Wet biomass and renewable power yield cost-competitive fuel

In the future, it could become easier to manufacture methanol from biomass decentrally and on site. Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) are proposing a method with which raw and waste materials from plants can be processed in a self-contained procedure under mild reaction conditions.

This method means that the complex drying and transportation of biomass to large biomass gasification plants becomes superfluous. The results are published in the journal Green Chemistry.

Methanol is a versatile basic chemical and promising energy carrier—for example, as a drop-in fuel that can be used directly in existing vehicles. The methyl alcohol with the chemical formula CH₃OH is currently mainly gained from fossil natural gas, making this process incompatible with long-term climate goals.

“Sustainable methanol from biomass will be able to compensate a proportion of methanol production from fossil fuels in the future. However, the current methods mean that this process is very complex and uses large amounts of energy,” says Dr. Patrick Schühle from the Chair of Chemical Reaction Engineering at FAU.

Research into methanol synthesis from biomass has primarily focused on biomass gasification up to now. During this process, waste material from agriculture or forestry and waste products such as hydrolysates from paper manufacturing is first dried, often ground up and subsequently transported to large gasification plants.

The material is first converted into synthesis gas at temperatures of up to 1,000 degrees Celsius and subsequently converted into methanol at pressures of between 50 and 100 bar. Since dry biomass has a lower volumetric energy density, it is often made into pellets before being transported, which means additional costs are involved.

80% carbon efficiency

The new method has a decisive advantage in that it enables wet biomass such as pomace, grass cuttings, wood chips or straw to be processed without prior drying. Since further processing such as shredding and pelleting is not required and hardly any external process heat, smaller plants can also be used.

“This process allows methanol to be produced in a more decentralized manner than was previously possible,” says Schühle. “Investing in this new technology could definitely be worthwhile for large farms or forestry operations or agricultural cooperatives.” The researchers have also been using the expertise of OxFA GmbH, a company based in Scheßlitz near Bamberg and a world leader in producing formic acid from biomass.

Competitive costs

Since the costs for methanol production mainly depend on the availability of green hydrogen, the researchers incorporated an electrolyzer into their design. It produces the oxygen and the hydrogen required for the reaction by splitting water.

Schühle says, “Electrolysis requires large amounts of energy. Ideally, the electricity required comes from renewable sources, such as photovoltaics or a local wind farm.”

Agrivoltaics, which is the use of agricultural land for producing both food and electricity, is increasingly being discussed in this context. With feed-in tariffs continuing to stagnate or even decline, it is becoming more economically attractive to use electricity generated by PV to produce methanol. In addition, it would be possible to produce methanol by storing formic acid temporarily only when electricity prices are particularly favorable.

“We have calculated that green methanol could be produced in the future at a similar cost to methanol produced using natural gas,” explains Schühle. “This means it could make a meaningful contribution to the defossilization of our industrial landscape from an economic point of view.”