**Correction 1:**

**Answer 1:**

The main characteristics of climate change in Sahelian humid zones include an increase in the frequency of extreme climatic events (heavy rainfall, floods), periods of drought between wet seasons, as well as increased variability of annual precipitation.

**Answer 2:**

In the Sahelian humid zone, climate change is mainly manifested by irregular rainfall and increased temperatures, while in the semi-arid zone, the effects are more marked by prolonged drought, increased desertification, and even higher temperatures, leading to a significant reduction in water resources.

**Answer 3:**

Climate variability in the semi-arid zones of the Sahel negatively affects agricultural production by making growing seasons more unpredictable, decreasing water availability, and increasing heat stress on crops, which reduces yields.

**Exercise 2: Perception of Climate Change by Farmers in the Sahelian Zone**

**Question 1:** How do farmers in the Sahelian wetlands perceive climate change?

**Question 2:** Identify the differences in the perception of climate change between farmers in the wetlands and those in the semi-arid zones of the Sahel.

**Question 3:** What are the main signs of climate change observed by farmers in the semi-arid zones of the Sahel?

**Correction 2:**

**Answer 1:**

Farmers in the Sahelian wetlands perceive climate change mainly through the irregularity of the rainy seasons, frequent floods, and an increase in dry periods between rainy seasons. They also observe a decrease in soil fertility due to erosion.

**Answer 2:**

Farmers in humid areas perceive climate change through irregular rainfall and flooding, while those in semi-arid areas are more concerned about longer droughts, reduced water resources, and rising temperatures, which directly affect the survival of their crops and livestock.

**Answer 3:**

The main signs of climate change observed by farmers in semi-arid areas of the Sahel include increased temperatures, reduced rainfall, a shorter and more irregular rainy season, and an increase in the frequency and intensity of droughts.
**Exercise 3: Adaptation Strategies of Farmer Organizations**

**Question 1:** What are the main adaptation strategies developed by farmer organizations in Sahelian humid zones in the face of rising temperatures?

**Question 2:** Compare the adaptation strategies of farmer organizations in Sahelian humid and semi-arid zones in the face of the effects of climate change.

**Question 3:** Discuss the limits of current adaptation strategies of farmer organizations in the face of the long-term effects of climate change.

**Correction 3:**

**Answer 1:**

In Sahelian humid zones, farmer organizations adopt strategies such as improving irrigation techniques, diversifying crops, adopting heat-resistant varieties, and community management of water resources to adapt to rising temperatures.

**Answer 2:**

In humid zones, strategies include water management and crop diversification, while in semi-arid zones, farmer organizations focus more on drought risk management, the use of drought-resistant crops, and soil conservation. Seasonal livestock migration to less affected areas is also common in semi-arid zones.

**Answer 3:**

Limitations of adaptation strategies include dependence on limited financial resources, lack of access to modern technologies, weak coordination between communities and local authorities, and increasing uncertainty about the long-term effects of climate change, which may render some strategies obsolete.

These exercises and answer keys provide a basis for understanding the dynamics of climate change in Sahelian humid and semi-arid zones and the responses of farmer organizations. They can be adapted according to the desired level of learning.
# CHAPITRE 5. ECONOMIC INDEX OF ECOLOGICAL CHARCOAL BASED ON *PROSOPIS JULIFLORA EICHHORNIA CRASSIPES* MIX AND THEIR CARBON SEQUESTRATION POTENTIAL

Alexis Dzokom¹, Roger Djouldé Darman²

¹Department of Environmental Sciences, National Advanced School of Engineering, University of Maroua, Cameroon

²Department of Agriculture Animal Husbandry and By-Products, National Advanced School of Engineering, University of Maroua, Cameroon

## ABSTRACT

The objective of this study is to evaluate the economic quality of charcoal based on *Prosopis juliflora* linked to *Eichhornia crassipes* and to determine its index economic value. The density of the charcoal based on *Prosopis juliflora* (50≤%) and *Eichhornia crassipes* (50≥%) is 0.395±0.037g/cm³ with the average humidity rate before drying of 48.89±14.03%, a low porosity (0.17±0.01) and a low average impact resistance index of 69.37±5.93%. With an average calorific value of 17.56±0.96 kJ/kg and a specific calorific capacity of 0.596±0.004kJ/kg/K, these dry ecological charcoals fix on average 58.24±24.54% of carbon and sequester on average 1194.31±1512.21kg of CO₂/year. The average weighted mass yield of these ecological coals is 90.096±1.5136% while its technological yield is 5.076±0.288%. For an average commercial yield of 1.2535±0.0034%, the average Economic Value index would be 1.5875±0.1510, which leads to a local sales price of 238.125±22.6528 FCFA/KG (i.e. €0.36/KG).

**Keywords:** Economic value index; Ecological charcoal; *Prosopis juliflora*; *Eichhornia crassipes*

## INTRODUCTION

On the energy front, the overexploitation of wood energy, which represents one of the major environmental problems [2, 3 and 4], caused a widening of the circle of deforestation around the Sahelian towns of Maroua and Garoua [5, 6]. In the areas supplying the Sahelian town of Maroua with fuelwood (Madjina, Songonyé, Ngambarou and Kinguériwa) the decline of the bush is clear [5]. *Prosopis juliflora* is present in the Cameroonian Sahel, in humid and semi-arid areas and helps to stop desertification, control deforestation and can help alleviate wood energy shortages. In the Cameroonian Lake Chad area, *Prosopis juliflora* is one of the invasive plants and its wood could provide 45% of the energy needs of rural areas, but is not used because it is considered to be a wood whose smoke is irritating to the eyes in traditional kitchens. Studies show that in arid and semi-arid regions of India, *Prosopis juliflora* accounts for up to 70% [29] or 80–90% [1] of all domestic fuel requirements of rural populations.
However, this consumption does not specify the location, the forms, or the consumers of this energy source; which cannot facilitate planning of this energy source [7].

Furthermore, the estimated charcoal production activity would employ 150,000 people in 1991 and generate more than 50 million US dollars while contributing only 6% to the energy needs in Haiti [8]. In India, forest service's produce and market 3 million tons of *Prosopis juliflora* charcoal per year, creating on average 55,500 days of employment per man per year [9], while between 3,000 and 16,000 t /year *Prosopis juliflora* charcoal is produced in northern Peru [10]. However, charcoal is mainly consumed in urban areas and is often produced at considerable distances from the point of consumption and approximately 3 to 6 kg of *Prosopis juliflora* or *Prosopis pallida* wood is required to produce 1 kg of charcoal depending on the method used [11]. The production of ecological charcoal based on aquatic invasive plants such as *Eichhornia crassipes* in Lake Chad requires an operational and functional choice of available and free binder in order to meet the needs of poor populations in arid and semi-arid zones [12].

The objective of this study is to evaluate the economic quality of charcoal based on *Prosopis juliflora* linked to *Eichhornia crassipes* and to determine its index economic value. At the end of this study, it is expected to produce large quantities of high quality ecological charcoal with a very high energy capacity, close to that of firewood, the sale price of which would be accessible to all social strata.

# I- MATERIALS AND METHOD

## I-1)- Study sites

The study was carried out in the Lake Chad area, in the Far North of Cameroon, around 10 sites, including 5 sites which are affected by the invasion of water by *Eichhornia Crassipes* and 5 other sites on dry land which are concerned by the invasion by *Prosopis juliflora*.
<figure><img src="image_118.png" /><figcaption>Figure 1: Map of the study area</figcaption></figure>

## I-2- Sampling of biomass and preparation of ecological charcoal samples

The dry dead biomasses of *Prosopis juliflora* and *Eichhornia crassipes* were collected in bulk in nature. Then, via a manual selective sorting process described by [2], they were separated and then arranged into dry dead biomasses on the one hand and live biomasses on the other hand.

Using the methodologies developed by [12, 13, 16, 17] and [18], the very selective sorting of the raw material is preferably done manually, thanks to individual protective equipment (nose covers, gloves, etc.). The fork, the pickaxe, the rakes, the garbage excavations, the shovels were used to dig and separate the raw material from the organic deposits. Wheelbarrows and bags are tools that made it possible to collect, transport and store this raw material [19, 20, 21 and 22].

### I-2-1) Carbonization process

The carbonization was carried out following the methodology developed by [4]. It consisted of carbonizing the dry biomass in a carbonizer at a temperature between 400-600°C.

#### I-2-1-1) Mass yield taken from biomass

The mass yield makes it possible to estimate the coal production of equipment based on the mass of the product to be carbonized processed. It is defined as the mass of ecological coal produced relative to the mass of carbonized biomass. Determining this ratio requires the following operations described by [13]: For the mass yield before carbonization we have:
* Weigh all of the biomass put into the oven (Mi);

* Determine the raw humidity (H%) of the biomass;

* Mass of biomass whose raw humidity is greater than 50% (H>50%) (MBO (H>50%));

* Determine the mass of the biomass (MB), by calculation, from the initial total mass (Mi), according to the formula :

$$MB = Mi \times (MBO(H > 50\%) - \frac{H\%}{100}) \quad (1)$$

For the mass yield after carbonization we have:

* Sorting and weighing any unburned products resulting from carbonization (Mi);

* Immediate weighing of all the coal (MC).

The mass yield on anhydrous (R) expressed as a percentage is given by the formula :

$$R = 100 \times (\frac{MC}{MB-MI}) \quad (2)$$

If this fuel is wood, the quantity of anhydrous wood (BO) introduced into the system must be assessed in the same way as above. The formula for mass yield then becomes:

$$Rnet = 100 \times (\frac{MC}{MB-MI+BO}) \quad (3)$$

If this fuel is not wood, the quantity of ant energy can also be taken into account, and the following formula makes it possible to calculate the equivalent of anhydrous wood such that:

$$BO = \frac{Ecological charcoal anhydrous mass \times Ecological charcoal anhydrous LCV}{LCV anhydrous carbonized wood} \quad (4)$$

The resulting ecological charcoal samples were prepared according to the method used by [2], where each was subdivided into triplicates, marked and weighed, and brought for laboratory analysis. Moisture levels, density and calorific value were determined as described in the following sections.

### I-2-1-2) Density (D) of ecological charcoal obtained

Density was determined as the ratio of oven dry weight (gr) to volume (cm³) using equation 3. The procedure followed the technique described in [14 and 19] whereby the volume wood is first determined by immersing the samples in water for 5 days (120 h) to reach full saturation, allowing them to drain for 5 min, and measuring their diameters using a caliper. slides. The volume was calculated using equation 2:

$$Volume = \frac{\pi \times D^2 \times L}{4} \quad (5)$$

Where D = average diameter of the sample and L = length of the sample.

The samples were dried again at 100°C until reaching a constant weight. The density (D) was then calculated according to equation 3:

$$Density = \frac{Dry weight of coal}{Sample volume} \quad (6)$$

Where the dry weight of the coal is in grams and the volume of the ecological coal sample is in cm³
### I-3) Physico-chemical characterization of ecological charcoal samples based on *Prosopis juliflora* linked to *Eichhornia Crassipes*

#### I-3-1) Moisture content of ecological charcoal samples based on *Prosopis juliflora* linked to *Eichhornia Crassipes*

As part of this work, the determination of the humidity level was inspired by the methodological measurement processes developed by [25]. The humidity level expresses the water content and strongly influences the calorific value and the ignition capacity of ecological charcoal. The humidity level is obtained by the following formula:

$$W(\%) = \frac{M_{wet} - M_{dry}}{M_{wet}} \times 100 \quad (7)$$

With: W: humidity level; M wet: mass of the sample before heating; M dry: mass obtained after heating to 105°C in the oven.

#### I-3-2) Resistance index of ecological charcoal samples based on *Prosopis juliflora* linked to *Eichhornia Crassipes*

The Impact Resistance Index (IRC) or Stability Test of ecological coal is determined by the compression tests undergone by ecological coal. The compressive force of ecological coal in its cylindrical position is determined by the appearance of faults during its compression [24].

<figure><img src="image_119.png" /><figcaption>Figure 4: a)-Test of the compression force of ecological charcoal and condition for the appearance of cleavages; b) -Test of the axial compression force of ecological charcoal and condition for the appearance of cleavages [24].</figcaption></figure>

#### I-3-3) Moisture recovery content of ecological charcoal samples based on *Prosopis juliflora* linked to *Eichhornia Crassipes*

The moisture recovery test via a simple immersion test that ecological charcoal is subjected to makes it possible to characterize their potential for resistance to thermal and environmental hazards of the storage location. It consists of measuring the diameter of ecological charcoal before and after immersion in order to determine the difference in water imbibition and the percentage of inclusion of materials in ecological
charcoal [26]. It is expressed in centimeters cube (cm³) [19].

### I-3-4) Volatile matter content

The BS EN 14.774-1 protocol for determining the volatile matter of a fuel consists of weighing the dry sample then heating it under nitrogen, at a temperature between 890° and 910°C for 7 minutes in a crucible with lid and weigh it again. The formula developed by the standard method [11] makes it possible to calculate the rate of volatile matter:

$$M.O.V. = \frac{(M850^{\circ}\text{C}-M899^{\circ}\text{C})\times100}{\text{M dry}} \quad (8)$$

*With: MOV: Volatile matter content, M895°C: Mass obtained after heating to 895°C, M899°C: mass obtained after heating to 899°C*

### I-3-5) Fixed carbon content

To determine fixed carbon, the BS EN 14.774-1 protocol was used. Two parts, each weighing 1 gram, were made from the combustible briquettes, then they were introduced into an oven for calcination. One part was calcined for 10 minutes at a temperature of 550°C, while the other part was calcined for 10 minutes at a temperature of 850°C. The fixed carbon rate developed by the standard method [14] allows it to be calculated using the following formula:

$$Cf(\%) = 100 - (Hsec + Mce850^{\circ}\text{C} + Mv550^{\circ}\text{C}) \quad (9)$$

### I-4) Calorific value and energy efficiency of ecological charcoal

The method [14] and the MA protocol, 108-P.Cal. 1.0 helped to measure and calculate calorific value. The heat capacity of the bomb and tank was calculated from a test done with benzoic acid. The calorific value of the ecological charcoal samples is measured by the following equation:

$$C.V. = \frac{[1000 \times (T^{\circ}\text{f} - T^{\circ}\text{i}) \times W - (Hh \times a)]}{b} \quad (10)$$

Where C.V.: calorific value of the sample (kJ/kg); T°f: maximum final temperature of the water in the tank after ignition (°C);

#### I-4-1) Specific heat capacity

The heat capacity of coal produced depends on the temperature provided when burning a chosen quantity. For a kilo of fuel, the empirical formula to calculate the heat capacity is:

$$C_{pm} = 0,131 + 0,003867 \times T \quad (11)$$
With: C<sub>pm</sub>: specific heat mass in kJ/kg/K; T: temperature in °K. With regard to our study, we considered running drinking water.

### I-4-2) Conversion yield of plants into ecological charcoal

The conversion yield of plants into ecological charcoal consists of burning dry plant biomass which contains volatile matter from the dry plant. After carbonization, dry coal briquettes have volatile matter content of dry coal. By writing that the fixed carbon, excluding volatile matter, was preserved during pyrolysis, we deduce that the yield of pyrolysis [5] is:

$$n pyro = \frac{1-Volatile matter Dry vegetable}{1-Volatile matter dry carbon} (\%) \quad (12)$$

### I-4-3) Energy Yield of Ecological Coal

The gross Energy Yield REn expressed as a percentage is given by the formula [13]:

$$REn (\%) = \frac{MTI \times LCVC}{Bo \times LCVC_{bio raw}} \times 100 \quad (13)$$

With Bo = Weight of the entire wet biomass before loading; LCV Gross bio= Lower calorific value of gross biomass; MTI = Mass of the coal in its entirety immediately after unloading; LCV = Lower Calorific Value of coal.

## I-5) Economic Value Index of Ecological Coal (EVI)

### I-5-1) Weighted mass yield of Ecological Coal

The weighted mass yield (RMP or R80) expressed as a percentage is given by the formula [13]:

$$RMP ou R80 (\%) = Rx \frac{CFx}{80} \times 100 \quad (14)$$

With RX = Gross mass yield in percentage control during the test and at the volatile matter index x. CFx = Fixed carbon rate on anhydrous coal for the volatile matter index x

## I-6) Technological Yield of Ecological Coal

The technological yield expressed in kg/m³ is given by the formula [13]:

$$RT (\%) = \frac{MTI}{VH2O} \quad (15)$$

With MTI = Mass of the coal in total (PC) immediately after unloading; V<sub>H2O</sub> = Water volume (V) of the oven.

## I-7) Commercial performance
The commercial yield (RC) expressed as a percentage is given by the formula [13]:

$$ \text{Commercial Yield of Ecological Coal} = \frac{\text{Mass of marketable coal produced (g)}}{\text{Mass of carbonized biomass(g)}} (\%) \qquad (16) $$

The Economic Value Index of Ecological Coal (EVI) is the sum between the Commercial Yield (CY) and the Physical-Calorific Value Index of Ecological Coal (PCVI) obtained:

$$ \text{EVI} = \text{CY} + \text{PCVI} \qquad (17) $$

The Selling Price of 1kg of Ecological Charcoal is the product between the IVE and the local Price of 1kg of Charcoal

$$ \text{Sale price of 1kg of ecological charcoal} = \text{EVI} \times \text{Local price of 1kg of charcoal} \qquad (18) $$

## II-) RESULTS

### II-1) - Invasive floristic composition of the study area

On average, a total of 73.87±7.24 individuals/Hectare distributed into 7.56±1.67 genera/Hectare, 5.17±1.09 species/Hectare and 3.11±0.58 families/Hectare was recorded in the ten study sites (Table 2). The distribution according to species on dry land shows a clear dominance of *Prosopis juliflora* (i.e. 29.16±1.67 individuals/hectare) followed by *Eichhornia crassipes* on water (98,509.06±68.68 individuals/hectare). These two species alone cover 81.59% of the vegetation studied. The most represented families are those of Mimosaceae (4 species), followed by Moraceae (3 species). Caesalpineaceae, Meliaceae, Rhamnaceae, Palmeae, Sapotaceae, Annonaceae, Sterculiaceae and Bombaceae have only one species. The Shannon index reveals a low diversity of the site (0.6 bits), the Pielou fairness being equal to 0.41. This index reflects the uneven distribution of inventoried species dominated by two species such as *Prosopis juliflora* and *Eichhornia crassipes*.

<table><caption>Table 1: Floristic composition of invasive plants on the sites</caption><thead><tr><th rowspan="2">Species</th><th rowspan="2">Emission factor (gr CO<sub>2</sub>eq/Kg)</th><th colspan="4">Density (Plants / km<sup>2</sup> / season)</th><th rowspan="2">Frequenc y (%)</th><th rowspan="2">Ecological footprint (ha/person)</th></tr><tr><th>Rainy season</th><th>Max. rainy season</th><th>dry season</th><th>Min. dry season</th></tr></thead><tbody><tr><td><i>Prosopis juliflora</i></td><td>0.094</td><td>17.981±0.6<br>14<sup>f</sup></td><td>18.742±0.5<br>94<sup>a,b</sup></td><td>15.007±0.5<br>53<sup>g</sup></td><td>5.459±0.0<br>67<sup>e</sup></td><td>43.50±1.04<sup>d</sup></td><td>0.476×10<sup>-4d</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>0.743</td><td>842.375±1<br>4,118<sup>a</sup></td><td>1038.009±<br>7.186<sup>a</sup></td><td>151.573±2<br>1.171<sup>d</sup></td><td>38.735±7.116<sup>c</sup></td><td>37.56±2.07<sup>e</sup></td><td>0.012±0.04<sup>a</sup></td></tr></tbody></table>

The average density of *Prosopis juliflora* on dry land within the study sites is
17.981±0.614 plants/km² during the rainy season (May to October), with the highest peak (18.742±0.594 plants/km²) in the month of August while during the dry season (from November to April), this density is 15.007±0.553 plants/Km² with a weak peak (5.459±0.067 plants/Km²) in the month of March. The emission factor of *Prosopis juliflora* during carbonization before the manufacture of ecological charcoal is 0.0937±0.007 grams CO₂eq/Kilogram, while this emission factor after manufacture of ecological charcoal (carbonized *Prosopis juliflora* linked to clay) is 0.011±0.003 gram CO₂eq/Kilogram. The removal of 3572.286±1.428 plants of *Prosopis juliflora*, or approximately 1000 kilograms of raw material, followed by their carbonization could result in a total of 937.367±1.967 grams CO₂eq/kilograms of the ecological charcoal produced, with an ecological footprint of 0.476×10-4ha/person having been impacted during the activities to make available 735.117±6.154 Kilograms of ecological charcoal (Table 1).

The average density of *Eichhornia crassipes* on the water surface during the rainy season (May to October) is 842.375±14.118 plants/m², with the highest peak (1038.009±7.186 plants/m²) at month of August while during the dry season (November to April) is 151.573±21.171 plants/m² with a low peak (38.735±7.116 plants/m²) in the month of March. The emission factor of *Eichhornia crassipes* during carbonization before the manufacture of ecological charcoal is 0.743±0.072gram CO₂eq/Kilogram while this emission factor after manufacture of ecological charcoal is 0.0012±0.0001 gram CO₂eq/Kilogram. The cleaning of the 3900 kilograms followed by their carbonization results in a total emission of 1768.7 grams CO₂eq (i.e. 1.7687 kilograms CO₂eq) with an ecological footprint of 0.012±0.004 ha/person having been impacted during the ecological charcoal production activities (Table 1).

## II-2) - Sampling of biomass and preparation of ecological charcoal samples

### II-2-1) - Living biomass and CO₂ stock

In the study sites, the average diameter of the trunks and stems of the species studied varies. The average diameter of the main trunks of *Prosopis juliflora* is 23.404±5.253 cm. The basal area covered by *Prosopis juliflora* is 3.978±1.391 m²/Ha with a coverage of 955.8±1.391m²/Ha and a biomass volume of 7.956±0.512 m³.

The average diameter of the main stems of *Eichhornia crassipes* is 5.914±0.893 cm with a covered basal area of 2.872±0.449 m²/Ha and a biomass volume of 1.436±0.603 m³ (Table 2).

<table><caption>**Table 2: Determination of aboveground biomass (BA)**</caption><thead><tr><td>Species</td><td>Average diameter of the main trunks (and stems) of the species (cm)</td><td>Basal area covered by the species (m²/Ha)</td><td>Density (Ind. No./Km²)</td><td>Volume of species biomass (m³)</td></tr></thead></table>
<table><tr><td><i>Prosopis juliflora</i></td><td>23.404±5.253<sup>a,g</sup></td><td>3.978±1.391<sup>d</sup></td><td>16.507±1.768<sup>a</sup></td><td>7.956±0.512<sup>e,f</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>5.914±0.893<sup>e</sup></td><td>2.872±0.449<sup>c</sup></td><td>151.573±21.171<sup>b</sup></td><td>1.436±0.603<sup>d</sup></td></tr></table>

The total average biomass of *Prosopis juliflora* and *Eichhornia crassipes* studied is variable. However, the total average biomass of *Prosopis juliflora* is 16.80±1.54 T/Ha, lower than the total average biomass of *Eichhornia crassipes* which is 197.77±0.79 T/Ha. The average carbon stock by *Prosopis juliflora* is 7.896±0.183 T/Ha with an average Carbon Equivalent of 15.06±0.35 T/Ha while the average carbon stock by *Eichhornia crassipes* is 92.952±1.547 T/Ha with an average Carbon Equivalent of 22.36±0.13 T/Ha (Table 3).

