Baoming Li

Conversion efficiency and oil quality of low-lipid high-protein and high-lipid low-protein microalgae via hydrothermal liquefaction.

Hydrothermal liquefaction (HTL) is a promising technology for converting algae into biocrude oil. Here, HTL of a low-lipid high-protein microalgae (Nannochloropsis sp.) and a high-lipid low-protein microalgae (Chlorella sp.) was studied. An orthogonal design was applied to investigate the effects of reaction temperature (220-300°C), retention time (30-90 min), and total solid content (TS, 15-25%wt) of the feedstock. The highest biocrude yield for Nannochloropsis sp. was 55% at 260°C, 60 min and 25%wt, and for Chlorella sp. was 82.9% at 220°C, 90 min and 25%wt. The maximum higher heating values (HHV) of biocrude oil from both algae were ∼ 37 MJ/kg. GC-MS revealed a various distribution of chemical compounds in biocrude. In particular, the highest hydrocarbons content was 29.8% and 17.9% for Nannochloropsis and Chlorella sp., respectively. This study suggests that algae composition greatly influences oil yield and quality, but may not be in similar effects.

Effects of furan derivatives on biohydrogen fermentation from wet steam-exploded cornstalk and its microbial community

Understanding the role of furan derivatives, furfural (FUR) and 5-hydroxymethyl furfural (HMF), is important for biofuel production from lignocellulosic biomass. In this study, the effects of furan derivatives on hydrogen fermentation from wet steam-exploded cornstalk were investigated. The control experiments with only seed sludge indicated that HMF addition of up to 1g/L stimulated hydrogen production. Similar results were obtained using steam-exploded cornstalk as the feedstock. Hydrogen productivity was increased by up to 40% with the addition of HMF. In addition, over 90% of furan derivatives with an initial concentration below 1g/L were degraded. Pyosequencing showed that the addition of HMF and FUR resulted in different microbial communities. HMF led to a higher proportion of the genera Clostridium and Ruminococcaceae, supporting the increased hydrogen production. This study suggested that hydrogen fermentation could be a detoxifying step for steam-exploded cornstalk, and HMF and FUR exhibited different functions for hydrogen fermentation.

Hydrothermal liquefaction of harvested high-ash low-lipid algal biomass from Dianchi Lake: effects of operational parameters and relations of products.

Hydrothermal liquefaction (HTL) allows a direct conversion of algal biomass into biocrude oil, not only solving the environmental issues caused by the over-growing algae but also producing renewable energy. This study reports HTL of algae after separation from eutrophicated Dianchi Lake in China. Conversion efficiency was studied under different operational conditions via an orthogonal design, including holding temperature (HT) (260-340 °C), retention time (RT) (30-90 min) and total solid (TS) (10-20%). A highest biocrude oil yield (18.4%, dry ash-free basis, daf) was achieved at 300 °C, 60 min, and 20% (TS), due to the low contents of lipids (1.9%, daf) and proteins (24.8%, daf), and high contents of ash (41.6%, dry basis) and carbohydrates (71.8%, daf). Operational parameters significantly affected the biocrude yields, and chemical distribution of HTL products. The biocrude production also related to other HTL products, and involved chemical reactions, such as deoxygenation and/or denitrogenation.

Ultrasound-assisted hydrolysis and acidogenesis of solid organic wastes in a rotational drum fermentation system.

