Search

Hydrogen can be produced from several feedstocks and technologies, making it an important partner in the energy transition to neutral carbon societies. Hydrogen production can be based on renewable feedstocks, such as agricultural residues, which are highly available and economical. However, a comprehensive analysis of all available hydrogen production technologies must be done. Therefore, this work focused on developing a comparative analysis of the sustainability of the main hydrogen production technologies. Technologies with the greatest opportunity for development were simulated and evaluated from a sustainability perspective. Techno-energetic, economic, environmental, and social indicators were used to calculate a comprehensive sustainability index (S Id). Steam biomethane reforming (SBMR) and electrolysis (EL) were the schemes with the highest S Id based on the techno-energetic and environmental dimensions. However, the S Id decreased substantially when the economic dimension was considered because SBMR presented high capital and operating costs, and EL had low technical performance. On the other hand, thermochemical and biological technologies require further research to decrease the environmental burden and improve the mass yield of the process. Therefore, each production scheme involves different disadvantages that must be resolved to increase the opportunities for hydrogen development. [Display omitted] • The sustainability index made it possible to establish the development opportunity presented by each technology considering different dimensions of analysis. • Steam biomethane reforming and gasification processes are more efficient and economically viable than electrolytic and biological technologies. • The cost of hydrogen production in electrolytic processes is highly dependent on the primary source of electricity. • Hydrogen production by biological processes requires more research on improving yields and production costs. • The scheme with the highest sustainability indexes was the steam biomethane reforming scheme. [ABSTRACT FROM AUTHOR]

This work evaluates the sustainability of small-scale biorefineries as a potential enterprise alternative to be introduced in rural areas based on experimental and simulation data. Four scenarios were evaluated: the first scenario involves the production of guacamole, the second involves the production of animal feed, and the third and fourth scenarios involve the extraction of bioactive compounds and the production of avocado oil or animal feed, respectively. In addition, all scenarios produce biogas and fertilizer. Each of the scenarios were evaluated considering the technical, economic, environmental, and social aspects. As a main result, the first scenario showed the lowest operating and investment costs, as well as the lowest economic profitability (profit margin 35%). On the other hand, the third and fourth scenarios present the highest investment and operating expenses (OpEx USD 6.2 million per year and CapEx USD 1.0 million), but their profit margins are in the 60–70% range. Furthermore, a life-cycle assessment (LCA) was carried out and allows inferring that the transformer link presents the highest environmental impact of the entire value chain and that the carbon footprint for all scenarios ranges between 1.01–2.41 kg C O 2 eq per kg avocado. Similarly, the social impact methodology shows that the proposed scenarios do not present any social risk. Thus, the biorefinery for animal feed, bioactive compounds, biogas, and fertilizer was selected as the best option to be implemented in Caldas. [ABSTRACT FROM AUTHOR]

Biorefinery feasibility is highly influenced by the early design of the best feedstock transformation pathway to obtain value-added products. Pretreatment has been identified as the critical stage in biorefinery design since proper pretreatment influences subsequent reaction, separation, and purification processes. However, many pretreatment analyses have focused on preserving and valorizing six-carbon sugars for future use in bioconversion processes, leaving aside fractions such as hemicellulose and lignin. To date, there has been no pretreatment systematization for the removal of lignocellulosic fractions. This work defines pretreatment efficacy through operational, economic, environmental, and social indicators. Thus, using the data reported in the literature, as well as the results of the simulation schemes, a multi-criteria weighting of the best-performing schemes for the isolation or removal of cellulose, hemicellulose, and lignin was carried out. As a main result, it was concluded that dilute acid is the most effective for cellulose isolation and hemicellulose removal for producing platform products based on six- and five-carbon sugars, respectively. Additionally, the kraft process is the best methodology for lignin removal and its future use in biorefineries. The results of this work help to elucidate a methodological systematization of the pretreatment efficacy in the design of biorefineries as an early feasibility stage considering sustainability aspects. [ABSTRACT FROM AUTHOR]

