Dutch-Belgian research: sunlight to convert CO2 into methane
Researchers of the Dutch TNO institute and the university of Hasselt (Belgium) have forced a breakthrough in using sunlight to convert CO2 into methane, the base ingredient of natural gas. In theory by capturing the CO2 out of the atmosphere and using the methane as a fuel again, you create a zero-emission cycle, professor Marlies Van Bael of UHasselt explains.
When used eventually on an industrial scale, the technique could be used to create a backup method for storing green energy from solar panels and wind mills into methane, that can be liquefied like natural gas today (LNG) and easily be stored and transported.
Energy by sunlight only
The principle of creating a fuel out of CO2 using sunlight is something nature has done for millions of years. It’s called photosynthesis. Traditionally you can make methane by combining CO2 and hydrogen (H2) under high temperature and pressure. Something that was already known at the end of the nineteenth century, but a process that is also very energy-hungry.
What the researchers did was developing a catalytic agent (using the metal ruthenium), that allows to convert CO2 from the atmosphere into methane (CH4) and water (H2O) very efficiently. The energy needed is provided directly by sunlight only.
Low temperature and pressure
In the process 55% of the energy of the sunlight is used. Conventional photo catalysts only use the ultraviolet (UV) spectrum of the sunlight, which means a lot of energy wasted. By concentrating the sunlight, the Dutch-Belgian researchers managed to initiate the process at relatively low temperatures (150°C) and low pressure (3,5 bar).
“For this kind of processes that’s a very low pressure”, explains professor Pascal Buskens from TNO to technical magazine De Ingenieur. “And this temperature we got purely out of concentrated light.”
The methane we know today – the natural gas – is a fossil fuel that is extracted from the earth and burned, creating extra CO2 in the atmosphere. “What we do is to get the CO2 out of the atmosphere to convert it into methane again. If you burn it again, you in fact have a zero-emission cycle that you can repeat”, says Marlies Van Bael.
But proving the efficiency of the process in the lab, is only a first step in actually using it on a larger scale. For this a lot of additional research will be needed, Van Bael says. Because sunlight is essential for the process, transparent reactors have to be developed. “And there is still a long way to go”, she adds.