Prospecting for underground natural hydrogen - new energy for the future

Hydrogen, accounting for 75% of ordinary matter by mass and over 90% by atomic number, is the third most abundant element on the Earth's surface, mainly in the form of chemical compounds such as water and hydrocarbons. When burned, hydrogen gas (H2) produces heat and water without causing environmental pollution, thus it is expected to be one of the clean energy sources for the future. Industrial hydrogen has so far been mainly produced by thermochemical processes of fossil fuels such as coal and natural gas, and insignificantly by electrolysis of water. Recent natural hydrogen discoveries recorded in the world, especially the exploration and discovery of relatively pure underground hydrogen which was extracted and used as fuel for a local power generator in Bourakebougou (Mali), show the possibility of prospecting for underground natural hydrogen. The article provides an overview of natural hydrogen discoveries over the world and gives recommendations on the prospecting for underground natural hydrogen in Vietnam.

Hydrogen as a Clean and Sustainable Energy Vector for Global Transition from Fossil-Based to Zero-Carbon

Hydrogen is recognized as a promising and attractive energy carrier to decarbonize the sectors responsible for global warming, such as electricity production, industry, and transportation. However, although hydrogen releases only water as a result of its reaction with oxygen through a fuel cell, the hydrogen production pathway is currently a challenging issue since hydrogen is produced mainly from thermochemical processes (natural gas reforming, coal gasification). On the other hand, hydrogen production through water electrolysis has attracted a lot of attention as a means to reduce greenhouse gas emissions by using low-carbon sources such as renewable energy (solar, wind, hydro) and nuclear energy. In this context, by providing an environmentally-friendly fuel instead of the currently-used fuels (unleaded petrol, gasoline, kerosene), hydrogen can be used in various applications such as transportation (aircraft, boat, vehicle, and train), energy storage, industry, medicine, and power-to-gas. This article aims to provide an overview of the main hydrogen applications (including present and future) while examining funding and barriers to building a prosperous future for the nation by addressing all the critical challenges met in all energy sectors.

Scientometric Overview of Coffee By-Products and Their Applications

As coffee consumption is on the rise, and the global coffee production creates an excess of 23 million tons of waste per year, a revolutionary transition towards a circular economy via the transformation and valorization of the main by-products from its cultivation and preparation (Coffee Husk (CH), Coffee Pulp (CP), Coffee Silverskin (CS), and Spent Coffee Grounds (SCG)) is inspiring researchers around the world. The recent growth of scholarly publications in the field and the emerging applications of coffee by-products published in these scientific papers encourages a systematic review to identify the knowledge structure, research hotspots, and to discuss the challenges and future directions. This paper displays a comprehensive scientometric analysis based on 108 articles with a high level of influence in the field of coffee by-products and their applications. According to our analysis, the research in this field shows an explosive growth since 2017, clustered in five core applications: bioactive compounds, microbial transformation, environmental applications, biofuels from thermochemical processes, and construction materials.

Modeling of thermochemical conversion of waste biomass – a comprehensive review

Thermochemical processes, which include pyrolysis, torrefaction, gasification, combustion, and hydrothermal conversions, are perceived to be more efficient in converting waste biomass to energy and value-added products than biochemical processes. From the chemical point of view, thermochemical processes are highly complex and sensitive to numerous physicochemical properties, thus making reactor and process modeling more challenging. Nevertheless, the successful commercialization of these processes is contingent upon optimized reactor and process designs, which can be effectively achieved via modeling and simulation. Models of various scales with numerous simplifying assumptions have been developed for specific applications of thermochemical conversion of waste biomass. However, there is a research gap that needs to be explored to elaborate the scale of applicability, limitations, accuracy, validity, and special features of each model. This review study investigates all above mentioned important aspects and features of the existing models for all established industrial thermochemical conversion processes with emphasis on waste biomass, thus addressing the research gap mentioned above and presenting commercial-scale applicability in terms of reactor designing, process control and optimization, and potential ways to upgrade existing models for higher accuracy.

Conceptual Process Design, Energy and Economic Analysis of Solid Waste to Hydrocarbon Fuels via Thermochemical Processes

Thermochemical processes use heat and series of endothermic chemical reactions that achieve thermal cracking and convert a wide range of solid waste deposits via four thermochemical processes to hydrocarbon gaseous and liquid products such as syngas, gasoline, and diesel. The four thermochemical reactions investigated in this research article are: incineration, pyrolysis, gasification, and integrated gasification combined cycle (IGCC). The mentioned thermochemical processes are evaluated for energy recovery pathways and environmental footprint based on conceptual design and Aspen HYSYS energy simulation. This paper also provides conceptual process design for four thermochemical processes as well as process evaluation and techno-economic analysis (TEA) including energy consumption, process optimization, product yield calculations, electricity generation and expected net revenue per tonne of feedstock. The techno-economic analysis provides results for large scale thermochemical process technologies at an industrial level and key performance indicators (KPIs) including greenhouse gaseous emissions, capital and operational costs per tonne, electrical generation per tonne for the four mentioned thermochemical processes.

Waste-to-Energy: An Opportunity to Increase Renewable Energy Share and Reduce Ecological Footprint in Small Island Developing States (SIDS)

Small Island Developing States (SIDSs) are faced with challenges such as reducing the share of fossil energy and waste landfilling. This work summarizes the main aspects of 53 SIDSs that constrain economic development, energy sources, and waste management strategies. An integrative bibliographical review is conducted to synthesize the state-of-the-art of waste-to-energy (WtE) strategies and compare the technologies in light of their suitability to SIDS. The findings show that considering the large amount of waste produced annually, WtE technologies are of the utmost importance to reduce ecological footprints (EFs) and greenhouse gas (GHG) emissions, and to increase the share of renewable energy with the installation of incineration plants with energy recovery to replace fossil fuel power plants. Although WtE is recommended for all SIDSs, the Atlantic, Indian Ocean, Mediterranean, and South China Sea (AIMS) countries exhibit higher population density (1509 inhab/km2) and a high share of fossil fuel in their electricity mix, so that there is greater urgency to replace landfilling practices with WtE. The estimation of potential power generation capacity (MWh) from annual municipal solid waste (MSW) in each SIDS as well as the reduced land area required demonstrate the feasibility of WtE technologies. Only 3% of the landfill area is necessary for buildings and landscaping associated with a WtE plant able to treat 1 million tons of MSW, considering a 30 year lifespan. Furthermore, incineration with energy recovery benefits from high penetration worldwide and affordable cost among thermochemical processes.