Fuels from thin air: drop-in liquid fuels from sky CO2, water and solar power


In Finland, we reported last week commercial vehicles operated by the City of Helsinki and bus services commissioned by HSL will fully switch to renewable fuels by 2020.

HSL, Stara, UPM, Neste, Teboil, St1, the Ministry for Economic Affairs and Employment, the Finnish Petroleum and Biofuels Association and the Technical Research Centre of Finland VTT are partners in that project, which is a signature element of the Helsinki region’s Smart & Clean project, which aims to achieve the most attractive zero-emission mobility in the world.

You might wonder if the technical progress towards unlocking biofuels on a grand scale in Finland is keeping up with the switch-over from petroleum, and the short answer is, Yes.

The VTT project

In the latest news, the Soletair process, developed by VTT Technical Research Centre of Finland and Lappeenranta University of Technology, is using carbon dioxide and solar power to produce renewable fuels and chemicals and has reached an end-to-end small demonstration scale.

Olli Pyrhönen, Wind Power Professor, LUT (left) and Pasi Vainikka, Principal Scientist, VTT. (Photo: LUT)

The new power-to-liquid plant was initially launched at the BIORUUKKI Piloting Center of VTT, and now has moved to the campus of LUT. The SOLETAIR project will be completed in mid-2018. It is funded with €1M by the Finnish Funding Agency for Technology and Innovation.

The aim of the project is to demonstrate technical performance and produce 200 liters of fuels and other hydrocarbons for R&D.

The pilot plant is coupled to LUT’s solar power plant in Lappeenranta, and demonstrates the entire process chain, from solar power generation to hydrocarbon production.

The process

The demo plant comprises four separate units: a solar power plant; equipment for separating carbon dioxide and water from the air; a section that uses electrolysis to produce hydrogen; and synthesis equipment for producing a crude-oil substitute from carbon dioxide and hydrogen.

The plant consists of three components. The direct air capture unit developed by the Technical Research Center of Finland (VTT) extracts carbon dioxide from air. An electrolysis unit developed by Lappeenranta University of Technology (LUT) produces the required hydrogen by means of solar power. A microstructured, chemical reactor is the key component of the plant and converts the hydrogen produced from solar power together with carbon dioxide into liquid fuels. This reactor was developed by KIT. The compact plant was developed to maturity and is now being commercialized by INERATEC.

The Direct air capture

Soletair’s creators say:

The current Direct Air Capture unit is a modified version of air-scrubbing units for civil shelters. The main principle for collecting carbon dioxide is adsorption/desorption process using solid amine sorbents. The sorbents used in the direct air capture unit are amine-functionalized polystyrene spherical beads.

Direct air capture of carbon is as follows: (1) Ambient air is introduced to the resin bed by fans. As air passes through the bed, CO2 reacts with the amine in the resin via chemisorption. In parallel water is also physically adsorbed. N2 and O2, major components of air, pass the bed unabsorbed. (2) Next is purging, pneumatic valves are closed and high vacuum is applied to remove air in the bed. (3) The bed is then heated to 80°C, to reverse the adsorption reaction and produce gas (CO2, H2O) in bed. (4) Finally, heating and vacuuming is continuously applied for two hours to collect the product CO2. Water is removed via air-cooled heat exchanger.

The Mobile Synthesis Unit

There are two approaches, both available in the Mobile synthesis unit.

The methanation production line produces synthetic natural gas (i.e. methane) from CO2 and H2 by using Sabatier reaction. Synthetic natural gas can replace traditional, fossil-derived natural gas without any problems. The reactor will be VTT in-house design with a nickel-based catalyst. Operating temperature for the methane production is around 300 °C in mildly elevated pressure.

The Fischer-Tropsch production line has two major steps. First, we will alter CO2 to a more useful component, CO. This is done by reverse water gas shift reaction (rWGS) in which a gas mixture of CO, CO2, H2 and H2O is balanced at high temperature of 800 °C with the help of a precious metal catalyst. The reactor operates at the same pressure as the following Fischer-Tropsch synthesis in order to avoid compression between process steps. The design of rWGS reactor and the catalyst is VTT in-house know-how.

Secondly, carbon monoxide and hydrogen are reacting to hydrocarbons in the Fischer-Tropsch reactor. Our project partner, IneraTec GmbH, has designed and manufactured this ultra-compact and efficient reactor. Fischer-Tropsch reaction produces a wide range of products from light hydrocarbon gases like methane, to liquid components like diesel and up to more solid wax components.

