Innovative biochar-producing gasifier stoves improve livelihoods, landscapes

A farmer uses a gasifier stove in Kenya. Using cleaner, energy efficient gasifier cook stoves instead of traditional wood burning fires has a positive impact on agriculture and environment. Photo credit: Mary Njenga
26 July 2018

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BONN, Germany (Landscape News) – Using cleaner, energy efficient gasifier cook stoves instead of traditional wood burning fires has a positive impact on agriculture and the environment, ultimately reducing the amount of fuel burned by more than 40 percent, according to scientists.

Currently, almost 4.5 million people die each year from health problems caused by inhaling indoor smoke generated by burning solid fuel. Worldwide, 38 percent of the population – 2.7 billion people – cook with wood collected unsustainably from forest and farm landscapes.

In sub-Saharan Africa, the backbreaking process of gathering firewood by hand – often by women and girls – and carrying it home provides the main source of fuel for cooking and heating.

Although liquid fuels, solar energy and hydropower could offer possible alternatives, high costs, infrastructure shortcomings and local habits make sustainable use of wood fuel, including firewood and charcoal, a more viable option in the region.

As a result, researchers at the World Agroforestry Centre (ICRAF) and the Wangari Maathai Institute (WMI) in Nairobi, Royal Institute of Technology, Lund University, Swedish University of Agricultural Sciences, International Institute for Tropical Agriculture, Center for International Forestry Research are trying to find healthier, more efficient energy conversion technologies that emit less pollution and simultaneously produce biochar (biomass charcoal) for soil amendment to improve plant growth and health.

“Cook stoves are critical — we need to develop innovations to meet cooking and energy needs that work within locally available infrastructure and which offer environmental and socioeconomic benefits,” said Mary Njenga, bioenergy research scientist at ICRAF and visiting lecturer at WMI.

“Not only is it strenuous work to gather wood, it detracts women from other pursuits such as agriculture or operating small businesses to generate income,” said Njenga, who will deliver a Landscape Talk speech at the upcoming Prospects and Opportunities for Restoration in Africa Global Landscapes Forum (GLF) at UN Environment headquarters in Nairobi. “Women spend about one working day per week in collecting firewood from forests. This implies that women are essentially living on a 20 percent pay cut as their productive days in a week are normally five as they spend Saturdays attending to domestic chores.”

Gasifier stoves help fulfill those aims. The stoves produce charcoal as a byproduct of wood burning, allowing a second meal to be cooked in a separate charcoal-burning stove and increasing efficiency in comparison to traditional three-stone stoves traditionally used in Kenya.

For their study, the team evaluated energy use efficiency, indoor air concentrations of carbon monoxide and fine particulate matter in rural Kenya to compare the new stove with other stoves.

Gasifiers transform firewood or crop residues to energy in four stages, including drying; pyrolysis (carbonization); gasification and gas combustion. After comparison with other options, the stoves were found to be most efficient at producing charcoal during the cooking process. The gasifier is also cleaner and burns more efficiently, saving about 40 percent of the amount of fuel used in the three stone open fire and 27 percent if the charcoal is used for other purposes, such as in soil management. It reduces the concentration of carbon monoxide and fine particulate matter by 45 percent and 90 percent compared to the three stone open fire, researchers discovered.

Charcoal produced in the gasifier stove was found to have good fuel properties, tested by cooking traditional meals comprising of ugali, a maize flour meal, and kale vegetables using the Kenya Ceramic Jiko (KCJ) charcoal stove. The performance of the charcoal produced in the gasifier was compared to conventional wood charcoal.

The study began as a pilot in Embu, a town about 120 kilometers northeast of Nairobi, where 20 households were given a galvanized steel gasifier made by artisans in Nairobi.

After receiving training, 20 households were issued with a gasifier stove and 35 percent used it daily. They said it saved fuel, produced less smoke and cooked food more quickly compared to the three stone stove. Users also liked its ability to produce charcoal for further cooking or for use as biochar, which improves soil by enhancing moisture and nutrient retention, improving structure, promoting micro fauna and sequestering carbon.

The farmers reported shortcomings with the galvanized steel gasifier because they found it was unstable and its wall got too hot, posing a high risk of burns.

In the second phase of the of the project, the team used the superior Gastov gasifier being produced by the Kenya Industrial Research and Development Institute (KIRDI). The Gastov is more stable and is fitted with an insulated wall. The stove was issued to 150 farmers in three areas. After two to three months of use, 96 percent of the households were still using it.

After a season of biochar application, the farmers realized an increase in yields. Some farmers produced more biochar than they needed on their pilot plots, sharing with neighbors. If biochar production continues, it could be an additional source of income for small-scale farmers, Njenga said, adding that scientists continue to study biochar quality and its beneficial attributes.

Small-scale farmer based biochar production is a win-win-win-win innovation for improving livelihoods and landscapes, Njenga said.

Crop residues such as maize cobs and coconut husks are also used as cooking fuel for gasifiers, reducing environmental pressure on treed areas. Residue burning means farmers also use fewer prunings from multipurpose trees on farms, reducing cooking energy poverty.

Additionally, farmers harvest the charcoal when the flame is turned off, and by that time quick cooking foods are ready. However, for food that takes longer to cook such as maize and beans, they still prefer to use the three stone fire instead of re-lighting the gasifier stove. As a result, the three stone open fire has not been abandoned and efforts to improve on its performance should also be pursued for optimal health benefits, Njenga said.

As a result of ongoing discussions of research findings with KIRDI, the Gastov has undergone improvements. It is now a dual stove that uses less fuel in addition to producing charcoal, eliminating the need to use a second charcoal stove. Despite 70 years of efforts to improve cookstoves, aims have not been realized and adoption rates are low, in part due to focus on distribution alone and limited research.

For scientists, research results illustrate the need to clearly understand the needs and preferences of users to ensure improved stove technology fits into their cooking culture. For example, the Gastov requires users to cut wood into small pieces of about 1 foot which is a challenge.

The research team includes design and environmental science students and a gender researcher from the Office of International Programs, College of Agricultural Sciences at Penn State University. This process has brought together a trans-disciplinary team that embraces co-learning and co-designing.

This on-going study began in 2013 and is supported by the Swedish Research Council and the Swedish International Development Cooperation Agency.

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