Wood stoves predate the mass availability of charcoal, and the early part of their evolution was based on the shape and combustion characteristics of split logs.

These factors dictate a typically wide rectangular firebox shape, which maximizes the length of log that can be inserted and allows for efficient loading. A flat base with no moving parts and no air intake from below makes it possible to create and maintain an ash bed. Hot air is applied from above to fuel the fire.

However, charcoal requires a different approach: it needs air to rise from below through the embers, and a solid bed of ash prevents this. You don’t want to spread the charcoal in a thin layer over the large combustion chamber of a wood-burning stove, so kilns designed for burning charcoal are circular in plan, tall and generally cylindrical, with a movable grate at their base. which can be shaken to shake. ash in the tray below.

Of course, there are a multitude of shapes and sizes on the market today, but in many you can see the lineage of the original design: be it a wood stove or a coal stove. The first one, more stocky and probably some kind of box. The latter, taller and narrower, perhaps cylindrical. This imposes layout compromises if you try to convert them.

It is often claimed that wood does not burn as well in a multi-fuel device. Depending on the design, this may be true: wood stoves are more or less sealed units, while multi-fuels may be less tightly sealed. And the presence of the grille, even if it can be covered, means that unwanted air can seep up into the combustion chamber. A taller design may be less ideal for creating the desired downward warm airflow for wood burning.

However, you might see some very impressive efficiency figures cited for modern multi-fuel designs, and they’ve clearly come a long way since the early days of coal. But just because a fire burns efficiently doesn’t mean it’s cheap. If you try to use a thin layer of charcoal on a large stove bed it will burn very quickly and you may not like the hourly consumption and the effect it will have on your wallet.

On the contrary, some argue that for use in a smoke control zone a multi-fuel boiler operating primarily on smokeless coal is needed. With modern all-wood designs meeting and exceeding legal requirements, that is no longer true. What may be more relevant is the lower cost of coal per BTU in an urban area where wood is scarce and expensive to come by.

What to do then? With many manufacturers offering identical designs with multi-fuel grilles or simpler flatbeds at a slight savings, it may seem like multi-fuel is better because it gives you options. And if you want to mix your wood with some charcoal, then that makes sense.

However, if you want to use other fuels, such as peat, straw, wood waste, and compressed paper, they all burn well, and probably better, when mixed with a traditional wood stove’s fuel supply.

So do your homework; see and check the figures of the different designs. This will help you weed out the ones that compromise performance for fuel flexibility, the ones that are genuinely smart and multi-tasking (probably the ones designed by women?).

Online there is a large number (as well as a wide range of pure wood stoves) of smart multi-fuel stoves from the manufacturers Wolverton and Pevez, as well as an integrated unit from inStove. They come in three categories: 3-5kW (below the level at which a permanent external air supply must be provided in the facility), 6-8kW: and 9-11kW. Your choice will be influenced by the opening sizes of the room and the fireplace.

These days when in wood burning mode the units have the ‘air wash’ flow which keeps the glass clean as well as being efficient.

Keep clean But it’s not all about flexibility. The nature of the fuels themselves must also be compared.

Coal, a fossil fuel, is ultimately not a renewable resource. It imposes a heavy environmental burden on its extraction and is a major cause of emissions of sulfur dioxide (acid rain), CO2, smog-forming nitrogen oxides, and mercury that accumulate in the food chain. Even smokeless fuel causes harmful emissions in its creation.

Wood, by contrast, is carbon neutral when it is continually replaced in managed forests where it absorbs CO2. Aside from some cutting and transportation costs, it has one of the lowest impacts of any combustible fuel. In the meantime, that is, while you religiously season your wood, ideally for 3 years, to reduce moisture below 20% before burning.

For country dwellers, wood is a sensible option compared to oil, propane tanks or coal, which are more expensive and less environmentally friendly.

The other factor to consider is that wood and charcoal are not happy companions in the bed of fire. The sulfur from the charcoal mixed with the moisture given off by the wood creates a highly corrosive vapor that will shorten the life of your fireplace, even if it’s stainless steel. And of course you shouldn’t use an unlined chimney, but if you did, it would work its way out, with dangerous consequences.

The solution for users of multiple fuels is to focus on one or the other at a time, rather than mixing them, if possible. And as tempting as it may be, never burn plastic or household waste. You don’t have the technology of a combined heat and power plant: what you would be creating would be a cloud of toxic waste. And that’s not really the point of these lean, eco-friendly heating machines.