How it Works

Ashland School of Environmental Technology

Industrial Version

The Developing World

StrawJet - How It Works

2 in. cable

The Idea

The concept behind the StrawJet technology is very simple. Straw and many other field crops have a hollow stem or one filled with soft pith. They all can support considerable loads parallel to the axis of the straw but are quite weak when stressed in any other direction, (try this with your drinking straw). David Ward and his team have developed a way to utilize this inherent strength of hollow straw.

Cross Section of Cable

The StrawJet harvests straw in the field before it has been crushed or damaged, orients the stems so they are all parallel, adds a clay based binding material, compresses the bundle and binds it into a continuous length of 2 inch cable using a polyester yarn. Once the clay has dried, the cable becomes a rigid cylinder.

Industrial Version Cables can be combined into a construction material in several ways. To meet the demand to reduce labor costs at the building site, we are developing a system to combine the cables into standard dimension building panels and into completed wall systems in the field.
	Model of StrawJet System Showing: (1) A modified combine making cables and harvesting grain simultaneously. (2) Loom truck collecting cables, cutting them to 8 foot lengths, weaving them into a mat and rolling the mat for ease of handling. (3) Mat ready for use and behind the roll a stack of mats cut to 8ft.x 8ft with interlocking ends to add strength to the joint. (4) Unroller and laminator. Each pass of unroller adds another layer to composite wall. Layers are pinned with bamboo and bonded with a matrix material. Alternate layers are oriented at right angles by inserting the 8 foot sections of interlocking mats shown in (3). This provides longitudinal strength in both directions.
	(5) A undulating wall section being made by alternate placement of supporting beams under the panel and weights on top. (6) A section of wall with the mobile cutter ready to cut it into panels. The cutter can be programed to cut out entire wall sections complete with door and window openings. (7) Finished panels being stacked on truck for delivery.
	(8) The ability to make curved walls allows for creative architectural designs. Roof panels could also be curved to utilize the inherent strength of a domed structure. (9) Completed wall panel being lowered in place.
Completed Wall Structure Walls can be built up using different materials to meet specific design requirements. The example at the left shows a wall with vertical straw columns and horizontal members from Jerusalem Artichoke. Also shown is a conduit to carry electrical wires and / or plumbing.

Hand Fed Version For
Developing Countries and Disaster Relief

We are in the process of designing and building a much simpler hand fed harvester to produce cable where the straw, or other fiber, is brought to the machine. Another simple machine wraps four cables together with a matrix material binder to form a continuous "beam" called StrawCore.

StrawCore members can be combined into panels or used individually. Using this technology, buildings can be constructed rapidly with only hand labor and without requiring large capacity trucks to move the material from the field to the building site.

Using the same technique, and utilizing fibers with more strength than wheat straw such as hemp, flax, palm fronds or bamboo, beams can be constructed to span between walls to support the roof. In developing countries this would be an important aspect of the technology because obtaining wood to hold up the roof is often difficult and expensive.
Cable made from palm fronds and Jerusalem artichoke

Industrial Version

Completed Wall Structure

Hand Fed Version For Developing Countries and Disaster Relief

Hand Fed Version For
Developing Countries and Disaster Relief