Thread by @FlyingQuercus

The 3rd in my treelogy of talks entirely based on pun titles - the most egregious one of all.
Here is the sing-along version of "grading and abetting - does timber strength grading help or hinder the circular economy" at the #TIMBER2019 conference of @wood_technology of @iom3 [1]

The previous talk "From forest to last" (#EvolvingTheForest) was a more general look at the future role of #wood the #bioeconomy & #CircularEconomy - which covered, among other things, the huge potential, but also the gap between renewable & unlimited [2]

https://twitter.com/FlyingQuercus/status/1141597167972495360

& 1st talk was "Would you know a tree if you saw one?" (#napres19) in which we learned that it is hard to define a tree - & how this doesn't matter & also matters a lot.
Let's return to this topic of how words shape our thinking, not always for good [3]

https://twitter.com/FlyingQuercus/status/1140895801943711746

Circular economy doesn't mean materials move in circles. Every cycle results in material loss & degradation - so we should still aim first to reduce & reuse. Also this is also about getting more of what is available into the value chain & sending it to the best, first uses. [4]

We need to act as though the supply of wood is limited - because it is. Yes we can grow more but renewable =/= unlimited & we can no more go back 30 years and plant more than we can put more oil in the ground. [5]

With rising world living standards, & forests being called on to supply alternatives to what we currently make from non-renewable sources we can be sure there will rising need to use wood as efficiently as possible. [6]

Using wood efficiently means using as little as we can, but also considering what grade we use. If low grade does the job, using high grade is a waste of a limited resource & an opportunity cost. [7]

And just now we have some strange incentives. Carbon accounting for buildings encourages use of more wood since that locks in (previously) atmospheric carbon - but would it not be better to build two buildings from the same amount? [8]

And with the drive to modernise construction & improve productivity I think we are loosing sight of what we should do about timber grades - indeed things seem to move in the wrong direction for material use efficiency (in order to improve time & £ efficiency). Not good for 🌍 [9]

In the not so distant past, building design was based on timber strength grades that were, directly, combinations of species, growth area, & grading method. But this required setting the source at design...not good for free trade [10]

& so we got generic strength classes, which have all the numbers needed for design, but can be met after design in a number of ways by different timber sources & grading. Good for markets, simple for design, & (on paper) many options...but... [11]

There are still issues. The system is still based on knowing species & growth area because both of those are big determiners of timber properties. Regrading is also not allowed / very difficult. Both of these are big problems for recovered wood [12] blogs.napier.ac.uk/cwst/regrading…

It is hard / impossible to determine species & growth area of wood recovered from building renovation / demolition, even with good reliable records. & even if it could be done, would the grading approach for new wood still work safely anyway? [13]

Challenges for recovered wood are similar to those for getting more species into the value chain - we have less information & don't have the option of extensive testing. Moreover, with improved segregation & tree breeding this could be said of main commercial species too. [14]

As well as this, we have a narrowing in the way we use grades. They get squeezed into the old-style Henry Ford model of mass production were you can have "any colour as long as it is black". The reasons are genuine but open to solution with technology [15]

However, we seem to be loosing sight of what grades are for, & forgetting that there is a problem that can be solved - not just for the good of 🌍 but for the good of 💷too. [16]

We we frequently discard timber for reasons that don't matter. We also discard some of the potential of the timber we do use.
This is done for good reasons that improve open markets & efficiency of trade & design - but we then go do the same when we don't need those things [17]

The general strength classes fit will to the traditionally used species, but they don't fit well to others - including ones we use a lot. For example larch is much denser than spruce for its strength & stiffness, so when it gets graded that density is undervalued [18]

It gets worse when we grade - since this is done as a grade combination and we might end up with something quite different from the standard strength class profiles, as in this example with larch. [19]
For more see blogs.napier.ac.uk/cwst/beyond-gr…

In this example, the timber put in the lower grade (C16) is considerably stronger & denser than that grade requires. Now imagine that was used in a design dictated by the connection performance and C16 was not deemed strong or dense enough - the timber would not be used [20]

& since C27 is not a widely specified strength class, the timber might be sold as C24 - discarding yet more performance. The annoying thing about this is that grading settings for a C16/C24 combination, which should be better yields, don't work because of checks in the code [21]

Discarding performance, especially density, can have a significant downside for the secondary properties, which are already conservative yet often govern the design. [22]
(for more blogs.napier.ac.uk/cwst/why-gradi…)

Actually, the way we discard density can result in problems - with the timber being a lot heavier than expected.
[23] blogs.napier.ac.uk/cwst/what-is-t…

This is why we developed some strength classes more fitted to the actual properties of home grown timber (so far spruce, larch & Douglas-fir), intended especially for when you are grading timber for a particular project [24]

Not being able to use the same grading approach for recycled and recovered wood, leads also to problems making products from it - including products for which it would be a very sensible & useful raw material, such as CLT [25]

The good news is that we will look at all these problems through the @ForestValue2017 InFutUReWood project. [26]
blogs.napier.ac.uk/cwst/introduci…

These slides contain some more detail of the grading work package. The aim is to make grading of recovered timber equivalent to new timber, & to also retain as much of existing insitu timber as possible (reduce, reuse before recycle) [27]

So in summary, the way grading works now is problematic for the circular economy - not just in terms of what we can do under the rules, but also in what we think we can do, & how that makes us behave when using structural timber [28]

But the problems are solvable, and we are working on them, alongside other researchers in Europe, who also want to make things better :) [29]

For more info on our work, see blogs.napier.ac.uk/cwst/

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