<table><caption>Table 3: Total living biomass and carbon stock of each species</caption><thead><tr><th>Species</th><th>Aboveground biomass of species (BA,T/Ha)</th><th>Belowground biomass of species (BS,T/Ha)</th><th>Total biomass of species (BT,T/Ha)</th><th>Carbon stock of species (SC, T/Ha)</th><th>Carbon equivalent (EqC, T/Ha)</th></tr></thead><tbody><tr><td><i>Prosopis juliflora</i></td><td>2,65±0,71<sup>a</sup></td><td>14,15±0,83<sup>a</sup></td><td>16,80±1,54<sup>a</sup></td><td>7,896±0,183<sup>f</sup></td><td>15,06±0,35<sup>d</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>67,15±0,03<sup>c</sup></td><td>130,62±0,76<sup>b</sup></td><td>197,77±0,79<sup>a</sup></td><td>92,952±1,547<sup>a</sup></td><td>22,36±0,13<sup>e</sup></td></tr></tbody></table>

## II-2-2) - Dry dead biomass and preparation of raw material

The average weight of the trunk of the dry dead biomass of *Prosopis juliflora* is 17.02±3.00 kg/m² while its average weight is 58.27±4.56 kg/m². The average LCV of the dry dead biomass of *Prosopis juliflora* is 17.92±0.02 MJ/kg with its average dry stock is 75.29±6.18 kg/m² and the average stock of its bioenergy is 1.35±0.101 GJ/m². These values are distributed in the table below:

<table><caption>Table 4: Dry dead biomass and bioenergy stock</caption><thead><tr><th>Site</th><th>Species</th><th>Trunk Weight (kg/m²)</th><th>Plant Weight (kg/m²)</th><th>LCV (MJ/kg)</th><th>Biomass stock (kg/m²)</th><th>Bioenergy stock (GJ/m²)</th></tr></thead><tbody><tr><td rowspan="2">Koussérie</td><td><i>Prosopis juliflora</i></td><td>16.27±0.65<sup>a</sup></td><td>53.16±1.44<sup>a</sup></td><td>17.957±1.042<sup>f</sup></td><td>69.43±1.04<sup>a,h</sup></td><td>1.246±0.754<sup>d</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>11.05±0.63<sup>c</sup></td><td>51.69±0.98<sup>a</sup></td><td>18,543±7,767<sup>d</sup></td><td>62.74±0.80<sup>g</sup></td><td>1.163±0.387<sup>a</sup></td></tr><tr><td rowspan="2">Makary</td><td><i>Prosopis juliflora</i></td><td>17.89±0.27<sup>a</sup></td><td>61.86±1.56<sup>a</sup></td><td>17.952±1.088<sup>d</sup></td><td>79.75±0.91<sup>a,b</sup></td><td>1.431±0.672<sup>e</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>11.15±0.23<sup>c</sup></td><td>57.96±0.69<sup>a</sup></td><td>18.521±7.605<sup>a</sup></td><td>69.11±0.46<sup>d</sup></td><td>1.279±0.986<sup>f</sup></td></tr><tr><td rowspan="2">Hilé Alifa</td><td><i>Prosopis juliflora</i></td><td>12.65±0.71<sup>a</sup></td><td>58.16±1.31<sup>a</sup></td><td>17.959±0.057<sup>f</sup></td><td>70.81±1.01<sup>e</sup></td><td>1.271±0.676<sup>d</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>16.15±0.03<sup>c</sup></td><td>57.77±0.79<sup>a</sup></td><td>18,508±7,764<sup>c</sup></td><td>73.92±0.41<sup>g</sup></td><td>1.368±0.111<sup>a</sup></td></tr><tr><td rowspan="2">Blangoua</td><td><i>Prosopis juliflora</i></td><td>19.65±0.34<sup>a</sup></td><td>61.89±1.71<sup>a</sup></td><td>17.898±1.091<sup>b</sup></td><td>81.54±1.02<sup>e</sup></td><td>1.459±0.653<sup>g</sup></td></tr><tr><td><i>Eichhornia crassipes</i></td><td>16.15±0.13<sup>c</sup></td><td>57.77±0.79<sup>a</sup></td><td>18.558±7.955<sup>a</sup></td><td>73.92±0.46<sup>h</sup></td><td>1.371±0.807<sup>b</sup></td></tr><tr><td>Darack</td><td><i>Prosopis juliflora</i></td><td>18.65±0.73<sup>a</sup></td><td>56.27±1.11<sup>a</sup></td><td>17.892±1.049<sup>c</sup></td><td>74.92±0.92<sup>a</sup></td><td>1.340±0.468<sup>e</sup></td></tr></tbody></table>
<table><tr><td><i>Eichhornia crassipes</i></td><td>16.15±0.59<sup>c</sup></td><td>47.17±0.79<sup>a</sup></td><td>18,498±7,785<sup>d</sup></td><td>63.32±0.69<sup>d</sup></td><td>1.171±0.293<sup>h</sup></td></tr></table>

The average weight of the stems of the dry dead biomass of *Eichhornia crassipes* is 14.13±3.50 kg/m² while its average weight is 54.47±4.06 kg/m². The average LCV of the dry dead biomass of *Eichhornia crassipes* is 18.52±0.02 MJ/kg with its average dry stock is 72.22±6.19 kg/m² and the average stock of its bioenergy is 1.31±0.103 GJ/m². These values are distributed in table 5 below. A total of 5.78 kilograms of dry dead biomass was obtained from the carbonization of a total of 15.42 kilograms of wet dead biomass, distributed as follows:

<table><caption>**Table 5: Preparation of raw materials**</caption><thead><tr><td>Raw material</td><td>Weight before drying (Kg)</td><td>Weight after drying (Kg)</td></tr></thead><tbody><tr><td>Dry dead biomass of <i>Prosopis juliflora</i></td><td>7.71</td><td>4.24</td></tr><tr><td>Dry dead biomass of <i>Eichhornia crassipes</i></td><td>7.71</td><td>1.54</td></tr></tbody></table>

The total amount of carbonized raw material used in this study was adjusted to 5 kilograms, consisting of the dry dead biomass of carbonized *Prosopis juliflora* (2.50 kilograms) and the dry dead biomass of carbonized *Eichhornia crassipes* (2.50 kilograms). The overall preparation process was carried out according to the following diagram:
<figure><img src="image_120.png" /><figcaption>Figure 2: Raw material processing diagram</figcaption></figure>

II-2-1) Carbonization process and proportion of binder added

The diagram of the carbonization process of *Prosopis juliflora* and *Eichhornia crassipes* in this study is as follows.
<figure><img src="image_121.png" /><figcaption>Figure 3: Scheme for producing ecological charcoal based on Prosopis juliflora and Eichhornia crassipes</figcaption></figure>

The clay binder sifted through the 0.25mm/mm mesh was used and represents 8% of the biomass used to mold

## II-2-2) Mass yield taken from biomass

The carbonization test was carried out 10 times. Each time, the mass yields were evaluated. The mass yield made it possible to estimate the potential carbon production of the dry dead biomasses of *Prosopis juliflora* and the dry dead biomasses of *Eichhornia crassipes* to be carbonized treated. The determination of the mass yields was recorded in the following table:

<table><caption>Table 6: Mass yield before and after carbonization of raw materials</caption><thead><tr><td>Raw material</td><td>Weight after carbonization (Kg)</td><td>Mass yield before carbonization (%)</td><td>Mass yield after carbonization (%)</td><td>Net mass yield of ecological charcoal (%)</td></tr></thead><tbody><tr><td>Dry dead biomass of <i>Prosopis juliflora</i></td><td>1.03</td><td>36.57±2.62</td><td>25.91 ±0.76</td><td>91.75±3.78</td></tr><tr><td>Dry dead biomass of <i>Eichhornia crassipes</i></td><td>1.01</td><td>16.02 ±1.59</td><td>94.35±0.84</td><td>98.42±4.95</td></tr></tbody></table>

The mass yield before carbonization of biomasses whose raw humidity is greater than 50% (H>50%) is 26.29± 2.10% while the mass yield after carbonization of biomasses is 60.13± 0.80%
Concerning the dry dead biomasses of *Prosopis juliflora*, the quantity of wood introduced into the metal carbonizer made it possible to obtain the net carbonization mass yield of 91.75±3.78% while for the dry dead biomasses of *Eichhornia crassipes* the quantity of ant energy in the metal carbonizer made it possible to obtain the net mass carbonization yield of 98.42±4.95%:

Then, 15 samples of ecological charcoal of three types of dimensions were made for each of the two species, and composite samples of ecological charcoal based on *Prosopis juliflora* linked to *Eichhornia crassipes* were made and presented in Table 7.:

<table><caption>Table 7: Sized samples of ecological coal</caption><thead><tr><th rowspan="2">Raw material</th><th colspan="6">Samples of Ecological Coal</th></tr><tr><th>L: 5.3±0.9 cm</th><th>D: 2.7±0.5 cm</th><th>L: 7.4 ±0.3 cm</th><th>D: 2.7±0.5 cm</th><th>L: 10.6±0.7 cm</th><th>D: 2.7±0.5 cm</th></tr></thead><tbody><tr><td>Dry dead biomass of <i>Prosopis juliflora</i></td><td>3</td><td></td><td>3</td><td></td><td>3</td><td></td></tr><tr><td>Dry dead biomass of <i>Eichhornia crassipes</i></td><td>3</td><td></td><td>3</td><td></td><td>3</td><td></td></tr><tr><td>Dry dead biomass of <i>Prosopis juliflora</i> (25%) + <i>Eichhornia crassipes</i> (75%)</td><td>3</td><td></td><td>3</td><td></td><td>3</td><td></td></tr><tr><td>Dry dead biomass of <i>Prosopis juliflora</i> (50%) + <i>Eichhornia crassipes</i> (50%)</td><td>3</td><td></td><td>3</td><td></td><td>3</td><td></td></tr><tr><td>Dry dead biomass of <i>Prosopis juliflora</i> (75%) + <i>Eichhornia crassipes</i> (25%)</td><td>3</td><td></td><td>3</td><td></td><td>3</td><td></td></tr></tbody></table>

With L= Length of the sample in centimeters (cm) and D= Diameter of the sample in centimeters (cm)

These samples were prepared according to the method used by [2], where each was subdivided into triplicates, marked and weighed, and taken for laboratory analysis. Moisture levels, density and calorific value were determined as described in the following sections. The clay binder was added in the following proportions:

<table><caption>Table 8: Proportion of raw material-binder mixed</caption><thead><tr><th>Proportion of clay binder (%)</th><th>2</th><th>5</th><th>8</th><th>10</th></tr></thead><tbody><tr><td>Carbonized and ground <i>Prosopis juliflora</i> (%)</td><td>100/0</td><td>100/0</td><td>100/0</td><td>100/0</td></tr><tr><td><i>Eichhornia crassipes</i> carbonized and ground (%)</td><td>100/0</td><td>100/0</td><td>100/0</td><td>100/0</td></tr><tr><td rowspan="3"><i>Prosopis juliflora</i> and <i>Eichhornia crassipes</i> carbonized and ground (%)</td><td>25/75</td><td>25/75</td><td>25/75</td><td>25/75</td></tr><tr><td>50/50</td><td>50/50</td><td>50/50</td><td>50/50</td></tr><tr><td>75/25</td><td>75/25</td><td>75/25</td><td>75/25</td></tr></tbody></table>

## II-2-3) Density (D) of ecological charcoal obtained

The variation between 0.372±0.053 g/cm³ and 0.405±0.094 g/cm³ indicates that there is significantly a variation in level p<0.05 (F (d_f=9) =11.528, p=0.0001) for the density. The density of ecological charcoal obtained from *Prosopis juliflora* (50≤ %) and *Eichhornia crassipes* (50≥ %) carbonized and ground is 0.395±0.037g/cm³ while the
density of the charcoal obtained from *Prosopis juliflora* (50≥%) and *Eichhornia crassipes* (50≤%) carbonized and ground is 0.385±0.083g/cm³. The ecological charcoal based on *Prosopis juliflora* (50%) and *Eichhornia crassipes* (50%) carbonized and ground (% linked to % clay) is 0.391±0.095 g/cm³

<table><caption>**Table 9: Density of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* bound to clay**</caption><thead><tr><th>Sample of ecological charcoal</th><th>Length (cm)</th><th>Diameter (cm)</th><th>Volume (cm³)</th><th>Weight of dry coal sample (g)</th><th>Density (g/cm³)</th></tr></thead><tbody><tr><td><i>Prosopis juliflora</i> charred and ground (100/0%)</td><td>5.343±0.932</td><td>2.678±0.345</td><td>30.329±3.049</td><td>11.226±3.054</td><td>0.372±0.053</td></tr><tr><td><i>Eichhornia crassipes</i> carbonized and ground (100/0%)</td><td>5.273±0.798</td><td>2.734±0.495</td><td>30.327±3.047</td><td>11.838±3.056</td><td>0.396±0.061</td></tr><tr><td><i>Prosopis juliflora</i> and <i>Eichhornia crassipes</i> carbonized and ground (25/75%)</td><td>7.417±0.283</td><td>2.677±0.385</td><td>42.351±2.809</td><td>16.945±1.842</td><td>0.405±0.094</td></tr><tr><td><i>Prosopis juliflora</i> and <i>Eichhornia crassipes</i> carbonized and ground (50/50%)</td><td>7.394±0.276</td><td>2.667±0.485</td><td>42.352±2.808</td><td>16.515±1.843</td><td>0.397±0.091</td></tr><tr><td><i>Prosopis juliflora</i> and <i>Eichhornia crassipes</i> carbonized and ground (75/25%)</td><td>10.611±0.647</td><td>2.657±0.485</td><td>60.659±1.957</td><td>23.051±2.914</td><td>0.382±0.026</td></tr></tbody></table>

## II-3) Physico-chemical characterization of ecological charcoal samples based on *Prosopis juliflora* linked to *Eichhornia crassipes*

The average humidity level before drying (48.89±14.03%) induces low average surface/volume ratios of ecological charcoal of 23.20±0.48 mm⁻¹, low porosity (0.17±0.01) and a low average impact resistance index of ecological charcoal (69.37±5.93%). The average rate of fixed carbon (58.24±24.54%) and the average rate of volatile matter in the coal (57.72±20.29%) induce a low average rate of moisture recovery in the ecological charcoal (1, 56±0.16%) after storage.

<caption>**Table 10: Physico-chemical characteristics**</caption>
<table><thead><tr><th>Settings</th><th>Prosopis juliflora carbonized and ground (100/0%)</th><th>Eichhornia crassipes carbonized and ground (100/0%)</th><th>Prosopis juliflora and Eichhornia crassipes carbonized and ground (25/75%)</th><th>Prosopis juliflora and Eichhornia crassipes carbonized and ground (50/50%)</th><th>Prosopis juliflora and Eichhornia crassipes carbonized and ground (75/25%)</th></tr></thead><tbody><tr><td>Moisture content after drying (%)</td><td>7.237±1.063</td><td>3.792±1.054</td><td>6.835±0.076</td><td>7.117±0.372</td><td>7.602±1.006</td></tr><tr><td>Ecological charcoal surface/volume ratio (mm<sup>-1</sup>)</td><td>22.68 ± 3.97</td><td>23.55±2.51</td><td>22.68±1.64</td><td>23.53±1.76</td><td>23.57±3.07</td></tr><tr><td>Density of charcoal (gr/ml)</td><td>Skeletal (ρ<sub>sq</sub>)</td><td>354.48±203.65</td><td>350.57±250.71</td><td>356.835±100.07</td><td>351.03±110.09</td><td>350.27±80.37</td></tr><tr><td>Ecological charcoal (gr/ml)</td><td>Apparent (ρ<sub>app</sub>)</td><td>438.5±32.06</td><td>423.29±20.85</td><td>427.36±05.65</td><td>427.18±58.72</td><td>422.94±30.61</td></tr><tr><td>Porosity</td><td></td><td>0.63</td><td>0.74</td><td>-0.29</td><td>-0.58</td><td>-0.67</td></tr><tr><td>Ecological charcoal impact resistance index (%)</td><td></td><td>76.53±4.11</td><td>74.66±2.73</td><td>64.26±0.65</td><td>63.65±0.87</td><td>67.73±0.46</td></tr><tr><td>Ecological charcoal moisture recovery content (%)</td><td></td><td>1.34±0.67</td><td>1.65±0.14</td><td>1.76±0.36</td><td>1.49±0.52</td><td>1.55±0.72</td></tr><tr><td>Ecological charcoal volatile matter content (%)</td><td></td><td>76.97±1.63</td><td>26.87±1.43</td><td>49.25±0.53</td><td>62.74±0.39</td><td>72.79±0.84</td></tr><tr><td>Fixed carbon content of ecological charcoal (%)</td><td></td><td>19.39±1.82</td><td>84.43±1.29</td><td>52.55±1.76</td><td>64.86±1.26</td><td>69.98±1.79</td></tr></tbody></table>

## II-4) Energy efficiency of ecological charcoal

With an average calorific value of ecological charcoal of 17.56±0.96 kJ/kg, the specific heat capacity of ecological charcoal is 0.596±0.004 kJ/kg/K. The average conversion efficiency of plants into ecological charcoal is 1.585±0.807% with an energy production during the combustion of coal of 8360 Joules.

<table><caption>Table 11: Fuel energy efficiency tests</caption><thead><tr><th>Test Parameters of ecological charcoal</th><th>Prosopis juliflora carbonized</th><th>Eichhornia crassipes carbonized</th><th>Prosopis juliflora and Eichhornia crassipes carbonized</th><th>Prosopis juliflora and Eichhornia crassipes carbonized</th><th>Prosopis juliflora and Eichhornia crassipes carbonized</th></tr></thead></table>
<table><thead><tr><th></th><th>and ground (100/0%)</th><th>and ground (100/0%)</th><th>crassipes carbonized and ground (25/75%)</th><th>crassipes carbonized and ground (50/50%)</th><th>crassipes carbonized and ground (75/25%)</th></tr></thead><tbody><tr><td>Calorific value of ecological charcoal (kJ/kg)</td><td>17.987±0.208</td><td>15.876±0.759</td><td>17.794±0.123</td><td>17.845±0.283</td><td>18.311±0.357</td></tr><tr><td>Specific heat capacity of ecological charcoal (kJ/kg/K)</td><td>0.603</td><td>0.595</td><td>0.599</td><td>0.595</td><td>0.591</td></tr><tr><td>Energy of combustion of ecological charcoal (Joules)</td><td>8360</td><td>4180</td><td>4180</td><td>4180</td><td>12540</td></tr><tr><td>Conversion yield of plants into ecological charcoal (%)</td><td>1.007</td><td>2.957</td><td>1.585</td><td>1.239</td><td>1.065</td></tr></tbody></table>

## II-8) Economic Value Index of ecological charcoal (EVI)

The average weighted mass yield of ecological charcoal is 90.096±1.5136% while its technological yield is 5.076±0.288%. The price of coal varies between 100 FCFA/KG (0.15 EUR) and 200 FCFA/KG (0.30 EUR) with an average of around 150 FCFA/KG (0.23 EUR) [2]. The average commercial yield of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 1.2535±0.0034% with an average Economic Value index of 1.5875±0.1510, which implies that the local selling price of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 238.125±22.6528 FCFA/KG (0.36 FCFA/KG).

<table><caption>Table: Economic Value Index of ecological charcoal</caption><thead><tr><th>Test Parameters of</th><th><i>Prosopis juliflora</i> carbonized and</th><th><i>Eichhornia crassipes</i> carbonized and</th><th><i>Prosopis juliflora</i> and <i>Eichhornia</i></th><th><i>Prosopis juliflora</i> and <i>Eichhornia</i></th><th><i>Prosopis juliflora</i> and <i>Eichhornia</i></th></tr></thead></table>
<table><thead><tr><th>ecological charcoal</th><th>ground (100/0%)</th><th>ground (100/0%)</th><th>crassipes carbonized and ground (25/75%)</th><th>crassipes carbonized and ground (50/50%)</th><th>crassipes carbonized and ground (75/25%)</th></tr></thead><tbody><tr><td>Weighted mass yield of ecological charcoal (%)</td><td>91.15±6.65<sup>a</sup></td><td>92.11±4.87<sup>a, c</sup></td><td>88.67±7.02<sup>d</sup></td><td>89.83±9.06<sup>b</sup></td><td>88.72±4.07<sup>e, c</sup></td></tr><tr><td>Technological Yield of ecological coal (%)</td><td>4.76±0.57<sup>b</sup></td><td>4.76±0.53<sup>b, f</sup></td><td>5.30±0.77<sup>d, h</sup></td><td>5.27±0.96<sup>g</sup></td><td>5.29±0.75<sup>i, b</sup></td></tr><tr><td>Commercial Yield (%)</td><td>1.259±0.046<sup>c</sup></td><td>1.253±0.016<sup>i</sup></td><td>1.252±0.067<sup>b</sup></td><td>1.251±0.078<sup>b</sup></td><td>1.251±0.073<sup>d</sup></td></tr><tr><td>Physical- Calorific Value Index of ecological charcoal</td><td>0.296±0.077<sup>d</sup></td><td>0.593±0.062<sup>b</sup></td><td>0.278±0.037<sup>a</sup></td><td>0.305±0.041<sup>k</sup></td><td>0.198±0.091<sup>c</sup></td></tr><tr><td>Economic Value Index of ecological charcoal (EVI)</td><td>1.555±0.046<sup>b</sup></td><td>1.846±0.018<sup>e</sup></td><td>1.530±0.065<sup>e</sup></td><td>1.556±0.071<sup>b</sup></td><td>1.449±0.073<sup>c</sup></td></tr><tr><td>Local selling price of ecological coal (FCFA)</td><td>233.31±77.64<sup>a</sup></td><td>276.91±75.07<sup>b</sup></td><td>229.59±77.06<sup>i</sup></td><td>233.41±75.07<sup>c</sup></td><td>217.39±70.57<sup>f</sup></td></tr></tbody></table>

## DISCUSSION

The total average biomass of *Prosopis juliflora* is 16.80±1.54 T/Ha, lower than the total average biomass of *Eichhornia crassipes* which is 197.77±0.79 T/Ha. *Prosopis Juliflora* biomass yield estimates include 7-20 t/ha/ year in the USA [36], 6-12 t/ha/year in Kenya [31], 11-20 t/ha/ year in India [32] and 10-16 m3/ha/ year in Ethiopia [35].

The average weighted mass yield of Ecological Charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 90.096±1.5136% while its technological yield is 5.076±0.288%. According to [30] of *Prosopis Juliflora* biomass, when the pyrolysis final temperature is increased from 400°C to 21 600°C, the mass yield of charcoal decreases from 33.8 % to 27.2 %. The Sustainable Energy for All (SE4ALL) Action Agenda that targets improved charcoal mass yield from 11% (in 2015) to 15% by 2020 and 18% by 2030, covers an expected contribution of 30% reduction of the predicted gap between supply and demand, representing 630,000 tons of wood (SE4ALL, 2015) [33].

Arid zones presently contain the lowest levels of carbon in the world on a per hectare basis, and it is necessary to consider the role of arid zone forests in carbon sequestration on a regional and global level [11]. In the present study, the average carbon stock by *Prosopis juliflora* is 7.896±0.183 T/Ha/year with an average Carbon Equivalent of 15.06±0.35 T/Ha/year while the average carbon stock by *Eichhornia*
*crassipes* is 92.952±1.547 T/Ha/year with an average Carbon Equivalent of 22.36±0.13 T/Ha/year. [11] estimate that Prosopis plantations could sequester carbon in excess of 1000 kg/ha/yr, with a yet unseen value in the emerging global market for 'carbon credits'.

