# Effects of Ecological Charcoal Production Processes Based on *Eichhornia crassipes* on its Characteristics as Cooking Energy

Alexis DZOKOM¹, Joel TIZE KODA², Pierre METSENA³, Fadimatou HAMADOU², Ezekiel KODJI¹, Roger DJOULDE DARMAN³

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

²Department of Renewable Energy, National Advanced School of Engineering, University of Maroua, Cameroon

³Department of Agriculture Animal Husbandry and By-Products, National Advanced School of Engineering, University of Maroua, Cameroon

**Abstract:**

*Eichhornia crassipes* is an invasive plant in the waters of Lake Chad. The ecological problems caused by its permanent and invasive presence lead to search solutions. Thus its valuation as cooking energy is an option whose objective is to assert the effect of production processes of ecological coal based on *Eichhornia crassipes* on their performance as cooking energy. The collection and sorting of these plants made it possible to prepare the raw material while their pre-treatment made it possible to carry out the anaerobic carbonization between 400-600°C on the one hand, and on the other hand, the semi-decomposition of *Eichhornia crassipes* biomass allowed us to have a raw material ready after 14 ± 03 days. Hygro-calorific characterization show that the ecological charcoal based on decomposed *Eichhornia crassipes* has 4.401±0.972% as moisture content average with a calorific value average of 17.825±8.308 MJ/Kg. The ecological charcoal based of carbonized *Eichhornia crassipes* has 3.79±1.05% as moisture content with average calorific value 21.05±7.76MJ/Kg. The chemical characterization show that the ecological charcoal based on charred *Eichhornia crassipes* has an average volatile matter rate of 26.87 ± 1.55%, a low average fixed carbon rate of 86.73 ± 2.67% and an average ash content 2.69 ± 0.33% while ecological coal based on decomposed *Eichhornia crassipes* has an average volatile matter rate of 22.059 ± 1.298%, an average fixed carbon rate of 74.496 ± 1.716 % and an average ash content of 1.97 ±0.72%. The Improved Culinary Furnace test, charred *Eichhornia crassipes* charcoal bonded to clay lasts in the fire longer time average, 46 minutes 10 seconds, when burning emitting 6.72±1.49 grams of ash average with 93.02±0.91% as mass loss average while the decomposed *Eichhornia crassipes* charcoal has a low burning time, 43 minutes 33 seconds, emitting 12.01±0.09 grams as ash average with 90.05±0.95% as mass loss average.

**Keywords:** *Eichhornia crassipes*, ecological charcoal, charcoal briquette

**Introduction**

*Eichhornia crassipes* is a free-floating aquatic plant on water's surface. Native to the Amazon basin in South America, this macrophyte aquatic plant, of the Pontederiaceae family and whose name Eichhornia is derived from the well-known 19th century Prussian politician, J.A.F. Eichhorn, is the most difficult to control in the world [1,2,3,4]. Widespread throughout the world in the late 19th and early 20th century, today this tropical plant is well known for its rapid reproductive capacity whose population can double in just twelve days [5, 6 and 7]. *Eichhornia crassipes* proliferation's makes it an invasive plant, raising it to the same level as weeds. Its germination and spread are rapid when environmental and ecological conditions are met. Ecological damage then ensues, such as: the obstruction of navigation routes; the disappearance of certain aquatic species; the disappearance of fishing areas and the appearance of certain waterborne diseases such as malaria. During their period of proliferation, whatever the mitigation methods applied, *Eichhornia crassipes* disappears in one place to resurface just as quickly in another place [8]. However, although it is possible to control it biologically and naturally, the persistence of favorable environment to their reproduction, such as that the abundance of space and nutrients doubled at a good medium temperature cause this plant to spread so prolifically that it covers water's surfaces in record time with a floating mat-like cover [9,10]. Considered as an ornamental plant by gardeners and botanists, because of its pretty purplish blue flowers and its

round and oval leaves, *Eichhornia crassipes* was propagated in many countries such as Latin America, the Caribbean, Africa, Southeast Asia and the Pacific more than a century ago because it was highly prized [9, 10, 11 and 12]. *Eichhornia crassipes* seeds hibernate over a dormant period of 15 to 20 years. *Eichhornia crassipes* contains lignocellulose (60% cellulose, 8% hemicellulose and 17% lignin) and a good part of carbon nitrate, which gives it characteristics of an alternative directly usable as renewable energy source [14, 15].

