Potential of Renewable Energy in Jamaica’s Power Sector: Feasibility Analysis of Biogas Production for Electricity Generation

Abstract

Jamaica is heavily dependent on fossil fuels to meet its energy demand and is currently seeking to reduce consumption. Accordingly, it is essential to investigate the expansion of renewable energy systems to achieve its 2030 renewable energy goal of 50%, with 70% diversification in energy types, as outlined in the National Energy Policy 2009–2030. This study explores biogas feasibility in Jamaica and discusses the potential for electricity generation from combinations of dairy cow and Swine feces with sugarcane bagasse. The study’s primary purpose is to assess the feasibility of biogas production from livestock manure and sugarcane bagasse for electricity generation and manure treatment. Findings reveal that biogas anaerobic digestion and the co-digestion of different varieties of animal manure with sugarcane bagasse can generate up to 122,607.68 MWh or 2.49% of Jamaica’s total electrical energy generation in 2019. The findings indicate a high potential for the installation of community-based plants. Moreover, considering all scenarios and the remaining feedstock, potential electrical energy increases to 222,868.60 MWh (4.53% of total energy generation). This power may be fed to the electrical grid network or consumed by local producers. In addition, electric power generation from animal manure and sugarcane bagasse is feasible with improved technical capability and human development. Additionally, anaerobic digestion and co-digestion of sugarcane bagasse plus animal manure offer an excellent solution to mitigate climate change.

1. Introduction

The energy sector in all economies embodies an essential constituent of national stability since it is a crucial input to producing goods and services which are fundamental to social and economic development. Increasingly, renewable energy (RE) is gaining greater importance as countries seek to transition from consuming large amounts of fossil fuel to energy systems that mitigate climate change. Jamaica is strategically seeking to reduce its dependence on imported petroleum by diversifying while modernizing its energy systems to include environmentally sustainable green forms of energy as outlined in its Vision 2030 National Development Plan (NDP) [1], thus shifting resources to facilitate the increased production of renewable energy technologies.

Currently, Jamaica depends heavily on petroleum imports to meet its energy requirements since it lacks fossil fuel deposits. At least 93% of the population has access to electricity supported by petroleum. Nevertheless, the island faces an increasing demand for fuel and the scarcity of financial resources to cover an increased oil bill, limiting energy security since approximately 9 to 11% of its gross domestic product covers oil imports [2].

As a result, the benefits of transitioning from fossil fuels toward renewables extend beyond increased energy security. Comparative cost assessments show that, by 2030, Jamaica can save up to USD 12.5 billion in energy system expenditure [3]. Accordingly, the negative environmental and economic repercussions demand a shift from fossil fuels to varying RE options. The share of RE sources in Jamaica has increased from 9% in 2009 to 19% in 2020, as shown in Figure 1. This energy is derived from renewable sources such as wind, mini-hydro, biomass, and solar power. Nonetheless, the government of Jamaica seeks to reduce energy imports from 81% to 50% by 2030, as cited by the Ministry of Energy and Mining [4], the Prime Minister’s Office [5], and the International Renewable Energy Agency (IRENA), 2021, in ENERGY PROFILE Jamaica (Figure 1) [6].

The ambitious goals mentioned above ought to be achieved by increasing energy-from-waste initiatives, including but not limited to the increased recycling of organic wastes through biogasification.

Thus, assessing the available organics is an essential starting point. Comparing the list of typical energy crops with those found in the all-island crop production (Figure 2), sugarcane is the most suitable energy generation. Additionally, animal manure is readily available, and their collection factors, ratio of volatile solids, and biogas generation rates are relatively high. These feedstocks have proven to be effective in biogas production. Moreover, using these sources serves multiple functions: reviving a fledgling sugar industry, promoting biomass waste-to-energy recovery, properly disposing of animal manure and bagasse, and greenhouse gas (GHG) emission reduction.

Not many studies focus on electricity cogeneration from bagasse plus biogas generation from livestock manure in Jamaica. Notable studies were conducted by Contreras-Lisperguer et al., 2018 [7], and Grant, S., and Marshalleck, A., 2008 [8]. Thus, further research is warranted to expand the research on the subject. There is also the availability of food and green wastes (for example, kitchen waste, fruit, vegetable, oil, and yard waste) for assessing biogas production. Compared to other organic substrates, these waste types supply a more significant carbon-to-nitrogen ratio (C/N) based on physical analysis and elemental compositions. In particular, animal manures have lower C/N ratios ranging from 10.6 to 15.8 compared to kitchen waste (20.3) and yard waste (25.9), as mentioned by Li et al., 2013 [9]. Nevertheless, this study utilizes sugarcane bagasse and livestock manure as feedstock because of data availability.

Another drawback is that, in Jamaica, organic wastes from households (kitchen, yard, fruit, and vegetable wastes) are not sorted from other wastes, as the country lacks stringent rules of waste separation. With a solid waste system that mixes organics and inorganics at the disposal stage, waste characterization and collection are complex, especially for aggregate estimation without contamination. However, further study is needed to investigate how these waste resources can generate energy to help meet the country’s 2030 renewable energy goal of 50%. Furthermore, energy-from-waste offers a solution for reviving a struggling sugar industry while mitigating climate change by improving livestock waste management.

The study’s objectives are to assess the availability of waste materials (different varieties of livestock manure and sugarcane bagasse) to produce biogas for electric power generation and to calculate the amount of electrical energy obtained from the selected waste resources. The focus is on utilizing sugarcane bagasse under anaerobic fermentation in single- and co-digestive states with animal manure at different ratios for energy utilization. The study’s primary purpose is to estimate the potential of biogas generation from animal manure and sugarcane bagasse, then to assess the possibility of electricity generation plus the contribution to the 20% diversification to renewable energy sources as outlined in the National Renewable Energy Policy [10], as well as to propose treatment for animal manure. The hypothesis is that the fermentation and co-fermentation processes of livestock manure and sugarcane bagasse are feasible and that methane production reaches a viable quantity to warrant increased numbers of biogas plants. It is technically and environmentally achievable to use the selected feedstock for biogas creation.