The price of coal varies between 100 FCFA/KG (0.15 EUR) and 200 FCFA/KG (0.30 EUR) with an average of around 150 FCFA/KG (0.23 €/KG) [2]. In the present study, the average commercial yield of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 1.2535±0.0034% with an average Economic Value Index of 1.5875±0.1510, which means that the local selling price of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 238.125±22.6528 FCFA/KG (0.36 €/KG). According to [34], in Kenya, the average price per bag ranges from between KES 400-450 (USD 3.60-4.50) at the producer level, and a kiln can produce 1-15 bags of charcoal, depending on the size of the kiln. [11] indicate that, collectors in Peru earn an equivalent of less than US$5/day, as during the production season charcoal a very low price because of their abundance (e.g. US$27/t in February 1995).

## CONCLUSION

The main objective of this study was to evaluate the quality of ecological charcoal based on *Prosopis juliflora* related to *Eichhornia crassipes* and to determine its indicator value. The collection and preparation of samples of ecological charcoal based on the dry dead biomass of *Prosopis juliflora* and *Eichhornia crassipes* made it possible to collect in bulk in nature 16.80±1.54 T/Ha of *Prosopis juliflora* and on average 197, 77±0.79 T/Ha of *Eichhornia crassipes*. The density of the charcoal obtained from *Prosopis juliflora* (50≤ %) and *Eichhornia crassipes* (50≥ %) carbonized and ground is 0.395±0.037g/cm³ while the density of the charcoal obtained from *Prosopis juliflora* (50≥ %) and *Eichhornia crassipes* (50≤ %) carbonized and ground is 0.385±0.083g/cm³. With an average calorific value of ecological coal of 17.56±0.96 kJ/kg, the specific heat capacity of ecological coal is 0.596±0.004 kJ/kg/K. The average conversion efficiency of plants into ecological coal is 1.585±0.807% with an energy production during the combustion of coal of 8360 Joules. The Physical-Calorific Value Index of Coal (PCVI) was calculated and analyzed using the Pearson coefficient (r=0.859, n=30, p=0.049) with a coefficient of determination of 85% and made it possible to observer a variation between 0.198±0.091 and 0.593±0.062. The physicochemical characterization of fuel samples based on *Prosopis juliflora* linked to *Eichhornia Crassipes* made it possible to obtain an average humidity level before drying (48.89±14.03%), a low porosity (0.17± 0.01) and a low average impact resistance index of coal (69.37±5.93%). The average fixed carbon (58.24±24.54%) and the average rate of volatile matter in the coal (57.72±20.29%) induce a low average rate of moisture recovery in the coal (1.56 ±0.16%) after storage. The dry ecological charcoal produced sequesters on average 1194.31±1512.21kg of
CO2/Ha/year. The average weighted mass yield of ecological charcoal is 90.096±1.5136% while its technological yield is 5.076±0.288%. The average commercial yield of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 1.2535±0.0034% with an average Economic Value index of 1.5875±0.1510, which implies that the local selling price of ecological charcoal based on carbonized and ground *Prosopis juliflora* and *Eichhornia crassipes* is 238.125±22.6528 FCFA/KG (i.e. 0.36±0.07€/KG and/or 0.34± 0.085 US Dollars/kg in 2024).

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# EXERCISES AND CORRECTIONS ON THE ECONOMIC INDEX OF ECOLOGICAL COAL BASED ON THE PROSOPIS JULIFLORA EICHHORNIA CRASSIPES MIX AND CARBON SEQUESTRATION POTENTIAL

## Exercise 1: Calculation of the Economic Index of Ecological Coal

**Question 1:** Define the Ecological Coal Economic Index (EIC). What are the criteria that influence this index in the context of a base composed of Prosopis juliflora and Eichhornia crassipes?

**Question 2:** Give a simplified formula to calculate the Economic Index of Ecological Coal (EIC) considering production costs and environmental benefits. Apply this formula using the following values:

- Cost of producing charcoal from *Prosopis juliflora*: 50 USD/ton

- Cost of producing charcoal from *Eichhornia crassipes*: 30 USD/ton

- Environmental added value per ton of coal from *Prosopis juliflora*: 150 USD

- Environmental added value per ton of coal from *Eichhornia crassipes*: 80 USD

## Correction 1:

### Answer 1:

The Ecological Coal Economic Index (EIC) measures the profitability of ecological coal by taking into account both production costs and environmental benefits. Criteria influencing this index include:

- Production costs of raw materials (*Prosopis juliflora* and *Eichhornia crassipes*).

- The costs of transformation into coal.

- Environmental benefits associated with the use of coal, such as carbon sequestration and reduction of greenhouse gas emissions.

### Answer 2:

The simplified formula for calculating the EIC is:

$$EIC = \frac{\text{Environmental added value} - \text{Production cost}}{\text{Production cost}}$$

For *Prosopis juliflora*:
$$EIC_{Prosopis juliflora} = \frac{150 - 50}{50} = \frac{100}{50} = 2$$

For *Eichhornia crassipes*:

$$EIC_{Eichhornia crassipes} = \frac{80 - 30}{30} = \frac{50}{30} \approx 1.67$$

Thus, the EIC is 2 for ecological charcoal based on *Prosopis juliflora* and around 1.67 for charcoal based on *Eichhornia crassipes*.

## Exercise 2: Assessment of Carbon Sequestration Potential

**Question 1:** Explain how carbon sequestration potential is measured for *Prosopis juliflora* and *Eichhornia crassipes* biomasses.

**Question 2:** Suppose that the biomass of *Prosopis juliflora* sequesters 1.2 tons of CO₂ per ton of coal produced and that the biomass of *Eichhornia crassipes* sequesters 0.8 tons of CO₂ per ton of coal produced. Calculate the total quantity of CO₂ sequestered for a production of 100 tons of coal from each biomass.

**Question 3:** Discuss the factors that may influence the carbon sequestration potential of the biomasses in question.

**Correction 2:**

**Answer 1:**

Carbon sequestration potential is measured by quantifying the amount of carbon dioxide (CO₂) captured and stored by biomass during its growth and after its transformation into coal. This usually involves:

- Measure the quantity of biomass produced.

- Estimate the proportion of carbon stored in this biomass.

- Calculate the quantity of CO₂ associated with biomass, using specific conversion coefficients.

**Answer 2:**

For *Prosopis juliflora*:

$$CO_{2 \text{ sequestered}} = \frac{1,2 \text{ tons CO}_2}{1 \text{ ton charbon}} \times 100 \text{ tons charbon} = 120 \text{ tons CO}_2$$

For *Eichhornia crassipes*:

$$CO_{2 \text{ sequestered}} = \frac{0,8 \text{ tons CO}_2}{1 \text{ ton charbon}} \times 100 \text{ tons charbon} = 80 \text{ tons CO}_2$$

Therefore, 120 tons of CO₂ are sequestered for 100 tons of charcoal based on *Prosopis juliflora* and 80 tons of CO₂ for 100 tons of charcoal based on *Eichhornia crassipes*.

**Answer 3:**
Factors influencing carbon sequestration potential include:

- **Type of biomass:** Different biomasses have varying carbon sequestration capacities depending on their carbon density and growth rate.

- **Growing conditions:** Environmental conditions, such as soil, water, and climate, affect the ability of biomass to capture and store carbon.

- **Transformation methods:** Processes for converting biomass into coal can influence the amount of carbon sequestered, depending on their efficiency and technology.

- **Agricultural management and practices:** Crop management practices, such as rotations and soil amendments, can also affect the ability of biomass to sequester carbon.

These exercises provide a better understanding of the economic and environmental aspects linked to the production of ecological charcoal from *Prosopis juliflora* and *Eichhornia crassipes*.

# CHAPITRE 6. IMPACT OF THE PROLIFERATION OF INVASIVE PLANTS ON BIODIVERSITY AND WOMEN'S
SOCIO-ECONOMIC ADAPTATION STRATEGIES IN THE
LAKE CHAD AREA

Alexis DZOKOM

SAHEL NATURE CONSULTING FOR COMMUNITIES, Sahelian Zone Office, Cameroon
Department of Geography, Faculty of Art, Letter and Social Sciences, University of Maroua,
Cameroon

**Abstract**

The increase in the magnitude of the effects of the invasion of environments by prolific invasive plants which impact biodiversity, eliminate certain major economic activities while increasing social challenges, women are increasingly vulnerable to climate change, The study of the impact of the proliferation of invasive plants on biodiversity and the socio-economic adaptation strategies of women in the Lake Chad area could help in the medium and long term, as a decision-making tool. The objective of this study is to determine the effect of *Prosopis Juliflora* and *Eichhornia crassipes* on biodiversity and the socio-economic adaptation strategies of women in the Lake Chad area. Taking floristic data on site made it possible to carry out the floristic inventory based on the Braun-Blanquet dominance abundance coefficients and the faunal inventory inspired and updated by the Biosedimentary Index (BSI) and Lake Chad Biotic Index (LCBI) methods. The study area was digitized and produced using ArcGis. The raw data were analyzed and formatted with Microsoft Office Excel software and imported as text files (separator: tab) into R and SPSS software. On an average of 4,167±2,786 sampling points, an average of 165,667±2,804 *Eichhornia crassipes* plants was observed, with an average abundance-dominance index of 3.833±1.169 and an average recovery rate of all the area of Lake Chad Cameroon which is 53.575±26.621%. However, the average regularity on the waters of Lake Chad is 0.598±0.217, higher in Makary (1.000) and lower in Blangoua (0.386). The average frequency of *Eichhornia Crassipes* in the waters of Lake Chad Cameroon is 16.7±0.11%: the highest is that of Makary (36%), while those observed in Darak (08) and Hilé Alifa (08) are weak. Women in the Lake Chad area and northern Cameroon carry out mainly agricultural subsistence activities. In any season on the water, the average rate of cleaning of spaces on the banks of Lake Chad for agricultural purposes is 8.6±0.55% while the average rate of use of methods for cleaning the bottom of the Lake Chad is 2.8±0.89% Sahelian semi-arid zone within the GIC and women's association. The transformations and sales of products carried out within the GICs is 12.32±7.23 Kilogram/Season/woman within the associations and 04.82±03.33 Kilogram/Season/woman within the GICs. The social strategy to adapt field production during the rainy season indicates that the average rate of diversification of forms of mutual aid is 25.80±3.27% in associations and 22.20±2.77% in GICs, while that
the average rate of donation requests in the form of agricultural materials or support, seeds and nurseries is 85.00±9.13% in association and 89.60±5.02% in GIC.

**Keys words:** Invasive Plants, Biodiversity, Women, Adaptation Strategies, Lake Chad

**Introduction**

In recent years, many rivers and their tributaries have been invaded by invasive plants, notably *Eichhornia crassipes* (Tchiaze and Priso, 2016): this is the case in Cameroon of Lake Chad and the Lagdo water retention dam. In the case of the Lake Chad area, in addition to the invasion of waters by *Eichhornia crassipes*, there is also the invasion of dry land by *Prosopis juliflora*, and ecological and socio-economic corollaries. In addition to the invasion of water and arable land by invasive plants, the Lake Chad area and its surroundings are also subject to the ravages of desertification where the soil and the productivity of seasonal plants, from year to year, decline because of the widespread effects of climate change in the Sahel. Furthermore, the cost of living and in particular chemical fertilizers are becoming more and more expensive on local markets while the floral and faunal resources of village ponds, tributaries of Lake Chad, rivers, reservoirs, wetlands, channels, drains, etc. are being replaced by *Prosopis juliflora* and *Eichhornia crassipes*, thus disturbing the survival of local biodiversity with a lot of environmental damage.

*Eichhornia crassipes* consists of high biomass, fibrous tissue, high energy and protein content that can be used for a variety of useful applications such as wastewater treatment, compost and fertilizer, animal feed (Abhed, 2020). On the one hand, *Eichhornia crassipes* is a source of organic matter that can be transformed into compost to improve soil quality and plant productivity (Sofyan et al. 2023). Compost has also been shown to suppress plant diseases and pests and improve agricultural crop yields (Sahana et al. 2018).

On the other hand, *Prosopis juliflora* is an invasive species in the arid and semi-arid zones of Lake Chad. This complex plant has become a major factor in eliminating the habitat of many native species to a catastrophic level. As experts report, *Prosopis juliflora* is included in the new IUCN (2020) list of the 100 worst invasive alien species in the world (Mwangi and Swallow, 2005). From experiences around the world, it appears that it is almost impossible to stop the growth of this plant, because it spreads widely in most arid and semi-arid areas of the world (Kazmi et al., 2010). Prosopis Juliflora stands are so common in the Lake Chad area that they have become the most common and intense plant in this area of northern Cameroon, compared to all plant species..
Women in the Lake Chad area and northern Cameroon carry out essentially agricultural subsistence activities, based on food crops (sorghum, millet, corn, rice, cowpea and fonio) with average yields between [0.85-5] ton.ha-1 (Hervé et al., 2016). Their activities are characterized by poor environmental management of agricultural land and the mismatch between the price of inputs and that of food crops. These two factors constitute important elements of continued soil degradation (Ouedraogo and Hien, 2015) and the increase in the cost of living in the Sahelian agricultural environment. The situation is exacerbated by the increase in the magnitude of the effects of the invasion of environments by prolific plants which impact biodiversity (destruction of aquatic resources such as fish, etc.), economic activities (decrease in fishing and obstruction waterways) and social (decrease in availability of drinking water and appearance of new diseases, increase in overpopulation of urban areas and desertion of landlocked villages due to invasive plants and social ills such as banditry, prostitution and others inhuman drift forms). In such a context, the study of the impact of the proliferation of invasive plants on biodiversity and the socio-economic adaptation strategies of women in the Lake Chad area could help in the medium and long term, to be a tool for decision support; hence the objective of this study which is to determine the effect of *Prosopis Juliflora* and *Eichhornia crassipes* on biodiversity and the socio-economic adaptation strategies of women in the Lake Chad area.

## 2. MATERIALS AND METHODS

### 2.1. Study Area

#### 2.2.1. Assessment of available biomass and density

Three data collection campaigns on 06 quadras per locality and in batches of 3 were carried out to evaluate the available biomass and their density. Quadras (1m×1m) were carried out on ten sites of the lake, in order to collect *Eichhornia crassipes* plants using a wooden cube of 01 m3. The integral harvest method following the grid of nested squares (Daget et al., 2010; Daget and Poissonet, 1971) made it possible to harvest all the species present within each plot.

The collection of raw materials is an operation which consists of mowing *Eichhornia crassipes* plants, waste from other invasive plants or any other from the place of their proliferation to a place of final elimination. It begins with the identification of raw materials in proliferation sites.

#### 2.2.2. Taking floristic data on site

The first step consists of distinguishing the large areas of the basin based on the different natures of spatial heterogeneities of the basin: presence of water, density of vegetation, etc. This first zoning is done using in situ visits. for small basins and is supplemented by taking aerial photos for large surface basins (Saulais M. and Bedell,
2009). The floristic inventory based on the Braun-Blanquet dominance abundance coefficients was established with indices varying from 1 to 5. These abundance-dominance indices make it possible to calculate for each species its average coverage (MR) which is the percentage occupied by this species in a given environment:

$$RMi = \frac{Ri}{\text{Total number of Survey Points}}$$

L'indice de présence (Pi) correspond au recouvrement moyen de l'espèce i sur le recouvrement total des individus :

$$Pi = \frac{RMi}{\sum RM}$$

This five-index scale gives the distribution of individuals of a species as follows:

1 = recovery from 1% to 10%, with average recovery = 5%;

2 = recovery from 10% to 25%, with average recovery = 15%; 3 = recovery of 25% to 50%, with average recovery = 37.5%; 4 = coverage of 50% to 75%, with average coverage = 62.5%; 5 = coverage of 75% to 100%, with average coverage = 87.5%.

The Shannon-Weaver index (H') indicates the diversity or specific richness of the environment, it is therefore determined by the following relationship:

$$H' = - \sum Pi \times \ln (Pi)$$

The regularity index or “Evenness index” or evenness of Pielou is:

$$R = \frac{H'}{Hmax}$$

The frequency data for each species were calculated as follows:

$$\text{Frequency of a species} = \left[ \frac{\text{Number of Points where the species is present}}{\text{Total Number of Points}} \right] \times 100$$

Likewise, the Sorensen coefficient which emphasizes the presence of species in two environments is given by the following relationship:

$$CS = \left[ \frac{2a}{(2a + b + c)} \right]$$

With: 0<CS<1; a = number of species common to the two environments A and B; b = number of species present in environment A and absent in environment B; c = number of species present in environment B and absent in environment A.

# 3. The productivity of *Eichhornia crassipes* in Lake Chad

## 3.1. The absolute growth rate (TDA)
The absolute growth rate (TDA), which reflects the increase in the number of individuals and/or the quantity of fresh biomass as a function of time, can be considered from the angle of vegetative and/or sexual reproduction (Oumarou et al., 2008). In this study, the vegetative multiplication which was considered when evaluating the quantitative and demographic growth rate of *Eichhornia crassipes* is taken into account and the evaluation of this rate consisted of experimentally determining the speed of multiplication at from experimental results by applying the relationship described by Radford (1967):

$$TDA = \frac{W1-W2}{t1-t2} \quad (\text{millimeter/day})$$

With: W1 = number of plants (or biomass) at the start of the experiment at time t1
W2 = number of plants (or biomass) at the end of the experiment at time t2

## 3.2. Assessment of multiplication speed

To measure the multiplication speed of *Eichhornia crassipes* (gram/day), 06 quadras/locality were installed, each measuring 01m² of surface materialized by wooden stakes fixed in the mud and surrounded by iron mesh protection. in which five plants of *Eichhornia crassipes* were placed, previously weighed on dates t₁ and t₂ following the method developed by Oumarou et al., (2008), which consists of taking out of the water at regular intervals (every 48 hours ), *Eichhornia crassipes*, which are counted, drained, weighed and returned to the water. The measurements were carried out in the dry season and in the rainy season.

## 3.3. Modeling the potential evolution of *Eichhornia crassipes* in Lake Chad

Modeling the potential evolution of *Eichhornia crassipes* in the Lake Chad area consists of representing the risk of invasion present in the area by the reproduction and growth capacity of the plant and the abiotic and biotic factors that favor its success scalable. Thanks to data obtained from 15 sampling points, its future distribution was determined with a view to providing decision support data for the planning and implementation of control appropriate to the management of *Eichhornia crassipes* which are invasive plants in this area. Firstly, the study area was digitized using the map produced using ArcGis as a mapping base. The calculations were carried out using the geostatistical analysis tool of the ArcGis program. Cross-validation was then carried out by obtaining different graphs and summaries of the measured and predicted values (Moreno and Valdez, 2005). Then another validation was carried out using MapInfo and Net Logo software to build predictive models of the potential distribution of the plant based on the physico-chemical parameters of the water (temperature, pH, conductivity and dissolved oxygen). Final maps were generated using ArcGis programs.
### 3-4. Physico-chemical characterization of water from the *Eichhornia crassipes* sampling site

After the work to quantify the species on site followed by a methodological update, a physicochemical analysis of the water was carried out at 12 points of effluent upstream and downstream of the sites, which could represent a source of contamination in the area of the site. Lake Chad: these are discharge points for wastewater and urban waste and/or Eichhornia crassipes proliferates. The samples were taken in 08 points which differ in the types of waste which were dumped there, their age and the way in which the waste is disposed there. The samples were collected in amber Pyrex borosilicate glass bottles, and stored in the dark and at 4°C before extraction. They were also filtered on 0.45µm cellulose acetate membranes.

### 3-5. Assessment of the wildlife biomass of Lake Chad

The updated BSI and BILC index methods, used as part of this work, were validated and the benthic macrofauna sampling protocol stabilized, in order to obtain the best compromise cost/sampling effort/ecological relevance for a point sampling. It required an additional field campaign (30 sampling points located throughout Grande Terre with 15 unit samples taken per sampling point) (Mary, 2015). All of this work made it possible to define:

* the most suitable mesh size for sampling benthic macrofauna (500 µm);

* the optimal number of samples to be taken per sampling point (7);

* the order of priority for sampling substrates at a sampling point (table 1);

* the most efficient sampling protocol (paragraph 2/8);

* sensitivity scores, between 1 and 10, for each known taxon of benthic macrofauna in current environments;

* the boundaries of biological quality classes (very good, good, fair, poor, poor) using graphical and statistical methods.

The biotic index is calculated by considering the total number of taxa listed, according to the following formula:

$$BILC \text{ or IBS} = \frac{1}{n} \sum_{i=1}^{I=n} S_i$$

With n: number of indicator taxa and if: score of taxon i for the calculated index

### 3.6. Data analysis

The raw data are collected from each questionnaire, entered and formatted with Microsoft Office Excel software and imported in the form of text files (separator: tabulation) into R and SPSS software for subsequent statistical analyses, namely:
analysis descriptive and the correlation test. The descriptive analysis consisted of calculations of proportions (percentages), means and standard deviations. Graphs and tables were constructed. The sperman correlation test made it possible to create a typology of the farms surveyed on the basis of the types of disturbance perceived. Given that the study sample was made up equally of men and women, only the variables "age" and "level of education" linked to workers were retained for this typology:

- The "age" variable has three modalities: the "Young" (YOUN) modality for workers whose age is < 45 years, the "Aged" (AG) modality for workers whose age is between 45 and 60 years old and the "Very elderly" (VE) modality for workers whose age is > 60 years old;

- The "level of education" variable has three categories: "workers without a formal level of education" (FLE), workers who have reached the primary level of formal education (PRIM) and workers who have reached the secondary level (SL) and more.

# 4. RESULTS AND DISCUSSION

## 4.1. Assessment of available invasive biomass and density

Three data collection campaigns of 30 samples over 06 quadras per locality and in batches of 3 were carried out for the evaluation of the available biomass and their density. Quadras (1m×1m) were carried out on ten sites of the lake, in order to collect Eichhornia crassipes plants using a wooden cube of 01 m³. The integral harvest method following the grid of nested squares (Daget and Poissonet, 1971; Daget et al., 2010) made it possible to harvest all the species present within each plot. The data collected is distributed as follows:

<table><caption>Table 1: Density of *Eichhornia crassipes* samples collected by batch between August-September 2022</caption><thead><tr><th>Sites</th><th>Number Quadras (1m×1m)</th><th>Number of plant species present (Plants/m²)</th><th>Density of <i>Eichhornia crassipes</i> harvested (Plants/m²)</th><th>Percentage of <i>Eichhornia crassipes</i> harvested/Quadra (%)</th></tr></thead><tbody><tr><td>Makary</td><td>06</td><td>07±0.4</td><td>137±1.1</td><td>95.5</td></tr><tr><td>Blangoua</td><td>06</td><td>17±0.1</td><td>296±2.3</td><td>83.9</td></tr><tr><td>Fotokol</td><td>06</td><td>08±0.1</td><td>151±0.3</td><td>88.1</td></tr><tr><td>Darak</td><td>06</td><td>12±0.3</td><td>152±1.3</td><td>87.2</td></tr><tr><td>Hilé Alifa</td><td>06</td><td>09±0.8</td><td>120±2.3</td><td>80.9</td></tr></tbody></table>

The mix of species present in the territory of Lake Chad and on the water surface in the sites is higher in Blangoua (17±0.1 plant species present/m²) and Darak (12±0.3
plant species present/m²) while in the lowest mix of species present on the water surface are found in Makary (07±0.4 plant species present/m²). The highest density of *Eichhornia crassipes* collected in Blangoua (296±2.3 *Eichhornia crassipes* plants present/m²) while the lowest density of *Eichhornia crassipes* collected is in Hilé Alifa (120±2.3 *Eichhornia crassipes* plants present/m²): this testifies to the vitality of biodiversity in these two wetlands of Lake Chad. However, the percentage of *Eichhornia crassipes* collected in relation to the number of plant species present per quadra is higher in Makary (95.5%) while it is lower in Hilé Alifa (80.9%). Consequently, Makary would be more invaded by *Eichhornia crassipes* than other localities.

