Mycelium Composites for Sustainable Development in Developing Countries: The Case for Africa

The socio‐economic struggles in Africa are partly attributed to the low productivity of the agricultural sector. The Sustainable Development Goals Centre for Africa (SDGC/A) and the African Development Bank Group (AfDBG) both agree that the continent needs sustainable interventions to boost agricultural productivity, employment, and income. In this regard, mycelium composite production can present one potential solution. The added value to agricultural waste used to produce mycelium composites can generate additional revenue for farmers, serving as an incentive to increase agricultural productivity. Furthermore, the establishment of mycelium composite start‐ups can increase employment and income, especially for women and the youth. Mycelium composites can also aid in mitigating environmental and health challenges caused by some of the current waste management practices in Africa. This review offers valuable insights into the potential use of mycelium composites as a sustainable alternative for Africa. It explores the potential use of locally accessible resources, the potential applications for the composites in Africa, and the potential challenges that may arise with this technology. It further assesses the potential contribution of this technology to sustainable development in Africa in line with the Sustainable Development Goals (SDGs) set by the United Nations (UN).


Introduction
3][4][5][6] They have gained significant attention, especially in the Global North, in the last two decades as potential alternatives to DOI: 10.1002/adsu.202300305conventional fossil fuel-based materials. [7]ycelium composites are grown by harnessing the inherent ability of filamentous fungi to grow into 3D interwoven networks while degrading organic matter. [8]In mycelium composites, this network acts as a binder for the organic particles (i.e., the organic substrate) on which the fungus grows. [9,10]Agricultural, agro-industrial, and forestry residues are typically used as the organic substrate, acting both as the main nutrient source as well as a scaffold for the fungus. [1]Thus, the production of mycelium composites is considered cost-and energy-efficient as it eliminates the need for complex high-end manufacturing processes. [2]The composition of mycelium composites makes them biocompatible, biodegradable, recyclable, and compostable, which further adds value to their use. [5]n this review, it is proposed that mycelium composites could be used to address some of the socio-economic and environmental challenges in developing (i.e., low-and middle-income [11] ) countries, using the African continent as a case study.First, the use of agricultural wastes adds more value to this otherwise waste biomass, while providing a greener agricultural waste management route. [6,12]According to the World Wildlife Fund (WWF), the global post-harvest agricultural waste generated each year amounts to 1.2 Gt (15.3% of the total mass produced). [13]This is particularly problematic in developing countries that heavily depend on agriculture for food and income.In Africa, agricultural waste constitutes a substantial portion of the overall waste generated and poses a serious threat to the wellbeing of the environment and the population. [14]Yam and cassava peelings, cassava stalks, plantain trunks, and leaves, and cocoa husks and pods collectively account for over 70% of the total agricultural biomass generated in Africa. [15]In Ghana, for example, this amounts to over 20 Mt every year. [16][17][18] As an alternative, it has been suggested that this biomass could be used to produce biogas, liquid fuel, pulp, and paper. [16,19]However, despite being relatively cost-effective, the carbon footprint, the need for chemical treatments, and the energy requirements for some of these applications make it necessary for other alternatives to be Figure 1.Stages in the manufacture of mycelium composites.Reproduced with permission. [1]Copyright 2019, Elsevier.
Additionally, the engagement in mycelium composite production has the potential to enhance productivity in both the local agriculture and mushroom farming sectors.It is believed that low agricultural productivity is one of the main obstacles to economic progress in Africa, despite the continent's dependence on agriculture for food, income, and employment. [29,30]On the other hand, the mushroom market is still underdeveloped and contributes only 0.07% of the global production. [31]The lack of interest in mushroom cultivation [32][33][34] has been attributed to various factors: the limited documentation on the characteristics, growth requirements, and ethnomycology of locally available fungi; the scarcity of fungal biologists; the lack of infrastructure, adequate technical support, and operating capital. [35,36]Revenues from the sale of agricultural waste materials and local mushroom species to mycelium composite producers could serve as an incentive for farmers to boost productivity and engagement in these sectors.The mycelium composite market could also generate more employment opportunities (and income) for the population.
This review presents mycelium composites as a potential sustainable material for developing countries, using Africa as a case study.It provides an overview on mycelium composites to understand the requirements for establishing a mycelium composite industry.It explores locally accessible resources that may be viable to produce mycelium composites and outlines the potential challenges that need addressing to make this technology feasible in Africa.It explores the potential application in mitigating some of the major environmental challenges in the continent; it further assesses the potential contribution of mycelium composites to sustainable development in Africa in line with the Sustainable Development Goals (SDGs) set by the United Nations (UN). [29]ble 1.Physical and mechanical properties of mycelium composites (MC), high-density polyurethane (HDPU), and expanded polystyrene (XPS).Ref.

