Sustainable coastal halophyte farming for biofuel in arid regions: Site
and feedwater selection using geochemical modelling
Abstract
Halophyte agriculture in marginal soils using saline water offers a
sustainable solution for generating biomass feedstock for carbon-neutral
aviation biofuels. A full-scale sustainable energy and agriculture
system (SEAS) demonstration is planned for the Abu Dhabi coast, where
evaporitic gypsiferous soils pose a challenge to long-term operation
because of the potential for land degradation. In this study,
geochemical modelling on the Geochemist’s Work Bench (GWB®) platform was
employed to: (1) Evaluate the feasibility of using coastal groundwater
versus seawater as irrigation feedwater; (2) determine the change in
agricultural return water salinity through site-specific soils upon
different seawater irrigation rates; and, (3) assess mineral deposition
effects in the soil column as a function of site-specific soil
characteristics at candidate sites over a one-year period of continuous
seawater irrigation. Evaporation modelling was used to evaluate
potential feedwater sources while varying feedwater composition and
electrolyte activity coefficient models. 1-D saturated-flow
advection-precipitation/dissolution modelling was utilized to assess
return water quality and mineral deposition as a function of both the
electrolyte activity coefficient model and the mineral composition of
site-specific soils. Results pointed to seawater as the more viable
feedwater option compared to coastal groundwater because of slower onset
of precipitation. This effort demonstrated that soil type did not
influence agricultural return water salinity (except for strongly gypsic
soils) but influenced mineral precipitation under surficial evaporation
conditions. Porosity loss correlated with layers of mineral deposition.
The study points to the need for careful selection of land and saline
water resources for the sustainable farming of halophytes.