As he is installing exhaust fans on his latest project—a walk-in solar tunnel dryer for betel nut in Jhapa District—Babu Raja Shrestha describes with infectious enthusiasm the sheer magnitude of the sun’s energy. During the course of an average day, each square meter of land in Jhapa receives approximately five kilowatt-hours of solar insolation. This is essentially the same amount of energy generated by a small diesel generator running for a couple of hours. Of course, harnessing solar energy to do work—whether through photovoltaic cells or through thermal technologies—is difficult and necessarily somewhat inefficient. Nonetheless, the vastness of the energy resource that the solar dryer taps into is somewhat of a marvel, underlined by Shrestha’s boyish energy.


Babu Raja Shrestha.

Trained as an aeronautical engineer in the Soviet Union during the 1970s, Shrestha has had a colorful career. Among other things, he has worked on projects to promote electric tempos in Kathmandu and LED “solar tukis” for rural household lighting, and for a time he was in charge of Biratnagar’s solid waste management program. In recent years, he has worked independently on a variety of small-scale agricultural mechanization technologies that use renewable energy sources. His eclectic choices in work seem driven by an incessant curiosity and impatience to get things done. He starts his days before sunrise and is constantly on the move, fixing things, thinking about how they could work better. As he explains it, “I’m not inventing new equipment. I’m just doing adaptive research, taking ideas developed elsewhere and applying them to our environment.”

His farm, located in a sleepy Tharu village on the outskirts of Biratnagar, is his base of operations. He grows mushrooms there and has developed a precise science of cultivation by innovating on conventional techniques. For example, he pasteurizes the rice straw that the mushrooms are grown on, using an insulated vat of water heated on a rocket stove, which cuts down on fuel use and preserves many of the beneficial microbes that help mushrooms grow. Shrestha’s office in the farm house is full of designs and pieces from past projects, including one for a wind-powered irrigation pump, a technology he thinks holds great potential for Terai areas with strong dry season winds and a high water table.

Installing the new exhaust fans in the solar tunnel dryer.

Shrestha first worked on solar dryers in the mid-’90s. Since then, he has fixed many of the initial glitches and cut down the costs. He built several panel-like units on his farm for drying mushrooms and other agro products. Currently, one 6 meter by 2 meter unit can dry 45–60 kilograms of wet material at a time and costs about NPR 290,000.

Preparing the betel nut for drying.


Shrestha’s latest dryer is being built at the Shree Krishna Betel Nut Cooperative in Budhabare, a quiet VDC in northern Jhapa where betel nut palms are the dominant feature of the landscape. The area is covered with plantations, most owned by smallholders, who intercrop the betel nut trees with a variety of other crops. Black pepper vines grow up the trunks in jungly profusion, while bananas, turmeric, ginger, and shade-loving vegetables like hot peppers and taro are planted below; rice and corn fields are also ringed with the trees. At harvest time, farmers cut the fruit using sickles attached to long bamboo poles, or they hire young men from West Bengal who climb up and jump from treetop to treetop.

Most growers in Jhapa sell their nuts to Indian traders in unprocessed form, since they lack drying technology and direct sun-drying is labor intensive and slow, leaving the nut prone to fungal attack.  Local farmers also face tough competition from Southeast Asian betel nut, which is legally imported into Nepal and then smuggled into India to avoid high tariffs. (Nepal’s Ministry of Commerce and Supplies recorded the import of over 64,000 metric tons of betel nut in 2013, which, if consumed domestically, would be nearly two and a half kilos per Nepali.)

Shrestha’s betel nut dryer in Budhabare resembles a greenhouse, with plastic sheeting covering a steel frame. It is based on a prototype from Kerala that he read about, developed to dry coconut. On the southern side is a glass lean-to structure that collects hot air, which is then blown through the greenhouse using solar-powered fans. Stacked inside the unit are 16 metal racks, which together can hold about one metric ton of wet betel nut. Khib Nath Gautam, the cooperative’s secretary, explains that the new dryer will allow Nepali farmers to process more nuts themselves, improving quality and increasing the prices that the betel will fetch.

Glass panels collect hot air for drying the nuts.

The solar tunnel dryer.

Over the next few weeks, Shrestha will be testing the dryer using thermometers and instruments to measure moisture placed throughout the unit. If efficient, he hopes that it will be approved for government subsidization through the Alternative Energy Promotion Centre, part of the Ministry of Science, Technology and Environment, which provides a 50 percent subsidy for certain technologies, up to NPR 1.5 lakh. The total cost of Shrestha’s project is about NPR 10.6 lakh, which will otherwise be covered by the Cooperative and the Nepal Betel Nut Farming Development Organization, a growers’ association.


Shrestha would like to build more dryers for Nepali betel nut farmers—who produced nearly 12,000 metric tons in 2013, mostly in Jhapa, southern Ilam, and Morang—but he also hopes for wider application. The technology could be used for turmeric, ginger, mushrooms, vegetables, even rice. Because the units are modular (their length can be adjusted to the scale of production) clients can start with a smaller investment and gradually build up. He expects that the price of the greenhouse dryer will fall considerably, since future units will not require research costs.

Still, the issue of cost seems important. Is the vision for mechanized agricultural development, renewable energy-based or not, relevant for Nepal’s poorest farmers? Shrestha says that labor-saving technologies are becoming more important in villages where labor is scarce due to increasing out-migration. And wind and solar technologies have small running costs relative to fossil fuel­–based alternatives. But they also require significant up-front investment, which he acknowledges is a problem.  He also says that, too often, donor-driven solar drying projects have targeted farmers who are too far from markets for the projects to be viable. For the time being, solar drying units like the one in Budhabare are likely to be most useful for farmers’ cooperatives with good market access and large commercial growers who can afford them.

When asked about the term “appropriate technology,” Shrestha, who has just returned to his peaceful farmhouse from Jhapa, pauses and replies, “Appropriate means that you can manufacture, that you can assemble, that you can maintain it using locally available resources. It also means that it matches the need of the user—it helps them do something they want to do.”

Cover photo: A basket of betel nuts and a nut slicer. Denish C/Flickr. Republished under CC license BY-NC-ND 2.0.