Figure 2. Crop availability (tons) in Jamaica from 2008 to 2017. The figure indicates nine different categories characterized by the Agricultural Marketing Information Division of the Ministry of Industry, Commerce, Agriculture, and Fisheries (MICAF, 2017). Refer to Appendix A for details. Source: [11].

Figure 2. Crop availability (tons) in Jamaica from 2008 to 2017. The figure indicates nine different categories characterized by the Agricultural Marketing Information Division of the Ministry of Industry, Commerce, Agriculture, and Fisheries (MICAF, 2017). Refer to Appendix A for details. Source: [11].

2. Study Area and Data

2.1. Study Area

Jamaica is a small island nation located in the Caribbean Sea with 2.98 million people. The island has 14 parishes (Figure 3). Most of the land, except for areas within the metropolis, is used for agriculture. An abundance of food is grown, and plenty of animals are reared to partially meet the demand of the population’s food supply; as a result, over 65% of the total municipal wastes are organic wastes, including agricultural crop waste, plus food and green wastes, which end up in landfill sites [12]. This waste stream, including sugarcane bagasse, is a valuable renewable energy source if appropriated well.

2.2. Bioenergy Utilization in Jamaica

In Jamaica, by 2009, 81% of the total renewable energy came from biomass, fuelwood, and sugarcane bagasse burning for heat and energy generation [14]. An estimated 11% to 15% of Jamaican homes depended on charcoal and fuelwood for cooking. Evidence suggests that residues from crop production are available for bioenergy generation, as outlined in the Worldwatch report in 2015, as shown in Table 1, the National Energy Policy 2009–2030 (NEP) [15], and Biofuels Policy (2010–2030) [16]. Nevertheless, this research focuses on using sugarcane bagasse with dairy cows and swine dung to produce biogas.

Despite technological progress in the energy industry, 45% of the world’s population, including those in some parts of Jamaica, continue to obtain their household energy from traditional energy sources, such as fuelwood, charcoal, crop, and animal residues, which contribute to human health problems [17].

Table 1. Proven RE potential (MW) and current utilization.

Renewable Energy Source	Proven RE Potential (MW)	Potential Being Utilized (%)	Estimated Installed Capacity (MW) (Up to 2020)
Solar	650–1876	5	93
Biomass	192	0	32
Waste-to-Energy	65–127	5	5 (3.25% from bagasse)
Hydro	33.4–56.1	57	31.92
Wind	112–1313	7.78	99
Geothermal	Minimal potential	0	0
Total	-	-	260.92
Renewable energy as % installed power capacity = approximately 19%

Current and potential renewable energy amounts by renewable energy types. Source: [18,19].

Table 1. Proven RE potential (MW) and current utilization.

Renewable Energy Source	Proven RE Potential (MW)	Potential Being Utilized (%)	Estimated Installed Capacity (MW) (Up to 2020)
Solar	650–1876	5	93
Biomass	192	0	32
Waste-to-Energy	65–127	5	5 (3.25% from bagasse)
Hydro	33.4–56.1	57	31.92
Wind	112–1313	7.78	99
Geothermal	Minimal potential	0	0
Total	-	-	260.92
Renewable energy as % installed power capacity = approximately 19%

Current and potential renewable energy amounts by renewable energy types. Source: [18,19].

2.3. Anaerobic Digestion and Biogas

Anaerobic digestion (AD) offers a dual solution for mitigating CO₂ emissions and meeting energy demands and waste management, nutrient recycling, renewable energy production, etcetera. AD involves a series of processes within which microorganisms break down biodegradable material without oxygen. Moreover, the process produces biogas, primarily methane and CO₂ [20]. Biogas can be produced from the AD process and converted to electrical energy for on or off-grid use. Moreover, biogas is available for transportation fuel (after it is upgraded to biomethane), cooking, and for generating heat.

Carbon and nitrogen in the AD process are essential for microbial cell growth. Researchers, including Khanal et al., 2019 [21] and Radhakrishnan and Sugumaran, 2010 [22], have pointed to the importance of having nitrogen and carbon feedstocks since a combination directly impacts residue decomposition, affecting microbial cell growth. While some agricultural wastes are rich in carbon and livestock waste is rich in nitrogen, balancing the carbon-nitrogen (C/N) ratio during co-digestion improves biogas yields. Bagasse is the fibrous material left over after the juice is extracted from sugarcane. It contains roughly 50% cellulose (carbon), 25% lignin, and 25% hemicellulose and is used in many processes, such as biogasification and building materials [23]. The high cellulose content makes it appropriate for biogasification, since the process yields copious amounts of CH₄ gas, which is necessary for electrical energy generation.

Biogas production provides an effective ecological solution to recycling and reusing wastes cost-effectively [24,25]. The process allows some organic wastes to generate RE, including agricultural waste, food waste, sewage sludge, animal manure [8,25,26,27], and organic industrial and municipal waste. Often-used agricultural waste includes rice straw, sugarcane bagasse, wheat straw, maize stalk, and lentil straw [28,29,30]. Several of these bio-crops are a part of Jamaica’s staple diet, with sugarcane production dominating the total crop production output, as shown in the all-island crop production data from 2008 to 2017 (Figure 2).

Biogasification is not new to Jamaica since it started in the 1980s. By 2016, approximately 60 small- and medium-size biodigester systems, namely up-flow anaerobic sludge blankets (UASB) and 107 biodigester septic tanks (BST), were in operation [31]. However, increased use of the technology, especially commercially, can aid in the revival of the struggling sugar industry while promoting the government’s energy-from-waste plan outlined in the NEP [10].

