The hydrogen gas bio-based economy and the production of renewable building block chemicals, food and energy

Seasonal characteristics of particle size distribution of organic markers in atmospheric particulate matters in Beijing

Beijing is a metropolis that is quickly growing, which has significant and unusual air pollution issues. In Beijing, organic matter makes up about 40%-60% of the total mass of fine particles, making it the most prevalent portion and highlighting its crucial role in reducing air pollution. However, a thorough chemical analysis of particulate organic matter has never been reported in Beijing. In this work, the organic components of fine particles in Beijing's urban environment were examined by the Gas Chromatography and Mass Spectrometry (GC/MS) method. In 30 p.m. (Particulate matter) 2.5, more than 101 unique chemical compounds were identified and measured. Seven samples from the 2015-2016 summer, including harvest, cold, Aromatic hydrocarbons, unsaturated fats, ferulic acid, polyaromatic, and some tracer substances (hopanes, present in environmental samples, and corticosteroids) were the main ingredients, with their total concentrations being 489, 1369, and 1366 ng*m-3 in the summer, respectively. Due to their various primary pollution sources, such as combustion processes, fuel combustion, and culinary emissions, various organic compounds displayed ostensibly varied seasonal tendencies. Discussion of these organic chemicals' prevalence and a source reveals Beijing's seasonal air pollution patterns.

Nutrient recovery and pollutant removal during renewable fuel production: opportunities and challenges

Stimulated by the desire to achieve a Net Zero energy economy, the demand for renewable fuels is growing rapidly. The production of toxic waste streams that accompanies the transition from fossil fuels to renewable fuels is often overlooked. These waste streams include, among others, thiols and ammonia, and benzene, toluene, and xylene (BTX). When suitable treatment technologies are available, these compounds can be converted to valuable nutrients. In this opinion article, we provide an overview of expected waste streams and their characteristics. We indicate future challenges for associated waste streams, such as the lag in developing resource recovery technologies. Furthermore, we discuss unexploited opportunities to recover valuable nutrients from these waste streams.

Dehazing redox homeostasis to foster purple bacteria biotechnology

Purple non-sulfur bacteria (PNSB) show great potential for environmental and industrial biotechnology, producing microbial protein, biohydrogen, polyhydroxyalkanoates (PHAs), pigments, etc. When grown photoheterotrophically, the carbon source is typically more reduced than the PNSB biomass, which leads to a redox imbalance. To mitigate the excess of electrons, PNSB can exhibit several 'electron sinking' strategies, such as CO₂ fixation, N₂ fixation, and H₂ and PHA production. The lack of a comprehensive (over)view of these redox strategies is hindering the implementation of PNSB for biotechnology applications. This review aims to present the state of the art of redox homeostasis in phototrophically grown PNSB, presenting known and theoretically expected strategies, and discussing them from stoichiometric, thermodynamic, metabolic, and economic points of view.

Hydrogen Oxidizing Bacteria as Novel Protein Source for Human Consumption: An Overview

The increasing threat of climate change combined with the prospected growth in the world population puts an enormous pressure on the future demand for sustainable protein sources for human consumption. In this review, hydrogen oxidizing bacteria (HOB) are presented as a novel protein source that could play a role in fulfilling this future demand. HOB are species of bacteria that merely require an inflow of the gasses hydrogen, oxygen, carbon dioxide, and a nitrogen source to grow in a conventional bioreactor. Cupriavidus necator is proposed as HOB for industrial cultivation due to its remarkably high protein content (up to 70% of mass), suitability for cultivation in a bioreactor, and the vast amount of available background information. A broad overview of the unique aspects of the bacteria will be provided, from the production process, amino acid composition, and source of the required gasses to the future acceptance of HOB into the market.

Hydrogen-oxidizing bacteria and their applications in resource recovery and pollutant removal

Hydrogen oxidizing bacteria (HOB), a type of chemoautotroph, are a group of bacteria from different genera that share the ability to oxidize H₂ and fix CO₂ to provide energy and synthesize cellular material. Recently, HOB have received growing attention due to their potential for CO₂ capture and waste recovery. This review provides a comprehensive overview of the biological characteristics of HOB and their application in resource recovery and pollutant removal. Firstly, the enzymes, genes and corresponding regulation systems responsible for the key metabolic processes of HOB are discussed in detail. Then, the enrichment and cultivation methods including the coupled water splitting-biosynthetic system cultivation, mixed cultivation and two-stage cultivation strategies for HOB are summarized, which is the critical prerequisite for their application. On the basis, recent advances of HOB application in the recovery of high-value products and the removal of pollutants are presented. Finally, the key points for future investigation are proposed that more attention should be paid to the main limitations in the large-scale industrial application of HOB, including the mass transfer rate of the gases, the safety of the production processes and products, and the commercial value of the products.

