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Supported by the National Science Foundation's program for Basic Research to Enable Agricultural Development (BREAD)

landscape_50y_conversion
Above: Complex agroecological landscape on a site with 50 years of agriculture: maize, tea, fallow, and agroforestry species (photo: D. Guerena).
Updates on Our Research

Updated August 2013

Clean-burning pyrolysis cookstoves: design and modeling

CookstoveSchematic

Above: Schematic of the pyrolytic cookstove now being produced as a pilot for further field testing in Kenya

Model_temperatureField

Above: Model results that were used in the improvement of cookstove performance through the incorporation of a truncated cone (right side image, angled wall in section view at top below the stove exit) that helps to improve drafting of stove and reduce smoke emissions. Colors show temperature field within the stove. Bottom of pot is at top.

Guided by existing stove designs and our modeling work to date, We have developed a pilot design for field testing in Kenya which incorporates an annular pyrolysis chamber and an outer drafting/safety shroud. The pyrolysis chamber is heated by, and also feeds an inner combustion chamber with pyrolysis gases. Temperature, velocity, and gas compositions can be modeled by the FLUENT modeling software, allowing the team to forecast the efficiency of heat delivery to the pot at the stove outlet as well as emissions characteristics by looking for uncombusted pyrolysis gases and final combustion products.

surface of response for CO:power metric of stove

Above: Surface of response for a stove evaluation metric, CO produced per KJ power output, to the stove-pot gap distance and the inner top wall length (truncated cone in final schematic above). Lower values denote better stove performance.

High energy output and low emissions are two important criteria for the stove, and we are using the ratio of carbon monoxide (CO) per unit power output of the stove as an important initial metric when evaluating model outputs as guidance for building test stoves. At left we show model outputs for how this ratio depends on the stove-pot gap and the inner barrier to increase residence time of fuel gases developed above as a truncated cone. An ideal stove would have low CO emissions with a high power output, and an excellent conversion efficiency of the pyrolyzed fraction of biomass fuel into energy.

Talk by B. Fisher at JKUAT

Photo: Professor Betta Fisher discusses stove modeling and design with engineers and students at Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya.

During a recent visit to Kenya, Professor Betta Fisher gave a presention and discussed stove modeling and design with engineers at the Jomo Kenyatta University of Agriculture and Technology (JKUAT).

Emissions testing and health impacts of pyrolysis cookstoves

Stove Mass Production, Kenya

PyrolyticStove_finalTouches

Photos: Pilot stove mass production (above) and finishing touches (below) during manufacture near Kisumu, Kenya.

Training on Stoves prior to testing

Photo: Training on stoves near Kisumu, Kenya with Willis Okatch and Dori Torres (Left) and Prof. Betta Fisher (Right) prior to distribution and gathering on usage, fuel efficiency, and emissions testing.

InputOnStoves_Kenya

Photo: Women give initial reactions to stove performance in a kitchen setting during training.

 

Using a completed pilot stove from the modeling and design team, Dori Torres, Rufus Edwards, and Betta Fisher have initiated a study on greenhouse gas emissions, fuel use and biochar production, and kitchen air pollution impacts in rural households in western Kenya. The study will monitor the improvements in emissions and indoor air pollution in households with the project's pyrolytic cookstove compared to traditional stoves and three-stone fires.  Total cooking time, and amount and type of fuel used will also be monitored to assess the overall impact of stove adoption on human health, biomass stocks, and potential benefits from biochar production.

Biochar as a microbial inoculant carrier

Rhizobia bacteria on hardwood biochar

above: Rhizobia nitrogen-fixing symbiotic bacteria (rod-shaped, about 3 micron length, center) occupying the surface of a hardwood biochar, visualized with a standard-prep scanning electron microscope. (photo: H. Jin)

rhizobia on grapevine biochar AirSEM

above: Rhizobia bacteria (circled) on grapevine biochar, visualized with an innovative zero-preparation scanning electron microscope in ambient air. (photo: S. Vanek)

Petri plate showing growth of rhizobial colonies

above: petri plate test for evaluating the growth of rhizobia in a biochar or peat medium. Each dot or bacterial colony originated from one bacterium or colony-forming unit within the microbial carrier. (photo: S. Vanek)

Steven Vanek and Janice Thies have concluded a number of trials comparing the usefulness of a wide variety of feedstocks for biochar to support microbes as inoculants, and are currently analyzing data to conclude what physical and chemical parameters lead to good carrier performance. Several materials show good promise as inoculant carriers, able to support microbes for months at tropical storage temperatures, at levels that satisfy international inoculant carrier standards (>108 bacteria per gram inoculant material @ six months).

David Guereña and Steven Vanek are also conducting new experiments that assess the potential for biochar to support rhizobia once in the soil under drying stress, which help to understand the interaction of biochar with microbes more generally in field soil conditions with wetting and drying cycles.

 

Biomass assessment to examine fuel use and fuel sources
Wood Gathering

Photo: fuelwood gathering near Kisumu, Kenya. (photo: D. Torres)

While also assisting the stove development team with design work on the stoves, Dori Torres has completed a broad inventory of biomass sources used in local bioenergy systems in coordination with the World Agroforestry Center (ICRAF), which will inform modeling efforts by the project team on landscape-level impacts of pyrolysis cookstoves and other bioenergy activities linked to biochar. She used a combination of quickbird satellite imagery and ground-truthing assessments of large landscape blocks of size 10x10 km, and is conducting the analysis of this large dataset. We look forward to her results.

Biochar and inoculant impacts in nutrient cycling in soils

Maize_biochar

Above: Johannes Lehmann shows a biochar plus fertilizer plot at left compared to a plot with a green manure plus fertilizer. (photo: J. Berazneva)

The Lehmann lab is researching the impacts of biochar inoculants on crop growth and how biochar applied to the soil can improve nutrient cycling in agroecosystems. Dori Torres is examining the molecular forms and fates of nitrogen (N) in biochar using x-ray spectroscopic analyses and a greenhouse study, to test the availability of biochar N ("black nitrogen") on N cycling. David Guerena has been researching how biochar applied to soil improves the efficiency of nitrogen fertilizer use by farmers, a study that will soon be published. He is also readying results for publication that were gathered during a greenhouse study that investigated the impact of different components within biochar (retained ash minerals, volatile compounds left from pyrolysis, carbon backbone structure) on nodulation and growth of beans. David is also conducting a second trial on the way that different biochars protect bacteria under drought stress in soils.

mycorrhizae on biochar

Above: Mycorrhizal hyphae (Glomus clarum) growing on biochar in a sample taken from a greenhouse experiment. (photo: S. Vanek)

Steven Vanek has analyzed data from a greenhouse experiment testing biochar and mycorrhizal impacts on phosphorus availability to beans. He has submitted a paper on the results to Plant and Soil, an international plant science journal.

Meanwhile, at ICRAF, Henry Neufeldt and Bernard Fungo have conducted a study on the effects of biochar in soils on greenhouse gas emissions. The field sites from the other studies and the focus on nitrogen and microbes will provide a great degree of complementarity between the ICRAF and Cornell research work.