Water scarcity severely affects drylands threatening their food security, whereas, the oil and gas industry produces significant and increasing volumes of produced water that could be partly reused for agricultural irrigation in these regions. In this review, we summarise recent research and provide a broad overview of the potential for oil and gas produced water to irrigate food crops in drylands. The quality of produced water is often a limiting factor for the reuse in irrigation as it can lead to soil salinisation and sodification. Although the inappropriate use of produced water in irrigation could be damaging for the soil, the agricultural sector in dry areas is often prone to challenges in soil salinity. There is a lack of knowledge about the main environmental and economic conditions that could encourage or limit the development of irrigation with oil and gas effluents at the scale of drylands in the world. Cheaper treatment technologies in combination with farm-based salinity management techniques could make the reuse of produced water relevant to irrigate high value-crops in hyper-arid areas. This review paper approaches an aspect of the energy-water-food nexus: the opportunities and challenges behind the reuse of abundant oil and gas effluents for irrigation in hydrocarbon-rich but water-scarce and food-unsecured drylands.

Nutrients and water found in domestic treated wastewater are valuable and can be reutilized in urban agriculture as a potential strategy to provide communities with access to fresh produce. In this paper, this proposition is examined by conducting a field study in the rapidly developing city of Hyderabad, India. Urban agriculture trade-offs in water use, energy use and GHG emissions, nutrient uptake, and crop pathogen quality are evaluated, and irrigation waters of varying qualities (treated wastewater, versus untreated water and groundwater) are compared. The results are counter-intuitive, and illustrate potential synergies and key constraints relating to the food–energy–water–health (FEW–health) nexus in developing cities. First, when the impact of GHG emissions from untreated wastewater diluted in surface streams is compared with the life cycle assessment of wastewater treatment with reuse in agriculture, the treatment-plus-reuse case yields a 33% reduction in life cycle system-wide GHG emissions. Second, despite water cycling benefits in urban agriculture, only <1% of the nutrients are able to be captured in urban agriculture, limited by the small proportion of effluent divertible to urban agriculture due to land constraints. Thus, water treatment plus reuse in urban farms can enhance GHG mitigation and also directly save groundwater; however, very large amounts of land are needed to extract nutrients from dilute effluents. Third, although energy use for wastewater treatment results in pathogen indicator organism concentrations in irrigation water to be reduced by 99.9% (three orders of magnitude) compared to the untreated case, crop pathogen content was reduced by much less, largely due to environmental contamination and farmer behavior and harvesting practices. The study uncovers key physical, environmental, and behavioral factors that constrain benefits achievable at the FEW-health nexus in urban areas.

The effluent of food waste (FWE) is generated during food waste treatment process. It contains high organic matter content and is difficult to be efficiently treated. In this study, the sample was collected from a 200 t/d food waste treatment center in Hangzhou, China. Subcritical and supercritical water gasification were employed to decompose and convert FWE into energy. The effects of reaction temperature (300–500 °C), residence time (20–70 min) and activated carbon loading (0.5–3.5 wt%) on syngas production and the remaining pollutants in liquid residue were investigated. It was found that higher reaction temperature and longer residence time favored gasification and pollutant decomposition, resulting in higher H₂ production and gasification efficiencies. It is noteworthy that the NH₃-N was difficult to be converted and removed under current experimental conditions. The addition of activated carbon was found to increase the gasification efficiency. The highest total gas yield, H₂ yield, carbon conversion efficiency, gasification efficiency, total organic carbon removal efficiency and chemical oxygen demand removal efficiency were obtained from gasification at 500 °C for 70 min with 3.5 wt% activated carbon.