Rising prices of fossil energy and the problem of global warming have led to a major effort to promote renewable energies. This has intensified the search for alternatives to fossil fuels to facing modernization and industrialization [9]. Exacerbated by soaring energy costs, water hyacinth holds great promise in this regard for the biofuels industry of the 21st century [16]. The production methods developed by [9] made it possible to produce ecological coal of high value. The pyrolysis (or carbonization) method between [400-800] °C converts raw materials into carbon by minimizing the volatile matter content and increasing the carbon content of the material. In this study, the objective is to produce ecological charcoal based on *Eichhornia crassipes* to contribute to the fight against the invasion of Lake Chad water's surfaces.

## 1. Materials and Methods

### 1.1. Study zone

This study was carried out in five districts around Lake Chad on the Cameroon side. Villages crossed by this lake experience the invasion of
Lake Chad water's surfaces by *Eichhornia crassipes*. These areas have been represented in the following table:

<figure><img src="image_1.png" /><figcaption>Figure 1: Map of the study area</figcaption></figure>

## 1.2. *Eichhornia crassipes* briquette manufacturing process

### a) Preparation of the raw material

The overall preparation process was carried out according to the following scheme:

<figure><img src="image_2.png" /><figcaption>Figure 2: Raw material preparation scheme</figcaption></figure>

### b) Carbonization process

The carbonization was carried out following the methodology developed by [28]. It consisted in carbonizing the dry biomass in a carbonizer at a temperature between 400-600°C.

<figure><img src="image_3.png" /><figcaption>Figure 3: Scheme of production of ecological charcoal based on *Eichhornia crassipes*</figcaption></figure>

During the carbonization, biochar is produced, of blackish color which, crushed, sieved and mixed with the binder, can be molded through a manually operated compaction and extrusion system to obtain ecological charcoal/ecological briquettes.

### c) Semi-decomposition process

During semi-decomposition, the methodology developed by [9] consisted of decomposing the biomass in a hermetically sealed plastic bag. The materials used are: Biomass: chopped and dried

stem of *Eichhornia crassipes*, Polyethylene decomposition bags (plastic bag with a thickness of more than 60µm, microorganism decomposition solution (EM1 solution) to accelerate the decomposition activity of microorganisms on the stem of chopped and dried Eichhornia crassipes. The process of semi-decomposition lasts about 14 ± 03 days with reversals after every 07 ± 02 days.

## 1.3. Hygro-calorific characterization of *Eichhornia crassipes*'s charcoal

### 1.3.1. Moisture content

Determination of the moisture content was inspired by the methodological measurement procedures developed by [17]. Moisture content expresses the water content and has a strong influence on the calorific value and the ignition capacity of charcoal briquettes. Moisture content is obtained by the following formula:

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

With: W: moisture content; M wet: mass of the sample; M dry: mass obtained after heating at 105°C in an oven.

### 1.3.2. Calorific value

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

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

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

## 1.4. Chemical characterization of *Eichhornia crassipes*'s charcoal

### 1.4.1. Volatile matter rate

BS EN 14,774-1 protocol for determination of volatile matter of fuel consists in weighing the dry sample heating under nitrogen, between 890° and 910°C temperature for 7 minutes in a crucible with lid and weigh again. The formula developed by the standard method [18] is used to calculate the volatile matter content:

$$M. O. V. = \frac{((M850^{\circ}\text{C} - M899^{\circ}\text{C}) \times 100)}{M\text{dry}} \quad (3)$$

With: MOV: Volatile matter content, M850°C: Mass obtained after heating to 850°C, M899°C: mass obtained after heating to 899°C

### 1.4.2. Ash content

Ash content is the quantity of very small mineral matter contained in a fuel and released after complete combustion, under the effect of heat at high temperatures. The result is obtained by applying the formula developed by the standard methods [19] and [20]:

$$A(\%) = \frac{(M850^{\circ}\text{C} \times 100)}{M\text{dry}} \quad (4)$$

With: A, M850°C: mass of the powder obtained after incineration at 850°C, M dry: dry mass of the sample.

