On the issue of halophytes as energy plants in saline environment

Abstract

Presented paper describes findings of original researches on assessment of halophytes in Uzbekistan for biogas production. A range of wild and cultivated plants was investigated. Their development and chemical composition was observed. Good yield of halophytes in marginal environment with low-fertile sandy soils and warm mineralized irrigated water was recognized (14–44 t/ha of green biomass). Chemical content of the biomass was analyzed. Highest total salt accumulation was revealed for Salicornia, Halostachys, Kallidium and Climacoptera (35–50%DM). Suaeda, Atriplex, Kochia, Karelinia and Glycyrrhiza accumulated less amounts of mineral ions (9–26%DM). Plants grown in farm trial contained less mineral compounds as compared with the same species from solonchak (for instance, 31.6% ash versus 46.9% for Climacoptera). Na+; Cl−; SO42− was mainly accumulated in green biomass of halophytes. High nutritional value of the biomass was confirmed. Halophytes contained a big amounts of crude protein (5–13 mg/g DM); cellulose (10.38–20.54 mg/g DM); and lipids (0.5–5.06 mg/g DM). Atriplex, Suaeda and Kochia are recognized as the most nutritional valuable plants. Anaerobic digestion of halophytic biomass was studied in batch-test and continuous mode experiments; 130–366 mL of biogas was produced from 1 g DM of various halophytes at 35 °C; and 269–480 mL – at 55 °C. Taking into consideration current use of different plants, biomass yield and biogas production it is recommended to admit Karelinia caspia as the most promising source of biogas. AD-reactor daily fed by mixture of Karelinia + vegetables/fruit waste (1:1) can produce about 500 mL CH4/day from 1 L of volume (35 °C; HRT = 20; OLR = 2.65 gVS/L/day).