Carbonization is a mild-pyrolysis process in which organic matter (e.g. agricultural residues, wood) is converted into a carbon-rich solid. This is the process that, over geological timescales, produces fossil fuels like coal, natural gas and petroleum oil. It typically occurs at temperatures of 300-400°C and, unlike combustion, does not require oxygen.
People in many communities use charcoal made from wood as a cooking fuel. D-Lab has developed a simple, low-cost process for using waste materials, like corn cobs and coconut shells, to make a material that can be used as a wood charcoal substitute. An important part of this process is carbonizing waste in a container, called a kiln, which limits the amount of air entering (and the temperature) inside.
A number of simple and complex technologies exist for carbonizing waste. The Fuel & Stoves Group is evaluating upon existing low-cost kiln technologies to determine suitable designs for achieving high char yield and low pollutant emissions.
Applying a large compression force to a granular material can cause the particles to bind together, usually through mechanical adhesion (e.g. interlocking fibers). The addition of a binder (e.g. starch) increases the strength of bonds between particles in the material. People use compressed blocks, bricks, and briquettes for a variety of applications including construction and fuel.
Since biomass like corn stalks and banana peels come in all shapes and sizes, grinding char made from these to a powder and then packing into briquettes makes sense to keep uniformity and consistency. Charcoal briquettes can be made using several techniques including small manual presses, to motorized screw presses. Community groups and small fuels businesses worldwide use these machines to manufacture their products.
The Fuel & Stoves Group is working with briquette producers and local fabricators to improve processes along the production chain, from carbonization to briquette drying. We are developing a simple case-hardening method to improve the wear resistance of components in locally fabricated, medium-scale screw presses (thesis). We are also evaluating methods for decreasing the time to dry freshly pressed briquettes.
Usage, Efficiency, Emissions & Air Quality
Background: Significant progress has been made recently to reduce the emissions and increase the efficiency of fuels and stoves. Yet balancing the benefits of reduced household air pollution and fuel consumption while considering user's preferences and financial limitations is a challenge. Recent studies show that sustained and exclusive adoption of improved cookstoves is low. Meanwhile, the number of premature deaths each year due to respiratory illness and disease attributed to household air pollution is increasing.
The D-Lab Fuel & Stoves Group leverages valuable partnerships with field practitioners and local enterprises who are supplying improved cooking products and providing employment opportunities to their communities. The survival and success of these enterprises ultimately depend on the uptake and adoption of their products.
Since many of our partners cannot access or afford to support R&D, the D-Lab Fuel & Stoves Group applies our engineering and testing capabilities to improve their products. We are applying existing and developing new methods for understanding the impacts of these products on indoor air quality, fuel savings, and user adoption. Our research uses mixed qualitative and quantitative measurements in both lab and field settings.
Standards exist to unify practitioners around a method and set of metrics that is agreed upon and accepted by an authority. Without standards, we wouldn't have common bolt and nut sizes, railroads, the kilogram or mobile networks. They act as guidelines for manufacturers to follow and ensure quality and safe products and services for all of us.
Practical: Many common fuel types and cookstove designs exist (e.g. the jiko in East Africa). However, a lack of guidelines for manufacturing, testing, and certification allow for poor quality and counterfeit products to survive in the market. Producers of quality products would benefit from standards for quality and performance to ensure that customers receive the full benefits of the product.
We believe that economically poor people don't deserve poor quality products. The D-Lab Fuel & Stoves Group is working with local fuel producers to design on-site testing procedures to ensure the quality and consistency of their products (quality testing protocol and data entry sheet). In addition, D-Lab biomass fuel research scientist Dan Sweeney is participating on the ISO technical committee to produce a global standard for clean cooking solutions.