ENplus Requirements for Wood Pellet Traders | Forever Fuels

The ENplus wood pellet accreditation scheme sets the rules that producers and traders (i.e. suppliers) must follow. It is supposed to ensure that the wood pellets arrive in a customer's store in the best condition possible. The rules are set out in the ENplus Handbook. As of late 2016, version 3 is the current version of the ENplus Handbook.

ENplus was established by the Germans and Austrians. Its governing body is the European Pellet Council. Although it is now a global scheme, the Germans and Austrians took the lead on drafting the rules. As you would expect of Germanic nations, the rules included quite specific and strenuous requirements that the authors had learnt would yield the best results, from many years of supplying wood pellets.

Some of these requirements, such as the effective requirement for pressurised tankers for smaller deliveries, involved substantial costs of compliance. Many suppliers in countries with immature pellet-heating markets, such as the UK, did not want to incur the cost when their market was too small to support it.

The European Pellet Council (EPC) therefore agreed to a temporary derogation for a limited period of three years, in order to encourage the uptake of the scheme in immature markets like the UK. The EPC intended that suppliers in those countries would use this period to equip themselves properly as the market grew to support it. But (despite the rapid growth in the UK pellet market in the following years) most British suppliers preferred not to spend the money and instead used the time to lobby for an extension of the derogation.

They achieved their objective in the negotiations over version 3 of the ENplus Handbook. In order to avoid conflict between countries that wanted higher standards (such as Germany) and countries that wanted lower standards (such as the UK), the EPC:

  1. watered down the rules in the international version of the Handbook, and
  2. agreed to allow national variations on the standard international ENplus rules.

The UK took advantage of this to further water down the standards required for deliveries, to the point that almost anything goes. Below is a comparison of the requirements, where the international rules and the UK rules differ.

International Rules UK Rules

Delivery requirements: 

  • Silo vehicles for Part Load Deliveries to end-users shall be equipped with a low-abrasion feeding system – the delivery pipe shall have the ability to deflect electric current (grounding of the vehicle) and shall be coated to reduce friction. The connection between pipes shall not contain sharp edges against the pellet flow. When vehicles other than silo trucks are used for end-user deliveries, only equipment can be used that guarantees a careful delivery with a minimized generation of fines.

  • Vehicles equipped with a rotary feeder shall not be used for end-user delivery due to the risk of generating an increased amount of fines. The International Management may agree with the company on an individual transition period.

  • Vehicles for Part Load Deliveries to end-users must be equipped with a gauged on-board weighing system. Individual exceptions from this rule may be allowed by the Competent Certification Body for a transition period.

  • Silo vehicles for Part Load Deliveries to end-users shall have a device to extract the supply air from the storage facility during the delivery if needed. The Competent Certification Body may accept other solutions that prevent dust from being blown into the building of the customer. The International Management shall be informed about which other solutions are accepted. 

  • Where pellets are blown from a silo truck into the end-users storage, the blowing distance has not exceeded 30 m including the internal ducts. 

Delivery requirements: 

Equipment for end-user deliveries must guarantee a careful delivery with a minimized generation of fines. 

  • All delivery vehicles making part load deliveries must be fitted with equipotential bonded delivery hoses AND the ability to be earthed (grounding of the vehicle) and shall be coated to reduce friction. The connection between hoses shall not contain sharp edges against the pellet flow.

  • Where Part Load Deliveries of bulk pellets are made to end-users, appropriate measures shall be implemented and/or appropriate equipment shall be used in order to guarantee that the weight of the delivered pellets is determined in an accurate way.

  • Air used to deliver the pellets must be able to exit the store and store area without causing a dust nuisance. 

  • The amount of fines in a delivery will only be < 4% w-% when the total length to be blown between the end user storage and delivery vehicle is less than 30 metres unless otherwise specified by the delivery company prior to delivery.

    ENplus certified companies in the UK may provide further restrictions on the blown length to allow for any bends, gradients or other impediments to smooth delivery. 

Customer's storage requirements:

  • The end-user’s store has been cleaned periodically. The frequency of the cleaning of stores shall be based on the annual consumption. Stores with an annual consumption of ≤ 15 tonnes shall be cleaned once in two years. Stores with an annual consumption ˃ 15 tons shall be cleaned once per year at least. 

Customer's storage requirements:

  • The end-user’s store must have been cleaned periodically. The frequency of cleaning is based on the number of deliveries but a minimum of once every two years. The store must have been completely cleaned after every 5 deliveries. 