### 1.4.3. Fixed carbon content

To determine fixed carbon, BS EN 14.774-1 protocol was used. Two parts of combustible briquettes, each weighing 1 gram, were made, then they were introduced into an oven for
calcination. One part was calcined for 10 minutes at 550°C, while other part was calcined for 10 minutes at 850°C. The fixed carbon content developed by the standard method [20] allows to calculate using the following formula:

$$Cf(\%) = 100 - (H_{\text{sec}} + M_{\text{ce}}850^{\circ}\text{C} + M_{\text{v}}550^{\circ}\text{C}) \quad (5)$$

## 1.5. Combustion tests

Combustion test allowed us to determine: Burning time of each combustible briquette; post-combustion mass (ash) and the loss mass.

# 2. RESULTS AND DISCUSSIONS

## 2.1. *Eichhornia crassipes* briquette manufacturing process

### 2.1.1. Preparation of raw material by carbonization

Preparation of *Eichhornia crassipes* raw's material by carbonization gave the following results:

<table><caption>**Table 1:** *Eichhornia crassipes* raw material prepared by carbonization</caption><thead><tr><th>Raw material</th><th>Quantities (gram)</th><th>Binder (0.5mm)</th><th>Particle size (mm)</th></tr></thead><tbody><tr><td>Leaf and branch</td><td>300</td><td rowspan="3">Kaolin clay</td><td>0.5 to 1</td></tr><tr><td>Stem, branch and root</td><td>300</td><td>0.5 to 1</td></tr><tr><td>Stem and branch</td><td>300</td><td>0.5 to 1</td></tr><tr><td>Whole plant</td><td>300</td><td></td><td>0.5 to 1</td></tr></tbody></table>

### 2.1.3. Preparation of raw material semi-decomposition

Preparation of *Eichhornia crassipes* raw's material by semi-decomposition gave, after 14 days, the following results:

<table><caption>**Table 2:** *Eichhornia crassipes* raw material prepared by semi-decomposition</caption><thead><tr><th>Raw material</th><th>Quantities (gram)</th><th>Binder (0.5mm)</th><th>Particle size (mm)</th></tr></thead><tbody><tr><td>Leaf and branch</td><td>500</td><td rowspan="3">Kaolin clay</td><td>0.5 to 1</td></tr><tr><td>Stem, branch and root</td><td>500</td><td>0.5 to 1</td></tr><tr><td>Stem and branch</td><td>500</td><td>0.5 to 1</td></tr><tr><td>Whole plant</td><td>500</td><td></td><td>0.5 to 1</td></tr></tbody></table>

## 4.1 Hygro-calorific characterization of *Eichhornia crassipes*'s charcoal

Clay-bound charred *Eichhornia crassipes* charcoal (98-02%) has a lower calorific value average of 14.67±2.01 MJ/Kg while clay-bound charred *Eichhornia crassipes* charcoal_Wood chips (70-28-02%) has 27.442±5.26 MJ/Kg calorific value average. Among these samples, clay-bound carbonized *Eichhornia crassipes* leaf charcoal (98-02%) has the highest calorific value, 17.656± 0.097 MJ/Kg, while charcoal from carbonized *Eichhornia crassipes* stem bound clay (98-02%) and/or the whole plant of carbonized *Eichhornia crassipes* bound to clay (98-02%) have the same calorific value 13.472 ± 0.012 MJ/Kg. It is found that among *Eichhornia crassipes* carbonized charcoal_Wood chips, charcoal from the leaves of *Eichhornia crassipes* carbonized_woodchips bound with clay (70-28-02%) has the bigger calorific value 33.137± 0.054 MJ/Kg while whole plant charcoal_woodchipClay-bound (70-28-02%) has the smallest calorific value 22.015± 0.017 MJ/Kg.

Charcoal from decomposed *Eichhornia crassipes* bound to clay (98-02%) has an average calorific value 12.755±1.703 MJ/Kg while charcoal from decomposed *Eichhornia crassipes* Chips wood bound to clay (70-28-02%) has a calorific value of 22.895±9.466 MJ/Kg. Among these samples, charcoal from leaves and branches of *Eichhornia crassipes* decomposed _wood chips bound to clay (70-28-02%) has the highest calorific value of 31.336± 0.017 MJ/Kg while charcoal from stems and branch of decomposed *Eichhornia crassipes* bound to clay (98-02%) has the smallest calorific value 11.012± 0.042 MJ/Kg. Overall, it appears that among the charred *Eichhornia crassipes* charcoal briquettes has the highest average calorific value of 21.05±7.76 MJ/Kg while the decomposed *Eichhornia crassipes* charcoal has the lowest average calorific value which is 17.825±8.308 MJ/Kg.

