One of the promising alternatives to fossil fuels is methanol, which the global shipping and logistics company Maersk, among others, is investing in for its future fleet of container ships. However, there is a problem when it comes to methanol. Today, 99 per cent of methanol production is based on coal and natural gas, and that's as far from green as it gets. DTU has contributed to developing a new method for producing biogas-based methanol.
"When methanol is produced from biogas, methanol is green because it comes from a renewable source. Biogas is a product of degraded waste from households, agriculture, and production," explains Associate Professor Philip Fosbøl, DTU Chemical Engineering, one of the researchers behind the project.
In the autumn of 2022, the technology was installed in a 40 ft container at Lemvig Biogas, and a year later the plant produced the first litres of methanol.
Methanol without hydrogen added
Traditionally, green methanol is produced from CO2 by adding hydrogen. The hydrogen is obtained through a process called electrolysis, where water molecules are split into hydrogen and oxygen. But electrolysis requires a large energy supply in the form of electricity, and although electricity prices have fallen, it is still so expensive that this form of methanol production cannot compete with methanol produced from fossil sources. DTU's new method does not require the addition of hydrogen to form methanol.
"We take biogas and turn it into synthesis gas, and then we take the synthesis gas and turn it into methanol. And we have a plant that can recycle and use CO2 together with hydrogen and produce even more methanol," says Philip Fosbøl.
Biogas typically consists of two-thirds methane and one-third CO2. Synthesis gas consists of carbon monoxide and hydrogen. To get from biogas to synthesis gas, a catalyst is required to make the process happen, and usually problems arise with deposition of coal on the catalyst. But using a new and innovative catalyst, DTU researchers eliminate this problem.
Since hydrogen is produced by the formation of synthesis gas, there is no need to add hydrogen to produce methanol. However, since biogas contains one-third CO2, you need to recirculate CO2 together with hydrogen from the synthesis gas in order to also convert CO2 into methanol. This process is brand-new and patented and one of the secrets of the great efficiency. The finished product consists of 95 per cent pure methanol, and 99.9 per cent can be achieved, if additional hydrogen from another source is added. Overall, the method has been a breakthrough for green methanol production.
"I do believe we're the first ever to demonstrate that you can produce methanol from biogas," says Philip Fosbøl.