Supplier's storage requirements:

  • If wood pellets from the store are delivered to end-users, the storage facility shall be equipped with a device to separate the fine fraction before loading the transport vehicle. The device shall be constructed to reduce the share of fines from 10 w-% to below 1 w-% in day-to-day-operations. Pellets shall not be stored after separation of fines. If there is a hopper it shall be completely discharged at least once for every 10 times the hopper’s volume has been used. Where the hopper’s capacity is bigger than 20 metric tonnes it shall be completely discharged every 200 tonnes. 

Supplier's storage requirements:

  • If wood pellets from the store are delivered to end customers, the storage facility shall be equipped with a device to separate the fine fraction before loading the transport vehicle. The device shall be constructed to reduce the share of fines to below 1 w-% in day-to-day-operations. Pellets shall not be stored after separation of fines. If there is a buffer after the screen, it must be completely discharged at an interval determined by multiplying the capacity of the buffer by 5. For example, if the buffer holds 5 tonnes, it must be completely discharged every 25 tonnes. This provides a consistent approach when compare to the requirements placed on end-users. 

If you are checking for yourself, the sections above are on pp.31-34 of each of the Handbook versions. "Silo vehicles" in the international version refers to pressurised tankers.

It should be apparent that the UK rules are less burdensome on the operator, and less protective of the customer, than the international version. The UK version is missing the following items from the international version.

Silo Trucks

When vehicles other than silo trucks are used for end-user deliveries, only equipment can be used that guarantees a careful delivery with a minimized generation of fines.

The specific mention of silo trucks (i.e. pressurised tankers) was removed because the UK Pellet Council did not want customers to know that it is harder (and in some cases impossible) with other types of vehicle to do "a careful delivery with a minimized generation of fines".

Rotary Feeders

Vehicles equipped with a rotary feeder shall not be used for end-user delivery due to the risk of generating an increased amount of fines.

Tipper-blowers and Transmanuts have to use rotary feeders to control the flow of product into the blow-line and to prevent the delivery air from blowing back into the body of the truck. This is effectively a requirement to use pressurised tankers, because the experts on the continent know that pressurised tankers give better results. The Brits took it out because they want to be free to use vehicles that are more widely-available secondhand, to reduce their capital investment, regardless of the impact on the quality of the delivery. 

Gauged on-board weighing system

Vehicles for Part Load Deliveries to end-users must be equipped with a gauged on-board weighing system.

"Gauged on-board weighing system" means a Legal-for-Trade weigh-loader. This is not just a requirement of the international ENplus rules, but also of Trading Standards where customers are being billed on the basis of the weight measured at the time of delivery. But the UKPC took it out anyway. As we explain on our page on Accurate Billing, it is difficult to offer Legal-for-Trade weighing on a tipper-blower. Operators may tell you that their trucks are calibrated and that this is functionally equivalent, but it is not the same thing. If it were, they would get their trucks certified as Legal-for-Trade.

The UKPC's version - "appropriate measures shall be implemented and/or appropriate equipment shall be used in order to guarantee that the weight of the delivered pellets is determined in an accurate way" - is intended to allow for options such as weighing over a weighbridge before and after the delivery. But whereas honest operators might do this genuinely, if the option is permitted, there is no way for a customer to know that a less scrupulous operator did not blow off some pellets before the second measurement to increase the bill. The only way for a wood pellet customer to know for sure that they have been billed for the correct quantity is for that quantity to be measured on site by weigh-loaders certified Legal for Trade. That is why the international ENplus rules insist on it. But the UK thinks it is more important to cater to any old delivery vehicle than it is to remove opportunities for cowboys to game the system.

Extraction Fan

Silo vehicles for Part Load Deliveries to end-users shall have a device to extract the supply air from the storage facility during the delivery if needed.

Not all wood pellet stores require active venting during delivery. But the majority do. The international ENplus rule is not saying that extraction must always be used. It is saying that all trucks should be equipped to offer it, because it will be required often enough that all trucks are likely to deliver to sites that require it.

That is not unreasonable. The UK rule is unreasonable: "Air used to deliver the pellets must be able to exit the store and store area without causing a dust nuisance." The ENplus scheme is an accreditation scheme for fuel suppliers, not for equipment installers. But the UK rule appears to be stating how wood pellet stores should be designed, not how wood pellet suppliers should ensure that they can cater to the requirements of the installations that they will encounter.

