Carlos Alvarez

Universidad de Cádiz | UCA · Department of Chemical Engineering and Food Technology

Passively aerated biological pretreatment was applied to four different lignocellulosic biomasses with varying fiber content profiles: sugar beet pulp (SBP), brewery bagasse (BB), rice husk (RH), and orange peel (OP). In order to analyze the organic matter solubilization yield at 24 and 48 h, different percentages of activated sewage sludge (2.5-10...

Rugulopteryx okamurae is an invasive brown alga causing severe environmental and economic problems on the western Mediterranean coasts. Thus, in addition to the difficulties caused to the fishing and tourism sectors, there is a need to manage its accumulation on the beaches. This work aims to valorise this waste by using it as raw material for prod...

This study was focused on bio-hydrogen production from thermophilic dry anaerobic acidogenic co-digestion (55 °C and 20 % of total solids) of pre-composted mixtures of organic fraction of municipal solid waste (OFMSW) and food waste (FW). Three different mixture ratios of OFMSW:FW (80:20, 70:30 and 50:50) have been tested. The application of pre-co...

Chemical Engineering courses are often designed to be divided into two types of lessons: lecture and experimental. In the second one, students develop the knowledge in a hands-on way by attending a pilot plant equipped with different instruments. Hence, a thorough understanding of the different unit operations is needed and, therefore, the implicat...

Microvawe irradiation has been applied to solubilise the organic matter from the invasive seaweed Rugulopterix okamurae as pretreatment for two conventional biological processes: enzyme hydrolysis (EH) for obtaining reducing sugars (RS) and dark fermentation (DF) for obtaining volatile fatty acids (VFAs). As operational conditions for the microwave...

This work consists of a long-term (621 days) experimental study about biogas production from sun dried sugar beet pulp and cow manure. Thermophilic (55 °C) anaerobic co-digestion was performed in semi-continuous reactors, testing ten hydraulic retention times (30-3 days) (HRTs) and organic loading rates (2–24 gVS/Lreactor∙d) (OLRs). Results showed...

It is well-known that brown macroalgae can be used as a source of valuable sugars with different biological activities, but its polymeric macrostructures should be hydrolyzed for obtaining an acceptable yield. This study deals with the production of free sugars by the enzymatic hydrolysis of optimized biologically pretreated brown seaweed. The biol...

Polyhydroxyalkanoates (PHAs) production from lignocellulosic biomass using mixed microbial cultures (MMC) is a potential cheap alternative for reducing the use of petroleum-based plastics. In this study, an MMC adapted to acidogenic effluent from dark fermentation (DF) of exhausted sugar beet cossettes (ESBC) has been tested in order to determine i...

Organic fraction of municipal solid waste (OFMSW) is an ideal substrate for biogas production; however, complex chemical structure and being heterogeneous obstruct its biotransformation in anaerobic digestion (AD) process. Thermal pre-treatment of OFMSW has been suggested to enhance the solubilization and improve the anaerobic digestibility of OFMS...

A circular economy is an economic system aimed at minimizing waste and making the most of resources. Anaerobic digestion (AD) is a technology of great interest for the circular economy approach since it combines the treatment of high organic load wastes with the production of energy vectors (EV): biogas and biohydrogen. In this chapter, a brief des...

The growing demand for effective waste management strategies targeting a sustainable transition from a fossil fuel-based economy to a resource-efficient economy heightens the need for new biotechnological processes and innovations. Organic fraction of municipal solid waste (OFMSW) and sludge produced in wastewater treatment plants (WWTPs) are two o...

Polyhydroxyalkanoates (PHAs) are a family of bioproduced and biodegradable polyesters and a sustainable alternative to fossil-based plastics, yet their high production costs restrict them from traditional nonbiodegradable polymers. For an economical approach in the production of bioplastics, two factors must be considered: the use of biomass as raw...

Sugar beet by-products are a lignocellulosic waste generated from sugar beet industry during the sugar production process and stand out for their high carbon content. Moreover, cow manure (CM) is hugely produced in rural areas and livestock industry, which requires proper disposal. Anaerobic digestion of such organic wastes has shown to be a suitab...

Carbohydrates from vegetal biomass (wood and agricultural biomass). [...]

