Aquatic plant Azolla as the universal feedstock for biofuel production

Abstract

BackgroundThe quest for sustainable production of renewable and cheap biofuels has triggered an intensive search for domestication of the next generation of bioenergy crops. Aquatic plants which can rapidly colonize wetlands are attracting attention because of their ability to grow in wastewaters and produce large amounts of biomass. Representatives of Azolla species are some of the fastest growing plants, producing substantial biomass when growing in contaminated water and natural ecosystems. Together with their evolutional symbiont, the cyanobacterium Anabaena azollae, Azolla biomass has a unique chemical composition accumulating in each leaf including three major types of bioenergy molecules: cellulose/hemicellulose, starch and lipids, resembling combinations of terrestrial bioenergy crops and microalgae.ResultsThe growth of Azolla filiculoides in synthetic wastewater led up to 25, 69, 24 and 40 % reduction of NH4–N, NO3–N, PO4–P and selenium, respectively, after 5 days of treatment. This led to a 2.6-fold reduction in toxicity of the treated wastewater to shrimps, common inhabitants of wetlands. Two Azolla species, Azolla filiculoides and Azolla pinnata, were used as feedstock for the production of a range of functional hydrocarbons through hydrothermal liquefaction, bio-hydrogen and bio-ethanol. Given the high annual productivity of Azolla, hydrothermal liquefaction can lead to the theoretical production of 20.2 t/ha-year of bio-oil and 48 t/ha-year of bio-char. The ethanol production from Azolla filiculoides, 11.7 × 103 L/ha-year, is close to that from corn stover (13.3 × 103 L/ha-year), but higher than from miscanthus (2.3 × 103 L/ha-year) and woody plants, such as willow (0.3 × 103 L/ha-year) and poplar (1.3 × 103 L/ha-year). With a high C/N ratio, fermentation of Azolla biomass generates 2.2 mol/mol glucose/xylose of hydrogen, making this species a competitive feedstock for hydrogen production compared with other bioenergy crops.ConclusionsThe high productivity, the ability to grow on wastewaters and unique chemical composition make Azolla species the most attractive, sustainable and universal feedstock for low cost, low energy demanding, near zero maintenance system for the production of a wide spectrum of renewable biofuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0628-5) contains supplementary material, which is available to authorized users.

Growth performance and biochemical profile of Azolla pinnata and Azolla caroliniana grown under greenhouse conditions

“…Azolla is one of the fastest growing plants capable of doubling its biomass in 5-6 days [11]. In the present study, A. pinnata showed higher growth performance than A. caroliniana considering the average plant growth percentage and RGR values and the biomass-doubling time.…”

“…The use of wastewater as a source of reclaimed water would significantly reduce the cost and impact on the environment. Since the utilization of wastewater is very limited for most terrestrial crops, attention has shifted towards the use of aquatic plants [11]. Azolla species are one of the world's most economically important macrophytes [12] because of their high growth rates, high biomass production, bioremediation capacity, easy maintenance and easy harvest [13].…”

Liquid fuel generation from algal biomass via a two-step process: effect of feedstocks

“…As an important biomass category, algae, which has adapted to living in aquatic environments (saltwater or freshwater), has emerged as a promising alternative to fossil fuels as it does not compete with edible crops and food and can generate larger amounts of lipid than terrestrial biomass. In addition, the sustained removal of algae will generally benefit the nutrient balance and native ecology of the affected aquatic ecosystems [ 3 ]. Therefore, algae present a particularly promising feedstock for future biofuel production.…”

Temporary freshwater wetlands floristics in central Mexico highlands

“…Tagetes lucida has medicinal properties as anti-depressive (Bonilla-Jaime et al 2015) and T. micrantha has diverse medicinal properties (Linares & Bye 1987). Biofilter/ biofuel: Azolla filiculoides and A. microphylla are attractive species for the production of renewable biofuels (Miranda et al 2016). Egeria densa can remove heavy metals from the environment (Tsuji et al 2017), as can Eleocharis aciculares, E. macrostachya, and, E. montana (Ha et al 2011, Olmos-Márquez et al 2012.…”