What is biomass technology and just how feasible is it for your brewery? Here Chris Lewington, the founder of Brew Resourceful, investigates both the economic, environmental and process implications involved.
I wrote an article in the last edition of the Brewers Journal on how we can decarbonise heat energy for small and medium-sized craft breweries.
It detailed why this is arguably the biggest challenge in decarbonising our industry. That came from personal experience, as I had literally just finished a mammoth project with the incredible Vault City Brewery on road mapping decarbonising their new brewery build in Penicuik, Scotland.
Without doubt, decarbonising heat was the single biggest headache I had.
I conducted over six bespoke heat decarbonising feasibility studies including an electric steam generator, heat pump, creating biogas, purchasing biogas and a biomass boiler.
In this article, I want to share with you the findings of my feasibility study on biomass. Why this technology?
Because I had the most fun doing it and many people have told me (and continue to do so) that it’s not feasible. I believe differently.
If you read my opening call-to-arms piece in this edition you will know how invested I am in sustainability not meaning environmentalism, but people, planet, and profit in equal measures.
So we will investigate both the economic, environmental and process implications. I do not promise this is the silver bullet in decarbonising heat energy, but I promise that this is fun.
An Introduction
In an incredibly well-funded world of complex thermodynamics, fluid mechanics and electrical engineering, discussing combusting fuel in a furnace feels wrong.
A biomass boiler burns organic matter such as wood, agricultural waste or brewers spent grains to generate heat, which then undergoes a process called gasification and this hot gas is passed through a heat exchanger with water which in turn creates steam.
Flue gasses and ash are controlled and disposed of/reused, importantly flue gasses have specific regulatory consent limits.
Fuel
Intrinsic to biomass boilers is the choice of biomass you burn. There are a lot of options available, some are quite frankly, horrendous and others extremely promising.
Your choice of fuel directly affects your return on investment, both economically and environmentally. The most common biomass used is wood.
For me personally, this is a challenging concept, how can burning wood for heat possibly be economically or environmentally viable? As with just about everything in life, it depends on where you source it and how it was processed.
First let’s assess the environmental impact, Rory at Treco (Biomass Boiler Manufacturer) sent me this great chart from GOV.UK, a nice visualisation of the environmental cost of burning various types of wood compared to burning gas.
I like this chart a lot, you can clearly see where and why natural gas contributes so much damage to the environment.
The combustion aspect of gas is the most significant environmental factor, but when you look at wood, it’s processing and transport.
As you can see from the chart, (aside from natural gas and light fuel oil) your choice of wood type, origin and amount of processing is intrinsic to the environmental impact.
It’s no surprise that non-UK wood types have significant transport costs associated, but more importantly, wood processing quickly starts to close the gap between wood and natural gas.
A sustainability hack for you, generally speaking, don’t just focus on the amount of miles your goods travel, focus on the way they are manufactured.
By far the best option (environmentally) is wood processing waste, there’s very minimal processing required (often just chipping) and you only need to account for the combustion and minor transport costs (depending on the location of the waste wood, usually it’s local).
Unfortunately, there just isn’t the data to compare brewers spent grain. Presumably, the processing and transport costs are close to zero, however there is good reason to believe it releases more NO2 when burnt compared to wood, so I would guess that it averages out the same kgCO2 per kWh as waste wood, potentially marginally higher.
Net Calorific Value
One incredibly important metric of fuel choice is its net calorific value, i.e. how much energy will you get by burning 1 kg of the specific fuel type?
The lower the value, the more fuel you need to burn in order to get the same amount of heat energy, the higher the less fuel you will use.
This impacts the environmental, economic and practicality of a biomass boiler. Let’s check out some Net Calorific Values (NCV) of popular fuel choices and of course our friend, brewer’s spent grain (BSG).
You can see why we have been burning natural gas for so long, it’s NCV is far greater than any organic material, meaning we need far less of it.
However, as our judgement of fuels has broadened beyond simple economic calculations, we now have to look at the rest of the organic material.
Wood pellets offer the best NCV followed by waste wood and then our friend BSG. Excitingly, the NCV of BSG here is looking very comparable.
