Microalgae biofuel is expected to be an ideal alternative to fossil fuels to mitigate the effects of climate change and the energy crisis. However, the production process of microalgae biofuel is sometimes considered to be energy intensive and uneconomical, which limits its large-scale production. Several cultivation systems are used to acquire feedstock for microalgal biofuels production. The energy consumption of different cultivation systems is different, and the concentration of culture medium (microalgae cells contained in the unit volume of medium) and other properties of microalgae vary with the culture methods, which affects the energy consumption of subsequent processes. This review compared the energy consumption of different cultivation systems, including the open pond system, four types of closed photobioreactor (PBR) systems, and the hybrid cultivation system, and the energy consumption of the subsequent harvesting process. The biomass concentration and areal biomass production of every cultivation system were also analyzed. The results show that the flat-panel PBRs and the column PBRs are both preferred for large-scale biofuel production for high biomass productivity.

This comprehensive study unveils the vast global potential of microalgae as a sustainable bioenergy source, focusing on the utilization of marginal lands and employing advanced machine learning techniques to predict biomass productivity. By identifying approximately 7.37 million square kilometers of marginal lands suitable for microalgae cultivation, this research uncovers the extensive potential of these underutilized areas, particularly within equatorial and low-latitude regions, for microalgae bioenergy development. This approach mitigates the competition for food resources and conserves freshwater supplies. Utilizing cutting-edge machine learning algorithms based on robust datasets from global microalgae cultivation experiments spanning 1994 to 2017, this study integrates essential environmental variables to map out a detailed projection of potential yields across a variety of landscapes. The analysis further delineates the bioenergy and carbon sequestration potential across two effective cultivation methods: Photobioreactors (PBRs), and Open Ponds, with PBRs showcasing exceptional productivity, with a global average daily biomass productivity of 142.81mgL^-1d^-1, followed by Open Ponds at 122.57mgL^-1d^-1. Projections based on optimal PBR conditions suggest an annual yield of 99.54 gigatons of microalgae biomass. This yield can be transformed into 64.70 gigatons of biodiesel, equivalent to 58.68 gigatons of traditional diesel, while sequestering 182.16 gigatons of CO₂, equating to approximately 4.5 times the global CO₂ emissions projected for 2023. Notably, Australia leads in microalgae biomass production, with an annual output of 16.19 gigatons, followed by significant contributions from Kazakhstan, Sudan, Brazil, the United States, and China, showcasing the diverse global potential for microalgae bioenergy across varying ecological and geographical landscapes. Through this rigorous investigation, the study emphasizes the strategic importance of microalgae cultivation in achieving sustainable energy solutions and mitigating climate change, while also acknowledging the scalability challenges and the necessity for significant economic and energy investments.

A shortened version of Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS) for determining the dissipation and residue of imidacloprid present in Zizania latifolia and purple sweet potato was established by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The average recoveries of imidacloprid in the two crops ranged from 82.12 to 113.79%, with relative standard deviation (RSD) of <7.32%. The dissipation dynamics of imidacloprid in Z. latifolia plants and purple sweet potato plants followed first-order kinetics, with half-lives of 3.2–5.5 days in each of sampling locations. The terminal imidacloprid residues in Z. latifolia and purple sweet potato at each of location were <0.005–0.120 mg kg⁻¹. According to the risk assessment results, both the acute dietary risk quotient and chronic dietary risk quotient values were <1, indicating that imidacloprid is unlikely to pose health risks to humans with normal recommended use. The present study may serve as a valuable reference for the safe and reasonable use of imidacloprid in Z. latifolia and purple sweet potato fields.

Reducing soil evaporation by different agricultural practices is important not only for water saving but also for its applicability by farmers. In wheat fields, the goal of efficient water management is to save water and increase yield. At present, the combined effects of maize-straw mulching (M) and crop density (D) on soil evaporation and temperature, wheat performance, and water use efficiency (WUE) are not clear. A field experiment was conducted for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). The two levels of crop density included high (HD) and normal density (ND), and the three levels of mulch included high (HM), low (LM), and no mulch (NM). The results indicated that both straw mulching and high crop density had significant inhibitory effects on soil evaporation. Normal crop density with high mulch gave the lowest yield among all treatments because high mulching reduced the soil temperature and hindered the soil temperature increase in early spring. Compared with normal crop density with no mulch, the yield and WUE of winter wheat for high crop density with low mulch (HDLM) were enhanced by 20.6% and 21.9%, respectively. Compared with other treatments, HDLM gave the higher WUE due to the higher soil temperature, leaf area index, and biomass. Therefore, HDLM was an effective way to maximize the WUE of winter wheat in the NCP.