The hydrolysis and acidogenesis of solid organic wastes in a rotational drum fermentation system (RDFS) were improved by direct ultrasonic irradiation (DUSI) and a modified ultrasonic treatment (MUST) composed of dilution, ultrasonic irradiation, and filtration. The effect of DUSI on VA desorption from particle surfaces was estimated. DUSI delivered few distinctions from the broth characteristics, but elevated pH and VS degradation rate (53% higher than the control) in the subsequent acidogenesis. The results demonstrated that DUSI could dislodge VA from particle surfaces and disrupt large-size particles by hydro-mechanical shear force. To improve VA desorption and removal, a MUST process was constructed. The influences of MUST on the characteristics of the fermentation broth and the subsequent acidogenic performance were investigated. MUST raise the broth pH level from 5.1 to 5.5 and remarkably decreased VA concentration from 11.0 to 3.5g/L. At the end of the subsequent acidogenesis, VA increasing ratios, VS degradation ratios, and surface based hydrolysis constants of the fermentors with the control broth (CF) and the treated broth (MUSTF) were 166.7% and 732.0%, 17.0% and 26.7%, and 16.9% and 26.8x10(-6)kgm(-2)d(-1), respectively. With the assistance of MUST, a considerably improved acidogenic performance of solid organic wastes was accomplished in terms of VA production, VS degradation, and particle hydrolysis.

Recovery of reducing sugars and volatile fatty acids from cornstalk at different hydrothermal treatment severity

This study focused on the degradation of cornstalk and recovery of reducing sugars and volatile fatty acids (VFAs) at different hydrothermal treatment severity (HTS) (4.17-8.28, 190-320°C). The highest recovery of reducing sugars and VFAs reached 92.39% of aqueous products, equal to 34.79% based on dry biomass (HTS, 6.31). GC-MS and HPLC identified that the aqueous contained furfural (0.35-2.88 g/L) and 5-hydroxymethyl furfural (0-0.85 g/L) besides reducing sugars and VFAs. Hemicellulose and cellulose were completely degraded at a HTS of 5.70 and 7.60, respectively. SEM analysis showed that cornstalk was gradually changed from rigid and highly ordered fibrils to molten and grainy structure as HTS increased. FT-IR and TGA revealed the significant changes of organic groups for cornstalk before and after hydrothermal treatment at different HTS. Hydrothermal treatment might be promising for providing feedstocks suitable for biohythane production.

Performance and microbial community of carbon nanotube fixed-bed microbial fuel cell continuously fed with hydrothermal liquefied cornstalk biomass

Hydrothermal liquefaction (HTL) is a green technology for biomass pretreatment with the omission of hazardous chemicals. This study reports a novel integration of HTL and carbon nanotubes (CNTs) fixed-bed microbial fuel cell (FBMFC) for continuous electricity generation from cornstalk biomass. Two FBMFCs in parallel achieved similar performance fed with cornstalk hydrolysate at different organic loading rates (OLRs) (0.82-8.16g/L/d). About 80% of Chemical oxygen demand (COD) and Total organic carbon (TOC) was removed from low-Biochemical oxygen demand (BOD)/COD (0.16) cornstalk hydrolysate at 8.16g/L/d, whereas a maximum power density (680mW/m(3)) was obtained at 2.41g/L/d, and a smallest internal resistance (Rin) (28Ω) at 3.01g/L/d. Illumina MiSeq sequencing reveals the diverse microbial structure induced by the complex composition of cornstalk hydrolysate. Distinguished from Proteobacteria, which a number of exoelectrogens belong to, the identified dominant genus Rhizobium in FBMFC was closely related to degradation of cellulosic biomass.

Using porphyritic andesite as a new additive for improving hydrolysis and acidogenesis of solid organic wastes

The effects of porphyritic andesite on the hydrolysis and acidogenesis of solid organic wastes were investigated by batch and continuous experiments using a rotational drum fermentation system. The results of the batch experiment show that if porphyritic andesite (1%, 3%, and 5% reactants) is added initially, the pH level increases and hydrolysis and acidogenesis are accelerated. The highest surface based hydrolysis constant (26.4x10(-3) kgm(-2) d(-1)) and volatile solid degradation ratio (43.3%) were obtained at a 1% porphyritic andesite addition. In the continuous experiment, porphyritic andesite elevated the first order hydrolysis constant from 13.10x10(-3) d(-1) to 18.82x10(-3) d(-1). A particle mean diameter reduction rate of 33.05 microm/d and a volatile solid degradation rate of 3.53 g/L d(-1) were obtained under the hydraulic retention time of 4, 8, 12 and 16 d.

