Risks and rewards of baking with a wood fired oven
Years ago I got the wood fired oven bug. Having used them to bake in for nearly fifteen years now, I would say I’m fully infected. Something about them defies reason, I guess - it’s so much easier to turn on a power switch than it is to gather and store wood to fire your oven, especially for a commercial bakery operation. But somehow, for me the hard way wins every time. Someone asked me a few years back if I would ever consider using a ‘regular’ oven again (in my baking practice), and without any hesitation I was able to say ‘no way!’ Baking with a wood fired oven is where the fun is. The whole idea of not having the convenience of flipping a switch to bake is a bit challenging for some people though, so I thought I would weigh up the risks and rewards in this article. So, the good stuff first:
The rewards of wood fired baking
Wood fired baking has a number of rewards attached to the process. The first, and most obvious one, is the quality of bread that you bake. ‘Quality’ is something that is really hard to pin down, and yet it’s also so obvious. The bread from a wood fired oven is just more earthy, more real. These are not exactly scientific terms - and if one did apply science to it, I think it would be difficult to quantitatively measure exactly what it is that’s different. I mean, wood fired bread smells different, especially if it’s baked in an oven where the fire is inside the baking chamber. You get the smell and taste of the fire, and I’m definitely partial to this flavour.
Mostly, though, the ovens I work with do not have the fire inside the baking chamber. I use what is known as ‘indirect’ style ovens, so the fire is a separate thing to the baking chamber. In that way, they bake just like any other oven. The flavour of woodsmoke is not part of it at all. Nonetheless, few who have eaten bread from one of these ovens would argue - they just bake great bread. I put it down to the difference between baking with ‘thermal mass’ versus baking using ‘convection’. The former causes the bread to rise with heat which passes directly into the dough, whereas the latter is heated by the air around the dough. So one type of heat goes directly through the dough, and the other goes around it. It makes a huge difference to the way the bread bakes, and to the way the bread’s ‘mouth feel’ is when you eat it. It also means the bread will keep for longer. In short, sole baked or hearth baked bread in an oven which is heated by thermal mass is more robust. It doesn’t ‘soften’ like ordinary bread - it holds its own.
The second reward of baking using a wood fired oven is the cost of operation. Even when you take into account the time it takes to gather wood - whether it’s felling your own, gathering ‘tree fall’ (sticks and branches), or using sawmill offcuts to power your oven - the cost per bake of an indirect woodfired oven is substantially less than an electric or gas oven. Having said that, if you have to purchase split timber from a vendor, your costs may be similar - but anyone who runs a wood fired oven commercially will work out very quickly that fuel is a direct cost and this has to be minimised. My own practice has involved using sawmill offcut for the past six or more years, as I’ve been living within easy driving distance of a sawmill. I calculate that my cost per bake is less than a quarter that of electricity on average.
Which leads me to the third reward. A wood fired oven makes you think about resource usage. Using an electric oven only causes you to worry about how much resource you use when the bill comes in. It’s an invisible factor most of the time. Your only real awareness of resource use is how much it costs you. On the other hand, when you can see the pile of fuel in front of you getting smaller each time you bake, you become aware of the resource you are using. You also become tuned to the qualities of the wood itself - which types burn hottest, fastest or longest. And when you fell your own timber, you see just how many loaves a single tree can bake. This type of consciousness is something I believe we all could use to our advantage when it comes to lowering our footprint on the earth. I guess the word to describe this reward would be ‘connectedness’. A wood fired oven helps the user to connect to the environment meaningfully.
These three rewards, for me, are enough. There are others, though. A big reward is not having to hook up three phase power or commercial gas supply in the first place. If you are wanting to bake from home, as so many people are now, the cost of this can be crippling, and simply makes the whole enterprise unviable before even leaving the planners desk. A wood fired setup can enable people to run their own show with very little capital, and longer term can also help them to keep their running costs down. A fully off grid setup is also possible, which means the baker isn’t affected by power outages. These can really throw a spanner in things when you are half way through a bake and the power goes down.
And the risks…
Wood fired baking does raise some issues though.
Wood fired ovens create smoke, and this can have an affect on air quality.
Working a wood fired oven involves a bit more labour than using a regular oven too, and this has to be factored in to the cost of operation.
High thermal mass ovens take time to heat up, and this is a resource use issue which needs to be carefully managed.
Wood fired ovens also tend to radiate a lot of heat from opening the firebox, so they need to be carefully planned in to the bakery so as not to create too much heat or smoke.
Using a woodfired oven in a fire prone area could potentially be an environmental risk.
Lets unpack these risk issues one at a time. The first is smoke. An inefficient oven creates smoke, as smoke itself is unburnt particulate. A pollutant to be avoided or at least reduced. There are two parts to this - operation and design. From an operational view, the fire has to be managed at all times. A smouldering, slow burning fire generates smoke, especially when fuel is introduced. However, a fast burning fire creates less smoke. Thus, a fast burning fire is desirable, no matter what type of oven you are using. This can be quite an art to master. In the end, fires are smoky when they are first lit, and then as they establish, the smoke becomes less. Learning the art of running any wood fired oven takes time, and this is something people have to learn how to do properly if they want to keep doing it for a long time.
The second part of smoke management is oven design. There are a number of things which can be helpful if addressed at the design stage. The first is the way the firebox works. In a direct oven, where the fire is inside the baking chamber, the internal shape and proportion of the oven is critically important. These ovens can be shockingly smoky, especially if the fire can’t get the right amount of air to burn efficiently. However, a good design coupled with skilled management will minimise the issue.
