Tag: transport

What is LNG and how is it cutting global shipping emissions?

5 July 2019

Sustainable business
Oil tanker, Gas tanker operation at oil and gas terminal.

Shipping is widely considered the most efficient form of cargo transport. As a result, it’s the transportation of choice for around 90% of world trade. But even as the most efficient, it still accounts for roughly 3% of global carbon dioxide (CO2) emissions.

This may not sound like much, but it amounts to 1 billion tonnes of CO2 and other greenhouse gases per year – more than the UK’s total emissions output. In fact, if shipping were a country, it would be the sixth largest producer of greenhouse gas (GHG) emissions. And unless there are drastic changes, emissions related to shipping could increase from between 50% and 250% by 2050.

As well as emitting GHGs that directly contribute towards the climate emergency, big ships powered by fossil fuels such as bunker fuel (also known as heavy fuel oil) release other emissions. These include two that can have indirect impacts – sulphur dioxide (SO2) and nitrogen oxides (NOx). Both impact air quality and can have human health and environmental impacts.

As a result, the International Maritime Organization (IMO) is introducing measures that will actively look to force shipping companies to reduce their emissions. In January 2020 it will bring in new rules that dictate all vessels will need to use fuels with a sulphur content of below 0.5%.

One approach ship owners are taking to meet these targets is to fit ‘scrubbers’– devices which wash exhausts with seawater, turning the sulphur oxides emitted from burning fossil fuel oils into harmless calcium sulphate. But these will only tackle the sulphur problem, and still mean that ships emit CO2.

Another approach is switching to cleaner energy alternatives such as biofuels, batteries or even sails, but the most promising of these based on existing technology is liquefied natural gas, or LNG.

What is LNG?

In its liquid form, natural gas can be used as a fuel to power ships, replacing heavy fuel oil, which is more typically used, emissions-heavy and cheaper. But first it needs to be turned into a liquid.

To do this, raw natural gas is purified to separate out all impurities and liquids. This leaves a mixture of mostly methane and some ethane, which is passed through giant refrigerators that cool it to -162oC, in turn shrinking its volume by 600 times.

The end product is a colourless, transparent, non-toxic liquid that’s much easier to store and transport, and can be used to power specially constructed LNG-ready ships, or by ships retrofitted to run on LNG. As well as being versatile, it has the potential to reduce sulphur oxides and nitrogen oxides by 90 to 95%, while emitting 10 to 20% less CO2 than heavier fuel alternatives.

The cost of operating a vessel on LNG is around half that of ultra-low sulphur marine diesel (an alternative fuel option for ships aiming to lower their sulphur output), and it’s also future-proofed in a way that other low-sulphur options are not. As emissions standards become stricter in the coming years, vessels using natural gas would still fall below any threshold.

The industry is starting to take notice. Last year 78 vessels were fitted to run on LNG, the highest annual number to date.

One company that has already embraced the switch to LNG is Estonia’s Graanul Invest. Europe’s largest wood pellet producer and a supplier to Drax Power Station, Graanul is preparing to introduce custom-built vessels that run on LNG by 2020.

The new ships will have the capacity to transport around 9,000 tonnes of compressed wood pellets and Graanul estimates that switching to LNG has the potential to lower its CO2 emissions by 25%, to cut NOx emissions by 85%, and to almost completely eliminate SO2 and particulate matter pollution.  

Is LNG shipping’s only viable option?

LNG might be leading the charge towards cleaner shipping, but it’s not the only solution on the table. Another potential is using advanced sail technology to harness wind, which helps power large cargo ships. More than just an innovative way to upscale a centuries-old method of navigating the seas, it is one that could potentially be retrofitted to cargo ships and significantly reduce emissions.

Drax is currently taking part in a study with the Smart Green Shipping Alliance, Danish dry bulk cargo transporter Ultrabulk and Humphreys Yacht Design, to assess the possibility of retrofitting innovative sail technology onto one of its ships for importing biomass.

Manufacturers are also looking at battery power as a route to lowering emissions. Last year, boats using battery-fitted technology similar to that used by plug-in cars were developed for use in Norway, Belgium and the Netherlands, while Dutch company Port-Liner are currently building two giant all-electric barges – dubbed ‘Tesla ships’ – that will be powered by battery packs and can carry up to 280 containers.

Then there are projects exploring the use of ammonia (which can be produced from air and water using renewable electricity), and hydrogen fuel cell technology. In short, there are many options on the table, but few that can be implemented quickly, and at scale – two things which are needed by the industry. Judged by these criteria, LNG remains the frontrunner.

