In 2010, around 14 million camels were alive worldwide, with 90% of them being dromedaries, as well as around seven hundred feral in Australia, coming down from those introduced as a method of transport in the 19^th and early 20^th centuries [18]. According to Food and Agriculture Organization (FAO) [10] and Faye and Bonnet [14], the number of the camel head has consistently increased since 1961, but the growth rate varies across the regions, i.e. from 2.1% in the former Soviet Republics to 13% in Somalia.

According to Faye [15], the most essential issue concerning camel demography is not the development of the camels’ heads number, but its number inside the total livestock that is calculated by the extend of Tropical Animal Units (TLU) for each country. Nevertheless, the relative camel density is related to particular discernment perception such as social, financial matters, and their other global socio-economic profiles [19-21]. Wherever camels’ drawn 25% of the complete TLU in KSA but the most elevated density is discovered inside the Horn of Africa (more than 2 camels/km²), and the Middle Eastern Arabian Peninsula (1 camel/km²). Inside the KSA, the farming system shifts from ancient and straight forward simple shapes to a semi-intensive farms that would oversee the organic biomass of livestock natural waste with the value of an economic and sustainable component for the commonplace production [14,22].

Present and potential uses of biological products from the camel

Livestock resources have played a considerable range of roles in human life from the initial days of recorded history. Human beings have accustomed to the employment of Livestock for food, cloth, organic fertilizer, medicine and fuel since the past [22,24]. In addition to different areas of concern in religion, art, music, and literature and several other different cultural manifestations of humankind [22].

Nevertheless, camel is a unique mammalian vertebrate animal inhibiting the hot and arid desert habitat, due to its adaptation mechanisms in behavioral, anatomical and physiological functions [23].

Camels manure is used for the decomposition of organic compounds spilled within the soil/water in Sharjah (UAE) since it may be a suitable agent for filtration due to its higher fiber contents [22]. Also, it employed as a fuel, particularly among the rural communities because it is prepared to burn after a number of minutes unlike cow dung and other organic trashes that takes several days in sunshine to dry [22,24].

However, CM and its scale of production are specific in various camel varieties as a dairy camel weighing 600 kg produces 15-17 kg dry manure every day whilst the drought regular camel produce about 11kgs of manure [22,24,25]. As well as, consumption of 82 kg from weather-eaten zag flora (Haloxylon bungee) would end in 129 kg horse manure and 100 kg dried CM [22,26].

In North-Eastern Baluchistan (Pakistan) and Southern Afghanistan, the CM is used in the small-scale farming system as a fertilizer for the garden, Pomegranate and grape trees [22]. In addition, it combats desertification and fixes sand dunes, an innovation for bio-paper and power generation [20,25]. 

In Bolivia, a country of west-central South America, the dung of the Llama’s camelid is employed to neutralize the acidic, metal-laden water with the aid of capability of manure as a brilliant agent for filtration due to the fact of its higher fiber contents [26].

In China, the livestock manure is used in terms of energy and heat for biogas production in relation to animal feed technology [27-29]. According to FAO statistic [11], the livestock manure provided 115 Mt annually, only 27 MT that was applied as fertilizers (Figure 3).

Globally, the level of livestock development is 0.6 per annum, but for the period 2008-2017 it was 1.3% per annum because the livestock population was 75% higher during that time [10-11]. Regionally, CM is going waste especially in locations with high camel density per unit area such as in the Emirates (UAE), Bahrain and Qatar [19]. Locally, i.e. in the KSA, livestock dung without separation from solid waste material and municipal waste in years from 2007 to 2012 was increased from 12.5 million to 15.2 million tons [30]. Therefore, the CM production (volume and type) is reasonable and the camel rearing enterprise fits well with such necessities due to data availability assessments, as the livestock growth is high especially in Asia (Figure 3 and 4).

