Implemented by: Flemming Nielsen (FACT/Banana hill)

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 significantly higher.