Keeping healthy and saving trees
Gasifiers could provide an answer to many of the issues associated with traditional cook stoves: the cost of fuel, the burden of firewood collection, health impacts and the destruction of trees.
“Keeping healthy and saving trees” is the subject of an article in the May-June 2015 edition of Miti magazine published by Better Globe Forestry.
In the article, led by Mary Njenga from the Word Agroforestry Centre, the authors call for a change in mindset and awareness-raising on the benefits of improved cooking technologies for improved livelihoods, environment and ecosystems.
Studies in Kenya have shown that cooking with a gasifier uses 40 per cent less fuel than a 3-stone cook stove and 27 per cent less fuel than an improved cook stove.
The article explains how a gasifier burns biomass under controlled oxygen where the volatiles and tars are burnt and charcoal and wood gas are made. The resulting gas mixture and charcoal can be used as energy. This technology is not new; the gasification of wood and coal has been known and used since the 1800s, in particular for coal-based gaslight in London and Paris during the 1850s.
To use a gasifier for cooking involves lighting it outside using tree leaves or papers till the fuel catches fire well, then taking it inside the house to cook. Cooking is done using the gases produced by the gasifier. Gasification and combustion of gaseous fuel is cleaner when compared to the open air combustion of firewood. A gasifier significantly reduces indoor air pollution caused by concentration of carbon monoxide and fine particulate matter. In addition, the gasifier transforms firewood into charcoal which can be used for cooking or other purposes such as soil amendment (biochar).
More than 4.3 million deaths a year are associated with smoke from kitchens. “Using inefficient cooking technologies such as poor performing cook stoves, poor quality biomass such as wet wood, wood from tree species with low energy and/or with toxins, and cooking in kitchens with inadequate ventilation all escalate the problem,” says the article.
Gasifiers can also make use of crop residues which would save trees and forests as well as mean reduced expenditure by households on cooking energy.
Collecting firewood is a time-consuming and arduous task, usually done by women and children. It diverts their attention away from other productive activities and education, and carrying heavy loads can have serious health impacts.
Importantly a gasifier has the potential to improve nutrition. Cooking food is important in breaking down carbohydrates and making food easier to digest so that humans can derive optimal energy and other nutrients. Cooking also makes food safer and tastier. But for poor people, accessing the energy needed for cooking can be a challenge. Many use unsafe sources of cooking fuel such as plastic when they can’t afford charcoal or find firewood. In some cases, traditional nutritious food that takes too long to cook is abandoned.
The author do note that there are some challenges associated with using a gasifier; it takes considerable time to light, requires wood to be chopped into smaller pieces and can become very hot. It does not provide warmth or allow for roasting of food. Also, a gasifier is more expensive than an improved or 3-stone cook stove.
With energy demand on the rise globally and around 2.5 million people worldwide still relying on biomass energy for cooking and heating, the long-term health and environmental benefits of gasifiers must surely outweigh those of more traditional cook stoves.
The article is authored by researchers from the World Agroforestry Centre; Wangari Maathai Institute for Peace and Environmental Studies at the University of Nairobi, Kenya; International Institute of Tropical Agriculture (IITA); and the Swedish University of Agricultural Sciences (SLU). It is based on on-going research to investigate the feasibility of small-scale bio char production and use to improve the livelihoods of smallholder farms in Kenya.