Moreover, the UK rule does not say that the store should not be pressurised, only that a dust nuisance must not be created when the air escapes. A supplier could pressurise a store to 1 barg and yet comply with the UK version of the ENplus Handbook. The store will be at significant risk of damage and the wood pellets will be degraded, but the supplier will not be at fault.

This may reflect a common misunderstanding about the purpose of active venting. It is often referred to as "dust extraction", but that is not its main purpose, nor is it especially effective at removing the dust. The point of active venting is that the truck's blower is pushing hundreds of cubic metres of air per hour into the store, which will be pressurised and possibly damaged if the air flow-rate out of the store is not at least as fast as the flow-rate into the store. Pressurisation is also bad because it reduces the pressure gradient along the delivery pipes, which reduces the solids loading factor that can be achieved, and that increases the degradation that will occur during delivery.

For health and safety, it is important to capture the dust that escapes from the store. But that is not the purpose of active venting. The purpose is to avoid pressurising the store. It reflects the depths of ignorance amongst many British wood pellet suppliers that the UK rules on venting refer only to the risk of a dust nuisance and not to the risks of pressurisation.

It is possible to design stores to release this air without significant pressurisation through "passive venting" if the cross-sectional area of the vents is wide enough. A rough rule of thumb is that the area of the vents should be at least double the area of the inlet pipe if "passive venting" is to be relied upon. That either means one big vent or two standard-sized vents. The big vent will require a big connector and double-sized filter bag, which fuel suppliers will be less likely to carry on their truck than a suction fan. Two standard-sized vents require two connectors and two filter bags, which fuel suppliers are also unlikely to carry. In practice, proper passive venting means not just wide vents, but also the permanent installation of filter bags to prevent the dust emissions that the UK rules talk about. Of the thousands of installations that we have delivered to, we have only ever seen this once - to the credit of a leading football club and their installer, as it happens.

The reason that the majority in the UK Pellet Council don't want to be required to carry a suction fan is because many tipper-blowers have nowhere to put a fan that is fit for purpose. Pressurised tankers have a lot of space beneath the sloping floor of the silo to store many lengths of delivery pipe, and compartments to hold the suction fan, bag filter, connectors, extension leads, etc. Tipper-blower operators often have to choose between not offering extraction, or carrying an inadequately-sized fan (like a converted hoover) in the cab. The UK version of the ENplus Handbook lets them get away with it.

The international version is better but not good enough. "A device to extract the supply air" could refer to a Henry Hoover. That would not be enough to remove the air at the rate that the blower delivers it. The Handbook should be specific that a device is required that extracts air at a faster flow-rate (at normal temperature and pressure) than the blower on the truck.


In other regards, the UK rules were more specific than the international rules. These were often not to apply tighter rules to British wood pellet suppliers, but to limit more tightly the circumstances in which the rules would apply to them.

Limits on the 4% fines guarantee

The amount of fines in a delivery will only be < 4% w-% when the total length to be blown between the end user storage and delivery vehicle is less than 30 metres unless otherwise specified by the delivery company prior to delivery.

It is clear that this rule also applies in the international ENplus Handbook: "Where pellets are blown from a silo truck into the end-users storage, the blowing distance has not exceeded 30 m including the internal ducts" (p.23). Presumably, the wording was changed partly to remove another reference to "silo trucks" (i.e. pressurised tankers) and partly to make it clear to customers that they should expect more than 4% fines for blowing distances over 30 metres, rather than that they simply do not have a right to complain if they experience more than 4% fines in those circumstances.

ENplus certified companies in the UK may provide further restrictions on the blown length to allow for any bends, gradients or other impediments to smooth delivery. 

This is a case where the UK rules are a partial improvement on the international rules, although this is insufficiently specific. It was raised by Forever Fuels during the negotiations, on the basis of principles of pneumatic transfer that had been taught by the Wolfson Centre for Bulk Solids Handling Technology. Impacts from bends, gradients and obstacles have a more detrimental effect on wood pellets than travelling long distances in a straight line.

A true reflection of these principles might have allowed for blowing distances of greater than 30 metres, provided that there were no bends, gradients or other obstacles. But most of our competitors' trucks can't blow more than 30 metres because they are not pressurised tankers. So we are left with the worst of both worlds for pellet-users, with a distance limit of 30 metres because of the limitations of the vehicles commonly used in the UK, and the option to shorten this distance if the supplier feels it is justified by the pipe route.