**4.2. Biomass of vegetation by city in the Lake Chad area Cameroon**

The Sahelian herbaceous steppe is not devoid of perennials, the most characteristic is *Panicum turgidum*, developing on the coarse sands which it fixes by forming large tufts. Although its culms are hard, it is appreciated by camels and cattle. After the drought its area expanded, and it now occupies vast areas, in Chad in particular.

Other perennials exist in this area, often with low abundance, especially after drought: *Stipagrostis unipulis*, *Aristida pallida*, *Cymbopogon schoenanthus* and *Cyperus jeminicus*.

The herbaceous carpet of annuals, composed mainly of grasses, is very closely dependent on rainfall. The most abundant species are *Tragus berteronianus*, *Enneapogon spp.*, *Cenchrus biflorus*, *Aristida mutabilis*. A species of Saharan affinity, *Molkiopsis ciliata*, is common, while *Gisekia pharnacioides* reflects low and irregular rainfall. Woody plants are very rare, while *Panicum turgidum* forms the perennial layer, accompanied by *Cyperus jeminicus* and *Aristida papposa*, relatively rare.
<table><caption>Table 2: Cross-tabulation of types of shrub layer biomass by city</caption><thead><tr><th>Types of biomass</th><th>Images</th><th>Harvest location</th><th>Makary</th><th>Blangoua</th><th>Darak</th><th>Logone Birni</th><th>Fotokol</th><th>Hilé Alifa</th></tr><tr><td></td><td></td><td colspan="7">Shrub layer per km²</td></tr></thead><tbody><tr><td>Acacia senegal</td><td></td><td>Dry land</td><td>14±2.4</td><td>11±0.3</td><td>7±0.2</td><td>16±0.7</td><td>10±0.4</td><td>10±0.5</td></tr><tr><td>Balanites aegyptiaca</td><td></td><td>Dry land</td><td>12±2.2</td><td>10±3.2</td><td>5±0.8</td><td>13±4.2</td><td>13±2.5</td><td>9±2.1</td></tr><tr><td>Ziziphus mauritiana</td><td></td><td>Dry land</td><td>9±0.1</td><td>10±1.3</td><td>4±0.2</td><td>10±3.1</td><td>11±2.3</td><td>7±1.4</td></tr><tr><td>Cadaba farinosa</td><td></td><td>Dry land</td><td>8±0.3</td><td>3±0.6</td><td>2±0.9</td><td>3±0.5</td><td>6±0.7</td><td>1±0.1</td></tr><tr><td>Capparis decidua</td><td></td><td>Dry land</td><td>3±0.5</td><td>2±0.3</td><td>1±0.2</td><td>1±0.3</td><td>4±1.4</td><td>1±0.2</td></tr></tbody></table>

<figure><img src="image_122.png" /></figure>

<figure><img src="image_123.png" /></figure>

<figure><img src="image_124.png" /></figure>

<figure><img src="image_125.png" /></figure>

<figure><img src="image_126.png" /></figure>
<table><tr><td><strong><em>Salvadora persica</em></strong></td><td><img src="image_0_0.png" alt="Dry land with a tree"></td><td>Dry land</td><td>2±0.8</td><td>2±0.6</td><td>1±0.1</td><td>1±0.2</td><td>2±0.3</td><td>1±0.1</td></tr><tr><td><strong><em>Prosopis juliflora</em></strong></td><td><img src="image_0_1.png" alt="Dry land with a tree"></td><td>Dry land</td><td>8±0.5</td><td>6±0.1</td><td>2±0.3</td><td>8±0.6</td><td>3±0.4</td><td>0</td></tr><tr><td colspan="9" style="text-align: center;"><em>Perennial herbaceous layer per m²</em></td></tr><tr><td><strong><em>Tragus berteronianus</em></strong></td><td><img src="image_0_2.png" alt="Lake with a plant"></td><td>Lake</td><td>9±0.6</td><td>8±0.2</td><td>8±0.3</td><td>9±0.6</td><td>9±0.8</td><td>8±0.4</td></tr><tr><td><strong><em>Enneapogon spp.</em></strong></td><td><img src="image_0_3.png" alt="Lake with a plant"></td><td>Lake</td><td>8±0.1</td><td>7±0.6</td><td>7±0.2</td><td>8±0.3</td><td>8±0.6</td><td>7±0.8</td></tr><tr><td><strong><em>Cenchrus biflorus</em></strong></td><td><img src="image_0_4.png" alt="Lake with a plant"></td><td>Lake</td><td>7±0.9</td><td>7±0.1</td><td>5±0.6</td><td>7±0.2</td><td>7±0.3</td><td>5±0.6</td></tr><tr><td><strong><em>Aristida mutabilis</em></strong></td><td><img src="image_0_5.png" alt="Lake with a plant"></td><td>Lake</td><td>5±0.5</td><td>5±0.9</td><td>3±0.1</td><td>5±0.6</td><td>5±0.2</td><td>3±0.3</td></tr></table>
<table><tr><td><i>Schoenefeldia gracilis</i></td><td></td><td>Lake</td><td>8±0.8</td><td>7±0.4</td><td>7±0.5</td><td>8±0.9</td><td>7±0.1</td><td>7±0.6</td></tr><tr><td><i>Aristida funiculata</i></td><td></td><td>Lake</td><td>7±0.9</td><td>7±0.8</td><td>5±0.4</td><td>7±0.5</td><td>5±0.9</td><td>5±0.1</td></tr><tr><td><i>Chloris pilosa</i></td><td></td><td>Lake</td><td>5±0.3</td><td>5±0.9</td><td>3±0.8</td><td>5±0.4</td><td>2±0.5</td><td>3±0.9</td></tr><tr><td><i>Pennisetum pedicellatum</i></td><td></td><td>Lake</td><td>3±0.1</td><td>2±0.3</td><td>2±0.9</td><td>2±0.8</td><td>1±0.4</td><td>2±0.5</td></tr><tr><td><i>Aristida funiculata</i></td><td></td><td>Lake</td><td>5±0.3</td><td>1±0.1</td><td>5±0.3</td><td>1±0.9</td><td>0</td><td>5±0.4</td></tr><tr><td><i>Echinochloa colona</i></td><td></td><td>Lake</td><td>3±0.2</td><td>0</td><td>3±0.1</td><td>1±0.3</td><td>1±0.9</td><td>3±0.8</td></tr></table>

<figure><img src="image_127.png" /></figure>

<figure><img src="image_128.png" /></figure>

<figure><img src="image_129.png" /></figure>

<figure><img src="image_130.png" /></figure>

<figure><img src="image_131.png" /></figure>

<figure><img src="image_132.png" /></figure>
<table><tr><td><i>Panicum laetum</i></td><td></td><td>Lake</td><td>8±0.2</td><td>5±0.2</td><td>8±0.3</td><td>1±0.1</td><td>5±0.3</td><td>8±0.9</td></tr><tr><td><i>Mitragyna inermis</i></td><td></td><td>Lake</td><td>1±0.6</td><td>3±0.1</td><td>5±0.2</td><td>5±0.3</td><td>3±0.1</td><td>1±0.3</td></tr><tr><td><i>Cymbopogon proximus</i></td><td></td><td>Lake</td><td>5±0.4</td><td>8±0.6</td><td>3±0.1</td><td>3±0.2</td><td>2±0.3</td><td>5±0.1</td></tr><tr><td><i>Aristida pallens</i></td><td></td><td>Lake</td><td>8±0.9</td><td>3±0.2</td><td>5±0.4</td><td>5±0.6</td><td>3±0.1</td><td>8±0.2</td></tr><tr><td><i>Eichhornia Crassipes</i></td><td></td><td>Lake</td><td>169±13.1</td><td>168±42.1</td><td>163±10.3</td><td>167±31.3</td><td>162±20.9</td><td>165±16.9</td></tr></table>

<figure><img src="image_133.png" /></figure>

<figure><img src="image_134.png" /></figure>

<figure><img src="image_135.png" /></figure>

<figure><img src="image_136.png" /></figure>

<figure><img src="image_137.png" /></figure>
<table><tr><td><i>Panicum turgidum</i></td><td></td><td>Lake</td><td>3±0.5</td><td>5±0.1</td><td>8±0.1</td><td>8±0.3</td><td>5±0.1</td><td>3±0.9</td></tr><tr><td><i>Cyperus jeminicus</i></td><td></td><td>Lake</td><td>8±0.1</td><td>3±0.5</td><td>3±0.1</td><td>6±0.1</td><td>3±0.3</td><td>8±0.1</td></tr><tr><td><i>Eragrostis tremula</i></td><td></td><td>Lake</td><td>7±0.2</td><td>8±0.1</td><td>2±0.5</td><td>8±0.1</td><td>2±0.1</td><td>3±0.3</td></tr></table>

<figure><img src="image_138.png" /></figure>

<figure><img src="image_139.png" /></figure>
## 4.3 Abundance-dominance indices of *Eichhornia crassipes* on site

Floristic data collection of *Eichhornia crassipes* and *Prosopis juliflora* respectively in plots of 01 m² by 20m² (for *Eichhornia Crassipes*) and plots of 01 Km² by 20Km² (for *Prosopis juliflora*) carried out in each of the 06 sites (Makary: Point 1, 2, 3, 4, 5, 6, 7, 8 and 9, Blangoua: Point 10,11, 12, Darack: Point 13 and 14 (Fig. 1); Hilé Alifa: Point 15, 16 and , Logone Birni; : Point 17, 18 and 19; Point 20, 21, 22, 23, 24 and 25, a total of 25 data collection points.

From 2022-2023, the five-index scale gives the distribution of *Eichhornia Crassipes* individuals in the Lake Chad area as follows:

<table><caption>Table 3: Estimation of the spatial heterogeneity of *Eichhornia Crassipes* and *Prosopis juliflora* in the water territories of Lake Chad Cameroon</caption><thead><tr><th rowspan="2">Study sites</th><th colspan="2">Number of relief points</th><th colspan="2">Number (Ri)</th><th colspan="2">Average coverage (RM) %</th><th colspan="2">Abundance-dominance indices</th></tr><tr><th><i>Eichhornia Crassipes</i></th><th><i>Prosopis juliflora</i></th><th><i>Eichhornia Crassipes</i></th><th><i>Prosopis juliflora</i></th><th><i>Eichhornia Crassipes</i></th><th><i>Prosopis juliflora</i></th><th><i>Eichhornia Crassipes</i></th><th><i>Prosopis juliflora</i></th></tr></thead><tbody><tr><td>Makary</td><td>9</td><td>9</td><td>169.2±14.83</td><td>29.8±4.8</td><td>18.78</td><td>71.88</td><td>2</td><td>5</td></tr><tr><td>Blangoua</td><td>3</td><td>7</td><td>168.7±15.78</td><td>49.4±1.4</td><td>56</td><td>66.96</td><td>4</td><td>5</td></tr><tr><td>Fotokol</td><td>6</td><td>8</td><td>162.5±20.28</td><td>25.3±3.5</td><td>27</td><td>77.64</td><td>3</td><td>5</td></tr><tr><td>Darak</td><td>2</td><td>7</td><td>163.3±31.52</td><td>47.1±4.3</td><td>81.5</td><td>84.15</td><td>5</td><td>5</td></tr><tr><td>Hilé Alifa</td><td>2</td><td>2</td><td>165.2±34.55</td><td>56.7±2.4</td><td>82.5</td><td>59.5</td><td>5</td><td>4</td></tr><tr><td>Logone Birni</td><td>3</td><td>3</td><td>167.4±32.66</td><td>62.9±4.7</td><td>55.67</td><td>65.75</td><td>4</td><td>4</td></tr><tr><td>Average</td><td>4.17±2.78</td><td>4.17±2.78</td><td>166.05±32.81</td><td>45.20±14.83</td><td>53.57±26.62</td><td>70.98±8.87</td><td>3.83±1.16</td><td>4.67±0.51</td></tr></tbody></table>

On an average of 4,167±2,786 sampling points, an average of 165,667±2,804 *Eichhornia crassipes* plants was observed, with an average abundance-dominance index of 3.833±1.169 and an average recovery rate (MR) of all the area of Lake Chad Cameroon which is 53.575±26.621%.

## 4.4. Presence of *Eichhornia crassipes* in the sampling sites

The diversity or specific richness of each environment in *Eichhornia crassipes*, which takes into account both richness and fairness, was determined using the Shannon-Weaver index, including the general average for Lake Chad Cameroon is 2.113±0.766 whose presence index is 0.207±0.095: the greatest diversity was observed in Hilé Alifa (0.256) while the lowest diversity is that observed in Makary (0.058).
<table><caption>Table 4: Quantification of species present on the sites</caption><thead><tr><th>Sites</th><th>Presence index of <i>Eichhornia crassipes</i> (Pi)</th><th>Shannon-Weaver index (H')</th><th>Regularity index (R)</th><th>Frequency of <i>Eichhornia crassipes</i> (%)</th></tr></thead><tbody><tr><td>Makary</td><td>0.058</td><td>3.531</td><td>1</td><td>36</td></tr><tr><td>Blangoua</td><td>0.333</td><td>1.363</td><td>0.386</td><td>12</td></tr><tr><td>Fotokol</td><td>0.167</td><td>2.219</td><td>0.628</td><td>24</td></tr><tr><td>Darak</td><td>0.253</td><td>1.704</td><td>0.482</td><td>08</td></tr><tr><td>Hilé Alifa</td><td>0.256</td><td>1.689</td><td>0.478</td><td>08</td></tr><tr><td>Logone Birni</td><td>0.173</td><td>2.175</td><td>0.616</td><td>12</td></tr><tr><td>Average</td><td>0.207±0.095</td><td>2.113±0.766</td><td>0.598±0.217</td><td>16.7±0.11</td></tr></tbody></table>

However, the average regularity on the waters of Lake Chad is 0.598±0.217, higher in Makary (1.000) and lower in Blangoua (0.386). The average frequency of *Eichhornia crassipes* in the waters of Lake Chad Cameroon is 16.7±0.11%: the highest is that of Makary (36%), while those observed in Darak (08) and Hilé Alifa (08) are weak.

Three collection campaigns of 30 samples were carried out in batches of 3. The data collected was distributed as follow:

<table><caption>Table 5: Density of *Eichhornia crassipes* samples collected by batch between August-September 2022</caption><thead><tr><th>Sites</th><th>Quadras (1m×1m)</th><th>Number of plant species present (Plants/m²)</th><th>Density of Eichhornia crassipes harvested (Plants/m²)</th><th>Percentage of Eichhornia crassipes harvested / Quadra (%)</th></tr></thead><tbody><tr><td>Makary</td><td>06</td><td>07±0.4</td><td>137±1.1</td><td>95.5</td></tr><tr><td>Blangoua</td><td>06</td><td>17±0.1</td><td>296±2.3</td><td>83.9</td></tr><tr><td>Fotokol</td><td>06</td><td>08±0.1</td><td>151±0.3</td><td>88.1</td></tr><tr><td>Darak</td><td>06</td><td>12±0.3</td><td>152±1.3</td><td>87.2</td></tr><tr><td>Hilé Alifa</td><td>06</td><td>09±0.8</td><td>120±2.3</td><td>80.9</td></tr></tbody></table>

The mix of species present on the water surface in the sites is higher in Blangoua (17±0.1 species of plants present/m²) and Darak (12±0.3 species of plants present/m²) while in the lowest mix of species present on the water surface are found in Makary (07±0.4 plant species present/m²). The highest density of *Eichhornia crassipes* collected in Blangoua (296±2.3 *Eichhornia crassipes* plants present/m²) while the lowest density of *Eichhornia crassipes* collected is in Hilé Alifa (120±2.3 plants *Eichhornia crassipes* present/m²): this testifies to the vitality of biodiversity in these two wetlands of Lake Chad. However, the percentage of *Eichhornia crassipes* harvested in relation to the number of plant species present by Quadra is higher in Makary (95.5%) while it is lower in Hilé Alifa (80.9%). Consequently, Makary would be more invaded by *Eichhornia crassipes* than other localities.

## 4.5. Physico-chemical characterization of water from the *Eichhornia crassipes* sampling site in the Lake Chad area Cameroon
The analysis of the water parameters of the sampling points was carried out on 12 points in six sites.

The Fotokol, Makary, Hilé Alifa, Darak and Logone Birni site received numerous biodegradable household pollutants such as household waste, sanitary and fecal waste, agricultural waste, etc., and the Blangoua site received non-household pollutants and non-biodegradable such as chemical and pesticide residues, petroleum products, etc. The following table illustrates the physicochemical parameters of each parameter studied.

The Fotokol site has a SS 3 to 4 times higher than that of the waters of the other sites over 24 hours. The presence of certain pollutants such as NH<sub>4</sub><sup>+</sup>, NO<sub>3</sub><sup>-</sup>, N.T.K. and Phosphate gives an idea of the level of pollution by nitrogen pollutants.

Overall, unpolluted sites have an average SS of 22.04±9.45 mg/l, sites polluted by organic matter have an average SS of 24.07±8.22 mg/l while sites polluted by non-organic matter have a TSS of 23.43±1.41 mg/l.

Sites polluted by organic matter have an average COD, higher of the order of 34.63±15.18 mg/l while the unpolluted sites have an average COD of 32.18±16.19 mg/l, the sites polluted by non-organic matter have a COD of 32.56±12.02 mg/l.
<table><caption>Table 6: Physico-chemical parameters of effluents at the sites (sample collection points)</caption><thead><tr><th rowspan="2">Collection sites for <i>Eichhornia crassipes</i> samples</th><th rowspan="2">Type of site</th><th rowspan="2">Period and dates of collection</th><th colspan="2">Suspended matter (mg/l)</th><th colspan="2">Chemic Organic Demand (COD) (mg/l)</th><th colspan="2">Biologic Organic Demand in 5 days (BOD<sub>5</sub>)(mg/l)</th><th colspan="2">NH<sub>4</sub><sup>+</sup> (mg/l)</th><th colspan="2">NTK (mg/l)</th><th colspan="2">NO<sub>3</sub><sup>-</sup> (mg/l)</th><th colspan="2">P total (mg/l)</th><th colspan="2">Ph</th></tr><tr><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</th><th>Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</th></tr></thead><tbody><tr><td>Makary</td><td>US</td><td>23/08/2022</td><td>8.4</td><td>8,1</td><td>16</td><td>14</td><td>5.6</td><td>5</td><td>0.99</td><td>0.79</td><td>3.76</td><td>3.15</td><td>2.72</td><td>2.32</td><td>0.78</td><td>0.21</td><td>7.6</td><td>7.1</td></tr><tr><td>Makary</td><td>OM</td><td>01/12/2022</td><td>28.8</td><td>28.4</td><td>57</td><td>55</td><td>5.3</td><td>5</td><td>34.87</td><td>34.31</td><td>37.77</td><td>37.31</td><td>0.48</td><td>0.28</td><td>0.46</td><td>0.26</td><td>7.4</td><td>7.6</td></tr><tr><td>Blangoua</td><td>NOM</td><td>10/08/2022</td><td>26.8</td><td>26.2</td><td>54</td><td>53</td><td>5.5</td><td>5.3</td><td>9.54</td><td>9.23</td><td>31.71</td><td>31.11</td><td>1.67</td><td>1.17</td><td>0.65</td><td>0.31</td><td>7.7</td><td>7.3</td></tr><tr><td>Blangoua</td><td>NOM</td><td>20/01/2023</td><td>28.6</td><td>28.2</td><td>34</td><td>36</td><td>4.6</td><td>4</td><td>8.73</td><td>8.21</td><td>32.61</td><td>32.01</td><td>1.8</td><td>1.19</td><td>0.66</td><td>0.28</td><td>7.2</td><td>7.4</td></tr><tr><td>Fotokol</td><td>OM</td><td>02/08/2022</td><td>28.4</td><td>28.9</td><td>35</td><td>39</td><td>5.3</td><td>5</td><td>33.87</td><td>33.29</td><td>38.65</td><td>38.91</td><td>0.75</td><td>0.29</td><td>0.74</td><td>0.37</td><td>7.6</td><td>7.2</td></tr><tr><td>Fotokol</td><td>OM</td><td>03/02/2023</td><td>27.8</td><td>28.8</td><td>42.8</td><td>42</td><td>7.2</td><td>7</td><td>32.66</td><td>32.21</td><td>38.66</td><td>38.72</td><td>1.69</td><td>1.09</td><td>0.48</td><td>0.34</td><td>7.8</td><td>7.2</td></tr><tr><td>Darak</td><td>US</td><td>09/08/2022</td><td>9.6</td><td>9.9</td><td>17</td><td>13</td><td>4.6</td><td>4</td><td>0.76</td><td>0.83</td><td>2.96</td><td>2.91</td><td>3.28</td><td>3.21</td><td>0.78</td><td>0.38</td><td>7.1</td><td>7.1</td></tr><tr><td>Darak</td><td>OM</td><td>05/01/2023</td><td>27.5</td><td>26.5</td><td>39.5</td><td>39</td><td>6.5</td><td>6</td><td>34.86</td><td>34.09</td><td>39.57</td><td>39.01</td><td>0.77</td><td>0.73</td><td>0.86</td><td>0.36</td><td>7.6</td><td>7.3</td></tr><tr><td>Hilé Alifa</td><td>US</td><td>13/08/2022</td><td>9.3</td><td>8.6</td><td>13.4</td><td>11</td><td>4.3</td><td>4</td><td>0.77</td><td>0.89</td><td>1.55</td><td>1.98</td><td>3.69</td><td>3.39</td><td>0.44</td><td>0.27</td><td>7.5</td><td>7.1</td></tr><tr><td>Hilé Alifa</td><td>OM</td><td>12/01/2023</td><td>28.5</td><td>28.2</td><td>38.3</td><td>37</td><td>7.6</td><td>7</td><td>31.86</td><td>31.23</td><td>37.76</td><td>37.87</td><td>0.99</td><td>0.92</td><td>0.65</td><td>0.29</td><td>7.3</td><td>7.5</td></tr><tr><td>Logone Birni</td><td>US</td><td>19/08/2022</td><td>8.7</td><td>8.5</td><td>17.4</td><td>15</td><td>3.5</td><td>3</td><td>0.99</td><td>0.93</td><td>2.99</td><td>2.82</td><td>3.98</td><td>3.58</td><td>0.37</td><td>0.31</td><td>7.8</td><td>7.2</td></tr><tr><td>Logone Birni</td><td>OM</td><td>04/02/2023</td><td>28.9</td><td>28.4</td><td>43</td><td>41</td><td>8.3</td><td>8</td><td>35.65</td><td>35.04</td><td>38.89</td><td>38.81</td><td>0.73</td><td>0.96</td><td>0.39</td><td>0.33</td><td>7.6</td><td>7.1</td></tr><tr><td>Average US</td><td></td><td></td><td>22.04±9.45</td><td></td><td>32.18±16.19</td><td></td><td>5.02±1.26</td><td></td><td>16.91±15.71</td><td></td><td>24.16±17.20</td><td></td><td>1.65±1.24</td><td></td><td>0.30±0.05</td><td></td><td>7.27±0.16</td><td></td></tr><tr><td>Average OM</td><td></td><td></td><td>24.07±8.22</td><td></td><td>34.63±15.18</td><td></td><td>5.3±1.55</td><td></td><td>20.02±15.59</td><td></td><td>27.40±16.18</td><td></td><td>1.52±1.23</td><td></td><td>0.31±0.04</td><td></td><td>7.27±0.16</td><td></td></tr><tr><td>Average NOM</td><td></td><td></td><td>23.43±1.41</td><td></td><td>32.56±12.02</td><td></td><td>5.30±0.91</td><td></td><td>18.44±0.72</td><td></td><td>26.21±0.63</td><td></td><td>1.65±0.01</td><td></td><td>0.32±0.02</td><td></td><td>7.24±0.07</td><td></td></tr></tbody></table>

With US=Unpolluted Site; OM=Site Polluted with Organic Matter; NOM= Site Polluted with Non-Organic Matter
## 4.6. Characterization of *Eichhornia crassipes* samples

To analyze the water, lipid, protein and ash contents, sampling was carried out on the leaves, stems and roots of *Eichhornia crassipes* collected from six sites. The samples analyzed are very rich in water (nearly 90%). Their average energy value is of the order of 314.454±25.367 kcal/100 g of dry leaves of *Eichhornia crassipes* and 306.273±35.271 kcal/100 g of dry roots of *Eichhornia crassipes*.

