To address the demand for sustainable, sulfur-free fractionation, this study investigated the alkali-ethanol fractionation of Miscanthus & times; giganteus using sequential Response Surface Methodology (RSM) strategy to systematically quantify parameter interactions and optimize process performance. An initial Box-Behnken Design (BBD) was employed at low severity to screen four independent variables (temperature, time, alkali concentration and ethanol concentration), regarding their impact on pulp yield, pulp chemical composition, and xylan solubilization. Subsequently, a Central Composite Design (CCD) was used to optimize the principal process drivers (temperature and alkali concentration) at high severity. In both designs, distinct optima were identified for two specific objectives: maximizing polysaccharide yield and maximizing delignification. In the low severity regime, the predicted optimum for maximizing polysaccharide retention yielded a 73.3% pulp yield (96.9% cellulose and 92.2% xylan retention), while the delignification focused optimum achieved 83.1% lignin removal. In the high severity regime, maximizing polysaccharide yield resulted in 88.2% cellulose and 67.6% xylan retention, whereas delignification objective achieved 91.3% lignin removal. Chemical and morphological analyses confirmed that varying severity regimes and objectives produce pulps with distinct structural chemotypes. This study establishes a robust sequential RSM model that serves as a powerful tool for precisely tailoring non-wood feedstock fractionation, enabling biorefineries to switch between high yield intermediate pulps and high-purity cellulose streams based on specific market requirements.

Kinetic studies of lignocellulose fractionation clarify mechanisms of biomass deconstruction but are challenged by substrate heterogeneity. Here, flow-through biphasic OrganoCat (OrganoCatFT) was used to fractionate beech wood and Miscanthus at 140 degrees C, 160 degrees C and 180 degrees C with 5 min sampling. Monosaccharide time courses showed rapid hemicellulose breakdown: xylose dominated the aqueous phase yet remained incompletely extracted, peaking at approximately 10 min at 160 degrees C-180 degrees C and at 20-25 min at 140 degrees C. At 140 degrees C, galacturonic acid was unexpectedly abundant (approximately 26% of extracted sugars from beech; approximately 10% from Miscanthus), indicating enhanced pectin accessibility under OrganoCatFT. Glucose yields increased with temperature and exceeded native glucan contents in hemicelluloses, consistent with contributions from starch, hemicellulosic glucan and limited cellulose hydrolysis. Kinetic fitting for beech required fast and slow xylan fractions with Arrhenius activation energies of 105 kJ mol-1 (fast) and 144 kJ mol-1 (slow) and an increasing fast fraction, phi = 0.208-0.634 (140 degrees C-180 degrees C). Miscanthus yielded higher xylose at 160 degrees C (106 mg g-1 vs 37 mg g-1 at 140 degrees C) but lower at 180 degrees C (80 mg g-1) due to furfural formation; glucose stayed <= 2.4 mg g-1. Thus, biomass-specific xylan architecture governs early hydrolysis, whereas cellulose conversion is only weakly temperature dependent in this range.

The environmental impacts of aerogel synthesis from lignocellulosic residues are analyzed using the Life Cycle Assessment (LCA) approach. All steps in the process chain, cradle-to-gate, are considered: from agricultural processes to cellulose extraction, the preparation of wet-gel beads and alcogels, and aerogels obtained by drying with supercritical carbon dioxide. Two methods of cellulose extraction are discussed. Life cycle inventory was built using primary data from the laboratory and with support of the Sphera LCA for Experts software. Environmental impacts are quantified using the functional unit of 1 kg of lignocellulosic-based aerogel. The focus is to assess the contribution of each process to the overall environmental performance and to identify hotspots during production. A comparison of the individual unit operations of the process chain shows that the alcogel preparation, followed by cellulose extraction, contributes most to the overall impact. This is predominantly caused by the supply of ethanol, acetic acid and 2-methyltetrahydrofuran. As aerogel preparation was carried out on a laboratory scale, these results can be regarded as a conservative estimate and thus serve as a basis for process optimization during scale-up. With the assumed improvements during scale-up and in a scenario for 2050, significant reductions in environmental impacts can be achieved, e.g., by 87-92% in terms of the greenhouse gas balance, by 75-87% in terms of acidification and by 92-94% in terms of resource availability. However, a comparative LCA with chosen benchmarks shows that lignocellulosic-based aerogels are not yet fully competitive.

