I was quite surprised while watching the biographical documentary of Dr. Percy Julian on a NOVA special. It appeared that soybeans were intensively studied as a plastic source at the Ford Motor Company, as Henry Ford believed strongly in the power of the soya plant for industry. In fact, the Soybean Car , bearing a soya-derived plastic body was unveiled in August of 1941.

We were deriving plastics from biological materials over 65 years ago? What an amazing head start! Where did that technology lead?

As Ford shifted much of the surrounding industries, this soybean car was not an isolated case of biological components developed for polymer chemistry in industry. Prior to WWII, it appeared that industry was quite involved with using our agrarian culture to develop plants for technologies. How did we get so sidetracked (again) into using primarily petroleum products for all of our plastic needs? We must conclude that following WWII, the USA and many other countries had become “industrialized” and had discovered the wonders of synthetic chemistry. Hence, industry no longer needed contact with agricultural-driven economies, and conversion of biomaterial to technological material was replaced by synthetic methods.

What is the connection to photovoltaics? Well…

...many new entrepreneurial PV researchers are promoting a plastic substrate for flexible photovoltaic devices. What these companies don’t tell the community is that traditional PV modules have guaranteed lifespans of >20-25 years set by industry, and these plastics would be unlikely to sustain that exposure period due to decomposition problems when exposed to ultraviolet light. This encourages a disposable market much like our trade in microelectronics and computers (ever found a laptop that lasts 25 years?). On top of that, almost all modern plastics are derived from petroleum or coal refined products.

So, if we’re not burning the coal/oil as fuel, it’s a plastic source material. This is doubly complicated then, as the plastic PV industry would encourage intense disposable consumerism of materials that require fossil fuel consumption for both a fuel source in the refining and polymerization process, and as feedstock for the substrate materials. This suggests that the math must be done to confirm that the energy input could be regained within the short lifespan of a plastic PV device.

Traditionally, the PV industry is quite good at running the numbers on such assessments. For example, in a silicon purification process SiO2 (silica) is reacted with C (black carbon) in a furnace to yield silicon and CO2 gas. However, both the energy consumed in the furnace and the CO2 produced can be replenished within 3-5 years of the solar cell’s lifespan.

I don’t suggest that we do away with plastics for everything, I just don’t think they are well-suited for all tasks of technology. Unfortunately, in the case of a flexible plastic PV module, the plastic will likely be non-recyclable due to the metals used in making the film conductive or inserting the light-absorbing semiconductor. So we have just created another technology where the product is pure solid waste following a brief consumption life span. (This is related to the principle of Environmental Technology that I’ve mentioned before).

I am also curious, is there a way to supplement our typical plastics with those made from renewable sources, such as plant materials? I have heard rumors in the popular science literature of a “green” wave of polymer chemistry based upon plant stock. I would be interested to learn more.

By the way: Dr. Julian was an extremely innovative chemist and entrepreneur in the 20th century. He was involved in exploring the potential of the soya plant for any number of applications in health and technology while working as a head scientist for the Glidden paint company. These discoveries included using soy to produce synthetic steroid hormones, water-based paints, fire retardants, and paper coatings. In addition to being a respected and influential scientist, he is widely recognized as a vitally important African-American contributing the field of science and business.

• Image credited to the Wikipedia entry for Soybean