> *Sarah Billington
> Oct. 14th*

> *Bio-composites: Building a Sustainable Future*

> Sarah Billington is Associate Professor in the  Department of Civil
> and Environmental Engineering at Stanford University, an
> interdisciplinary department committed to finding solutions to the
> sustainability challenges of our time and covering three main areas,
> the built environment, atmosphere and energy, and the water
> environment.

> 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, she
> and her colleagues received a two-year Environmental Venture Projects
> grant from Stanford's Woods Institute for the Environment to develop
> 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 her
> 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 main 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 tint.

They haven't looked into using used clothing as a source of fiber for composites.

They don't yet know if termites will eat the stuff.

Without a protective coating or fiber treatments the stuff absorbs water and loses stiffness.

Tian Harter