Peatlands store vast global carbon reserves but drainage for agriculture has turned them into major CO2 sources. Full rewetting without alternative production systems would threaten farm incomes and regional value chains. Markets and value chains for biomass from rewetted peatlands are still largely undeveloped, and detailed knowledge of its chemical composition and suitability for integration into existing processing industries is lacking. In this study, we systematically investigated three dominant wetland taxa, Phragmites australis, Phalaris arundinacea, and Carex spp., alongside Miscanthus × giganteus as a benchmark, focusing on their lignocellulosic characterization, lignin structure, and the performance in OrganoCat fractionation. This study aims to provide a detailed compositional characterization of peatland grasses to establish their biomass potential for applications of bio-based value chains. The peatland grasses showed lower cellulose (25%–32% vs. 42%) and in case of Carex and Phalaris also lower lignin contents (18% vs. 24%) compared to Miscanthus. The hemicellulose profiles of Miscanthus and Phragmites were dominated by xylose and arabinose, whereas Carex and Phalaris exhibited more complex mixtures indicative of more highly substituted arabinoxylans or multiple polysaccharide classes. Lignin architecture also varied: lignin–carbohydrate complex (LCC) densities were up to 25% higher in peatland grasses compared to Miscanthus. Phalaris showed more condensed G-rich lignins (20% higher than in Miscanthus) and all peatland grasses showed a reduced S/G-ratio. Carex showed a higher ferulate content contrasting Miscanthus’ less cross-linked structure. It was also demonstrated that the composition of lignin-bound polysaccharides varies substantially among the investigated grasses. Fractionation of the biomasses equilibrated the species-specific diversity of the four grasses, yielding cellulose-rich pulps with comparable composition (55%–65% cellulose) and saccharification efficiencies (>75%). This homogeneity across the processed pulps enables flexible mixed-species peatland biorefineries within multifunctional paludiculture systems prioritizing peat conservation and greenhouse gas mitigation.

Phosphorus (P) from surface waters can be captured in algal biomass, which can be used as a fertilizer. We investigated the efficiency of polyculture algal biofilms produced on municipal wastewater effluent as a P fertilizer for wheat. We asked whether arbuscular mycorrhizal fungi (AMF) and the beneficial root endophyte Serendipita vermifera influence plant performance and P uptake. Two pot experiments were performed with wheat fertilized with algal biofilms or highly available triple superphosphate (TSP) at a rate of 37 mg P kg−1, corresponding to 56.8 kg ha−1. In the second experiment, plants were inoculated with AMF (Rhizoglomus irregulare, Funneliformis mosseae, F. geosporum), S. vermifera, or both. P species contained in the algal biofilm and P release dynamics were analyzed by liquid-state 31P nuclear magnetic resonance spectrometry and leachate analyses. Algal biofilms contained high levels of orthophosphate with low water solubility. P recovery by wheat was lower than from TSP, as indicated by plant total dry matter and total P. In algae-fertilized wheat, AMF reduced growth but not P uptake, while S. vermifera in dual inoculation with AMF mitigated the adverse effects. S. vermifera significantly increased root growth and P content in roots when co-inoculated with AMF. Polyculture algal biomass is an effective, less leaching-prone organic P source for wheat. The synergistic effect of S. vermifera as a root growth-promoting fungus in its interaction with AMF shows the potential and relevance of microbial involvement in using algae-based fertilizers.

