Looking after the environment is vital if our species is to have a future on Earth. It’s also important for modern businesses to avoid prosecution for breaching environmental regulations, whilst showing shareholders and the public how they’re caring for the planet.

Regardless of the driving force behind your company’s environmental policy, you need to take measures to meet and/or exceed the demands of environmental legislation. Your environmental protection plan also needs to match your budget, and create an environment where you can keep abreast of changing legislation.

We’ll look at the typical environmental protection (EP) requirements of an Irish data centre, though these ideas and regulations will also apply to many other industries that use back-up generators in some capacity. Facilities managers for hospitals, food storage facilities, laboratories, and more will also find these guidelines useful.

We’ll also take a look at how you can keep your emissions as low as possible to help you keep shareholders and the public happy. Minimizing emissions can also help you stay ahead of new emissions regulations as they come into force.

Noise and Other Non-Emissions Regulations

Before you figure out which rules and regulations you need to follow, you’ll need to take a look at where your facilities are located, and where within these facilities your generators are placed. Environmental pollution isn’t limited to emissions from burning fuel, you need to be aware of noise pollution levels, and in some cases even levels of heat emission.

You’ll need to (in Ireland contact the relevant agglomeration for your area to find out what noise levels are suitable for your installation, remembering that emergency power can be required at any time of the day or night. Usually noise-reducing housing will resolve noise pollution issues, and since you can’t predict when emergencies will occur it’s a must in many cases.

You may also need various other licences dealing with transfer and recovery operations, minor air and heat emissions, or discharge of waste (such as condensate from cooling systems). Most data centres won’t need much in the way of additional licensing, but other industries may need quite a selection of different minor licenses.

Which Emissions Regulations Apply to You, and Which Licences do You Need?

The main source of emissions for any standby generator system is going to be from the combustion of fuel. The EU legislation most likely to cover mid-sized combustion plant emergency power systems is the EU (Medium Combustion Plants) Regulations 2017. These regulations combustion plant used for any purpose that has a thermal rated input between 1 MWth and 50 MWth.

If your backup generators go over 50 MW thermal input and they operate for more than 18 hours per year, you will need an Industrial Emissions Directive License. IED license applications are complex, and expensive to prepare. IED rules will apply to larger data centres and other large capacity backup power arrays.

If your generators are all over 3 MW thermal input, and the array adds up to more than 20 MW thermal input, you will also need a Greenhouse Gas Permit (GHG Permit). Commission for Regulation of Utilities and Energy (CRU) Licenses/Authorisations are required for all generators over 1MW thermal input, and those under 1MWth of power can apply for the simpler CRU “Way of Order”.

Be careful, you only count units over 3 MWth when adding your total site capacity together to see if it’s over 20 MWth, but if it does exceed 20 MWth you take into account all generators on site, regardless of their size.

You’ll also need to take notice of the Emissions Trading Scheme regulations.

As far as exemptions go, by keeping the hours per year in use under 50 hours/pa, your generator array can be exempt from much of this legislation. To be exempt, your generators must not be used for any purposes other than backup emergency power. For data centres, this means they must not be used for Triad Avoidance or Fast Frequency Response purposes.

Thermal Input What?

All of the EPA and EU emissions regulations are based on the power of the generators involved, with some regulations also affected by the number of hours per year the equipment is run for. Failing to calculate this correctly is a sure path to prosecution.

Calculating the number of hours per year your backup generators run for would seem like an easy task. It is, so long as you remember to include time spent running for testing and maintenance purposes. There are emissions exemptions for standby generators that are used for less than 50 hours per year, so if your power generation capacity is for standby only, with no load balancing or other extra functions, you may be in luck.

To calculate thermal input power for yourself, just follow these not so quick instructions from Amps. As a broad rule of thumb, generators are between 30% and 40% efficient, so you need to multiply the electrical capacity by about three to give you an idea of thermal input. One thing that’s worth taking note of is that thermal input power calculations include engine efficiency, fuel consumption, and fuel type. These can all be improved with a little forethought. Typically, a generator with 0.3 MW electrical output will have around 1 MWth thermal input power.

