Agricultural applications

The agro-industrial activities related to the three most cultivated palm tree species worldwide namely, oil palm, date palm, and coconut palm generate a large amount of residues during pre- and post-harvest processes. Residues include empty fruit bunches, palm kernel shells, trunks, fibers, husks, leaves, and others. If left unmanaged, the accumulation of these wastes can cause environmental nuisance and pest spread to healthy palm trees. On the other hand, crop intensification has led to soil depletion and degradation that could only be sustainably remediated by exogenous supplies of organic materials. In this regard, the incorporation of farm manures and plant residues have been practiced since ancient times to improve soil properties and crop yield. Accordingly, the agricultural valorization of palm tree residues could offer a sustainable practice for waste recycling within the concept of circular economy. While the easiest agricultural practice has been the direct incorporation of raw plant materials (bulk or shredded) into croplands, the lignocellulosic nature of these organic wastes and high C:N ratios decrease their mineralization rate in amended soils. In addition, various palm pests could use these residues as host materials and vectors to infect healthy trees. However, using cocopeat as growth substrate for hydroponics is particularly considered a successful way to valorize raw husks and fibers from coconuts. Composting palm residues by enhancing the aerobic degradation of organic materials is another process that produces a more stable biofertilizer with better physico-chemical and hygienic properties. This process could be further improved by adding animal wastes to palm residues so as to balance the C:N ratio of the feedstock and obtain a more nutrient-rich material. The thermochemical conversion of palm residues through pyrolysis largely reduces the volume of raw materials and generates both energy and biochar. The latter could be also applied to agricultural soils to improve mostly their physical properties including water retention and nutrient retention/release capacity.