The Maltese Islands food-water-energy nexus faces substantial challenges. These include increasing levels of land fragmentation and abandonment, an aging farming population and decreasing returns possible for remaining, often part-time, farmers. Demand for high quality, locally produced vegetables and seafood from natives, tourists and migrants continues to increase while production shrinks in the context of a rich traditional food culture. The country’s aquaculture sector also faces serious obstacles with exports facing tough competition and the tuna fattening industry dwindling because of reduced quotas. Water resources are also very scarce. Malta has no lakes or rivers and ground water is becoming increasingly brackish because of over-extraction, In terms of water resources per inhabitant, Malta is the most water stressed country in Europe and one of the ten most water-short countries in the world. Domestic supply of water is highly dependent on desalinization – an energy intensive process. Moreover, 90% of groundwater is of poor status and unfit for drinking because of nitrate pollution. This paper uses Malta as a case study to scope the potential of aquaponics to meet the complex demands of an economy with a high standard of living but extreme water-scarcity. Aquaponics – a closed cycle, soil-less method of cultivating crops that is highly water efficient and can reuse the limited effluents from intensive fish culture as a nutrient source, is assessed.

Report submitted to Food and Agriculture Organization (FAO) under the project, "Comparative assessment of water usage and impacts arising from biofuel projects in SOUTHEAST ASIAn Countries?, commissioned by the Letter of Agreement No LOA/RAP/2009/38. Thailand and Malaysia are two SOUTHEAST ASIAn countries with rapidly growing biofuel demand. Increasing use of biofuel envisages reducing dependence of petroleum products for transport and mitigating environmental impacts by reducing carbon emissions. It also expects to contribute to rural development and poverty reduction. However, the impacts of expanding production of feedstock for biofuel on water supply are not well understood. This paper assesses the water footprints and impacts of sugarcane molasses and cassava based bioethanol in Thailand, and palm oil based biodiesel in Malaysia. The water footprint of a commodity or service is the water depleted in its life cycle of its production or consumption. The total water footprints of sugarcane molasses and cassava bioethanol production in Thailand are estimated to be 1,646 and 2,304 m3/tonne, respectively, and of palm oil biodiesel in Malaysia is 3,730 m3/tonne. However, the contributions from irrigation are only a small fraction --9.0, 0.7 and 0.3%-- of the total water footprints of molasses and cassava bioethanol, and palm oil biodiesel respectively. In terms of irrigation water use,cassava is a better feedstock for bioethanol production than sugarcane molasses. In Thailand, the total annual irrigation water footprints in bioethanol production --54 million m3 (mcm) for molasses and 15 mcm for cassava-- is only 0.02% of the total renewable water resources. In Malaysia, total annual irrigation water footprint of palm oil biodiesel production is only 0.001% of the total renewable water resources. A significant spatial variation of irrigation water footprints of molasses based ethanol exists across provinces in Thailand, indicating potential for reducing water footprints. The total irrigation water footprints in biofuel production in the future in both countries will also be negligible in comparison to total water availability. However, the impact of wastewater generated in the production processes can have significant impacts on quality of local water resources. A part of the waste water, called 'spent wash', is applied as fertilizer, and over use of it can affect soil and neighboring water resources. The proposed plans on biofuel production in the future can generate more 'spent wash' than that can be used in crop fields as fertilizer. Spent wash has found to have high PH value, temperature, biological and chemical oxygen contents etc. The usual practice of storing spent wash in a pond for a long period near a plant can have detrimental impact on soil, streams' and groundwater quality. In sum, this study concludes that from the perspective of quantity of irrigation water use, the increasing biofuel production does not pose a major problem in Thailand or in Malaysia, and cassava is a better feedstock than sugarcane molasses for bioethanol production. However, the quality of water resources with increasing effluents generated by the biofuel plants could be a major environmental bottleneck to guard against | Upali A. Amarasinghe, Nishadi Eriyagama, Wannipa Soda, 'Growing biofuel demand in Thailand and Malaysia: water use and impacts. Project report submitted to Food and Agriculture Organization (FAO) under the project, "Comparative assessment of water usage and impacts arising from biofuel projects in SOUTHEAST ASIAn Countries?', International Water Management Institute (IWMI), 2014