Mycelium Composites: An Overview
Mycelium composites consist of organic substrate particles bound in a 3D interwoven mycelium network made of thin filaments known as hyphae. [37]They are typically grown using whiterot filamentous fungi like Ganoderma lucidum, Trametes versicolor, and Pleurotus ostreatus for their inherent ability to decompose lignocellulosic macromolecules. [2,37,38]Figure 1 shows the steps involved in the production of mycelium composites.The organic substrate is hydrated, inoculated (with fungal spores, hyphal tissue, or mushroom tissue), and then incubated at ≈25°C under controlled humidity to provide an environment suitable for fungal growth. [38]The time span for incubation ranges between 7 and 30 days depending on the growth kinetics of the fungus and the desired mycelium density.The as-grown composite is finally oven-dried or hot-pressed at temperatures ranging between 60 and 100 °C to kill the fungus and improve stiffness. [39]8] Copyright 2019, Elsevier.
Generally, mycelium composites are good thermal, and acoustic insulators: their thermal conductivity ranges from 0.04 to 0.18 Wm −1 K −1 [1] and they can absorb up to 75% sound at frequencies below 1.5 kHz [41] with a typical Noise-Reduction-Coefficient (NRC) of 0.4-0.53. [42]In comparison, commercial acoustic foams like HDPU can absorb up to 90% sound within the same frequency range, [43] and have a NRC of ≈0.644. [41]The thermal stability and fire-retardant properties of mycelium composites are quite poor, like other bio-based materials.However, they are tuneable and can be enhanced by introducing phenolic-rich substrates like lignin and silica-rich substrates, e.g., rice hulls or silica glass fines. [1,2]Also, filamentous fungi like T. versicolor typically develop a moisture-repellent skin around the composite, which protects the hydrophilic organic particles under high relative humidity (RH). [38]o far, the use of mycelium composites has been limited to semi-structural applications due to their relatively low mechanical properties (as listed in Table 1).The strength of mycelium composites seems to be directly related to the density of the material, with typical proportionalities seen for foam-like materials, as shown in the Ashby chart in Figure 2a.Hot-pressed mycelium composites generally have higher elastic moduli compared to cold-pressed and non-pressed (as-grown) mycelium composites, i.e., hot-pressed > cold-pressed > non-pressed.While nonpressed mycelium composites seem to exhibit a typical foam-like behavior, hot-pressed mycelium composites behave like wood and cork when deformed. [38]The increase in elastic modulus, stiffness, and flexural strength of hot-pressed mycelium composites has been attributed to: • The increase in bulk density and the reduction of pores, as seen in Figure 2b; • The heat-induced polymerization of lignin and the esterification processes; [46,47] • The reduced moisture which, otherwise, acts as a plasticizer; [1] • The formation of heat-induced cross-linkages between the amino acids in the mycelium cell walls and the functional groups of the organic substrates. [47]gure 3 shows the typical tension and compression stressstrain responses of mycelium composites with different densities.Both the elastic moduli and yield strengths increase as the density increases.The stress-strain graph for low-density mycelium composites shows a characteristic quasi-linear defor- Reproduced with permission. [37]Copyright 2017, Springer Nature.mation behavior up to failure. [37]However, as the density of the composite increases, the stress-strain graph shows a gradual change in gradient after the apparent yield stress at ≈100 kPa, as shown in Figure 3a; this behavior has previously been observed for other polymeric foams. [48]The ultimate tensile strength of the composite typically does not exceed ≈25 MPa, which is lower than that of the pure mycelium. [1]The tensile properties are a function of the hypha-substrate bond interactions and the structure of the mycelium network itself. [1,2,49,50]The low tensile strength has been attributed to the low hypha-substrate bond density due to limited fungal growth within the core of the material as a result of poor aeration. [2]s seen in Figure 3b, mycelium composites typically show a characteristic compressive stress-strain deformation behavior similar to that of high-density polymeric foams. [51]Therefore the compressive behavior of mycelium composites can be described using the deformation mechanisms for conventional polymeric foams.Under compression, high-density foams display a linear-elastic deformation followed by strain-hardening. [37]A gradual increase in stress is observed beyond the apparent yield stress [52] (typically below ≈8% strain for mycelium foams [37] ).This is because high-density foams are usually characterised by a smaller volume fraction of pores which gradually collapse as the compressive stress progresses, thus, resulting in the gradual transition between the two linear regions. [53]The compressive and flexural properties seem to be also related to the compressive properties of the substrate. [1]Stiffness is enhanced by hot-pressing the as-grown composites and can be further improved by incorporating inorganic and/or inert particles (highly stable particles that are not easily digested by fungi and, therefore, retain most of their characteristics) like cellulose nanofibrils, glass fines, and nanoclay particles. [2,54,55]

Factors Influencing Mycelium Growth and Composite Production
The thermodynamic, physical, and mechanical properties of mycelium composites depend on the composition and nutritive profile, the size and geometry of particles, porosity of the organic substrate, as well as the characteristics of the growth medium (e.g., humidity, pH, temperature, and aeration). [3,50]The subsequent sections provide an overview of these factors and how they could affect mycelium growth.

Composition of the Carbon Substrate
The choice of agricultural, agro-industrial, and forestry waste for mycelium composites depends on the specific requirement of the fungus used and its specific polymer degrading abilities. [50]][58][59] At present, the main sources of carbon for mycelium composites are predominantly based on lignocellulosic wastes from the cereal and forestry sectors. [1]Despite being largely available and inexpensive, they have often resulted in lower-density mycelium networks due to the complex structure of lignocelluloses.Pre-treatment processes (e.g., partial hydrolysis of cellulose and hemicellulose, and partial delignification) can potentially facilitate fungal decomposition of lignocellulosic substrates [60] but this may come at an added cost, making the overall process less economically sustainable.

Fungal Species Selection
The degradation abilities of fungi influence the morphology of the mycelium network and must be considered when selecting species for mycelium composite production. [61]Simultaneous decay fungi seem to grow faster than nutrient-selective (or selective) fungi, resulting in high-density mycelium networks characterized by finer hyphae on various substrate compositions (e.g., cellulose and dextrose substrates). [62]Examples of simultaneous decay fungi include T. hirsuta and T. versicolor.On the other hand, nutrient-selective fungi like P. ostreatus seem to typically develop stiffer hyphae with higher chitin contents on lignocellulose substrates compared to other substrate compositions. [62,63]anoderma lucidum, another selective fungus with a higher affinity for lignin, is found to grow faster on lignin-rich substrates, resulting in denser networks with longer and stiffer hyphae compared to when it is grown on glucose-rich substrates. [64]However, it is often suggested that mycelium composite materials should be grown using a mixture of substrates (composed of glucose, starch, and lignocelluloses) for balanced properties.For example, in a study conducted by Joshi et al. (2020) [65] mycelium composites based on a mixture of wheat bran, sugarcane, and sawdust particles showed improved thermal stability, hydrophobic properties, and mechanical strength compared to those based on single substrates (i.e., either wheat bran, sugarcane, or sawdust).

Physico-Chemical Properties of the Growth Medium
The growth kinetics and morphology of the fungal mycelium are dependent on various process parameters such as the composition, pH, humidity, and temperature of the growth medium. [66]n addition to carbon, fungi require a combination of other macronutrients and micronutrients such as calcium, nitrogen, and phosphorus [67,68] that are either supplied via the substrate or added as additives. [38,69]Added carbohydrates further increase the nutritional value of the substrates, regulate the medium pH, and improve the binding of mycelium to the organic particles. [62]alcium and calcium compounds like gypsum improve the morphogenesis and growth kinetics of hyphae. [70]Phosphate-rich nutrients enhance the rate of growth, the branching frequency, and the length of hyphae, resulting in mycelia with three times larger diameters. [68]Phosphorus also improves the fire resistance of mycelium composites by promoting char formation upon combustion. [71]Manganese ions influence the shape of the hyphal filaments by controlling hyphal tip polarity, degree of branching, hyphae diameter, and rate of chitin synthesis. [68]he pH of the growth medium is a function of the nitrogen content and can be regulated using a suitable substrate formulation. [68]Filamentous fungi typically grow at a pH between 4 and 9 (usually 7 is the optimum pH). [67]The pH of the growth medium fluctuates as growth progresses due to the constant change in the composition of the substrate as the fungus absorbs its nutrients. [72]At the same time, fungi secrete pHmodulating molecules such as organic acids to regulate these pH changes. [73]The ability of the fungus to adapt to specific pH levels, and the composition of the organic substrate determine the overall acidity/alkalinity of the system, with the prevailing pH driving the growth and morphology of the system. [68]Acidic systems are less desirable as they promote the breeding of yeast and bacteria and produce shorter hyphae; phosphates and urea-based substrates can be introduced as pH buffers. [67]he water absorption capacity of the substrate is also integral as moisture helps to sustain growth by promoting nutrient diffusion and enzyme stability.The degree of hydration of a substrate is a function of its water activity and depends on its water-binding properties. [67]For growth, fungi require at least 20% moisture. [67]owever, the hydrophilic nature of natural materials and the water generated as a by-product of decomposition by fungi causes an increase in the overall moisture content. [68]Above ≈70% moisture content, the organic particles tend to agglomerate, and this reduces the diffusion of O 2 , promoting CO 2 production and the breeding of bacteria and yeast. [67,68]A high CO 2 concentration results in longer and thinner hyphae with lower chitin concentrations, thus reducing the structural strength of the fungal cell walls. [68]CO 2 concentration is also influenced by the dimensions and geometry of the substrate particles: while smaller particles can provide a larger contact area for mycelium growth, they also have a higher chance of agglomerating, leading to a higher CO 2 concentration. [1,67,68]Thus, the need for optimization for a balanced growth environment.