Indirect ovens, or ovens which have a separate firebox, have an advantage here, especially if properly designed. These ovens can utilise a smaller, well ventilated firebox, which, when the fire is established, have so much heat stored in them that they burn their own smoke. I have been working on what I term ‘high airflow’ fireboxes for some years now, and all my designs incorporate this principle as the basic starting point. In my latest design, which I’ll be writing about in an upcoming article, I have incorporated ‘gasification’ as a central tenet of the way the firebox works. I have used it before with limited success, but trials of the latest approach have so far shown me that this is the way to go. My barrel oven design has the entire firebox built as a gasifier. Stay tuned for more about this when I have finished building the oven.
Another design initiative to minimise smoke is the way the chimney works. The height of the chimney in any oven is critical. The chimney should be made high enough to lift the smoke away from nearby buildings and into the atmosphere where it can disperse rapidly. Having a tall chimney also allows the fire to draw batter, which in turn leads to less smoke coming out. Often, a smoky oven can be improved by simply extending the chimney. Of course in some cases a chimney being made longer can cause the oven to draw less efficiently - but this is mostly because the firebox cannot establish enough airflow to push the smoke fast enough up the chimney in the first place.
Running a woodfired oven means feeding it with fuel on a regular basis, and this in itself brings us to the next issue: labour. There’s no getting away from this issue, but it can be minimised by thinking through the baking process carefully.
Most bakers will be doing preparation duties while they are warming the oven, utilising their time efficiently while the oven is heating up. They will time the production and baking carefully so that everything works in sync with the oven. The ideal is to run production so that the oven is optimally hot at exactly the right time for loading, and then once the oven is loaded, it is kept full until the bake is finished, with no gaps between loads. There is also some labour involved in preparing and storing wood. Having a wood splitter or using fine offcut can minimise this, but it has to be factored in nonetheless.
The issue of heating large thermal mass can be minimised by the way a bakery is run, as well as in the way the oven is designed and insulated. Bakeries using the oven on multiple concurrent days achieve efficiencies by the effect of heat being held in the thermal mass from the day before. Wrapping the oven in the right amount of insulation to best store heat reduces the inefficiency of having to heat the thermal mass from cold each time.
Another solution to this issue can be to design the oven to heat up quickly from cold. My barrel oven is specifically designed to do this, as the thermal mass is outside the baking chamber, rather than inside it. Thus, heat up time is minimised. This type of oven is best for weekly bakers like me.
Using my travelling oven in Western Australia some years back. The terracotta pots on the top of the oven are ‘heat sinks’ - I heated them up on the top of the oven and then transferred them to the proofer to heat it.
Heat and smoke from the firebox is an issue with all woodfired ovens. Again, it can be minimised by bakery design. I like to put my wood fired ovens outside if possible, where there is separation from the bakery production space, and where there is plenty of natural airflow. I tend to wrap these outside baking areas in shade cloth or similar to minimise the possibility of flies or dust or smoke. If an oven must be placed inside, there should be some thought as to internal ventilation of the space. As anyone who has worked in a bakery will tell you, this is not an issue specifically for wood fired bakeries. Any workspace with a big oven in it is going to get hot, so proper thought around this issue at the planning stage is essential.
Using a wood fired oven in a fire prone area is another real issue, though it is also one which is fairly easy to mitigate. The simplest solution to reduce potential embers escaping from the chimney is to install stainless mesh (there is an Australian Standard mesh available for exactly this reason) on the chimney outlet. The mesh is fine enough to prevent ash passing through, though you need to design the mesh protector in such a way that airflow is maintained. This can be done by fashioning the mesh into a tall cylinder so that air between the holes is maximised.
Some wood fired ovens spew out embers fairly easily, while others don’t. In a well designed wood fired oven, embers are either burnt before exiting the oven, or pass around a number of turns and twists before heading for the flue outlet. Each turn captures particulate.
If your oven is allowing embers to exit in the first place, this shows it isn’t very efficient. This is definitely something to become aware of, and is important in a management sense, whether you are in a fire prone area or not.
Barrel Oven Sketch
In my next article here I’ll be talking about my latest oven build, the Barrel Oven. It’s a small commercial wood fired oven, capable of baking about 30 - 40 loaves at a time. This one has been specially designed for occasional bakers like me, who do not bake on a daily basis. We need an oven to be able to heat up really quickly, and one which will use as little fuel as possible. This design is a refinement of my original barrel oven, which I built about 8 years ago. I’ve incorporated gasification into the design, as well as some new tricks to make living with the oven long term more enjoyable.
At the time of writing this, I have not completed plans for this oven as a DIY project - but I do intend to, once the oven has been commissioned. If you would like to support the build, I have been running some crowd funding campaigns to help with building costs and retooling my bakery. All support is welcome, and once the oven is finished I will match your contribution dollar for dollar with services or bread. At the time of writing, the Barrel Oven is nearing completion, but extra support is still needed, as there is still a bakery to rebuild!
Note: Since beginning the build, I have had lots of support from friends of the bakery directly, as we were beset by a fire late in 2020. This support has been through another channel, which can be linked here. This one shows total contributions towards rebuilding the bakery, including direct contributions and Gofundme ones as well. I’m eternally grateful to everyone who has assisted so far. You will not be forgotten!