Whether cruise ship, freighter or ferry: So far, shipping has been anything but environmentally friendly because its fuels produce large amounts of carbon dioxide, soot and other air pollutants. But German researchers have now developed a bio-fuel that is made from plant waste and produces less harmful emissions. Its energy density is even higher than that of normal marine diesel.
Shipping is responsible for the emission of around one billion tons of carbon dioxide worldwide. In addition, the freighters, cruise ships or ferries operated with heavy oil or ship diesel emit large quantities of soot, fine dust, nitrogen oxides and other air pollutants. These not only pollute the environment, they can also be harmful to health, particularly for residents of coasts and port cities. One could change the bad climate balance of shipping by new, more environmentally friendly fuels.
From wheat straw to ethanol to diesel and co
This is where the development of a research team from the Fraunhofer Institute for Environmental, Safety and Energy Technology (UMSICHT) comes into play. Andreas Menne and his team have developed a method that can be used to produce biofuels from plant waste and thus renewable raw materials. They already produce 20 liters of this bio-fuel per week in their test facility. In the first step, the plant material is fermented to bioethanol. “Whether straw, leaves, sawdust or residual wood – we can use almost anything as a raw material for bioethanol,” explains Menne. “Actually, I can take any other alcohol.”
In the next step, the alcohol is passed into an evaporator. There it is heated to 350 degrees and exposed to a pressure of 20 bar, then the gaseous alcohol flows into the heart of the plant, the tubular reactor. This is filled with activated carbon, which is coated with a special catalyst. It ensures that the flowing ethanol gas reacts with the activated carbon and thereby forms hydrocarbon chains of different lengths – the basic building blocks of diesel, petrol or kerosene. “A catalyst is often developed in the laboratory and it is then difficult to produce it in large quantities,” says Menne. “But for this we can buy the materials inexpensively, because it is not made of precious metals or rare earths.”
Less soot, less greenhouse gases
But how good are the biofuels produced in this way? Researchers at the Fraunhofer Institute for Chemical Technology (ICT) in Pfinztal in Baden have examined this. On their test bench, they tested the biofuel with common commercial engines and determined engine performance and exhaust gas values under various conditions. It turned out that bio-fuel reduces greenhouse gas emissions by up to 30 percent compared to fossil fuel. The emission of carbon monoxide, hydrocarbons and soot is also lower than that of normal diesel. At the same time, bio-fuel even has a slightly higher energy density, as the researchers report. Because its physical nature is very similar to that of fossil diesel, biofuels can completely replace classic fuels without any risk to the engine.
The question remains whether the production of this bio-fuel is also ecologically ahead. Venkat Aryan from Fraunhofer UMSICHT has determined the eco-balance of the fuel for this. It takes into account all greenhouse gases that arise from the extraction of raw materials through chemical conversion processes to the combustion of the fuel. The result: With 64 to just under 92 grams of CO2 equivalents per megajoule, the biodiesel from wheat straw also produces fewer greenhouse gases in the overall balance than classic diesel from petroleum – 94 grams of CO2 equivalents per megajoule add up to this.
Can be used directly as a marine diesel
According to the scientists, their biofuels made from vegetable raw materials offer a good alternative for petroleum-based fuels that can already be used directly in shipping. “Our fuel can turn into gasoline, diesel or even kerosene for airplanes,” explains Menne. However, the production of biokerosene is more complex, while marine diesel does not require refining by a refinery. It is therefore the easiest to replace. “You could just put our system in a port,” explains the researcher. “Our process is so straightforward that the shipping companies could produce their diesel themselves. Then the time of the big stinkers would be over quickly. ”
The technology for this is already ready for the market, as the Fraunhofer researchers report. So far, synthetic diesel has been more expensive than petroleum diesel. Menne is confident that this could change soon.
Source: Fraunhofer Society