However, they only contain traces of lipids. The protein content varies between 223.281% dry matter and 262.681% dry matter with an average of 239.386±13.159% dry matter in the leaves and 242.418±13.001% dry matter in the roots. The carbohydrate contents are high (varying from 28 to 71 g per 100 g). The ash contents, which reflect those of the mineral elements, at the level of the roots vary slightly, i.e. 33 g/100 g in Fotokol and 48 g/100 g in Makary, while at the level of the leaves, they vary slightly, i.e. 32 g/100 g. in Fotokol and 43g/100g in Makary. All these values vary significantly on the one hand between the roots and the leaves (P < 0.05), on the other hand between the different sites (P < 0.05). The following table illustrates the physicochemical parameters of each sample studied.

<table><caption>Table 7: Chemical characterization of *Eichhornia crassipes* in the Lake Chad area
Cameroon</caption><thead><tr><th>Collection sites for <br><i>Eichhornia crassipes</i> samples</th><th></th><th>Carbohydrate content (g/100g)</th><th>Nitrogen percentage (%)</th><th>Protein content (%ms)</th><th>Lipid content (% g/100g MF)</th><th>Ash content (g/100g)</th><th>Metabolic energy (EM in kcal/100 g of <i>Eichhornia crassipes</i>)</th></tr></thead><tbody><tr><td rowspan="2">Makary</td><td>Leaves</td><td>71</td><td>36.021</td><td>225.131</td><td>0.002</td><td>43</td><td>322</td></tr><tr><td>Roots</td><td>28</td><td>37.003</td><td>226.002</td><td>0.001</td><td>48</td><td>305</td></tr><tr><td rowspan="2">Blangoua</td><td>Leaves</td><td>69</td><td>38.291</td><td>239.318</td><td>0.001</td><td>36</td><td>288</td></tr><tr><td>Roots</td><td>35</td><td>36.390</td><td>223.281</td><td>0.001</td><td>34</td><td>309</td></tr><tr><td rowspan="2">Fotokol</td><td>Leaves</td><td>68</td><td>42.029</td><td>262.681</td><td>0.001</td><td>32</td><td>348</td></tr><tr><td>Roots</td><td>31</td><td>43.102</td><td>252.311</td><td>0.001</td><td>33</td><td>332</td></tr><tr><td rowspan="2">Darak</td><td>Leaves</td><td>70</td><td>38.054</td><td>237.837</td><td>0.001</td><td>41</td><td>342</td></tr><tr><td>Roots</td><td>30</td><td>39.201</td><td>234.131</td><td>0.001</td><td>43</td><td>331</td></tr><tr><td rowspan="2">Hilé Alifa</td><td>Leaves</td><td>67</td><td>39.028</td><td>243.925</td><td>0.001</td><td>38</td><td>311</td></tr><tr><td>Roots</td><td>29</td><td>38.711</td><td>245.131</td><td>0.001</td><td>39</td><td>312</td></tr><tr><td rowspan="2">Logone Birni</td><td>Leaves</td><td>69</td><td>41.029</td><td>256.431</td><td>0.001</td><td>40</td><td>259</td></tr><tr><td>Roots</td><td>30</td><td>42.201</td><td>255.443</td><td>0.002</td><td>41</td><td>232</td></tr><tr><td>Average in leaves</td><td></td><td>49.75±20.15</td><td>38.575±1.905</td><td>239.386±13.159</td><td>0.0011±0.0003</td><td>38.818±4.875</td><td>314.454±25.367</td></tr><tr><td>Average in roots</td><td></td><td>49.75±19.98</td><td>39.194±1.986</td><td>242.418±13.001</td><td>0.0011±0.0003</td><td>38.636±4.738</td><td>306.273±35.271</td></tr></tbody></table>

## 4.7. The productivity of *Eichhornia crassipes* in Lake Chad

### 4.7.1. The absolute growth rate (AGR)
In this study, data were collected on samples during 90 days of the dry season (from October 1 to December 30) and 90 days of the rainy season (from June 1 to August 30). Vegetative propagation was evaluated by determining the quantitative and demographic growth rate of *Eichhornia crassipes*, taking into account the environments in which the *Eichhornia crassipes* samples grew. The parameters of the growth media that were taken into account for the evaluation of this rate are:

<table><caption>Table 8: Physico-chemical parameters of growth waters of *Eichhornia crassipes* samples</caption><thead><tr><th rowspan="2"></th><th colspan="2">Makary</th><th colspan="2">Blangoua</th><th colspan="2">Fotokol</th><th colspan="2">Darak</th><th colspan="2">Hilé Alifa</th></tr><tr><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th></tr></thead><tbody><tr><td>Samples</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td></tr><tr><td>pH</td><td>7.50±0.23</td><td>8.75±0.13</td><td>7.80±0.32</td><td>8.41±0.47</td><td>8.01±0.74</td><td>8.11±0.32</td><td>7.02±0.11</td><td>8.58±0.01</td><td>7.12±0.11</td><td>8.15±0.7</td></tr><tr><td>Conductivity (µS/cm)</td><td>164±0.32</td><td>143±0.41</td><td>165±0.12</td><td>153±0.65</td><td>165±0.82</td><td>169±0.74</td><td>161±0.64</td><td>156±0.83</td><td>163±0.23</td><td>163±0.63</td></tr><tr><td>Dissolved oxygen (mg/l)</td><td>6.5±0.12</td><td>6.9±0.74</td><td>6.3±0.36</td><td>6.1±0.83</td><td>6.3±0.23</td><td>7.3±0.41</td><td>5.1±0.11</td><td>5.4±0.47</td><td>6.2±0.11</td><td>6.6±0.2</td></tr><tr><td>Temperature (°C) (day/night)</td><td>37/28</td><td>31/22</td><td>36/29</td><td>35/23</td><td>36/26</td><td>32/21</td><td>40/32</td><td>34/25</td><td>36/24</td><td>33/20</td></tr><tr><td>Turbidité (UNT)</td><td>6</td><td>7</td><td>5</td><td>5</td><td>8</td><td>6</td><td>5</td><td>5</td><td>6</td><td>7</td></tr></tbody></table>

The competitive success of *Eichhornia crassipes* also seems linked to levels of eutrophication and the area occupied by the rest of the vegetation present in the habitat (Morris et al., 1999). One of the determining factors for the growth of *Eichhornia crassipes* is the pH which must be between 6 and 8 (Téllez et al., 2008).

From the data obtained, it appears that the waters of Lake Chad which cross the Fotokol area have a higher pH (8.06±0.56) with average conductivities of the order of 167± 0.78 µS/cm and of dissolved oxygen 6.8± 0.32 mg/l, while the waters of the lake which cross the Darak area have a lower pH (7.80±0.06) with average conductivities of around of 158.5± 0.73 µS/cm and dissolved oxygen 5.8± 0.29 mg/l. These results are close to those of Téllez et al. (2008) who obtained maximum growth of *Eichhornia crassipes* in the waters of the Guadiana River with a pH between 7.25 and 8.1. The optimal average temperature for plant growth is between 25°C and 27°C (Arthaud, 2015). In the study area, the optimal average day/night water temperature during the study is 34.5/36°C to 40/25°C, and the relative humidity is 15/40% to 75/95%. The temperatures of *Eichhornia crassipes* growth media vary between 31/22°C and 40/32°C.

Measurements taken during the dry and rainy season show an absolute population growth rate of 0.091/plant/day, so it takes approximately ten days for one plant of *Eichhornia crassipes* to give rise to another plant. This contrasts with the results obtained by Oumarou et al. (2008) which indicates that the absolute population
growth rate of water hyacinth is 0.083/plant/day and it takes approximately twelve
days for one plant of hyacinth to give rise to another plant in the Bangr-Wéoogo urban
park.

The increase in phytomass is 0.37 g/DM/day per plant. During the period of the
experiment, *Eichhornia crassipes* did not completely cover the 1m² quadras. By
examining the rate of multiplication during the dry season and the rainy season, we
note that the curves which reflect the demographic and biomass increase (figure 3)
are not regular, they present levels almost every three weeks.
<figure><img src="image_140.png" /></figure>

<figure><img src="image_141.png" /><figcaption>Figure 1: Quantitative evolution and absolute rate of increase in the quantity of fresh biomass of *Eichhornia crassipes* in the dry and rainy season by quadras</figcaption></figure>

The absolute rate of increase in the quantity of fresh biomass of *Eichhornia crassipes* as a function of time (Δt =5 days) made it possible to observe the variation in the growth in length of the biomass as the increase of the plants was carried out during a variation
of constant time, over a total duration of 25 days. During this period, all other environmental parameters were met such as:

<table><caption>Table 9: Absolute rate of increase (ARI) in the quantity of fresh biomass of Eichhornia crassipes as a function of time</caption><thead><tr><th rowspan="2"></th><th colspan="2">5 days</th><th colspan="2">10 days</th><th colspan="2">15 days</th><th colspan="2">20 days</th><th colspan="2">25 days</th></tr><tr><th>Δw<sub>1</sub><br>(mm)</th><th>ARI<br>(mm/day)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARI<br>(mm/day)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARI<br>(mm/day)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARI<br>(mm/day)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARI<br>(mm/day)</th></tr></thead><tbody><tr><td>Eichhornia crassipes in Makary</td><td>1.9</td><td>0.38</td><td>2.8</td><td>0.56</td><td>3.3</td><td>0.66</td><td>4.1</td><td>0.82</td><td>4.4</td><td>0.84</td></tr><tr><td>Eichhornia crassipes in Blangoua</td><td>1.8</td><td>0.36</td><td>2.7</td><td>0.54</td><td>3.6</td><td>0.72</td><td>4.3</td><td>0.86</td><td>4.5</td><td>0.9</td></tr><tr><td>Eichhornia crassipes in Fotokol</td><td>1.9</td><td>0.38</td><td>2.8</td><td>0.56</td><td>3.7</td><td>0.74</td><td>4.4</td><td>0.88</td><td>4.7</td><td>0.94</td></tr><tr><td>Eichhornia crassipes in Darak</td><td>1.7</td><td>0.34</td><td>2.9</td><td>0.58</td><td>3.4</td><td>0.68</td><td>4.8</td><td>0.96</td><td>4.9</td><td>0.98</td></tr><tr><td>Eichhornia crassipes àin Hilé Alifa</td><td>1.7</td><td>0.34</td><td>2.8</td><td>0.56</td><td>3.6</td><td>0.72</td><td>4.2</td><td>0.84</td><td>4.4</td><td>0.84</td></tr><tr><td>Average</td><td>1.8±<br>0.1</td><td>0.36±0<br>.02</td><td>2.8±0<br>.07</td><td>0.56±0<br>.01</td><td>3.52±0<br>.16</td><td>0.70±0<br>.03</td><td>4.36±0<br>.27</td><td>0.87±0<br>.05</td><td>4.58±0<br>.22</td><td>0.9±0<br>.06</td></tr><tr><td>Percentage increase (%)</td><td colspan="2">5.5</td><td colspan="2">5.3</td><td colspan="2">4.9</td><td colspan="2">4.7</td><td colspan="2">4.1</td></tr></tbody></table>

The relative growth rates, at a time interval of 05 days, vary between 4.1 and 5.5%. These results are close to those of the work of Gopal (1987) which indicates a relative daily growth rate which varied between 4% and 6%, at doubling times of between 10 and 60 days, depending on the experimental conditions.

### 4.8. Assessment of multiplication speed

In this study, the evaluation of the vegetative multiplication speed was evaluated by determining the quantitative and demographic values of *Eichhornia crassipes* taking into account the parameters of the water sampling media in which these samples of *Eichhornia crassipes* was growing. The parameters of the growth media that were taken into account for the evaluation of this multiplication speed are:

<table><caption>Table 10: Parameters of the water sample collection locations used to evaluate the rate of multiplication of fresh biomass of Eichhornia crassipes</caption><thead><tr><th rowspan="2">Collection location</th><th colspan="2">Makary</th><th colspan="2">Blangoua</th><th colspan="2">Fotokol</th><th colspan="2">Darak</th><th colspan="2">Hilé Alifa</th></tr><tr><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th></tr></thead><tbody><tr><td>Samples</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td><td>10</td></tr><tr><td>Water clarity (visibility) (cm)</td><td>2.12±0.65</td><td>1.94±0.1</td><td>1.6±0.</td><td>1.83±0.3</td><td>1.93±0</td><td>1.31±0.3</td><td>1.91±0</td><td>1.47±0.8</td><td>1.92±0</td><td>1.62±0.1</td></tr><tr><td>Lake depth (m)</td><td>7.53</td><td>8.13</td><td>6.38</td><td>7.47</td><td>7.71</td><td>7.31</td><td>6.21</td><td>6.85</td><td>5.21</td><td>7.67</td></tr><tr><td>Soil type</td><td colspan="10">ferrugineux tropicaux lessivés</td></tr><tr><td rowspan="3">Sands (mm)</td><td>Coarse</td><td>5-12</td><td>6-10</td><td>7-12</td><td>6-12</td><td>6-12</td><td>7-12</td><td>5-12</td><td>6-12</td><td>7-12</td><td>6-12</td></tr><tr><td>Average</td><td>2-4</td><td>2-3</td><td>2-3</td><td>2-4</td><td>2-4</td><td>2-4</td><td>2-3</td><td>2-4</td><td>2-3</td><td>2-4</td></tr><tr><td>End</td><td>1-2</td><td>1-3</td><td>1-2</td><td>1-3</td><td>1-2</td><td>1-3</td><td>1-2</td><td>1-3</td><td>1-2</td><td>1-3</td></tr><tr><td>Number of wildlife species harvested/liter</td><td>150±0.73</td><td>375±0.23</td><td>128±0.9</td><td>741±0.74</td><td>201±0.9</td><td>711±0.32</td><td>132±0.4</td><td>258±0.61</td><td>132±0.7</td><td>85±0.21</td></tr></tbody></table>

From the data obtained, it appears that the waters of Lake Chad have a low clarity (visibility) of the water (2.12±0.65 cm) in the dry season in Makary with 150±0.73 wildlife species harvested/liter, while the highest Water Clarity (visibility)
(1.31±0.39cm) in rainy season was observed in Fotokol with 711±0.32 wildlife species harvested/liter. Variations in the invasive potential of an exotic aquatic plant reflect its novel habitat preference and propagule availability (Mandryk and Wein, 2006). *Eichhornia crassipes* is a plant that reproduces both vegetatively and sexually, the former being the most important for the rapid expansion and colonization of the plant through the formation of stolons (Téllez et al., 2008).

The evaluation of the biomass density of *Eichhornia crassipes* was made during the period from September 2022 to February 2023 in the dry season and from May 2023 to August 2023 in the rainy season, a period during which the site is mono specifically and completely populated with *Eichhornia crassipes* on the body of water. The average density is 164±0.23 feet of *Eichhornia crassipes* per square meter with an average weight of 0.36±0.14kg of fresh biomass per unit (Graph 2). Passage to the oven reveals a proportion of average dry matter (DM) of 6.16±0.08% and an average water content of 94.67±0.54% (Ganesh et al., 2005) places the water content between 94 and 95%. This high water content makes *Eichhornia crassipes* a biological material of choice for biomethanization, to the extent that the anaerobic environment is obtained by saturation of the reaction medium with water, which is, moreover, a rare commodity in the Sahel.

<figure><img src="image_142.png" /><figcaption>Graph 2: Quantitative evolution of *Eichhornia crassipes* in dry and rainy seasons</figcaption></figure>

The evaluation of the multiplication speed of the fresh biomass of *Eichhornia crassipes*
as a function of time (Δt =5 days) made it possible to observe the variation in the weight of the biomass as the growth of the plants increases was carried out during a constant time variation, over a total duration of 25 day.

<table><caption>Table 11: Evaluation of the multiplication speed of fresh biomass of *Eichhornia crassipes* as a function of time</caption><thead><tr><th rowspan="2"></th><th colspan="2">5 days</th><th colspan="2">10 days</th><th colspan="2">15 days</th><th colspan="2">20 days</th><th colspan="2">25 days</th></tr><tr><th>Δw<sub>1</sub><br>(mm)</th><th>ARG<br>(mm/da<br>y)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARG<br>(mm/da<br>y)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARG<br>(mm/da<br>y)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARG<br>(mm/day)</th><th>Δw<sub>1</sub><br>(mm)</th><th>ARG<br>(mm/da<br>y)</th></tr></thead><tbody><tr><td><em>Eichhornia crassipes</em> in Makary</td><td>0,7</td><td>0,14</td><td>0,8</td><td>0,16</td><td>1,3</td><td>0,26</td><td>1,5</td><td>0,3</td><td>1,7</td><td>0,34</td></tr><tr><td><em>Eichhornia crassipes</em> in Blangoua</td><td>0,5</td><td>0,1</td><td>0,6</td><td>0,12</td><td>1,2</td><td>0,24</td><td>1,7</td><td>0,34</td><td>1,9</td><td>0,38</td></tr><tr><td><em>Eichhornia crassipes</em> in Fotokol</td><td>0,8</td><td>0,16</td><td>1,3</td><td>0,26</td><td>1,6</td><td>0,32</td><td>1,9</td><td>0,38</td><td>2,2</td><td>0,44</td></tr><tr><td><em>Eichhornia crassipes</em> in Darak</td><td>0,5</td><td>0,1</td><td>0,8</td><td>0,16</td><td>1,4</td><td>0,28</td><td>1,8</td><td>0,36</td><td>1,9</td><td>0,38</td></tr><tr><td><em>Eichhornia crassipes</em> in Hilé Alifa</td><td>0,6</td><td>0,12</td><td>0,9</td><td>0,18</td><td>1,3</td><td>0,26</td><td>1,9</td><td>0,38</td><td>2,1</td><td>0,42</td></tr><tr><td>Average</td><td>0,62±0,1<br>3</td><td>0,12±0,0<br>3</td><td>0,88±0,26<br>5</td><td>0,18±0,0<br>5</td><td>1,36±0,1<br>5</td><td>0,27±0,0<br>3</td><td>1,76±0,1<br>7</td><td>0,35±0,03<br>9</td><td>1,96±0,1<br>9</td><td>0,39±0,0<br>4</td></tr></tbody></table>

*Eichhornia crassipes* has an extraordinary growth rate with, in other countries, an increase in biomass of 400 to 700 tons per ha per day, or an increase in water area coverage by a factor of 1.012 to 1,077 per day (Téllez et al., 2008).

<figure><img src="image_143.png" /><figcaption>Graph 3. Quantitative evolution and growth rate of *Eichhornia crassipes* in the dry and cold season</figcaption></figure>

4.8.1. Modeling the potential evolution of *Eichhornia crassipes* in Lake Chad
In Figure 3, the map shows the division of the risk level of the sections of the watershed studied into four categories: sections where the risk of infestation is high, very high, extremely high and maximum. Figure 2 shows the main areas (Ha) and risks

<figure><img src="image_144.png" /><figcaption>Graph 4: Graph of risk levels of sections of the Lake Chad watershed</figcaption></figure>
In the study area, there are therefore no physicochemical conditions that would limit the distribution and persistence of the plant. Indeed, this part of the Lake Chad basin is extraordinarily vulnerable to infestation. The area also showed favorable conditions for the continued growth and expansion of *Eichhornia crassipes* year after year.

<figure><img src="image_145.png" /><figcaption>Figure 1: Map of areas on risks of being recovered by *Eichhornia crassipes* in the lac Tchad Basin in Cameroon.</figcaption></figure>

The different risk levels are never far from habitable zones, the maximum risk level (red) is located in the town of Makary (12°33'45.98 north latitude and 14°26'51.3 east longitude, 1845 km²) and in the area of the mouth of the tributary of the city of Fotokol (12°22'39.74 north latitude and 14°13'30.22 east longitude. 3285 Km²). The high risk areas (pink) correspond to the town of Blangoua (12°44'57" North Latitude and 14°34'49" East Longitude, 2116 Km²) and rivers of the town of Hilé Alifa (12 ° 42' 0" North latitude, 14° 19' 0" east longitude). Other areas of Lake Chad that are either at very high (orange) or extremely high (yellow) risk levels are found in the Hilé Alifa and Fotokol areas respectively. Therefore, it is predictable to expect major infestations in the currently colonized area, both in population size and spatial extent. Its expansion into areas currently free of infestation is also expected. These include the Logone Birni area (lower floodplains, between El Béid and Kousseri) and the Chari reservoir towards Chad. Given the size of the potential distribution area, it would
seem necessary to provide for a significant increase and subsequent maintenance of the level of resources and logistics intended for the prevention and control of *Eichhornia crassipes*.

### 4.8.2. Impact on the animal biomass present by city in waters prey to *Eichhornia crassipes* in the Lake Chad area Cameroon

Lake Chad and the rivers, aquifers and aquatic ecosystems contained in its hydrographic basin are declared international waters. During our surveys in 2010, the sampling points surveyed made it possible to count a total of 124 aquifer species. In 2024, we counted a total of 92 species at the same sampling points surveyed. Since 2010-2024, we note an average overall loss of aquatic biodiversity of 25.21±1.72% in the waters of Lake Chad and a loss of waterways due to invasive plants of 78.80±1.30%.

