Environmental

Could using CO2 as a fuel save the combustion engine?

EPFL has developed a concept for capturing and recycling CO2.

Although the electrification of private transport could be one of the solutions for reducing the CO2 emissions linked to transport, reducing those generated by public transport and freight (buses and trucks) is more problematic.

Researchers from the Faculty of Engineering Sciences and Techniques at the EPFL (The Swiss Federal Institute of Technology in Lausanne) are proposing a new solution to reduce the emissions linked to this sector by 90%: capture the CO2 directly from the exhaust, liquefy it in a tank located on the vehicle’s roof and convey it in liquid form to the pump, where it will be converted into conventional fuel by renewable energy.

Several technologies introduced by the EPFL have been combined to allow the CO2 to be captured then converted from the gas to the liquid state, while making maximum use of the available energy on board, such as the engine’s heat. In their study, the scientists use the example of an HGV.

First of all, the vehicle emissions are recovered directly from the exhaust and cooled, the water is then separated from the gases. In order to isolate CO2 from the other gases (nitrogen and oxygen), the gases are passed though a modulated-temperature adsorption system, using Metal Organic Framework (MOF) materials or adsorbents, designed specially to absorb CO2. These materials are developed by the Energypolis teams at EPFL’s Valais Wallis campus. Once saturated with CO2, this material is heated to extract pure CO2. High-speed turbochargers developed by the EPFL campus in Neuchâtel use the engine’s heat to compress the CO2 and turn it into liquid. The latter is stored in a tank. It can be converted into conventional fuel in a special station, using green electricity.

The entire process will take place in a 2 x 0.9 x 1.2 m capsule, located above the driver’s cab and representing only 7% of the vehicle’s payload. The researchers calculate that a truck consuming 1 kg of conventional fuel could produce 3 kg of liquid CO2 and that the conversion is made with no energy penalty.

As for the 10% of non-recyclable CO2 emissions, the researchers propose offsetting them by using fuel derived from biomass.

In theory, this system could work on all types of heavy goods vehicles, coaches and even boats, whatever fuel is used. The advantage of this system on an industrial level is that, unlike electric or hydrogen solutions, it enables the fleet of HGVs that are already in use on our roads to be retained, while making them carbon neutral.

Now that the patent for this system has been filed, the researchers hope to improve their process and miniaturise their system to make it suitable for use on cars with thermal engines that will then operate on a quasi-closed circuit using greenhouse gases.

 

Electric cars and the environment

Ever-increasing concerns over the green credentials of traditional combustion engines have, in part, prompted a noticeable shift towards electric vehicles.

According to figures released by the Society of Motor Manufacturers and Traders (SMMT)1, year-to-date sales of pure electric vehicles in September 2019 are up 122% on the same period in 2018.

While the numbers remain low – 25,097 pure-electric cars have been sold in the year so far, just 1.3% of UK registrations – the electric vehicle (EV) sector looks set for rapid growth.

If the prospect of zero tailpipe emissions wasn’t enough, rising interest is also being fuelled by affordability, the increased availability of charging points, the threat of pollution charges in city centres, scrappage incentives and government grants.

So, are electric cars as green as people think? We examine the evidence.

From the moment an electric car hits the streets, it emits no tailpipe emissions, but will still produce some degree of pollution from tyre and brake particles. The real environmental impact though, occurs before an electric car has left the factory floor.

A report by the European Environment Agency (EEA) highlights that emissions from battery electric vehicle (BEV) production are generally higher than those from internal combustion engine vehicle (ICEV) production.

One study suggests that CO2 emissions from electric car production are 59% higher than the level in production of traditional internal combustion engine vehicles (ICEVs).

The greater emissions are largely attributed to the battery manufacturing process, something the EEA suggests could be amended to incorporate increased use of renewable energies.

However, once an electric vehicle begins its life on the roads the bulk of its emissions have already been produced; whereas with combustion engines, a long period of tailpipe emissions are just beginning.