<figure><img src="image_4.png" /><figcaption>**Graph 1:** Calorific value of samples of ecological charcoal based on *Eichhornia crassipes*</figcaption></figure>

These results corroborate those found by [20, 9] who found that charcoal from *Eichhornia crassipes* _wood chips produced greater heat intensity while being cleaner, more convenient and took up less space when stored.

Ecological charcoal made from decomposed *Eichhornia crassipes* has moisture content (4.401±0.972%) while Ecological charcoal made from charred *Eichhornia crassipes* has moisture content of 3.79±1.05%. Charcoal from whole
plant *Eichhornia crassipes* _wood chips has the highest moisture content 5.85±0.12% while charcoal from charred *Eichhornia crassipes* leaves and branches has the lowest moisture content 2.71 ±0.43%. This state of humidity is higher in the briquettes resulting from the semi-

decomposition than those resulting from the carbonization process because carbonized *Eichhornia crassipes* was able to release the excess free water by dry dehydration, during carbonization.

<figure><img src="image_5.png" /><figcaption>**Graph 2:** Plot of moisture content trends against calorific value</figcaption></figure>

There is an inverse relationship between calorific value and moisture content (Graph 2). The plot of the trends of the moisture content of ecological charcoal based on *Eichhornia crassipes* shows that the linear calorific value is ascending when that of the moisture content is descending. Ecological charcoal made by using *Eichhornia crassipes* from the semi-decomposition method has a higher dry moisture content than Ecological charcoal by using *Eichhornia crassipes* from the carbonization method. Overall, following the trend lines, when the humidity increases, it causes a decrease in its calorific value and vice versa. This confirms the results of [22] which indicate that the calorific value is influenced by the moisture content. The range of moisture content in the dry state does not lead to remarkable energy loss during the vaporization of the moisture present and their stability during storage is considerable [23]. Ecological charcoal made from *Eichhornia crassipes* have good characteristic because their dry relative moisture content is between 2.71% and 5.85%, lower than that of wood charcoal 6% [24].

## 4.2 Chemical characterization of *Eichhornia crassipes*'s charcoal

### 4.2.1. Volatile matter content

Ecological charcoal based on carbonized *Eichhornia crassipes* has an volatile matter content average of 26.87±1.55% while that of ecological charcoal based on decomposed *Eichhornia crassipes* is 22.059±1.298%, in accordance with the conclusions of [24], but contrary to those of [25] who insist that woody biomasses have higher levels of volatile matter than other biomasses. Charcoal from clay-bound carbonized *Eichhornia crassipes* stems (98-02%) has the highest volatile matter content of 28.59±0.87%, possibly due to the process of

carbonization of the structure stems of *Eichhornia crassipes* which helps it to retain a high level of volatile matter in the carbonized material, better than by the process of semi-decomposition. Charcoal from the leaves and branches of *Eichhornia crassipes* semi-decomposed_wood chips has the lowest volatile matter content (20.14±0.18%).

### 4.2.2. Ash content

Ash content average of charred *Eichhornia crassipes* charcoal is 2.69±0.33% (with respectively 2.912±0.097% for charred *Eichhornia crassipes* charcoal_woodchips and 2.477±0.343% for charred *Eichhornia crassipes* charcoal), while charcoal from decomposed *Eichhornia crassipes* has 1.972±0.719% ash content (with respectively 2.615±0.2456% for charcoal from *Eichhornia crassipes*_wood chips decomposed and 1.33±0.21% for anthrax from decomposed *Eichhornia crassipes*). Our results, concerning decomposed *Eichhornia crassipes* charcoal, are close to those concluded by [26] which indicate that the ash content of woody biomass is between 0.08% and 2.3%. Decomposed *Eichhornia crassipes* charcoal has a lower average ash content, possibly due to the addition of woodchip (which would be a non-woody vegetable) and clay binder which would act as a filler, thus contributing to a higher ash content and possibly also due to their low carbon binding capacity [27, 9].