<table><caption>Table 12: Density of *Eichhornia crassipes* samples collected by batch between August-September 2022</caption><thead><tr><th>Sites</th><th>Number of sampling points</th><th>Number of animal species present /m² in 2010</th><th>Number of animal species present /m² in 2024</th><th>Loss of aquatic biodiversity (%)</th><th>Waterways present in 2010 (%)</th><th>Waterways present in 2024 (%)</th><th>Loss waterways (%)</th></tr></thead><tbody><tr><td>Makary</td><td>7</td><td>22,06±0,71</td><td>13,02±0,27</td><td>40,91±0,51</td><td>100</td><td>21±0,91</td><td>79±0,43</td></tr><tr><td>Blangoua</td><td>7</td><td>31,01±0,02</td><td>26,01±0,65</td><td>03,85±0,11</td><td>100</td><td>22±0,19</td><td>78±0,66</td></tr><tr><td>Fotokol</td><td>7</td><td>26,03±0,01</td><td>16,07±0,32</td><td>38,46±0,13</td><td>100</td><td>20±0,73</td><td>80±0,87</td></tr><tr><td>Darak</td><td>7</td><td>21,02±0,17</td><td>19,01±0,94</td><td>9,52±0,05</td><td>100</td><td>20±0,67</td><td>80±0,53</td></tr><tr><td>Hilé Alifa</td><td>7</td><td>24,08±0,29</td><td>16,01±0,15</td><td>33,33±0,19</td><td>100</td><td>23±0,35</td><td>77±0,74</td></tr><tr><td>Moyenne</td><td></td><td>41,33±3,96</td><td>30,33±4,95</td><td>25,21±1,72</td><td>100</td><td>21,2±1,30</td><td>78,8±1,30</td></tr></tbody></table>

The majority of the profiles of the sampling points are generally in a meandering concavity (figure x) in running water environments of the rivers which flow towards Lake Chad.
<figure><img src="image_146.png" /><figcaption>Figure 2: Concavity mold</figcaption></figure>

The order of priority for sampling the substrates at the sampling points made it possible to obtain the following data (table 13):

<table><caption>Table 13: Identification of substrates (% coverage) and speed classes characterizing them</caption><thead><tr><th rowspan="2">HABITABILITY ORDER</th><th rowspan="2">SUBSTRAT</th><th rowspan="2">% COVERAGE AT THE SAMPLING POINT</th><th rowspan="2">REPRESENTATIVENESS (MARGINAL / DOMINANT)</th><th colspan="4">SPEED (V) IN CM/S</th><th rowspan="2">WATER VISIBILITY/CM</th></tr><tr><th>Cascade V&gt;150</th><th>Fast 150&gt;V&gt;75</th><th>Medium 75&gt;V&gt;25</th><th>Low to none V&lt;25</th></tr></thead><tbody><tr><td>11</td><td>Bryophytes</td><td>1</td><td>M</td><td>II</td><td>I</td><td></td><td></td><td>1</td></tr><tr><td>10</td><td>Branches/trunks</td><td>1</td><td>M</td><td></td><td></td><td></td><td>I</td><td>1</td></tr><tr><td>9</td><td>Stones/pebbles (25 to 250 mm)</td><td>3</td><td>D</td><td></td><td>I</td><td>II</td><td></td><td>3</td></tr><tr><td>8</td><td>Litter (+slime)</td><td>2</td><td>M</td><td></td><td></td><td>II</td><td>I</td><td>2</td></tr><tr><td>7</td><td>Hydrophytes*</td><td>4</td><td></td><td></td><td></td><td></td><td></td><td>4</td></tr><tr><td>6</td><td>Root hair</td><td>2</td><td>M</td><td></td><td></td><td></td><td>I</td><td>1</td></tr><tr><td>5</td><td>Blocks "liftable" by hand (size greater than 250 mm)</td><td>5</td><td>D</td><td>III</td><td>I</td><td>II</td><td></td><td>1</td></tr><tr><td>4</td><td>Gravel (2 to 25 mm)</td><td>10</td><td>D</td><td></td><td></td><td>I</td><td>II</td><td>3</td></tr><tr><td>3</td><td>Sands (&lt; 2 mm)</td><td>48</td><td>M</td><td></td><td></td><td></td><td>I</td><td>2</td></tr><tr><td>2</td><td>Lateritic fines (&lt; 2 mm)</td><td>1</td><td></td><td></td><td></td><td></td><td></td><td>4</td></tr><tr><td>1</td><td>Rocks, slabs (non-movable support)</td><td>15</td><td>D</td><td>I</td><td>II</td><td>IV</td><td>II</td><td>1</td></tr><tr><td>0</td><td>Algae</td><td>8</td><td></td><td></td><td></td><td></td><td></td><td>1</td></tr><tr><td colspan="2">Total</td><td>100</td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

The average water height of the sampling locations is 85±7.07 cm while the current speed is on average low. The substrates which contribute to the survival of invasive
aquatic plants are classified from the most biogenic (bryophytes) to the least biogenic (green algae) with almost no and stable clogging and whose aquatic vegetation is made up of 98% *Eichhornia crassipes*

### 4.8.3. Taxa to consider when studying

The taxonomic richness of Lake Chad was an essential element to consider to explain the index scores. This parameter is usually well correlated with the nature of the habitats when water quality is not limiting (Gay, 2000). The experience of Lake Chad shows that in sampling points where a low number of indicator taxa is collected, the index notes have been contradictory and difficult to interpret.

<table><caption>Table 14: Sampling table</caption><thead><tr><th rowspan="2">Levy</th><th rowspan="2"></th><th rowspan="2">Current speed</th><th rowspan="2">Water height (cm)</th><th colspan="3">Substrate</th><th colspan="2">Aquatic vegetation</th></tr><tr><th>Nature</th><th>Clogging (no / weak / medium / strong)</th><th>Stability (stable/moderately stable, unstable)</th><th>Nature</th><th>Abundance (%)</th></tr></thead><tbody><tr><td rowspan="3">Phase 1 and 3 on marginal sites</td><td>L1</td><td>Fast</td><td>80</td><td>Pontederiaceae</td><td>null</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td>L2</td><td>Weak</td><td>90</td><td>Branchages, Pontederiaceae</td><td>weak</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td>L3</td><td>Fast</td><td>90</td><td>Litter, Pontederiaceae</td><td>weak</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td rowspan="4">Phase 2: 4 on dominant sites</td><td>L4</td><td>Weak</td><td>85</td><td>Rock, Pontederiaceae</td><td>null</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td>L5</td><td>Fast</td><td>80</td><td>Rock, Pontederiaceae</td><td>null</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td>L6</td><td>Weak</td><td>75</td><td>Hand lifting blocks, Pontederiaceae</td><td>weak</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr><tr><td>L7</td><td>Fast</td><td>95</td><td>Stones/pebbles and Pontederiaceae</td><td>null</td><td>stable</td><td>Eichhornia crassipes</td><td>98</td></tr></tbody></table>

### 4.8.4. Determination of biological quality

The biological quality class thresholds for LCBI and BSI are shown in Table 16. They were readjusted by Dzokom (2024). On the other hand, the observation made is that in the heavily disturbed sampling points, the taxonomic richness was low; which is similar to the score obtained by Mary and Archaimbault, (2012).

<table><caption>Table 15: Sensitivity scores of indicator taxa of the Lake Chad Biotic Index (LCBI) and the Biosedimentary Index (BSI).</caption><thead><tr><th>Taxon</th><th>LCBI Score</th><th>BSI Score</th><th>Taxon</th><th>BILC Score</th><th>BSI Score</th></tr></thead><tbody><tr><td><strong>INSECTS</strong></td><td></td><td></td><td><strong>Diptera</strong></td><td></td><td></td></tr><tr><td>Lepidoptera</td><td>6</td><td>4</td><td>Blephariceridae</td><td>10</td><td>8</td></tr><tr><td>Springtails</td><td>2</td><td>4</td><td>Ceratopogoninae</td><td>5</td><td>2</td></tr><tr><td><strong>Ephemeroptera</strong></td><td></td><td></td><td>Forcipomyiinae</td><td>7</td><td>5</td></tr><tr><td>Baetidae</td><td>8</td><td>5</td><td>Chironomini</td><td>5</td><td>3</td></tr><tr><td>Leptophlebiidae</td><td></td><td></td><td>Chironomus</td><td>1</td><td>4</td></tr></tbody></table>
<table><tbody><tr><td>Amoa</td><td>8</td><td>9</td><td>Corynoneura</td><td>5</td><td>6</td></tr><tr><td>Celiphlebia</td><td>6</td><td>7</td><td>Harrisius</td><td>5</td><td>4</td></tr><tr><td>Coula</td><td>10</td><td>10</td><td>Orthocladiinae</td><td>1</td><td>2</td></tr><tr><td>Fasciamirus</td><td>10</td><td>6</td><td>Pseudochironomini</td><td>9</td><td>5</td></tr><tr><td>Kariona</td><td>10</td><td>10</td><td>Tanypodinae</td><td>5</td><td>3</td></tr><tr><td>Kouma</td><td>7</td><td>10</td><td>Tanytarsini</td><td>2</td><td>4</td></tr><tr><td>Lepeagenia</td><td>10</td><td>4</td><td>Cecidomyiidae</td><td>3</td><td>3</td></tr><tr><td>Lepeorus</td><td>6</td><td>7</td><td>Culicidae</td><td>6</td><td>9</td></tr><tr><td>N. genre 4</td><td>7</td><td>9</td><td>Dixidae</td><td>9</td><td>5</td></tr><tr><td>N. genre A</td><td>10</td><td>10</td><td>Dolichopodidae</td><td>3</td><td>5</td></tr><tr><td>N. genre B</td><td>10</td><td>10</td><td>Empididae</td><td>9</td><td>4</td></tr><tr><td>Notachalcus</td><td>7</td><td>8</td><td>Ephydridae</td><td>2</td><td>6</td></tr><tr><td>Oumas</td><td>8</td><td>4</td><td>Limoniidae</td><td>3</td><td>6</td></tr><tr><td>Ounia</td><td>9</td><td>8</td><td>Muscidae</td><td>8</td><td>5</td></tr><tr><td>Papposa</td><td>10</td><td>10</td><td>Psychodidae</td><td>1</td><td>8</td></tr><tr><td>Paraluma</td><td>5</td><td>4</td><td>Rhagionidae</td><td>10</td><td>5</td></tr><tr><td>Peloracantha</td><td>10</td><td>10</td><td>Simuliidae</td><td>2</td><td>5</td></tr><tr><td>Pova</td><td>10</td><td>9</td><td>Stratiomyidae</td><td>2</td><td>4</td></tr><tr><td>Simulacala</td><td>7</td><td>7</td><td>Svrphidae</td><td>3</td><td>3</td></tr><tr><td>Tenagophila</td><td>10</td><td>7</td><td>Tabanidae</td><td>5</td><td>6</td></tr><tr><td>Tindea</td><td>9</td><td>7</td><td>Tanyderidae</td><td>5</td><td>5</td></tr><tr><td><strong>Trichoptera</strong></td><td></td><td></td><td><strong>Coleoptera</strong></td><td></td><td></td></tr><tr><td>Ecomidae</td><td>6</td><td>4</td><td>Cucurlionidae</td><td>9</td><td>7</td></tr><tr><td>Helicophidae</td><td>8</td><td>10</td><td>Dytiscidae</td><td>8</td><td>3</td></tr><tr><td>Helicopsychidae</td><td>6</td><td>9</td><td>Gyrinidae</td><td>5</td><td>5</td></tr><tr><td>Hydrobiosidae</td><td>5</td><td>7</td><td>Hydraenidae</td><td>6</td><td>5</td></tr><tr><td>Hydropsychidae</td><td>5</td><td>5</td><td>Hydrophilidae</td><td>3</td><td>3</td></tr><tr><td>Hydroptilidae</td><td>4</td><td>2</td><td>Noteridae</td><td>5</td><td>5</td></tr><tr><td>Kokiriidae</td><td>10</td><td>9</td><td>Scirtidae / Helodidae</td><td>10</td><td>3</td></tr><tr><td>Gracilipsodes</td><td>6</td><td>8</td><td>Staphylinidae</td><td>3</td><td>3</td></tr><tr><td>Oecetis</td><td>5</td><td>6</td><td>Haliplidae</td><td>5</td><td>5</td></tr><tr><td>Symphitoneuria</td><td>9</td><td>6</td><td><strong>Heteroptera</strong></td><td></td><td></td></tr><tr><td>Triplectides</td><td>5</td><td>7</td><td>Belostomatidae</td><td>5</td><td>5</td></tr><tr><td>a. genr. Leptoceridae</td><td>8</td><td>7</td><td>Corixidae</td><td>5</td><td>5</td></tr><tr><td>Philopotamidae</td><td>7</td><td>7</td><td>Gerridae</td><td>7</td><td>9</td></tr><tr><td>Polycentropodidae</td><td>7</td><td>8</td><td>Hebridae</td><td>5</td><td>5</td></tr><tr><td><strong>Odonatoptera</strong></td><td></td><td></td><td>Hydrometridae</td><td>9</td><td>7</td></tr><tr><td>Aeshnidae</td><td>5</td><td>5</td><td>Leptopodidae</td><td>5</td><td>5</td></tr><tr><td>Coenagrionidae</td><td>4</td><td>5</td><td>Mesoveliidae</td><td>8</td><td>4</td></tr><tr><td>Corduliidae</td><td>7</td><td>10</td><td>Notonectidae</td><td>7</td><td>10</td></tr><tr><td>Isostictidae</td><td>7</td><td>9</td><td>Ochteridae</td><td>5</td><td>5</td></tr><tr><td>Lestidae</td><td>5</td><td>5</td><td>Pleidae</td><td>5</td><td>5</td></tr><tr><td>Libellulidae</td><td>3</td><td>4</td><td>Saldidae</td><td>5</td><td>5</td></tr><tr><td>Argiolestidae*</td><td>7</td><td>8</td><td>Veliidae</td><td>5</td><td>9</td></tr><tr><td>Synthemistidae</td><td>5</td><td>8</td><td>Planipennes</td><td>5</td><td>5</td></tr><tr><td><strong>Cnidarians (Hydras)</strong></td><td>3</td><td>3</td><td><strong>GASTEROPOD MOLLUSKS</strong></td><td></td><td></td></tr><tr><td>Platyhelminths</td><td>3</td><td>9</td><td>Gyraulus</td><td>6</td><td>10</td></tr><tr><td>Buy</td><td>1</td><td>10</td><td>Physastra</td><td>2</td><td>10</td></tr><tr><td>Nematodes</td><td>2</td><td>30</td><td>Physa</td><td>2</td><td>3</td></tr><tr><td>Nemertians</td><td>6</td><td></td><td>Pseudosuccinea</td><td>8</td><td>3</td></tr><tr><td>Oligochaetes</td><td>1</td><td>7</td><td>Melanoides</td><td>3</td><td>4</td></tr><tr><td><strong>CRUSTACEANS</strong></td><td></td><td></td><td>Melanopsis</td><td>7</td><td>9</td></tr><tr><td>Amphipode</td><td>7</td><td>13</td><td>Thiara</td><td>5</td><td>3</td></tr><tr><td>Isopode</td><td>3</td><td>3</td><td>Hydrobiidae</td><td>8</td><td>4</td></tr><tr><td>Atyidae</td><td>5</td><td>7</td><td>Neritidae</td><td>6</td><td>5</td></tr><tr><td>Grapsidae</td><td>5</td><td>5</td><td><strong>MICROBENTHOS</strong></td><td></td><td></td></tr><tr><td>Hymenosomatidae</td><td>7</td><td>5</td><td>Ostracodes</td><td>2</td><td>9</td></tr><tr><td>Palaemonidae</td><td>8</td><td>9</td><td>Copépodes</td><td>9</td><td>5</td></tr><tr><td></td><td></td><td></td><td>Hydracariens</td><td>5</td><td>4</td></tr></tbody></table>

The most pollutant-sensitive taxa have the highest scores.

* Formerly Megapodagrionidae

In the case of low taxonomic richness identified (less than 10 taxa), Mary and Archaimbault (2012) recommend the calculation of BSI and/or LCBI index scores and
the argumentation of the values obtained according to the characteristics of the environment, especially if they demonstrate good or very good biological quality. Indeed, a low taxonomic richness reflects, in the case of Lake Chad, the disturbances due to the invasion of Eichhornia crassipes. A good quality sampling point generally includes at least fifteen different taxa or characterizes a particular type of environment (source area, outcrop, seepage, etc.) (Mary, 2015).

<table><caption>Table 16: Quality classes for LCBI and BSI (7 unit samples)</caption><thead><tr><td>LCBI</td><td>BSI (Biosedimentary Index)</td><td>Quality</td></tr></thead><tbody><tr><td>LCBI ≤ 4,15</td><td>BSI ≤ 4,25</td><td>Bad</td></tr><tr><td>4,15 &lt; LCBI ≤ 4,85</td><td>4,25 &lt; BSI ≤ 4,75</td><td>Poor</td></tr><tr><td>4,85 &lt; LCBI ≤ 5,50</td><td>4,75 &lt; BSI ≤ 5,25</td><td>Fair</td></tr><tr><td>5,50 &lt; LCBI ≤ 6,50</td><td>5,50 &lt; BSI ≤ 6,00</td><td>Good</td></tr><tr><td>LCBI &gt; 6,50</td><td>BSI &gt; 6,00</td><td>Very good</td></tr></tbody></table>

## 4.9. Local adaptation strategies for disturbances linked to invasive plants

### 4.9.1. Local economic strategy for adaptation to disturbances linked to invasive plants

In any season on the water, the average rate of cleaning of the banks of Lake Chad is 8.6±0.55% while the average rate of use of methods of cleaning the bottom of Lake Chad is 2.8 ±0.89% Sahelian semi-arid zone within GICs and women's associations. To be able to catch fish, some women create oases for fishing and fish farming (93.12±0.44%) while the average rate of use (or valorization) of invasive plants is low 5.48±2.91% in the hydraulic zone of Lake Chad.

In any season on dry land, the average rate of cleaning of the banks of Lake Chad is 8.6±0.55% while the average rate of use of methods of cleaning the bottom of Lake Chad is 2.8±0.89% Sahelian zone within GICs and women's associations. To be able to catch fish, some women create oases for fishing and fish farming (93.12±0.44%) while the average rate of use (or valorization) of invasive plants is low 5.48±2.91% in the hydraulic zone of Lake Chad
<table><caption>Table 17: Economic strategy for adaptation to disturbances linked to invasive plants</caption><thead><tr><th rowspan="2"></th><th colspan="4">Economic adaptation strategy linked to water</th><th colspan="4">Economic adaptation strategy linked to land</th></tr><tr><th>Cleaning of the banks of Lake Chad (%)</th><th>Cleaning of the bottom of Lake Chad (%)</th><th>Development of oases for fishing and fish farming (%)</th><th>Use / Valorization of invasive plants (%)</th><th>Manual cleaning of invasive plants (%)</th><th>Chemical cleaning of invasive plants (%)</th><th>Development of invasive plant exploitation sites (%)</th><th>Use/valorization of invasive plants (%)</th></tr></thead><tbody><tr><td>Makary</td><td>8±0,3</td><td>2±0,9</td><td>93,7±0,9</td><td>08,8±0,9</td><td>8±0,2</td><td>2±0,3</td><td>38,27±8,17</td><td>05,2±0,9</td></tr><tr><td>Blangoua</td><td>9±0,9</td><td>1±0,3</td><td>92,9±0,7</td><td>07,3±0,3</td><td>9±1,5</td><td>3±0,5</td><td>49,32±1,32</td><td>04,1±0,3</td></tr><tr><td>Fotokol</td><td>8±0,7</td><td>1±0,7</td><td>92,7±0,4</td><td>06,2±0,7</td><td>7±0,9</td><td>2±0,6</td><td>37,56±4,13</td><td>07,1±0,7</td></tr><tr><td>Darak</td><td>9±0,4</td><td>1±0,4</td><td>92,8±0,9</td><td>01,5±0,4</td><td>8±0,4</td><td>3±0,3</td><td>44,13±2,22</td><td>08,1±0,4</td></tr><tr><td>Hilé Alifa</td><td>8±0,9</td><td>9±0,3</td><td>93,5±0,2</td><td>03,6±0,3</td><td>9±0,7</td><td>2±0,7</td><td>51,21±3,56</td><td>04,9±0,3</td></tr></tbody></table>

In the rainy season, the average use rate of fertilizers and chemical inputs is 86.40±5.55% among GIC women and 89.20±5.31% among association women, while the rate of using fertilizers and organic inputs is 16.40±9.12% among women in GICs and 13.20±4.02% within associations. The average rate of modification of the need for water to be put in the fields is 30.40±3.97% among the women of the associations and 33.80±3.42% the women of the GIC while the average rate of modification of spacing between lines is 15.20±2.68% for women in GICs and 14.60±3.84% within associations.

<table><caption>Table 18: Economic strategy for adapting agricultural production to disruptions linked to invasive plants</caption><thead><tr><th>Site</th><th></th><th>Use/cost of fertilizers and chemical inputs (%)</th><th>Use/cost of organic fertilizers (%)</th><th>Change in the need for water to be applied to the fields (%)</th><th>Changes in the spacings between the rows (%)</th><th>Changes in the spacings between the pockets during transplanting (%)</th><th>Change in depth of transplanting holes (%)</th></tr></thead><tbody><tr><td rowspan="5">Dry season</td><td>Makary</td><td>79±0,11</td><td>32±1,27</td><td>31±0,73</td><td>17±0,65</td><td>25±0,77</td><td>21±0,23</td></tr><tr><td>Blangoua</td><td>89±1,17</td><td>12±0,65</td><td>37±1,15</td><td>13±0,19</td><td>21±0,05</td><td>28±0,57</td></tr><tr><td>Fotokol</td><td>91±0,56</td><td>17±0,32</td><td>29±0,11</td><td>19±1,15</td><td>23±0,35</td><td>29±0,03</td></tr><tr><td>Darak</td><td>82±0,65</td><td>11±0,94</td><td>27±0,56</td><td>14±0,53</td><td>22±0,57</td><td>27±0,77</td></tr><tr><td>Hilé Alifa</td><td>91±2,72</td><td>10±0,15</td><td>28±0,21</td><td>13±0,12</td><td>28±0,63</td><td>24±0,13</td></tr><tr><td rowspan="5">Rainy season</td><td>Makary</td><td>81±0,05</td><td>9±0,13</td><td>35±0,59</td><td>11±0,15</td><td>20±0,15</td><td>21±0,27</td></tr><tr><td>Blangoua</td><td>87±0,93</td><td>11±0,23</td><td>39±2,72</td><td>16±0,55</td><td>22±0,09</td><td>20±0,37</td></tr><tr><td>Fotokol</td><td>91±1,59</td><td>18±0,19</td><td>33±0,76</td><td>18±0,32</td><td>21±0,94</td><td>27±0,36</td></tr><tr><td>Darak</td><td>94±2,07</td><td>17±0,32</td><td>32±0,77</td><td>10±0,39</td><td>27±0,67</td><td>21±0,55</td></tr><tr><td>Hilé Alifa</td><td>93±1,23</td><td>11±0,55</td><td>30±0,12</td><td>18±0,76</td><td>29±0,17</td><td>22±0,51</td></tr></tbody></table>

In the dry season, by means of modifications to the spacing between the pockets during transplanting in order to minimize losses when the plants emerge, it is 23.80±2.77% and 23.80±3.96 within the associations that within the associations while the average rate of modifications to the depth of transplanting holes in order to ensure the retention and saving of water at ground level is 25.80±3.27% within the associations and 22.20±2.77% in GIC. In the dry season, the average immediate sale after harvest, carried out within the GIC is 837.57±135.90 Kilogram/Season/woman in and
795.00±40.56 Kilogram/Season/woman in association while the average sale after harvest storage is 519.89±60.04 Kilogram/Season/woman in association and 596.6±100.44 Kilogram/Season/woman within the GIC. The transformations and sales of products carried out within the GICs is 23.37±22.02 Kilogram/Season/woman and in association, we note 04.00±02.54 Kilogram/Season/woman.

