Part 3 of building a carbon neutral distillery – meeting the energy challenge.

Steam from biomass – making it work

Biomass – the practicalities

Many have tried to run a distillery from a biomass boiler; some have struggled; and a few have failed, given up and gone home… but others have succeeded, and the industry has learnt from all of these examples – good and bad. 

The overriding priority when considering biomass for a distillery is to make sure it’s done safely. Distillery operators are expert in managing the hazards they are familiar with, including those associated with oil and gas fuelling, but biomass presents different hazards – often unfamiliar to distillers. Seeking expert support in the design, commissioning and operation of the boiler system is therefore essential.

The introduction of the RHI tempted lots of people into the sector – not all of them expert in the hazards or practicalities of biomass boiler systems. The flood of installations in the following years led to a significant number of installations which were not up to standard, including some dangerous examples. This resulted in some newsworthy accidents and tarnished the reputation of the sector as a whole. The cowboys who dominated the sector at its peak have mostly left town, but they left behind a legacy of poorly designed and under-performing biomass systems.

However, this shouldn’t be viewed as a failing on the part of biomass as a low carbon technology, but the result of an incentive scheme which was as poorly designed as some of the installations it triggered. Most of the companies still in the biomass sector know and understand the hazards, and how a project should be designed and implemented safely. The Combustion Engineering Association’s BG05 “Guidance on the Design and Operation of Biomass Systems” is a great place to get an appreciation of the types of hazards I refer to here.

As well as a safe boiler, distillers want a boiler that works in their application, and without applying specific knowledge, there are some well-known ways a biomass boiler can struggle in distillery service.

Offsite fabrication of a biomass steam boiler plant

Timing is everything

As anyone who’s sat round a campfire knows, there’s a delay between putting a log on the fire and feeling the benefit of it. It’s a characteristic of all solid fuels, and this delay certainly isn’t ideal in a distillery application – when the operator asks for steam to the still, he means now, not in 20 minutes. There is a similar problem when the still run is complete – the fuel on the grate continues to burn, and the heat may be wasted if the distillery doesn’t need it at that specific moment. 

In an attempt to cater for distilleries’ notoriously “peaky” steam demand, many biomass boilers have been fitted in parallel (duty/assist) with the existing fossil fired boiler. Typically, the design intent was for the biomass boiler to provide the base load, leaving the fossil fuelled boiler to pick up the peaks in demand. However, the limited turndown capacity of boilers can mean that the fossil boiler spends a lot of time on minimum fire, taking a large part of the distillery’s demand, reducing the fossil fuel displacement and actually leaving the peaks to be taken up either by the biomass system or by the fossil boiler cycling on and off. Neither is ideal.

In partnership with engineers in continental Europe who have been designing biomass systems for over 50 years, re:heat have implemented and proven a number of techniques for controlling the fire in the furnace and the boiler pressure to iron-out the mismatch between steam supply and demand. This means the peaks and troughs which are common in distillery applications can be met by a single biomass boiler – without the need for backup plant.

When foul isn’t fair

Gas boilers hardly ever need cleaning, oil boilers maybe once a year. Biomass boilers which are not properly controlled can need much more frequent cleaning due to build-up of tar or soot in the furnace or boiler, particularly when they are burning “difficult” fuels such as wet woodchip or draff.

Furred boiler tubes from running a dry wood boiler on wet fuel

If a “difficult” fuel is readily available at a low cost, then regular cleaning may be justifiable, but in a well-designed biomass boiler system, cleaning twice a year is adequate for most industrial users.

A low carbon footprint can come with a big actual footprint…

It’s an inescapable fact that a biomass store is bigger than an oil tank or a gas governor. If your site is tight, then it might be a struggle to fit a biomass system onto it, but there are usually approaches which can be adopted to manage this. For example, it may be that the fuel supply chain could be tweaked to minimise on-site storage space requirement, or it might be an application for a pellet fired boiler. Certified sustainable pellets are widely available from manufacturers in the UK, which will keep your environmental credentials intact.

