The Green Thumb: Bamboo U, Part One
This month, we’ll begin a three-part series that will take an in-depth look at one of the most amazing natural materials on earth: Bamboo.
Trust, but verifyWhen I was studying architecture in college one of my professors told us an interesting story. He had spent the morning inspecting the forms for the foundation of a custom-built house he designed, making sure all was in readiness for the concrete pour to take place that afternoon. With everything in order, he parted, leaving the supervision of the pour to the general contractor. About a half-hour later, he realized he had left his briefcase at the job site so he headed back to retrieve it. To his amazement-and displeasure-he returned to find that in the short time that had passed, all the steel re-bar had been pulled out of the formwork and was in the process of being replaced with bamboo poles of a similar diameter. As a cost saving measure, the GC had tried, but failed (due to a twist of fate), to save the cost of the expensive steel re-bar by substituting cheaper bamboo poles.
Yankee ingenuityOf course, this use of bamboo may seem farfetched, but in a large portion of the world, bamboo re-bar used for concrete reinforcement is just one of bamboo’s many uses, particularly in developing nations. If I had to guess, the GC probably was a “Seabee” (or “CB,” an acronym for “Construction Battalion,” the Navy’s version of the U.S. Army Corps of Engineers) in the Pacific Theater during WWII. With steel in short supply and/or unavailable, Yankee ingenuity stepped in and made use of what was readily available in abundance in the tropical and sub-tropical climates of the south and central Pacific, bamboo. To give concrete foundations, runways, etc., the tensile strength needed to resist tension forces (stretching), bamboo poles were found growing naturally nearby. This kind of resourcefulness helped the United States win the Pacific war, but, unfortunately for the hapless GC of my story, it was not to code on the Gold Coast of Long Island.
If this story sounds incredulous to you, consider the fact that bamboo is one of the strongest building materials in the world, with a tensile strength comparable to steel. That’s very significant considering the fact that steel has the highest strength-to-weight ratio of any building material. In resistance to bending forces, steel is 10 times as strong as masonry and 20 times as strong as wood. In fact, bamboo has a strength-to-weight ratio surpassing graphite. In compression (squeezing), bamboo outclasses concrete having a compressive strength of up to 52,000 psi.
Sea of BambooContrary to popular belief, bamboo is not a wood species at all, but rather, it is a member of the grass family. For thousands of years Asian cultures have employed bamboo for a wide variety of uses. Over one billion people live in bamboo houses and 25 percent of the world’s population relies on bamboo for their daily existence. In the southern Chinese province of Hunan, extensive bamboo forests have given the region the title: “The Bamboo Sea.” It is from this area of China that most of the bamboo for the North American market is grown and processed into finished products.
Native to diverse climates, bamboo can be found throughout most of Asia, South America, sub-Saharan Africa, Northeast Australia and the Southeastern United States. Bamboo is the most diverse group of plants in the grass family and the most primitive sub-family; it has been around for a very long time. A wood-like grass, some species can grow up to two feet a day and reach 160 feet in just six weeks. In comparison, a 60-foot tall tree requires about 60 years to grow to that height! Talk about “rapidly renewable”! One species grows to 180 feet and is one meter in diameter.
Wood of the PoorIn India bamboo is known as “the wood of the poor.” In China, where it is most abundant, it is referred to as “friend of the people.” The Vietnamese simply call it “brother.” There are between 1,100 and 1,500 species of bamboo growing in both tropical and sub-tropical climates. Some species are deciduous (shed their leaves) while others are evergreen. It grows at elevations as high as 4,000 meters in parts of China and the Himalayas. Harvesting bamboo is not a threat to the beloved panda that is native to these higher elevations. Pandas eat a species of bamboo that grows only in the higher elevations, not in the lower elevations where the most widely cultivated bamboo grows. Known as Mao Zhu or, more commonly Moso Bamboo, the Japanese name for it, Moso Bamboo grows China’s lowland Hunan province; the Bamboo Sea.
Bamboo is distinguished by four elements:
• A woody culm (stem)
• Complex branching
• A robust rhizome system
• Infrequent flowering
Each year a bamboo plant can produce several full-diameter, full-length culms. In its lifetime a bamboo plant can produce up to 15 kilometers of usable “pole” with diameters up to 30 cm. Wood, on average, has a 2 to 5 percent annual increase in “biomass” while bamboo claims a 10 to 30 percent annual increase. Bamboo is as light as balsa wood yet as strong as steel. This great strength is derived from the cellulose fibers that run the length of the stalk. Bamboo’s flexibility is derived from Ligmin. It is extremely hardy as well. In fact, it was the first plant to grow in Hiroshima after the atomic bomb was dropped on the city in August 1945. If you cut one stalk, two will grow in its place without any need for fertilizer.
Worldwide AppealAnnually, the world trade in bamboo and rattan is about $5 billion. It is primarily harvested in developing countries by women and children who live at or below subsistence levels. In Bangladesh – the poorest nation on earth, 73 percent of the population live in houses almost completely fashioned out of bamboo; walls, window frames, ceilings, pillars, rafters, roofs etc. In rural Asia, it is used to construct pontoon and suspension bridges and is very useful in providing fast vegetative cover for deforested areas, due to its rapid growth. It is also used for road and river embankments as a stabilizer and check against soil erosion. Taiwan exports about $50 million worth of bamboo shoots annually and the Philippines has a booming furniture industry. For its domestic paper industry, India uses 2.2 million tons of bamboo and in Java, 20 different musical instruments including wind, stringed and percussion, are made from bamboo. Anthropologists believe that the flute was invented by early man using a hollow bamboo stem to make sounds, and, eventually, music. In Costa Rica, from a bamboo plantation of only 60 hectacres (150 acres), each year 1,000 houses are built of bamboo.
Next month-in Part Two, we’ll continue to investigate the many wonders of bamboo and its growing use as a “green” building material.