Enzymatic saccharification of plant-sourced lignocellulosic biomass is a key step in biorefinery approaches. However, these biomasses in their raw form are quite recalcitrant, which invokes the need for pre-treatment processes aimed at not only increasing glucose conversion, but also better valorising non-carbohydrate biopolymers, such as lignin. Here, we use a two-fold computational and experimental approach to investigate enzymatic saccharification time-courses for three cellulosic substrates (i.e. AVICEL, a mixture of AVICEL with Organosolv lignin, and Sigmacell), and four plant-sourced lignocellulosic biomasses following three different conditions for each of them (i.e. untreated, OrganoCat pre-treated with a swelling step, and OrganoCat pre-treated without a swelling step), making a total of fifteen samples. Considering the specific composition of each substrate, the model successfully reproduces the saccharification dynamics for each of the fifteen samples. It additionally provides values for the parameter Crystallinity Fraction that faithfully replicate the substrate Crystallinity Indices experimentally determined by ssNMR. Importantly, we show that the Crystallinity Index of distinct biomasses is differently impacted by swelling, while the sugar release is consistently impacted by pre-treatment across biomasses. Eventually, both artificial cellulosic and plant-sourced lignocellulosic biomasses demonstrate that the sugar release is the result of the combination of the Crystallinity Fraction (the model parameter for experimentally measured ssNMR Crystallinity Index) and the digestibility ratio, the model parameter that represents in a coarse-grained manner complex spatial and structural features. Overall, our results stress the need for further experimental investigations that physically explain variations in the digestibility of crystalline bonds across biomasses and pre-treatment conditions. Additionally, we supplemented our work with theoretical investigations on a generic lignocellulosic substrate to highlight the roles of various model parameters in a qualitative manner.

The isolation of high-quality lignin from lignocellulose plays a pivotal role in the holistic use of biomass. Hence, modern approaches aim to avoid recondensation reactions of lignin during extraction and aim to maintain most of the native structure. This increases its solubility and the proportion of cleavable beta aryl linkages, which can be of advantage in the subsequent process chain. As the lignin structure varies greatly between different plant groups, understanding the effect of lignin structural features on processing and vice versa is a prerequisite for industrial application. In this study, a two-step process using concentrated phosphoric acid in a swelling step and then a biphasic fractionation process utilizing diluted phosphoric acid under mild conditions was used as a benchmark to extract lignin from 10 structurally and compositionally different plant materials. Pyrolysis-gas chromatography-mass spectrometry and 1H-13C-heteronuclear single quantum correlation-nuclear magnetic resonance were used to identify the monomer unit composition and the linkage proportion of lignin before and after extraction and combined with size exclusion chromatography, wet chemical analysis of the biomass, and fractionation yields to identify correlations before and after processing. After processing, the relative beta aryl ether linkage content decreased greatly from 40-90 to 20-40 linkages per 100 monomer units. The molecular weight (M w) of extracted lignin was measured to be between 2000 and 6800 Da, indicating that the fractionation process produces relatively uniform lignin in these aspects from different plant sources. Nevertheless, lignin structure properties such as beta aryl and resinol linkages showed an influence on delignification and lignin size.

In the modern world, plastics have become indispensable. Due to their properties, they are used for a wide variety of applications ranging from packaging materials to textiles and medical technology. The vast majority of these plastics are made from finite fossil feedstocks that will need to be replaced in the long term to meet consumer demands in the future. Intensive research is being conducted into alternative bio‐based feedstocks to replace petroleum‐based plastics with more environmentally friendly variants. This includes polylactide, a polyester derived from lactic acid, which is mainly used as packaging material. In this work, star‐shaped copolymers consisting of polylactide and OrganoCat lignin with varying lignin loadings are synthesized using a “grafting‐from” approach directly from the lactide melt using a zinc‐based guanidine catalyst. This method proves to be efficient and copolymers can be produced after 30 min to three hours with high lactide conversions. Kinetic studies are performed to investigate the influence of different lignin loadings on the polymerization rate and 31P NMR experiments are used to analyze the functionalization of the lignin. Thermal analysis reveals an increase of the glass transition temperature and a higher thermal decomposition temperature with increasing lignin content.