There are currently just 125 ships worldwide using LNG, but these numbers are expected to increase by between 400 and 600 by 2020. Given that the world fleet boasts more than 60,000 commercial ships, this remains a drop in the ocean, but with the right support it could be the start of a large scale move towards cleaner waterways.

What is a fuel cell and how will they help power the future?

27 June 2019

Carbon capture

How do you get a drink in space? That was one of the challenges for NASA in the 1960s and 70s when its Gemini and Apollo programmes were first preparing to take humans into space.

The answer, it turned out, surprisingly lay in the electricity source of the capsules’ control modules. Primitive by today’s standard, these panels were powered by what are known as fuel cells, which combined hydrogen and oxygen to generate electricity. The by-product of this reaction is heat but also water – pure enough for astronauts to drink.

Fuel cells offered NASA a much better option than the clunky batteries and inefficient solar arrays of the 1960s, and today they still remain on the forefront of energy technology, presenting the opportunity to clean up roads, power buildings and even help to reduce and carbon dioxide (CO2) emissions from power stations.

Power through reaction

At its most basic, a fuel cell is a device that uses a fuel source to generate electricity through a series of chemical reactions.

All fuel cells consist of three segments, two catalytic electrodes – a negatively charged anode on one side and a positively charged cathode on the other, and an electrolyte separating them. In a simple fuel cell, hydrogen, the most abundant element in the universe, is pumped to one electrode and oxygen to the other. Two different reactions then occur at the interfaces between the segments which generates electricity and water.

What allows this reaction to generate electricity is the electrolyte, which selectively transports charged particles from one electrode to the other. These charged molecules link the two reactions at the cathode and anode together and allow the overall reaction to occur. When the chemicals fed into the cell react at the electrodes, it creates an electrical current that can be harnessed as a power source.

Many different kinds of chemicals can be used in a fuel cell, such as natural gas or propane instead of hydrogen. A fuel cell is usually named based on the electrolyte used. Different electrolytes selectively transport different molecules across. The catalysts at either side are specialised to ensure that the correct reactions can occur at a fast enough rate.

For the Apollo missions, for example, NASA used alkaline fuel cells with potassium hydroxide electrolytes, but other types such as phosphoric acids, molten carbonates, or even solid ceramic electrolytes also exist.

The by-products to come out of a fuel cell all depend on what goes into it, however, their ability to generate electricity while creating few emissions, means they could have a key role to play in decarbonisation.

Fuel cells as a battery alternative

Fuel cells, like batteries, can store potential energy (in the form of chemicals), and then quickly produce an electrical current when needed. Their key difference, however, is that while batteries will eventually run out of power and need to be recharged, fuel cells will continue to function and produce electricity so long as there is fuel being fed in.

One of the most promising uses for fuel cells as an alternative to batteries is in electric vehicles.

Rachel Grima, a Research and Innovation Engineer at Drax, explains:

“Because it’s so light, hydrogen has a lot of potential when it comes to larger vehicles, like trucks and boats. Whereas battery-powered trucks are more difficult to design because they’re so heavy.”

These vehicles can pull in oxygen from the surrounding air to react with the stored hydrogen, producing only heat and water vapour as waste products. Which – coupled with an expanding network of hydrogen fuelling stations around the UK, Europe and US – makes them a transport fuel with a potentially big future.

 

Fuel cells, in conjunction with electrolysers, can also operate as large-scale storage option. Electrolysers operate in reverse to fuel cells, using excess electricity from the grid to produce hydrogen from water and storing it until it’s needed. When there is demand for electricity, the hydrogen is released and electricity generation begins in the fuel cell.

A project on the islands of Orkney is using the excess electricity generated by local, community-owned wind turbines to power a electrolyser and store hydrogen, that can be transported to fuel cells around the archipelago.

Fuel cells’ ability to take chemicals and generate electricity is also leading to experiments at Drax for one of the most important areas in energy today: carbon capture.

Turning CO2 to power

Drax is already piloting bioenergy carbon capture and storage technologies, but fuel cells offer the unique ability to capture and use carbon while also adding another form of electricity generation to Drax Power Station.

“We’re looking at using a molten carbonate fuel cell that operates on natural gas, oxygen and CO2,” says Grima. “It’s basic chemistry that we can exploit to do carbon capture.”

The molten carbonate, a 600 degrees Celsius liquid made up of either lithium potassium or lithiumsodium carbonate sits in a ceramic matrix and functions as the electrolyte in the fuel cell. Natural gas and steam enter on one side and pass through a reformer that converts them into hydrogen and CO2.

On the other side, flue gas – the emissions (including biogenic CO2) which normally enter the atmosphere from Drax’s biomass units – is captured and fed into the cell alongside air from the atmosphere. The CO2and oxygen (O2) pass over the electrode where they form carbonate (CO32-) which is transported across the electrolyte to then react with the hydrogen (H2), creating an electrical charge.

