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

Summary

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.