Hydrogen is a key energy vector to accomplishing energy transition and decarbonization goals proposed in the transport and industrial sectors worldwide. In recent years, research has focused on analyzing, designing, and optimizing hydrogen production, searching to improve economic prefeasibility with minimal emissions of polluting gases. Therefore, the techno-economic analysis of hydrogen production by electrolytic and gasification processes becomes relevant since these processes could compete commercially with industrial technologies such as SMR - Steam methane reforming. This work aims to analyze hydrogen production in stand-alone processes and energy-driven biorefineries. The gasification and electrolysis technologies were evaluated experimentally, and the yields obtained were input data for scaling up the processes through simulation tools. Biomass gasification is more cost-effective than electrolytic schemes since the hydrogen production costs were 4.57 USD/kg and 8.30 USD/kg at an annual production rate of 491.6 tons and 38.96 tons, respectively. Instead, the electrolysis process feasibility is strongly influenced by the recycled water rate and the electricity cost. A sensitivity analysis was performed to evaluate the temperature, pressure, and current density variability on the hydrogen production rate. The increase in pressure and current density induces parasitic currents while the temperature increases hydrogen production. Although higher hydrogen production rates from gasification, the syngas composition decreases the possibility of being implemented in applications where purity is critical. [Display omitted] • The costs associated with raw materials and utilities have the greatest impact on the hydrogen product cost. • The prefeasibility of the electrolytic processes depends strongly on the recirculated water and electricity cost. • The thermochemical processes present higher economic profitability than the electrolytic processes. [ABSTRACT FROM AUTHOR]

The depletion of energy resources worldwide shows the need to develop new energy carriers while reducing the environmental impact of energy generation. Cassava is a highly distributed crop in Colombia, and Sucre is a region that contributes more than 40% of national production through an established value chain. Like other crops, cassava generates different usable residues, such as the cassava stalk, which can be valorized by producing energy carriers that meet the needs of the process. Therefore, this work aimed to evaluate the environmental impact of the cassava value chain (VC) for the Sucre region and to analyze the possibility of including residues processing stages to produce low (biomethane) and high complexity (hydrogen) energy carriers. The life cycle assessment (LCA) considered the agronomic stage, including some links of the value chain (suppliers, producers, transformers, and market) and the production schemes of energy carriers, generating biomethane through anaerobic digestion and hydrogen through steam biomethane reforming. The inventory was developed considering reports from the National Cassava Federation (COLFEYUCA) for the Sucre region, and the mass and energy balances in the simulation schemes were obtained from the Aspen Plus v9.0 software. As the main results, the influence of the transformer stage in the value chain can be highlighted, contributing more than 90% of the impact due to energy demands and waste generated. Additionally, when energy carriers was included, biomethane and hydrogen can supply the total energy needs of the biorefinery and between 72% and 58% of the energy demand of the transformation stage, respectively. In addition, it was established that the value chain without the valorization of the cassava residues produced 1.22 kg CO 2 eq/kg of cassava. In comparison, when including the valorization stages, the value chain generated 1.20 kg CO 2 /kg of cassava, where the raw materials, especially the sludge for anaerobic digestion, presented the greatest contribution to the environmental impact in the biorefineries. Thus, it can be concluded that cassava crop residues and biomethane production are established as a processing alternative for generating usable energy within the links of the production chain, mitigating, in turn, the overall impact of the value chain. • The life cycle assessment concluded that the link with the greatest environmental impact in the value chain was the transformers. • The predominant emissions were emissions to air and water, led by nitrogen compounds. • The inclusion of valorization schemes for the generation of usable energy carriers mitigates the environmental impact. • The environmental impact of valorization schemes was associated with the input of high impact streams such as sludge for anaerobic digestion. • Hydrogen is a complex energy carrier to install in rural areas, therefore biomethane presents greater development opportunities. [ABSTRACT FROM AUTHOR]