Availability of Local Resources for Mycelium Composite Production
It is apparent that the mechanical properties of mycelium composites are heavily influenced by the characteristics of the mycelium binder and its interaction with the organic substrate residues. [1,8,37]In fact, the strength of mycelium composites is known to be a function of the hyphae-substrate bond density and has been found to be directly proportional to the density of the mycelium network. [1,2,49,50][58][59]  The image was reproduced using data provided by the FAO. [74]us, both constituents must be carefully selected to obtain composites with superior characteristics and expand their range of applicability.
The following sections provide a summary of the typical biomass waste generated from the agricultural and agroindustrial sectors, as well as the locally accessible fungi with potential for mycelium composite production.

Local Agricultural and Agro-Industrial Waste
Figure 4 and Table 2 show the main agricultural crops produced in Africa in 2021, obtained from data provided by the FAO, [74] and Table 3 lists the main composition of the agricultural and agroindustrial waste streams.The agriculture sector generates large amounts of post-harvest crop residues and agro-industrial byproducts in the form of vines (leaves, stalks, stems), pods, husks, peelings, skins, cobs, fibrous residues, bagasse, molasses, and pulps. [75]It must be noted that biomass wastes may be specific to the regions where their corresponding crops are primarily cultivated, harvested, and consumed (Table 2).Nonetheless, some of these as still cultivated and common in various African countries.Waste agricultural biomass may be classified as sucroserich, starch-rich, or lignocellulosic, the latter being the most predominant throughout the continent.

Sucrose-Rich Agricultural Wastes
Dense mycelium networks can be obtained using simple sugars like glucose, fructose, and sucrose; however, their relatively high cost makes them unviable for commercial mycelium composite Table 2. Main agricultural crops produced in Africa, quantities (in megatons), percentage of global production and leading African producers. [74]op Production (Mt) production. [1]For example, the current price of 1 kg of sugar is $0.45. [76]As a more cost-efficient alternative, the molasses from the sugar processing industry and the pulp and mucilage from the cocoa production industry could be used as nutrient-rich substrates.The high sucrose content of these by-products has previously resulted in high-density mycelium materials with 1.2 to 1.8 times larger hyphal diameters compared to those based on lignocellulose. [12,50]However, the low production of these byproducts from the respective industries could potentially limit the availability of this biomass for large-scale mycelium composite production.For example, the South African sugar industry, one of the largest global producers, [77] only generates 0.38 tonnes of molasses for every 8.46 tonnes of sugarcane. [78]

Starch-Rich Agricultural Wastes
Starch is considered a "first generation feedstock" for fungi because it is the most digestible polysaccharide and the second most digestible carbohydrate after glucose. [60]Hence, starch-rich biomass could offer a promising alternative to supplement or replace sucrose-rich substrates. [79]The cassava and yam processing industries generate large amounts of waste peelings that are high in starch content and constitute 10 to 13% of the dry mass of a tuber. [80]Considering that ≈203.6 Mt of cassava and 73.5 Mt of yam are produced each year (Table 2), an annual supply of at least 20 Mt of peelings would be available for mycelium production.This biomass could further be supported with the peelings from the potato, plantain, and banana processing industries as this biomass is also known to be starch-based. [15]

Lignocellulosic Agricultural Wastes
][83][84][85] Yet, lower densities (and strengths) have been recorded for mycelium composites based on lignocelluloses. [1]This is because their complex and stable structure requires a concentrated amount of enzymes by fungi to effectively decompose them into easily assimilable simple sugars, resulting in lower bioconversion yields. [86]his is also the case for other complex polysaccharides, amino acids, lipids, organic acids, and alcohols. [67]The effectiveness of lignocellulosic substrates can be augmented with nutrient-rich supplements [62] (e.g., sucrose and starch) or via pre-treatment processes, e.g., partial hydrolysis of cellulose and hemicellulose, and partial delignification. [60]Other properties of the lignocellulosic organic substrates like type (particulate or fibrous), particle size, and porosity, can also be optimized for composites with improved strength. [3,50]he pod husks and bean shells of cocoa, as well as the bagasse from sugar crops, constitute the largest lignocellulosic waste from the cocoa and sugar industries, respectively.The cocoa industries in Central and West Africa alone, for example, generate ≈6.7 million metric tonnes of cocoa waste (70-80% of the total harvest) every year in the form of husks, pods, and shells. [80,87]gain, the South African sugar industry generates 2.4 tonnes of bagasse (plus 0.56 tonnes of pressmud) for every 8.46 tonnes of sugarcane. [17]These lignocellulosic wastes and those from the plantain industry (i.e., peelings and leaves [88] ) are rich in water-soluble and NaOH-soluble extractives like waxes, lipids, and chlorophyll, which can easily be treated before mycelium inoculation. [15]In addition, the plantain industry generates one part of rachis, five parts of pseudostem, and 0.15 parts of rejected unripe plantain fruit for every plantain fruit produced. [88]arge quantities of lignocellulosic waste are also available from the cereal industry.For example, each kilogram of maize generates 0.5 kg of stalks, 0.22 kg of leaves, 0.15 kg of cobs, and 0.14 kg of husks. [99]The rice industry generates between 0.41 and 3.96 kg of straw and 20 to 33% of husks for every kilogram of harvested rice. [89]Maize residues are mainly composed of cellulose and hemicellulose and have lower amounts of lignin, [100] which may facilitate fungal degradation.On the other hand, rice residues are rich in lignin, inorganic particles (≈20% of total dry mass), and extractive matter (>10% of total dry mass), [89] which reduces the nutritional value of rice waste.Previous work on mycelium composites based on rice wastes as organic substrates has revealed that the high inorganic composition results in materials with limited hyphal growth, bond density, and, hence, strength. [1]However, the high silica and lignin contents in composites containing up to 75 wt.%rice hulls reduce the average and peak heat release rates (i.e., 107 and 185 kW m −2 , respectively), suggesting this could improve the fire-retardant properties of the composites. [1]he pressed fruit fibers, empty fruit bunches, kernel shells, and other residues from the palm oil industry constitute 90% of the total dry mass of the harvest (excluding fronds and trunks). [101]They also have significantly high amounts of lignin that can reach up to 50% in kernel shells, twice as high as that of banana pseudostem (17.3%), sugarcane bagasse (20%), and jatropha (29.6%). [100]Coconut wastes, on the other hand, have lower amounts of lignin and are heavily produced throughout the year. [98]This potentially makes coconut shells a better substrate for mycelium compared to oil palm residues, onion, [102] or peanut residues, [103] which are seasonal and difficult to recover.