It sounds obvious, but a good fuel supply is crucial to successful operation of a biomass boiler. Less obvious is that the fuel supply should be planned out well before the boiler is operational. The biomass fuel supply chain can be daunting to those unfamiliar with it, but don’t worry – there are plenty of people out there who can make it work for you. It doesn’t need to be any more difficult than buying oil, but there are some bear traps to avoid and forward planning will save stress, time and cost.

Biomass boiler plant room under construction, Brora Distillery, October 2020


There’s no getting away from the fact that distilling is an energy intensive process, and that up to 90% of all the energy used in a distillery can be in the form of steam and heat. You can certainly reduce the energy demand by implementing heat recovery strategies, but there is always going to be a need for heat input. No single heat supply solution is the right one for every application, and no single solution can provide for the whole industry. 

It’s clear, however, that biomass-fired boilers are one of the most technically and economically viable options currently available, and in many cases the only low carbon option which is likely to work for a distillery. Properly designed systems which use high quality equipment and proven technology can be the beating heart of a distillery, and with a realistic lifespan of 25 years or more on the right boiler, it’s important to get it right.

re:heat’s senior team includes forestry, biomass boiler and distillery engineering professionals, meaning we’re ideally placed to assess or implement a biomass-fired solution for your distillery, or to advise on any aspect of the project lifecycle through our consultancy arm. So, if you’re still burning dinosaurs to make whisky, then call us – we can help.

Building a carbon neutral distillery… meeting the energy challenge.

Our Principal Engineer, Andrew McGhee applies his 25 years of energy sector and distillery engineering experience to look at some of the answers.

We all know that emissions of CO2 have to be greatly reduced over the next very few years, and that distillers everywhere are working hard on how to achieve this.  The latest Environmental Strategy Report from the Scotch Whisky Association shows the distilling industry leading the charge, reporting that the 2020 target for reducing fossil fuel use has been smashed, with 28% of primary energy now coming from non-fossil fuels.

But there’s no getting away from the fact that distilling is an energy intensive process, so what is the beleaguered energy or environment manager to do?  The good news is that there are lots of options out there.  That’s also the bad news – because no single one of these options is “the best” in every situation.  So there’s a need for careful assessment (by that beleaguered energy manager) on a case-by-case basis.  We at re:heat – biomass installers and low carbon heat consultants – believe that there is a place for all of the options; that no individual option can do it all. If anyone tells you that that theirs is the best solution in every case, then you’re clearly talking to a salesman – not an engineer or sustainable energy professional.

Maximising energy efficiency across every stage of a process should be a given. Your insulation should be good, your steam leaks should be eliminated, and waste heat should be recovered and beneficially reused wherever practicable.  Apart from that, there are dozens of ways of reducing energy use, from the cheap & simple to the hugely complex and expensive.  Which ones are justified (or justifiable) on any particular site depends on the size of the site and the price of your energy, amongst other things.  But one universal truth is that however much you work on energy efficiency improvement, you’re still going to need a source of energy which is as close to zero carbon as possible.

So, what are the main options for carbon neutral heat?

Electrification.  It’s perfectly possible to generate heat from electricity – either directly or by using a heat pump.  Electrical heat is clean and easy – we use it every time we make a cup of tea or coffee.  Some will tell you it’s 100% efficient, but of course that is misleading.  The main problems with electrical heat are that it’s expensive, and the UK’s power grid simply can’t support generation and distribution on the scale required to fully decarbonise our heat, not to mention our transport.

The price problem can be reduced with high temperature (steam raising) heat pumps, however, they’re not widely used or proven yet in industrial applications.  Also, to qualify for RHI support, heat pumps can only use air or ground source – not waste process heat, and air/ground source high temperature heat pumps have low coefficients of performance due to the high temperature uplift required.

The other broader problem with the electrification of heat is a looming power generation squeeze in the UK.  Six of the UK’s 7 existing nuclear power stations and all of the coal fired stations are expected to shut down within the next 10 years, although there should be a new nuclear plant coming online soon – Hinkley C in Somerset, which is projected to begin providing power to the grid in around 2026, and will provide around 7% of the UK’s electricity needs.  But with the UK’s current nuclear fleet providing around 20%, you can see the problem.  Add to that an increasing demand from the electrification of transport, and the power squeeze is apparent.