Most car batteries are made in China, South Korea and Japan, where the use of carbon in electricity production is relatively high.

An EEA report found that in China, 35-50% of total EV manufacturing emissions arise from electricity consumption for battery production. These emissions are up to three times higher than in the United States.

In China the proportion of renewable energy in the electricity mix is projected to rise sharply between now and 2025.

If electricity was generated by wind power alone, China would see a 50% drop in emissions from the production phase compared with the current EU electricity grid mix.

Reducing worldwide carbon intensity by 30% would see a 17% reduction in greenhouse gas emissions from battery production by 2030.

Lithium batteries found in electric cars, tend to be made up of base metals such as copper, aluminium and iron. Other critical raw materials (CRMs) with high economic importance and high-risk supply feature more in electric vehicle production than ICEV production, and require energy-intensive extraction.

Improved energy production techniques and more advanced battery technology will result in less reliance on critical raw materials. This means that electric cars will get greener as the means to produce and power them begin to leave less of an environmental impact.

A well-maintained, modern electric car should be able to achieve 150,000 miles and beyond before the battery begins to lose capacity, although this figure will reduce if a rapid-charger has been the predominant means of charging.

At some point, owners will be faced with recycling or replacing the battery – likely to then cost far more than the value of the vehicle.

Currently there is no standardised process for recycling batteries, but the benefits make a considerable difference to electric vehicles’ green credentials.

Reports suggest that material recovery can lead to a reduction in energy of 6-56% and a 23% reduction of greenhouse gases, compared with virgin material production.

Car manufacturers have started to act. Volkswagen introduced a scheme in 2019 which it believes will see 97% of all the raw materials used in new EV batteries reused by 2046.

A standardised recycling technique and testing of second-use applications for these batteries has the potential to significantly reduce the environmental impact of their production.

With production aside, an electric car is then only as clean as the power it uses to keep moving.

Until 100% of EVs run on 100% renewable power, the electricity source will remain a thorn in the side of an EV’s environmental merits.

Crucially though, an electric vehicle has the potential to be 100% green, at least from the perspective of driving and the source of power. And the good news is that energy production is reaching a significant turning point.

The UK National Grid predicts there will be 36 million electric vehicles on the roads by 2040 – a figure revealed before the government’s plan to bring the ban on new petrol and diesel sales forward to 2035.

Everything points to battery-electric cars being the future of mass transportation. For a while, electric was seen to be neck-and-neck with hydrogen in the race to achieve mainstream appeal, but it would appear EV have edged ahead.

While the likes of the Toyota Mirai and Honda Clarity are undoubtedly impressive, they are produced in limited quantities and sold in small numbers. Hydrogen might have a strong future in Japan, but only through large-scale investment from the government.

Other companies to nail their flag to the EV mast include Volvo, which has announced every new car it launches from 2019 will feature an electric motor, and Jaguar, which promises to do the same thing from 2020.

Next-generation EVs will be bespoke builds, offering extended range, faster charging times and improved practicality. In short, EVs will go from niche to mainstream.

Take the updated version of the Nissan Leaf, which offers an extended 235-mile range and ability to be charged to 80% in just 40 minutes.

The forthcoming Tesla Model 3 could achieve up to 220 miles of range, while the Jaguar i-Pace is predicted to offer a range of at least 311 miles.

According to Zap-Map, there are currently around 27,000 charging connectors in the UK across 10,000 locations. Research from Deloitte suggests that around 43,000 charging points will be needed by 2030.

Of course, some degree of home charging will be required if infrastructure is to cope with the increased number of electric cars. In July 2019 a UK government consultation set out plans that all new UK homes must have charging points included.

Once on the road, EV’s are responsible for much lower emissions than cars powered by fossil fuels. The challenge now is to reduce the emissions produced through manufacturing and energy production.

As electric cars become more widespread, cleaner energy generation, better recycling schemes and improvements to battery technology are all needed before we feel the full benefit of their green potential.