To meet the ever-increasing electricity needs of its population, Cote d'Ivoire regularly invests in production infrastructure. Thus, its electricity production capacity has increased from 1391 MW in 2010 to 2214 MW in 2019. These electricity facilities are mainly composed of thermal and hydroelectric power plants. Thermal power plants, whose contribution to the electricity mix is estimated at 67% in 2019, remain dependent
With the aim of increasing its production capacity, the country plans to introduce renewable energies into electricity production. This desire is expressed through an action plan, the implementation of which should make it possible to achieve a contribution of 42% of these energies in the energy mix by 2030. The estimated amount for the implementation of this plan for the period 2021-2030 is approximately USD 1,549.91 million. This amount should enable the realisation of several projects developed by the ministry in charge of the country's energy resources. These projects include the construction and operation of six biomass power plants for a total of USD 425.2 million
However, the present study evaluates the environmental performance of cocoa pod husk used as fuel for a biomass power plant. In a previous study, Zinla et al.
For the environmental assessment, the study calculates the environmental impacts of the electricity generation process using cocoa pod husk. According to Chauhan et al.
According to these authors, life cycle assessment (LCA) is a comprehensive method to assess the environmental performance of a biofuel. For Chauhan et al.
In this study, we use LCA to assess the global warming potential of electricity production from a biomass power plant using cocoa pod husk in Côte d'Ivoire. Greenhouse gas emissions of this electricity production are compared with those of other energy sources. The environmental analysis is important to define a better framework for technological investments for the energy valorization of Ivorian cocoa pod husk. The findings will provide guidance for the development of biomass thermal power plants using cocoa pod husk for electricity generation in Côte d'Ivoire.
LCA is an iterative method structured around a functional unit. It is generally conducted in four stages: definition of objectives and scope, inventory analysis, impact assessment, and interpretation of results. These are both distinct and interdependent
This study conducts a life cycle assessment of electricity generation from a biomass power plant using cocoa pod husk in Côte d'Ivoire. It assesses the environmental performance of cocoa pod husk and compares it to other energy sources used for electricity production. Thus, the objectives of the study are: (a) to calculate the environmental impact of electricity production using cocoa pod husk, (b) to compare the environmental performance of cocoa pod husk with that of renewable and conventional sources of electricity production and (c) to analyse the sensitivity of the parameter that most affects the life cycle emissions of cocoa pod husk.
The functional unit used in this study is 1 kWh of electricity produced by the different energy sources. This functional unit is used in most LCA studies of electricity generation
If the boundaries are set too narrowly, some important impacts may not be detected; conversely, if they are set too broadly, other impacts than those of interest may be included
The process boundaries of this study start from the process of producing the mature cocoa pods from the cocoa farm to the process of burning the dry cocoa pod husk in the biomass boiler of the power plant. Thus, the boundaries of the power generation process include: the production of the mature cocoa pods (The establishment of cocoa farms is not taken into account in this step), the collection of the cocoa pod husk, the transportation of the cocoa pod husk, and the combustion of the cocoa pod husk. These different processes can be grouped into two main steps, namely, biomass preparation and cocoa pod husk burning. Biomass preparation includes: the process of producing mature cocoa pods, and the collection and transport of cocoa pod husk.
The study is carried out in the Bas-Sassandra district located on the southwest coast of Côte d'Ivoire. This district covers an area of 2,095 km2. It includes the regions of San-Pedro, Gbôklè and Nawa.
The production of mature cocoa pods require the use of fertilisers and pesticides. Data on fertilisers and pesticides come from CNRA (Centre National de Recherche Agronomique) literature
The collection of cocoa pod husk in this study consists of conveying the dry cocoa pod husk in bulk from the plantations to the local collection centre, located near the village. Each village that produces dry cocoa beans will have a collection centre. The collection process requires the use of light vehicles. In general, in the district, the vehicles used to transport agricultural products from the farms to the village have a capacity of 3 tons per load. Thus, the vehicles used for the collection of dry cocoa pod husk are tractor-trailers with a capacity of 3 tonnes per load. The maximum distance between the collection centre and the cocoa farms is estimated at 10 km. In general, in the district, the furthest cocoa fields are located about 10 km from the village.
The cocoa pod husk is then transported from the local collection centre to the thermal power plant. The trucks used for transport have a loading capacity of 20 tonnes. For economic reasons and availability of residues, the study assumes that the power plant is located in the department of Soubré. This department is the heart of the new cocoa loop in Côte d'Ivoire. Soubré's cocoa production represents 59% of the cocoa production of the Bas-Sassandra district
Departements |
Transport (km) |
San-Pedro |
133 |
Tabou |
229 |
Buyo |
84 |
Méagui |
52 |
Gueyo |
67 |
Sassandra |
161 |
Fresco |
223 |
According to the study by Shafie et al.