3. Materials and Methods

Several kinds of research are done to cogenerate power from different types of waste. Combining agri-waste with animal excrement yields considerable amounts of biogas energy suitable for commercial purposes [32]. Figure 4 shows the proposed system for biogas production using bagasse and animal excrement as feedstock. In the case of Jamaica, natural sources are available for energy delivery. Thus, quantitative assessments of the total available residue for biogas are essential. The process of deriving the total electrical energy to be derived from biogasification is expressed below:

• Secondary data collection of available residues from agricultural and livestock manures was collated to assess the appropriate feedstock for analysis.
• A comprehensive literature review looked at similar studies and an array of relevant country policy papers.
• Quantification of the agricultural and livestock residues was performed through data assimilation. The works applied are listed in this section.
• The data was computed in Microsoft Excel software, with findings centered on specific distinguishing factors from residue types.
• Finally, a brief conclusion was drawn to estimate available bioresources for energy application.

After that, the potential biogas output was calculated based on feedstock availability. For example, feedstock collection coefficients of animal manures and sugarcane bagasse are given in Table 2 and Table 3, where the biogas generation rates are also available. The total potential biogas is then converted to electrical energy by utilizing similar coefficients found in the works of Banks 2009 [33], Qiu et al., 2014 [34], and Suhartini et al., 2019 [35].

3.1. Assumptions

Digestion and co-digestion for biogas production are natural processes that require little external energy throughout the generation process, and the raw materials needed are renewable. Animal excrement and sugarcane bagasse are available materials, making biogas energy a sustainable alternative to petroleum, considering the overall input costs.

3.2. Data Collection

The data employed consists of information gathered from the Ministry of Water, Land, Environment, and Climate Change; Ministry of Industry, Commerce, Agriculture, and Fisheries; Meteorological Service Division in the Ministry of Economic Growth and Job Creation; Ministry of Science, Technology, Energy, and Mining; and the United States Department of Agriculture.

3.3. Quantitative Assessment of Agricultural and Livestock Residues’ Energy-from-Waste Potential

The research examines the current agricultural wastes available on the island for biogas production by gathering statistical data from the Ministry of Industry, Commerce, Agriculture, and Fisheries (MICAF) and the USDA Foreign Agricultural Services: Global Agricultural Information Network, Office of Agricultural Affairs. Agricultural wastes generally include all organic materials, which are by-products from the harvesting and processing of crops. Here, it refers to sugarcane waste (sugarcane bagasse), while animal waste or manure refers to livestock waste.

The quantitative method used to estimate available residue for biogas energy generation is adopted and modified from the studies of Suhartini et al., 2019 [35], and Rahman, M. M., and Paatero, J. V., 2012 [36]. The relevant equations are delineated below. Bagasse availability for energy production:

$${\mathrm{R}}_{\mathrm{c}}=\mathrm{P}{\ast \mathrm{Y}}_{\mathrm{c}}$$

(1)

where ${\mathrm{R}}_{\mathrm{c}}$ (kg ${\mathrm{d}}^{-1}$) is the total crop residue where P (kg${\mathrm{d}}^{-1}$) is daily crop production, and ${\mathrm{Y}}_{\mathrm{c}}$ is crop residue to yield mass ratio.

$${\mathrm{A}}_{\mathrm{c}}={\mathrm{R}}_{\mathrm{c}} \ast {\mathrm{C}}_{\mathrm{c}}{\ast \mathrm{S}}_{\mathrm{c}}{ \ast \mathrm{D}}_{\mathrm{c}}$$

(2)

Here, ${\mathrm{A}}_{\mathrm{c}}$ (kg ${\mathrm{d}}^{-1}$) is the available crop residue for biogas generation where ${\mathrm{C}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue) is residue collection factor, ${\mathrm{S}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue) is surplus availability factor and ${\mathrm{D}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue) is the residue dryness factor.

$${\mathrm{B}}_{\mathrm{c}}={\mathrm{A}}_{\mathrm{c}} \ast {\mathrm{V}}_{\mathrm{c}} \ast {\mathrm{G}}_{\mathrm{c}}$$

(3)

where ${\mathrm{B}}_{\mathrm{c}}$ is total biogas potential from sugarcane bagasse residue (${\mathrm{m}}^3{\mathrm{d}}^{-1}$), ${\mathrm{V}}_{\mathrm{c}}$% is the ratio of volatile solid (VS) to dry matter, and ${\mathrm{G}}_{\mathrm{c}}$ (${\mathrm{m}}^3{\mathrm{kg}}^{-1}$) of residue is the rate of biogas generation from VS. For the computation of accessible livestock residue, surplus availability and residue dryness factors are excluded, as with previous successful research.

$${\mathrm{R}}_{\mathrm{L}}=\mathrm{N}{\ast \mathrm{Y}}_{\mathrm{L}}$$

(4)

where${\mathrm{R}}_{\mathrm{L}}$ is the total residue from each livestock (kg ${\mathrm{d}}^{-1}$), N is the number of livestock (unit), and ${\mathrm{Y}}_{\mathrm{L}}$ (kg ${\mathrm{d}}^{-1}$) is the (dry matter) residue generation rate.

$${\mathrm{A}}_{\mathrm{L}}={\mathrm{R}}_{\mathrm{L}} \ast {\mathrm{C}}_{\mathrm{L}}$$

(5)

where ${\mathrm{A}}_{\mathrm{L}}$ (kg ${\mathrm{d}}^{-1}$) is total available livestock residue, ${\mathrm{C}}_{\mathrm{L}}$ (kg kg ${\mathrm{d}}^{-1}$) is the residue collection factor.

$${\mathrm{B}}_{\mathrm{L}}={\mathrm{A}}_{\mathrm{L}}{ \ast \mathrm{V}}_{\mathrm{L}}{ \ast \mathrm{G}}_{\mathrm{L}}$$

(6)

where ${\mathrm{B}}_{\mathrm{L}}$ (${\mathrm{m}}^3{\mathrm{d}}^{-1}$) is the biogas potential from livestock residues, ${\mathrm{A}}_{\mathrm{L}}$ (kg ${\mathrm{d}}^{-1}$) is total available livestock residue, ${\mathrm{V}}_{\mathrm{L}}$(VS) is the ratio of VS to dry matter, and ${\mathrm{G}}_{\mathrm{L}}\left({\mathrm{m}}^3{\mathrm{kg}}^{-1}\right)$is the rate of biogas generation from VS.

