Vaclav Smil on wood

[ I’ve extracted bits about wood from Smil’s book about materials below, read the book for the larger context.  Enormous amounts of wood were used in former civilizations with much smaller populations than today, so it’s clear we can’t go back to wood as an energy resource as fossils decline without very quickly cutting the remaining forests down. Though we’re already destroying forests at such a huge rate for agriculture and construction that perhaps forests will mostly be gone by the time declining fossils are noticeably reducing population.  Though inaccessible boreal and other forests will remain, if climate change hasn’t already converted them to grasslands.

Alice Friedemann   www.energyskeptic.com  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts:  KunstlerCast 253, KunstlerCast278, Peak Prosperity]

Vaclav Smil. 2013. Making the Modern World: Materials and Dematerialization.  Wiley.

The ships that made the first Atlantic crossings were remarkably light: a Viking ship (based on a well-preserved Gokstad vessel built around 890 CE) required the wood of 74 oaks (including 16 pairs of oars).

Fuel-wasting fireplaces and braziers resulted in a huge demand for fuel wood and charcoal to heat the expanding cities of the pre-coal era. In Paris, the demand rose from more than 400,000 loads of wood in 1735 to more than 750,000 loads in 1789 (about 1.6 Mm3) and the same amount of charcoal, prorating to more than a ton of fuel per capita (Roche, 2000).

Wood remained indispensable not only for building houses and transportation equipment (carts, wagons, coaches, boats, ships) but also—as iron smelting rose in parts of Europe—for charcoal production for blast furnaces (substitution by coke began only during the latter half of the eighteenth century and was limited to the UK). And as Europe’s maritime powers (Spain, Portugal, England, France, and Holland) competed in building large ocean-going vessels—both commercial and naval—the increasing number of such ships and their larger sizes brought unprecedented demand for the high-quality timber needed to build hulls, decks, and masts.

With wooden hulls, masts, and spars being as much as 70% of the total mass (the remainder was divided among ballast, supplies, sails, armaments, and crew) these pioneering vessels contained 60–75 tons of sawn timber (Fernández-González, 2006).

Iron production in small blast furnaces required enormous quantities of charcoal and combined with inefficient wood-to-charcoal conversion this led to widespread deforestation in iron-smelting regions: by 1700 a typical English furnace consumed 12,000 tons of wood a year (Hyde, 1977).

All railroad ties (sleepers) installed during the nineteenth century were wooden; concrete sleepers were introduced only around 1900 but remained uncommon until after World War II. Standard construction practice requires the placement of about 1900 sleepers per km of railroad track, and with a single tie weighing between roughly 70 kg (pine) and 100 kg (oak) every kilometer needed approximately 130–190 t of sawn (and preferably creosote-treated) wood. My calculations show that the rail tracks laid worldwide during the nineteenth century required at least 100 Mt of sawn wood for original construction and at least 60 Mt of additional timber for track repairs and replacements (Smil, 2013).

Wooden railway ties, that quintessential nineteenth-century innovation, maintained their high share of the global market throughout the twentieth century. During the 1990s, 94% of America’s ties were wooden.

The energy cost of market-ready lumber (timber) is low, comparable to the energy cost of many bulk mineral and basic construction materials produced by their processing. Tree felling, removal of boles from the forest, their squaring and air drying will add up to no more than about 500 MJ/t, and even with relatively energy-intensive kiln-drying (this operation may account for 80–90% of all thermal energy) the total could be as low as 1.5 and more than 3.5 GJ/t (including cutting and planing) for such common dimensional construction cuts as 2 × 4 studs used for framing North American houses.

The low energy cost of wood is also illustrated by the fact that, in Canada, the energy cost of wood products represents less than 5% of the cost of the goods sold (Meil et al., 2009). Energy costs on the order of 1–3 GJ/t are, of course, only small fractions of wood’s energy content that ranges from 15 to 17 GJ/t for air-dry material. Obviously, the energy cost of wood products rises with the degree of processing (FAO, 1990). Particle board (with a density between 0.66 and 0.70 g/cm3) may need as little as 3 GJ/t and no more than 7 GJ/t, with some 60% of all energy needed for particle drying and 20% for hot pressing.

The energy cost of paper making varies with the final product and, given the size and production scale of modern pape rmaking machines (typically 150 m long, running speeds up to 1800 m/min., and annual output of 300 000 t of paper), is not amenable to drastic changes (Austin, 2010). Unbleached packaging paper made from thermo-mechanical pulp is the least energy-expensive kind (as little as 23 GJ/t); fine bleached uncoated paper made from kraft pulp consumes at least 27 GJ/t and commonly just over 30 GJ/t (Worrell et al., 2008). Most people find it surprising that this is as much as a high-quality steel.

Recycled and de-inked newsprint or tissue can be made with less than 18 GJ/t, but the material is often down-cycled into lower quality packaging materials.

Wooden floors are much less energy intensive than the common alternatives: the total energy per square meter of flooring per year of service was put at 1.6 MJ for wood (usually oak or maple) compared to 2.3 MJ for linoleum and 2.8 MJ for vinyl.

Collection of household waste paper is expensive, and a thorough processing of the material is needed to produce clean fibers for reuse. This includes defibering of paper, cleaning and removal of all nonfiber ingredients (most often adhesive tapes, plastics, and staples), and de-inking is needed if the fibers are to be reprocessed into white paper. Reprocessing shortens the cellulose fibers and this means that paper can be recycled no more than 4 to 7 times.

Late 19th to early 20th century hand-stoked coal stoves converted no more than 20-25% or less of the fuel’s chemical energy to useful heat, though that’s good compared to the less than 10% efficiency of wood-burning fireplaces before that. Oil-fired furnace efficiency can be up to 50%, natural gas home furnaces 70-75%.

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2 Responses to Vaclav Smil on wood

  1. Philip Bogdonoff says:

    Alice, do you remember this post by Nate Hagens on The Oil Drum?

    Home Heating in the USA: A Comparison of Forests with Fossil Fuels
    http://www.theoildrum.com/node/3374

    See esp. his concluding chart, showing for each state the “Number of years of heat from forest alone (no fossil fuels)”.

    If we replaced the fossil fuels we current use for our heating needs with wood, the hardwood forests in most states would be consumed in 25 years or less — some in much, much less time.

    • energyskeptic says:

      Yes I mention this in my post When deforestation begins after peak fossils, how long will it last? within several other posts in Energy, Biomass, Wood (in http://energyskeptic.com/category/energy/biomass/wood-energy/
      I should add it to my Experts / Nate Hagens section. It certainly is a classic and took a LOT of work and research.
      I keep pestering him on when he’ll come out with his book, but it won’t be this technical, it’s an ecology / peak everything “textbook” that’s still evolving as he teaches class on this at the University of Minnesota and keeps refining it.

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