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| Spike in the Log |
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| Pulled from the Log |
EROEI – Energy Return On Energy Invested
Wood Heat for the Lazy
It’s often said that wood is the fuel that warms us twice. But that’s understated!
Lessee…
Locate, fall and limb tree (standing dead and dry).
Buck into stove-length rounds.
Split to various sizes..
Transport to home.
Stack (store) handy to stove.
COOK and/or HEAT.
Clean stove (periodically).
By my count, it warms us seven times! On our waterborne home, this omits fetching wood in from the woodshed. And I didn’t even mention greenwood seasonin!.
All this represents a considerable amount of energy invested in the energy returned for desired cooking and heating.
Similar to cost/benefit analysis, EROEI is the ratio of the amount of energy we get from a given energy expenditure; the bang for our energetic buck. Without doing any math, it urges us to think about our energy inputs, outputs and benefits in relation to costs. It’s an orienting concept. High EROEI is good; Low EROEI is less good. EROEI = 1 is pointless; EROEI < 1 is a downward spiral.
For fuels such as diesel, gas or electric, our personal EROEI may appear lesser, but money must be made and spent with all the energy investments that requires of us. The equation is more complex, perhaps, but pertains, nonetheless.
From our point of view, a few hours passed weekly in beautiful woods and useful exertion in return for energy independance has been a good bargain. It has gotten us off our lazy butts and into the wider world. Our blood flowing and our backs strong. But as we age and our store of individual energy diminishes we’re looking ahead.
What follows are a handful of approaches, resources and tactics aimed at increasing our return and reducing our investment for higher EROEI.
Smaller Volume plus Insulation
Insulation is a lesson we learned better late than never. Higher R-value hull and overheads with double-paned windows have become our standard practice.
Now we’re looking to reduce volume. The smaller a space to heat, the less energy return is required, which in turn lowers our necessary energy investment (for heating, but also for row/sailing and maintenance).
In WAYWARD (our present boat), the living space is 20ft x 8ft x 5ft in the main, plus a trunk cabin and hatch that end up totalling about 1000ft3. The boat we’re now building for our dotage will be 12ft x 4ft x 4ft plus a small galley extension to total about 250ft3.
We’ll have only a quarter the volume to heat!
Rocket Stoves
It’s said that the energy lost in woodsmoke is nearly half the total of unburnt wood. Rocket Stoves burn that smoke, reducing wood demand accordingly. With a quarter the volume to heat and (about) half the wood per unit of heat, we’re already talking around 1/8th the required energy investment for the desired outcome.
Furthermore, they reduce or eliminate energy invested in points 1-4 from our list above.
Target small dead limbs – Thumb to wrist size covers cooking to heating. This eliminates whole tree felling and brings the dead limbs of many otherwise living trees online. In our forests, there is a super-abundance of limbs in this range, both among lower branches and windfallen. As a bonus, our coniferous limbs are sap rich near the bole for extra energy density.
Process to length – All methods (see below) are much easier with small diameters than bucking sound wood. Since there is no stove box, we can use longer pieces, reducing the number of cuts.
No splitting! – This is especially helpful as long-fibered spruce, generally our most practical firewood, resists splitting (which make it great for spars).
Transport – Because gathering is such light duty, we can typically keep up by gathering a small amount on our daily ventures on shore, spreading effort over longer time. In our case, the heavy packs we’ve been using over treacherous footing constantly threaten strain or sprain… smaller loads are fail-safer.
These points are hard to quantify, but further increase our EROEI to a substantial degree.
Alternatives to Sawing
Sawing wood is hard work, even with a blade that is well sharpened and set (a process of considerable energy investment!). Nevertheless, it’s the least effort for bucking up rounds which are sound and of larger diameter, and/or of a tough species. For small diameters, however, other methods are faster and take less effort. As a bonus, since small stuff is less stable for sawing, the saw can skitter dangerously… other methods, while not carefree, are generally a degree fail-safer.
Lop – A good set of ratcheting anvil loppers (for dry wood) makes quick and easy work of any limb within its range.
Chop - With an ax, hatchet or hatchet/maul and a hardspot (stump or log) chop down perpendicular with a single strike on opposing sides (two, four or more according to difficulty) of a limb to create a weak spot (we’re not generally chopping through). Pull the end back to bridge between hardspot and ground and smack it with the back of the tool to break or use any of the following methods. It’s generally more efficient to first chop along the whole log, then break along in one go.
Break - Depending on diameter, species, soundness and dryness wood can be directly broken by hand or across a knee, tree, limb, rock, etc.. Holding to either side and striking at the breakpoint impact loads that point for usually good results (use caution to preserve your wrists against that same impact!).