While having 20 0.5 MWth generators would be impractical in many cases, and would lead to increased maintenance costs, it’s useful to know about these calculations. You might be able to avoid more onerous legislation by installing five or six smaller generators rather than one or two large ones.

An array of slightly smaller generators also gives you more leeway to replace and upgrade in stages if and when the need arises. Your finance department may well thank you for this.

So, What Improvements Can Actually Affect How Regulations Are Applied?

While no improvements are going to make a 60 MWth generator into a 0.5 MWth generator, taking every possible step to reduce emissions may have an effect on which regulations apply to you. In fact, when you look at the things that reduce thermal input power of a generator, they are the same things that lead to reduced emissions:

  • Improved generator efficiency
  • Better quality fuel

So How Can I Improve Emissions from Our Back-Up Generators?

Whether or not you run your back-up generators enough hours per year to make you liable to emissions regulations, it’s important to reduce emissions as much as possible to protect the planet and reduce overall running costs. So, just what can you do to lower emissions?

Improve Efficiency

As a rule, larger capacity diesel generators are more efficient than smaller ones, so it’s often better to have a lower number of larger generators. When you design a backup generator array, it’s always better to have at least two combustion plants, to protect you should the worst occur and one of them fail during a power cut.

It’s also a little disingenuous to have a large array of smaller (sub 1 MW electrical output/ sub 3 MWth) generators to try and side-step emissions licencing regulations. A set up like this will also be around 4% less efficient than a lower number of higher-rated generators.

Generally speaking, newer, well maintained generators with engines from well-known global brands will be the most efficient, and will have the lowest emissions. They will also likely cost less in maintenance and down time over their lifetime.

Fuel Quality

Fuel quality is a big issue when it comes to keeping emissions low. After all, emissions are a direct result of burning whatever fuel you put in.

Things like water in fuel, diesel bugs, dirt, and even air won’t just make the power output of your generators uneven. It will also make your generators less efficient, never mind the fact that these can all cause long-term damage to your equipment, reducing its predicted lifespan.

By introducing a regular fuel testing and cleaning program that includes maintenance of all filters and transfer pipes, you can avoid these problems.

Bio-diesel vs Regular Diesel?

Biofuels are often touted as the perfect solution to the world’s environmental woes. EU targets aim to have all diesel contain at least 10% biodiesel by 2020.

So, from an emissions point of view, should you switch to bio-diesel? It depends very much on the source of your biodiesel. Some biofuels are actually more polluting than old-fashioned fossil fuels, due to the resources expended in their production.

As far as actual combustion goes, many toxic emissions can be shown to be lower when using higher percentages of biodiesel. Reduced levels of NOx, CO, and CO2 have all been demonstrated. Whether or not these figures will eventually have an effect on how legislation is applied remains to be seen, but you can still be certain that your on-site emissions will be lower with biodiesel.

Storage problems are similar to normal diesel, requiring regular fuel testing and polishing. Biodiesel can be sluggish at low temperatures. As mentioned, you need to source your biodiesel carefully to be sure it isn’t costing the environment more than using normal diesel would overall.

One thing to watch out for with Biodiesel is that it can damage seals and gaskets in your storage system. This includes any mixture with 5% or more biodiesel, so pretty much all fuel these days.


Standard maintenance is one of the best ways to keep emissions to a minimum. Make sure you keep up with all planned and unplanned maintenance on all of your generators, pus the fuel storage and supply systems attached to them.


While there are a number of ways you can improve the emissions from your backup generators, if you want to get the best deal possible from the current environmental protection regulations you will need to plan the sizes of your generators carefully.

If, like many organizations with emergency standby generators, you use diesel or biodiesel as a fuel source, you need to take this into account when planning maintenance. Looking after your stored fuel and fuel delivery system, as well as the engines themselves, will reduce emissions the most. It will also save you money in the long run by making sure nothing can deteriorate due to lack of care.

To find out more about how testing and maintaining your fuel supply can help you optimise your emergency generator emissions, get in touch with our team of fuel experts today.

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