Frequency of cleaning the end-user's store

The store must have been completely cleaned after every 5 deliveries.

Both the international and the UK rules agree that the store should be cleaned at least every other year. But the international rules apply this to customers using less than 15 tonnes per year, whereas the UK rules make it the baseline for everyone. Stores should be cleaned more frequently than this if they use more than 15 tonnes a year according to the international rules, or if they take more than 5 deliveries every two years according to the British rules.

This is another case where the British rules are an improvement, suggested by Forever Fuels on the basis of our Wolfson training, and simple common sense.

A customer using 12 tonnes per year might put in a 3-tonne store. A customer using 18 tonnes per year might put in a 20-tonne store. In the first case, they will have had around 10 deliveries before they clean out their store, according to the international rules. In the second case, they will have to clean out their store every year, even though they only take one delivery per year.

The UK rules are intended to reflect the fact that the fines are accumulating with every delivery, and the quantity of fines that affects the system depends partly on the size of the system. They therefore need to be removed on a schedule determined by the number of deliveries and the proportion of the store space occupied by the dregs. A multiple of five is a compromise that was judged appropriate to apply equally to customers' stores and to suppliers' hoppers, on the basis that the rule is aiming to manage the same effect - particle-size segregation leading to the build-up of fines at the bottom of a hopper.

The UK rule is based on the rule of thumb that used to be applied in Germany. But the Germans themselves abandoned this rule when putting together version 3 of the ENplus Handbook, and went for the simpler but irrational rule in the international Handbook.

Thorough screening

The device shall be constructed to reduce the share of fines from 10 w-% to below 1 w-% in day-to-day-operations.

The UK rules are missing "from 10 w-%". "w-%" means "as a percentage by weight".

This is another case where both versions of the Handbook are imperfect. The UK objected to the inclusion of "from 10 w-%" because this ignored the possibility that the wood pellets might have been screened before delivery to the depot. If the pellets always arrive at the depot with less than 1% fines because they are pre-screened, it is a waste of money to require a high capacity screen at the depot. A more modest screen that can screen from (say) 2% to < 1% is adequate for this purpose.

Moreover, it is hard to define "in day-to-day operations". A screen's capacity is a trade-off between the product flow-rate and the thoroughness of the screening. Most screens could reduce the fines from 10% to 1% if the product is throttled to a low enough flow-rate. Who is to say whether a product flow-rate of (say) 10 tonnes per hour could be adequate for day-to-day operations? It depends how much product needs to be loaded out on any particular day.

However, this sensible dispensation in the UK rules has been abused by most operators. It should not absolve operators of having a high-capacity screen somewhere in the chain. A low-capacity screen for loading out is only appropriate where the wood pellets have already been pre-screened.

That is particularly true of imported wood pellets. Screens of a modest capacity may be adequate at a factory, because the proportion of fines that needs to be removed is likely to be only one or two percent. But imported wood pellets have been handled multiple times. Each handling stresses the pellets and produces more fines. It is common for imported wood pellets to contain 5% or more fines. If they are loaded out over a low-capacity screen, either the screen must be run very slow or the pellets will not be adequately screened.

Yet most operators have installed low-capacity screens at the import stores, and most of the loads collected from there are delivered direct to customers without further screening.

They could get away with it if they slowed the screen down to a rate where the fines can be removed, but that might mean taking an hour to load a truck. The cost of the truck, driver and store depend on using them to deliver as much volume as possible, so operators want the trucks loaded as quickly as possible in short succession. They cannot afford to load out with their low-capacity screens at a rate that would ensure that clean wood pellets are loaded from a stockpile of imported pellets with high fines.

They should be caught out by high fines in the reference samples taken at the time of loading, but ENplus permits (although it advises against) a sampling methodology that is likely to produce a misleadingly-low fines-content in the sample. We have explained all of this in more detail in our page on Minimising Dust.

Forever Fuels only collects from stores or factories with sufficiently high-capacity screens to load out at a reasonable rate whilst removing the fines from the wood pellets that are distributed from there (i.e. high-capacity screens where there is a risk of high fines, or lower-capacity screens where the risk of high fines is minimal, such as at the factories). Our own screens for the import stores can reduce the fines from 5% to < 1% at a product flow-rate of 90 tonnes per hour.

