Tech Talk

AdBlue explainer: Peak body tackles some of the biggest questions

adblue questions

To assist the industry and operators in “demystifying” some of the issues surrounding diesel exhaust fluid/AdBlue, the Truck Industry Council has issued the below question and answer bulletin.

What is diesel exhaust fluid (DEF)?

DEF is a mixture of urea and water, manufactured to meet one of the following automotive standards: ISO 22241, or DIN 70070. DEF is composed of 32.5 per cent “technical grade” urea and 67.5 per cent high quality de-mineralised/de-ionised water.

Why is DEF sometimes called AdBlue?

DEF and AdBlue are the SAME product (made to the same standards). The term Diesel Exhaust Fluid (DEF) is commonly used in North American. The term AdBlue is a trademarked name of the German automotive industry association Verband der Automobilindustrie (VDA) and is commonly used in Europe (and has become the generic term commonly used in Australia). Diesel Exhaust Fluid (DEF) is the technically correct term that should be used.

Do all trucks use DEF?

No, there are some new trucks that do not use DEF to control their exhaust emissions, these trucks use Exhaust Gas Recirculation (EGR) coupled with a Diesel Particulate Filter (DPF) emission technology (EGR-DPF). There are also many older trucks that have very basic, or no emission control systems, these trucks do not use DEF.

TIC estimates that of the 687,623 trucks (with a GVM greater than 3.5t – ABS data January 2021) operating on Australia roads at present, approximately 20-25 per cent require DEF, albeit, many of these DEF trucks are used for linehaul operations and carry a significant amount of Australia’s freight.

How much DEF does a truck use?

For trucks that are designed to use DEF, the amount the truck uses varies on a number of factors, including the emission standard, ADR80/01, /02, or /03 (Euro IV, V, VI, or the alternative Japanese and US standard). However, as a general rule of thumb, the quantity of DEF used is typically only 2-6 per cent of the volume of diesel fuel consumption by the truck.

What is the current situation with DEF supply in Australia?

DEF suppliers have told government and industry organisations, that there are sufficient supplies of DEF in Australia and currently “on the water” enroute to Australia and that the current rolling forecast for supply, of 2 to 3 months, is being maintained, therefore as long as purchase rates remain constant with actual requirement rates, supply can be maintained. Further, suppliers have indicated they believe that the global supply of DEF will improve in 2022 as traditional urea suppliers in Europe, Asia and the USA, ramp up manufacturing to combat the supply shortage out of China.

However, if there is panic buying and hording of DEF, by transport operators here in Australia, then there could well be a shortage of DEF over the coming months. We never had a toilet paper supply issue during Covid, but sales peaks due to panic buying led to shortages on the shelves at times.

Can DEF be stockpiled and does it have a “shelf life”?

DEF should not be stockpiled. It is sensitive to storage conditions and does have a shelf life. If stored between -10 and +30 oC, the shelf life of DEF is approximately one year. At temperatures of around 35 oC, the shelf life is reduced to six months, or less. Note, if DEF is imported pre-mixed and ready to use, the shipping time from source country to Australia must be included as part of the shelf life. This may shorten the times listed above by a further couple of months.

Stock piling DEF beyond standard business use requirements could lead to the DEF spoiling and becoming unusable (with ensuing financial losses for those stockpiling).

If stored, DEF should be stored in the manufacturer’s original container in a well-ventilated, cool and dry area, out of direct sunlight.

What happens when a truck currently runs out of DEF?

This is determined by the emission regulation and is as follows:

  • Derates the engine to approximately 40 per cent of its maximum torque. This is a regulatory requirement in ADR80/01/02/03.
  • The effect on speed/efficiency varies depending on the trucks load. If the truck is empty, the engine derating would likely reduce the trucks speed by 50-60 per cent. If the truck is fully loaded, the engine derating would likely reduce the trucks speed by 80-90 per cent, effectively allowing the truck to crawl to a safe place to park, then allowing the DEF to be replenished and the truck to resume normal operations.

Can a DEF emission control system in a truck be “turned off”?

This question needs to be addressed on a legal, technical and practical basis:

  • Regulatory requirements, no this would be illegal in Australia.
  • Technical, would require a significant amount of R&D (months, possibly a year or more) by the truck/engine Original Equipment Manufacturer (OEM) overseas (no engine emission development is conducted in Australia) to see if this was technically possible and to determine what the short, mid and long term impacts on the engine and truck would be.
  • Practically, TIC is aware of DEF defeat devices that have been used by some truck operators, of course these devices are illegal and generally their use leads to failure of the trucks exhaust emission system, which in turn prevents engine and truck operation (the engine is effectively strangled by a “collapsed” exhaust system catalyst). Whilst the purpose of injecting DEF into the exhaust is to create a chemical reaction that “kills off” the NOx that is produced within the engine, DEF is also used to maintain the exhaust catalyst within a specific operational temperature range. Without DEF, exhaust temperatures can significantly increase, leading to overheating of the exhaust catalyst and internal failure of the exhaust catalyst (distorted internals that can collapse and block the exhaust system). Even if the catalyst does not suffer an internal mechanical failure, use without DEF, even for a short period, will lead to irreversible chemical etching of the catalytic plates, destroying the catalyst’s effectiveness. A “poisoned” catalyst cannot be repaired, or recovered, it is destroyed and will need replacing, at a cost of many thousands of dollars.

Can diluted (watered down) DEF be used in a truck?

There is no point in using diluted (watered down) DEF in a truck’s engine. The DEF emission system on a truck works by measuring the NOx that is emitted by the engine after the DEF is injected into the exhaust system. If the DEF has a lower concentration of urea (old/aged, or diluted DEF), the truck’s emission system will simply increase the injection rate of DEF to “kill” the NOx to the required (ADR) level. If the DEF was diluted (watered down) too much, then the truck’s DEF system would not be able to inject enough DEF into the exhaust system to “kill” the NOx to the required level (the DEF pump could not supply enough of the diluted DEF), this would cause a fault in the DEF system and the truck’s engine would be derated to approximately 50 per cent of its maximum power. This is a regulatory requirement in ADR80/01/02/03. This reduction in power would allow the truck to crawl to a safe place to park, then allowing the DEF to be replenished with the correct concentration of urea and the truck to resume normal operations.

Can DEF be manufactured from fertiliser grade urea?

The short answer is NO, DEF cannot be successfully made from fertiliser grade urea. Fertiliser grade urea contains many other chemical impurities including metals, chlorines, etc. These impurities will damage the trucks DEF system and importantly the impurities will, in a very short time, “poison” the engines exhaust catalyst, destroying the catalyst for life. This catalyst “poisoning” is similar to what happens in a petrol engine car if the petrol has lead in it. That is why lead was removed from petrol years ago and why DEF can only be manufactured from “technical grade” urea. It may however, be possible to further refine fertiliser grade urea to produce technical grade urea, that could then be used to manufacture DEF.

In the case that a truck needs to continue to drive without DEF, what would their options be?

Nothing, there are no options, DEF is required for the truck to operate, it is no less important than diesel fuel in a truck’s operation.

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