Organization for Economic Co-Operation and Development (OECD).

Constraints to commercialization of algal fuels.

Spent coffee ground (SCG) contains large amounts of organic compounds (i.e. fatty acids, amino acids, polyphenols, minerals and polysaccharides) that justify its valorization. Earlier innovation explored the extraction of specific components such as oil, flavor, terpenes, and alcohols as value-added products. However, by-products of coffee fruit and bean processing can also be considered as potential functional ingredients for the food industry. There is an urgent need for practical and innovative ideas to use this low cost SCG and exploit its full potential increasing the overall sustainability of the coffee agro-industry.

Spent coffee grounds: A review on current research and future prospects

This article presents a comprehensive review of numerical methods and models for interface resolving simulations of multiphase flows in microfluidics and micro process engineering. The focus of the paper is on continuum methods where it covers the three common approaches in the sharp interface limit, namely the volume-of-fluid method with interface reconstruction, the level set method and the front tracking method, as well as methods with finite interface thickness such as color-function based methods and the phase-field method. Variants of the mesoscopic lattice Boltzmann method for two-fluid flows are also discussed, as well as various hybrid approaches. The mathematical foundation of each method is given and its specific advantages and limitations are highlighted. For continuum methods, the coupling of the interface evolution equation with the single-field Navier–Stokes equations and related issues are discussed. Methods and models for surface tension forces, contact lines, heat and mass transfer and phase change are presented. In the second part of this article applications of the methods in microfluidics and micro process engineering are reviewed, including flow hydrodynamics (separated and segmented flow, bubble and drop formation, breakup and coalescence), heat and mass transfer (with and without chemical reactions), mixing and dispersion, Marangoni flows and surfactants, and boiling.

Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications

Spent coffee grounds (SCG) were extracted with an environmentally friendly procedure and analyzed to evaluate the recovery of relevant natural antioxidants for use as nutritional supplements, foods...

Recovery of natural antioxidants from spent coffee grounds

Oil extracted from spent coffee grounds as a renewable source for fatty acid methyl ester manufacturing

One of the future-generation biofuel options that has recently recieved increased attention is the production of biofuels from microalgae. Besides the use of algae oil for physicochemical biodiesel production, biochemical and thermochemical pathways are possible. Although there is still a need to research algae production systems, downstream processing (e.g., biofuel production) needs to be researched in parallel. As there are several methods to produce biofuel from algae, different possible production processes are reviewed. By investigating the different steps of each of the processes and highlighting the challenges and risks that can occur, it is possible to make a decision regarding which pathway might be feasible for algal resources in the future.

https://www.tandfonline.com/doi/pdf/10.4155/bfs.12.14

Review on possible algal-biofuel production processes

For the disintegration and extraction of microalgae to produce lipids and biofuels, a novel processing technology was investigated. The utilization of a hydrothermal treatment was tested on four different microalgae species (Scenedesmus rubescens, Chlorella vulgaris, Nannochloropsis oculata and Arthorspira platensis (Spirulina)) to determine whether it has an advantage in comparison to other disintegration methods for lipid extraction. It was shown, that hydrothermal treatment is a reasonable opportunity to utilize microalgae without drying and increase the lipid yield of an algae extraction process. For three of the four microalgae species, the extraction yield with a prior hydrothermal treatment elevated the lipid yield up to six times in comparison to direct extraction. Only Scenedesmus rubescens showed a different behaviour. Reason can be found in the different cell wall of the species. The investigation of the differences in cell wall composition of the used species indicate that the existence of algaenan as a cell wall compound plays a major role in stability.

Hydrothermal disintegration and extraction of different microalgae species.

In this paper numerical results on reactive mass transfer from single gas bubbles to a surrounding liquid are presented. The underlying numerical method is based on the solution of the incompressible two-phase Navier-Stokes equations. The Volume-of-Fluid method is applied for the description of the liquidgas interface. Within the numerical approach the concentration of the transfer component is represented by two separate variables, one for each phase. Numerical results are in good agreement with experimental data.

A VOF-based conservative method for the simulation of reactive mass transfer from rising bubbles

In this paper, a Volume-of-Fluid (VOF)-based approach for the Direct Numerical Simulation (DNS) of reactive mass transfer in gas?liquid flows is described. At the interface, local thermodynamic equilibrium is assumed and modelled by Henry's law. First numerical simulation results are presented for non-reactive and reactive mass transfer from rising gas bubbles to a surrounding liquid. For the evaluation of reactive mass transfer simulations with a consecutive, competitive reaction system in the liquid, a local selectivity is employed.

Michael Kröger

Papers

Oil extracted from spent coffee grounds as a renewable source for fatty acid methyl ester manufacturing

Review on possible algal-biofuel production processes

Hydrothermal disintegration and extraction of different microalgae species.

A VOF-based conservative method for the simulation of reactive mass transfer from rising bubbles

VOF-based simulation of reactive mass transfer across deformable interfaces