Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2021

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Abstract

Bicarbonate was evaluated as an alternative carbon source for a green microalga, Tetradesmus wisconsinensis, isolated from Lake Norsjø in Norway. Photosynthesis, growth, and lipid production were studied using four inorganic carbon regimes: (1) aeration only, (2) 20 mM NaHCO3, (3) 5% (v/v) CO2 gas, and (4) combination of 20 mM NaHCO3 and 5% CO2. Variable chlorophyll a fluorescence analysis revealed that the bicarbonate treatment supported effective photosynthesis, while the CO2 treatment led to inefficient photosynthetic activity with a PSII maximum quantum yield as low as 0.31. Conversely, bicarbonate and CO2 treatments gave similar biomass and fatty acid production. The maximum growth rate, the final cell dry weight, and total fatty acids under the bicarbonate-only treatment were 0.33 (± 0.06) day−1, 673 (± 124) mg L−1 and 75 (± 5) mg g−1 dry biomass, respectively. The most abundant fatty acid components were α-linolenic acid and polyunsaturated fatty acids constituting 69% of the total fatty acids. The fatty acid profile eventuated in unsuitable biodiesel fuel properties such as high degree of unsaturation and low cetane number; however, it would be relevant for food and feed applications. We concluded that bicarbonate could give healthy growth and comparative product yields as CO2.

Abstract

The aim of this study was to contribute to closing global phosphorus (P) cycles by investigating and explaining the effect of fish sludge (feed residues and faeces of farmed fish) and manure solids as P fertiliser. Phosphorus quality in 14 filtered and/or dried, composted, separated or pyrolysed products based on fish sludge or cattle or swine manure was studied by sequential chemical fractionation and in two two-year growth trials, a pot experiment with barley (Hordeum vulgare) and a field experiment with spring wheat (Triticum aestivum). In fish sludge, P was mainly solubilised in the HCl fraction (66 ± 10%), commonly being associated with slowly soluble calcium phosphates, and mean relative agronomic efficiency (RAE) of fish sludge products during the first year of the pot experiment was only 47 ± 24%. Low immediate P availability was not compensated for during the second year. Thus efforts are needed to optimise the P effects if fish sludge is to be transformed from a waste into a valuable fertiliser. In manure solids, P was mainly soluble in H2O and 0.5 M NaHCO3 (72 ± 14%), commonly being associated with plant-available P, and mean RAE during the first year of the pot experiment was 77 ± 19%. Biochars based on fish sludge or manure had low concentrations of soluble P and low P fertilisation effects, confirming that treatment processes other than pyrolysis should be chosen for P-rich waste resources to allow efficient P recycling. The field experiment supported the results of the pot experiment, but provided little additional information.

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Abstract

This study evaluated the effects of bio-based carbon materials on methane production by anaerobic digestion. The results showed that biochar and hydrochar can promote cumulative methane yield by 15% to 29%. However, there was no statistical significance (p > 0.05) between hydrochar and biochar produced at different temperature on methane production. 16S rRNA gene sequencing and bioinformatics analysis showed that biochar and hydrochar enriched microorganism that might participate in direct interspecies electron transfer (DIET) such as Pseudomonadaceae, Bacillaceae, and Clostridiaceae. The the surface properties of the modified biochar were characterized with BET, Raman, FTIR and XPS. Bio-based carbon materials with uniform dispersion provided a stable environment for the DIET of microorganisms and electrons are transferred through aromatic functional groups on the surface of materials. This study reveals bio-based carbon materials surface properties on methane production in anaerobic digestion and provides a new approach to recycling spent coffee grounds.

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Abstract

Syngas from pyrolysis/gasification process is a mixture of CO, CO2 and H2, which could be converted to CH4, so called syngas biomethanation. Its development is obstructed due to the low productivity and CO inhibition. The aim of this study was to demonstrate the feasibility of using syngas as the only carbon source containing high CO concentration (40%) for biomethanation. Lab-scale thermophilic bioreactor inoculated with anaerobic sludge was operated continuously for over 900 h and the shift of microbial structure were investigated. Results showed that thermophilic condition was suitable for syngas biomethanation and the microbes could adapt to high CO concentration. Higher processing capacity of 12.6 m3/m3/d was found and volumetric methane yield of 2.97 m3/m3/d was observed. These findings could strengthen the theoretical basis of syngas biomethanation and support its industrialization in the future.

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Abstract

In-situ hydrogen biomethanation is a promising technology to upgrade biogas. The efficiency of biomethanation relies on various parameters, e.g. gas supplement, temperature and hydrogenotrophic methanogens. Therefore, it is important to investigate the characteristics of in-situ hydrogen biomethanation under different conditions. In this study, two experiments (lasted for 91 days and 105 days) were carried out to investigate the impacts of feeding gas and operating conditions on performances of reactors and microorganisms. During the whole experiment, no obvious fluctuation of pH and limitation of gas–liquid mass transfer were found. Results showed that the hydrogenotrophic methanogenesis performed better at thermophilic condition, while the dominant archaea genera at mesophilic and thermophilic temperature was determined to be Methanobacterium and Methanothermobacter, respectively. The highest CH4 content (greater than 90%) was obtained when H2 and CO2 was feeding at ratio of 4:1 and Methanothermobacter was dominant. These findings can provide useful information for promoting hydrogen biomethanation.

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Abstract

With the development of the world economy and society, the living standards of residents have been improved, along with a large amount of food waste and carbon dioxide (CO2) emissions. In the face of global warming and energy shortages, food waste can be used as high-value bio-energy raw materials which is also an effective way to reduce CO2 emissions. Therefore, this paper proposes a novel anaerobic digestion and CO2 emissions efficiency analysis based on a Slacks-Based Measure integrating Data Envelopment Analysis (SBM-DEA) model to evaluate and optimize the process structure of anaerobic treatment of food waste. The total feed volume and the discharge volume of liquid digestate are taken as inputs, and the total methane (CH4) production volume is taken as the desirable output and CO2 emissions are regarded as the undesirable output to build the biogas production and CO2 emissions evaluation model during the anaerobic digestion process. Finally, the proposed method is used in the actual anaerobic digestion process. The results show that the overall efficiency values in January, April, May, and June in 2020 are higher than those in other months. At the same time, due to the optimal allocation of slack variables of inputs and undesirable outputs, the efficiency values of other inefficient anaerobic digestion days can be improved.

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Abstract

Power-to-methane technology is a promising solution to facilitate the use of excess variable renewable energy for biomethane production. In this approach, hydrogen produced via electrolysis is used to upgrade raw biogas, which can be subsequently used as fuel or stored in the gas grid. Ex-situ biomethanation is an emerging technology that could potentially replace conventional energy-intensive biogas upgrading methods and allow CO2 utilization for biomethane production. This work provides a comprehensive overview on the current status of ex-situ biomethanation with particular attention to trickle bed reactor. The review includes description of ex-situ biomethanation and summarizes previous works on this topic. The key elements related to operational conditions, efficiency, and microbiology of ex-situ biomethanation using trickle bed reactor are described here. Additionally, the review highlights the technical and economic issues that have to be addressed for future development and large-scale implementation of ex-situ biomethanation.