Locally Available Fungi
It is estimated that the total number of fungal species across the world is ≈3.8 billion of which 135,000 are well documented. [9,104]ach species has unique anatomical, morphological, and physiological characteristics, which are highly influenced by the physical and chemical properties of the organic substrate and the growth medium. [68,105]Africa is renowned for its diverse climatic variations, which provide ideal environments for the growth and proliferation of various species of fungi: it is estimated that the continent could contribute to ≈25% of the global fungal biodiversity. [36][34]

Basidiomycete Fungi in Africa
Most basidiomycetes, including white-rot and brown-rot fungi, have the inherent ability to grow on a wide range of low-nutrient lignocellulosic biomasses. [66]Thus, the selection and use of these fungi among locally accessible species must be prioritized to potentially increase the cost-and energy-efficiency of mycelium composite production in Africa. [114]The most prevalent basidiomycete fungi in the tropical and subtropical regions in SSA are those in the genera Auricularia, Laetiporus, Lentinula, Lentinus, Marasmius, Termitomyces, Volvariella, Agaricus, and Pleurotus. [108,115]The Agaricus, Pleurotus, and Lentinula species are the most abundant and have been successfully cultivated by small-scale farmers on corn cobs, rice husks, maize bran, and sawdust. [34,36]This suggests that the growth requirements and characteristics of these species are understood, despite the poor documentation.Moreover, these species have already been extensively utilized in the production of mycelium composites, indicating a substantial body of research supporting their suitability for this technology. [8,21,38,83,85,116]

Ascomycetes Fungi in Africa
The Saharan climate, characterized by hot and dry days followed by extremely cold nights, favors the growth of truffles and truffle-like fungi belonging to the Ascomycota phylum. [106]hese are underground fungi also known as "desert truffles". [108]n North Africa, truffles are locally referred to as Al-Kamaa, Al-Fag'a, gibbah, khlaasi, Zubaidi, Eblaj, Nahbaat alra'ad, Terfas, Faga Al toyoor, Nabat Al Radh, asqal, Bidat El Ardh, and Banat Ober. [108,117,118]Desert truffles are also found in the Kalahari Desert in South Africa [107] where they are known as n'abbas. [109]mmon truffles and truffle-like fungi in Africa belong to the Glaziellaceae, Discinaceae, Morchellaceae, Helvellaceae, Tuberaceae, Pezizaceae, and Pyronemataceae families. [119]While the literature on mycelium-based composites typically reports the use of basidiomycete filamentous fungi, [4] the potential use of filamentous ascomycetes should also be investigated.

Potential Applications in Africa
The versatility and high potential of the material lead to a broad spectrum of innovative applications and services, which can be classified into different sectors, with the construction and design sector being the most prominent. [39]Mycelium composites are commonly used as cores and foams; [120] ceiling, thermal, and acoustic insulation panels; [120][121][122] and furniture. [5]The research community also envisions the potential use of mycelium composites as structural construction bricks, exemplified by projects like the Hy-fi Tower (Figure 5a), [123] the MycoTree, [7,124] and the Growing Pavilion. [125]Mycelium-based cutlery has also been proposed. [5]The mycelium composite market in Africa is still nascent and only a few small-scale startups have emerged in the last two years, located in Egypt, Kenya, and South Africa. [126]ycelium (Egypt) produces mycelium composites for planter pots (Figure 5b), insulation (Figure 5c), and packaging, as well as mycelium leather, a mycelium-derived product. [127,128]My-coTile (Kenya) is producing mycelium composite tiles as part of a project aimed at improving the livelihood of the rural community while promoting environmental sustainability. [129,130]Myco-Minded (South Africa) specialises in the production of mycelium composites for insulation, surfboards, planter pots, and water filtration. [131]Lastly, M2Bio Sciences, a USA-based nutraceutical biotechnology company in South Africa, has recently launched Hempcelium (Figure 5d) for packaging. [132]ycelium composites have demonstrated a huge potential for repurposing agricultural, agro-industrial, and forestry waste into valuable materials as proven by the success of the startups specializing in this technology. [3]Being biodegradable, biocompatible, and compostable, they can easily be disposed by composting, thus replenishing soil nutrients (e.g., nitrogen and phosphorus) for increased soil fertility, [133] without polluting the  [123] b) planter pot and c) insulating core panel by Mycelium. [127]d) Hempcelium packaging by M2Bio Sciences. [132]Images reproduced with permission of M2Bio Sciences, Mycelium, and HOLCIM FOUNDATION.
environment. [58,134]The following sections discuss some of the characteristics of mycelium composites that could be exploited in addressing some of the socio-economic and environmental challenges in the continent.

Expanding Local Production to Boost Socio-Economic Development
The production of mycelium composites could promote an increase in agricultural productivity and revenue while reducing hunger and the reliance on imported food in Africa.It is reported that the agricultural sector accounts for ≈25% of Africa's Gross Domestic Product (GDP) [135] and 60% of jobs across the continent. [136]However, the productivity of the sector still remains low and this, according to the Sustainable Development Goals Centre for Africa (SDGC/A) and the African Development Bank Group (AfDBG), is one of the main obstacles to economic progress in Africa. [29,30]On the other hand, the local mushroom market is underdeveloped.The most recent data provided by the FAO shows that in 2019 only 29,000 tons of mushrooms (and truffles) were produced in Africa, making up only 0.07% of the global production. [31]It is also estimated that the average annual production of mushrooms per farmer in most African countries is approximately 240 kg, with a sale price of about $2 per kg. [36,137]ycelium composite production could generate revenue for smallholder farmers and market women from the sale of agricultural waste and locally grown mushroom species to mycelium composite manufacturers.This, in turn, could be an incentive to expand their plantations, thereby, increasing agricultural productivity and generating local employment opportunities.Mycelium composite start-ups could also generate income and more sustainable employment alternatives across the continent, especially for women and the youth, therefore mitigating the surge in the unemployment rate driven by the rapidly growing population. [138,139]Previous studies have also shown that there is a correlation between the low average remuneration (and employment rate) of the population and their engagement in illegal artisanal and small-scale mining (ASM) activities as a source of income, for example. [140,141]142][143] The generation of alternative sources of income could therefore mitigate some of these challenges.