The reason for this excitement is because if we update this table, with the cost per tonne you will see the cost is not comparable.
When conducting this for Vault City, I attributed a small £20 p/tonne cost of waste wood as there were transport costs and a modest incentive for the farmer.
Economically speaking there are two standouts: BSG and waste wood. Excitingly, this is the same as the environmental standouts.
Practicality
Now we have two standouts (waste wood and BSG) let’s assess their practicality. Waste wood is fairly straightforward, you need to be able to secure X amount of tonnes per year, at regular intervals, store it and purchase at a stable price.
It requires you to rely on either one or multiple sources which does create an additional workload for whoever is in charge of procurement.
BSG alleviates most of these concerns, however, comes with plenty of its own. First, let’s look at availability.
The key to BSG’s self-sufficiency is that you can provide enough per day in order to fuel your biomass boiler.
Ultimately, this varies heavily brewery-to-brewery as it depends on factors such as: Average plato of wort (per month/week/day/brew), Brewhouse efficiency (% and standard deviation), Number of brews per day/week and Grain composition.
If you brew a lot of low/no beers now or in the future, then BSG being your fuel of choice will likely end here.
If, like Vault City, you’re famed for your higher abv styles, you can continue down the path of feasibility. I prepared this chart for Vault City (some data has been changed when replicating this chart for this article) which you can see, estimates a deficit of BSG created vs required.
Exciting.
You also must factor in the efficiency of the biomass boiler, as that will determine the quantity needed. For this I used a recommended efficiency of 85%.
Drying
In the NCV charts above I did omit a very important aspect of the NCV for BSG, that the moisture content needs to be at 30%.
For most brewers, spent grain leaves the mash/lauter tun at ~80% moisture content (varies brewery-to-brewery).
And at this exact point, most will tell you that BSG becomes unfeasible as a fuel type. Because options to dry from 80% to 30% are compression screws, electric/gas driers or a combination of them both.
All of these require significant energy which erodes the economic saving to a point of redundancy. I calculated for Vault City, there would be 104 kWh of heat energy a day required to dry the amount of BSG required a day.
If you choose gas for this heat energy, you ruin the environmental return, if you choose electricity you ruin the economic return.
However, there is a silver bullet. A company called Stronga has invented a drying system specifically for spent grain that uses waste thermal energy from the biomass to dry the incoming BSG to the biomass boiler.
This now overcomes the former roadblock of drying as it uses little electricity to operate and can handle the quantities required.
They have an informative website, check it out here for more details (https://stronga.com/en/drying-spent-grain-with-stronga-sustainable-uses-of-brewers-grains/)
Flue Gasses and Particulate
When burning organic fuel flue gasses are released and subject to regulation. Flue gasses of both waste wood and BSG contain CO2, water vapour, particulate matter and small amounts of Nitrogen Oxides (NOx) as well as volatile organic compounds (VOCs).
A benefit of waste wood as a fuel type is its commonly used as fuel for biomass, therefore managing flue gasses is well researched and managed. Wood produces large but manageable amounts of ash which does increase the need for routine maintenance and filter checking.
Publicly available research into BSG as 100% fuel type is extremely limited, leaning toward non-existent.
The main concern is the residue left after combustion along with the heavy particulate (ash) created when burning BSG.
This is confirmed by Alaskan Brewery in the US, who operate a biomass plant that runs on BSG, they had to shut the plant down every 25 hours of operation to remove ash accumulation in the system.
Their answer was to input a ‘sonic horn’, effectively a device that uses centrifugal force to pull ash out of the flue gas, not allowing it to settle in the boiler.
They reported this increased time between maintenance from 25 to 96 hours, a huge improvement but still concerning.
I have had some experienced biomass boiler experts tell me that 100% BSG is simply not feasible due to the quantity of ash and poor burn quality, and others say it’s manageable with the right equipment. I’m sure this would make for a good debate in the Biomassers Journal or at the Biomassers Congress…
I am currently working on research with Treco, using Vault City’s BSG to evaluate the flue profile of burning this, once the research is obtained I will be sharing it to my Brew Resourceful subscriber list and potentially down the line, The Brewers Journal.
