Although many people are not aware of the scope of the problem, tobacco production and curing is devastating the native forests of Uganda, Kenya, Tanzania, Zambia, and Malawi. It is estimated that over 110,000ha of forest is lost each year.
Since 2005, we have been developing an improved tobacco curing system for small holder farmers in southern Africa. In 2007 field research conducted by GTZ/ProBEC showed that the rocket barn reduced fuel consumption by 50% and increased farmer income by approximately USD 1300/p.a. This year in Malawi, Hestian Innovation will partner with Alliance One and Limbe Leaf to build approximately 1500 barns in the next 6 months.
Working with BAT and GTZ/EAP Uganda we are also prototyping a new and unique barn for Uganda. We are interested in placing interns in Malawi to help support the dissemination effort. If you are interested, let us know by clicking here.
If you are interested in helping in developing collaborative research projects with universities to study and improve the design of the rocket barn, let us know by clicking here.
Contact us for user guides and step-by-step plans for constructing rocket barns, available on a case-by-case basis.
The rocket barn is protected by a US provisional patent as well as an international patent application.
(New International Patent Application No. PCT/US2010/53395 filed October 20, 2010 (Based on U.S. Provisional Application Nos. 61/387,777 filed September 29, 2009 and 61/402,379 filed August 26, 2010) NATURAL DRAFT CURING SYSTEM ).
If you are interested in licensing this technology please contact Peter [at] rocketstove [dot] org
Trials at Lisandwa Estates,
December 2009 - March 2010
Prepared by: Peter Scott
Prepared for: Alliance One and Phillip Morris international
Existing wood powered conventional tobacco curing systems at Lisandwa Estates in Malawi - as in many parts of Africa - are extremely inefficient. Alliance One estimates that, on average, 18 m3 of pine (or approximately 9000 KG) are required to produce 1000 KG of cured tobacco1 at Lisandwa.
During the 2009-2010 season, two new Commercial Rocket Barns were developed to reduce fuel consumption and to improve leaf quality. The 'RB 5W' 1000 stick barn utilizes a wood furnace with natural draft convection, and the 'RB 5C' 1000 stick barn utilizes a hand-fed coal furnace/forced air system.
Near the end of the curing season, our tests showed that the conventional barn (CB 4) required 9.7 m3 of pine to produce 783 kg of cured tobacco in one test and 11.8 m3 of pine to produce 824 kg tobacco in the second test, as compared to the RB 5w, which required 3.3 m3 of wood to produce 824 kg and 801 kg respectively. This translates into an estimated average of 13.35 m3 of pine/ton of cured tobacco (or an SFC of 6.8 KG of wood:1 KG of cured tobacco) 2 for a conventional barn and an estimated average of 4 .05 m of pine/ton of cured tobacco (or an SFC of 2 .03 KG of wood:1 KG of cured tobacco3) for the RB 5W. See the table below for a comparison between the RB 5W and the conventional barn.
During the last two weeks of the curing season, the RB 5W system
was reconfigured to utilize coal. A new hand-fired coal furnace was
constructed and connected to a 1/3 hp fan unit. As the table below shows,
the new RB 5C required 1120 KG of coal to produce 821 KG of cured
translates to an estimated SFC of 1.4
KG coal:1 KG tobacco.
Anecdotal reports suggest that conventional
hand-fired coal/forced air curing systems commonly require 2-3 times
the quantity of coal that was used in the RB 5C. Unfortunately, we were
not able to conduct tests on conventional coal barns due to the absence
of such barns at Lisandwa estates.
- wood or coal -is the most cost-effective in Malawi?
Ascertaining the type of fuel that
is the most cost-effective depends upon a number of factors (e.g. the
price difference between wood and coal, cost of transport, access to
electricity, operator skill level etc.). These obviously will vary for
In Malawi, for example, one ton of
coal costs approximately US$150 landed. This would translate into a
cost of approximately $165-$210 per ton of tobacco cured. This
does not include the cost of electricity, capital costs such as fans,
and associated maintenance3.
The price of one cubic meter of wood
is approximately US$30 landed. This translates into a cost of $120
per ton of tobacco cured as compared to $165-$210 per
ton for the RB 5C or $400 per ton for the conventional barn.
Because the RB 5W utilizes a natural draft, it does not require a fan
or other costs associated with a forced air system. Also, leaks in the
flue pipes are less critical, since the volatile gases in the wood develop
a more powerful draw through the flue pipe system.
The RB 5C, on the other hand, must
be constructed so as to completely eliminate leaks from the flue pipes
. Coal, unlike wood, does not contain a large quantity of volatile gases
and therefore does not naturally generate its own convective flow. Without
air being forced constantly through the entire flue pipe system, heat
transfer and convective flow through the barn are greatly
diminished. If the flue pipe system is not constructed and maintained
properly, barn performance will be greatly reduced.
The skill level of the furnace attendant
should also be considered when deciding whether to disseminate the coal
or wood powered barns. For example, if the attendant does not split
the wood or if the fire is not carefully tended, then barn performance
will be diminished and costs will go up.
Obviously, the skill of the furnace
attendant is a critical factor for both the wood- and the coal-powered
rocket barn systems. However, it appears to have a less significant
impact on the performance of the wood-powered barn. More observation
of coal and wood furnace operators is recommended to assess the validity
of this assumption.
Furthermore, the RB 5W is the more
attractive option for developing a carbon offset project, especially
if the wood is sustainably harvested.
Conclusion: although more research would provide a more conclusive picture (as only two tests of the coal powered barn were conducted) it appears that the wood powered rocket barn (RB 5W) is the most cost-effective option for Malawi.