Leverage - Leverage multiplies our power, greatly reducing energy invested. Look for a hard point and a fulcrum a little less than the desired length apart. Closely spaced trees or limbs work well, as do rock neighbors, crevasses and overhangs. Insert the stick with its end on the (further) hardspot and break point on the (nearer) fulcrum. Pry until broken. Sometimes it helps to break halfway, turn the stick 180deg and finish the other way.
Whack Job - This one only works with punky wood, but is fastest and very easy. Find a hardspot, preferably with a sharpish edge (rock, say). Swing the wood like a bat to impact at your desired break point. Momentum snaps the stick on contact. As with an axe, use effort to accelerate the swing but relax before impact (ride the end of the swing) to reduce shock to your joints.
Cudgeling - Again, pretty much for punkwood. Find a soundwood cudgel (usually about the size of a baseball bat), bridge the victim, and whop it in the middle to break. Watch out for flying ends!
All these methods can be mixed and matched as convenient. The ‘tool-less’ methods are especially helpful in the field for impromptu picnics, and help reduce long wood for a smaller, safer fire.
As you can see, the more brittle the wood, the easier it all gets. Which brings us to…
Punky Wood
Punky (rotting) wood has lost a portion of its energy content to oxidation… in effect, it is pre-burnt to a degree. But a goodly amount of energy remains.
The benefit is that fermentation has weakened the longitudinal fibers, leaving it easy to break by any of the manual means or with ‘found’ tools. In minutes of light effort, armloads of firewood can be gathered with neither lop, chop nor saw. No tools to sharpen, transport or lose!!
While gathering, we look for the rather broad ‘Goldilocks’ point: not too firm, not too far gone. Light and dry. Well-aired in place or partially elevated above the ground, they dry quickly. The woods are rife with low-hanging dead- and fallen limbs in this state. Close to our fire, boat or dory is a plus.
Punkwood is consumed quicker than sound wood. Thicker diameters can be used to slow and cool combustion (which is proportional to engaged surface area). Where sound wood thin enough to break by hand burns away quick and hot, we can go for larger diameters in punky woods that burn cooler and last far longer. This is especially useful for even heat of a cool evening. Thick ‘uns also take up less storage volume than the equivalent mass in small stuff.
In our parts alders line much of the coast. This quick-growing ‘hardwood’ produces many dead limbs which go punky in short order. Other species such as poplars, aspens and birch are similar.
A couple of cons with this approach…
Compared to sound wood, punkwood requires more volume to transport, tend and store for any given amount of heat. Greater throughput means more ash and its clean-out. These energy investments weigh against its other gains.
While punkwood dries quickly, it absorbs water just as readily. In wet weather (which includes most of winter), it’s often too wet to use.
Still and all, for much of the year, it requires substantially less energy invested for energy returned. So low, in fact, that ‘bouquets’ of punkwood from our daily walks generally supply us with all the summertime wood we need.
‘Spikes’
Spikes are the pitchy roots of limbs from a rotten conifer trunk of pitch rich species (e.g., some pines, spruce, fir?). The pitch is energy dense AND preserves the spike AND waterproofs it… spikes are only ever surface-wet and dry quickly. The rest of the limb has usually rotted away leaving stove-length pieces.
Once the trunk of a fallen tree is fully soft, one can walk along it and harvest the limbs, pulling the spikes like carrots. Or walk along many creeks and beaches and simply pick up spikes (which don’t float) from trees long gone. A few days in the sun or behind the stove and good to go.
Bark
Beachcombed fir bark is a windfall, as fir only grows far to the south of us. Ranging from 1 1/2in to 6in thick and up to 6ft long, it is easily broken to length. Quite resinous, it resists absorbing water and dries quickly in any case. It charcoals quickly but lasts long, perfect for warming on a rainy day.
Alan and Sharie Farrell used mostly fir bark, especially in their later years. It became scarce as British Columbia logging receded, and this became quite a problem for them as time went on.
Fir bark works great in a fire-box. We haven’t yet tried it in our Rocket Stove, and I have my doubts. Too smoky? And the Rocket principle is a hot burn.
But there are other applications…
Coppicing
Coppicing is the practice of cutting a swift-growing species (such as alders, willows, poplars and many fruit trees!) back to a stump trunk. New limbs spring up in their hundreds for sustainable harvest. It was commonly used for prolific woodlot fuel production on farms and commercial stands.
This approach looks to be a promising option for favorite spots…an arboreal guerrilla garden!
*****
There are many things we’ll miss about our current wood-range with oven. But I gotta say, its low EROEI won’t be one of them.
We’ll just have to find other ways to get our exercise!