Biogas production through anaerobic digestion has proven to be one of the most important pillars of the transition into the circular economy concept, a sustainable approach for biorefinery. This work aims to extend and improve knowledge in the anaerobic co-digestion of complementary substrates, given insights into wastes biodegradability and the in...

Lignocellulosic biomass, comprising of cellulose, hemicellulose, and lignin, is a difficult-to-degrade substrate when subjected to anaerobic digestion. Hydrothermal pretreatment of lignocellulosic biomass could enhance the process performance by increasing the generation of methane, hydrogen, and bioethanol. The recalcitrants (furfurals, and 5-HMF)...

In this paper, the viability of thermophilic anaerobic co-digestion of exhausted sugar beet pulp (ESBP) and pig manure (PM) was evaluated. The effect of the proportion of ESBP on biogas production was investigated by using a series of lab-scale batch assays, in duplicates. The following five ESBP:PM mixture ratios were studied: 0:100, 10:90, 25:75,...

Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) offers the possibility of a clean and renewable energy source – i.e. biogas. However, OFMSW lacks certain characteristics that may limit its efficacy as such a resource. Bio-resources such as sewage sludge and animal wastes have these characteristics and so may be use...

Effect of hydraulic retention time (HRT) on bio-hydrogen production from co-digestion of organic fraction of municipal solid waste (OFMSW) and mixed sludge (MS) in dry thermophilic conditions (55°C and 20% total solids) was investigated. A decreasing sequence of six HRTs, from 2.9 to 0.8-days, was performed to evaluate the stability of the system a...

In this paper, a destabilization episode in a semi-continuous dry thermophilic acidogenic reactor for the co-digestion of organic fraction of municipal solid waste (OFMSW) and food waste (FW) was induced. The aim was to determinate the effect of the organic loading rate (OLR) and co-substrate ratio on hydrogen production by dark fermentation. OLR w...

A series of batch anaerobic digestion assays were implemented to determine the influence of total solids concentration on the anaerobic digestion of sugar beet by-products and their co-digestion with two kind of livestock manures (pig and cow manures). The two total solid concentrations studied were 8% and 5%. Total solids contents above 8% were no...

Exhausted sugar beet cossettes (ESBC) are one of the main byproducts generated in the sugar industries. The pellets of dried pulp of ESBC used in this study are composed of 85% beet pulp and 15% molasses and have a high lignocellulosic-type organic matter content (91% volatile solids) and a nitrogen deficiency. Mesophilic anaerobic co-digestion in...

The effect of mesophilic anaerobic co-digestion of dried pellets of exhausted sugar beet cossettes (ESBC-DP) and cow manure (CM) on the enhancement of methane generation and process stability were studied with the aim to select the best substrate mixture ratio. A series of batch experiments was conducted using the following five mixture ratios of E...

Dried pellet of exhausted sugar beet cossettes were digested alone and combined with cow manure as co-substrate in a mesophilic semi-continuous anaerobic system. In single digestion assay, the stable biogas production and stable reactor operation was observed at the hydraulic retention time (HRT) of 20days (OLR: 3.26gVS/Lreactord) which was the min...

Anaerobic co-digestion of dried pellet of exhausted sugar beet cossettes (ESBC-DP) with pig manure (PM) was investigated in a semi-continuous stirred tank reactor (SSTR) under mesophilic conditions. Seven hydraulic retention times (HRT) from 20 to 5days were tested with the aim to evaluate the methane productivities and volatile solids (VS) removal...

The organic fraction of municipal solid waste (OFMSW) usually contains high lignocellulosic and fatty fractions. These fractions are well-known to be a hard biodegradable substrate for biological treatments and its presence involves limitations on the performance of anaerobic processes. To avoid this, thermochemical pretreatments have been applied...

BACKGROUND: For the first time, low intensity ultrasonication was applied to stimulate the biological activities during aerobic digestion of municipal waste activated sludge (AS). The specific oxygen uptake rate (SOUR) analysis was performed to investigate the sono-biostimulation effects on AS activity. RESULTS: The highest improvement of 60% in SO...

Batch dry-thermophilic anaerobic co-digestion (55°C) of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) for hydrogen production was studied under several sludge combinations (primary sludge, PS; waste activated sludge, WAS; and mixed sludge, MS), TS concentrations (10-25%) and mixing ratios of OFMSW and SS (1:1, 2.5:1, 5:1,...