<table><caption>Table 19: Economic adaptation strategy linked to the market and the sale of products harvested by season in the face of disturbances linked to invasive plants</caption><thead><tr><th rowspan="2">Site</th><th rowspan="2"></th><th colspan="2">Immediate sale after harvest (KG/Season)</th><th colspan="2">Sale after harvest storage (KG/Season)</th><th colspan="2">Processing and Sale (KG/Season)</th></tr><tr><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th><th>Dry season</th><th>Rainy season</th></tr></thead><tbody><tr><td rowspan="5">Area invaded by <i>Eichhornia crassipes</i> (≤50%) and <i>Prosopis juliflora</i> (≥50%)</td><td>Makary</td><td>897,31 ± 90,31</td><td>678,45 ± 21,98</td><td>567,87 ± 42,21</td><td>678,12 ± 12,12</td><td>07,17 ± 4,01</td><td>06,88 ± 01,02</td></tr><tr><td>Blangoua</td><td>897,41 ± 54,13</td><td>791,23 ± 73,65</td><td>437,11 ± 04,01</td><td>597,13 ± 76,35</td><td>09,81 ± 02,99</td><td>05,73 ± 00,65</td></tr><tr><td>Fotokol</td><td>899,76 ± 21,53</td><td>902,87 ± 62,11</td><td>587,67 ± 20,03</td><td>701,11 ± 26,81</td><td>05,12 ± 01,04</td><td>09,19 ± 02,41</td></tr><tr><td>Darak</td><td>594,47 ± 23,23</td><td>804,54 ± 71,07</td><td>495,47 ± 33,00</td><td>482,17 ± 39,01</td><td>49,45 ± 03,06</td><td>22,27 ± 03,90</td></tr><tr><td>Hilé Alifa</td><td>898,93 ± 20,83</td><td>799,92 ± 96,78</td><td>511,37 ± 24,01</td><td>597,92 ± 96,08</td><td>45,31 ± 24,01</td><td>17,52 ± 06,98</td></tr><tr><td rowspan="5">Area invaded by <i>Eichhornia crassipes</i> (≥50%) and <i>Prosopis juliflora</i> (≤50%)</td><td>Makary</td><td>791,14 ± 38,41</td><td>798,97 ± 31,54</td><td>654,64 ± 33,01</td><td>791,01 ± 27,19</td><td>04,34 ± 03,36</td><td>01,79 ± 00,27</td></tr><tr><td>Blangoua</td><td>729,77 ± 23,92</td><td>877,65 ± 47,65</td><td>692,61 ± 39,43</td><td>797,12 ± 49,02</td><td>02,67 ± 01,4</td><td>07,82 ± 02,42</td></tr><tr><td>Fotokol</td><td>839,79 ± 31,97</td><td>879,91 ± 01,58</td><td>432,65 ± 13,01</td><td>416,14 ± 20,73</td><td>03,69 ± 01,37</td><td>01,14 ± 00,23</td></tr><tr><td>Darak</td><td>809,10 ± 53,41</td><td>780,34 ± 21,45</td><td>580,01 ± 34,76</td><td>683,79 ± 19,22</td><td>08,15 ± 04,22</td><td>08,39 ± 01,11</td></tr><tr><td>Hilé Alifa</td><td>805,24 ± 43,10</td><td>810,97 ± 10,93</td><td>621,41 ± 43,31</td><td>539,92 ± 21,11</td><td>01,41 ± 03,39</td><td>04,95 ± 01,09</td></tr></tbody></table>

In the rainy season, the average immediate post-harvest sale made within the GICs is 795.57±79.61 Kilogram/Season/woman and in association we have 829.57±46.23 Kilogram/Season/woman while the average sale after harvest and storage is 611.29±86.00 Kilogram/Season/woman within the GICs and 645.60±165.36 Kilogram/Season/woman within the associations. The transformations and sales of products carried out within the GICs is 12.32±7.23 Kilogram/Season/woman within the associations and 04.82±03.33 Kilogram/Season/woman within the GICs.

### 4.9.2. Local social strategy for adaptation to climate disruption within GICs and associations

In the dry season, the average rate of diversification of forms of mutual aid is 88.80±4.43% in association and 92.20±7.01% in GIC, while the average rate of Request for donation in the form of agricultural, seed and nursery equipment or support is 16.40±9.12% in association and 13.20±4.02% in GIC. Faced with climatic hazards, certain GICs and associations opt for prayer sessions or rites of invocation of the gods, including 30.40±3.97% in associations and 33.80±3.42% in GICs and this situation is
observed more in certain localities of the semi-arid Sahelian zone (in Guirvidig and Laf than in Mindif) according to Yakouba et al. (2017). Solidarity between members of certain GICs and associations is on average 15.20±2.68% in the dry season, while the average of favorable responses to inter-association requests (or GICs), a guarantee of solidarity with other GICs is 23.80±3.96% in the dry season.

<table><caption>Table 20: Social strategy to adapt field production during the dry season</caption><thead><tr><th>Site</th><th></th><th>Diversification of forms of mutual aid (%)</th><th>Request for donation (materials or agricultural support, seeds and nurseries) (%)</th><th>Prayer or rites of invocation of the gods (%)</th><th>Solidarity between members (%)</th><th>Solidarity with others GIC (%)</th></tr></thead><tbody><tr><td rowspan="5">Dry season</td><td>Makary</td><td>89±1,21</td><td>32±0,17</td><td>31±3,19</td><td>17±0,93</td><td>25±0,37</td></tr><tr><td>Blangoua</td><td>82±2,15</td><td>12±0,27</td><td>37±0,16</td><td>13±0,27</td><td>21±0,56</td></tr><tr><td>Fotokol</td><td>94±1,57</td><td>17±0,32</td><td>29±0,77</td><td>19±0,05</td><td>23±0,24</td></tr><tr><td>Darak</td><td>88±0,79</td><td>11±0,35</td><td>27±0,39</td><td>14±0,35</td><td>22±0,03</td></tr><tr><td>Hilé Alifa</td><td>91±2,65</td><td>10±0,75</td><td>28±1,65</td><td>13±0,13</td><td>28±0,37</td></tr><tr><td rowspan="5">Rainy season</td><td>Makary</td><td>21±0,07</td><td>89±3,56</td><td>91±7,75</td><td>37±0,63</td><td>2±0,05</td></tr><tr><td>Blangoua</td><td>28±0,33</td><td>99±6,37</td><td>81±0,36</td><td>65±1,36</td><td>2±0,03</td></tr><tr><td>Fotokol</td><td>29±0,56</td><td>76±1,63</td><td>97±2,55</td><td>79±2,31</td><td>1±0,07</td></tr><tr><td>Darak</td><td>27±0,36</td><td>80±0,01</td><td>91±1,33</td><td>67±0,03</td><td>7±1,63</td></tr><tr><td>Hilé Alifa</td><td>24±0,65</td><td>81±0,06</td><td>99±2,07</td><td>68±0,63</td><td>9±1,35</td></tr></tbody></table>

The social strategy to adapt field production during the rainy season indicates that the average rate of diversification of forms of mutual aid is 25.80±3.27% in associations and 22.20±2.77% in GICs, while that the average rate of donation requests in the form of agricultural materials or support, seeds and nurseries is 85.00±9.13% in association and 89.60±5.02% in GIC. Faced with climatic hazards, certain GICs and associations opt for prayer sessions or rites of invocation of the gods, including 91.80±7.01% in associations and 94.00±3.31% in GICs. Solidarity between the members of certain GICs and associations is on average 63.20±15.62% in associations and 88.00±7.42% in GICs, while the average of favorable responses to inter-associative requests (or GIC), a guarantee of solidarity with other GICs.

Social and religious adaptations result in the purchase and/or donation of nurseries and invocation rites in the event of a rainfall deficit scenario (Yakouba et al., 2017). Many beliefs attribute the decrease in “water coming from the sky” to divine punishment due to non-compliance with divine rules such as libidinal practices in the fields of production and the desecration of sacred places (Brou et al., 2005; Yakouba et al., 2017). This results in the organization of specific rituals performed in order to bring back the rain.

CONCLUSION
The objective of this study is to determine the effect of *Prosopis juliflora* and *Eichhornia crassipes* on biodiversity and the socio-economic adaptation strategies of women in the Lake Chad area.

In sum, on an average of 4,167±2,786 sampling points, an average of 165,667±2,804 *Eichhornia crassipes* plants was observed, with an average abundance-dominance index of 3,833±1,169 and an average recovery rate of the entire area of Lake Chad Cameroon which is 53.575±26.621%. However, the average regularity on the waters of Lake Chad is 0.598±0.217, higher in Makary (1.000) and lower in Blangoua (0.386). The average frequency of *Eichhornia crassipes* in the waters of Lake Chad Cameroon is 16.7±0.11%: the highest is that of Makary (36%), while those observed in Darak (08) and Hilé Alifa (08) are weak

Overall, unpolluted sites have an average SS of 22.04±9.45 mg/l, sites polluted by organic matter have an average SS of 24.07±8.22 mg/l while sites polluted by non-organic matter have a TSS of 23.43±1.41 mg/l. Sites polluted by organic matter have an average COD higher in the order of 34.63±15.18 mg/l while the unpolluted sites have an average COD of 32.18±16.19 mg/l, the sites polluted by non-organic matter have a D.C.O. of 32.56±12.02 mg/l.

In 2010, the sampling points surveyed made it possible to count a total of 124 aquifer species while in 2024, a total of 92 species were counted at the same sampling points surveyed. Since 2010, we note an average overall loss of aquatic biodiversity of 25.21±1.72% in the waters of Lake Chad and a loss of waterways due to invasive plants of 78.80±1.30%..

Women in the Lake Chad area and northern Cameroon carry out mainly agricultural subsistence activities. In any season on the water, the average rate of cleaning of spaces on the banks of Lake Chad for agricultural purposes is 8.6±0.55% while the average rate of use of methods for cleaning the bottom of the Lake Chad is 2.8±0.89% in Sahelian semi-arid zone (Area invaded by *Eichhornia crassipes* (≥50%) and *Prosopis juliflora* (≤50%)) within the GIC and women's association. To be able to catch fish, some women create oases for fishing and fish farming (93.12±0.44%) while the average rate of use (or valorization) of invasive plants is low 5.48±2.91% in the hydraulic zone of Lake Chad (Area invaded by *Eichhornia crassipes* (≤50%) and *Prosopis juliflora* (≥50%)).

In the rainy season, the average immediate post-harvest sale made within the GICs is 795.57±79.61 Kilogram/Season/woman and in association we have 829.57±46.23 Kilogram/Season/woman while the average sale after harvest and storage is 611.29±86.00 Kilogram/Season/woman within the GICs and 645.60±165.36 Kilogram/Season/woman within the associations. The transformations and sales of products carried out within the GICs is 12.32±7.23 Kilogram/Season/woman within the associations and 04.82±03.33 Kilogram/Season/woman within the GICs.
The social strategy to adapt field production during the rainy season indicates that the average rate of diversification of forms of mutual aid is 25.80±3.27% in associations and 22.20±2.77% in GICs, while that the average rate of donation requests in the form of agricultural materials or support, seeds and nurseries is 85.00±9.13% in association and 89.60±5.02% in GIC. Faced with climatic hazards, certain GICs and associations opt for prayer sessions or rites of invocation of the gods, including 91.80±7.01% in associations and 94.00±3.31% in GICs. Solidarity between the members of certain GICs and associations is on average 63.20±15.62% in associations and 88.00±7.42% in GICs, while the average of favorable responses to inter-associative requests (or GIC), a guarantee of solidarity with other GICs.

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EXERCISES AND CORRECTIONS ON THE IMPACT OF
THE PROLIFERATION OF INVASIVE PLANTS ON
BIODIVERSITY AND THE SOCIO-ECONOMIC
ADAPTATION STRATEGIES OF WOMEN IN THE LAKE
CHAD AREA

Exercise 1: Impact of the Proliferation of Invasive Plants on Biodiversity

**Question 1:** Describe how the proliferation of invasive plants, such as Eichhornia crassipes, affects biodiversity in the Lake Chad region.

**Question 2:** Discuss the specific impacts of these plants on the aquatic and terrestrial ecosystems around Lake Chad.

**Question 3:** What are the main local species threatened by the proliferation of invasive plants and why?

**Correction 1:**

**Answer 1:**

The proliferation of invasive plants, such as Eichhornia crassipes, can have major impacts on the biodiversity of the Lake Chad region. These invasive plants can:
- Obstruct aquatic habitats: By forming dense mats, they block the light necessary for photosynthesis of native aquatic plants, thus modifying habitats for fish and other aquatic organisms.

- Decrease water quality: The decomposition of invasive plants can lead to an increase in nutrients in the water, which can cause harmful algae blooms and harm water quality.

- Modify hydrological regimes: They can modify the flow of water, leading to changes in flow regimes and soil erosion.

**Answer 2:**

**Specific impacts include:**

- **Aquatic ecosystems:** Eichhornia crassipes creates obstacles to water circulation, which can lead to a decrease in dissolved oxygen, thereby affecting fish and other aquatic organisms.

- **Terrestrial ecosystems:** Invasive plants can reduce soil moisture by absorbing large amounts of water, which can affect native vegetation and the animals that depend on that vegetation.

**Answer 3:**

**The main threatened local species include:**

- **Endemic fish:** Certain species of fish from Lake Chad, such as Bagrus bayad, are threatened because they depend on clear, oxygen-rich aquatic habitats.

- **Native aquatic plants:** Local aquatic plants, such as water lilies, are in danger because they are smothered by dense mats of invasive plants.

- **Aquatic birds:** Birds that feed on fish and aquatic insects may also be affected by reduced fish populations and degradation of their habitats.

**Exercise 2: Socio-Economic Adaptation Strategies of Women in the Lake Chad Zone**

**Question 1:** Identify and describe three socio-economic adaptation strategies adopted by women in the Lake Chad area in the face of the impacts of invasive plants.

**Question 2:** Analyze how these strategies influence the economic and social resilience of women in this region.

**Question 3:** What challenges do women face in implementing these strategies and how can they be overcome?

**Correction 2:**
Answer 1:

Three coping strategies include:

- **Diversification of sources of income:** Women can turn to alternative economic activities, such as selling handicraft products, farming crops resistant to invasive plants, or breeding small animal species.

- **Implementation of water management techniques:** To cope with changes in hydrological regimes, women implement techniques such as the construction of dikes or canals to improve water management in agricultural fields.

- **Education and community awareness:** Women play a key role in raising awareness among local communities about the impacts of invasive plants and the adoption of sustainable practices to reduce their proliferation.

Answer 2:

These strategies influence resilience in the following ways:

- **Income diversification:** It allows women not to depend solely on activities affected by invasive plants, providing greater economic security.

- **Water management:** Improves water availability for crops, which can increase agricultural yields and stabilize income.

- **Community education:** Strengthens the capacity of communities to respond to environmental challenges and implement collective solutions.

Answer 3:

Challenges encountered include:

- **Limited access to financial resources:** Women may lack funds to invest in water management technologies or to diversify their economic activities.

- **Lack of training:** Insufficient training on invasive plant management techniques can limit the effectiveness of the strategies put in place.

- **Resistance to change:** Traditional habits and resistance to change within communities can hinder the adoption of new practices.

Possible solutions:

- **Access to microcredits:** Facilitate access to credits for women in order to invest in necessary tools and techniques.

- **Training programs:** Establish training programs to teach invasive plant management methods and water management skills.
- **Encouragement of community support:** Promote community initiatives and dialogues to promote acceptance and integration of new practices.

These exercises allow us to explore the impacts of invasive plants and the specific socio-economic responses of women in the Lake Chad region. They provide a basis for understanding environmental challenges and adaptation strategies in a complex context.
# CHAPITRE 7. ECOLOGICAL MODELING, FUEL ECONOMY, ENERGY AUTONOMY AND COMMUNITY ACCEPTABILITY OF IMPROVED STOVE-OVENS

Alexis DZOKOM

SAHEL NATURE CONSULTING FOR COMMUNITIES, Sahelian Zone Office, Cameroon
Department of Geography, Faculty of Art, Letter and Social Sciences, University of Maroua,
Cameroon

## ABSTRACT

In this work, the objective is to propose conceptual models of improved stoves capable of saving fuels and increasing the energy autonomy of cooking stoves. The stove construction technique has made it possible to manufacture ecological and sustainable improved cooking stoves. The Active Method of Research and Participatory Planning (MARPP) was used in the surveys. The ASTME711-87 method (2004) and the MA protocol, 108-P.Cal. 1.0 helped to obtain an average calorific value of 28.15±02.53MJ/kg, a maximum calorific and energy efficiency expected from combustion stoves of 50%. The average humidity rate in the combustion chamber is 23.08±02.52% governed by an average temperature before ignition of 33.85±05.86°C with an average heating time of the combustion chambers of 12.48±01.96 min. The protocol for measuring the collection efficiency and the performance of the fibrous media in filtration made it possible to determine a direct interception ratio of fine particles of 0.561±0.051 with a total average quantity of fluorescent particles injected of 13.92±0.74 L/min. When evaluating the performance of the fibrous media in filtration, the collection efficiency is 0.21±0.08 L/min while the pressure drop 0.023±0.005 L/min.). When analyzing the particles collected by the smoke filters of the improved stoves, the evaluation of the collection efficiency with the acid gas treatment filter indicates that CO₂ (67.10±0.63%) and (NH₄) HCO₃ (16.33±01.21%) were better filtered with the SAHEL NATURE CONSULTING stove. The highest fuel economy is 61.07±03.09% with an average of 0.716±0.093kg of charcoal produced. The energy autonomy of improved stoves has made it possible to observe that the maximum heat (871.02±58.32°C) obtained in the combustion chamber. The analysis of the socio-economic impacts of improved stoves in households, it appears that the most used heat in households is that of traditional African three-legged stoves due to its high accessibility rate and the weight of culinary habits although users have noted a high emission of smoke (80.1±0.5%).

**Keywords:** Improved culinary stoves, energy autonomy, fuel economy, community accessibility
INTRODUCTION

The study of hearths can be considered as a means of approaching the behavior of prehistoric men in relation to the use of fire (March, 1992). The hearth represents a technology that is as old as the discovery of fire and the civilization of man. The oldest known hearths date from approximately 400,000 years BC found in China (Sharma, 1993; Beatrix, 1995) to 500,000 BC (Europe) (Bonifay, 1976; Beatrix, 1995). Man (homo erectus, lower Paleolithic) lived mainly in caves and made fire in a circle of stones. In Africa, although there are some clues about ceramic hearths (1000 BC – 16th century), it is noted that there remains a significant amount of research and documentation to be done to trace their history and find their presence in the ancient cultures of the South (Dorst, 1960; Beatrix, 1995). The technical development of the hearth, the oven and the cooker only began with the industrial revolution in the 19th century. From the 19th century in Europe, the developments in technology and the most influential factors are (Beatrix, 1995): the overexploitation of forests followed by a shortage leading to a high price of firewood; the discovery and introduction of other fuels and energies, first in industry and then in households (coal, gas, oil, electricity, etc.); the development of new industrial technologies (cast iron, steam engine, light, steel, aluminum, etc.) and the growing need for a practical and efficient organization of the household and the kitchen. In Africa, in the Sahel, they started after the great drought of the end of 1970. In Central America, it was after the earthquake in Guatemala in 1976. These first waves, more or less at the initiative of Westerners, correspond to massive stoves with chimneys, with two or three pots or pans. They are generally complicated, expensive or difficult to obtain compared to traditional local stoves. In 1985, the improved stove project was requested by the State of Cameroon and it was not until 1989 that the pilot phase began. The motivations for such a request were due to the fact that programs concerning domestic energy, mostly in the form of stove projects using fuel efficiently, have been implemented for several decades. However, it is only in the last decades that significant technical and financial assistance has been provided, but in no case sufficient aid that would correspond to the importance of the sector (Klingshirn, 1995).

Nevertheless, the support given to the various projects and programs by governmental and non-governmental organizations has been sufficient to prove, over time, that programs, properly planned and implemented with the involvement and participation of users, producers and development managers, can have a significant impact at different levels and be among the most effective development efforts (Klingshirn, 1995). "Thanks to their integrated and interdisciplinary nature, combined with a participatory approach, household energy projects can be considered socially, economically and ecologically beneficial; they are also sustainable when properly managed" (Klingshirn, 1995).
Wood represents only 5.4% of the total energy consumed in the world, but it constitutes for 2/3 of humanity the main, if not almost exclusive, domestic energy resource (Doat, 1982). Stoves that have had incomplete combustion produce more charcoal than those that have gone all the way with this combustion (March, 1992).

In the context of this work, the objective is to propose conceptual models of improved stoves capable of saving fuels and increasing the energy autonomy of culinary stoves. The idea is to conduct a reflection in the direction of the design of a stove-oven, capable of consuming less wood while having a high energy efficiency and whose maximum temperature is maintained for a long time to not only ensure culinary requests, but also to allow the continuous production of heat energy transformable into electrical energy.

# 1- MATERIAL AND METHOD

## 1-1 Study sites

The study sites were identified in the Far North and North regions of Cameroon, Sahelian zone, in ten localities, with women's associative movements and common initiative groups (GIC). These are the localities of Mokolo, Maroua, Mora, Garoua, Guider (for the semi-arid Sahelian zone) and Waza, Makari, Lagdo, Yagoua and Maga (for the Sahelian humid zone).
<figure><img src="image_147.png" /><figcaption>Figure 1: Localities sites of the study area in the Sahelian regions of the Far North and North Cameroon</figcaption></figure>

Three localities in the North region were chosen for the study while the other seven localities belong to the Far North region. These localities were chosen because they are part of the wetlands and semi-arid zones and the different methods of using traditional stoves and ovens for culinary purposes.

## 1-2- Design and dimensioning of the structure of some improved stoves used in the Far North Cameroon

The stove construction technique developed in the workshop of the NGO SAHEL NATURE CONSULTING FOR COMMUNITIES (2023) consisted of cutting, folding, assembling and riveting using templates adapted to each model to be made. Production was carried out by technicians trained by the NGO SAHEL NATURE CONSULTING FOR COMMUNITIES (2023), and sales are left to women's associations after the project.

## 1-3- Materials for manufacturing the internal components of the hearths
From the point of view of their materials, the different types of known hearth-ovens can be classified into four classes:

### 1-3-1- Hearth-ovens made of earth and/or ceramic

In many cases, this category is made with a mixture of sand and clay. These hearth-ovens have a high thermal inertia, and the heating time as well as the cooling time is long. Hence the interest in dishes with a long cooking and simmering time.

### 1-3-2- Metal hearth-ovens

They can range from simple to complex. The simplest to make can be made from old cans and thus give rise to rustic, economical but not very resistant material. The coating that will be used is a mild steel sheet (sheet metal), with a minimum thickness of 0.6 mm.

### 1-3-3- Brick and cement hearth-ovens

Heart-ovens made of cement, briquettes or hearth-ovens that, in manufacturing, require the mixing of cement, brick and metal generally have a significantly longer lifespan than large earthen ovens, and generally do not have cracks. They often heat up quickly, compared to the heating of three-stone hearths and have a better known cooking method. Their only major drawback is their fairly high price (Doat, 1982).

## 1-4- Expected calorific and energy yield of combustion chambers.

Combustion is the most widespread process for the energy recovery of biomass with a contribution corresponding to 97% in the overall production of bioenergy. (Takali, 2015)

### 1-4-1- Factors entering into the overall expected calorific production of the combustion chamber.

#### a) Moisture content

In the context of this work, the determination of the moisture content was inspired by the methodological measurement procedures developed by Tobiasson et al., (1991). The moisture content expresses the water content and strongly influences the calorific value and the ignition capacity of the briquettes. The moisture content is obtained by the following formula:

$$W(\%) = \frac{(\text{Wet matter} - \text{Dry matter})}{(\text{Wet matter})} \times 100 \quad (1)$$

With: W: moisture content; Wet M: mass of the sample; Dry M: mass obtained after heating to 105°C in an oven.

#### b) Calorific value

The ASTME711-87 method (2004) and the MA protocol, 108-P.Cal. 1.0 helped to measure and calculate the calorific value. The heat capacity of the bomb and the tank
was calculated from a test done with benzoic acid. The calorific value of the samples is measured by the following equation:

$$ P. C. = \frac{[1000 \times (T^{\circ}f - T^{\circ}i) \times W - (H_h \times a)]}{b} \quad (2) $$

Where P.C.: calorific value of the sample (kJ/kg); T°f: maximum final temperature of the water in the tank after ignition (°C); T°i: initial temperature of the water in the tank before ignition (°C); W: calorific capacity of the calorimeter [constant of the device determined with benzoic acid (kJ/°C)]; Hh: calorific value of the mineral oil (kJ/kg); b: weight of the sample (g); a: weight of the oil (g).

