A chainsaw and log splitter can make quick work of a cord of firewood. But they’re dependent on fossil fuels. How do saws and splitting axes stack up? We tested it out this spring as part of our Low Tech R & D series. You can find this and other tests at the project page.
What are the cost, energy, time, and labor differences between using a chainsaw and log splitter or a one-person crosscut saw and splitting axe. We expect that a saw and axe compare favorably to chainsaws and log splitters in a) cost and b) energy but not c) time or d) labor.
Firewood was cut and split using a gas-powered saw and splitter as well as a one-person crosscut saw and splitting axe. A myriad of data were recorded, including cost of equipment, time required for cutting and splitting in each method, and calories and fuel burned for each step and method. Wood was measured by square inches cut (A=π (d/2)²) and square feet of the face of stacked wood.
Over two months (2 Feb–3 Apr, 2021) I cut and split two thirds of a cord of wood (a cord is a standard firewood unit, measuring 4 ft × 8 ft × 4 ft of stacked, split wood; a face cord is a single width stack measuring 4 ft × 8 ft × 1 1/3 ft). For the manual sawing I used an antique “one and a half man” saw (similar to this; mine was $50, $300 new) and for splitting a Fiskars splitting axe ($70). I borrowed my neighbor’s Poulan Pro PR4016 ($169) and log splitter (Speeco 25 Ton, similar to this $1,050 one). Thanks to my neighbor Keith A. for lending the saw and splitter and Phil B. for helping run the splitter. Thanks also to Joe and Susan L. for access to the wood for the test.
For many of us, time is the most pressing limit on what we can get done. In this test, the results are absolutely clear. A chainsaw is by far the most efficient slayer of logs, turning long lengths into short rounds in a fifth of the time of a hand saw. If we extrapolate my hand sawing and chainsawing to the amount of time needed to cut up logs for a cord of firewood, it would have taken me about twenty-five hours by hand and only five and a half with the chainsaw.
Splitting also has a clear winner, but not the one I expected. I anticipated that the splitter would be quicker than the axe, and after we had run the machine for an hour, I thought this was the case, but when I crunched the numbers, it was clear that because the splitter used two people it was actually slower than splitting by hand. In this case, a full cord of wood could be split by hand in four and a half hours, while the splitter would need two people for two and a half hours, or five work hours total. Now perhaps a single person running the machine is a little faster overall, but these results suggest that an axe is faster or at least not much slower if someone is alone and very efficient.
The methods vary even more widely when cost is considered. The manual methods are the cheapest, both in start-up and running costs. In the case of splitting, it is a blow-out.
An antique cross-cut saw can be found for a reasonable price (mine was $50), but even if you have to buy a new one at $300, the lifetime costs of the saw (another $50 for a sharpening kit), which can be decades, wins out over the chainsaw. Even this reasonably priced saw ($169) should last a decade, but over that five hundred hours of its use-life, it will burn through 62.5 gal of gas, which if we take to cost $2.50, that’s an additional $156.25. Plus the gallons of chain oil would add another $320 ($16/gal × 20 gal) and a replacement chain over the lifetime ($15) plus sharpening kit ($20). This adds up to a decade cost for the chainsaw of $660.25. If that amounts to five hundred hours, that’d cut up ninety cords of wood, or about $7.37/cord. Cutting the same cord with a saw only runs $0.37 (the new saw would be $1.11/cord at 9 cords per year over 30 year lifetime). But as mentioned above, it would take five times as long.
The axe is the hands-down winner over the splitter, though. My neighbor, Keith A., says his splitters last more than a decade. At a price of $1,050, plus a gallon of gas per hour, splitting up ninety cords over a decade would cost $17.42 ((2.3 gal × $2.50/gal) + ($1,050/90 cords)). My axe, coming it at $66, should last at least two decades, but even if it didn’t, that’d be just $0.73/cord (assuming nine cords a year for a decade). And, as we’ve seen above, the axe is as fast or faster than the splitter.
To measure labor and effort, we use Kcal (otherwise known as food calories) as a uniform measure of human effort. This is measured through a heart monitor and sports software to convert the beats-per-minute into calories burned based on the user’s size and mass. In addition, we have to consider the kilocalories of the gas fed into the saw and splitter, but that’s in the next section.
Again the chainsaw is the clear winner over the hand saw. To saw up a cord of wood, a chainsaw operator would only use about 1500 Kcal. To do the same amount of work, someone using a crosscut saw would expend a whopping 12,906 Kcal! This is a huge difference.
The splitter also wins out over the axe, but it isn’t a blow out. Splitting a cord of wood by hand burns about 2700 Kcal, while running a splitter to do the same work burns 1861 Kcal. Since both require the shifting and stacking of large amounts of wood, the splitting itself is the only difference and accounts for the extra 1000 Kcal, which really isn’t that much, as a 20-mile bike ride or a 10-mile run burns the same amount.
And of course this assumes that the person doing the splitting is able-bodied. If you have mobility or heart issues, chain saws and splitters are much less stressful to your body and that may have to be your most important consideration.
