The kapok, or Ceiba pentandra, is a remarkable tree that populates rain forests in South and Central America, West Africa, and Southeast Asia. Mature kapoks can reach 150 feet in height and have trunk diameters of up to 9 feet. Kapoks have a distinctive umbrella-shaped canopy that accommodates many bird, frog, and plant species. And they also may be a viable alternative energy source for humans.
Researchers at the University of Maryland and the University of Colorado Boulder who analyzed fibers and seed pods from the kapok tree found that they would make optimal electrodes for next-generation microbial fuel cells (MFCs). MFCs use electrochemically active bacteria to process organic matter and generate power as a result. The researchers claim that the kapok fibers, given their porosity, lightness, and large surface area, provide the ideal surface for the colonization of such bacteria.
The scientists carbonized the fibers in a tube furnace to make the bacteria on them electrically conductive. "The direct carbonization of low-cost and naturally available hollow kapok fiber provides an advantageous alternative to non-renewable solid macroporous carbon cloth electrodes,” Liangbing Hu, an assistant professor of materials science and engineering at the University of Maryland and a co-author of the related paper, told Materials Today. "It is much cheaper, lighter, and has much higher gravity energy density.”
The carbonized kapok offers many environmental advantages over conventional MFC materials, which the researchers say are expensive and unsustainable. Nevertheless, the kapok is a critically important tree that is currently being harvested regularly for use in pulpwood and plywood products. One solution could be cultivating the tree's seed pods for fiber, leaving the tree itself intact. Perhaps the development of kapok-based MFCs will motivate the increased collection of seed pods, thus discouraging the wholesale destruction of the trees themselves.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.
Image courtesy Flickr user Don Faulkner via a Creative Commons License.