Advanced polymeric/inorganic nanohybrids: An integrated platform for gas sensing applications

Rapid industrial development, vehicles, domestic activities and mishandling of garbage are the main sources of pollutants, which are destroying the atmosphere. There is a need to continuously monitor these pollutants for the safety of the environment and human beings. Conventional instruments for monitoring of toxic gases are expensive, bigger in size and time-consuming. Hybrid materials containing organic and inorganic components are considered potential candidates for diverse applications, including gas sensing. Gas sensors convert the information regarding the analyte into signals. Various polymeric/inorganic nanohybrids have been used for the sensing of toxic gases. Composites of different polymeric materials like polyaniline (PANI), poly (4-styrene sulfonate) (PSS), poly (3,4-ethylene dioxythiophene) (PEDOT), etc. with various metal/metal oxide nanoparticles have been reported as sensing materials for gas sensors because of their unique redox features, conductivity and facile operation at room temperature. Polymeric nanohybrids showed better performance because of the larger surface area of nanohybrids and the synergistic effect between polymeric and inorganic materials. This review article focuses on the recent developments of emerging polymeric/inorganic nanohybrids for sensing various toxic gases including ammonia, hydrogen, nitrogen dioxide, carbon oxides and liquefied petroleum gas. Advantages, disadvantages, operating conditions and prospects of hybrid composites have also been discussed.

Waste-to-nutrition: a review of current and emerging conversion pathways

Residual biomass is acknowledged as a key sustainable feedstock for the transition towards circular and low fossil carbon economies to supply whether energy, chemical, material and food products or services. The latter is receiving increasing attention, in particular in the perspective of decoupling nutrition from arable land demand. In order to provide a comprehensive overview of the technical possibilities to convert residual biomasses into edible ingredients, we reviewed over 950 scientific and industrial records documenting existing and emerging waste-to-nutrition pathways, involving over 150 different feedstocks here grouped under 10 umbrella categories: (i) wood-related residual biomass, (ii) primary crop residues, (iii) manure, (iv) food waste, (v) sludge and wastewater, (vi) green residual biomass, (vii) slaughterhouse by-products, (viii) agrifood co-products, (ix) C₁ gases and (x) others. The review includes a detailed description of these pathways, as well as the processes they involve. As a result, we proposed four generic building blocks to systematize waste-to-nutrition conversion sequence patterns, namely enhancement, cracking, extraction and bioconversion. We further introduce a multidimensional representation of the biomasses suitability as potential as nutritional sources according to (i) their content in anti-nutritional compounds, (ii) their degree of structural complexity and (iii) their concentration of macro- and micronutrients. Finally, we suggest that the different pathways can be grouped into eight large families of approaches: (i) insect biorefinery, (ii) green biorefinery, (iii) lignocellulosic biorefinery, (iv) non-soluble protein recovery, (v) gas-intermediate biorefinery, (vi) liquid substrate alternative, (vii) solid-substrate fermentation and (viii) more-out-of-slaughterhouse by-products. The proposed framework aims to support future research in waste recovery and valorization within food systems, along with stimulating reflections on the improvement of resources' cascading use.

Highly Permeable Fluorinated Polymer Nanocomposites for Plasmonic Hydrogen Sensing

Hydrogen (H₂) sensors that can be produced en masse with cost-effective manufacturing tools are critical for enabling safety in the emerging hydrogen economy. The use of melt-processed nanocomposites in this context would allow the combination of the advantages of plasmonic hydrogen detection with polymer technology; an approach which is held back by the slow diffusion of H₂ through the polymer matrix. Here, we show that the use of an amorphous fluorinated polymer, compounded with colloidal Pd nanoparticles prepared by highly scalable continuous flow synthesis, results in nanocomposites that display a high H₂ diffusion coefficient in the order of 10^-5 cm² s^-1. As a result, plasmonic optical hydrogen detection with melt-pressed fluorinated polymer nanocomposites is no longer limited by the diffusion of the H₂ analyte to the Pd nanoparticle transducer elements, despite a thickness of up to 100 μm, thereby enabling response times as short as 2.5 s at 100 mbar (≡10 vol. %) H₂. Evidently, plasmonic sensors with a fast response time can be fabricated with thick, melt-processed nanocomposites, which paves the way for a new generation of robust H₂ sensors.

Potential of microbial protein from hydrogen for preventing mass starvation in catastrophic scenarios

Human civilization's food production system is currently unprepared for catastrophes that would reduce global food production by 10% or more, such as nuclear winter, supervolcanic eruptions or asteroid impacts. Alternative foods that do not require much or any sunlight have been proposed as a more cost-effective solution than increasing food stockpiles, given the long duration of many global catastrophic risks (GCRs) that could hamper conventional agriculture for 5 to 10 years. Microbial food from single cell protein (SCP) produced via hydrogen from both gasification and electrolysis is analyzed in this study as alternative food for the most severe food shock scenario: a sun-blocking catastrophe. Capital costs, resource requirements and ramp up rates are quantified to determine its viability. Potential bottlenecks to fast deployment of the technology are reviewed. The ramp up speed of food production for 24/7 construction of the facilities over 6 years is estimated to be lower than other alternatives (3-10% of the global protein requirements could be fulfilled at end of first year), but the nutritional quality of the microbial protein is higher than for most other alternative foods for catastrophes. Results suggest that investment in SCP ramp up should be limited to the production capacity that is needed to fulfill only the minimum recommended protein requirements of humanity during the catastrophe. Further research is needed into more uncertain concerns such as transferability of labor and equipment production. This could help reduce the negative impact of potential food-related GCRs.