Frequency of cleaning the supplier's hopper

If there is a buffer after the screen, it must be completely discharged at an interval determined by multiplying the capacity of the buffer by 5.

The international rules say "If there is a hopper it shall be completely discharged at least once for every 10 times the hopper’s volume has been used. Where the hopper’s capacity is bigger than 20 metric tonnes it shall be completely discharged every 200 tonnes." 

The purpose of this rule is to avoid the accumulation of fines in the hopper after the screen, which would risk fines levels of more than 1% being loaded on the truck, even if the fines had been reduced to less than 1% by the screen.

One could argue that the 1% fines limit at loading makes this rules redundant. It doesn't matter how the operator achieves that level so long as they achieve it. But experience and theory tell us that removing the fines regularly is essential to achieving this objective, just as it is essential to avoid the accumulation of fines in a customer's store. What's sauce for the goose is sauce for the gander. So it is no harm to mandate a rule that good practice requires anyway.

This is another case where the UK rules are more sensible than the international rules. Under the international rules, a 20-tonne hopper would only need to be completely discharged every 10th load. In all likelihood, the fines will be pretty high by then. But a 200-tonne hopper would have to be fully discharged every time it is loaded, and a 500-tonne hopper could apparently never be filled more than 40%! This is an irrational rule. It is a mystery why it was retained for the international rulebook when we had brought this issue to the Germans' attention, other than that the Germans could not conceive of a buffer larger than a few tonnes.

The UK rule recognises that the hopper needs to be flushed at roughly the same frequency as a customer's store needs to be cleaned, because the actions are addressing the same problem - particle-size segregation leading to build-ups of fines on the floor of the silo. A multiple of 5 is not scientific. It is just a compromise that allowed for sensibly-sized end-users' stores to be cleaned no more than once a year, and suppliers' hoppers to be emptied at a manageable frequency. We have been operating to this rule for some time now, and have found that it works to ensure that we do not exceed the 1% fines limit when loading out of our depots (which are effectively big buffers).


In yet other respects, the international and UK versions of the ENplus Handbook are identical and equally inadequate, either because the rules were watered down in version 3, or because ENplus was always inadequate on that point. For example:

Visual Inspection

Version 2 of the Handbook stated:

The delivery driver has to perform a visual inspection of the quality of the wood pellets during the loading process. 

This requirement has disappeared from version 3. The visual inspection is an important point in the supply chain at which issues such as contamination or over-length wood pellets may be spotted. Nothing has been put in place instead of this requirement that would provide an alternative way of spotting these kinds of issues.

Visual inspection is far from perfect. You cannot inspect every pellet. But checking what you can see is better than not checking at all. Some issues are identified, and eliminating whatever problems you can is better than letting everything past.

Visual inspection is more difficult than you might imagine. Tankers may have walkways, but it is questionable whether the collapsible safety barriers meet the requirements of the Working at Heights regulations. Tippers have no walkway - just a ladder at one end of the body, from which the pellets at one end of the truck can be observed.

To carry out a thorough and safe visual inspection, a platform or gantry is required. But that is more cost, and most operators do not want to incur the cost. The removal of this requirement in version 3 of the ENplus Handbook may be a recognition that so many operators were flouting the requirement in version 2 that it was unenforceable. Certainly, that was the case in the UK, where Forever Fuels is unusual for including a gantry or platform at each of its sites.

Sampling methodology

The Handbooks state:

Reference samples shall be taken during the loading process, preferably from falling material. 

The "preferably" is key. If the objective is genuinely representative samples, it should be a requirement to collect the samples from falling material.

The alternative technique permitted by the various international standards as well as ENplus is to take scoops from the loading-out conveyor belt. See our page on Minimising Dust for why this is inadequate.

Only by taking the increments for the sample from falling material can one be sure that the result is not being skewed by the methodology.

Once again, an inferior option is permitted by ENplus because the correct option is more expensive. No investment is required for someone to stand by a conveyor belt and scoop nine increments into a sample bag. To collect samples from falling material, sampling apparatus is required. The falling material is at the head of the conveyor, so a platform is required to access the sampling apparatus. Many operators did not want this cost, and the European Pellet Council and their national counterparts wanted as many ENplus-accredited organisations as possible, so rules were implemented that would not deter members. That is an unfortunate incentive for a scheme that is supposed to ensure high standards.

