Multi-criteria decision analysis of wood waste ash and glass foam: toward sustainable material selection for biomethanation

Z. Kusnere*, D. Lauka and K. Spalvins

Riga Technical University, Institute of Energy Systems and Environment,
Azenes iela 12/1, LV 1048 Riga, Latvia
*Correspondence: zane.kusnere@rtu.lv

Abstract:

The study examines the potential applications of wood waste ash and waste glass, by-products of various industrial processes, which have conventional applications such as composting and soil improvement. A new development, vulcanised wood ash material, is studied analysed, drawing parallels between its industrial production process and that of clay pellets. Vulcanised wood ash material and glass foam, which are characterised by advantageous chemical and physical properties, are proving to be versatile resources for various technical applications. Employing a systematic decision-making approach, the study utilises multi-criteria decision analysis and the Technique for Order of Preference by Similarity to Ideal Solution method to evaluate materials for biotrickling filter reactors in ex-situ biomethanation. The comparative analysis includes ash filter material, glass foam, and other industry alternatives, emphasising environmental impacts. The findings reveal expanded clay pellets as the most suitable carrier material, closely followed by polyurethane foam, while glass foam demonstrates remarkable performance despite ranking third. The innovative qualities of glass foam, such as high porosity and thermal insulation, position it as a viable option for biotrickling filter reactors, promoting sustainable practices and circular economy principles. However, further development is required to optimise vulcanised wood ash for biomethanation, potentially enhancing its efficiency through pH adjustment and porosity optimisation.

Key words:

In search of the best technological solutions for creating edible protein-rich mutants: a multi-criteria analysis approach

I. Berzina*, S. Raita, M. Kalnins, K. Spalvins and I. Kuzmika

Riga Technical University, Institute of Energy Systems and Environment, Azenes street 12/1, LV 1048, Riga, Latvia
*Correspondence: Indra.Berzina@rtu.lv

Abstract:

Single-cell protein (SCP) is a promising alternative for replacing plant and animal-derived dietary proteins. SCP contains essential nutrients and high levels of essential amino acids (AA). Given the versatility of microbial strains and waste substrates that can be used as feedstocks, many variations of production processes can be explored. Improving these microorganism strains by enhancing their properties and productivity is vital to increasing SCP competitiveness. One of the options to enhance microorganism strains would be by creating mutants with better AA profiles. By using mutagenesis and AA inhibitors it should be possible the create novel strains with improved AA-producing properties. The use of AA inhibitors to promote selective pressure on SCP-producing strains is a novel concept and is not a widely explored approach, therefore, the further development of this method should be explored. This paper used a multi-criteria decision analysis method to evaluate different technological factors vital for creating protein-rich mutants. These factors are microorganism strains, agro-industrial waste substrates used as process feedstocks, AA inhibitors, and mutagenesis methods. Microorganisms Candida utilis and Bacillus subtilis showed the highest potential for being used. Molasses was the ‘closest to the ideal’ substrate to be used as feedstock for SCP production. As the most promising mutagenesis method ethyl methane sulphonate was selected. Glufosinate ammonium and methionine sulfoximine for both bacteria and fungi were identified as the best inhibitors for SCP-rich mutant selection. Identified combinations of optimal solutions for microorganisms, substrates, inhibitors, and mutagenesis techniques should be further investigated and evaluated in laboratory settings. This could help to increase SCP’s competitiveness as a sustainable protein source.

Key words:

agro-industrial waste, amino acid inhibitors, amino acids, biomass, herbicides, low-cost substrate, MCDA, microbial protein, microorganisms, multi-criteria analysis, mutagenesis, proteins, residues, SCP, single-cell proteins, TOPSIS, waste biomass