### 4.2.3. Fixed carbon content

Carbonized *Eichhornia crassipes* charcoal has a low fixed carbon content (86.73±2.67%) (With 89.035±0.905% for charred *Eichhornia crassipes*_woodchips and 84.43±1.29% for charcoal carbonized *Eichhornia crassipes*) compared to their decomposed counterparts which has 74.496±1.716% (with 73.707±0.444%
for decomposed Eichhornia crassipes charcoal and 75.285±2.241% for Eichhornia crassipes charcoal_woodchips).

<figure><img src="image_6.png" /><figcaption>Graph 3: Chemical characteristics of Eichhornia crassipes fuel samples</figcaption></figure>

### 4.3.6 Combustion/cooking test

Charcoal cooking test of charred *Eichhornia crassipes* with a cooking stove improved made it possible to boil 01 liter of water in 15 minutes 20 seconds and 250 grams of rice in 25 minutes 46 seconds. The average burning time of charred *Eichhornia crassipes* charcoal is 44 minutes 52 seconds with post-combustion mass (ash) of

14.36±0.22 milligrams/Kilogram of Ecological charcoal and an average mass loss of 86.75± 0.01%

charred *Eichhornia crassipes* charcoal Clay bound lasts on average longer in the fire (46 minutes 10 seconds) when burning while decomposed *Eichhornia crassipes* charcoal has a low burn time (43 minutes 33 seconds) (Table 3)

<table><caption>Table 3: Cooking test with samples of Eichhornia crassipes briquettes</caption><thead><tr><td>Samples</td><td>Burning time (s)</td><td>Mass of post-combustion fuel (gr)</td><td>Mass loss (%)</td></tr></thead><tbody><tr><td>Carbonized Eichhornia crassipes charcoal</td><td>2208±3.81</td><td>08.59±0.91</td><td>75±0.5</td></tr><tr><td>Charcoal from Eichhornia crassipes_Charred woodchips</td><td>3276±3.81</td><td>24.85±0.43</td><td>91±0.8</td></tr><tr><td>Decomposed Eichhornia crassipes smut</td><td>2204±1.53</td><td>02.51±0.15</td><td>87±0.3</td></tr><tr><td>Charcoal from Eichhornia crassipes_decomposed woodchips</td><td>2996±4.39</td><td>21.49±0.29</td><td>94±0.9</td></tr></tbody></table>

After 60 minutes of combustion, carbonized Eichhornia crassipes charcoal emits an average of 6.72±1.49 grams of ash with an average mass loss of 93±0.9%, while decomposed Eichhornia

crassipes charcoal emits an average of 12.01±0.09 grams of ash with an average mass loss of 90.05±0.95%.

### Conclusion

The objective of this study was to determine the effect of green charcoal production processes on their performance as cooking energy. Overall, it appears that carbonized *Eichhornia crassipes* charcoal briquettes perform better than decomposed *Eichhornia crassipes* charcoal briquettes. Indeed, on the hygro-calorific level, ecological coal based on decomposed *Eichhornia crassipes* has a moisture content of 4.401 ± 0.972% with a low calorific value average (17.825 ± 8.308 MJ / Kg) while ecological coal based of carbonized *Eichhornia crassipes* has a low moisture content of 3.79±1.05% with a high average calorific value of 21.05±7.76MJ/Kg.

Chemical characterization show that the ecological charcoal based on charred *Eichhornia crassipes* has volatile matter average rate (26.87±1.55%) and low fixed carbon average (86.73±2.67%) and ash content average (2.69 ± 0.33%) while ecological charcoal based on decomposed *Eichhornia crassipes* has volatile matter content average (22.059 ± 1.298%), and fixed carbon content average (74.496 ± 1.716%) and ash content average (1.97 ±0.72%).

In terms of improved cook stove applicability, charred *Eichhornia crassipes* charcoal bounded to clay lasts on average longer in the fire (46 minutes 10 seconds) during combustion emitting an average of 6.72±1, 49 grams of ash with an average mass loss of 93.02±0.91% while decomposed *Eichhornia crassipes* charcoal has a
low burn time (43 minutes 33 seconds), emitting an average of 12.01±0.09 grams of ash with an average mass loss of 90.05 ± 0.95%. From the point of view of cooking energy, charred *Eichhornia crassipes* charcoal_woodchip bound with clay has a better efficiency in the stove. In the case where one would like to proceed by decomposition of the biomass, the decomposed *Eichhornia crassipes* charcoal_woodchips and bound to the clay would be just as interesting.

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