Implemented by: Flemming
Main findings: The project saves at least 227 t CO2e per year when full production is reached.
The JPO replaces diesel. To assess the CO2 savings resulting from
substituting diesel with JPO it is necessary to estimate both the diesel
that is being displaced as well as the carbon expenses involved in the
production of Jatropha. As explained in the following a number of
factors like transport fuel costs are of the same size whether diesel of
JPO is used and can therefore be omitted from the calculations.
The current area planted with Jatropha is the equivalent of 600 ha. It
is expected that at maturity the yield will be 800 kg/ha, resulting in a
total production of 480 t/y of dry Jatropha seeds. 96,000 l JPO can be
extracted from the seeds. The weight of 96,000 l JPO is 88 t.
JPO has an energy density of 39.5 MJ/kg and diesel 48 MJ/kg so 96,000 l
JPO can substitute 79,000 l diesel. The weight of 70,000 l diesel is 66 t.
The diesel that is being displaced is currently obtained in Pemba and
transported on mini busses and old pick-up trucks. The pick-up trucks
can typically load 1 t. The truck used by BBC carries 4 t. The fuel
consumption of the pick-up trucks is estimated to be 1 l per 8 km.
Through the use of GIS, modelling and custom made transport planning
software it was found that the BBC truck has to drive 16,760 km/y to
collect the 480 t, which consumes 3,258 l diesel.
To transport the equivalent amount of diesel, i.e. 66 t from Pemba to
Bilibiza using the local pick-up trucks requires 66 trips of a total of
13,200 km (counting only one-way because the cost of the return trip is
paid for by transporting other goods). This results in a fuel
consumption of 1650 l diesel. Using JPO instead of diesel therefore
requires 1,600 l/y extra diesel for transport. This is equivalent to
1,945 l JPO or 2.1 t JPO.
Another factor to consider is the effect of Jatropha cultivation on the
carbon balance in the fields. Research undertaken in collaboration with
University of Copenhagen found that if forest is cleared to give place
for Jatropha then large amounts of carbon is lost. However, farmers are
not clearing forest to plant Jatropha but instead replace existing
hedges with Jatropha.
The long term carbon build up under Jatropha hedges is probably similar
to what would occur if the hedges still consisted of common local woody
species. However, export of nutrients through harvesting of Jatropha
needs to be considered:
The traditional hedges are pruned for firewood and plants like chilli
and medicinals are harvested in small qualities. Jatropha is harvested
too but due to the low utility value of the wood the prunings are mostly
left in situ. The harvesting of seeds will probably at maturity
represent a larger drain of nutrients than the harvesting from
traditional hedges and this could with time lead to slower soil carbon
build up under Jatropha compared to traditional hedges. However, this is
counteracted by the use of Jatropha press cake as manure which returns
most of the nutrients and carbon to the fields. In practise the press
cake will often not be applied on Jatropha hedges but in higher value
crops. This does, however, not affect the balance at the farming system
level. Overall it is therefore reasonable to assume that there is no net
effect on the soil carbon balance from the cultivation of Jatropha with
the current practise. The effect on soil carbon can therefore be omitted
from the calculations.
Also farmers are not using any fertiliser, manure or pesticide for the
Jatropha, so these factors can be omitted too.
It takes energy to extract and process the Jatropha oil. The Sayari
press can process 70 kg Jatropha seeds per hour into 14 l JPO. The
generator powering the press consumes about 1 litre diesel per hour. JPO
has an energy density of 39.5 MJ/kg and diesel 48 MJ/kg so 1 l diesel
can be substituted by 1.2 l JPO. In other words 8.6% of the expelled oil
is used for processing so the annual JPO production of 96 t, 87.7 t will
be available. Deducting the 1.2 t JPO to cover the extra transport needs
86.5 t are left to substitute diesel consumption. In terms of energy
content that is equivalent to 71 t diesel.
Green House Gas savings are measured in Carbon Dioxide Equivalent
(CO2e). According to DEFRA (2010) one t diesel is equal to 3.2 t CO2e.
The 71 t diesel that is being substituted by the project at full
production is therefore equal to 227 tCO2e/y.
It can be questioned if it is reasonable to use fossil fuel in Pemba as
a benchmark. By doing so the energy used to extract the fossil fuel,
refining it and transporting it to Pemba is omitted. If that was
included the CO2e savings calculated for the project would be