This study adapts the biphasic OrganoCat system into a flow-through (FT) reactor, using a heated tubular setup where a mixture of oxalic acid and 2-methyltetrahydrofuran (2-MTHF) is pumped through beech wood biomass. This method minimizes solvent-biomass contact time, facilitating rapid product removal and reducing the risk of secondary reactions. A comparative analysis with traditional batch processes reveals that the FT system, especially under severe conditions, significantly enhances extraction efficiency, yielding higher amounts of lignin and sugars with reduced solid residue. Notably, the FT system shows partial hydrolysis of the cellulose, which increases with temperature while not producing significant amounts of furfural or 5-HMF, indicating more efficient depolymerization of polysaccharides without substantial sugar degradation. A statistical design of experiments (DOE) using a Box-Behnken design elucidates the influence of process variables (time, solvent flow rate, temperature) on the yield. Key findings highlight reactor temperature as the dominant factor affecting yields, with process time showing a significant but less pronounced impact. This study demonstrates the potential of the FT OrganoCat system for efficient lignocellulosic biomass fractionation and represents an advancement towards continuous lignocellulose processing, contributing to our knowledge of process optimization for improved biorefinery applications.

Poplar plays a vital role in carbon sequestration and provides valuable raw materials for various industrial applications. This study dissects the effects of genotype and nitrogen fertilization on recalcitrance features in poplar biomass towards OrganoCat pretreatment. Three genetically different poplar hybrids were cultivated for 13 weeks at greenhouse conditions and fertilized with different forms of inorganic nitrogen. Stem material was processed with different degrees of severity. Biochemical data of the biomass and OrganoCat products was used in a multiscale analysis to determine recalcitrance parameters. The relationship between nitrogen fertilization and genotype on the subsequent processing was investigated. The genotype had a greater influence on the recalcitrance of young poplars than nitrogen fertilization. Generally, crystalline cellulose content and enzymatic glucose conversion increased after processing with a higher severity. Moreover, the overall compositional variation decreased after OrganoCat processing. Optimization of nitrogen fertilization, transfer to field experiments and lignocellulose processing techniques are crucial for maximizing economic and environmental benefits of poplar plantations.

In this study, three technical-scale Algal Turf Scrubber (ATS) systems were continuously operated in a green-house over one year to evaluate the nutrient removal and recovery ability. The independent and interdependent effects of water temperature and light intensity on dependent variables, such as nutrient removal and recovery, were identified via mathematical modelling. Over 7 days, the average total nitrogen and phosphorous removal rates and efficiencies were 30.93 and 8.95 mg/L and 51.2 and 89.5 %, respectively. Based on a statistical regression matrix, the quadratic models were chosen to analyze data on nutrient removal and recovery. In this study, light intensity was the dominant variable for ATS performance. Significant positive correlations were found between nutrient removal and recovery, and biomass productivity. The annual production costs for dried algal biomass, N and P were 2.27, 40 and 156 euro kg-1, respectively. Our results indicated that the ATS technology can be efficient and cost-effective in nutrients removal and recovery from wastewaters.

Due to its ample production of lignocellulosic biomass, Sida hermaphrodita (Sida), a perennial forb, is considered a valuable raw material for biorefinery processes. The recalcitrant nature of Sida lignocellulosic biomass towards pretreatment and fractionation processes has previously been studied. However, Sida is a non-domesticated species and here we aimed at expanding the potential of such plants in terms of their processability for downstream processes by making use of the natural variety of Sida. To achieve this goal, we established a collection comprising 16 different Sida accessions obtained from North America and Europe. First, we asked whether their cell wall characteristics are reflected in genetic distance or geographical distribution, respectively. A genotyping-by-sequencing (GBS) analysis resulting in a phylogenic tree based on 751 Single Nucleotide Polymorphisms (SNPs), revealed a high genetic diversity and a clear separation between accessions collected in North America and Europe. Further, all three North American accessions were separated from each other. Of the eleven European accessions, five form individual groups and six others belong to a single group. Clonal plants of seven selected accessions of American and European origin were produced and cultivated under greenhouse conditions and the resulting plant material was used for in-depth wet-chemical and spectroscopic cell wall characterization. Two accessions with contrasting cell wall characteristics were then selected and processed using the OrganoCat technology. Results of the different product yields and chemical compositions are reported. Overall, cell wall analyses revealed contrasting clusters regarding these main components between the accessions that can be related to genetic and, partly, geographical distance. Phenotypically, the accessions clustered into two groups that are not entirely overlapping with geographical origin. These results can be the basis for a targeted selection or cultivation of Sida accessions for biorefinery approaches.

