Data from: Emissions and char quality of flame-curtain "Kon Tiki" kilns for farmer-scale charcoal/biochar production

Pyrolysis of organic waste or woody materials yields charcoal, a stable
carbonaceous product that can be used for cooking or mixed into soil, in
the latter case often termed "biochar". Traditional kiln
technologies often used for charcoal production are slow and without
treatment of the pyrolysis gases, . This resultings in emissions of gases
(mainly methane and carbon monoxide) and aerosols that are both toxic and
contributes to greenhouse gas emissions, the most important being methane,
carbon monoxide and aerosols. In rRetort kilns where pyrolysis gases are
led back to a combustion chamber. This are faster and can reduce emissions
substantially, but isare costly and consumes a considerable amount of
valuable ignition material such as wood during start-up. To overcome these
problems, a novel type of technology, the Kon-Tiki flame curtain
pyrolysisrocess, is proposed. This technology combines the simplicity of
the traditional kiln with the combustion of pyrolysis gases in the flame
curtain (similar toachieved in the retort kilns)., also avoiding use of
external fuel for start-up. By adding feedstock layer by layer in an open
cone-shaped kiln, the pyrolysis gases formed underneath the flame curtain
are combusted, at the same time creating enough heat to avoid use of
external fuel for start-up. The rResults from this aA field study in Nepal
using various feedstocksmixtures of the ubiquitous invasive shrub
Eupatorium, rice husk and wood as feedstocks showed char yields of 22 ± 5
% on a dry weight basis and 40 ± 11 % on a C basis. Total pyrolysis time
was one to four hours per m3 of produced biochar. Biochars with high C
contents (76 ± 9%; n=57), average surface areas (11 to 215 m2 g-1), low
EPA16 - PAHs (2.3 to 6.6 mg kg-1) and high CECs (43 to 217
cmolc/kg)(average for all feedstocks, mainly woody shrubs) were obtained,
in. Overall, the analytical data of all biocharsthe produced with this new
technologybiochars complianceed with the European Biochar Certificate
(EBC). The mMean emission factors for the flame curtain kilns found in
this study were (in g kg-1 biochar for all feedstocks); carbon dioxide
(CO2)= 4300 ± 1700, carbon monoxide (CO)= 54 ± 35, non-methane volatile
organic compounds (NMVOC)= 6 ± 3, methane (CH4)= 30 ± 60, aerosols (total
suspended particles, TSP, derived from (PM10) = 11 ± 15, total products of
incomplete combustion (PIC)= 100 ± 83 and nitric oxides (NOx)= 0.4 ± 0.3.
The Kon Tikiflame curtain kilns emitted statistically significantly
(p<0.05) lower amounts of CO, PIC and NOx than retort and
traditional kilns, and higher amounts of CO2. With benefits such as high
quality biochar, low emission, no need for start-up fuel, fast pyrolysis
time and, importantly, easy and cheap construction and operation the flame
curtain technology represent thus a promising possibility for sustainable
rural biochar production.