Air quality in the UK is a massively important issue, with pollutants such as oxides of nitrogen (NOx), known to be hazardous to health and particularly a problem in urban areas. Data centers, even those located within urban areas, make a negligible contribution to the overall levels of pollutants like NOx but certainly have the potential to.

This potential is directly linked to the significant amount of standby diesel generating capacity required should there be a failure of the grid/distribution network operator (DNO) power supply.

This WBPS press release looks at the impact of the Industrial Emissions Directive and Medium Combustion Plant Directive on Data Centre emissions.

The Industrial Emissions Directive 2010 (IED) is an EU directive that aims to control pollution from a wide range of industrial emissions of air pollutants, discharges of wastewater, and generation of waste which includes emissions from standby generators, but it is poorly designed for standby generators particularly when they are installed in large data centers.

As a result, it is itself disproportionately burdensome for operators to comply with, particularly when combined with the requirements of other legislation such as the Medium Combustion Plant Directive (MCPD), The Clean Air Act, other regional or local requirements e.g. ULEZ, etc.

The Environment Agency is rightly insisting that operators meet the requirements of these directives. Particularly those relating to NOx emissions which can be the costliest to implement but not always as effective as believed.

What is a data center?

A data center is a highly resilient facility that forms part of a global network of such facilities. Data centers are places that underpin our modern digital economy by processing, storing, and transacting digital data and when combined with communications networks, form our core digital infrastructure.

As well as underpinning all “online” activity, data centers enable the day-to-day use of social media platforms, the general public, retailers and banks to process financial transactions, supermarkets to resupply, delivery companies to manage logistics, and public authorities to deliver services and messaging. Some sites are officially deemed Critical National Infrastructure (CNI) so that they reflect the nature of the type of activity being managed within.

Why are standby generators needed?

Data centers are large users of electrical power, so the primary reason standby generators are included is to provide backup power in the event of a prolonged power utility failure. This utility failure can be anything from just a few seconds to hours or possibly days. Some sites do have a secondary mains supply, but diesel generators are the “go-to” solution because they are able to provide the largest amount of power in the shortest time, and diesel fuel can be safely stored on site.

Emissions from a diesel-powered internal combustion engine are multifaceted and as such, there isn’t any one single solution. Over the last 20 years, there’s been a significant push to reduce levels of CO2 with this global objective framing both international and local legislation.

Whilst reducing CO2 remains an ongoing challenge other elements present in the exhaust line have been of concern for many years and this too has been driving the industry to respond with innovations and targeted responses.

The diesel engine and generating set manufacturers have worked to develop engines that comply with new regulations and as a result, there have been significant advances made in the reduction of Particulate Matter (PM) Hydrocarbon (HC/soot), etc the adoption of common rail fuel induction systems and manufacturing engines to much tighter tolerances which significantly reduce heavier lubrication oil seeping past the piston rings. With older installations and engines of an older design, these issues will continue to be a problem until they are replaced.

Which regulations cause the problem?

The Industrial Emissions Directive (IED) speaks directly to installations having a thermal input of 50MWth and above and includes a standby plant. There are already a good number of “hyperscale” data centers in the UK that have sufficient on-site standby generating capacity such that they require IED permits. With the current trend towards fewer, larger facilities, more operators are likely to find themselves needing to comply with this regulation.

Awareness is growing but still patchy, mainly because IED wasn’t widely consulted over in the data center world, it seems to be being implemented differently in different EU nation-states, (and from jurisdiction to jurisdiction within the UK) the legislation has been poorly communicated to interested parties and the government guidance that is available is extremely difficult to interpret.

What is IED all about?

IED is one of a number of regulatory requirements targeted at reducing/ controlling pollution. IED is an EU Directive and as such is implemented through domestic legislation in the UK; in this case the Environmental Permitting Regulations or EPR. Its requirements are wide-ranging and aim to set controls on all forms of emissions to air, water, and ground. It is an air quality element that impacts data center operations. Standby diesel generator exhaust gases are complex and include CO, CO2, oxides of nitrogen, sulfur, soot, and particulate matter.