Agricultural residues such as rapeseed straw can be a valuable source of cellulose, sugars, and aromatic molecules like lignin. Understanding its composition is crucial in order to develop suitable processing technology for the production of biofuel or biochemicals from rapeseed straw. Here, we developed a small-scale OrganoCat system to screen multiple technical conditions and different samples at higher throughput and utilize this system to analyze straw samples from a set of 14 genetically different Brassica lines on their processability. Correlation analysis was performed to investigate the effects of cell wall polymer features on rapeseed biomass disintegration. At comparably mild reaction conditions, the differences in recalcitrance towards OrganoCat fractionation within the set were especially associated with parameters such as pectic polysaccharide content, acetylation, and hemicellulose composition. These findings can subsequently be used to optimize and scale up the pretreatment and fractionation of lignocellulose derived from rapeseed straw.

EDITORIAL article Front. Plant Sci., 03 October 2023Sec. Technical Advances in Plant Science Volume 14 - 2023 | https://doi.org/10.3389/fpls.2023.1284658

Small-scale agriculture and industries in remote areas often lack the access to cost-effective wastewater (WW) treatment. One techno-economical solution could be the WW treatment by algal biofilm in the Algal Turf Scrubber (ATS). Here, a systematic, and year-round case study on the efficiency of algal biofilms in nutrient recovery from municipal and agricultural WW was carried out at exemplary places in Mid-Germany. The nutrient recovery of ATS biofilms were quantified by operating four pilot-scale ATS with municipal, pig, cattle, or biogas-effluent WW, for one year. The obtained data were used to evaluate the techno-economic feasibility of algal-based fertilizer production in ATS from WW. The cultivation data were analysed and employed for a technoeconomical evaluation. The results show that macro- and micronutrients were recovered from all WWs in the algal biofilm. Technical data indicate a limited potential of agricultural WWs with high solid or nutrient load. Economic results found ATS biofilm production costs under current settings of 272 to 565 (sic) kg(-1) for the municipal and agricultural WW, respectively. Economic evaluation indicates competitive costs of 2.22 (sic) kg(-1) for fertilizer production in municipal WW at an ATS size of 1760 m(2). SWOT analysis highlight a competitive ATS-based fertilizer with new market opportunities and conceivable solutions to urgent environmental challenges.

With their ability of CO2 fixation using sunlight as an energy source, algae and especially microalgae are moving into the focus for the production of proteins and other valuable compounds. However, the valorization of algal biomass depends on the effective disruption of the recalcitrant microalgal cell wall. Especially cell walls of Chlorella species proved to be very robust. The wall structures that are responsible for this robustness have been studied less so far. Here, we evaluate different common methods to break up the algal cell wall effectively and measure the success by protein and carbohydrate release. Subsequently, we investigate algal cell wall features playing a role in the wall’s recalcitrance towards disruption. Using different mechanical and chemical technologies, alkali catalyzed hydrolysis of the Chlorella vulgaris cells proved to be especially effective in solubilizing up to 56 wt% protein and 14 wt% carbohydrates of the total biomass. The stepwise degradation of C. vulgaris cell walls using a series of chemicals with increasingly strong conditions revealed that each fraction released different ratios of proteins and carbohydrates. A detailed analysis of the monosaccharide composition of the cell wall extracted in each step identified possible factors for the robustness of the cell wall. In particular, the presence of chitin or chitin-like polymers was indicated by glucosamine found in strong alkali extracts. The presence of highly ordered starch or cellulose was indicated by glucose detected in strong acidic extracts. Our results might help to tailor more specific efforts to disrupt Chlorella cell walls and help to valorize microalgae biomass.

