Excessive composite pollution carbon sources enhance the bio-fertilizer efficiency of Tetradesmus obliquus: focused on cultivation period

Microalgae can use carbon sources in sludge extract prepared from sludge. Moreover, the high concentration of CO2 and the large number of carbon sources in the liquid phase will promote microalgae growth and metabolism. In this experiment, Tetradesmus obliquus was cultivated with sludge extract at 30% CO2. Algae liquid (the name used to describe the fertilizer made in this research) was further prepared as lettuce fertilizer. The effect of different times of microalgae culture (10, 15, 20, 25, and 30 days) on the fertilizer efficiency of the algae liquid was evaluated by lettuce hydroponic experiments. The findings indicate that lettuce cultivated in algae liquid collected on the 15th and 30th days exhibited superior performance in terms of growth, antioxidant capacity, and nutritional quality. We analyzed the experimental results in the context of microalgae metabolic mechanisms, aiming to contribute experience and data essential for the development of industrial microalgae fertilizer production.

Determining reclaimed water quality thresholds and farming practices to improve food crop yield: A meta-analysis combined with random forest model

Irrigated agricultural systems with reclaimed water (RW) play a crucial role in alleviating global water scarcity and increased food demand. However, appropriate reclaimed water quality thresholds and farming practices to improve food crop yield is virtually unclear. Therefore, for the first time, this study made a large compilation of previous studies using meta-analysis combined with a random forest (RF) model and analyzed the impact of RW versus freshwater (FW) on the yield of food crops (cereals, vegetables, and fruits). It was found that magnesium ion (Mg²⁺), calcium ion (Ca²⁺), electrical conductivity (EC), total nitrogen (TN), and potential of hydrogen (pH) were the most important factors for RW quality indicators. Based on the results, water managers should establish more conservative RW quality thresholds to promote food crop production, especially for salts and pollutants in RW. Compared to international water quality standards, it could be slightly relaxed the restrictions of TN in RW. The optimal farming practices obtained that irrigation amount of the mixed RW and FW (RW + FW) was from 1000 m³ ha^-1 to 5000 m³ ha^-1, and the cultivation period was no more than three years. Flood irrigation (FI) and drip irrigation (DI) for cereals were also recommended. Finally, a comparison of the determined results from this method with other scenarios published, finding a good agreement.

The influence of cultivation period on growth and biodiesel properties of microalga Nannochloropsis gaditana 1049

This work reported for the first time the detailed impacts of cultivation period on growth dynamics and biochemical composition of a microalga strain Nannochloropsis gaditana 1049. The results shown either the biomass accumulation, lipid content, neutral lipid content, monounsaturated fatty acids composition or the favorable fatty acid profile of C16-C18 increased along with the cultivation period extension, but the lipid productivity displayed a decrease since cultured for 16 days, with the highest value reached 289.51 ± 16.34 mg L(-1) d(-1). Biodiesel properties of this microalga also changed with the cultivation period extension, with average unsaturated degree decreased from 1.24 ± 0.03 to 0.59 ± 0.02, cloud point increased from 3.39 ± 0.40 °C to 12.14 ± 0.32 °C, cetane number increased from 54.59 ± 0.20 to 58.96 ± 0.16 and iodine number reduced sharply from 105.15 ± 2.24 gI2/100g to 56.44 ± 1.76 gI2/100g, which all satisfied the specifications of biodiesel standard.