Electricity generation using cocoa pod husk is a new system in Côte d'Ivoire. The country does not currently have a biomass power plant using cocoa pod husk. This means that data sources are limited. Therefore, data on boiler emissions are taken from the USEPA report. The emission factors taken in this reference are those for dry wood burning in a biomass boiler.
The electrical power produced by the cocoa cortex is calculated from equation 1
P = (m x η x LHV) / (3.6 x T) (1)
m: Amount of crop residue used to produce 1kWh of electricity in kg ;
P: Electrical power produced by the biomass power plant in MW;
T: Operating time of the thermal power plant in hours;
LHV: Lower heating value of crop residue in MJ/kg.
An environmental impact is understood as a change in the environment, whether beneficial or detrimental, due to a human activity. This change can cover very different environmental aspects. In LCA, these different aspects are called impact categories
There are no standard methods for assessing environmental impact categories
To assess the environmental impacts of bioenergy, the majority of LCA studies have used the midpoint impact categories of the CML method
Of the eight impact categories of the CML-baseline, only four categories considered to be very robust for the purposes of this study were taken into account.
Particulates emitted |
NOx |
CO |
|
VOC |
|
Particulate matter |
Emission factors (g/kWh) |
0.76 |
0.93 |
0.039 |
0.06 |
1750.03 |
0.62 |
Region |
Departement |
Cocoa beans (Tonnes) |
Cocoa podhusk (Tonnes) |
Energy potential (MW) |
San-Pedro |
Tabou |
171164 |
231071.4 |
20.62 |
San-Pedro |
||||
Nawa |
Soubré |
272265 |
367557.75 |
32.78 |
Buyo |
||||
Méagui |
||||
Gueyo |
||||
Gbôklè |
Sassandra |
21426 |
28925.1 |
2.58 |
Fresco |
Environmental impact category |
Relevant emissions |
Unit |
Acidification |
Sulfurdioxide |
kg |
|
Nitrogen oxides NOx |
|
|
Hydrochloricacid HCL |
|
|
Hydrofluoricacid HF |
|
|
Ammonia |
|
Eutrophication |
Phosphate |
kg |
|
Nitrogen oxides NOx |
|
|
Nitrogen |
|
|
Nitrates |
|
|
Ammonia |
|
Toxicity |
Arsenic |
kg 1,4- DB équivalents |
|
Chromiumequivalents VI |
|
|
Benzene |
|
|
Hexachlorobenzene |
|
Climate change |
Carbon dioxide |
kg |
|
Nitrous oxide |
|
|
Methane CH4 |
|
|
Chlorofluorocarbon CFC |
|
|
Hydrochlorofluorocarbon HCFC |
|
These results reveal that electricity production using cocoa pod husk in the Bas-Sassandra district is accompanied by emissions of environmental pollutants involving climate change, acidification, eutrophication, and human toxicity.
The acidification is attributable to the emission of about 1.12 g
Human toxicity is attributable to the emission of approximately 9.91 g 1,4 DBeq/kWh of electricity. This impact is implied by the pollutants emitted during the collection, transport and combustion processes of the cocoa pod husk. The contribution of collection to toxicity is about 27%; that of combustion is about 30%. Electricity generation using rice straw in Malaysia emits about 1.41 g 1,4DB/kWh of electricity
Finally, the process using cocoa pod husk in Côte d'Ivoire emits about 328.22 g
Environmental impacts |
Values |
Units |
Eutrophication |
28 10-2 |
g |
Climate change |
328.22 |
g |
Toxicity |
9.91 |
g 1,4 DB équivalent |
Acidification |
11.2 10-1 |
g |
In order to take into account possible changes in the fuel supply circuit of the thermal plant, the study proposes to vary the transport distances in a sensitivity study to see their effects on the greenhouse gas emissions of the process.
The second unit can be installed in San-Pedro, and supplied with fuel from the departments of Tabou, Sassandra and San-Pedro. The maximum transport distance in this case is 100 km for a maximum GHG emission of 328.22 g
The environmental impacts of the electricity generation process using cocoa cortex in the Bas-Sassandra district of Côte d'Ivoire were calculated for the processes of cocoa pod production, collection, transport and combustion of the cocoa pod husk to produce 1 kWh of electricity. This electricity production is accompanied by emissions of pollutants involving acidification, eutrophication, global warming and human toxicity.
Acidification is implied by the emission of 1.12 g
The sensitivity analysis showed that the transport distance has an effect on the GHG emissions of the sector. Thus, GHG emissions increase with the distance travelled by the transport vehicle. The analysis identified power plant locations that would reduce GHG emissions for the production of 1 kWh of electricity.