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Developing
technologies for fabricating load bearing,
insulating construction materials from surplus straw and other fibrous plant materials such as flax or palm fronds.
Solutions
to the need for better housing
in a world of diminishing resources.
Background
Currently ASET
is focused on finding synergistic solutions to two problems, the
need for low cost energy efficient, housing free from environmental
toxins, and the need to find better uses for agricultural by products
such as straw left over after the harvest of grains. In much of
the world, wood is in short supply and forests are threatened. Traditional
alternatives such as Adobe which does utilize some straw, are labor
intensive and do not stand up well in earthquake prone regions.
Straw bale construction is also labor intensive, and requires as
significant amount of wood to create rigid load bearing walls. Both
construction techniques require wood or some other structural material
to hold up the roof. With this in mind David Ward set out to find
a solution.
Ten years of
research and head scratching led to the building of the first prototype
of a harvester that could bind straw into a cable, the first stage
on the way to a useful product.
In late 2001 with the success of the first prototype, David began constructing the prototype II, and a the same time gathering the human resources to form the Ashland School of Environmental Technology. By December of 2002, the first StrawJet had been completed and field-tested at the Oregon State University Agricultural Experiment Station, and ASET had been established as a non-profit corporation.
Work continued to automate the system, and in 2005, a for profit company StrawJet Inc. was established. StrawJet Inc. received a grant from the EPA through the SBIR (Small Business Innovation Research) program to begin developing a commercial model. The prototype III developed with that grant solved many of the technical issues involved in producing a commercial unit.
Currently two different machines are under development. One is a simple hand fed version for the developing world where harvests are done by hand or where alternative fibers such as palm fronds will be used. Work also continues on the larger version for the world of industrial agriculture.
The concept of the technology
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| Cable |
The desire to use straw as a building material is as old as the agricultural revolution, but straw based products have always suffered from the apparent lack of strength of the plant itself. Previous technologies from straw bale construction to the recent development of compressed straw-board and straw panels have all begun with crushed, chopped straw. The fundamental advance embodied in the Strawjet technology is the use of the whole undamaged plant stem. The compressive strength of straw when loaded parallel with the stem is impressive. The Strawjet system seeks to use that strength by bundling the plant stems into "cables" about 2 inches in diameter.
These cables can then be combined to form individual construction members or into panels or entire wall systems. To be compatible with the demands of the U.S. building industry to reduce labor costs at the building site, a panelized construction system is being developed using cables woven into a continuous mat. (see: how it works) A wall is built up by laminating successive layers of mat together with a binding material primarily made of clay, soil and paper pulp. Alternate layers are oriented at right angles to provided strength along both directions.
| The Woven Mat System |
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| The StrawCore System |
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An alternate system combines 4 cables into a "beam" called StrawCore and the recombines the
4 in.x 4 in. members to make structural members such as roof beams, arches or wall panels. The finished material is coated with a plaster made from soil, clay and paper pulp.
Because the material is flexible when it is first made, curved building components can be made efficiently leading to greater design freedom, and the ability to utilize the natural strength of curved forms.
Benefits of the StrawJet Buildings
The
true significance of this technology is the universal availability
of straw on a continuously renewable basis. Most
other building materials such as, cement, steel, wood, and glass,
are associated with significant environmental costs related to their
extraction, manufacture or harvest. Straw on the other hand is often
considered a waste product and a nuisance, and being a by product
of raising crops for human food does not place any additional burden
on the environment. The resulting buildings would provide better
insulation and be better able to withstand stresses resulting from
earthquake than the typical brick and mortar construction used in
the developing world. Converting straw to a building material would
save resources, provide the farmer with another source of income,
and for every ton of straw preserved in this fashion approximately
894 lbs. of carbon would be sequestered for the lifetime of the
building.
View
the Strawjet Photo Gallery |
