Muhammad Tahir Ashraf

• Doctor of Philosophy
• Assistant Professor at University of Southern Denmark

Trace metals are indispensable for the metalloenzymes involved for efficient H2/CO2 biomethanation. In-depth understanding of trace metals requirements of methanogens cannot only lead to robust and stable operation, but also can enhance CH4 productivity. In this study, the effect of trace metals on the biomethanation process was examined. Trace met...

Research within biological methanation has been a great development using biotrickling filters (BTF), as a power-to-x solution, but research within up scaling is missing. This study investigates the commercial potential of biomethanation in BTF by operating two 1 m³ reactors which was implemented into a full-scale biogas plant. Several areas were i...

Ex-situ biomethanation in a biotrickling filter is being developed as a robust technology for the conversion of CO2 to CH4 using H2 generated from renewable power. The technology uses hydrogenotrophic methanogens in a biofilm as the catalyst and the optimum supply of nutrients in the biofilm is imperative for stable and long-term operation. In this...

Ex-situ biomethanation in a biotrickling filter is being developed as a robust technology for the conversion of CO2 to CH4 using H2 generated from renewable power. The technology uses hydrogenotrophic methanogens in a biofilm as the catalyst and the optimum supply of nutrients in the biofilm is imperative for stable and long-term operation. In this...

Ex-situ biomethanation in a biotrickling filter is being developed as a robust technology for the conversion of CO 2 to CH 4 using H 2 generated from renewable power. The technology uses hydrogenotrophic methanogens in a biofilm as the catalyst and the optimum supply of nutrients in the biofilm is imperative for stable and long-term operation. In t...

Disposal of carbon-rich wastes, such as food waste, is one of the several environmental concerns raised nowadays. Conversion of organic residues by dark fermentation produces short-chain (C1–C6) carboxylic acids, which are valuable chemical building blocks. The objective of this study was to optimize the operational parameters and perform comparati...

Hydrogenotrophic biomethanation in a biotrickling filter has been reported to be a proven technology for biological biogas upgrading in recent studies. However, the preparation of enriched hydrogenotrophic methanogens in a separate reactor prior to biomethanation in a trickled bed is a lengthy procedure and therefore hard to apply on an industrial...

Optimum pH for methanogenesis in an anaerobic digester is well known, however, the effect of pH and its control strategy for the ex-situ biomethanation is understudied. In this study, two pH control strategies, namely the addition of buffer media and the control of CO2/H2 feed ratio, were investigated using a thermophilic biotrickling filter. Among...

Bio-based plastics, produced from natural and renewable sources, have been found to be good replacers to petroleum-based plastics. However, economic analyses have not been carried out for most of them, specifically those from whey. In this study, a techno-economic assessment of the industrial-scale production of plastics from whey protein is carrie...

The prevailing trends in global energy consumption and the rapid depletion of fossil fuel present an urgent need for alternative fuels, particularly from renewable sources of biomass. In this study, date palm tree mixture wastes (DTM) and date seed (DS) biomass were used as starting materials in the production of bio-oil by pyrolysis. The yields of...

Hydrogenotrophic methanogenesis is a power-to-gas method, biologically converting CO2 to CH4 using H2 generated from electrical power. However, the low rate of gas-liquid mass transfer of H2 limits the hydrogenotrophic methanogens biocatalyst. We explored hydrogenotrophic methanogenesis using cattle manure as trickling solution by employing a therm...

Designing a biorefinery involves the selection of the set of products and the technologies that will be used for processing a given set of biomass feedstocks. Biorefinery design methodologies have relied either in conventional conceptual process design, where the set of products and technologies under consideration is fixed, or on the optimization...

Biorefinery based on multi-feedstock lignocellulose can be viable where a sustainable supply of a single substrate is limited, for example in arid regions. Processing of mixed feedstocks has been studied in lab scale, however, its economics are less studied. In this study, an economic comparison was made between separate and combined (mixed) proces...

Techno-economic evaluation of processes based on hydrothermal pretreatment is needed to set the current status and to identify processing bottlenecks that need to be addressed to make these processes viable. Having suitable models to carry simulations is a prerequisite for conducting such evaluations. The goal of this chapter is to discuss differen...

Utilization of multi-specie feedstocks is imperative for application of lignocellulosic biorefineries in arid regions. Different lignocellulosic residues vary in composition and anatomical features. Pretreatment and enzymatic hydrolysis are two processes at the front end of any lignocellulosics biorefinery applying biochemical pathway, and have to...

Sizing of large scale pervaporation units from experimental data requires mathematical models which can predict the pervaporation process performance adequately. In this work, a modeling approach is reported with a semi-empirical flux model regressed over experimental flux data measured at lab scale. The regression approach generates a temperature...

Lignocellulosic biorefineries consist of multiple processing steps that can be carried out by a single or by different actors. In the latter case, biorefineries can be decomposed into suppliers of intermediates and consumers of them. Following this decomposition, a multi-actor multi-objective optimization problem can be formulated and a two-level L...

Microalgae is a promising feedstock for the production of liquid fuels to be used as replacements of oil-based fuels. In this work, we analyse a Chlorella vulgaris microalgae biorefinery that aims to produce biodiesel and renewable diesel from the lipids contained in the algae. The analysis is carried out by decomposing the biorefinery into a suppl...

There is a wide biomass spectrum in the United Arab Emirates (UAE). Twenty three different biomass and fractions local to the UAE including lignocellulose (date palm, Moringa peregrina, mangroves, and garden trimmings), halophytes (Salicornia sinus-persica, Salicornia bigelovii, Halodule uninervis, Halophila ovalis, and Halophila stipulacea), macro...

Demand for non-fossil liquid transport fuels is increasing and biogas to liquid fuels conversion is one possible way to produce liquid fuels. Conversion of natural gas to liquid fuels by Fischer-Tropsch synthesis (FT-synthesis) is an established process applied at industrial scale. Biogas plants have relatively lower throughput and methane concentr...

Landscape and garden trimmings are a continuous stream of green waste and only a small portion of it is recycled through composting. There is a potential for its use as raw material for production of second generation biofuels. In this study trimmings of Bermuda grass and Clerodendrum inerme (Jasmine hedges), which are commonly grown in gardens and...

Optimization and a cost-oriented analysis, including the capital and energy-of-compression costs, were performed to compare propane- and ammonia-refrigeration economizer cycles with and without presaturators. The simulation and optimization to minimize the cost were performed by using the HYSYS simulator and the Peng–Robinson equation of state was...