Valorisation of Jatropha curcas waste by composting
This crop requires different pruning seasons for proper production, which generates a large amount of waste in the form of biomass.
A simple controlled composting step produces an organic solid with properties that make it suitable as a fertiliser in agriculture. The process requires mixing the waste with other agricultural waste from the fruit, thus solving several environmental problems.
Jatropha curcas is generally used for the production of bio-oil which is then transformed into biodiesel by transesterification. For intensive production, several parameters are important, notably pruning, which generates significant quantities of biomass wastes. Pruning not only increases the number of branches and therefore the number of fruits, but also makes it possible to maintain a tree shape that facilitates harvesting. This operation generates green waste rich in mineral elements (NPK). Green waste, a mixture of pruning wastes or branches and fruit peels in a ratio of 5:1, is used for composting. The mixture is homogenised and placed in a bioreactor. During composting, the reactor is fed by a flow of compressed air to ensure complete oxygenation. An automatic system continuously keeps the biomass in motion. The composting period is one month, producing a compost with the following parameters: C/N <21, NH4+/NO3- <1 and a pH between 5 and 7. Phosphorus levels increase after the fifth day of composting to reach 0.03 mg/g.
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