Comparative study of carbonization techniques on the quantity of charcoal andquality as a biochar in the city province of Kinshasa (DRC)
Amela Lokima Bosekwa Peter
Ehime University; AAP Master I
Graduate School of Agriculture
peteramela@yahoo.fr

Introduction
 The soils of Kinshasa and its surroundings for the most part, are highly degraded andvery acidic. This translates into low agricultural yield.
 Peasants practice itinerant agriculture on burns and are more interested in making
charcoal to improve their income. It is a threat to the forest and climate change
mitigation.
 Biochar offers the possibility of improving the physical properties of sandy and acidic
soils. However, the production of charcoal that can be used to make biochar, is doneby traditional carbonization and gives low yields with a high environmental cost.
 It is in this context that we conducted a study to compare the production and qualityof biochar of three carbonization techniques including the Traditional Technique (T),the Traditional improved Technique (TA) and the Traditional Improved Technique with
Metal Vents (TAM).

pH and carbon content of T, TA and TAM biocharsoil pH and texture
TechniquespH%COT

6.80

43.45aTA

6.63

78.43b

Objective

TAM

6.70

66.75ab Evaluate the amount of production of each technique in order to determine thenecessary planting forest area to be cut to amend 1 ha of sandy soil with 30 tons ofbiochar.
 Evaluate the quality of biochar from each carbonization technique in terms of pH,carbon content and water retention capacity

Tab. 2. pH et %CO of biochars

 pH (soil) = 5.59, texture = sandy (sand = 82.27%
silt=3.39% clay=14.34%)
 pH of biochars of all techniques is acidic. Lehmann
et al., 2009 showed that biochars can be produced atalmost any pH (between 4 and 12).
 The carbon comparison test gave the following
descending order: TAM > TA > T.

Water retention capacity
Evolution of water content

Method and material
A. Charcoal production
 The charred species is Acacia auriculiformis
cut from a 7-year plantation with an area of Processing of charcoal into biochar
0.5 ha.
 The difference between T, TA and TAM is Steps: preparation of wood, construction ofin the grinding mwheel ventilation
12 stere wheels, weighing of 5 steres withsystemdynamometer to find the average weight of Calculation
ofcharcoal
yield
bya stere, carbonization, unloading, sacking,technique:charcoal weighing

Fig.6. Evolution of the volumetric water content fordose 15

Charcoal (kg)/grinding wheel weight(kg) x 100

TAT

T

TAM

TAM

TA

T : technique
Traditionnelle

TAOn the one hand, biochar increases
the water retention power of the soil
and on the other hand, like any otherorganic matter, biochar prevents waterfrom evaporating quickly

TA : technique
Traditionnelle
Améliorée

TAM : technique
Traditionnelle
améliorée avecévents Métalliques(TAM).
Fig. 1. Arrangement of the wheels incomplete blocks randomized
TAM For the dose of 30T/ha the curvesof the carbonization techniques havean almost confused appearance. But
they are higher than the curve of
the control sample. Towards the endof the observation the suction force
had decreased, the temperature in
the dry season at night dropped andthis slowed down the trend ofevaporation

THowever, the performance of thecontrol sample would be justified by
the relatively high clay content (14%)

Fig.2. Construction of a TAM Grinding Wheel

B. Soil sampling, Laboratory analyses
 Sampling of soil to be mixed with biochar: soil depth 0-30 cm, air drying, composite
formation, measurement of soil pH (distilled water, pH meter) and analysis of soil
texture according to the method of the Laboratory of the ORSTOM Center of Noumea
in New Caledonia using hydrogen peroxide (H2O2) and hydrochloric acid (HCl).
 We mixed the soil and biochar in cups following the treatments. We then weighedthem to have the dry weights. We moistened them (300 ml of water) until saturationand waited for the end of the infiltration and weighed the moistened weights. The
follow-up was done by weighing every day.
 To determine the amount of biochar of the doses 15 T/ha and 30 T/ha corresponding
to 816g and 813g of soil, we exploited the relationship between the weight of the soilon 1ha at the depth of 30 cm (depth exploitable by the roots of food crops) with thedensity of sand (d=1.5).
 Evaluated parameters: Water content (Θ)= (Wet weight (Ww) – Dry weight(Dw)) /Dw *100*d with d=sandy soil density = 1.5; Moisture at field capacity(Mf)=(Ww-Dw)/Dw *100; Humidity at the Wilting Point (Hf)=Hc*1/3 for sandy
soil with more than 10% clay,According to Perigaud (1963) cited by Kayembe (2016)

Fig. 7. Evolution of the volumetric water content
for dose 30

Observation of Moisture in the field, moisture at the point of wilting, wateravailability time for doses of 15T/ha and 30T/ha
The water availability time for the plant is the number of days that separate
moisture at field capacity and moisture at the wilting point.
This is the time it takes for the water in the soil to no longer be available to plants.
Techniques

Hc (%)

Hf (%)

Temps (j)

D15

D30

D15

D30

D15D30

t

21.9

21.9

7.5

7.5

15

15

T

24.0

24.5

8.0

8.2

16

17

TA

24.0

24.5

8.0

8.2

1618

TAM

22.2

24.1

7.5

8.4

1618

Tab.3. Summary of results on field moisture, wilting point moisture, water
availability time for the plantResults

In the second part of the work the observation is not very different between
the three carbonization techniques on almost all parameters observed. The
difference is observed between biochar treatments of dose 30T/ha and thecontrol.
The different aeration systems of the carbonization techniques have increased
the yields and not the quality of the biochar because the majority of the factors
influencing the quality have acted fairly in all the techniques, including the raw
material used which is Acacia auriculiformis harvested on the same plantation of
7 years and the preparation of the wood before carbonization was done under
the same conditions for all techniquesAlso, the high clay content (14%) of our soil did not allow to observe thedifference between soil amended with biochar and the control

Area required by technique to produce 30T of biochar

Conclusion

Fig. 3. arrangement of 18 permeable cups
Fig. 4. Dose 15 and Dose 30 Treatments and(dimension = 700 ml) associated with 16 jars tosample control
collect the percoding.

Technique Wood(kg)

area(m2)

Charcoal+ waste area/30T(kg)(ha)

area/30T(%)

100

T

6004.4 540.5 1304.467 1.243
78.8

TA

6004.4 540.5 1655.0

0.979
100,3

TAM

6004.4 540.5 1299.8

1.247

Tab.1. Area to be deforested to produce 30 tons ofbiochare to be amended 1 ha of cropWith the TA we can reduce the area of
deforestation due to carbonization by
21.2% compared to the traditional
technique (T)Ibi village, where 100 ha of Acacia is
made available in the carbonization
market per year, the use of TA toproduce 30 tons of charcoal biochar
processing, represents a reduction of
21.2 ha on annual deforestation.

Applying biochar is a sustainable technique. There are agricultural andenvironmental positives effects. In Kinshasa, producing biochar by the TA
technique can improve the processing. However, other studies using other tree
species, and monitoring parameters to see the long-term effect of biochars usedon the evaporation process, the retention of mineral elements, the biologicalactivity of soils, may be complementary to this study.