Energy and Emissions
I’m particularly interested in emissions and energy for two reasons. First, people often debate how sustainable and green a woodstove is. Second, as we need to reduce greenhouse gas emissions, burning less fuel and doing things efficiently is increasingly important. We’ll take the EPA’s standard of 8.9 kg CO₂/gal gas burned. It is also important to remember the large amounts of other gasses and particulate matter that the two-stroke chainsaw is emitting. Additionally, most chainsaws are a two-stroke engine, which emit up to 300 times more greenhouse gasses when burning fuel than some four-stroke vehicles. Even without going into these significant emissions, let’s look at the carbon alone.
To cut a cord of wood, a chainsaw will emit 6.4 kg of carbon (plus plenty of much worse stuff). That’s about the same amount that a power plant emits to create 7 kWh, a third of what a typical house uses in a day. The splitter will burn through 2.3 gal, emitting 20.47 kg of carbon to split that same cord, which is the equivalent of the carbon released by a power plant to supply a whole day’s worth of power to a house.
This doesn’t even begin to take into account the significant emissions from the manufacturing process. I haven’t been able to find exact data on the carbon footprint of chainsaw production, but it is mostly steel and plastic. A computer’s production footprint ranges from 200 to 800 kg of emissions, so I imagine it is in this range. It was equally hard to find data on a splitter (please point me to these data if you find them). A new smart car, one of the smallest made, still accounts for six tons of emissions. Based on this, I’d guess a couple of tons for the splitter. These data came from How Bad Are Bananas: The Carbon Footprint of Everything.
The saw and the axe do not emit any carbon. But wait, doesn’t the user breathe out carbon dioxide? Yes, of course, but that CO₂ is part of the existing atmospheric carbon cycle. That means it already was factored into the greenhouse effect. The carbon emitted from the engine is new carbon added to the atmosphere from ancient sources. Think of it this way, if you pee into a pool that you are already in, it doesn’t raise the water level, but if you urinate into a pool from the edge, it does. This is why I consider burning sustainably harvested wood in the winter a better alternative than using fuel oil, propane, or natural gas: the carbon from those trees was recently in the atmosphere and would be released again if the tree fell and rotted.
We can also look at this through energy, in this case, Kcal embodied in the gallons of gas burned. Each gallon has 31,000 Kcal. We can compare this energetic output to our own bodies and simple tools to see how shockingly efficient we are as machines. The chainsaw would burn 0.72 gal of gas to cut a cord of wood, or 22,280 Kcal. Add to that the 1500 Kcal of the user and a cord of wood requires 23,780 Kcal to cut. This makes our 12,906 Kcal used in the hand saw look downright efficient at 54 percent of the calories. This is even more true when splitting. The machine burns 71,300 Kcal to process a full cord. The user(s) add 1861, bringing the total to 73,161 Kcal. An axe, requiring only 2701 Kcal to split that same cord demonstrates the extreme efficiency of the method — it is twenty-seven times more efficient. Think about it: an axe is a heavy wedge that you lift up about a meter and drop into a log. You store energy by lifting the axe head up and then release it by dropping it, letting gravity do the work. The machine must push a wedge straight through the wood using brute force alone.
If we consider the fossil fuels used to create the extra food calories for the manual methods, the differences are accentuated. For every food calorie (Kcal) we eat, about 10 Kcal of fossil fuels are burned in production and transportation. So the 12,906 Kcal more the handsaw used means 129,060 fossil fuels were used to create those food calories. But then it also takes energy to produce the gasoline. If we take a figure of 1:11 (1 gal burned to create 11 gal gasoline), we can add 9 percent to the gasoline Kcal burned. The chainsaw then, burned 39,285 Kcal with operator ([22,280 × 1.09] + [1500 × 10]). The axe’s 2701 Kcal represent 27,010 Kcal of fossil fuels burned, compared to 96,327 Kcal for the splitter and operator ([71,300 × 1.09] + [1861 × 10]).
We can accept part of our hypothesis. The handsaw was cheaper in cost and energy but the chainsaw dominated in time and labor — significantly. But the hypothesis was rejected for the axe in that while it was cheaper in cost and energy, it was also faster and only a little more labor intensive than using the splitter. The major work is shifting the wood, not the splitting.
In the end, one’s decision comes down to what counts most for you: time, money, the environment. If time is your guiding factor, then bucking logs with a chainsaw and the splitting with an axe is the way to go. If money is your lodestar, then all by hand is the best option. This holds true for the environment as well unless you consider the fossil fuels used in the production of the food. In all cases, the splitting axe or maul is more efficient in time and cost, and only a little less so in calories (and who doesn’t have a few extra calories to work off, am I right?). If a chainsaw company wants to send me an electric chainsaw to test out, I will be glad to run it through its paces. In that case, I anticipate the carbon (and monetary) costs are upfront and the ecological savings come in the use and charging (which will vary by a location’s energy mix).
The following video summarizes this study: