The review ensured the relevance and quality of the information sources by applying specific inclusion and exclusion criteria. The information was based on the researcher’s studies and grey literature sources.

The inclusion criteria for sources of information were the following:

1) Focused on Tanzania, Sub-Saharan Africa and the global south, where the global north was considered for only comparison or similarity reasons regarding the IVs and bioenergy and nutritional food sovereignty.

2) Addressed indigenous vegetables, bioenergy, nutrition, or food sovereignty

3) Provided empirical or analytical insights relevant to sustainable food-energy systems.

The exclusion criteria ruled out:

1) Studies unrelated to the core themes.

2) Research lacking precise data or findings, such as editorials or opinion pieces.

3) Sources older than 1990, unless foundational to the topic.

Using the above criteria, several documents, including articles, book sections, theses, and reports, were initially selected.

The retrieval of research information on indigenous/traditional vegetable-bioenergy synergy to support nutritious food sovereignty in Tanzania and other countries involved a comprehensive search of academic and grey literature. The literature comprises peer-reviewed articles, book sections, theses, and reports published over the past three and a half decades (1990-2025). The items were included to reflect both historical context and recent developments in sustainable food policy, which consider nutritious food sovereignty supported by IVs and bioenergy utilisation. Additionally, only academic and grey literature written in English was considered.

We used databases such as PubMed, Scopus, Journal Storage (JSTOR), and Google Scholar, as well as repositories such as the Sokoine University of Agriculture Institutional Repository (SUAIRE), to locate relevant literature. Additionally, the electronic resources subscribed to by Sokoine University of Agriculture (SUA) were used. Access to these electronic resources was done through the SUA library website (https://www.lib.sua.ac.tz/subscribed-e-resources). Furthermore, we considered reports from governmental, non-governmental, and international organisations. The reports include those from the Tanzania Food and Nutrition Centre (TFNC) (https://www.tfnc.go.tz/), Tanzania National Bureau of Statistics (NBS), Research on Poverty Alleviation (REPOA), Energy and Water Utilities Regulatory Authority (EWURA), Renewable Energy Policy Network for the 21st Century (REN21) (https://www.ren21.net/), Food and Agriculture Organization (FAO), and World Bioenergy Association (WBA).

We retrieved the information using the following search terms, combined with keywords: “indigenous vegetable seed,” “traditional vegetable,” “bioenergy,” “biofuel,” “food sovereignty,” and “nutrition in Tanzania and other countries”. Additionally, the Boolean operators (AND, OR) were employed to refine searches, ensuring that articles addressed the synergetic relationship between IVs and bioenergy toward nutritious food sovereignty in Tanzania and other countries. The following are the combinations of keywords using the Boolean operators: “indigenous OR traditional vegetable seeds AND bioenergy,” “synergy of indigenous vegetable AND bioenergy,” “traditional vegetable AND bioenergy for nutrition,” and “indigenous vegetable seeds AND bioenergy for food sovereignty.” All sources of the information, for the review, were subjected to above mentioned search terms from17th December 2024 to 10th March 2025. Articles were selected based on their relevance to the topic, methodological rigour, and contribution to understanding the synergy between IVs and bioenergy for the pursuit of nutritious food sovereignty. The authors of this review article conducted the review based on their expertise in food nutrition and renewable energy. Both authors have been engaged in food security projects. No disagreement occurred during the reviewing sessions.

Screening the studies in both academia and grey literature was done in two steps: 1) Title and Abstract Screening for eliminating irrelevant articles i.e., the article or report that does not contain any relevant keywords for example vegetable, and bioenergy, food sovereignty, food nutrition; 2) Full-Text Screening for reviewing the remaining articles or reports for relevance and quality where last two paragraph of introduction section, and the sections of methodology, results and discussion, and conclusion and recommendation have to include relevant information related to the indigenous vegetable, bioenergy, nutrition and food sovereignty.

Following a quality appraisal using an adapted CASP checklist to ensure the reliability of findings and a full-text review, a few documents initially selected were included in the final analysis, as stipulated by CASP-2018. Studies were assessed based on the clarity of research questions, appropriateness of the study design, robustness of data collection and analysis, and relevance to the Tanzanian and other countries’ contexts. During synthesis, we prioritised high-quality studies, especially those with comprehensive analyses or longitudinal data, as these provide a more reliable basis for formulating intervention and policy recommendations.

A descriptive analysis of sources of information was conducted, based on the Year-Wise distribution of the types of literature considered and the frequency of data source applications. Furthermore, a 4th-order polynomial trend curve was generated to show the accumulation of literature within the scope of this study.

Data were extracted and thematically synthesised using analytical frameworks similar to those reported by Pollock et al. [24] and Schmidt et al. [25]. The framework was applied across three interlinked domains: 1) Nutritional and agro-ecological roles of indigenous vegetables, 2) Productive uses of bioenergy in food systems, and 3) Synergistic IV-bioenergy pathways enabling nutritious food sovereignty. This framework enabled the identification of reinforcing feedback across nutrition, energy, environment, and policy systems [26].

As a review article, this study is limited by its reliance on secondary data, which may not fully capture all local-level distinctions or the most recent on-the-ground developments. Furthermore, the focus on peer-reviewed, high-quality sources may inadvertently exclude informal knowledge or recent innovations that have not yet been documented in the academic literature. However, this review seeks to provide a comprehensive analysis by triangulating sources [27] and combining academic, governmental, and international perspectives.

Using the inclusion and exclusion criteria shown in Sub-section 2.1 of this article, 350 documents, including articles, book sections, theses, and reports, were initially selected. Following a quality appraisal using an adapted CASP checklist to ensure the reliability of findings and a full-text review, 123 documents were included in the final analysis. The descriptive analysis of the information sources used to prepare this article is presented in terms of item distributions by year of publication and item type in Figure 1 and Figure 2, respectively. Also, the frequencies of using the data source during data extraction are presented in Table 1.

Figure 1. Combined published items distribution from 1992 to 2025.

Table 1. Frequency of data sources used to address the objective of this article.

Figure 2. Total number of published items for each type of source.

3.1.1. Year-Wise Distribution of the Type of Literature Considered

The distribution of published items by year of publication is as follows: 2024-2002 for journal articles; 2024-2017 for book sections or book chapters; 2024-2013 for reports; and 2024-2008 for theses. Figure 1 shows the ranges of the combined published item distributions from 1992 to 2025. From Figure 1, a 4th-order polynomial trend curve shows that publications on IVs and biomass energy research increased from 2007 to 2024. The increase might have been caused by greater attention paid to meeting the SDGs through initiatives worldwide.

Figure 2 shows that most of the information used in this article was collected from the journal articles. Most journal articles were based on the original research, as shown in the reference section. Little information was collected from the book sections.

Additionally, the synthesis of the 123 items included in this study is presented in the subsequent subsections. The synthesis focused on addressing the research question of how IVs and bioenergy can synergise to support the attainment of food sovereignty that is nutritious in Tanzania and other countries.

3.1.2. Data Sources Application Frequency

The items, i.e., articles, theses, book sections, and reports synthesised were obtained from different journals and the websites of reputable organisations, including national and international agencies and organisations. Major publishers where most of the data were collected include Springer Nature Switzerland, Elsevier, Emerald Publishing Limited, Wiley, and Springer International Publishing (Table 1). SUA has the highest frequency [17] among all data sources shown in Table 1. SUA focuses on agriculture and allied disciplines; therefore, it is justifiable as a leading source of information on IVs and biomass energy. The diverse information sources ensure the relevance of the findings.

The synthesis revealed and confirmed three converging domains: 1) nutritional and agro-ecological roles of indigenous vegetables, 2) productive uses of bioenergy in food systems, and 3) Synergistic indigenous vegetables-bioenergy pathways enabling nutritious food sovereignty. Additionally, the synthesis provided insight into addressing the research question of ‘How can indigenous vegetables and bioenergy synergise to support nutritious food sovereignty in Tanzania and globally?’ Furthermore, the research question is addressed through the findings presented in the subsequent subsections and the following sections.

3.2.1. Indigenous Vegetables as Pillars of Nutrition and Resilience

The digestion of the extracted data revealed that the IVs contribute to nutrition security, climate resilience, agricultural sustainability and food sovereignty. The evidence consistently shows that IVs contribute disproportionately to micronutrient intake, dietary diversity, and climate resilience. As detailed in the subsequent sub-section, species such as Amaranthusspp., Solanumnigrum, and Corchorusolitorius provide iron, zinc, calcium, and vitamins essential for addressing child stunting and hidden hunger. Their adaptability to marginal environments and low input requirements positions them as strategic crops under climate variability. Beyond nutrition, IVs sustain agrobiodiversity, informal seed systems, and women-led knowledge networks—core elements of food sovereignty. However, their full nutritional value is often undermined by inefficient post-harvest processing and preservation methods. The contribution of IVs is explained in detail as follows:

1) Nutrition security

The findings show that IVs have rich nutrient profiles, such as Solanumnigrum, Amaranthusspp., and Corchorusoliforius found in Tanzania and Ghana, which are high in protein (15.5% - 22.8%), essential amino acids, minerals (calcium, iron, zinc), and α-linolenic acid. These nutrients address deficiencies common in sub-Saharan Africa [28][29]. Also, condensed tannins in traditionally processed vegetables, such as drumstick and amaranth, exhibit antioxidant and antidiabetic properties, thereby enhancing dietary health [29]. The nutritional values of IVs have led to efforts to promote knowledge sharing about their use. For example, in Tanzania, knowledge-sharing through social networks and school-based programs was argued to improve awareness of IVs and support food security [30]. However, a decline in IV use was reported in South Africa. This underscores the need for campaigns to preserve indigenous knowledge and promote IVs’ cooking and preservation techniques [31].

2) Climate resilience

Climate resilience can be seen in the adaptability and biodiversity hotspot management techniques used to address climate change issues. In terms of adaptability, IVs such as Cleome gynandra and Cucumis metuliferus thrive in diverse climates, including during dry seasons, ensuring year-round availability [32][33]. Additionally, low-water-use crops, including traditional leafy vegetables, are promoted in South Africa to address water scarcity [34]. Furthermore, biodiversity hotspots in Tanzania, such as Arusha and Morogoro, as well as in Ethiopia, host high vegetable diversity, which is critical for adapting to climate change [33].

3) Agricultural sustainability and practices

Agricultural sustainability depends on various factors, including the availability of reliable inputs like seeds. IVs supports biodiversity conservation and sustainable seed systems. Home gardens in Tanzania and Zimbabwe conserve traditional germplasm, with 52% - 81% of households relying on local seed sharing [32][35]. Additionally, strengthening informal seed systems, compared to formal ones, ensures access to climate-resilient varieties, including those of IVs [36].

The IVs’ traditional preservation methods, e.g., sun-drying, reduce post-harvest losses quantitatively but may also increase losses in quality and nutrient bioavailability. Regarding the issue of IV quality loss, Bighaghire et al. [37] proposed optimising preservation methods to retain the vital nutrients of processed IVs using an improved traditional method. IVs were reported to reduce dependence on external inputs and align with agro-ecological practices, as the seeds are readily available [38][39].

4) Preservation of IVs for nutritious food sovereignty

In Tanzania and globally, supporting smallholder farming rather than industrial-scale models preserves IV cultivation and aligns with food sovereignty principles [40]. Some countries have recognised the potential of IVs to support food sovereignty. They have formulated strategies to promote a wide range of valuable IV varieties. For instance, Ecuador amended its constitution to adopt food sovereignty, emphasising local production and traditional foods, including IVs, thereby reducing reliance on imports of agricultural inputs [20]. Also, traditional preservation methods for IVs, such as fermentation, mitigate losses. This has been noted in Haiti, where traditional foods are being promoted through policies aimed at reducing waste and enhancing nutrition [41].

Furthermore, fostering food sovereignty is enhanced through agroecology practices. The practices protect biodiversity and traditional knowledge while ensuring resilient food systems [42]. For instance, indigenous communities in Peru and Brazil maintain food sovereignty through diversified crops like maize and IVs’ home gardens, using agro-ecological practices [43][44]. Women, often custodians of traditional preservation techniques, play critical roles in reducing losses and maintaining dietary diversity [42]. Besides, they dominate seed conservation and decision-making in home gardens, but gender-transformative approaches are needed for equitable benefits [35][45].

3.2.2. Bioenergy as an Enabler of Nutritious Food Systems

Bioenergy systems—particularly biogas, briquettes, and gasification—enable productive use of energy across the food value chain. Agricultural residues, including IV waste, cassava peels, and cereal husks, represent a substantial untapped energy resource in Tanzania.

The literature demonstrates that decentralised bioenergy does the following: powers drying, milling, refrigeration, and storage; reduces post-harvest losses by up to 20%; replaces biomass combustion in inefficient stoves, lowering indoor air pollution, and produces by-products (e.g., biochar) that enhance soil fertility. Thus, bioenergy directly influences not only energy access but also food quality, safety, and availability.

Tanzania and other tropical countries have abundant biomass for bioenergy generation. There are various biomass sources in Tanzania, including agricultural residues such as maize, sugarcane, and cassava, as well as vegetable wastes. Agricultural wastes (e.g., cassava peels, maize stalks, bagasse) offer untapped biomass energy potential (~135 PJ/year) that could support decentralised energy solutions[40]. Conversion of these residues into bioenergy through processes such as anaerobic digestion, gasification, or briquetting provides a reliable energy source for food drying, milling, preservation, and storage, thereby reducing post-harvest losses, especially in humid areas [46][47]. Cassava waste yields bioethanol at 85 g/L and biogas at 15 - 23 MJ/kg of volatile solids, providing energy for small-scale vegetable processing [48]. Biogas from livestock manure and vegetable waste supports energy-intensive processes such as drying, oil extraction, and storage, improving the shelf life of IVs [49]. Furthermore, small-scale biogas plants in rural areas, for example, in Kenya and Bangladesh, use vegetable and crop waste to generate electricity for milling and refrigeration, enhancing food security [50].

Moreover, improved cooking technologies like microgasifiers and improved cookstoves (ICS) reduce firewood use. In Tanzania and Asia, technologies that enable waste-to-energy (e.g., rice husk gasification, citrus seed biodiesel) provide clean energy for food preservation while reducing reliance on fossil fuels, thereby enhancing the circular economy [51][52]. The reduction frees firewood for food processing and lowers indoor pollution. Also, residues from ICS, such as biochar, enhance soil fertility for vegetable cultivation [53][54]. Furthermore, sorghum biomass in semi-arid regions (e.g., Brazil and Africa) is densified into briquettes with heating values comparable to those of wood, which can be used to dry leafy vegetables [55].

The systems that combine drought-resistant crops such as sorghum with bioenergy production ensure year-round energy for food processing. Surplus biomass from agroforestry can power small-scale combined heat and power (CHP) plants [56].

The finding of this review is that the intersection of IVs and bioenergy creates a circular bioeconomy. In this system, IV residues and other agricultural wastes are converted into bioenergy; bioenergy supports energy-efficient processing that preserves nutrients; reduced losses and improved shelf life enhance food availability; reliance on imported food and fossil fuels declines, and environmental externalities are minimised.

Energy-efficient cooking and preservation technologies emerge as a critical nexus where nutrition and energy outcomes converge. When supported by coherent policies and gender-inclusive governance, these synergies translate into tangible gains in food sovereignty.

Bioenergy enables better utilisation of indigenous crops, including IVs, through energy-efficient cooking and storage technologies, ensuring nutrient retention and reducing waste. The findings regarding the synergy of IVs and the productive use of bioenergy are based on the above-mentioned fact. The subsequent subsections present a synthesis of the extracted data on the synergy between IVs and the productive use of bioenergy for nutritious food sovereignty in Tanzania and other countries.

1) Energy-efficient cooking technologies

The availability of efficient technologies facilitates the use of IVs and bioenergy synergy to process nutritious food. For instance, improved cook stoves and the integration of bioenergy reduce reliance on traditional fuels. The modern cook stoves (e.g., micro-gasifiers, pellet stoves) exemplify the integration advantage. They are powered by bioenergy (biogas, biodiesel, and briquettes) and reduce firewood consumption by 15% - 37%, lowering indoor pollution and preserving heat-sensitive nutrients in IVs [54]; [57]. Pellet cookstoves and other modern biomass systems (e.g., biogas cookstoves) enable faster, cleaner cooking while maintaining micronutrient integrity in IVs [57]. Also, rice husk gasification produces syngas for thermal drying [51], reducing post-harvest losses and preserving nutrient-rich IVs. Bioenergy sources, such as crop residues (e.g., cassava peels) and indigenous fruit/vegetable wastes, when converted efficiently into biogas or biodiesel, provide clean cooking energy without competing with food security [58][59]. Moreover, biodiesel produced from castor and jatropha meets the required standards, offering RE for food processing without threatening food sovereignty [58]. Integration of bioenergy and solar energy systems is vital for the reliable energy supply needed for food processing. It improves the system’s capacity factor. The abundance of biomass (including IV waste) and sunlight, especially in Tanzania, makes the system reliable for dehydrating vegetables and retaining vitamins and antioxidants better than open-air sun drying [60]. Furthermore, Tanzania’s NMNAP II and Five-Year Development Plan (FYDP III) advocate RE in agriculture, but implementation requires public-private partnerships [61][62].

2) Preservation and storage innovations

Decentralised biogas plants coupled with biogas generator power refrigeration units. The units extend shelf life and reduce post-harvest losses of various crops, including IVs. Reducing losses can reduce spoilage by up to 20% [46]. Also, solar drying and biogas-powered refrigeration extend shelf life, reducing post-harvest losses by up to 20%. For example, solar dryers retain nutrients better than traditional sun-drying methods. Drying vegetables using available, low-cost integrated solar technology offers an opportunity to increase the value of the seasonal surplus [63].

3) Circular bioeconomy and wastevalorisation

The synergy of IVs and bioenergy powers the circular bioeconomy by utilising agro-residues. Cassava peels, maize stalks, fruit seeds, and IV wastes are converted into bioenergy (e.g., biodiesel, biogas) using various technologies. This creates a closed-loop system for waste-to-energy in food processing [64][65]. For example, citrus seed biodiesel (with a 93% yield) powers machinery for vegetable milling and packaging [52]. Circular bioeconomy models repurpose non-edible fruit seeds into bioenergy, supporting local economies without displacing food crops. Furthermore, Carbon Credit markets incentivise bioenergy adoption, linking environmental and nutritional goals. This was noted in a study conducted in Bangladesh to assess the viability of utilising agricultural biomass-based energy to meet Bangladesh’s energy demands [66]. In the context of climate resilience, RE from biomass reduces greenhouse gas emissions and supports climate-smart agriculture [67]; agroforestry-bioenergy systems (e.g., sorghum and biogas in Brazil) enhance resilience to droughts while supporting food processing [55]. These lead to SDG alignment, with reduced greenhouse gas emissions (through waste-to-energy) and advances in SDGs 2 and 7 noted [59].

4) Enhancing food sovereignty

Some smallholder farmers in Tanzania adopt agro-ecological practices to grow nutrient-dense IVs (e.g., amaranth, spider plant). The practice can be supported by bioenergy for irrigation and food processing [68]. Agro-ecological practices enhance the use of locally available resources in farming. This phenomenon reduces reliance on imported farming inputs, thereby supporting food sovereignty. Policies in Ecuador and Haiti prioritised traditional crops and decentralised energy systems, thereby reducing reliance on imported foods [20][41]. Haiti’s food sovereignty policy prioritises smallholders and traditional foods, in contrast to Nigeria’s fragmented approaches. Effective policies require infrastructure for preservation and bioenergy adoption [69]. Also, Walters [70] emphasises that overreliance on imported seeds threatens food security, but promoting indigenous varieties enhances local adaptability. Furthermore, agro-ecological practices prioritise the cultivation of IVs, aligning with food sovereignty principles [42].

5) Nutrient retention, health and dietary diversity

Energy-efficient cooking (e.g., cooking with gasifiers) preserves iron, vitamin A, and folate in leafy greens, i.e., in indigenous vegetable dishes. Consuming these dishes with the mentioned nutrients helped address Tanzania’s 35% child stunting rate [71]. In Kenya, the coupled interventions of production and nutrition education increased Women’s Dietary Diversity Scores (WDDS) by 21% while enhancing access to nutrient-dense IVs [71]. Chicory (Cichoriumintybus) and Sintrong (Crassocephalumrepidiodes) are IVs found in India, Indonesia, Italy and Bulgaria. Research on these IVs has demonstrated the global potential for their use in managing diabetes and malnutrition [72][73].

The challenges constraining the synergetic IVs and productive use of bioenergy include the limited information on the bioavailability of IV nutrients and anti-nutrient effects that require further study [28]; inadequate storage, transportation, processing, and preservation facilities that hinder biomass utilisation [63], and minimal investments in integrated solar drying and biogas plants, which are needed in rural Tanzania [63]. Furthermore, the use of modern cooking solutions in Tanzanian households remains limited; investments in pellet stoves, biogas systems, and other clean cooking technologies are critical [61].

Nutritional values of post-harvest produce are assessed quantitatively and qualitatively, with macro- and micronutrients expressed in standard units or percentages [28][74]. The agricultural value of the produce can be expressed in several ways, including identifying opportunities across all components of its value chain.

With this note, the IVs Nutritional and Agricultural Values were evident in terms of nutrition security, climate resilience, agricultural sustainability and food sovereignty. IVs provide essential nutrients to improve dietary health, leading to their promotion; however, awareness of their benefits and their decline in use are reported. The significance of the IVs and their promotion has also been reported by Mbhatsani et al. [75]. Besides, various varieties of IVs in Tanzania and other countries thrive in diverse climates, ensuring their availability throughout the year and their critical adaptation to climate change. The resilience of the IVs to climate is valuable, as was argued by Chepkoech et al. [5].

Furthermore, IVs’ sustainability is guaranteed, provided they are not affected by invasive species, as their seeds are locally available and sometimes shared at minimal cost. However, Mativavarira et al. [76] call for strengthening informal seed systems to address IVs’ seed availability. Most traditional preservation practices for IVs lead to a loss of product quality; however, improved practices can be developed. IVs must be valued in terms of quantity and quality [77].

Nutritious food sovereignty is supported, among others, through the sensitisation of IVs farming. Some countries have formulated policies and even amended their constitutions to incorporate food sovereignty grounded in local production and traditional foods, including IVs. These initiatives have led to the development of several projects and programmes aimed at boosting the countries’ locally based nutritious food sovereignty [78]-[80]. Agro-ecological practices and women’s involvement in promoting the IVs are vital for supporting food sovereignty. These matters are insisted on by [81] and Ekomer et al. [82].

Resources in Tanzania are abundant for producing bioenergy equivalent to 135 PJ/year. The trend is similar to that of other tropical countries. The primary sources of bioenergy are agricultural waste, including vegetable waste. Proven conversion processes for biomass into bioenergy (e.g., briquettes, biogas, bioethanol) for productive use, along with their associated technologies, are available. The productive use of bioenergy includes powering systems for post-harvest processing, preservation, and storage, leading to reduced quantity and quality losses and to improved shelf life of produce (e.g., IVs and food).

Examples of productive uses of bioenergy from agricultural waste include generating electricity for refrigeration via systems such as biogas-fueled generators [50]. Also, clean cooking through improved cooking technologies that use bioenergy lowers indoor pollution, reduces fossil fuel dependence, and by-products (e.g., biochar) from improved cook stoves enhance soil structure for vegetable cultivation. Furthermore, biomass resources power small-scale CHP plants. The availability of biomass resources, the conversion technology, and the productive use of bioenergy described in this subsection are similar to those reported by Babu et al. [7], Sikiru et al. [83], and Tshikovhi and Motaung [84].

The synergy of efficiently applying improved cooking technologies, including clean energy such as bioenergy, to prepare food involving IVs offers the following: retention of heat-sensitive nutrients in the IVs dish and reduced reliance on environmentally polluting firewood. Also, the synergy enhances reduced post-harvest losses of nutrient-rich IVs and other produce through processing, provides clean energy from agricultural wastes without threatening food sovereignty, and offers the option of integrating bioenergy and other RE systems to improve the capacity factor for processing post-harvest produce and food.

Moreover, synergy between IVs and bioenergy facilitates innovations in postharvest preservation and storage, the circular bioeconomy, and waste valorisation, thereby enhancing food sovereignty, health, and dietary diversity. The facilitated initiatives support the nutritious food sovereignty in Tanzania and other countries. The synergy advances the nations and international agenda, including Tanzania’s NMNAP II and FYDP III, as well as SDG 2 and SDG 7. The synergy of indigenous vegetables and bioenergy is demonstrated in the conceptual framework (Figure 3). Indigenous vegetables supply nutrient-dense food and biomass residues. These residues are converted into bioenergy, which powers energy-efficient cooking, processing, and storage. The feedback loop reduces losses, enhances nutrition, and supports a circular bioeconomy, reinforcing food sovereignty outcomes.

Figure 3. Conceptual framework illustrating the synergy between indigenous vegetables and bioenergy.

The challenges hindering the full potential of the synergy include limited information on the bioavailability of IV nutrients and anti-nutrient effects, scarce and affordable digesters and other infrastructure, and minimal investment in biomass utilisation and the integration of RE systems. Also, the adoption of modern clean-cooking solutions is low in Tanzania. The information presented on challenges is similar to that reported by Byaruhanga and Isgren [85], Diamantis et al. [86], Freitas et al. [87], Huang [88] and Rajendran et al. [89]. One option to address the challenges mentioned is to increase awareness of the merits of synergy among stakeholders, governments, and financial institutions to support concession loans and subsidies in communities below the poverty line.