Several factors are considered when generating biogas, including retention time, substrate type and availability, temperature, pH, residue to yield mass ratio, collection factor, residue dryness ratio of volatile solids, and surplus availability factor, as outlined in Table 2 and Table 3. These vary depending on the study, research condition, pretreatment, substrate content (livestock and crop species), and environmental conditions, such as temperature, retention time, and pH values [27,28,32,37,38].

Equations (1)–(6) have been adopted from the work of Rahman and Paatero in 2012 [36], utilizing highlighted values from Table 2, Table 3 and Table 4. Slight amendments were made for the adaptation to the study site. For example, to derive potential biogas energy generated from sugarcane bagasse by finding the total crop residue, ${\mathrm{A}}_{\mathrm{c}}$. From Equation (2), ${\mathrm{R}}_{\mathrm{c}}$ (kg ${\mathrm{d}}^{-1}$) is the total crop residue, ${\mathrm{C}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue) residue collection factor, ${\mathrm{S}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue) surplus availability factor, and residue dryness factor ${\mathrm{D}}_{\mathrm{c}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$of residue). The theoretical biogas potential ${\mathrm{B}}_{\mathrm{c}}$is computed by multiplying three variables, i.e., available crop residue ${\mathrm{A}}_{\mathrm{c}}$ (kg ${\mathrm{d}}^{-1}$), the ratio of volatile solids to dry matter ${\mathrm{V}}_{\mathrm{c}}$, and ${\mathrm{G}}_{\mathrm{c}}—$the rate of biogas generation from volatile solids (VS).

The potential amount generated is assumed to be from 300 days since the plant will be operational for 300 days per year. As for the methane content in biogas from bagasse, the study used the research findings from Kwaku Armah et al., 2020 [39], which established 60% as the average methane output. Likewise, Tuesorn et al. [40] and Sthembiso, M., and Makarfi, I.Y., 2020 [41] have confirmed higher methane production in the co-fermentation of sugarcane bagasse with swine manure (68%) and in dairy cow manure (80%). Similarly, research by Rangkuti et al., 2006 [42], and Lansing et al., 2010 [43] have verified average methane generation of 61.7% and 69.9% in biogas generation from dairy cow dung and swine manure substrates, respectively. Finally, the CH4 output is converted to kWh by multiplying the biogas potential times methane output times 10.5, which is the electric energy conversion rate. The calculation procedure is similar for livestock and mixtures of crops and manure.

AD is a technique employed in quantitative methods to transfigure residues to biogas. These calculations do not use the temperature, retention time, and pH values, since they are already used to derive the biogas generation rate referenced in previous studies given in Table 2 and Table 3. Moreover, the final calculations of dairy cow and swine manure availability only consider medium- to large-scale farms of ≥500 animals per head, as defined in this study. Nonetheless, since no historical research has listed the values and calculative approach in Jamaica, a wide range of literature was examined and then appropriated.

Electrical energy conversion efficiency fluctuates for biogas, ranging from 30 to 40% [33,36]. Thus, the study uses the midrange value of 35%. The plant operation capacity is 300 days per annum, which computes potential energy capacity [33,35].

In the case of co-digestion, the potential biogas calculation is similar to the previous cases:

$$\mathrm{BP}={\mathrm{A}}_{\mathrm{r}} \ast {\mathrm{V}}_{\mathrm{r}} \ast {\mathrm{G}}_{\mathrm{r}}$$

(7)

where BP is the normalized biogas generation rate from the total available residue of substrates presented as 2.14 in the work of Suhartini et al. [35], ${\mathrm{A}}_{\mathrm{r}}$ (${\mathrm{kg}\mathrm{kg}}^{-1}$) is the entire available residue, ${\mathrm{V}}_{\mathrm{r}}$ (kg ${\mathrm{d}}^{-1}$) is the ratio of volatile solids from substrates, and ${\mathrm{G}}_{\mathrm{r}}\left({\mathrm{m}}^3{\mathrm{kg}}^{-1}\mathrm{of}\mathrm{volatile}\mathrm{solids}\right)$represents the rate of biogas generation. The theoretical BP is calculated in Table 4 using values from Surendra et al., 2014 [20], Bhattacharya et al., 1997 [25], Afrizal et al., 2017 [26], and Suhartini et al., 2019 [35].

Table 2. Factors used to estimate agricultural residue availability.

Agricultural Residue	Collection Factor	Surplus Availability Factor	Residue Dryness Factor	Ratio of Volatile Solid	Biogas Generation Rate	References
Unit	0–1	0–1	0–1	0–1	m3/kgVS
Rice straws	0.60	0.50	0.83	0.54	0.34	[30,38,44,45]
Rice husk	0.80	0.46	0.876	0.69	0.69	[30,35,44,45,46]
Rice bran	1.00	0.68	0.91	0.69	0.50	[30,35,45,47,48]
Jute stalks	0.35	0.50	0.905	0.50	0.30	[30,45]
Sugarcane tops	0.70	1.00	0.50	0.50	0.37	[30,38,45]
Wheat straws	0.35	0.20	0.925	0.94	0.36	[30,35,45,46]
Sugarcane bagasse	1.00	0.21	0.51	0.74	0.37	[30,35,45,46]

Source: detailed values are derived from the listed references provided in the table.

Table 2. Factors used to estimate agricultural residue availability.

Agricultural Residue	Collection Factor	Surplus Availability Factor	Residue Dryness Factor	Ratio of Volatile Solid	Biogas Generation Rate	References
Unit	0–1	0–1	0–1	0–1	m3/kgVS
Rice straws	0.60	0.50	0.83	0.54	0.34	[30,38,44,45]
Rice husk	0.80	0.46	0.876	0.69	0.69	[30,35,44,45,46]
Rice bran	1.00	0.68	0.91	0.69	0.50	[30,35,45,47,48]
Jute stalks	0.35	0.50	0.905	0.50	0.30	[30,45]
Sugarcane tops	0.70	1.00	0.50	0.50	0.37	[30,38,45]
Wheat straws	0.35	0.20	0.925	0.94	0.36	[30,35,45,46]
Sugarcane bagasse	1.00	0.21	0.51	0.74	0.37	[30,35,45,46]

Source: detailed values are derived from the listed references provided in the table.

Table 3. Factors used to estimate livestock residue availability.

Livestock Type	Collection Factor	Ratio of Volatile Solid to Dry Matter	Biogas Generation Rate	References
Unit	0–1	0–1	m3/kgVS
Poultry	0.50	0.46	0.18	[25,35,45]
Sheep	0.60	0.91	0.31	[25,33,45]
Goat	0.60	0.59	0.31	[25,38,45]
Swine	0.50	0.89	0.65	[40]
Dairy cow	0.50	0.93	0.66	[25,26,38,45]

Source: detailed values are derived from the listed references provided in the table.

Table 3. Factors used to estimate livestock residue availability.

Livestock Type	Collection Factor	Ratio of Volatile Solid to Dry Matter	Biogas Generation Rate	References
Unit	0–1	0–1	m3/kgVS
Poultry	0.50	0.46	0.18	[25,35,45]
Sheep	0.60	0.91	0.31	[25,33,45]
Goat	0.60	0.59	0.31	[25,38,45]
Swine	0.50	0.89	0.65	[40]
Dairy cow	0.50	0.93	0.66	[25,26,38,45]

Source: detailed values are derived from the listed references provided in the table.

Table 4. Factors used to estimate residue availability for the co-digestion AD biogas process.

Livestock Type	Residue Generation Rate	Collection Factor	Ratio of Volatile Solid to Dry Matter	Biogas Generation Rate	References
Unit	kg dry matter/day	-	-	m3/kgVS
Sugarcane bagasse and Swine	-	0.90	0.71	0.89	[20,25,40]
Sugarcane bagasse and dairy cow	-	0.75	0.80	0.92	[26,41]

Source: derived from sources in the references of the table [20,25,26].

Table 4. Factors used to estimate residue availability for the co-digestion AD biogas process.

Livestock Type	Residue Generation Rate	Collection Factor	Ratio of Volatile Solid to Dry Matter	Biogas Generation Rate	References
Unit	kg dry matter/day	-	-	m3/kgVS
Sugarcane bagasse and Swine	-	0.90	0.71	0.89	[20,25,40]
Sugarcane bagasse and dairy cow	-	0.75	0.80	0.92	[26,41]

Source: derived from sources in the references of the table [20,25,26].

Livestock residue availability uses data from 2016, based on accessibility. While livestock types have strict definitions [49], several studies have classified farm sizes with different variations, including Venier and Yabar in 2017, that used ≥500 animals per head as mid-to-large size farms [49,50,51,52,53,54,55,56,57]. Therefore, it is postulated that farm size is dependent on the production system within a country. The approach finds that previous research yielded positive findings in generating biogas from varying combinations of sugarcane bagasse with dairy cow and swine manure, for example, in the work of Afrizal et al., 2017 [26]; Mashi, B. H., 2018 [27]; and Tuesorn et al., 2013 [40].

4. Findings and Discussion

The results indicate a high potential for installing small-scale biogas plants in parishes with a consistently high amount of feedstock from the six sugar factories and 54 swine and dairy cow farms (with ≥500 animals per head). Findings indicate that the biogas potential is 4.92 million m³ per year when dairy cow dung is fermented and 9.34 million m³ per year from the fermentation of swine manure. The combined use of dairy cow and swine dung and sugarcane bagasse can respectively yield 18.89 and 10.81 million m³ of biogas per year. The theoretical potential of generating electricity ranges from 22,139.97 to 222,868.60 MWh/year.

4.1. Sugarcane Bagasse Availability in Jamaica

Sugarcane bagasse’s availability is calculated using the average output over ten years (2009–2018) (Figure 5) from the six available factories to derive the substrate available for biogas production computed by Equations (1)–(3). The computation is used to derive theoretical potential biogas and electrical energy computations, as seen in

Table 5. Total potential electrical energy per year without factor variables and baseline scenario.

Scenarios	Residue Type	Total Residue (kg/day)	Total Available Residue (kg/day)	Residue Mix (ratio)	Potential Biogas (300 days) (m3/year)	Total Electricity Potential (MWh/year)
CASE 1	Dairy cow dung	106,887	53,443	-	4,920,495	3,187,742
CASE 2	Swine dung	215,393	10,769,650	-	934,536,378	6,859,029
CASE 3	Sugarcane bagasse	399,478	42,784	-	3,514,281	2,213,997
CASE 4	Sugarcane bagasse and dairy cow dung	399,478 and 1,068,867	42,784 and 42,784	1:1	18,893,400	12,240,089
CASE 5	Sugarcane bagasse and swine dung	399,478 and 407,093	42,784 and 1,426,133	3:1	10,814,083	7,721,255

The parameters and findings in Table 5 are based on Equations (1)–(7).

.