Plastic Waste Management
Agricultural, plastic, and electronic waste (e-waste) constitutes a huge problem in Africa and poses a threat to the environment and the health of the population. [26,28,144]South Africa, Kenya, and other African countries [27,[145][146][147] have long been battling with plastic and e-waste pollution which is rapidly deteriorating the environment. [148]The upsurge in waste generation has been attributed to the rapid population growth, rate of urbanization, changing consumption patterns, and the lack of adequate waste management infrastructure. [25,149]It is further aggravated by the volumes of waste imported from the Global North through the waste trade [150][151][152][153][154] and the dependence on refurbished electronic devices from these countries, which are often obsolete and irreparable. [144]The total municipal solid waste (MSW) generated in Africa in 2012 was estimated to be 125 Mt and is expected to be double this amount by 2025. [155]he MSW generated in Africa is mainly composed of plastics (≈13% by mass) and solid organic waste (≈70%) including food and waste from the agricultural, agro-industrial, and forestry sectors. [155]These are usually landfilled, incinerated, or abandoned in the open field. [148,155]Thus, increasing the amounts of greenhouse gases (GHGs) emitted into the atmosphere and the toxic chemicals leaching into the soil and water systems. [28]These chemicals sometimes seep into nearby farmlands and previous studies [148] have confirmed evidence of heavy metal contamination (Zn, Fe, Cr, and Pb).The health implications of toxic chemicals on the workers and residents near these waste sites include damaged nervous systems, decreased mental capacities, blood disorders, respiratory infections, and eye and skin irritation. [144]lastic and microplastic pollution has also been identified as the most detrimental to the aquatic environment and its biota. [156]nfortunately, the treatment of contaminated water and soil is difficult, expensive, and often impossible depending on the source of pollutants.
Previous studies have confirmed the plastic-degrading abilities of some fungi in the Basidiomycota and Ascomycota phyla. [157,158][161][162] Further research may be required to investigate the plastic-degrading abilities of other common basidiomycetes [162] popularly used in this technology, e.g., A. bisporus, T. versicolor, T. multicolor, [38,47,71] L. edodes, and G. lucidum. [20,81,82]Some Tremellomycetes, [163][164][165] Tritirachiomycetes, [166] and Ustilaginomycetes [167] are also classified as plastic-degrading fungi, but these are not common for producing mycelium composites.This is also the case for Dothideomycete [168,169] and Sordariomycete [162,168,170,171] fungi (Ascomycota phylum), known for their ability to degrade PE, polyurethane (PU), polystyrene (PS), and PVC among others. [162]he inherent ability of fungi to break down plastics may present a huge opportunity to incorporate plastics as substrates or additives in mycelium composites, providing an environmentally friendly solution for plastic waste management as well.Additionally, the replacement of synthetic plastics in some applications with mycelium composite alternatives could mitigate the impacts of plastic production [172] and plastic pollution [173] on the environment.Mycelium composites could be used as substitutes for some single-use plastics, plastic packaging (including XPS packaging), acoustic insulators, and fishing gear. [41]In the automotive industry mycelium composites could replace the synthetic foams found in bumpers, doors, roofs, engine bays, trunk liners, dashboards, and seats. [2]Mycelium leather, although not a composite, could also replace the synthetic leather used for car seats.

E-Waste Management
E-waste includes end-of-life (EOL) and/or intentionally discarded electrical or electronic items (e.g., household appliances, IT equipment, consumer electronics) and their parts. [24]It is reported that the cumulative amount of locally produced waste (≈50-85% of the total mass [174] ) and imported e-waste from the Global North exceeded 5.8 Mt in 2019. [26]Inadequate e-waste management practices result in the release of high concentrations of toxic chemicals, including lead, cadmium, mercury, dioxins, furans, and polycyclic aromatic hydrocarbons. [175]These pollutants have the potential to negatively impact the ozone layer and contribute to the challenges of climate change. [26]Egypt, South Africa, Nigeria, Libya, Algeria, Botswana, Gabon, and Namibia have been particularly affected by e-waste pollution. [25,155,176]ycelium composites could replace conventional plastic components in electronic devices, as shown in Figure 6: breadboards, enclosures, battery holders, and buttons. [177]The characteristics of mycelium composites that make them suitable for these applications are their low electrical conductivity and high fireresistance ratings. [3]Furthermore, this could help mitigate the fire outbreaks and incidents that have become more and more frequent in various African countries, resulting in the loss of lives and properties. [178]ycelium composites are also being investigated for more advanced electrical and electronic applications.Fungi can adjust to environmental changes due to their ability to sense light, chemicals, gases, gravity, electric fields, and mechanical cues. [179,180]his could permit the design of mycelium composites for optical, tactile, and chemical sensors; storage devices; signal processors, and decision-making tools. [181]Adamatzky [182] has suggested that mycelium decision-making tools could convert environmental stimuli received through the fruiting body into electrical signals and the computation would be conducted within the mycelium network itself.There is also an interest to use mycelium for the next-generation of monolithic buildings that can self-grow and self-repair using natural environmental adaptation mechanisms. [183]It has been demonstrated that the photosensing ability of mycelia can be enhanced by functionalising the substrate with conductive nanoparticles and polymer systems like poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). [184]Adamatzky et al. [20] have also explored the mechanosensing ability of mycelium composites and found that the pattern of their electrical activity changes when an external load is applied (Figure 7).Given this property, they could be used as on/off sensors. [20]hile research in this field is in its initial stages and far from being exhausted, [183] it should be explored in Africa to promote sustainability and innovation.and (d) breadboard.Reproduced with permission. [177]Copyright 2019, ACM.

Water Pollution Management
Water pollution is a pervasive problem throughout the entirety of Africa, impacting the inhabitants, wildlife, and vegetation of the continent. [185]The primary factor leading to water pollution is the release and accumulation of untreated industrial and municipal effluents into lakes, rivers, dams, and surrounding areas. [185,186]Agricultural effluents, [187] untreated sewage, [148] waste plastics, and ASM effluents [188,189] are the major contribu-tors to water pollution.The release and accumulation of mercury, mercury-contaminated tailings, and methylmercury are particularly problematic in Ghana, Mali, Tanzania, Burkina Faso, the Democratic Republic of Congo, and Zimbabwe. [190,191]These issues are further aggravated by uncontrolled deforestation, as seen in Cameroon and in the Congo Basin. [187]ungi are natural decomposers of organic matter and are good antimicrobial organisms; some species can also absorb, adsorb, and sequester heavy metals like lead, mercury, and selenium  [20] to study the mechanosensing properties of mycelium composites.Reproduced with permission. [20]opyright 2021, Elsevier.and pathological organisms (e.g., E. coli). [10,192,193]These characteristics can be exploited to treat anthropogenic pollutants and previous work has confirmed the efficiency of mycelium in the bioremediation of soil and water contaminated with pesticides, fertilizer runoffs, chlorine, and dioxins. [133,194,195]201] Ahmadi et al. [21] have recently investigated and proposed the use of cellulose-mycelium composite foams in water filtration and purification, demonstrating their relatively high filtration efficiency.According to the authors, the porous mycelium structure enables physical filtration and detoxification in low-pressure water streams. [21]The authors also found that the filtration efficiency increased with increasing mycelium network density: this was attributed to the higher microchannel density for the physical capture of impurities.In addition, it was found that the live mycelium appeared to be more efficient in neutralizing KOH polluted systems than the pristine cellulose foam and the composite with dead mycelium.KOH neutralisation was attributed to the accumulation of K + ions within the fungal hyphae controlled by K + /H + antiporters, which substitute a proton for a K + ion. [202]

Challenges in Upscaling Mycelium Composite Production
While mycelium composites hold great promise for sustainable development in Africa, it should be acknowledged that there may be drawbacks associated with this technology and its implementation.

