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Alternative Energies
The Path Away from Oil

An algae unit for algea production consisting of a row of pipes
Algea farms artificially grow the aquatic plant. Algae can be turned into sustainable biomass, which, in some cases, can replace fossil oil. | Photo (detail): Hilda Weges © picture alliance / Zoonar

Because of global warming, the oil era is coming to an end. This is something that countries and even oil companies themselves have understood. The challenge for the global community now is to find alternatives to oil that do not release greenhouse gases. How can this be achieved?

By Dr. Frank Frick

Greenland announced in summer 2021 that it would stop searching for oil in its territories despite geologists believing that the Arctic is still home to huge undiscovered reserves. The government of this Danish autonomous region justified the step not only by pointing to the negative consequences of oil exploration for nature, tourism and fishing, but also – surprisingly enough – by citing economic analyses. Apparently it is not particularly profitable to drill for oil in the Arctic.

Nowadays even oil companies have accepted that the glory days of the oil business are over. Being a carbon-based energy source, oil releases carbon dioxide (CO2) during combustion – and the signatories to the Paris Agreement want to prevent the Earth from heating up by more than two degrees Celsius. For example, the oil giant BP announced a shift in strategy last year that would see it become “an entirely different type of energy company” by 2030. As CEO Bernard Looney wrote, BP is thereby supporting energy markets in the transition to renewable and other forms of carbon-free or low-carbon energy. But which climate-friendly energy forms are in fact suitable alternatives to oil?

To answer this question, it is important to understand that around two thirds of the oil that is used worldwide – once it has been converted into diesel, petrol or kerosene – are used in road, sea, rail and air transport. This has been calculated by the International Energy Agency (IEA).

Green Electricity for Transport

To move away from conventional combustion engines, the most obvious step is to replace them with electric engines. In Germany, around 440,000 purely battery-powered electric cars were already registered in July 2021 – the total number of passenger cars being over 48 million. Asked how climate-friendly electric vehicles are, the German Federal Environment Ministry writes: “Electric cars are as clean as the electricity they are powered by.” In other words, if more and more people buy electric cars, the climate will only benefit if sufficient wind power and photovoltaic plants are built to produce “green” electricity. In addition, it also matters how environmentally friendly the production of the batteries is.

Green electricity can also be used elsewhere: it allows for example “green” hydrogen to be extracted from water in large-scale facilities. The hydrogen can then be used as a fuel in electric vehicles that are fitted with fuel cells. Fuel cells convert the chemical energy in hydrogen back into electrical energy. The biggest advantage that fuel cell cars have over battery-powered vehicles is their greater range: series-produced vehicles can travel up to 600 kilometres without needing to refuel. One of the downsides is that they require their own infrastructure with filling stations and hydrogen pipelines.

Carbon Dioxide As a New Type of Oil

There is also a way to improve the carbon footprint of vehicles with combustion engines: the carbon dioxide released by their engines is at least partly removed from the atmosphere beforehand: either if it is bound by algae or fast-growing grasses – the resulting biomass then being turned into fuels similar to gasoline or diesel by industry, using green electricity. Or if the industry uses hydrogen to turn CO2 from exhaust fumes into so-called synthesis gas, which is then used to produce synthetic fuel – again using green electricity. Depending on the end product in question, experts refer to this as “Power-to-Gas”, “Power-to-Fuel” or more generally “Power-to-X”. Though demonstration plants exist, use of Power-to-X has yet to become more widespread.

“Engines that are run on hydrogen, or especially on synthetic fuels manufactured from it, require more energy than battery-run electric engines. For example, a car with a combustion engine needs five to six times as much energy – in the form of renewable electricity – to travel the same distance as a battery-run electric car”, calculates the German Advisory Council on the Environment. It believes therefore that the future of hydrogen and synthetic fuels in the transport sector lies elsewhere: in aviation and international shipping, explaining that in those areas “batteries are not a solution on account of the low energy density of electrochemical storage facilities.”

Reducing the Heating Demand

By comparison with the transport sector, doing without oil to heat buildings appears to be only a small problem: according to the IEA, only around five percent of the oil consumed worldwide is used for heating systems in buildings. Furthermore, many buildings can have their future heating demand reduced considerably by thermally insulating their external surfaces. The heat that is then still needed could be supplied primarily by heat pumps that use green electricity to extract energy from the air, water or ground.

IEA statistics reveal that around 17 percent of the oil consumed worldwide is attributable to “non-energy use”. This is an amazingly low figure when one considers that oil is a universal raw material that is used in everything from medicines and plastics to paints and varnishes, pesticides, cosmetics and detergents. Electricity cannot replace oil in these applications because it contains no atoms and is merely the movement of charged particles in a particular direction.

Biomass As Oil Replacement

There are two important climate-friendly substance-based alternatives to oil. One is CO2, which from exhaust gases or the air supplies the carbon atoms that industry then uses to manufacture basic chemicals initially and then chemical-based end products via the Power-to-X route. The other is biomass. The biggest problem is that biomass is made of more complex substances than oil. To replace oil with biomass, the chemical industry would have to completely transform the way it manufactures plastics, cosmetics and the like – a production process that it has optimized over many decades. The new processes are still very energy-intensive and costly at present. However, thousands of researchers worldwide are working feverishly to change this.