> *Sarah Billington
> Oct. 14th*
Building a Sustainable Future*
> Sarah Billington is Associate Professor in the Department of
> and Environmental Engineering at Stanford University, an
> interdisciplinary department committed to finding solutions to the
> sustainability challenges of our time and covering three main
> the built environment, atmosphere and energy, and the water
> Sarah's research in structural engineering focuses on the
> investigation of high performance, sustainable materials and their
> behavior, design and simulation in structural systems. In 2004,
> and her colleagues received a two-year Environmental Venture
> grant from Stanford's Woods Institute for the Environment to
> artificial wood that is both durable and recyclable. The research
> team focused on a new class of construction material called
> biodegradable composites, or "biocomposites"-glue-like resins
> reinforced with natural fibers that are made from plant fibers and
> recyclable polymers.
> Sarah will give an overview of her work with bio-composites - in
> words "a great opportunity to make products that serve a societal
> need and respect and protect the natural environment."
Sarah began by explaining that cement manufacture gives off roughly 5%
of our CO2 emissions, and 40% of the space in our landfills is used by
construction and demolition debris. She came into the equation looking
for a way to do something about that. One of her colleagues is looking
for a way to make use of the methane from wet landfills and waste water
treatment plants. Together they are developing ways to recycle used
materials back into new construction materials.
Fiber reinforced composites consist of a matrix and a fiber bonded
together into a material that has a better mix of qualities than
either alone. Sarah's composites use PHB (Polyhydroxybuterate) for the
matrix. These are created by bacteria that store the carbonfrom
methane as PHB in their cells. The PHB is then extracted from the
bacteria and can be formed into pellets, which are combined with fiber
to make composites.
The composites she has made to date have similar properties to many
types of wood. They tend to be not quite as stiff, and are expected to
melt at about 180 ' Centigrade. The stuff can be molded into
almost any shape. At this point it is still expensive compared to
wood, but with further research and understanding of the material
behavior, they hope to find ways to bring costs down.
PHB could also be used for making biodegradable plastics. The
requirements for getting PHB is a supply of methane and a digester for
the bacteria to work their magic in.
They are currently working in various ways to have the bacteria produce
PHB more efficiently. Sarah is hopeful they will find applications for
PHB matrix materials that will be competitive in the construction
marketplace within ten years.
During Q&A a number of points came up:
Cow manure could be used to provide the methane to grow PHB.
Peanuts for packaging might be an excellent market for the PHB.
The composites tends to be heavier than equivalent plywood, and not
quite as stiff.
They have figured out how to make it transparent but it has a yellowish
They haven't looked into using used clothing as a source of fiber for
They don't yet know if termites will eat the stuff.
Without a protective coating or fiber treatments the stuff absorbs
and loses stiffness.