One Up to now, corn and sugarcane are

One 
requirement  for  sustainable development is  the 
availability  of  adequate 
energy  services  for satisfying  basic 
needs,  improving  social 
welfare,  and achieving  economic development  (Rogner et 
al. 2004) .The best option for African countries including Tanzania to
meet rural energy needs is to grow on a massive scale in waste lands Care-free
growth,regenerative CAM plants Agave and Opuntia.

Up to now, corn and sugarcane
are used in the biofuel production. In the debate on food vs fuel, it is
necessary to find alternatives. With the highest amount of ethanol produced in
the world still derived from food crops such as corn and sugarcane, speculators
have argued that using such crops for fuel can drive up the price of food.

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Presently, about
80% of total global energy share is contributed by fossil fuels, whereby
transportation sector consumes the main part of it (REN21, 2014). These fuels
main component is hydrocarbon include things such as petroleum, coal or natural
gas derived from organic matter accumulated over time. The main issue with
these sources of fuels is the fact that they are non-renewable and therefore
can be exhausted. By 2100 the global fossil fuel reserve is projected to be
depleted (Saxena et al., 2009). Other issues include generation of greenhouse
gaseous leading to global warming and consequently climate change and its impacts.
Never the less there is also price fluctuation, which make the word insecure
with the available energy.

The search for
renewable energy source of energy, which is safer and easily available is
currently a necessity (Moshi et al 2014a). 
Such energies include among other biofuels, which are favoured alternative
to fossil fuels (Moshi, 2015).

Biofuel stands for a wide range of fuels, which are in some way derived from
biomass. This include biomasses,fuels and biogases.When it comes to their
classification biofuels can be classifies as the first ,second, third, and
fourth generations( Davis S 2012 ). Food crops rich in sugar or starch or
vegetable oil are the ones producing first generation biofuel (Davis S 2012).
The second generation biofuels are produced from residual non-food parts of
current crops, such as stems, leaves and husks that are left behind once the
food crop has been extracted, as well as other crops that are not used for food
purposes. The third generation biofuels are obtained from algae (Ziolkowska and Simon 2011b). The major drawback of the first generation biofuel crops is that
they are important food crops and their use for fuel can have adverse impacts
on food supply further more these crops are intensive in the use of one or more
inputs such as land, water, fertilizers, pesticides, etc., which have other environmental implications (Ziolkowska
and Simon 2011b).

These fuels produced
by microorganisms include bioethanol, biobutanol, biodiesel, biogas, and
biohydrogen (Nigam and Singh, 2011). Among these bioethanol, biogas and
biodiesel are the ones, which are mostly produced at commercial scale.

Biogas is a renewable source of energy
that belongs to the category of biofuels. It typically refers to a gas produced
by the biological breakdown of organic matter in the absence of oxygen. The anaerobic
digestion of biodegradable materials such as biomass, manure, sewage, municipal
waste, green waste, plant material and crops produces biogas.

 The composition of the gas is methane (CH4)
and carbon dioxide (CO2) and may have small amounts of hydrogen
sulphide (H2S), moisture and siloxanes. (Chynoweth et al., 2001) Gases methane, hydrogen and carbon monoxide (CO) can be combusted
or oxidised with oxygen. This energy release allows biogas to be used as a fuel
for any heating purpose, such as cooking. On top of that this gas can be used
in a gas engine converting the energy in the gas into electricity and heat (Moshi, 2015). Like
natural gas biogas can be compressed and used to power motor vehicles. Bio
methane can be made from it through cleaning and upgrading it to natural gas
standards. The nutrient-rich digestate that is left by biogas or anaerobic
digestion process can be used as fertiliser.

Challenge that
arises in the use of biogas as a transport fuel is mainly due to the cost of
feedstock, which takes more than 50% of the total cost of biogas production (Moshi
et al., 2014a). The main feedstock for biogas production are crops which are
also required for other applications such as food and feed. This necessitate
more researches to find inedible feedstocks.

There are option or
solution to this, which is identification and characterization of feedstocks
which, are not used as food but also cheap and readily available in the environment.
With the increasing hotter climate conditions drought resistant crops have become
more attractive as feedstock one of them the essentially spineless, fast-growing Opuntia ficus-indica (L.) Mill. (Figure 1).

In this study Crussulacean Acid Metabolism (CAM) plant, Opuntia ficus indica also known as spineless cacti will be characterized as feedstock and the
effect of its different botanical fraction will be evaluated for biogas
production.     

Opuntia are known to have high water use efficiency (WUE). They have cladodes
which are covered with thick epidermis preventing water loss and their stomata closes
during the day but open at night. This has the
effect of reducing water evaporation in this plant species. These are desert
plants that can survive where nothing else can grow (Tarisse, 2008). This makes
them a suitable plant resource for climate change adaptation. Using spineless Opuntia
as an energy crop is offering serious perspectives to countries prone to
drought and relying on imports for their energy consumption (Tarisse, 2008).

Figure 1: Opuntia ficus-indica

 

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