Abstract
BackgroundCompared with other general energy crops, microalgae are more compatible with desert conditions. In addition, microalgae cultivated in desert regions can be used to develop biodiesel. Therefore, screening oil-rich microalgae, and researching the algae growth, CO2 fixation and oil yield in desert areas not only effectively utilize the idle desertification lands and other resources, but also reduce CO2 emission.ResultsMonoraphidium dybowskii LB50 can be efficiently cultured in the desert area using light resources, and lipid yield can be effectively improved using two-stage induction and semi-continuous culture modes in open raceway ponds (ORPs). Lipid content (LC) and lipid productivity (LP) were increased by 20% under two-stage industrial salt induction, whereas biomass productivity (BP) increased by 80% to enhance LP under semi-continuous mode in 5 m2 ORPs. After 3 years of operation, M. dybowskii LB50 was successfully and stably cultivated under semi-continuous mode for a month during five cycles of repeated culture in a 200 m2 ORP in the desert area. This culture mode reduced the supply of the original species. The BP and CO2 fixation rate were maintained at 18 and 33 g m−2 day−1, respectively. Moreover, LC decreased only during the fifth cycle of repeated culture. Evaporation occurred at 0.9–1.8 L m−2 day−1, which corresponded to 6.5–13% of evaporation loss rate. Semi-continuous and two-stage salt induction culture modes can reduce energy consumption and increase energy balance through the energy consumption analysis of life cycle.ConclusionThis study demonstrates the feasibility of combining biodiesel production and CO2 fixation using microalgae grown as feedstock under culture modes with ORPs by using the resources in the desert area. The understanding of evaporation loss and the sustainability of semi-continuous culture render this approach practically viable. The novel strategy may be a promising alternative to existing technology for CO2 emission reduction and biofuel production.
Highlights
Compared with other general energy crops, microalgae are more compatible with desert conditions
XJ-2, and P. falcata XJ-176 were 59, 41, and 19 mg L−1 day−1 (12, 8, and 4 g m−2 day−1, Additional file 5: Table S4), Net energy ratio (NER) and energy balances NER is defined as the ratio of the energy produced over primary energy input as represented in Eq (9): NER = Energy produced/
We confirmed that lipid content (LC) was significantly increased in the open runway pool (1000 L), and with industrial salt induction
Summary
Compared with other general energy crops, microalgae are more compatible with desert conditions. Microalgae cultivated in desert regions can be used to develop biodiesel. Microalgae are increasingly considered as feedstock for next-generation biofuel production because of their many excellent characteristics, such as broad environmental adaptability, short growth period, high photosynthetic efficiency, and high-quality lipid [3, 4]. The commercial feasibility of microalgal biodiesel is limited because only few microalgal strains can be grown reliably with high lipid content (LC) outdoors. Large-scale outdoor cultivation using sunlight is the only solution for the sustainable industrial production of microalgal biofuel [8]. An essential prerequisite to achieve the industrial-scale application of microalgal biofuel is the selection of robust and highly productive microalgal strains with relatively high LC outdoors
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