Techno-Economic Assessment of Biological Biogas Upgrading Based on Danish Biogas Plants

Ex-situ biomethanation for CO2 valorization: State of the art, recent advances, challenges, and future prospective

Ex-situ biomethanation is an emerging technology that facilitates the use of surplus renewable electricity and valorizes carbon dioxide (CO2) for biomethane production by hydrogenotrophic methanogens. This review offers an up-to-date overview of the current state of ex-situ biomethanation and thoroughly analyzes key operational parameters affecting hydrogen (H2) gas-liquid mass transfer and biomethanation performance, along with an in-depth discussion of the technical challenges. To the best of our knowledge, this is the first review article to discuss microbial community structure in liquid and biofilm phases and their responses after exposure to H2 starvation during ex-situ biomethanation. In addition, future research in areas such as reactor configuration and optimization of operational parameters for improving the H2 mass transfer rate, inhibiting opportunistic homoacetogens, integration of membrane technology, and use of conductive packing material is recommended to overcome challenges and improve the efficiency of ex-situ biomethanation. Furthermore, this review presents a techno-economic analysis for the future development and facilitation of industrial implementation. The insights presented in this review will offer useful information to identify state-of-the-art research trends and realize the full potential of this emerging technology for CO2 utilization and biomethane production.

Comprehensive assessment of biorefinery potential for biofuels production from macroalgal biomass: Towards a sustainable circular bioeconomy and greener future

Marine macroalgae have attracted significant interest as a viable resource for biofuel and value-added chemical production due to their abundant availability, low production costs, and high carbohydrate and lipid content. The growing awareness of socio-economic factors worldwide has led to a greater consideration of marine macroalgae as a sustainable source for biofuel production and the generation of valuable products. The integration of biorefinery techniques into biofuel production processes holds immense potential for fostering the development of a circular bioeconomy on a broad scale. Extensive research was focused on the technoeconomic and environmental impact analysis of biofuel production from macroalgal biomass. The integrated biorefinery processes offers valuable pathways for the practical implementation of macroalgae in diverse conversion technologies. These studies provided crucial insights into the large-scale industrial production of biofuels and associated by-products. This review explores the utilization of marine macroalgal biomass for the production of biofuels and biochemicals. It examines the application of assessment tools for evaluating the sustainability of biorefinery processes, including process integration and optimization, life cycle assessment, techno-economic analysis, socio-economic analysis, and multi-criteria decision analysis. The review also discusses the limitations, bottlenecks, challenges, and future perspectives associated with utilizing macroalgal biomass for the production of biofuels and value-added chemicals.

Developing a biogas centralised circular bioeconomy using agricultural residues - Challenges and opportunities

Anaerobic digestion (AD) can be used as a stand-alone process or integrated as part of a larger biorefining process to produce biofuels, biochemicals and fertiliser, and has the potential to play a central role in the emerging circular bioeconomy (CBE). Agricultural residues, such as animal slurry, straw, and grass silage, represent an important resource and have a huge potential to boost biogas and methane yields. Under the CBE concept, there is a need to assess the long-term impact and investigate the potential accumulation of specific unwanted substances. Thus, a comprehensive literature review to summarise the benefits and environmental impacts of using agricultural residues for AD is needed. This review analyses the benefits and potential adverse effects related to developing biogas-centred CBE. The identified potential risks/challenges for developing biogas CBE include GHG emission, nutrient management, pollutants, etc. In general, the environmental risks are highly dependent on the input feedstocks and resulting digestate. Integrated treatment processes should be developed as these could both minimise risks and improve the economic perspective.

Enhancement of Anaerobic Digestion with Nanomaterials: A Mini Review

In recent years, the number of articles reporting the addition of nanomaterials to enhance the process of anaerobic digestion has exponentially increased. The benefits of this addition can be observed from different aspects: an increase in biogas production, enrichment of methane in biogas, elimination of foaming problems, a more stable and robust operation, absence of inhibition problems, etc. In the literature, one of the current focuses of research on this topic is the mechanism responsible for this enhancement. In this sense, several hypotheses have been formulated, with the effect on the redox potential caused by nanoparticles probably being the most accepted, although supplementation with trace materials coming from nanomaterials and the changes in microbial populations have been also highlighted. The types of nanomaterials tested for the improvement of anaerobic digestion is today very diverse, although metallic and, especially, iron-based nanoparticles, are the most frequently used. In this paper, the abovementioned aspects are systematically reviewed. Another challenge that is treated is the lack of works reported in the continuous mode of operation, which hampers the commercial use of nanoparticles in full-scale anaerobic digesters.

Biological Aspects, Advancements and Techno-Economical Evaluation of Biological Methanation for the Recycling and Valorization of CO2

Nowadays, sustainable and renewable energy production is a global priority. Over the past decade, several Power-to-X (PtX) technologies have been proposed to store and convert the surplus of renewable energies into chemical bonds of chemicals produced by different processes. CO2 is a major contributor to climate change, yet it is also an undervalued source of carbon that could be recycled and represents an opportunity to generate renewable energy. In this context, PtX technologies would allow for CO2 valorization into renewable fuels while reducing greenhouse gas (GHG) emissions. With this work we want to provide an up-to-date overview of biomethanation as a PtX technology by considering the biological aspects and the main parameters affecting its application and scalability at an industrial level. Particular attention will be paid to the concept of CO2-streams valorization and to the integration of the process with renewable energies. Aspects related to new promising technologies such as in situ, ex situ, hybrid biomethanation and the concept of underground methanation will be discussed, also in connection with recent application cases. Furthermore, the technical and economic feasibility will be critically analyzed to highlight current options and limitations for implementing a sustainable process.

Energy Use in the EU Livestock Sector: A Review Recommending Energy Efficiency Measures and Renewable Energy Sources Adoption

This study conducts a review bringing together data from a large number of studies investigating energy use in EU livestock systems. Such a study has not been conducted previously, and improvements in our understanding of energy use concentrations in livestock systems will aid in developing interventions to achieve the EU’s 2030 and 2050 sustainability targets. The results from the Life Cycle Assessments included in this review indicate that energy use is concentrated in feed, housing, and manure management. In most systems, animal feed is the dominant energy use category. Regarding specific livestock categories, the studies covered indicate that energy use requirements range from 2.1 to 5.3 MJ/kg per ECM for cow milk, 59.2 MJ/kg for a suckler cow–calf, and 43.73 MJ/kg for a dairy bull, 15.9 MJ/kg to 22.7 MJ/kg for pork production, 9.6 MJ/kg to 19.1 MJ/kg for broiler production, 20.5–23.5 MJ/kg for chicken egg production. Our review indicates dominance of and dependence on fossil fuel and discusses the situation and research around transitioning towards renewable energy sources and improving energy efficiency. Our analysis indicates that existing energy use data in livestock systems are fragmented and characterized by multiple methodologies and considerable data gaps. In our view, there is a need for the development of a standardized methodology for measuring energy use in livestock systems, which we consider a necessary step to develop interventions that reduce fossil energy use in livestock systems and its contribution to climatic change.