New directions for fertilizer plants: Do you know about ammonium fuel?

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As we move towards net-zero carbon emissions by 2050, you'll be hearing more about ammonia as a clean fuel option. It looks to be one of the clean fuel options for long-distance hauling and trucking. So, what is it, how is it made, and how does it become a green fuel? As a fuel, ammonia (15.6 MJ/L) has 70% more energy by volume than liquid hydrogen (9.1 MJ/L at low temperatures) and nearly three times the energy of compressed hydrogen (5.6 MJ/L at 700 bar pressure). By weight, it carries 6250Wh/kg of energy, which is more than 20 times the energy of today's lithium batteries, enough to overcome the inefficiency issues introduced when extracting energy. There are a few key ways to use ammonia as a fuel. One is to "crack" it into H2 and N2 gases, and then use the hydrogen as a combustion fuel or to generate electricity through a fuel cell. Australian Commonwealth Scientific and Industrial Research Organization calculations show that when ammonia is converted into hydrogen and run through a PEM fuel cell, approximately 2094Wh/kg of energy can be obtained. This is approximately 19% of the 10 MWh/ton of renewable energy required to create ammonia. Another option is to burn ammonia directly as a combustion fuel, combining with oxygen to release energy, with nitrogen and water being the only off-gas products. It's not super simple. Ammonia does not burn at lower temperatures, so another combustion fuel is usually required at the same time. Additionally, if the combustion process is not well managed, it can release large amounts of nitrous oxide, a powerful greenhouse gas. But if done properly, CSIRO calculated the result to be 2315Wh/kg, or 21% of the energy input for ammonia synthesis. A third approach is to use ammonia directly as fuel in high-temperature solid oxide fuel cells (SOFCs), using nitrogen and water as by-products to generate electricity. This is more efficient, with a return of up to 5510Wh/kg, or 50% of the energy input. One drawback here is that SOFC technology is expensive and tends to work slowly, providing low power density, but it is possible to run a hybrid system with a fuel tank that converts a proportion of the ammonia fuel into hydrogen when bursts of power are needed. Today, ammonia production is a dirty and energy-intensive process, with most of the hydrogen required being extracted from steam-reformed methane gas. Extracting natural gas from the ground always results in methane leaking into the atmosphere, where it is a very powerful greenhouse gas, and the steam reforming process not only uses a lot of energy but also releases carbon dioxide as part of the reaction. In order to combine these H2 molecules with the N2 molecules taken from the atmosphere, you need to break the strong bonds holding these nitrogen atoms together. This is usually done via the Haber-Bosch process, which produces liquid ammonia by heating a mixture of the two gases to above 400°C (752°F) and pressurizing it to about 250 bar with the help of an iron catalyst. Needless to say, the cost of energy here is huge, and most of it typically comes from fossil fuels. Ammonia is produced in huge quantities, it is the second most produced chemical in the world, and it currently accounts for 2% of global fossil energy use and related emissions. Combined with chemical processing and fugitive methane emissions, ammonia is the largest source of pollution in industrial chemical production. https://p6.toutiaoimg.com/origin/pgc-image/ShxniWTHSl31I6?from=pc It is possible to reduce emissions from current ammonia production by replacing fossil energy with green energy in the Haber-Bosch process and using carbon capture and storage to separate and store much of the CO2 emissions from the methane reforming process. But it's impossible to prevent fugitive methane from leaking, so this "blue ammonia" still has an environmental cost. This is considered a transitional step. True "green ammonia" can be produced by using renewable energy to generate hydrogen through electrolysis and then through the Haber-Bosch process powered by green energy. This is a relatively inefficient use of renewable energy, but it gives you a truly emissions-free source of ammonia. This is considered a medium-term solution. There are other completely green methods under development, including "reverse fuel cell" technology that converts renewable energy, water and air into ammonia, without the need for a separate hydrogen electrolysis process. These methods are starting to look quite effective, but currently they are still too slow to produce the large quantities of ammonia needed for current agricultural uses, let alone serve the emerging green liquid fuel market. Essentially, ammonia does have the potential to become a usable clean fuel. But the path here is not clear. A lot of work needs to be done to develop and promote new green ammonia production methods, and at the other end of the spectrum, a lot of work needs to be done to develop efficient and powerful ways to use the energy it stores. Both sides of the equation need to become cost competitive if cheap, dirty diesel is to be replaced.