fuel for the next workday.

New Holland Co. now has a tractor that uses a hydrogen-diesel fuel mix to enhance power and reduce emissions. The engine can run on 100 percent diesel or a diesel-hydrogen mix. Hydrogen is injected and mixed with air during the piston intake stroke. As with all diesel engines, diesel is injected near top dead center of the compression stroke and compression heat ignites the combined fuels. The greenhouse gasses coming out the stack are significantly reduced.

On board electrolyzers that run on power from the tractor’s alternator are available, but buyer beware. When the electrolyzer is turned on and the hydrogen produced is injected into the engine, the claims are more engine power and practically no emissions. But any power enhancement has to be ephemeral. The electrical power required from the alternator is not free, and the power produced from an electrolyzer can never exceed, or even equal, the power put into it. The laws of thermodynamics cannot be suspended.

 

Jack DeWitt is a farmer-agronomist with farming experience that spans the decades since the end of horse farming to the age of GPS and precision farming. He recounts all and predicts how we can have a future world with abundant food in his book “World Food Unlimited.” A version of this article was republished from Agri-Times Northwest with permission.

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