Monday, June 21, 2010

Growing Bricks

I recently came across an article about a professor who has come up with a novel way to make bricks. Concrete in general and bricks in specific require a lot of energy to produce. The raw materials have to be heated to very high temperatures to achieve the right chemical reactions. All that energy costs money and has a high environmental impact. Professor Ginger Dosier has come up with a possible solution. She fills a mold with sand and introduces a special bacteria and a solution containing urea, a common waste product. Over the next four to seven days, the bacteria consumes the urea and produces calcium carbonate, locking the sand particles together and creating a sort of synthetic sandstone. All this happens biologically at room temperature.

Of course, I am a bit of a chemistry geek and happen to know that urea ((NH2)2CO) and sand (usually SiO2) don’t contain any calcium, which makes the formation of calcium carbonate (CaCO3) a little tricky. However, I am willing to assume that there is some sort of nutrient broth introduced that the article above failed to mention. If any of you out there have any further details on this, I’d love to hear them.

I find this technology promising as concrete production is responsible for about 5-8% of greenhouse gas production worldwide. Most of those gasses are produced as a result of the heating of the raw materials used in concrete, but the chemical reactions that produce concrete also produce carbon dioxide. Fortunately, there are others tackling this problem as well. In England, engineers have come up with a type of concrete that is based on magnesium silicates instead of calcium carbonate. The interesting thing about this concrete is that it not only uses less heat to produce, but it actually consumes carbon dioxide from the atmosphere as it cures, making it carbon-negative.

Of course, it may be years before these products become widely available as materials like this need to undergo extensive testing in order to develop standards for mix design and production. Then those standards need to be adopted by regulatory agencies. That all takes time. However, the Italians have discovered a kind of concrete that actually scrubs the pollutants from the air. The benefit of this is that it is only a minor modification of existing concrete and thus doesn’t need extensive testing. They discovered that when titanium dioxide, which is a white dye often used in foods, is mixed in with the concrete, it reacts with the sunlight, producing a catalytic reaction that breaks down carbon monoxide and nitrogen dioxide in the atmosphere. While it isn’t a cure for carbon dioxide emissions, it can help with air quality.

Thursday, June 17, 2010

Combating Desertification

Humans use up soil. It is a sad fact, but it is true. The very basis of our food system is a substance that gets depleted but rarely replenished. Part of the problem is in how we think and how we view soil. Most people think of soil as a reserve of nutrients for plants to take from as they grow. In return, we put nitrogen, phosphorus and potassium back, thinking that it replenishes what we took out. It doesn’t. Soil is a living organism that is fed by a continuous input of organic material, mostly in the form of dead plant material and animal waste. When nutrients, including organic material, are removed from the soil without properly returning it, the organisms in the soil starve and eventually die. Healthy soil has several inches of organic matter that act like a sponge when it rains, soaking up moisture quickly when it rains and reducing runoff. As the soil dies, it also loses the ability to store water, eventually leading to a process called desertification. By some estimates, 38,000 square kilometers of arable land are lost per year to desertification.

Biologist Allan Savory, who won this year’s Buckminster Fuller Challenge, set about tackling the problem of desertification decades ago. In his native country of Zimbabwe, this process has been turning grasslands and savannahs into deserts. In addition to poor farming practices, desertification is achieved by overgrazing the land to the point that it cannot recover and is left a dry, parched landscape. The new landscape is no longer productive from a human standpoint, but is also detrimental from a climate change standpoint, as it is much more prone to fire and no longer sequesters carbon in the soil. He began with a holistic approach, studying how natural grasslands support vast herds of ungulates. He assumed that the grasslands evolved with their herd animals as part of the same ecosystem. Then he looked at the difference between how natural herd animals graze the land and how domesticated animals graze the land. What he found was counter-intuitive.

In the wild, animals used to travel in vast herds, much like the wildebeests do today in Africa. The bison herds in America were equally massive. What the wild herds DON’T do, though, is stay in one place and continually graze the same grasses over and over. The grasses need time to recover between grazings. He also found that huge herds of ungulates till up the ground as they walk on it, distributing and trampling in the organic material they are depositing. He set out to emulate this method of grazing by increasing herd sizes and more closely managing how they migrate across the land as they feed. Grass keeps a reserve of energy in its roots. When it is grazed to the ground, it uses those reserves to put up more leaves. When the large wild herds graze, they eat the old vegetation until it is depleted and then move on to find more food. The grass puts up new leaves a few days later, after the herd has left. When a cow grazes in one area, it prefers to eat the tender young leaves. By doing so, it hinders the ability of the plant to recover fully.

Savory started helping cattle ranchers increase the size of their herds, a process that nearly no one thought would work. Then he helped them manage how the herds roamed across the land, fully grazing one area out and then not returning to the same area until it was fully recovered. The grasslands recovered and the grasses started growing back in, creating a healthy ecosystem. Eventually, the water retention of the soil increased and springs started to develop. Stream flows increased and the whole desertification process was reversed.

Monday, June 14, 2010


Anyone who has spent any time truly studying nature has probably noticed that for nearly every piece of technology we have, there is an analog in nature. The interesting thing is that the analogs in nature often accomplish what we are trying to accomplish more elegantly, simply, and at a lower resource cost than what we humans can seem to manage. Some of the examples are pretty interesting. We came up with air conditioning; termites in Africa managed to achieve a constant temperature and humidity with very little energy input, using architecture. In our current world, the lack of availability of fresh water is a growing problem worldwide. There is only so much to go around. However, there is a nearly limitless supply of water in the oceans, if only there was a way to remove the salt. Desalinization plants are costly to build and operate. However, your own body has a solution. The salinity of blood is very similar to the salinity of seawater, and we can’t afford to lose all that salt. So kidneys filter the blood and remove excess water and impurities while leaving most of the salt behind. In fact, the efficiency of this process is why we can’t drink seawater. The salt would just build up in our bodies. The examples go on and on.

More and more scientists and engineers are now working together to study biological systems in nature and how they work. Most importantly, they are trying to find ways to emulate those processes through a process called biomimicry. Biomimicry is the study of nature with an intent to copy nature’s solutions and apply them to human problems. One recent high-profile example is gecko tape. Scientists have studied how geckos use the tiny hairs on their feet to stick to slippery surfaces, like glass, and used this to make a tape that is incredibly strong but doesn’t use adhesives. Instead, it uses millions of tiny hairs. Each hair attracts surfaces through a force called Van der Waals forces, which are actually very weak forces. However, by having millions of hairs, the forces add up to a very strong attraction. The result is tape that will hold huge forces, even in wet conditions, without leaving a sticky residue. For more information on the promise of biomimicry, I highly recommend watching Janine Benyus’ two talks to TED on the subject here and here. Biomimicry offers new and exciting ways of solving humanity’s problems.