Increased renewable generation – especially offshore wind – will fill some of the gap, but it’s doubtful whether the grid (generation or distribution) can support the widespread deployment of heat electrification without huge infrastructure investment.  Electrification of heat could be viable if you can generate power locally – tidal power on Islay or Scapa Flow for example, but these sorts of options are limited in scope and scale.  So, there is a place for some electrification of heat, but it is by no means the panacea for the 2020’s that some claim.

Hydrogen. Great fuel, zero emissions – what’s not to like?  Well, there is currently nowhere near enough of it to go round!  You can make it from water and electricity, but the poor energy conversion efficiency means you would be better off just using the electricity directly.  Really, hydrogen is an energy storage medium – not an energy source.  It’s also very expensive at the moment.  

As the hydrogen market develops over the next few years, supply will increase and prices will drop, but it’s probably a decade or more away from helping that poor energy manager, and the UK government has big ambitions for using hydrogen in the existing fossil gas grid.  The hydrogen industry needs support because it’s certainly a part of the future energy mix, but it’s not ready to help many people with 2030 emissions targets to meet, particularly if they’re off the gas grid.

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Biomass. People have been burning wood for thousands of years to raise heat, and in 2020 it still constitutes the world’s largest non-fossil source of energy.  It’s renewable, the technology is proven, there’s an established supply chain, and you can have a system up and running in a year.

As this opinion is coming from a biomass company, you’d expect us to claim that it’s the answer to everything, right?  Well, no, we don’t think it’s for everyone.  Again, there’s not enough wood available at present to cater for the entire distilling sector, and you really want to be in an area with an established forestry and wood products industry, because wood fuel is bulky. We wouldn’t recommend it in Shetland for example, but there’s no escaping the fact that wood is without doubt one of the most cost-effective emission reduction strategies which can be implemented at scale now. We’ll come to the debate about whether using wood is really helping lower CO2 emissions in part 2.

Biogas / bio-propane.  Both natural gas and LPG (propane) can be manufactured from biogenic origins, so that the CO2 released on combustion has previously been drawn from the atmosphere by plants. Both are chemically identical to their fossil equivalents, but again (are you getting the pattern yet?) there is not enough of either material available to satisfy the needs of the whole distilling industry.

Vegetable oils can also displace fuel oil in boilers for steam generation.  Some oils are cost competitive with fossil oil and proven in industrial application.  They do have one or two operational problems, but nothing that can’t be overcome.  However, the supply of vegetable fuels oil is very limited, and heat users will have to compete with the transport sector for the available resource.

Geothermal energy.  The deeper you drill, the hotter it gets.  Unfortunately, to get steam you have to go really deep, and the upfront capital cost gets quite daunting.  If you have a distillery in Iceland or Turkey, you probably know about this already, but there are a few areas in the UK with real geothermal potential. Worth checking out, but entirely dependent on local geology.

Biogenic carbon capture. For every 100 tonnes of CO2 which goes up the chimney from the boiler, over 30 tonnes is vented cold and pure from the fermentation process. That cold pure CO2 is ideal for re-use or sequestration.  You have to be careful where that CO2 goes, but with geological sequestration projects alive and kicking in the UK, there is potential there. Unfortunately, it’s probably too far out for your 2030 targets, but do I dare suggest that whisky production could viably have negative emissions in the future by making use of this mechanism?

Alternative raw materials.  Pea gin anyone?  A tip of the hat to Arbikie Distillery in Angus, but this is probably not able to be rolled out on a large scale – and definitely not in the making of scotch whisky!

The main point here is that there isn’t enough of any one of these resources to supply all of Scotland’s distilleries.  Most or all of these solutions are required if the industry – and not just individual distilleries – is to achieve carbon neutrality.

re:heat offer biomass solutions which are widely deployed and well proven in the distilling sector, so that’s what we’ll focus on in part 2 of this post, coming soon.

Email to find out more about carbon neutral distilling and the solutions on offer.