Suitability of Opuntia ficus-indica (L) Mill. and Euphorbia tirucalli L. as energy crops for anaerobic digestion

Abstract

Decentralised energy from feedstock cultivated on marginal land can address various problems of many developing countries. Plants like Opuntia ficus-indica (L) Mill. (Cactaceae) and Euphorbia tirucalli L. (Euphorbiaceae) are adapted to thrive on marginal land and hence ideal for feedstock production without competing for arable land. This study explored the potential of intensive cultivation of these plants under various planting densities on marginal land blocks, each having an area of 900 m2, and compared the specific methane production potential of their biomass. Biomass samples from the wild mother plants and those from the cultivated blocks were analysed for their elemental and plant composition. The Hohenheim Biogas Test (HBT) was employed to test their biogas/methane yield potential of the biomass samples. The study showed that high density planting did not negatively affect the plant growth and biomass production. During four month growth time, the plantations at highest density (Euphorbia tirucalli at 266667 plants/ha and Opuntia ficus-indica (L) Mill. at 20.000 plants/ha) were able to generate a methane yield of approximately 1791 m³ in the case of Euphorbia tirucalli L. and 1860 m³ in the case of Opuntia ficus-indica (L) Mill. from 1 ha of marginal land.