Capital Investment and Recurring Expenses
The capital requirements and recurring expenses for operating a mycelium composite facility may present the biggest hurdle for Africa.These expenses depend on the scale of operation, the production capacity, the complexity of the facility, the equipment, the materials, the geographical location, and the local market. [203]The capital expenditure encompasses the cost of infrastructure, equipment, research and development (R&D), licenses, and permits. [204]The recurring expenditures for operating and maintaining the facility include the cost of labor, material supply, power supply, and other operational costs. [205]The associated costs would also have an impact on the pricing of mycelium composites in Africa, potentially rendering them inaccessible to the average individual for purchase.
To reduce the cost-related barriers, it may be critical to explore and capitalize on locally accessible resources and technologies.Investing in R&D could provide the knowledge required to understand how production processes can be optimized to obtain high-quality materials at affordable rates.Furthermore, fostering collaborations with various stakeholders, including research institutes, investors, and the local agricultural and mushroom markets, as well as international collaborations may be vital steps to enable this.

Scalability and Reproducibility
Reproducibility and standardization are necessary for large-scale industrial production but have not yet been achieved with this technology. [3]This has been partly attributed to the sensitivity of mycelium composites to many factors, including: 1) The composition, size, structure, defects, physical, and mechanical properties of the organic substrate; [1,56,67] 2) The degrading abilities of the fungus; [50] 3) The morphological, biochemical, and physicochemical characteristics of the mycelium network and its interactions with the organic substrate particles; [1,2,49,50] 4) Complex process parameters, e.g., temperature, relative humidity (RH, and pH; [39,66,68] 5) The choice of processing methods for sterilization, inoculation, mold filling, drying, and post-processing. [1,4]gure 8 shows the relationship between these parameters and their impacts on the properties of mycelium composites.The interactions between these parameters are complex and not fully understood, and often result in inconsistent properties even within a single production cycle. [4]This has been the main obstacle to achieving the industry-standard level of product certification.Other challenges are related to the uncertainty associated with biological organisms, the high probability of contamination, [3] and the long duration of a growth cycle which can take up to a month. [206]Well-established companies like Ecovative and Biohm have resorted to genetic engineering and optimization of fungal strains, as well as the co-incubation of microorganisms to overcome some of these obstacles. [3]frica is known for its climate, cultural, and urban diversity.This results in a diverse range of agricultural crops (hence the biomass waste), local fungal species, and locally accessible technologies.While this makes it possible to customize the properties of mycelium composites to fit geographical and climatic requirements, [3] it may also pose an obstacle to reproducibility and standardization of the properties of mycelium composites.Protocols would need to be developed to define standardized material properties and processing methods for large-scale production, which could increase the range of applications of this material. [4]

Sensitivity to Weathering Conditions
The mechanical strength of mycelium composites deteriorates under high RH. [38]In fact, mycelium composites are known to possess low weathering resistance [207] as a result of their hydrophilic nature. [208]This is partly attributed to the open pore structure of the composites caused by the loss of hydrostatic pressure within the hyphae and subsequent collapse of the cell wall after thermal treatment. [8,40,209]To improve their shelf-life [206] and fire-retardant properties, [210] mycelium composites are often coated with commercial waterproof coatings which are often not biodegradable.Coatings may also be applied to repel termites and insects that may be attracted by the emission of volatile compounds from hot-pressed composites. [211]This, while showing some improvement in weathering resistance and strength, impacts on the biodegradability of the material and may cause soil Illustrative framework of the factors and process parameters, and their impacts on the properties of mycelium composites.Reproduced with permission. [4]Copyright 2020, Elsevier.
pollution due to leakage of toxic chemicals. [210]Further investigation is required to assess the chemical composition and environmental impact of degraded coated mycelium composites. [206]lso, the porous surface of the composite sometimes limits the efficacy of surface coatings. [207]

Environmental Impact
Figure 9 shows the potential environmental impact at various stages of the mycelium composite production chain.The use of electricity and the transportation of materials (e.g., the agricultural biomass) seem to have a significant impact on the environment, [210] as seen in Figure 9, constituting the main hotspots.Energy is required to power sterilization, shredding, mold filling, incubation, drying, and hot-pressing equipment used in advanced facilities.In some African countries, relying on electrical power could be particularly problematic if facilities are established near farmlands for easy access to the agricultural waste: most farmlands are usually situated in rural areas where power supply is often intermittent and fixing power lines can be expensive.Therefore, using equipment and processing techniques that are not reliant on energy and are often rooted in local technologies and practices might offer greater advantages when considering the production of mycelium composites in Africa (and developing countries in general).Transportation of agricultural biomass to a production facility situated further away from the farmland may also contribute to a notable increase in the environmental footprint [212] and overall production cost.
The LCA conducted by Stelzer et al. (2021) [210] emphasizes the environmental impacts associated with the use of agricultural products and the overall mycelium composite manufacturing process.The potential for acidification, eutrophication, global warming, soil pollution, and photochemical ozone creation are higher due to the use of fertilizers in agriculture.This, along with the risk of bioresource competition, may escalate if individuals and enterprises decide to prioritize the potential economic benefits of mycelium composites.The water required for hydrating the substrates may also impact the environment and potentially lead to water scarcity in certain areas.It must be noted that current LCAs for mycelium composites are predominantly based on parameters obtained from laboratory scale production and that it is possible that the magnitude of the identified environmental impacts could escalate or reduce on an industrial scale.
The environmental impacts associated with mycelium composite production can be mitigated using various approaches, as suggested in other works: [206,210,213] 1) Using less energy-intensive alternatives; for example, pasteurization at 60 °C, hydrogen peroxide sterilization, or coincubation of bacteria and/or other fungal organisms to replace autoclaving which requires high temperatures (i.e., 121 °C) and pressures.2) Prioritizing renewable energy alternatives and less energy intensive practices over non-renewable energy sources.3) Integrating the mycelium composite technology with wellestablished locally accessible technologies.4) Prioritizing manual labor over advanced machinery, e.g., for shredding the organic substrate and filling the molds, on small-scale production.Environmental impact of a typical mycelium composite production chain.Reproduced according to the terms of the CC BY license. [210]opyright 2021, The Authors, published by MDPI.
5) Capitalizing on locally accessible agricultural biomass, which could also reduce the cost of transportation.6) Prioritizing forestry residues and low-grade agricultural biomass over nutrient-rich substrates, to reduce the environmental impact of the agriculture sector.Nutrient-rich biomass typically comes from crops with high nutrient and, hence, fertilizer requirements. [210]) Prioritizing biomass waste generated from other manufacturing processes and industrial sectors, e.g., using bamboo microfibers generated from industries that process bamboo for scaffolding applications or the wooden panels and window frames from building sites.
Nonetheless, the reported environmental impact of mycelium composites seems lower than that of conventional fossil fuelbased materials like concrete, sand-lime, and facing bricks: mycelium composite materials can save up to 2.5 times the amount of greenhouse gas emissions from concrete brick production and up to 3-6 times that from sand-lime bricks and facing bricks. [210]

