Sweet Buildings (AMSEN)

Alan Anderson

Even in some of the more traditional academic areas, such as civil engineering, RISE students are finding innovative approaches to ongoing needs. For example, John Mwero, a PhD student at the University of Nairobi, faced the familiar challenge of building new, high quality buildings at lower cost and with reduced environmental impact.

When John was considering a PhD in engineering, he looked at a problem of significant dimension. Virtually all new buildings in Nairobi are built of concrete, which accounts for 15-20 percent of the structure’s cost. Concrete is relatively expensive, and requires large amounts of energy to produce. He started thinking about ways to reduce these costs, and found numerous suggestions that various raw materials, including agricultural wastes, might be used to replace some portion of the concrete in buildings.

Where John grew up, in Kilifi, near Mombasa, sugar cane was a central feature of life. His mother kept a garden of stalks near the front door of their house so she could cut a bit of cane to chew on when she went out. A sugar cane mill was located not far from the house, and sugar cane dominated the landscape. Huge piles of stalks and leaves – bagasse – surrounded every mill.

Disposal of this bagasse has become a substantial environmental problem. Some of it is useful as mulch for farmers, and some is bagged as fuel for boilers – indeed, the price of sugar is now so low that the sale of bagasse can be more profitable than the sale of sugar. And recently sugar plants have been burning the bagasse to reduce its volume, using a controlled spray technique to reduce the smoke. But burning still leaves large piles of ash.

John began a literature search and found suggestions that such organic residues might find a new application as a substitute for concrete. But how much could be used? He began some early tests, making small cubes of concrete and sugar cane ash. His early results were encouraging. Although large amounts of ash would weaken the concrete, small amounts – about 6-8 percent – would actually bring a slight improvement in strength. He found similar results with rice husks.

“I’m very much encouraged,” he said. “Bagasse is very available, and would reduce the demand for cement, which is very energy intensive to produce. This might also mean extra revenue for the farmer eventually, and solve the problem of disposal of bagasse. And we may be able to find ways to reverse the loss of strength at higher proportions.”

John has the support of his four supervisors in this project, and he sees better linkages between academic engineers and private firms as essential to innovation. “People in companies have a very low opinion of people in academia,” he said. “I’ve had people tell me, ‘You know, an engineer with a masters is not necessarily the best engineer.’ When someone comes from a university and goes into a firm, it’s like starting out fresh. Academics lose track of the cutting edge of industry. We have to reduce that gap by having more people in industry who are also teaching. If students are taught by someone actually doing work on the ground, they will be much better engineers.”

In John’s case, one of his supervisors is a consulting engineer for a large firm in Nairobi, where he also worked for a year before starting his MS work in 2003. “I would also like to be a consulting engineer, because then I can make a good link between the theory and the practice,” John told me.

At the same time, he enjoys teaching, which he began last year, and would like a permanent position on the faculty. He acknowledges a problem in classes that are too large (60-90 students) to allow discussion or attention to individual students. In the Kenyan system, engineering majors in a particular field all attend the same classes together for the five years of the program. Civil engineering attracts few women, he says; in his class of 60 graduating students, only three were women. He attributes this in part to tradition and in part to the large class sizes, where aggressive students have an advantage.

See update here.