The main parts of Fischer-Tropsch module are the intensified reactor, a hot trap to condense the wax products, and a cold trap to condense the liquid products. The Fischer-Tropsch unit has a cobalt catalyst in a novel compact reactor with integrated water evaporation cooling cycle.

Phase 4: Mobile Synthesis Unit (MOBSU)

Refining into gas, chemicals and fuels

Soletair’s creators say:

The renewable product stream from the Mobile Synthesis Unit is a mixture of hydrocarbons ranging from light gaseous products to liquids and even solid paraffin waxes. The share of each type of product varies a lot depending on the reaction conditions and the catalyst used in the Fischer-Tropsch reaction. It is essential to utilize all of these products fully to make an economically feasible process.

The renewable product that is in gaseous form at room temperature consists of methane, the main component of natural gas, and other light hydrocarbons. It is easy to separate the gaseous fraction from the liquid and solid products. The light paraffins generally known as Liquefied Petroleum Gas, are sold to customers to be used for instance in stoves, grills and refrigerators. 

The liquid product can be fractioned by distillation to renewable gasoline and middle-distillate hydrocarbons. The gasoline fraction is further hydrotreated and reformed over a platinum catalyst in order to increase its octane number and to improve other characteristics for motor use. The middle-distillate fraction is also hydrotreated and thereafter distilled to renewable jet-fuel and/or diesel.

There is only limited use for the wax fraction in special applications such as candles or white oils for consumer products. However, it is possible to hydrocrack the waxes to diesel and jet-fuel and to lesser extent to gasoline. These products can then be combined with the distilled liquid products.

THE INERATEC backstory

INERATEC GmbH is a spinoff of KIT and develops, constructs, and sells compact chemical plants for various gas-to-liquid and power-to-liquid applications. The spinoff is supported under the EXIST research transfer program of the Federal Ministry for Economic Affairs and Energy. In addition, KIT and INERATEC contribute their expertise to the “Power-to-X” Kopernikus project funded by the Federal Ministry of Education and Research.

Scale-up prospects

Pilot-scale plant units have been designed for distributed, small-scale production. It is so compact that it fits into a ship container and produces gasoline, diesel, and kerosene from regenerative hydrogen and carbon dioxide.Production capacity can be increased by adding more units.

Information gathered during the project will be useful for the commercialization of the technologies. New business opportunities will arise for companies such as those benefiting from the carbon circular economy or surplus electricity, or for chemical companies.

The Helsinki backstory

Vehicles serving on HSL’s routes in the Helsinki region include around 1,400 buses, which consume about 40,000 tons of fuel each year. Stara’s own vehicle fleet uses around 2,000 tons of fuel a year. About 500,000 tons of biofuel are produced in Finland on an annual basis.

Helsinki launches project to convert commercial and public transport fleet to 100% bio by 2020

The developing partners

VTT and LUT have invested €1M in the equipment. The research is being funded by Tekes and a number of companies: ABB, ENE Solar Systems, Green Energy Finland, Proventia, Hydrocell, Ineratec, Woikoski, Gasum and the Finnish Transport Safety Agency (Trafi).

Further Readings

You can read about a related set of developments from VTT in detail, here: Liquid transportation fuels via large-scale fluidized-bed gasification of lignocellulosic biomass.

Here are the detailed Soletair process calculations.

And here’s our 2017 Digest Multi-Slide Guide to Soletair technology.

The Digest’s Take

Clearly, the news out of Finland and the deployment of this technology at pilot scale is a material step forward. The process economics we will understand better, later, after the pilot data is obtained, but for a commercially-relevant plant size expect the capex to be daunting, given that the inputs (sun, air, water) are so cheap. This VTT study looked at biomass-to-fuels via F/T — not the same thing, but in the general ball park, and had figures like €360M in there for a full-scale plant.

Second, let’s await the results on catalyst life, cost and yield before we break out the bubbly — the search for the catalytic Methuselah is proving to be daunting when it comes to biosphere — although fair to say that a lot of the catalyst-poisoning impacts seen with biomass (for example, too much steam from the water released from feedstock) would not be a factor here.

However, let’s note this as the technological leap that it is, and also note how Fuel-Forward Finland is turning out to be.

More on the story.

Photo 1: Olli Pyrhönen, Wind Power Professor, LUT (left) and Pasi Vainikka, Principal Scientist, VTT. (Photo: LUT)

Photo 2 Cyril Bajamundi, Research scientist from VTT