The main objective of this work has been to analyze the effect of hydraulic retention time (HRT) on the hydrogen production from the organic fraction of municipal solid waste (OFMSW) coming from a full-scale mechanical–biological-treatment (MBT) plant. Furthermore, it has also been studied, simultaneously, the effect of HRT on the solubilization of...

In anaerobic processes, the volatile fatty acid profile (VFA) is closely related with the methanogenic activity and, hence, the knowledge of the relationship between these two parameters (VFA evolution and methane production) is fundamental to characterize the behavior of anaerobic reactors for treatment of organic wastes.In this study, a destabili...

The start-up strategies for thermophilic anaerobic reactors usually consist of an initial mesophilic stage (35°C), with an approximate duration of 185 days, and a subsequent thermophilic stage (55°C), which normally requires around 60 days to achieve the system stabilizatio. During the first 8-10 days of the mesophilic stage, the reactor is not fed...

Thermochemical and biological pretreatments have been applied to the organic fraction of the municipal solid wastes (OFMSW) coming from an industrial 30 mm-trommel placed in a full-scale mechanical–biological treatment (MBT) plant in order to study their effects on the organic matter solubilization yield and the biomethanization process.To compare...

The influence of particle size and organic matter content of organic fraction of municipal solid waste (OFMSW) in the overall kinetics of dry (30% total solids) thermophilic (55°C) anaerobic digestion have been studied in a semi-continuous stirred tank reactor (SSTR). Two types of wastes were used: synthetic OFMSW (average particle size of 1mm; 0.7...

The application of the anaerobic digestion for the treatment of the industrial organic fraction of municipal solid waste (OFMSW) has currently been of special interest. The main barrier in the treatment of this type or organic waste is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical,...

This paper studies the effect of both thermochemical (under different pressures, temperatures and alkaline agent dosage) and biological (using mature compost, sludge and the fungus Aspergillus awamori) pretreatments on the kinetic of dry-thermophilic (20% Total Solids and 55°C) anaerobic digestion of industrial organic fraction of the municipal sol...

In this paper, the critical and the optimum conditions for thermophilic-dry anaerobic digestion have been determined employing two types of Organic Fraction of Municipal Solid Waste (OFMSW): synthetic (average particle size of 1mm) and industrial (average particle size of 30mm). On the basis of the methane production rate and the removal percentage...

Solid retention time (SRT) is a very important operational variable in continuous and semicontinuous waste treatment processes since the organic matter removal efficiency--expressed in terms of percentage of Dissolved Organic Carbon (% DOC) or Volatile Solids (% VS) removed--and the biogas or methane production are closely related with the SRT impo...

The anaerobic digestion (AD) process for waste stabilization is a very attractive option in managing the organic fraction of municipal solid waste (OFMSW); hence, many industrial OFMSW biomethanation plants are operating today all around the world. In general, the literature contains many operational and control parameters to check the behavior of...

The work presented here concerns the start-up and stabilization stages of a Continuous Stirred Tank Reactor (CSTR) semicontinuously fed for the treatment of the Organic Fraction of Municipal Solid Waste (OFMSW) through anaerobic digestion at thermophilic temperature range (55 degrees C) and dry conditions (30% Total Solids). The procedure reported...

El acuífero de Sotogrande, con una superficie de unos 30 km2, está situado en el litoral mediterráneo de la provincia de Cádiz, cerca del límite con la provincia de Málaga. Se trata de un acuífero detrítico costero enclavado en una comarca cuya principal actividad económica es la turística, orientada a un sector de población de alto poder adquisiti...

Laboratory studies on dry anaerobic digestion of mixture of organic fraction of municipal solid waste, mainly putrescible fraction selected source (SS–OFMSW), and others organic compounds (garden waste, rice hulls, animal waste and sludge) demonstrated the optimum efficiency at 35 % total solid and thermophilic conditions (55 °C). Five starts up an...

The aim of this work was to optimize the start up and stabilization phase of SEBAC (Sequential Batch Anaerobic Composting) digestion of the organic fraction from urban solid waste combined or not combined with swine digest waste. Four different processes were studied in which the initial composition of the reactors involved in the process was modif...