Research and Education
The engagement of the population in mycelium composites may be challenged by the limited knowledge and expertise on local mycology.The knowledge of the characteristics and the requirements for domesticating locally available fungi is crucial not only to produce high-quality mycelium composites, but also for safety reasons, especially on large-scale productions.For example, some fungi are known to be pathogenic organisms and may be harmful to animals and plants. [39]These pathogens may release spores and mycotoxins [160,[214][215][216] as well as volatile compounds like alcohols, aldehydes, esters, phenols, and ketones. [217,218]Long-term exposure to these compounds could cause respiratory problems, compromise the immune system, skin penetration, and death. [39,219]Under specific conditions, even common low-risk fungi (e.g., P. ostreatus and T. versicolor) may become pathogenic. [39]Exotic fungal species can also become invasive, contributing to the potential extinction of other local fungal species. [220]Furthermore, white-and brown-rots can cause the decay of wooden structures in households, railroads, and utility poles.
While various biological routes have been proposed to mitigate these risks, [221][222][223] standardized industrial protocols are also required to monitor and mitigate some of the possible risks that may arise during the production of mycelium composites.This requires a deep understanding of this field and more support from the various stakeholders involved in mycology, which is currently very limited. [32,33]The risk mitigation considerations for the production of mycelium composites have been listed in Figure 10.
To prevent the escalation of potential hazards emerging from large-scale production of mycelium composites and preserve the ecological diversity of the continent, it is important to encourage collaborations with the existing research entities.For example, the Council of Scientific and Industrial Research (CSIR) across the continent may possess or could support in providing the necessary infrastructure, expertise, and technological capacity required to establish mycelium composite production in African countries that have yet to embrace this technology.They could also support emerging and existing enterprises, promoting the expansion of this market and encouraging the transition toward bio-based alternatives.

Discussion
The financial struggle in Africa has been attributed to the low agricultural productivity in the continent, among other reasons. [29,30]According to the SDGC/A, a 1% increase in agricultural productivity could lead to 0.5% decrease in poverty and unemployment rates. [29]The high rate of unemployment, low income, and the need to satisfy the demands of a technologically advancing society have resulted in a surge in illegal ASM activities.The lack of expertise, high cost of infrastructure, and lack of policies controlling these activities have further caused an unprecedented increase in environmental pollution, which is particularly affecting the aquatic ecosystem. [143]This issue is very renowned in Ghana, South Africa, Tanzania, and Zimbabwe: large amounts of toxic chemicals (e.g., cyanide), heavy metals Mycelium products could generate income for farmers through the sale of agricultural waste and for start-ups through the sale of composite products.

SDG2
The added revenue from the sale of agricultural wastes could promote an increase in agricultural productivity, thus, increasing availability of local produce.

SDG3
Mycelium composites can reduce environmental pollution and related health hazards in Africa.For example, by replacing single-use plastic packaging, they could help reduce the issue of plastic pollution.

SDG6
Mycelium composites can be used for mycoremediation of heavily polluted water systems, thus, providing access to clean water.

SDG8
Mycelium production can increase the income and employment rates across the continent.

SDG9
Mycelium composite can promote innovation in various sectors, e.g., construction, automobile, and packaging.

SDG11
Mycelium composites could reduce the amount of toxic chemicals resulting from the open-field incineration and disposal of waste.They can also support the transition towards a circular economy.

SDG13
The reduced toxic emissions and the low-energy requirements for production could mitigate some of the well-known environmental challenges (greenhouse effect, climate change, etc.).

SDG14
Reduced water pollution results in a healthier ecosystem for aquatic organisms.

SDG15
Reduced land pollution results in a healthier ecosystem for land organisms.