Modeling of water and nitrogen utilization of layered soil profiles under a wheat-maize cropping system

a b s t r a c t Understanding water and nutrient utilization in agricultural layered soil is very important for the improvement of agricultural management and protection of the environment. The objective of this paper is to determine the effect of layered soil profiles on crop yield and water and fertilizer nitrogen (N) utilization. Firstly a water and nitrogen management model (WNMM) was calibrated and validated under a wheat-maize cropping system in an alluvial plain using published data of two soil profiles (named A and B). The results showed that the model can be used to simulate the water movement and N transport, as well as crop growth in the study area. Then, another three very different soil profiles (named C, D and E) near to profiles A and B were studied. The profile C had a silt loam-clay profile; the profile D had a silty loam-clay-silt profile and the profile E had a clay-silty loam-silt profile. The soil hydraulic parameters of these profiles were obtained by pedo- transfer functions using measured soil properties. Given the same initial conditions and field management practices, the WNMM was then used to simulate water and Nitrogen balance and crop yield for the three profiles. Simulated results showed that the profiles (C, D and E) have similar water and fertilizer N use efficiencies (WUE, FNUE), while the crop yields of profiles C and D were higher than that of the profile E. Compared with profiles D and E, the profile C has least water drainage (127 mm) and total N loss (117 kg N ha − 1 ). We concluded that layering of soil profiles has a strong effect on water and fertilizer N utilization and crop yield. Such an effect of layered property of soil profiles, therefore, needs to be taken into account in precision agriculture related research.

Volatile organic acid adsorption and cation dissociation by porphyritic andesite for enhancing hydrolysis and acidogenesis of solid food wastes.

Volatile organic acid adsorption, cation dissociation by porphyritic andesite, and their effects on the hydrolysis and acidogenesis of solid food wastes were evaluated through batch experiments. The acetic acid adsorption experiments show that pH was mainly regulated by H(+) adsorption. The mono-layer and multi-layer adsorption were found under the low (8.3-83.2 mmol/L) and high (133.22-532.89 mmol/L) initial acetic acid concentration, respectively. The dissociated cations concentration in acidic solution showed the predominance of Ca(2+). Porphyritic andesite addition elevated the pH levels and accelerated hydrolysis and acidogenesis in the batch fermentation experiment. Leachate of porphyritic andesite addition achieved the highest hydrolysis constant of 22.1 x 10(-3)kgm(-2)d(-1) and VS degradation rates of 3.9 g L(-1)d(-1). The highest activity of microorganisms represented by specific growth rate of ATP, 0.16d(-1), and specific consumption rate of Ca(2+), 0.18d(-1), was obtained by adding leachate of porphyritic andesite.

Co-digestion of chicken manure and microalgae Chlorella 1067 grown in the recycled digestate: Nutrients reuse and biogas enhancement

The present investigation targeted on a sustainable co-digestion system: microalgae Chlorella 1067 (Ch. 1067) was cultivated in chicken manure (CM) based digestate and then algae biomass was used as co-substrate for anaerobic digestion with CM. About 91% of the total nitrogen and 86% of the soluble organics in the digestate were recycled after the microalgae cultivation. The methane potential of co-digestion was evaluated by varying CM to Ch. 1067 ratios (0:10, 2:8, 4:6, 6:4, 8:2, 10:0 based on the volatile solids (VS)). All the co-digestion trials showed higher methane production than the calculated values, indicating synergy between the two substrates. Modified Gompertz model showed that co-digestion had more effective methane production rate and shorter lag phase. Co-digestion (8:2) achieved the highest methane production of 238.71mL⋅(g VS)-1 and the most significant synergistic effect. The co-digestion (e.g. 8:2) presented higher and balanced content of dominant acidogenic bacteria (Firmicutes, Bacteroidetes, Proteobacterias and Spirochaetae). In addition, the archaea community Methanosaeta presented higher content than Methanosarcina, which accounted for the higher methane production. These findings indicated that the system could provide a practicable strategy for effectively recycling digestate and enhancing biogas production simultaneously.