Cleaning up chainsaws
Will California have zero-emissions chainsaws by 2024? Yes, but...
Growing up in rural North-East Victoria, chainsaws were an autumn ritual. The majority of households had one wood burner, often two, and each would consume several metric tonnes of firewood each winter. So every autumn, without the incredibly noisy two-stroke engines would roar, the sawdust would pour out, and us kids would wait for the chainsaw to be safely on the ground before we’d start gathering the chopped-up pieces, dodging the disturbed ants and spiders.
On farms, in forestry, and in gardens the world over, the chainsaw is utterly ubiquitous. In 2021, roughly US$4 billion worth of chainsaws were sold. I don’t have access to expensive market research reports, but at a guess, the average chainsaw might retail for US $500, suggesting that in the order of eight million saws are sold every year.
Chainsaws are seriously polluting
Unlike other small-engined machinery, petrol-powered chainsaws, even in 2022, are almost exclusively use two-stroke engines (the only example of a four-stroke chainsaw I’ve been able to find is an Aldi special buy).
So why do modern chainsaws persist in using two-stroke engines, when other small-engined devices have switched to somewhat less-filthy four strokes? In short, power to weight, along with simplicity and ease of maintenance. Large professional chainsaws have the most powerful engines of any hand-held device; Stihl’s largest model has a 6.4 kW maximum output, and weighs roughly ten kilograms.
No four-stroke engine of a similar weight comes close. Put it this way - this chainsaw is almost as powerful as a small road-legal motorcycle. Of course, not every chainsaw is quite as high-powered as the huge saws used by professional foresters and firefighters. A typical farm saw would be roughly half as powerful, and a good medium-size saw you might have to prune some fruit trees, or chop up a small load of firewood, would be in the region of 1.5-2 kilowatts.
Two-stroke engines, whatever their size, are notoriously filthy devices. As well as being far less fuel-efficient than a comparably powerful four-stroke engine, they emit huge amounts of particulates, VOC, and carbon monoxide. So of all the small engines California is banning by 2024, these are some of the most important from a non-CO2 emissions perspective.
Where are we at?
So can we make zero-emissions chainsaws? Well, yes. But there are some caveats here, at least for the short term!
If you’re an energy nerd like me, you would have looked at the power figure for the small saw I mentioned and thought “you could power that off mains power”. And, in fact, you can, and corded electric chainsaws of this size cost virtually nothing at your local hardware store. They work just fine, by all reports. But they’re literally a nonstarter for anything other than household use in a small backyard. And - a theme we’re likely to come back to repeatedly in this series - we can’t power anything bigger off a standard mains power socket (and Australian 10 ampere 230 volt sockets can deliver notably more energy than America’s notoriously puny 110 volt, 16 ampere plugs).
But can we do better with batteries? Kinda.
The most powerful battery chainsaws currently on the Australian market are roughly equivalent to a medium petrol saw, and they’re apparently very good in that role. They’re more reliable, quieter (in relative terms - electric chainsaws still require hearing protection), need a lot less maintenance, start immediately, vibrate a lot less, and the battery packs last long enough that you’ll probably want a rest before it runs out. It’s worth noting here that smaller saws aren’t just used by homeowners. Professionals usually own multiple saws, and will switch to a smaller, lighter saw for smaller logs to reduce fatigue.
But however useful the equivalent of a medium chainsaw is, you’re not going to cut the trunk of a large tree with it, which is something a subset of chainsaw users do on a regular basis1 . Is it technically feasible to build a cordless chainsaw to match the performance of a large petrol saw?
They’re getting there. There’s an American company that sells a 3.4kW saw with a 20-inch bar (the chainsaw industry is a holdout for imperial measurements). At least one reviewer suggests that when fitted with the right battery it’s close to the performance of a typical farm saw, slicing through a decent-sized log in short order:
However, this power comes with a compromise. With the larger battery, the saw weighs in at 9 kilograms, three kilograms heavier than a typical farm saw, and only a kilogram lighter than the huge Magnum forester’s saw mentioned earlier. So we might be starting to get close to the limits of current technology.2
So, in summary, electric chainsaws available on the market in 2022 can meet the needs of the majority of chainsaw users. Costs are reasonable, particularly for professional users, as slightly higher purchase costs are likely to be more than outweighed by the savings on fuel, two-stroke oil, and maintenance. And all the other familiar benefits of electric power - smoothness, reliability, and less noise - are very much applicable to chainsaws.
Batteries and recharging? The big saws take a battery worth a bit over 300 USD. Not cheap, but petrol chainsaws this size are typically over $1000. The batteries can be recharged in about half an hour, so two batteries would be enough to keep the saw going continuously. Electric vehicles are increasingly supplied with Vehicle to Load capabilities, so in the near future mobile charging can be from an EV work vehicle if mains power is not available.
The other interesting thing about these batteries - a topic that we’ll come back to next time - is that while they’re not compatible with other manufacturers’ chainsaws, they are often compatible with other tools from the same manufacturer.
What about the future?
The saws available right now don’t quite match the very largest chainsaws used by professionals, but progress continues. The reviewer of the Greenworks electric chainsaw above pointed me to this report about a new model in development with about 25% more power (4.3 kW) and a longer bar. It also features a new, more powerful battery to match the saw. Interestingly, the new battery appears to have a similar weight to the old one. But it’s still a heavy beast, and it doesn’t quite match the power (and thus the cutting ability) of the largest petrol saws. So it seems like, for a very few applications, California’s laws will be a bit of pain.
But lithium-ion battery energy density continues to improve. There is every reason to think that within a few years, electric chainsaws will be more than powerful enough to match and exceed the performance of petrol ones, while being immensely cleaner, quieter, smoother, and cheaper to run and maintain.
Chainsaws are probably the single most challenging piece of small-engine machinery to replace with electric, and the technology is almost there.
Next, we’ll look at some examples where the electric option is already clearly superior - whipper-snippers and their heavy-duty cousins, brush cutters.
I should note here that while native forest logging is deservedly unpopular with environmentalists, farmers, firefighters, and arborists will still need to cut large trees down, and cut them up, even when native forest logging is consigned to history).
pun absolutely intended