Type of Biomass Boiler
Another consideration is the type of biomass boiler you would require. There are two options, a Medium Temperature Hot Water (MTHW) or High Temperature Hot Water (HTHW) biomass boiler. The crucial difference is MTHW biomass boilers are capable of max 120c steam whereas HTHW can achieve 157c and above.
Generally, breweries use 157c for distribution which is then reduced when it reaches its destination.
The path of least resistance is, of course, to emulate what you would normally experience and opt for the HTHW biomass boiler, however, the investment cost is over double. Which for most medium-sized craft breweries will roadblock this project.
Operationally, 120c steam is usable, and it’s reasonable to implement this in a new brewery build, but it’s very difficult to retrofit into an existing steam distribution system that was designed for 157c steam.
Return on Investment
So let’s push those rather large potential road blocks to one side, and focus on why I am so keen to pursue BSG as a fuel source.
Here are the results of the ROI calculator I created for Vault City. I must stress at this point that this return on investment calculation is NOT representative of your brewery.
These are based on multiple factors that are extremely bespoke to Vault City as well as an estimation of CAPEX cost (to be fair to the supplier I did not share specific quote value).
The two major highlights from the ROI calculator are the 10-year ROIs. After the initial investment, Vault City would be £961k in the green from gas cost savings. And that over 10 years they would prevent 1,662 tonnes of CO2e from entering the atmosphere.
For context, I investigated over 30+ sustainability technologies, and in terms of return on investment both economically and environmentally, this was one of the top 3 technologies available right now that deliver that kind of ROI.
On top of that, Vault City would be entirely self-sufficient for heat energy, meaning they would be secure against any future shocks to the energy market like we saw in 2022.
And the story behind turning a waste stream into 100% of your heat demand is exceptional, which for me personally, is extremely exciting.
I’m sure you might be wondering if Vault City is going ahead with this technology, the answer is, potentially but not today. Ultimately, there were better (economic, environmental and process) options available that had less risk, and cumulatively better ROIs.
In my opinion, Vault City is in a unique position to implement this technology due to the availability of BSG, building a greenfield brewery and they genuinely care about sustainability. Which is exciting, and it does lead onto an important question.
What are the current alternatives? You could wait for heat pump technology to fall in price and increase in longevity, combine on-site electricity generation with an electric steam boiler (not viable in medium sized breweries) or simply wait for another alternative.
Or you could purchase a proven technology now, that will save you close to £1m and 1,666 tonnes CO2e over 10 years, by which time you can ‘upgrade’ to the latest modern, proven and affordable technology.
However, as you can see from this feasibility exploration, there are still major challenges to overcome, all of which will take time to investigate.
On top of this Angus Morison (Head Brewer) and Steve Smith-Hay (Co-Founder) rightfully pointed out that during a new brewery build, would you want to introduce this level of potential chaos? Absolutely not.
The Next Steps
If you made it this far, you will know that there are some very important hurdles to overcome before I could actually recommend this technology.
These include investigations into the burn profile of Vault City’s BSG and how that will affect the operation and maintenance of the biomass boiler as well as the legal consenting limits for flue gasses.
Waste wood is still a good fuel source, it lacks the self-sufficiency angle but does alleviate a lot of the BSG concerns. You can also blend the two and burn simultaneously. A local reliable source of this is intrinsic to its feasibility.
I can’t stress enough how fun this was as a feasibility study and that it is far from complete. There is a chance, this time next year I can write the final article on this, with a picture of me next to an operational biomass boiler, but there’s an equal chance we have found a better route to decarbonise Vault City’s heat energy, all I know for sure is that we will do it.
I would love to hear your thoughts and feedback, please contact me via LinkedIn or email chris@brewresourceful.com and finally a huge thank you to Vault City for allowing me to share their data, this is the exact action of collaboration I expressed in my intro piece at the start of the journal is essential for us to progress our industry.
If you believe you’re brewery could house a biomass boiler, let’s work on feasibility and grant funding together!
Sources
Figure 1. GOV.UK – https://assets.publishing.service.gov.uk/media/5a799d4ee5274a684690ad54/3153-final-report-carbon-factor.pdf
Figure 2,3,4 – Brew Resourceful Report for Vault City 2024.
