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Gaining Theoretical and Practical Experience with TLUDs at Stove Camp

By Thayer Tomlinson

I had the pleasure of joining about 25 other participants to learn how to design, build, and operate small gasifiers at the CHAB camp (Combined Heat and Biochar) August 7 – 12th. Run by the Biomass Energy Foundation (BEF), the camp was located at the New England Small Farm Institute (NESFI) in Belchertown MA (United States). With large indoor and outdoor facilities and tools, it was a perfect place to test and build gasifiers. 

The camp’s three instructors Paul Anderson (Dr. TLUD), Hugh McLaughlin, and Tom Reed provided group lectures on gasification, thermodynamics, design, application, feedstock issues, and chemistry as well as hands on instruction. We examined existing rocket and TLUD (top lit updraft) stove models, learned about larger “ovens”—55 gallon TLUDs—and had the opportunity to put theories into practice by building our own gasifiers and testing them. Through lighting and operating the units, it became obvious which designs worked and which needed further revision. Participants also put our stoves to work by cooking meals and learned how the stoves behave “in the field” when rain and wind are very much present. We also had the ability to use multiple feedstocks such as switchgrass, woodchips, walnut shells, jatropha seeds, and pellets—with different moisture percentages. 

Firing up the stoves highlighted some of the common stove testing procedures such as the water boiling test (which really clarified how long 40 minutes can be if you are waiting for water to boil). Ideally, a good stove can boil a 5 liter pot of water in about 20 minutes. If TLUDs are to completely or even partially replace a three stone fire in a developing country application, they need to be reliable, save fuel, produce fewer emissions, and most importantly, be user friendly. I learned this quickly when one of my initial designs tipped over when I placed a pot of water on it.

The camp participants were mainly from the US and Canada but we had some from as far away as Kenya. Not everyone at camp was interested primarily in cooking applications. By day three, we split into group project work—some focusing on cook stove development, but others designed, built and tested larger 55 gallon TLUDs made to specifically produce biochar and sequester carbon. Additional projects focused on multiple large stoves for maple syrup/institutional cooking applications, dual TLUD/charcoal stoves, feedstock drying units, and models for educational demonstrations.

Throughout the five day camp, we had numerous guest speakers who provided perspectives on business cases for cookstoves in developing countries, highlighted international programs which currently use ovens and cookstoves, reviewed some TLUD education programs, and provided an update of activities from the recent UKBRC (UK Biochar Research Program) conference.

BEF will be hosting a Spanish language CHAB camp in Honduras the end of September at the Zamorano Institute; for more information, please contact Paul Anderson. Additionally, BEF has plans to expand its training offerings for further educational efforts around the globe.