Watching as the Soil Breathes

In the timescales of history, the discovery and scientific acceptance of climate change are very recent events. The scientific discovery of climate change began in the early nineteenth century when the natural greenhouse effect was first identified. Researchers then dared to venture that low levels of carbon dioxide might explain the ice ages of the past. Later, at the turn of the last century, the idea that humans might be responsible for climate change was proposed by Svante Arrhenius, but it was deemed faulty and brushed aside at the time. It took until the 1960s for people to be convinced about the warming effect of carbon dioxide. Only then, with the advent of the environmental movement, did scientists began to look closely at changes in carbon dioxide levels over the ages and the factors which contributed to those changes.

The levels of carbon dioxide in the atmosphere are instrumental in tracking climate change – but they are not the only parameters by which scientists predict and track global warming. The burning of fossil fuels releases carbon dioxide into the atmosphere and causes it to heat up, and this heating triggers noticeable changes in other processes too.

For example, increased atmospheric temperatures have an effect on soil respiration, or the production of carbon dioxide when soil organisms respire. This natural process, in which carbon dioxide is released from the soil into the atmosphere, is also in a “positive feedback system” with global climate change – which means that soil respiration rates can be affected by climate change, and in turn, respond by accelerating climate change. Ben Bond-Lamberty and Allison Thomson, researchers at University of Maryland’s Joint Global Change Research Institute, have found that soil respiration has increased by about 0.1 percent per year in the two decades from 1989 to 2008. Thus, as the atmosphere becomes warmer, plants and microbes in the soil release more carbon dioxide.

The link between carbon dioxide levels in the soil and global temperatures makes data regarding the carbon dioxide levels in the soil very valuable, as it can advance our understanding of global climate change. I visited the Electrical Sciences Block to interview Vaibhav Pratap Singh, a research student in the department who has worked on a wireless sensor network that can give us just this data by monitoring the levels of carbon dioxide in soil.

 

Vaibhav with the soil carbon dioxide sensor module.
Vaibhav with the soil carbon dioxide sensor module.

 

Vaibhav’s device measures and wirelessly communicates the carbon dioxide levels in the soil. Using these measurements, he can throw light on the variations of soil carbon dioxide levels with seasons, temperature conditions and geographical locations. For his project, Vaibhav won the Bayer Young Environmental Envoy 2013 (BYEE 2013) competition, which is held in cooperation with the United Nations Environment Programme (UNEP), and participated in the Bayer environmental summit in Germany, from 10th November to 15th November 2013, along with forty-eight others from eighteen other countries.

At the start of the interview, I ask Vaibhav to explain how the device was built and what it does. He explains that the set-up for the device consists of a carbon dioxide sensor chamber covered with a membrane that is “semipermeable” – it allows only certain gases to pass through it and keeps others out. The sensor measures the levels of carbon dioxide and converts these measurements into electronic signals. But there is another hurdle here: the electronic signal has to be transmitted over long distances since it is impractical to collect data from the forest or grassland where the sensor is.

 

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Vaibhav solved this problem by employing a wireless network which sends data to be recorded on remote servers. When these remote servers are interfaced with a personal computer, one can analyze the data and generate graphs that depict the variation of carbon dioxide in the soil.

Like most technology that is developed for remote areas, Vaibhav’s soil carbon dioxide sensor comes with a familiar challenge: power. The sensor must draw its energy from somewhere, and in the far-away areas where it is to be deployed, the most readily available source of energy is the Sun. Vaibhav explains that the carbon dioxide sensor is powered by a battery, and the device is equipped with a solar panel so that the battery can be recharged. The device is also fitted with a pump. This, Vaibhav tells me, is because the device is designed to monitor not just the levels of carbon dioxide in the soil, but also its levels in the atmosphere.

Has the sensor been used yet to collect data? Vaibhav answers, “Yes, we conducted our first round of data collection from 28th March to 8th April in 2012. We buried the sensor chamber at a depth of 20 centimeters. Every three hours, the levels of carbon dioxide in the soil were measured. We found that the levels of carbon dioxide in both the soil and the atmosphere increase with an increase in temperature,” Vaibhav adds. Pointing to the graph that shows the variation of carbon dioxide levels with time, he continues, “You can see this by the spikes at 10 a.m., 1 p.m. and 4 p.m. These spikes are linked to the role of microbes in breaking up carbon compounds in the soil to produce carbon dioxide.”

He elaborates, “After a reading of soil carbon dioxide level is taken, the pump is turned on. The pump pushes out the air that is already in the sensor chamber and pumps in air from the atmosphere. The sensor then measures the level of carbon dioxide in the atmosphere. After this is measured, the atmospheric air is pumped out. There is also a valve that is built into the device to enable calibration. After the air is pumped out of the chamber, the valve is opened, and this brings any remaining air in the chamber in contact with soda lime, which absorbs all the carbon dioxide.

Now, the levels of carbon dioxide in the chamber are known to be zero, and the sensor output can be appropriately calibrated.”

So what’s next? Vaibhav answers, “Right now, we’ve finished designing the hardware for the project and are in the experimental phase of it. One challenge for us is to reduce the power consumed by the sensor so that its battery lasts longer. This is particularly important for long–term experiments. We also want to be able to receive data from the sensor on mobile phones, for which we’ll have to incorporate GSM. Another major challenge is to make the measurement precise and accurate, for which we have to eliminate errors in calibration. The goal of the project, ultimately, is to build a low-power, low-cost device to study how the level of carbon dioxide in the soil varies with seasons,temperature and geographical locations.” Vaibhav hopes to receive support from Bayer in taking his project further. Bayer’s international presence could also help them collect data from different parts of the world. Vaibhav envisions his product as one that can help a spectrum of people across the world, from environmental researchers and organisations to agricultural universities and farmers.

Environmental consciousness and technological advancements can make for strange bedfellows. And especially at a university like IIT Madras, which has a beautiful and fragile natural ecosystem in tenuous equilibrium with rapid development, Vaibhav’s research and the recognition it has received are an encouraging affirmation that science could possibly marry the two.