One may argue that a declining industry may halt production. However, sugarcane comparatively grosses considerable production value annually among many crops cultivated in Jamaica (Figure 2). Furthermore, the old industry is relatively stable, notwithstanding the recent decline in production. Therefore, improvements in technical, structural, and operational capacities will remain viable for producing bagasse annually.

Nonetheless, sugar is a part of Jamaicans’ staple diet, maintaining consistently high demand locally, predominantly for brown sugar. Additionally, it is among the significant foreign exchange-earners behind bauxite and tourism. Jamaica has special and preferential treatment in the European and United States markets: assured duty and quota-free trading. This entry guarantees the reasonable stability of crop production since demand is ever relevant to generating supplies. Substrate content is vital in determining levels and rates of methane generated from the anaerobic process. Energy crops and their content, such as sugarcane bagasse, sugarcane straw, corn, sorghum, cassava, and Napier (elephant) grass, produce high methane levels, an essential component of biogas indicated in much research, including [31,55,56,57,58,59,60,61]. Thus, the use of sugarcane bagasse is a relevant feedstock for investigation.

4.2. Livestock Production and Availability in Jamaica

Poultry has the highest number of animals compared to other animals, as revealed in Figure 6; however, the manure count is diminutive. Moreover, farms are numerous, spreading out over a large area. Additionally, the collection efficiency will be lower, given the high capital cost of collection amounts and points. Although research done by Grant and Marshalleck in 2008 [8] shows that the productive value of biogas is higher when chicken manure is added as a substrate compared to dairy cow and Swine, it is not considered in the study. Based on the availability identified in Figure 6, their suitability, and high collection factors, dairy cow and swine dungs are combined with sugarcane bagasse residue.

Within context, wastes from Swine and dairy cows are valuable biodegradable materials that have the potential to generate a higher degree of energy in co-digestion, with agricultural wastes in Jamaica utilizing the slurry-only system. Combining the slurry-only system with the AD of energy crops can yield increased energy output at low, long-term capital costs [29]. Figure 4 represents a depiction of the process along with the possible outcome.

4.3. Potential Biogas Yield and Electrical Energy Generation

Utilization of the available feedstock shown in Figure 5 and Figure 6 with five scenarios simulates varying ratios described in Table 5—the calculated answers for theoretical potential biogas and total potential electrical energy from different residue types listed below. Under mono- and co-digestion conditions, without applying other factor variables, the presented scenarios can generate up to 2.49% of the total electricity generated in 2019, namely 4910 GW [6]. Nonetheless, system upgrades within the farming and sugar industries will increase the production of available feedstock, having direct positive effects. Furthermore, AD technology offers an alternative for improved efficiency in power generation when applied effectively.

4.4. Biogas Functionality

Energy generation is a crucial element of a nation’s development since it impacts the production and distribution of goods and services necessary for social amenity provision. The modes of production, distribution, and consumption have extensive repercussions on other sectors, such as tourism, agriculture, health, and infrastructural planning. Thus, the plan to reduce petroleum importation is necessary for sustained green growth in addition to energy security.

In 2018, oil imports amounted to USD 1.63 billion, accounting for 7–10% of Jamaica’s total gross domestic product (GDP) [62]. The transition from fossil fuels guarantees the possibility of resource reallocation from spending on petroleum imports to building human capital plus developing other industries. Subsequently, the sugar industry’s rejuvenation stands to benefit from the redistributed funds.

The sugar industry’s production has been on the decline in recent years. Production of sugarcane and sugar is decreasing, except for momentary spikes in production, partly due to low conversion efficiency from antiquated equipment and low competitiveness. Seasonal production stands at approximately 1.5 million tons [53]. In response to reviving the third oldest industry, which remains the single most important crop, representing 23% of total crop production in 2016, in Figure 2, the government drafted a strategy to improve the industry’s performance—"Country Strategy.” The target is to produce raw sugar, molasses, and ethanol, leaving bagasse behind as waste. The findings indicate that sugarcane bagasse can generate electricity, both under mono- or co-digestion AD processes, with sugarcane bagasse under fermentation producing 122,607.68 MWh and being the lowest output among the feedstock in mono-digestion and the co-digestion scenarios. Consequently, it is postulated that electrical energy generation from this valuable resource has great potential.

Despite the weaknesses in the sugar industry, it remains the country’s most important crop, contributing roughly 2% to GDP, and earns approximately USD 74.5 million annually. It provides jobs for about 38,000 people directly during the cropping season and 28,000 people off-season. An estimated 8% of the population derived their income now and indirectly from the industry in 2010. According to the Sugar Industry Authority, “sugarcane is grown in almost every parish; accounting for over 40,000 hectares, or 40% of the land under permanent agriculture. Furthermore, about one-half of the population live in sugar-dependent parishes” [51]. Notably, this research incorporates 33,000 hectares.

From 2003 to 2008, sugarcane bagasse represented 1.8% of energy generation; moreover, by 2009, 3.25% of RE was shared from thermal treatment [14]. Based on the findings, sugarcane bagasse’s treatment with livestock manure under AD offers a healthier solution for promoting circularity with the spill-over effect of electricity generation. Looking at the nature of the industry and its importance to society, finding ways to improve its sustainability is crucial. Developing countries such as Brazil, India, and Mauritius have found ways to stabilize sugarcane production in the local market while being internationally competitive. They also promote circular economies by using bagasse for energy production [55].

The NEP 2009–2030 supports the development of biomass, plus the environmental sustainability of sugar-dependent areas. AD digestion and co-digestion from bagasse in Jamaica represent a significant opportunity to reduce CO₂ emissions alongside fossil fuel-based energy dependence. Likewise, the process can stabilize the fledging sugarcane industry, boosting production to meet stipulated quotas within the European and American markets.