Forever Fuels takes its samples from falling material to ensure that its reference samples are representative.

Magnet

At no point has ENplus ever mentioned the possibility of including a magnet on the loading-out line, to capture any ferric contamination.

Where the wood pellets travel direct from the factory to the customer, this is perhaps understandable, partly because many factories include magnets in their production line anyway, and partly because there are few opportunities for contamination with metal objects in a short supply chain (although we once had a paint-tin lid loaded into one of our trucks at a factory).

But where wood pellets have travelled over several stages of handling, the risks of metal contamination are not insignificant. And the consequences of metal contamination on a customer's system can be severe.

  • Bulkers used for transporting wood pellets from the factory to the port, or from the port to the depot, are not normally used exclusively for wood pellets (Forever Fuels' bulkers are an exception). Their previous load may have included metals, and stray items may occasionally get left in the body, however rigorously the driver tries to clean it (for instance, something may be left on the lip of the body or be caught up in the sheet).
  • Ships' holds are steel, under intensive use with high risks of impact (e.g. contact with the grab when loading and discharging) and exposed to corrosive conditions (i.e. a salty atmosphere) by their very nature. With the best will in the world, it is impossible to prevent corroded flakes of metal from getting into the product in the hold occasionally.
  • The equipment that operates around a shed (e.g. front-loaders, screens and conveyors) consists of many steel parts. From time to time, something will be shed from one of those parts and may end up in the stockpile.

It is not difficult to suspend a magnet above a loading-out conveyor. We have installed magnets at all our sites, and experience has shown that they are required - metal fragments are captured regularly. But a magnet is another cost that operators do not want. They are not included on the most common handling system used at our competitors' sites. We are not aware of many sites besides ours that include them. ENplus does not require them.

Durability

Durability is a measure of wood pellets' propensity to disintegrate into fines (fragments smaller than 3.15mm). The test is to put screened pellets (i.e. with no fines) into a tumbling box for 5 minutes and then screen them again and see what proportion of fines has been generated. If the proportion is 2%, the durability is 98%. So a high durability implies a likelihood that the wood pellets will disintegrate less in handling.

It is no more than a likelihood. Forever Fuels sponsored a PhD student (Murtala Abdulmumini) at the Wolfson Centre for Bulk Solids Handling Technology, who studied the relationship between durability and actual degradation. The relationship was found to be unreliable. The durability test does not replicate the stresses encountered during delivery. It consists of many gentle impacts, whereas wood pellets experience several much harder impacts during delivery. Murtala developed a test that more accurately replicated the stresses during delivery, which gave (not surprisingly) a more accurate indication of a sample's propensity to disintegrate during a delivery. However, this has not been adopted by any standards body, and the standard durability test remains the best (if imperfect) indicator that we have.

The original durability limit for ENplus A1 wood pellets was 97.5%, but this was increased to 98% for the version 3 Handbook. The Germans pushed for even higher - 98.5% - but the UK voted for the 98% compromise, for good reasons. However, those reasons do not imply that 98% is always good enough.

The ENplus specification tries to be a one-size-fits-all spec for all circumstances. The reality is that the durability required depends very much on the number of stages of handling, and the harshness of that handling.

Where wood pellets are delivered direct from the factory by pressurised tanker, or for bagged pellets, 98% durability is more than good enough.

Where wood pellets are hauled from the factory to the port, tipped in a shed, loaded out of the shed and onto a ship, discharged from the ship onto a bulker, tipped in another shed, loaded out of that shed, and then blown into a customer's store by a tipper-blower, wood pellets with 98% durability will be badly-degraded by the time they reach the customer's store. Even if they do not have more than 4% fines, they will consist of mostly very small fragments (see Size Distribution below), which will have operational implications for the customer's fuel-handling and heating system.

The ENplus standard makes no attempt to differentiate between supply chains. It should probably specify a limit of 98.5% where wood pellets are handled more than twice between the factory and the customer. And it should probably include a size-distribution parameter (see below) for the delivered wood pellets, (a) because that is the most important factor to the end-user's experience and (b) because that would put the onus on distributors to consider how their combination of durability, handling stages, handling equipment, etc. affects the end-result for the user.

Forever Fuels has required higher durability than 98% in our main import contracts.

Size distribution

See our page on Size for the failings in the standards with regard to the size parameters. The maximum length parameter (0% > 45mm) is impractical. Because the minimum length is so short (3.15mm) and there is no size-distribution parameter, a load consisting entirely of 3.5mm fragments would be considered a valid load of A1-grade wood pellets by ENplus.