“It’s like combining an open cycle gas turbine (OCGT) with carbon capture,” says Grima. “It has the electrical efficiency of an OCGT. But the difference is it captures CO2 from our biomass units as well as its own CO2.”

Along with capturing and using CO2, the fuel cell also reduces nitrogen oxides (NOx) emissions from the flue gas, some of which are destroyed when the O2and CO2 react at the electrode.

From the side of the cell where flue gas enters a CO2-depleted gas is released. On the other side of the cell the by-products are water and CO2.

During a government-supported front end engineering and design (FEED) study starting this spring, this CO2 will also be captured, then fed through a pipeline running from Drax Power Station into the greenhouse of a nearby salad grower. Here it will act to accelerate the growth of tomatoes.

The partnership between Drax, FuelCell Energy, P3P Partners and the Department of Business, Energy and Industrial Strategy could provide an additional opportunity for the UK’s biggest renewable power generator to deploy bioenergy carbon capture usage and storage (BECCUS) at scale in the mid 2020s.

From powering space ships in the 70s to offering greenhouse-gas free transport, fuel cells continue to advance. As low-carbon electricity sources become more important they’re set to play a bigger role yet.

Learn more about carbon capture, usage and storage in our series:

This is how you unload a wood chip truck

30 June 2017

Sustainable bioenergy
Truck raising and lowering

A truck arrives at an industrial facility deep in the expanding forestland of the south-eastern USA. It passes through a set of gates, over a massive scale, then onto a metal platform.

The driver steps out and pushes a button on a nearby console. Slowly, the platform beneath the truck tilts and rises. As it does, the truck’s cargo empties into a large container behind it. Two minutes later it’s empty.

This is how you unload a wood fuel truck at Drax Biomass’ compressed wood pellet plants in Louisiana and Mississippi.

What is a tipper?

“Some people call them truck dumpers, but it depends on who you talk to,” says Jim Stemple, Senior Director of Procurement at Drax Biomass. “We just call it the tipper.” Regardless of what it’s called, what the tipper does is easy to explain: it lifts trucks and uses the power of gravity to empty them quickly and efficiently.

The sight of a truck being lifted into the air might be a rare one across the Atlantic, however at industrial facilities in the United States it’s more common. “Tippers are used to unload trucks carrying cargo such as corn, grain, and gravel,” Stemple explains. “Basically anything that can be unloaded just by tipping.”

Both of Drax Biomass’ two operational pellet facilities (a third is currently idle while being upgraded) use tippers to unload the daily deliveries of bark – known in the forestry industry as hog fuel, which is used to heat the plants’ wood chip dryers – sawdust and raw wood chips, which are used to make the compressed wood pellets.

close-up of truck raising and lowering

How does it work?

The tipper uses hydraulic pistons to lift the truck platform at one end while the truck itself rests against a reinforced barrier at the other. To ensure safety, each vehicle must be reinforced at the very end (where the load is emptying from) so they can hold the weight of the truck above it as it tips.

Each tipper can lift up to 60 tonnes and can accommodate vehicles over 50 feet long. Once tipped far enough (each platform tips to a roughly 60-degree angle), the renewable fuel begins to unload and a diverter guides it to one of two places depending on what it will be used for.

“One way takes it to the chip and sawdust piles – which then goes through the pelleting process of the hammer mills, the dryer and the pellet mill,” says Stemple. “The other way takes it to the fuel pile, which goes to the furnace.”

The furnace heats the dryer which ensures wood chips have a moisture level between 11.5% and 12% before they go through the pelleting process.

“If everything goes right you can tip four to five trucks an hour,” says Stemple. From full and tipping to empty and exiting takes only a few minutes before the trucks are on the road to pick up another load.

Efficiency benefits

Using the power of gravity to unload a truck might seem a rudimentary approach, but it’s also an efficient one. Firstly, there’s the speed it allows. Multiple trucks can arrive and unload every hour. And because cargo is delivered straight into the system, there’s no time lost between unloading the wood from truck to container to system.

Secondly, for the truck owners, the benefits are they don’t need to carry out costly hydraulic maintenance on their trucks. Instead, it’s just the tipper – one piece of equipment – which is maintained to keep operations on track.

However, there is one thing drivers need to be wary of: what they leave in their driver cabins. Open coffee cups, food containers – anything not firmly secured – all quickly become potential hazards once the tipper comes into play.

“I guess leaving something like that in the cab only happens once,” Stemple says. “The first time a trucker has to clean out a mess from his cab is probably the last time.”