SDG17
Mycelium materials can stimulate transdisciplinary collaborations between scientists, citizens, and countries in finding sustainable, ethical, and affordable material solutions for many wasted resources.It can nourish a decentralised manufacturing approach.
(e.g., mercury, cadmium, lead, and iron), and organic chemicals discharged by ASMs have been found in surface aquatic systems. [142,148]Environmental pollution can also reduce the productivity of the workforce, loss of biodiversity in both aquatic and terrestrial environments, and loss of the aesthetic value of a country, which further impairs the economic growth of the continent. [26,28,148]t is evident that the African continent, as previously suggested, [29,30] needs sustainable alternatives that can increase income and agricultural productivity, reducing poverty and hunger, and at the same time mitigating some of the environmental challenges.In this regard, mycelium composites show huge potential. [2,21,69]The potential socio-economic benefits of bio-based solutions are evidenced by previous reports for Global North countries.For instance, in 2018 the European bioeconomy sector registered a turnover of ≈€ 2.4 trillion (equivalent to over $2.6 trillion), with biobased manufacturing industries contributing 30% of this total and leading to the creation of 3.5 million job opportunities. [224,225]Similarly, in 2017, the biobased sector in the United States supported ≈4.6 million jobs directly or indirectly, injected $470 billion into the U.S. economy, and led to the generation of 2.79 jobs in other sectors for every biobased job. [226,227]While these statistics offer promise, they do not guarantee that mycelium composites (and other bio-based solutions) may have comparable socio-economic benefits for African and other developing countries.Nevertheless, according to the International Labour Organisation (ILO), bio-based solutions could potentially generate more than seven million new jobs in developing countries. [228,229]he use of locally available fungi and lignocellulosic biomass could also support the expansion of local mushroom and agricultural markets. [230,231]In return, the expansion of the mushroom industry would also provide the infrastructure to help support the mycelium composite market and, potentially, provide more sustainable economic processing routes. [208]Mycelium composites also offer several ecological benefits: they allow the repurposing of waste; they are biodegradable, compostable, and recyclable at end-of-life; and they have the potential to mitigate some environmental challenges.
A summary of the potential contribution of mycelium composites to the achievement of some specific SDGs for sustainable development in Africa is presented in Table 5.
To support the expansion of the mycelium composite market in Africa, however, several challenges need to be addressed.First, the economic feasibility of this technology can be compromised, particularly in rural areas, due to the extensive dependence on electricity throughout the production process.In advanced production facilities, electricity serves to power various components such as LED grow lights, HEPA filter fan units, humidifiers within incubation chambers, as well as ovens and hot-presses.][234] Nevertheless, in anticipation of the possible obstacles related to the consumption of electricity, this machinery could be replaced with equipment and processing methods that are both more ecologically sound and economically viable.Ideally, these alternatives should be integrated with locally available technologies and practices.It should be noted that the environmental impact associated with the consumption of electricity might differ depending on the specific energy mix of a country or the chosen energy source for production.Consequently, it is important to conduct life cycle assessments (LCAs) and life cycle cost (LCC) analysis to identify the energy source that offers better ecological and economic benefits.
The substantial water consumption associated with mycelium composite production could pose further challenges.Water used for hydrating the agricultural substrate is indispensable as it is essential for maintaining a suitable relative humidity for fungal growth.However, water used for sterilizing (or pasteurizing) the agricultural biomass can be reduced by using water-efficient autoclaves or employing alternative sterilization methods, e.g., sterilisation by chemical treatment. [235]It is worth emphasizing that since all materials are sterilized before producing mycelium composites, different water sources can be used regardless of their contamination level.Thus, the incorporation of slightly contaminated water from other processes (e.g., agro-industrial processes) or harvested rainwater, for example, can be considered viable alternatives to mitigate the ecological impact of water use.
Furthermore, mycelium composites also display relatively low structural properties, making them unapplicable for large, selfsupporting structures.It is well-known that the strength of mycelium composites is not comparable to that of conventional construction materials. [3]For example, the compressive strength of mycelium composites can range between 0.35 and 0.75 MPa, [236] which is comparatively lower than that of conventional clay (69-140 MPa [3] ) and concrete bricks (≈22.5 MPa [4] ).Mycelium composites also display low weathering resistance Nonetheless, mycelium composites are comparable to commercial packaging and insulating materials and show a potential for application in addressing some of the major environmental pollution issues in Africa, e.g., agricultural waste management, plastic pollution, e-waste pollution, and water pollution.
The scaling up of mycelium composites in Africa can also be challenging due to the limited education and research in this field, the lack of suitable infrastructure, and the underdeveloped mushroom market.The climate diversity and variation in the composition and properties of agricultural biomass could also present a hindrance to the establishment of the mycelium composite market.Norms, regulations, and safety protocols are required to mitigate the impacts on the environment and the health of the population.The ongoing expansion of the mushroom market in Africa and the growing scientific interest in mycology show significant prospects for transitioning toward mycelium composite production. [4]Additional concerns are those arising from the possibility of bioresource competition and food waste as a result of potential agriculture overproduction.The social impact of this technology on African communities should also be investigated in further studies to account for all sustainability aspects. [210]

Conclusion
The agricultural sector plays an integral role in the economy of the African continent.However, the low productivity of the sector contributes to the high financial struggle and hunger in many communities.The SDGC/A and AfDBG both agree that increasing agricultural productivity can drive sustainable development in Africa, increasing income and employment rates, while reducing poverty and hunger in some communities.It is also believed that this could promote engagement in more sustainable practices, thus preserving the natural resources of the continent.It has been proposed that embracing bio-based solutions could support the socio-economic development of the continent.In this regard, bio-based materials like mycelium composites present a potentially sustainable alternative.Mycelium composites are essentially made of agricultural waste particles bound by a fungal mycelium network.They have gained a lot of attention as a sustainable green material that adds value to agricultural and agroindustrial waste.Many applications have already been commercialized for use as insulators, flooring panels, and foams.The scientific community is also proposing other advanced applications for the composites and a lot of research is still ongoing in this area.
The properties of mycelium composites are tuneable and can be customized through fungal species selection, growth medium parameters, and manufacturing processes, thus expanding their range of applications in different fields.Mycelium composites should be explored in African and other developing countries for potential use as: 1) Substitutes for conventional materials such as single-use plastic packaging, plasticware in electronic devices and synthetic foams in automobiles.2) Mycelium composite filters for water treatment via physical filtration as well as mycoremediation of toxic inorganic materials and pathological organisms (e.g., E. coli).3) Construction materials that could reduce the costs associated with building using conventional materials, while mitigating the environmental impact associated with the extraction, processing, and disposal of construction materials.4) Affordable bio-based materials for biomedical and electronic applications.
It must be acknowledged that, despite the attractive benefits mycelium composites may present for these countries, their relatively low strength and weathering resistance currently pose a limitation to their use.It is postulated that the life cycle of these materials could be extended to 20 years with regular maintenance; [237,238] however, this lacks research support at present.Moreover, further research is needed to investigate the weathering performance of mycelium composites under the varied climates found across Africa and to overcome their limitations to broaden their scope of application.

Figure 2 .
Figure 2. a) Ashby chart showing the elastic modulus against the density of non-pressed, cold-pressed, and hot-pressed mycelium composites compared to conventional materials.b) Non-pressed and hot-pressed mycelium composites.Reproduced with permission.[38]Copyright 2019, Elsevier.

Figure 3 .
Figure 3.Effect of density on the (a) tensile and (b) compressive stress-strain curves of mycelium composites.c) Variation of elastic modulus, d) yield, and ultimate tensile strength with respect to material density.Solid lines in (c) and (d) represent the expected scaling for open-cell foams.Reproduced with permission.[37]Copyright 2017, Springer Nature.

Figure 4 .
Figure 4. Agricultural crop production in Africa in 2021.The image was reproduced using data provided by the FAO.[74]

Figure 6 .
Figure 6.Applications of mycelium composites in electronics as (a) circuit boards, (b) an enclosure for Arduino UNO and as a (c) Circuit Playground, and (d) breadboard.Reproduced with permission.[177]Copyright 2019, ACM.

Figure 8 .
Figure 8. Illustrative framework of the factors and process parameters, and their impacts on the properties of mycelium composites.Reproduced with permission.[4]Copyright 2020, Elsevier.

Figure 9 .
Figure 9. Environmental impact of a typical mycelium composite production chain.Reproduced according to the terms of the CC BY license.[210]Copyright 2021, The Authors, published by MDPI.

Table 1
lists the properties of mycelium composites (MC), HDPU, and XPS.

Table 4 .
Common wild fungi species in different regions inAfrica.

Table 4
lists examples of local wild fungi species found in various African regions.Only local wild species were considered because of their potential economic viability, compared to exotic species, for mycelium composites in Africa while expanding the local mushroom market.

Table 5 .
Ways in which mycelium composites could address the SDGs and promote sustainable development in Africa.