Why is IED difficult?

Data centers and in particular the “hyperscale” data centers all have a large amount of standby capacity which is used infrequently. The low level of usage presents a number of challenges for operators that require IED permitting. To demonstrate all systems are working correctly the generating set is run regularly for testing and maintenance. This testing, which is often for relatively short periods (30 minutes), can often be undertaken with no or very low levels of load. This well-established practice has traditionally been done to keep fuel consumption and hence CO2 emissions to a minimum.

Running at low levels of load means that the SCRs fitted to reduce NOx never reach their optimal operating temperature and hence do not function. For many years government policy was to strive forever (and still is) to lower emissions of CO2 which takes you in the direction of higher efficiency/low fuel consumption engines. IED then poses a challenge for generator manufacturers and data center operators because it represents a change in the direction of government policy.

For many years manufacturers have been focused on improving fuel efficiency to reduce carbon impacts associated with Scope 1 emissions from plants. This new policy now requires manufacturers to supply generators on the basis of their air quality performance and the regulator is seeking to impose a two-gram limit for NOx, a major pollutant. This is something of a “cake and eat it” moment where there needs to be a trade-off between fuel efficiency, and lower CO2 emissions and air quality, in this case NOx.

It is important to note that the Environment Agency has taken something of a pragmatic approach when permitting older installations which are only part way through their life cycle with plants yet not requiring replacement.

How can emissions be further reduced?

Organizations that are looking to reduce emissions further are often turning to Hydrotreated Vegetable Oil (HVO). HVO is a paraffinic drop-in diesel fuel substitute that provides a cleaner alternative to power standby diesel generators, as well as other diesel-powered machinery.

Conforming to EN15940 standards, HVO is manufactured from many kinds of vegetable oils, such as rapeseed, sunflower, soybean, and palm oil.

Some or all of these sources can be from waste products such as used frying oils or animal fats hence, they can be made from entirely renewable energy sources that do not impact crop resources.

The adoption of HVO (EN 15940) could translate into a widely claimed maximum 90 percent reduction in CO2 emissions over its entire lifecycle. There is currently no conclusive evidence that the use of HVO has any significant impact on the levels of NOx produced by the generating set.

Some designers and operators have looked to gas as an alternative as it is cleaner in emissions and particulates than diesel. However, on-site storage is a space and safety problem, with having a local source of sufficient capacity and reliability another.

Gas, having a lower calorific value than diesel, means the engine swept volume must increase to deliver the same power, meaning higher initial capital costs. Starting a gas engine can take much longer and the set is much slower at accepting site loads. Those issues, combined with higher maintenance costs, have ensured gas generation is very rarely adopted.

Many of the larger manufacturers are currently working on a hydrogen fuel solution, running test programs to assess long-term reliability issues. This option looks to offer a promising future but there is some way to go with work still to be done to provide a truly “green” source of hydrogen fuel, workable local safe storage and distribution methods. In the long term, the data center sector (and others) will need to transition away from diesel plants, but at the moment these potential alternative solutions are still at the trial stage. In the short to medium term diesel generators remain the default solution for ensuring resilience and business continuity.

Data center operators along with the supply chain take meeting their responsibilities to minimize air quality impacts seriously. The need to minimize NOx emissions is clear, and meeting the obligations is being committed to organizations investing in appropriate solutions. With growth continuing in the sector more sites will need to comply with IED requirements in the future.

The IED legislation as currently enacted is not wholly appropriate for the data center market as it imposes a regulatory burden disproportionate to the outcomes achieved. This isn’t particularly a failure of the legislation itself but more that the regulations haven’t kept up to date with market developments and particularly the rapid growth in large and hyperscale data centers.

The legislation therefore urgently requires a more bespoke approach to minimize and mitigate data center air quality impacts. There is no need to compromise on either the requirements or ambition, but it is essential that the requirements are proportionate and above all deliver meaningful outcomes.

For further information, please email Robb Shingles at [email protected]