This study investigated the anaerobic digestion of an algal–bacterial biofilm grown in artificial wastewater in an Algal Turf Scrubber (ATS). The ATS system was located in a greenhouse (50°54′19ʺN, 6°24′55ʺE, Germany) and was exposed to seasonal conditions during the experiment period. The methane (CH 4 ) potential of untreated algal–bacterial biofilm (UAB) and thermally pretreated biofilm (PAB) using different microbial inocula was determined by anaerobic batch fermentation. Methane productivity of UAB differed significantly between microbial inocula of digested wastepaper, a mixture of manure and maize silage, anaerobic sewage sludge, and percolated green waste. UAB using sewage sludge as inoculum showed the highest methane productivity. The share of methane in biogas was dependent on inoculum. Using PAB, a strong positive impact on methane productivity was identified for the digested wastepaper (116.4%) and a mixture of manure and maize silage (107.4%) inocula. By contrast, the methane yield was significantly reduced for the digested anaerobic sewage sludge (50.6%) and percolated green waste (43.5%) inocula. To further evaluate the potential of algal–bacterial biofilm for biogas production in wastewater treatment and biogas plants in a circular bioeconomy, scale-up calculations were conducted. It was found that a 0.116 km 2 ATS would be required in an average municipal wastewater treatment plant which can be viewed as problematic in terms of space consumption. However, a substantial amount of energy surplus (4.7–12.5 MWh a −1 ) can be gained through the addition of algal–bacterial biomass to the anaerobic digester of a municipal wastewater treatment plant. Wastewater treatment and subsequent energy production through algae show dominancy over conventional technologies. Graphical abstract

Sugarcane bagasse is commonly combusted to generate energy. Unfortunately, recycling strategies rarely consider the resulting ash as a potential fertilizer. To evaluate this recycling strategy for a sustainable circular economy, we characterized bagasse ash as a fertilizer and measured the effects of co-gasification and co-combustion of bagasse with either chicken manure or sewage sludge: on the phosphorus (P) mass fraction, P-extractability, and mineral P phases. Furthermore, we investigated the ashes as fertilizer for soybeans under greenhouse conditions. All methods in combination are reliable indicators helping to assess and predict P availability from ashes to soybeans. The fertilizer efficiency of pure bagasse ash increased with the ash amount supplied to the substrate. Nevertheless, it was not as effective as fertilization with triple-superphosphate and K 2 SO 4 , which we attributed to lower P availability. Co-gasification and co-combustion increased the P mass fraction in all bagasse-based ashes, but its extractability and availability to soybeans increased only when co-processed with chicken manure, because it enabled the formation of readily available Ca-alkali phosphates. Therefore, we recommend co-combusting biomass with alkali-rich residues to increase the availability of P from the ash to plants.

This study investigated and optimized the nutrient remediation efficiency of a simple low-cost algal biofilm reactor, the algal turf scrubber (ATS), for wastewater treatment. Combined effects of three cultivation variables—total inorganic carbon, nitrogen-to-phosphorous (N:P) ratio, and light intensity—were examined. The ATS nutrient removal efficiency and biomass productivity were analyzed considering the response surface methodology (RSM). The maximum removal rates of total P and N were 8.3 and 19.1 mg L −1 d −1 , respectively. As much as 99% of total P and 100% of total N were removed within 7 days. Over the same period, the dissolved oxygen concentration and pH value of the medium increased. The optimal growth conditions for simultaneous maximum P and N removal and biomass productivity were identified. Our RSM-based optimization results provide new insights into the combined effect of nutrient and light availability on the ATS remediation efficiency and biomass productivity.