Until recently, a huge plume of black smoke could often be seen billowing from Winfrida Mgaya’s rice fields.

The 51-year-old farmer from Makifu Village, in the Iringa district in Tanzania’s southern highlands, would routinely set ablaze piles of rice straw as she prepared her farm for the next planting season.

Like many farmers, Mgaya used fire to destroy waste straw, spewing environmentally damaging carbon into the air and risking the blaze spreading into other people’s fields.

Then she discovered she could turn her surplus straw and rice husks into something more valuable: “bio-coal” which can be used to fertilise crops to boost harvests or as an energy source for cooking.

“It was a big surprise to me when I first learned about this technique,” she said. “I didn’t expect one day I would use the rice husks profitably.”

Mgaya is among more than 15,000 rice farmers in Tanzania’s southern highlands who are learning how to use rice husks and straw to produce bio-coal under a three-year project implemented by the Royal Norwegian Society for Development (Norges Vel) and the Rural Urban Development Initiative (RUDI), a private-sector organisation dedicated to assisting small-scale farmers.

Using special ovens, the farmers carbonise the rice-husk waste, which can then be turned into energy-rich bio-coal or pressed into briquettes to be burned for cooking. The surplus heat and gas produced during the carbonising process  – today largely carried out using firewood – can also be used as energy.

Before she started using husks to improve the soil on her farm, Mgaya, a frail-looking mother of six, was reaping dismal harvests of between six and eight bags per acre. Now “I mixed the converted wastes with soil, and the new method was very effective,” she said. “In the end I was able to get 14 bags of rice.”

The idea of finding a sustainable use for rice waste was partly in response to another initiative aimed at helping improve the lives of Tanzania’s rice farmers.

Since 2007, RUDI and Norges Vel have been working with small-scale rice growers to increase incomes, strengthen the role of women, secure market access and get funding through micro-credit.

Growing more rice means producing more rice husk – Tanzania produces more than 3.2 million metric tons of it each year. To dispose of the waste, farmers often leave it heaped in great mounds to rot, burn it or dump it in the forests, all of which can create environmentally damaging carbon emissions.

But turning the husks into fertilizer can be good for the soil and the environment, Norges Vel researchers say. According to Johan Ellingsen, leader of the bio-coal project, once added to acidic and sandy soils, the bio-coal can hold in nutrients and prevent them from being washed out of the soil during rainy seasons.

When the $800,000 project, which is funded by the Nordic Climate Facility, launched in 2013, farmers who joined were told to establish a few demonstration plots on their land and apply the bio-coal to those while still using conventional fertilising methods on the rest of their crops.

“We have seen a visible increase in crop yield in the fields where bio-coal had been used,” Ellingsen said.

The bio-coal also acts like a sponge, researchers say, storing water in the soil for longer. “With this method the rice can grow well even in dry conditions,” said farmer Mgaya. “I don’t have to worry about shorter rains anymore. I only need enough water in the soil, that’s all.”

Local scientists say using rice waste in this way also helps offset the high cost of buying chemical fertilisers.

One problem, however, is that most bio-coal is currently produced using firewood as an energy source. To try to change that, project leader Ellingsen said Norges Vel has teamed up with TATEDO, a Dar es Salaam-based energy development organisation, to develop more efficient ovens that burn using bio-coal itself.

This article is published in collaboration with Thomson Reuters Foundation trust.org. Publication does not imply endorsement of views by the World Economic Forum.

To keep up with the Agenda subscribe to our weekly newsletter.

Author: Kizito Makoye is a freelance correspondent for the Thomson Reuters Foundation.

Image: A farmer sets rice seedlings into paddy fields at the Mwea Irrigation Scheme in Kirinyaga district, about 100 km (62 miles) southeast of Kenya’s capital Nairobi. REUTERS/Noor Khamis