Continued pressure on the local industry from fluctuations in sugar prices, changes in quotas, and marketing approaches in international trade present opportunities for diversification and increased value-added products addressed by biogasification. Moreover, the animal husbandry industry stands to positively gain from biogasification through AD under the single- and co-digestion of manures to valuable biogas for electrical plus cooking energy. It offers recommendable solutions to treating animal manure by simultaneously providing organic fertilizers, reducing greenhouse gas emissions, and managing odor.

From the findings under single-digestion, 31,877.42 MWh per year can be produced from dairy cow manure, while swine manure generates 68,590.29 MWh per year from the available feedstock. This may be seen as negligible in comparison to the power generated from solar (20 MW), hydropower (29 MW), and wind power (99 MW) in 2020 [63]. Furthermore, co-digestion will amount to some unused residue, which can be utilized as mono-fermentation and then coupled with output from co-digestion conditions, thus increasing the total potential for electricity generation. For example, in the case of sugarcane bagasse combined with dairy cows, adding the remaining livestock manure of dairy cows and swine feedstocks alone will theoretically generate 137,201.77 MWh per year. Consequently, following the same principle, sugarcane bagasse co-digestion with swine and leftover residue from Swine and dairy cow manure will generate 222,868.60 MWh per year of potential electricity, amounting to 4.53% of the total electrical energy generated in 2019.

Additionally, it is environmentally beneficial to treat animal waste by biogasification instead of open dumping, as poor livestock waste management has adverse effects on water eutrophication and soil degradation and contributes to air pollution by greenhouse gas emissions [64,65]. Additionally, it provides an additional avenue to diversify the renewable energy systems on the island, thereby addressing the diversification of renewable energy systems outlined in the National Renewable Energy Policy [10].

Biogas is a relatively mature green technology that conclusively generates electrical energy. Current biodigesters consist of UASB and BST. The already developed systems are known to perform multiple functions concerning the mitigation of GHGs, the lessening of organic wastes, and the promotion of circularity. The Scientific Research Council recorded an estimated 360 small- to medium-scale systems as operational [31].

Notwithstanding, the benefits of expanding solar, wind, and hydropower are numerous. However, one benefit of expanding bioenergy is that it will improve the diversification of Jamaica’s renewable energy sources, especially if the emphasis is placed on waste characterization and separation, thereby improving the purity and collection capacity of food and green wastes, including garden waste—a viable feedstock material for biogas generation [9]. It is recommended that further study be carried out to assess potential biogas and heat energy generation from food and yard waste since the energy potential can be more significant given the target C/N ratio of kitchen waste, −20.3, and yard waste, −20.9, compared to livestock manure, at 10.6 to 15.8 (Li et al., 2013) [9].

4.5. Potential for Improved Manure Management

Solar and wind power may be better options for electricity generation in Jamaica, given the country’s geographic location and renewable energy potential, as seen in Table 1. Nonetheless, biogasification offers benefits beyond heat and electrical energy output, promoting a circular economy, improved manure management, and methane emission reduction while obtaining biofertilizers as another gain. To date, Jamaican authorities have set no clear standard for the managing and disposing of agricultural wastes (animal manures and wastes from crops). Statistics indicate that 90% of all farm types are categorized as small in Jamaica, of which 4851 are registered livestock farms, as indicated by the Ministry of Agriculture and Fisheries (MoAF) (Ministry of Agriculture and Fisheries (MoAF), 2020) [66].

When treated by fermentation, agricultural waste boosts ecological farming by providing pathways to institute strategic circular economy models, where the 4R approach of reducing, reusing, recovering, and recycling after production creates sustainable communities. Significant amounts of potential biomass energy and resource recovery are currently being wasted on the 230,000 registered farms [67]. Another negative environmental impact that can be mitigated is the pollution from chemical fertilizers applied to crops, which causes a decrease in soil quality and deterioration in groundwater quality, as discussed in the works of Savci, S., 2012 [64], Lal, R., 2015 [65], and Uddin, M., et al., 2021 [68].

As the country’s population increases, the government pursues increased agri-supplies to meet demand. However, it faces challenges that can be mitigated by applying circular synergistic agricultural practices since they support ecological and socio-economic goals.

Several pathways should be considered for their improvement. These include (1) Instituting systems to monitor and reduce CO₂ emissions by livestock and other agri-waste, which are essential for CO₂ abatement since the government’s national development plan (Vision 2030 National Development Plan (NDP) Planning Institute of Jamaica, 2009) [1] intends to achieve a 7.8% CO₂ reduction. Thus, government intervention is necessary to develop clear national regulatory standards for livestock manure and other agri-waste management. The action should be achieved by instituting a public ordinance, including a penalty for violation. Such measures are significant for CO₂ abatement. For example, the Ministry of Agriculture, Forestry, and Fisheries (MAFF), Japan, established the “Act for Promoting Proper and Use of Management of Livestock Manure” (later, Livestock Waste Management Act) in 1999 with five years moratorium and then fully enforced it from 2004. The latter helps guide further technological development in agricultural science, especially agri-waste management (Mishima et al., 2017) [69]. It also improves the solid waste management system and reduces the amount of waste going to landfills.

(1)

The above systems should include resource and recovery mechanisms using efficient technology, for example, BIMA digesters.

(2)

Upgrade current systems in Jamaica as some of the BTS up-flow models were installed during the 1980s.

(3)

Biogas projects need to be promoted by the government and other stakeholders in rural areas and large-scale factories.

(4)

Rural, family-owned farms have limited capital for investment in new, applicable, sustainable, and ecology-based high technology. Therefore, the government should subsidize such businesses to aid in sustainable manure management.

(5)

Technical support and consultation regarding environmental initiatives are needed for all farmers in Jamaica, not just livestock farmers. However, crop farmers might also value resource recovery since the waste types yielded contribute to industries’ circular economy models and synergies.

(6)

The success of sustainable agriculture requires proper planning with an emphasis on economic viability as such, a system with several industries combined is necessary to generate profit.