Livestock manure assessment in waste-to-energy potential

Livestock manure can be turned into nutrients, composts and fertilizers of various kinds if properly and wisely handled [22,24,26] as only 9% of the total biomass generated by livestock is estimated worldwide for biogas recovery [26,31]. Still, the use of livestock manure as organic fertilizer and fuel is common in developing countries [11,25,28], but manure trade is less common in the crop-livestock sector of the KSA, as the region is in need for an accurate geographic estimation of the current biomass resources available in Saudi Arabia.

Other than end-use applications [25,27-29], the possibilities for converting CM to energy are plentiful and can include a wide range of camel biological product sources, and conversions technologies.

Biomass is the only sustainable organic petroleum substitute due to its high volatility and high reactivity, partly due to its generally high moisture content and high oxygen content, which provides the necessary benefits as a combustion feedstock [32,33]. However, biomass contains less carbon and extra gas that of a low heating worth than the fossil fuels [34]. As well as, biomass co-firing helps coal firing and reduces GHG emission and electricity generation costs [32,34]. Even the meat and milk production system for peri-urban camel farming is growing today in several cities in Saudi Arabia where the selling of the previous products is a critical economic activity as a consumer-oriented process, reflecting the diverse roles of camels with gradual market integration. In addition, the expansion of the KSA economy affects camel farming system [35,36].

Approximately 150 million tons of cow-dung is currently used worldwide as fuel and India accounts for 40% of the total [33]. Therefore, the new cost-effective and eco-friendly energy techniques for the use of livestock waste biomass for energy generation are required as a remedial measure. On the contrary, researchers have found that camel dung has almost the same value as that of cow dung [24,33]. Dried cow-dung [33] has been used in many countries to produce electricity (calorific value 14 MJ / kg), as it generates the same amount of fuel energy as dried firewood (calorific value 16-20 MJ / kg).

Nevertheless, biomass is an abundant, naturally occurring source of energy, and one that is also carbon-neutral, i.e. it generates an equal amount of carbon dioxide to that it consumes; biomass can therefore play a key role in meeting energy requirements [32,33]. Although biomass energy has a long history of satisfying the basic illumination, heating and cooking needs of humanity, its capacity as an electrical source has been steadily developed since the oil crisis in different parts of the world [31].

In the KSA, as the state of electricity grid provide electrical supply for just 80% for population in general [4,37]. KSA has planned to double its energy capacity up to 120GW by investing $117 billion in the power sector over the next 25 years [7], while the biomass energy is the third-largest global source of energy, among the primary energy sources after coal and oil, comprising up to 40%-50% of vitality utilization in numerous creating nations like India [33]. Globally, 64% is the major share of biomass energy from wood and wood squanders, 24% MSW, 5% agricultural waste, and 5% landfill gases [37,38].

Conversion of biomass technologies: Possible Process Overview

There are three main processes’ technologies used to convert biomass to energy [30,31]: thermochemical, biochemical, and physiochemical (Figure 5).

Conversion of biomass to energy: Scope of practice options

General background information in the previous section (Figure 5) provides a brief overview of the energy transformation options. Biomass provides more than 10% of global energy consumption and 35 million tons of manure feedstock form USA annually [9]. However, many international corporations, like the AGRO-EKO, have been engaged in animal manure to extract energy from the biological waste products that would be best-utilized on-farm or close to the source [25]. Therefore, CM quality for engineering choices will rely on the chemical, biological and physical properties of biomass and the major organic components of biomass could be categorized as cellulose, hemicelluloses, and lignin, so that atmospheric CO₂ and C-neutral are simply recycled [8,39,40,41]. Nevertheless, we present data for the surplus and undiscovered domesticated CM from the general worldwide and regional knowledge by FAO (2019) statistic (Figure 6). Figure (7) provides an overview of feasible and predictable future uses of camel biomass as a renewable capacity for assembly of biofuels, heat generation, other generations, other chemicals, and alternative materials.