The ENplus accreditation scheme, and EN and ISO standards have been described as standards written by people who do not understand standards.


The weaknesses of the standard are exacerbated by the inadequacies of enforcement. The Handbook provides for infrequent routine inspections, and extraordinary inspections at the discretion of the UKPC if significant complaints are received.

On-site inspections only occur every three years (other than for bagging plants). In the intervening years, only "remote inspections" are conducted. You might think that "remote inspection" is an oxymoron. The use of the term is reflective of a mindset that regards checking paperwork as somehow a meaningful test of whether a company is acting properly in real life.

The routine inspections are unlikely to catch malpractice. Suppliers know they are coming (in fact, they organise and contract for them). They will take care to follow the rules on that date. It proves nothing about whether they will always do so.

Despite that, several organisations failed to organise their initial inspection for a year after they were accredited. They remained listed as accredited for that period.

The Listed Inspectors who carry out the inspections no doubt intend to do so diligently. But they may lack the expertise to spot where they are being misled. We have witnessed important infractions of the ENplus rules at sites that have passed their inspections.

Unscheduled inspections are more important than the scheduled inspections, to test how suppliers are operating when they do not expect an inspection. But the circumstances in which they may be triggered, according to the ENplus rules, are not often related to genuine non-compliances with the ENplus rules.

Complaints are unlikely to be received about non-compliance with most of the ENplus rules, because they are neither visible to nor understood by most end-users. End-users are concerned only with problems that they or their installer attribute to the fuel. Typically, this relates to the accumulation of fines through particle-size segregation, which users and installers discover when they experience problems with the boiler, and conclude (through lack of knowledge of bulk solids handling) must indicate that "dusty pellets" were delivered.


ENplus is about the chain from the forest to the boiler. The customer's installation is part of that chain, and a key factor in whether the user's experience will be positive. The fuel-supply cannot be seen in isolation from the equipment that handles and uses the fuel.

Yet they have been treated as largely separate by the UK authorities. There is a separate accreditation scheme for biomass boilers and their installers: the Microgeneration Certification Scheme. MCS is largely a rubber-stamping exercise. There is no accreditation scheme for larger boilers. MCS has nothing useful to say on fuel-storage and -handling. Pellet-users of all sizes will find that there are no meaningful standards governing their fuel-store and fuel-feed system. 

When a customer experiences a problem, they can often find themselves in limbo between an installer blaming the fuel and a fuel-supplier blaming the installation. The blame often lies mainly in the area in between - the fuel-storage and -handling systems (90% of which are not fit for purpose in the UK) and the way they are operated (e.g. cleaned out regularly, or not).

To try to address this, the EPC introduced Storage Guidelines alongside version 3 of the Handbook. These were a lightly-modified version of a Storage Guide that had been available for years, stemming originally from Germany, then translated into English by a Dane for the Irish forest-products industry, and then published in the UK by the UKPC. It has been roundly ignored by British installers for the many years that it has existed, as they have resisted all attempts to educate them on the subject of bulk-solids handling.

In version 3 of the ENplus Handbook, the EPC's Storage Guideline is directly referenced for the first time. Pellet-users will only be eligible for the ENplus guarantees on the delivered quality of their wood pellets if their system complies with the Storage Guidelines.

Several requirements in the ENplus Handbook on fuel-suppliers assume that the fuel-store has been designed in accordance with the Storage Guidelines. In particular, a functional access hatch is required for several of the important measures that a fuel-supplier should take in order to ensure a good outcome. Yet most pellet stores in the UK do not include a functioning access hatch (i.e. one that can be opened easily for internal inspection regardless of whether the fuel store is full or empty). Quite often, there is no access to the boiler or store, just to the connectors for the permanent pipes.

Besides the requirement (discussed above) for the cleaning of the end-user's store, ENplus requires the delivery driver to record:

  • Status of the storage room with obvious defects, e.g. missing impact mats, unfavourable pipe angles, and missing ventilation.

  • Amount of residual pellets in the store. 

  • Conditions of delivery, e.g. length of pipe.

  • Boiler status (on/off) 

And "the customer (or their representative) must sign the delivery documentation for confirmation".

In most deliveries, some or all of this is not possible because of the installation and/or the customer's absence.

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