Enhanced Phototrophic Biomass Productivity through Supply of Hydrogen Gas

Industrial production of phototrophic microorganisms is often hindered by low productivity due to limited light availability and therefore requires large land areas. This letter demonstrates that supply of hydrogen gas (H₂) increases in phototrophic biomass productivity compared to a culture growing on light only. Experiments were performed growing Synechocystis sp. in batch bottles, with and without H₂ in the headspace, which were exposed to light intensities of 70 and 100 μmol/m²/s. At 70 μmol/m²/s with H₂, the average increase in biomass was 96 mg DW/L/d, whereas at 100 μmol/m²/s without H₂, the average increase in biomass was 27 mg DW/L/d. Even at lower light intensity, the addition of H₂ tripled the biomass yield compared to growth under light only. Photoreduction and photosynthesis occurred simultaneously, as both H₂ consumption and O₂ production were measured during biomass growth. Photoreduction used 1.85 mmol of H₂ to produce 1.0 mmol of biomass, while photosynthesis produced 1.95 mmol of biomass. After transferring the culture to the dark, growth ceased, also in the presence of H₂, showing that both light and H₂ were needed for growth. A renewable H₂ supply for higher biomass productivity is attractive since the combined efficiency of photovoltaics and electrolysis exceeds the photosynthetic efficiency.

Proteinaceous methanotrophs for feed additive using biowaste as carbon and nutrients source

To achieve a sustainable production of food and feed production, inexpensive carbon and nutrient sources are needed. In the present study, biologically upgraded biogas is coupled with electrochemically extracted nitrogen from digested biowaste to cultivate mixed methanotrophs as protein source. Results showed that an increase from less than 5 μgCu²⁺/L to 100 μgCu²⁺/L increased the biomass production by 41%. Microbial analysis revealed that the dominated Methylomonas spp. followed by Methylophilus spp. created a specialized community for high CH₄ assimilation. Moreover, duplicate semi-continuous fermenters run for 120 days validating the efficiency of alternative carbon and nitrogen feedstocks at long-term operation. As for dry cell weight (DCW) production, more than 2.5 g-DCW/L were produced using biologically upgraded biogas and electrochemically extracted nitrogen. Furthermore, the protein content and amino acid profile (>50% of DCW) demonstrated that the microbial biomass pose the characteristics to be used as animal feed additive.

Supportiveness of Low-Carbon Energy Technology Policy Using Fuzzy Multicriteria Decision-Making Methodologies

The deployment of low-carbon energy (LCE) technologies and management of installations represents an imperative to face climate change. LCE planning is an interminable process affected by a multitude of social, economic, environmental, and health factors. A major challenge for policy makers is to select a future clean energy strategy that maximizes sustainability. Thus, policy formulation and evaluation need to be addressed in an analytical manner including multidisciplinary knowledge emanating from diverse social stakeholders. In the current work, a comparative analysis of LCE planning is provided, evaluating different multicriteria decision-making (MCDM) methodologies. Initially, by applying strengths, weaknesses, opportunities, and threats (SWOT) analysis, the available energy alternative technologies are prioritized. A variety of stakeholders is surveyed for that reason. To deal with the ambiguity that occurred in their judgements, fuzzy goal programming (FGP) is used for the translation into fuzzy numbers. Then, the stochastic fuzzy analytic hierarchical process (SF-AHP) and fuzzy technique for order performance by similarity to ideal solution (F-TOPSIS) are applied to evaluate a repertoire of energy alternative forms including biofuel, solar, hydro, and wind power. The methodologies are estimated based on the same set of tangible and intangible criteria for the case study of Thessaly Region, Greece. The application of FGP ranked the four energy types in terms of feasibility and positioned solar-generated energy as first, with a membership function of 0.99. Among the criteria repertoire used by the stakeholders, the SF-AHP evaluated all the criteria categories separately and selected the most significant category representative. Finally, F-TOPSIS assessed these criteria ordering the energy forms, in terms of descending order of ideal solution, as follows: solar, biofuel, hydro, and wind.

Wastewater treatment in 2050: Challenges ahead and future vision in a European context

•Wastewater treatment plants are slowly evolving.•In the next decade, successful implementation of technologies is focused intensification.•New technologies will be focused on gases and bio-based materials.•Academics need more freedom to develop novel concepts.•Collaborative platforms that enable demonstration of high-risk technologies is key.