### c) Expected combustion tests in the combustion chamber

The combustion test allowed us to determine:

The combustion time of each combustible briquette;

The mass of the fuel (ash) post-combustion;

Mass losses

### d) Determination of the ease of ignition of the fuels in the combustion chamber

The ignition test consists of determining the ease of ignition of the fuels in 5 minutes. It consists of measuring, using a thermocouple, the fire temperature of an incandescent sample (T°al). The ignition of the fuel lasts 1 minute and the measurement of the temperature of the incandescent part of the fuel is done at 25 s (T°t') and at 300 s (T°t''). The ease of ignition is written by Formula 1 (Souleymane et al., 2020).

$$ T^{\circ}_{al} = T^{\circ}_{f''} - T^{\circ}_{f'} \quad (3) $$

T°al: ignition temperature, T°t'': temperature at t equal to 5 min, T°t': temperature at t equal to 25 s.

### e) Determination of the combustion time of fuels in the combustion chamber

The combustion time (CD) test consists of determining the total combustion time of 600 g of fuels introduced into an improved fireplace with a clay combustion chamber. It begins with ignition until the ash is obtained. The combustion time is written according to Formula 2.

$$ \Delta t = t_f - t_i \quad (4) $$

Δt: time for the fuels to burn; t_f: end of combustion time of the fuels; t_i: start of combustion time of the samples

### f) Determination of the energy efficiency of the combustion chambers

The study on the energy efficiency of the fuels lasts 2 hours. It is determined from the start and duration of boiling of the water, the quantities of remaining and evaporated water and then the temperature of the fuel fire. The results are obtained according to the relations below:

* **Start of heating of the combustion chambers**
The start of boiling of the water corresponds to the time it takes for the water to boil. It is expressed as follows

$$teb = t_{\text{deb}} - t_{\text{p}} \quad (5)$$

teb: start of boiling of the water; t deb: time from which the water boils; t p: time from which the pan is placed on the fire.

## Heating time of the combustion chambers

This corresponds to the boiling time of the water. To do this, we take the difference between the time when the water stops boiling and the time when boiling begins. The expression is as follows

$$\Delta t = t_{\text{feb}} - t_{\text{deb}} \quad (6)$$

$\Delta t$: boiling time of the water (min); t feb: end of boiling of the water; t deb: start of boiling of the water.

### 1-4-2- Decontamination of fumes and toxic pollutants in the air

As part of this work, purifying the fumes that could be emitted by the hearth-oven means designing a small absorbent filter that will have the capacity to retain all the acidic, basic or simply toxic pollutants resulting from the combustion of fuels.

#### 1-4-2-1- Manufacturing materials of the "pleated cartridge filter" for fumes

According to Laurence (2006), filter cartridges are made up of pleated fibrous media placed under

#### 1-4-2-2- Manufacturing materials of the "pleated cartridge filter" of fumes

According to Laurence (2006), filter cartridges are made of pleated fibrous media placed in a cylindrical shape, while cassettes are flat pleated filters. Although there are other types of filters based on non-woven fibrous media ("depth" cartridge filters, flat filters), pleated filters are by far the most used (Colin, 2013).

According to this author (Colin, 2013), for an equivalent size, pleating makes it possible to obtain filtration surfaces more than 10 times greater than flat filters and two geometric quantities are generally used to characterize them. Collection efficiency measurement protocol

According to Galbrun, (2007), the main air flow is generated by creating a depression downstream of the collection system using a venturi pump operating on compressed air, whose flow rate can reach 30L/min. A fraction $\chi$ of the injected air is taken upstream of the collection system using a vane pump and passes through a bag filter, which provides access to the total quantity of fluorescent particles injected which is equal to

$$n_1 = \left[ \frac{(1-\chi)}{\chi} \right] n_0 \quad (7)$$

$n_0$ being the total quantity of fluorescent particles collected on the filter.
The collection efficiency is then calculated by taking the ratio of the amount of particles collected divided by the amount of particles introduced into the collection cell:

$$ \eta = \frac{n_2+n_3}{n_1} \qquad (8) $$

### 1-4-2-3- Sizing and permeability models of fibrous media

From Darcy's law, modeling the flow of a gas in a porous medium amounts to determining an expression for the permeability (Colin, 2013). In the case of a monomodal fiber size distribution, k is a function of the solid volume fraction of the media, α, and the fiber radius r as deduced by the formula:

$$ k = r^2 \cdot f(\alpha) \qquad (9) $$

f (α), called dimensionless permeability, can be calculated from considerations on an arrangement of fibers, subjected to the drag force resulting from a fluid flow (Thomas, 2001; Colin, 2013).

### 1-4-2-4- Performance of fibrous media in filtration

When used as a filtration system, the performance of fibrous media is assessed by its collection efficiency (E) and its pressure drop (ΔP). A “good filter” must have a low pressure drop and a high efficiency. This characteristic can be assessed by a quality factor, called figure of merit (Colin, 2013):

$$ FOM = \frac{-\ln(1-E)}{\Delta P} \qquad (10) $$

### 1-4-2-5- Collection efficiency

The efficiency is determined experimentally (1 – (Cp downstream /Cp upstream)); however, it is possible, under certain conditions, to calculate it from the expressions of unit collection efficiency of a fiber and the structural parameters of the filter.

The unit collection efficiency of a fiber is a function of several collection mechanisms that intervene more or less significantly depending on the particle size:

- Brownian diffusion for $dp < 1$ µm (figure 20),

- Direct interception for $dp > 0.1$ µm (figure 21),

- Inertial impaction for $dp > 1$ µm (figure 22),

- Sedimentation, generally neglected for particles with a diameter of less than 10 µm,

- Possible electrostatic effects.

### 1-4-2-5-1- Collection by Brownian diffusion.

Due to collisions with gas molecules, particles of dimensions smaller than or equivalent to the mean free path of gas molecules (λ=0.067 µm for air) travel a random oscillating trajectory which considerably increases the probability of interception by the fibers (Laurence, 2006). Particle capture by Brownian diffusion is characterized by the Peclet number (Pe) which describes the relationship between particle transport by convection and transport by diffusion:

$$ Pe = \frac{d_p U_0}{D_{diff}} \qquad (11) $$
With $U_0$= superficial velocity of the fluid (m.s⁻¹)

Ddiff= Brownian diffusion coefficient (m².s⁻¹)

For a spherical particle, this coefficient is written as: : $D_{diff} = \frac{kTCu}{3\pi\mu d_p}$ (12)

With k Boltzmann constant [k= 1,380 658· 10⁻²³ J·K⁻¹],

T temperature (K),

μ dynamic viscosity of the gas (Pa·s),

Cu Cunningham correction coefficient.

The Cunningham correction coefficient (Cu) is a factor that takes into account the discontinuities of the medium when the particle size is close to the mean free path of the gas molecules (Laurence, 2006).

$$C_u = 1 + Kn_p \left[ 1,207 + 0,44 \exp \left( \frac{-0,78}{Kn_p} \right) \right] \quad (13)$$

With Knp Knudsen number relative to the particle:

$$Kn_p = \frac{2\lambda}{d_p} \quad (14)$$

In the flow, small diameter particles (dp < 1 µm) are not subject to any interaction other than collisions with the carrier gas molecules. They follow random trajectories, independent of the streamlines (Colin, 2013).

<figure><img src="image_148.png" /><figcaption>Figure 2: Schematic of the Brownian diffusion collection mechanism (Bémer et al., 2006, and Colin, 2013).</figcaption></figure>

### 1-4-2-5-2- Collection by interception.

Particles that follow the streamlines of the carrier gas (dp > 0.1 µm) can be intercepted by a fiber if the distance between them becomes smaller than their radius. The interception collection mechanism is independent of the velocity; it depends only on the geometry of the particles and is described by the ratio between the particle diameter and the fiber diameter (Colin, 2013):

$$R = \frac{d_p}{d_f} \quad (15)$$
<figure><img src="image_149.png" /><figcaption>Figure 3: Schematic of the interception collection mechanism (Bémer et al., 2006 and Colin, 2013)</figcaption></figure>

### 1-4-2-5-3- Collection by inertial impaction.

Large particles (dp > 1µm), under the effect of their inertia, tend to leave the streamlines of the carrier gas and follow rectilinear trajectories (Colin, 2013).

$$St = \frac{\rho_P \times d_P^2 \times v_i}{\mu \times d} \quad (16)$$

Collection by inertial impaction is characterized by the Stokes number (St), which expresses the ratio between the kinetic energy of the particle and the energy dissipated by friction with the fluid (Laurence, 2006).

<figure><img src="image_150.png" /><figcaption>Figure 4: Schematic of the inertial impaction collection mechanism (Bémer et al., 2006; Colin, 2013).</figcaption></figure>

### 1-4-2-5-4- Sieving.

Sedimentation (sieving), generally neglected for particles with a diameter of less than 10 µm, is the predominant capture mechanism when the particles have a size greater
than or equal to the characteristic dimension of the pores of the fibrous media (Colin,
(2013))

<figure><img src="image_151.png" /><figcaption>**Figure 5:** Mechanisms of particle capture on a collector fiber by sieving (Laurence, 2006)</figcaption></figure>

**1-4-2-5-5- Collection by electrostatic effects.**

Some electrostatic filters are composed of polarized fibers. Under the effect of electrostatic forces, the trajectory of a charged particle can be deflected in the vicinity of a fiber and the particle can attach itself to it (Bémer et al., 2006, ; Colin, 2013).

<figure><img src="image_152.png" /><figcaption>**Figure 6:** Particle capture mechanisms on a collector fiber by electrostatic effects
(Laurence, 2006)</figcaption></figure>

**1-5- Fuel economy and energy autonomy of improved stoves**

The Active Research and Participatory Planning Method (MARPP) used in this work consisted of more or less structured interviews. This socio-economic data collection tool aims to obtain information in person, individually or in small groups, through a series of questions asked (Dzokom, 2021). The information collected is recorded in a sheet serving as a conversation guide with the possibility of readjusting the questions during the interview. This data collection method was carried out mainly during the intense activities of using improved stoves in households in the Sahelian zone of Cameroon.

**2- RESULT AND DISCUSSION**

**2-1- Design and dimensioning of the structure of some improved stoves used in the Far North of Cameroon**

In the Far North of Cameroon, the cities that have benefited greatly from the projects related to improved stoves are Maroua, Mokolo, Mora, Yagoua, Kaélé, Maga and
Kousseri. Popularized under the popular name of Katindé Njamndi (Multi pot), the stoves made from recovered sheet metal (200 l drums, vehicle carcasses) were intended for the use of wood fuel by women in households. The diameters of the stoves vary between 300 and 600 mm for respective prices between 1300 and 5500 FCFA in 1993.

<figure><img src="image_153.png" /><figcaption>**Figure 7: Improved stoves in Maroua-Cameroon**</figcaption></figure>

An improved stove is a stove that is built to use the same local materials as the traditional stove but with the aim of reducing smoke emissions, common diseases and infections that these smokes cause, reducing deforestation and making traditional stoves efficient by improving them. (Akouehou et al., 2012). Designing ecological improved stoves-ovens must be able to ensure energy efficiency that can produce significant energy output while minimizing fuel consumption. Its sizing depends on the shape and size of the pots.

As part of our study, we aim to design an ecological improved stove-oven whose shape and bottom should have the following characteristics:

* Lower fuel consumption than the traditional three-legged stove;

* Higher energy efficiency than the traditional three-legged stove;

* The production of fumes and dirt is lower than that of the traditional three-legged hearth.

The dimensional characteristics of the ecological hearth-oven that we aspire to set up, taking into account socio-economic and environmental realities, aim to make viable a system that, until recently, was not very important and did not attract much interest. In other words, the ecological hearth-oven that we size must provide electrical energy.

## 2-2- Characteristics of improved hearths
From the point of view of their materials, the different types of known hearth-ovens can be classified into four classes:

## 2-3- Earth and/or ceramic hearth-ovens

In many cases, this category is made with a mixture of sand and clay. These hearth-ovens have a high thermal inertia, and the heating time as well as the cooling time is long. Hence the interest in dishes with a long cooking and simmering time.

Their construction techniques are simple because they are similar to traditional masonry and the construction materials needed for their construction are shovels, trowels, sieves, briquette molds, etc. (depending on the various unlisted literature) (Doat, 1982)

<table><caption>Table 1: Different materials for manufacturing improved earthenware (clay) hearth-ovens</caption><thead><tr><th>CHARACTERISTICS</th><th colspan="2">MEDIUM MODEL</th><th colspan="3">LARGE MODEL</th></tr></thead><tbody><tr><td>Type of hearth:</td><td colspan="5">Ecological clay hearth-oven (or ALZO cement)</td></tr><tr><td>Number of households</td><td>One hearth</td><td>Two hearths</td><td>Three hearths</td><td>Four hearths</td><td>Five hearths</td></tr><tr><td>Type of clay</td><td colspan="5">Earthenware clays, refractory clays, stoneware clays, raku clays, etc.</td></tr><tr><td>Manufacturing temperature (resistance)</td><td colspan="5">950° to 1100° approximately</td></tr><tr><td rowspan="6">Material</td><td>Clay</td><td>*</td><td></td><td>*</td><td></td></tr><tr><td>Straw</td><td>**</td><td></td><td>**</td><td></td></tr><tr><td>Ash</td><td>***</td><td></td><td>***</td><td></td></tr><tr><td>Manure</td><td colspan="2">Animal dung</td><td colspan="2">Animal dung</td></tr><tr><td>Water</td><td colspan="2">5 to 10 (liters)</td><td colspan="2">15 to 40 (liters)</td></tr><tr><td></td><td colspan="2"></td><td colspan="2"></td></tr></tbody></table>

For Doat, 1982, these are hearth-ovens made of pottery built in fired clay, are light and heat much more quickly than the previous one while retaining heat moderately. According to Mbaye (2011), the ceramic insert with a clay grain size should preferably not exceed 0.5 mm.

## 2-4- Metal hearth-ovens

They can range from simple to complex. The simplest to make can be made from old drums and thus give rise to rustic, economical but not very resistant material. The covering that will be used is a mild steel sheet (sheet metal), with a minimum thickness of 0.6 mm.

<footnote>* any type of clay that can meet the requirement of pottery</footnote>

<footnote>** straw from plant debris</footnote>

<footnote>*** ash from the incineration of dry plants</footnote>
<table><caption>Table 2: Different materials for manufacturing improved hearth-ovens (in metal)</caption><thead><tr><th>CHARACTERISTICS</th><th colspan="2">MEDIUM MODEL</th><th colspan="3">LARGE MODEL</th></tr></thead><tbody><tr><td>Type of hearth:</td><td colspan="5">Ecological metal fireplace oven (ALZO)</td></tr><tr><td>Number of households</td><td>One hearth</td><td>Two hearths</td><td>Tree hearths</td><td>Four hearths</td><td>Five hearths</td></tr><tr><td>Type of metal</td><td colspan="5">Steel, aluminum, iron, stainless steel,...</td></tr><tr><td>Welding alloy</td><td colspan="5">Tin, copper....</td></tr><tr><td rowspan="4">Material</td><td>Steel</td><td>*</td><td></td><td></td><td>*</td></tr><tr><td>Stainless steel</td><td>***</td><td></td><td></td><td>**</td></tr><tr><td>Iron</td><td>***</td><td></td><td></td><td>***</td></tr><tr><td>Aluminium</td><td>**</td><td></td><td></td><td>***</td></tr></tbody></table>

Unlike earthen stoves, metal hearths with a chimney, a grate, holes and lids are efficient cookers whose costs are often incompatible with local purchasing power and possibilities (Doat, 1982).

## 2-4- Brick and cement hearths

Hearths made of cement, briquettes or hearths that, in their manufacture, require a mixture of cement, brick and metal generally have a much longer lifespan than large earthen stoves and generally do not have cracks. They often heat up quickly, compared to the heating of three-stone hearths and have a better-known cooking method. Their only major drawback is their relatively high price (Doat, 1982).

Furthermore, for Mbaye (2011), the thickness of the sheet metal must not exceed 1.2 mm. If the coating used is that of a recovered sheet, direct exposure to fire (under high temperature) for about an hour improves the resistance and finish of the hearth. The ceramic insert used in the manufacture of the hearth must be made from suitable clay and fired uniformly between 700°C and 900°C in a kiln. The grid (base of the ceramic insert), according to Mbaye (2011), must have small holes separated by at least 15 mm by material. The holes must measure from 10 to 20 mm.

<footnote>* any type of pure metal</footnote>

<footnote>** scrap metal</footnote>

<footnote>*** any type of scrap metal or alloy</footnote>
<table><caption>Table 3: Different materials for manufacturing improved earthenware (clay) hearths-ovens</caption><thead><tr><th>Characteristics</th><th colspan="2">MEDIUM MODEL</th><th colspan="2">LARGE MODEL</th></tr></thead><tbody><tr><td>Type of hearth:</td><td colspan="4">Ecological clay (or cement) hearth-oven</td></tr><tr><td>Number of households</td><td>One hearth</td><td>Two hearths</td><td>Tree hearths</td><td>Four hearths</td><td>Five hearths</td></tr><tr><td>Cement type</td><td colspan="4">Earthenware clays, refractory clays, stoneware clays, raku clays, etc.</td></tr><tr><td>Manufacturing method</td><td colspan="4">(resistance) Cement-sand-water dosage</td></tr><tr><td rowspan="3">Material quantity</td><td>Cement</td><td colspan="3">*</td></tr><tr><td>Sand</td><td>Fine ± semi coarse</td><td colspan="2">Fine + semi-coarse + coarse</td></tr><tr><td>Water</td><td>5 to 10 (liters)</td><td colspan="2">15 to 40 (liters)</td></tr><tr><td>Material content</td><td colspan="4">Depends on the texture of the materials and the size of the pots</td></tr></tbody></table>

## 2-5- The mixed clay-metal hearth-ovens of SAHEL NATURE CONSULTING

The metal hearth-oven that we designed is made from old sheets and thus gives rise to rustic, economical and more or less resistant material. The coating that is used is a mild steel sheet (sheet), with a minimum thickness of 0.6 mm. The combustion chamber is made with a mixture of sand (03%) and clay (97%)

<table><caption>Table 4: Some prototypes of improved hearths studied in Maroua-Cameroon</caption><thead><tr><th>Origin</th><th>Name of the hearth</th><th>Materials</th><th>Size (mm Ø)</th><th>Thermal efficiency in the laboratory</th><th>Fuel economy (in the field)</th><th>Unit cost</th></tr></thead><tbody><tr><td>Mali, Niger</td><td>Mali: Téliman<br/>Niger: Mai Sauki</td><td>Recycled sheet metal, barrels, black sheet metal</td><td>210-650</td><td>26 à 30 %</td><td>30 à 40 %</td><td>550-950</td></tr><tr><td>ONG S.N.C. C. (2023)</td><td>ALZO</td><td>Recycled sheet metal</td><td>210-650</td><td>26 à 30 %</td><td>30 à 40 %</td><td>550-950</td></tr><tr><td colspan="7">Source: Sahel Nature Consulting for Communities, Sahelian Zone Camero on (2023)</td></tr><tr><td>Mali, Niger</td><td>Cameroon:<br/>Katindé Njamndi<br/>Mali: Nafacaman,<br/>Multi mixed pot<br/>Niger: Multi pot</td><td>Drums, black sheet metal, salvaged sheet metal, etc.</td><td>180-220</td><td>27 to 32% (in laboratory) in Mali and 23% (Burkina and Niger)</td><td>40 à 50 % au Mali et 25 % (Burkina and Niger)</td><td>1.800-2.300</td></tr><tr><td colspan="7">Source: DNAS-GTZ, Anke Weymann</td></tr><tr><td>Burkina Faso<br/>Cameroun</td><td>Cameroun:<br/>Katindé loppé</td><td>Red clay</td><td>190-240</td><td>27 à 32% (en laboratoire) au Cameroun et 23 % (Burkina)</td><td>40 à 50 % au Cameroun et 25 % (Burkina)</td><td>2000-3000</td></tr></tbody></table>

<footnote>* any type of cement that can meet the requirement of solidity</footnote>
Bolivie: La Paz

Foyer Amélioré

Argile rouge,
céramique, argile

270

19% (aluminum pot, ø 200 mm) 24% (aluminum pot, ø 260 mm)

20 %

2000-3000

<figure><img src="image_154.png" /></figure>

Source: Augusto Rocha, AMCPP

The dimensional characteristics of the ecological hearth-oven that we aspire to set up, taking into account socio-economic and even environmental realities, aims to make viable a system that, until recently, did not have great importance and did not attract great interest. In other words, the ecological hearth-oven that we aim to size must meet the need to provide electrical energy. Thus, the various dimensions of the components of the hearth are found in the following tables:

<table><caption>Table 5: Different dimensions of improved ecological hearth-ovens made of clay</caption><thead><tr><th>Characteristics</th><th></th><th>MEDIUM MODEL</th><th>LARGE MODEL</th></tr></thead><tbody><tr><td>Exterior dimension</td><td></td><td>55-65 cm</td><td>70-75 cm</td></tr><tr><td>Interior dimension</td><td></td><td>30-50 cm</td><td>40-60 cm</td></tr><tr><td>Combustion chamber dimension</td><td></td><td>15-25 cm</td><td>20-30 cm</td></tr><tr><td>Firebox section</td><td></td><td>30x50 cm</td><td>40x60 cm</td></tr><tr><td rowspan="5">Dimensions :</td><td>Door (combustible entrance)</td><td>Circular shape 20x20 cm</td><td>25x25 cm</td></tr><tr><td></td><td>Rectangular shape 20x25 cm</td><td>20x30 cm</td></tr><tr><td>Height</td><td></td><td>25-30 cm</td><td>45-50 cm</td></tr><tr><td>Built-in height</td><td></td><td>15-20 cm</td><td>20-25 cm</td></tr><tr><td>Boiler (capacity)</td><td></td><td>15 000 à 18 000 cm³</td><td>19 000 à 20 000 cm³</td></tr><tr><td rowspan="6">Chimney</td><td>Fume cooler (L×W×H)</td><td></td><td>30×17×38 cm³</td><td>30×17×38 cm³</td></tr><tr><td>Luminous surface* (h x w)</td><td></td><td>40 x 35 cm</td><td>60 x 45 cm</td></tr><tr><td>Conduit section (Ø)</td><td></td><td>20 cm</td><td>30 cm</td></tr><tr><td>Conduit volume</td><td></td><td>63 000-95 000 cm³</td><td>354 000-495 000 cm³</td></tr><tr><td>Conduit height</td><td></td><td>200-300 cm</td><td>500-700 cm</td></tr></tbody></table>

## 2-6- Expected calorific and energy efficiency of combustion hearths.

The average humidity rate in the combustion chamber is 23.08±02.52% and the calorific value measured in the combustion chamber is 28.15±02.53MJ/kg. During the expected combustion tests in the combustion chamber, the average mass of the fuel before combustion was observed to be 12.71±08.55 gr, with an average mass of the post-combustion fuel of 01.77±00.58 gr and mass losses of 86.07±07.97% for an average combustion time of 15.24 ± 1.66 minutes.

<footnote>* The luminous surface is the open surface of the hearth and which is a function of the volume of the combustion chamber to be heated</footnote>