(7)

Government support is necessary for the success of agri-waste treatment by fermentation in Jamaica since the technology required can be expensive for low-earning farms. Jamaican farms’ adaptable and amenable technologies are also considered the available natural resources.

4.6. Biogas for Sustainable Development in Communities

Biogas is often used to generate electricity but offers more solutions for domestic use, such as replacing traditional biomass, which includes burning wood for energy needs. This fuel source provides heat and light and substitutes for cooking. The utilization of biogas and its attractiveness vary according to location and conditions.

In 2005, an appraisal showed that approximately 37,000 tons (t) of charcoal was processed per annum for domestic use. The implication is a threat to plant biodiversity. Jamaica’s landmass spans 10,900 km², with roughly 31%, 339,000 hectares, remaining forested. The forests comprise pine trees, mahogany, teak, cedar, and eucalyptus trees, among other common tropical species (Loy and Coviello, 2005 [70]; United States Agency for International Development (USAID), 2021 [71]). Demand for fuelwood utilized in cooking plus heating puts strain on forest resources. Nonetheless, it is hard to calculate the amount of deforestation from harvesting firewood since the Forestry Department has no official deforestation record. Estimates indicate that approximately 50,000 hectares of forest are necessary to satisfy the demand for firewood and charcoal, of which 11% will be met through reforestation by the department (Loy and Coviello, 2005) [70].

Some significant negative implications of using charcoal for cooking and heat are social, ecological, and environmental losses and damage to health, such as respiratory illnesses and associated costs, plus soil and air quality deterioration [72]. A shift to resource recovery is essential for domestic socio-economic stability to maximize domestic energy. Some rural community members who spend their disposable income on healthcare because of exposure to fuelwood can benefit from the change. Accessibility to biogas cylinders for cooking and heating offers several positives beyond improved human well-being. It encourages the better management of environmental resources for sustainability by promoting economic circularity. Specifically, it promotes the following:

• The amelioration of quality of livestock and agricultural wastes.
• The provision of support for local businesses and rural community members with increased investments.
• Increases in energy recovery rate from bioresources, regenerating natural capital. In this case, namely agricultural and manure wastes.
• Sustainable energy production in communities, especially those outside urban centers, where remoteness hampers easy transfer of on-grid electricity. Moreover, where heating demand is high, alternative renewable energy sources such as wind, solar, and hydropower cannot fill the market demand.
• Contributes to sustainable social development by accentuating symbiotic relationships between private and governmental entities in exchanging goods. This structure improves circularity, a core element in energy recovery from recycling, as highlighted in sustainable development goal (SDG) number 11, Sustainable Cities and Communities, promoting a reduction in city resources and environmental impacts. Moreover, other connected SDGs to a circular economy include 7 Affordable Clean Energy, 12 Responsible Consumption and Production, 13 Climate Action, and 15 Life on Land.

Consequently, the way forward necessitates institutional and societal changes. For example:

• Improved coordination of industries, namely agriculture, with solid waste management.
• Improved waste management system, boasting a design within which wastes (feedstock) will be easily transferable to utilization zones.
• The promotion of family-sized or community-based methods will encounter fewer barriers, such as social acceptability, high startup input costs, and formal policies for streamlining development in the renewable energy market.
• Effective planning and market application to locate viable organic feedstock.
• Biomass residues collected on a large scale are appropriate for improving the current electric power generation. However, small-scale ones are applicable to meet household cooking needs in remote regions where natural gas and electricity are unreachable or too costly.

5. Limitations

The study reveals limitations regarding the underutilization of AD for biogasification. Utilization of increased data, including smaller farms housing <500 animals per head, can increase electrical energy output. Additionally, since poultry has the highest count per head and has a higher biogas generation rate, see

Table 6. Biogas production is based on animal residue.

Animal Dung	Biogas Generation (liters biogas/kg manure)
Chicken	70
Cattle	40
Pig	30

Source: Adopted from the study of Grant, S., and Marshalleck, A., 2008 [8].

[8]. Since there can be electrical energy production and pollution mitigation from broilers, houses on poultry farms in Jamaica are worth investigating further. This research can benefit stakeholders with site suitability analysis, carbon dioxide emission reduction evaluation, and an economic valuation of proposed biogas plant locations. Thus, part two (Jamaica’s Biogasification Site Suitability Analysis with Environmental Socio-economic and Technical Considerations) will address aspects of biogasification. The study is underway and considers both aspects for further appropriation. Moreover, it indicates the amount of bioenergy resource recovery to be exploited from given substrates. Thus, the information here is helpful for the government’s deployment to facilitate an environment that encourages a circular economy through the education of relevant stakeholders, including farmers, community members, and industry players.

6. Conclusions

The study uses the available government database information to calculate biogas production potential. The theoretical assessment uses the number of available livestock, collection factor, residue generation, and volume of biogas generation in cubic meters per kilogram. Applying the results, available livestock manure and sugarcane bagasse can produce up to 4.53% of the island’s total electricity demand.

When converted to electrical energy through biogasification, the residues contribute affordable alternative energy to fossil fuels, including petroleum, which the country is heavily dependent on for electricity production. The transition from fossil fuels guarantees proper resource utilization, with current government policies supporting case studies within this paradigm. For example, the National Energy from Waste Policy 2010–2030 has set out plans and guidelines which comprise the promotion of waste-to-energy schemes. In addition, it highlights that sugarcane bagasse, in combination with varying animal manure, enriches the potential of generating biogas through anaerobic digestion and co-digestion, which offers immeasurable benefits to Jamaican society to improve socio-economic, environmental, and agricultural standards.

Moreover, bioresources are easily accessible in Jamaica. Thus, available biomass residues can be collected on small and large scales and then efficiently utilized for power generation, cooking, or heating needs. Therefore, this research is valuable to the country and may appeal to other small island nations with similar crop and livestock production.