[GSBN] Sharing thoughts on pros and cons of using straw as a building material.

[Derek Roff]

It’s great to hear your thoughts, Lars, and John’s comments, as well.  I have a few reactions to Lars’ four points.

1)  “the straw belongs in the earth”  I’m not at all sure that the straw belongs in the earth.  All current cereal grains are relatively new creations of selective breeding.  Looking back to their relatives, diverse grasses in evolutionary times, the grass/straw would never make it into the soil directly.  In many, many places, dried grasses are likely to burn at the end of each season through natural fires.  In our current agricultural era, burning the straw was also the most common choice, until pollution concerns reduced it.  Maybe not in Denmark, and wet climates, where decomposing on the surface would be more likely, in ancient times.  The intact root system would contribute to soil health.  How much potassium and phosphorous is in the straw, and how much could make it back into the soil, after the straw above the surface burns or rots?  My guess is, not much.

I doubt that growing cereals takes carbon out of the soil.  In fact, in natural growth, it adds carbon to the soil.  Almost all the carbon in growing plants comes from the carbon dioxide in the air.  Growing grains put some of this carbon into the root system, which remains in the soil, if the soil isn’t tilled.  There is no way to get the straw into the soil without plowing or tilling, both of which release more carbon from the soil than the amount that the straw would add.  Tilling in straw has another couple of possible negatives- increasing the risk of fungus and disease for next year’s crop, and diminishing the available nitrogen in the soil.  So even without the cost factor and the fossil fuel used in chopping and tilling the straw into the soil, there are ecological reasons to prefer using it in building houses.

2)  “we are only delaying the return of the straw to the earth”  This point is built on the first, which is the thesis that the straw should return to the soil.  Atmospheric CO2 is the greatest ecological crisis of this period, and locking up as much carbon as possible, right now, is one of the biggest contributions that we can make.  If enough strawbale houses were built each year to lock up a lot of carbon for fifty to one hundred years, this would be a very good thing.  In contrast, tilling the straw into the soil now, or letting it burn or rot, all put much more carbon into the atmosphere in the current cycle of a year or two.  That has negative ecological impacts.

3)  “building with staw bales sequesters CO2”  I agree.  We need to build a lot more straw bale houses.

4)  “the farmer can make €90/ton selling straw”  At that price, it is unlikely that any farmer is going to till the straw into the soil.  I don’t know what price bales sell for in Denmark, but US bale prices would earn the farmer a bit more for a ton of straw bales than Lars indicates for a ton of bulk straw.  If that is true in Denmark as well, then there is a financial advantage to the farmer to make building bales.

I love thinking about and discussing these questions.  Thanks, Lars.

Derek

Derek Roff
derek at unm.edu<mailto:derek at unm.edu>




On Jul 28, 2018, at 2:52 PM, John Glassford <jacksflat at gmail.com<mailto:jacksflat at gmail.com>> wrote:

Morning Lars

We are at the start of a drought here down under especially the Eastern States of Queensland and New South Wales.

Straw is still available and we look forward to the next harvest in November.

Victoria will have straw bales.  Plenty to meet the needs of our "fledgling" industry of straw bale building.

#1 Benefit for using straw here in Australia is that a vast amount of straw is burnt each and every year.  Almost a million tonnes just from rice straw.

#2 Benefit straw consumes a fraction of the energy that goes into making bricks and concrete blocks.

#3 Benefit we have now built in areas of very high bush fire attack levels, not many products on the market today can equal straw bale.

#4 Benefit comes back to cost and even in the drought it is still more economical than bricks or weatherboard.

I have no arguments in the opposite!

Say G' day to Jo!

The Straw Wolf

Huff 'n' Puff Constructions
http://www.glassford.com.au<http://www.glassford.com.au/>
61 2 6927 6027
In Australia (02) 6927 6027
Mobile 0412 11 61 57

0498 190 880<tel:0498%20190%20880>


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