Influence of particle size on the carbonation of stainless steel slag for CO2 storage

Abstract The main aims of this work were to assess the CO2 storage capacity of different particle size fractions of stainless steel slag subjected to accelerated carbonation under mild operating conditions, to study the influence on reaction kinetics of some of the main operating parameters (temperature, pressure and liquid to solid ratio) and to determine the effects of the process on slag mineralogy and leaching behavior. Maximum CO2 uptakes of 130 g CO2/kg residues were measured for the finest grain size and decreased with particle size owing to differences in reacting species availability and specific surface. Process kinetics proved relatively fast, achieving completion in around 2 hours with a CO2 pressure of 3 bar and an optimal liquid to solid ratio of 0.4; temperature was the parameter that most influenced CO2 uptake, due to its enhancement effect on silicates dissolution

Comparison of different reaction routes for carbonation of APC residues

Abstract This paper analyses and compares the results of accelerated carbonation experiments for CO2 storage carried out on the air pollution control (APC) residues of a waste incineration plant, via both the dry and the wet route. The two routes achieved a similar maximum calcium conversion to carbonates (around 65%) corresponding to a potential CO2 storage capacity of 250 g/kg residues. For the dry route, maximum conversion was achieved in a few minutes at 400 ∘C under a 10% CO2 atmosphere, whereas for the wet route it was obtained in about 10 minutes under a 100% CO2 atmosphere, with a liquid to solid ratio of 0.2, at 30 ∘C and 3 bar, or without water addition at 50 ∘C. These results suggest that carbonation of APC residues, and possibly of other combustion residues, through either the dry or wet route, may be effectively applied for CO2 storage, at least in the niche market of waste incineration

Biohydrogen production from food waste: Influence of the inoculum-to-substrate ratio

In this study, the influence of the inoculum-to-substrate ratio (ISR) on dark fermentative hydrogen production from food waste (FW) was evaluated. ISR values ranging from 0.05 to 0.25 g VSinoculum/g VSsubstrate were investigated by performing batch tests at T = 39 °C and pH = 6.5, the latter being the optimal value identified based on a previous study. The ISR was found to affect the fermentation process, clearly showing that an adequate ISR is essential in order to optimise the process kinetics and the H2 yield. An ISR of 0.14 proved to optimum, leading to a maximum H2 yield of 88.8 L H2/kg VSFW and a maximum production rate of 10.8 L H2/kg VSFW∙h. The analysis of the fermentation products indicated that the observed highest H2 production mostly derived from the typical acetate/butyrate-type fermentation

Anaerobic Biodegradability of Commercial Bioplastic Products: Systematic Bibliographic Analysis and Critical Assessment of the Latest Advances

Bioplastics have entered everyday life as a potential sustainable substitute for commodity plastics. However, still further progress should be made to clarify their degradation behavior under controlled and uncontrolled conditions. The wide array of biopolymers and commercial blends available make predicting the biodegradation degree and kinetics quite a complex issue that requires specific knowledge of the multiple factors affecting the degradation process. This paper summarizes the main scientific literature on anaerobic digestion of biodegradable plastics through a general bibliographic analysis and a more detailed discussion of specific results from relevant experimental studies. The critical analysis of literature data initially included 275 scientific references, which were then screened for duplication/pertinence/relevance. The screened references were analyzed to derive some general features of the research profile, trends, and evolution in the field of anaerobic biodegradation of bioplastics. The second stage of the analysis involved extracting detailed results about bioplastic degradability under anaerobic conditions by screening analytical and performance data on biodegradation performance for different types of bioplastic products and different anaerobic biodegradation conditions, with a particular emphasis on the most recent data. A critical overview of existing biopolymers is presented, along with their properties and degradation mechanisms and the operating parameters influencing/enhancing the degradation process under anaerobic conditions

Accelerated carbonation of steel slags using CO2 diluted sources: CO2 uptakes and energy requirements

This work presents the results of carbonation experiments performed on Basic Oxygen Furnace (BOF) steel slag samples employing gas mixtures containing 40 and 10% CO2 vol. simulating the gaseous effluents of gasification and combustion processes respectively, as well as 100% CO2 for comparison purposes. Two routes were tested, the slurry-phase (L/S = 5 l/kg, T = 100°C and Ptot = 10 bar) and the thin-film (L/S = 0.3–0.4 l kg, T = 50°C and Ptot = 7–10 bar) routes. For each one, the CO2 uptake achieved as a function of the reaction time was analyzed and on this basis, the energy requirements associated with each carbonation route and gas mixture composition were estimated considering to store the CO2 emissions of a medium size natural gas fired power plant (20 MW). For the slurry-phase route, maximum CO2 uptakes ranged from around 8% at 10% CO2, to 21.1% (BOF-a) and 29.2% (BOF-b) at 40% CO2 and 32.5% (BOF-a) and 40.3% (BOF-b) at 100% CO2. For the thin-film route, maximum uptakes of 13% (BOF-c) and 19.5% (BOF-d) at 40% CO2, and 17.8% (BOF-c) and 20.2% (BOF-d) at 100% were attained. The energy requirements of the two analyzed process routes appeared to depend chiefly on the CO2 uptake of the slag. For both process route, the minimum overall energy requirements were found for the tests with 40% CO2 flows (i.e., 1400−1600 MJ/tCO2 for the slurry-phase and 2220 – 2550 MJ/tCO2 for the thin-film route)

Two-Stage Process for Energy Valorization of Cheese Whey through Bio-Electrochemical Hydrogen Production Coupled with Microbial Fuel Cell

The present work investigates a two-stage process scheme for cheese whey valorization through energy recovery in different forms by means of bio-electrochemical systems. The first stage consisted of an integrated bio-electrochemical process for H2 and electricity production. This combined dark fermentation with an electrochemical system with the aim of overcoming the typical thermodynamic/biochemical limitations of fermentation and enhancing H2 recovery. The second treatment stage involved a single-chamber microbial fuel cell, featuring an innovative configuration consisting of four air cathodes with fly ash as the oxygen reduction catalyst. The bio-electrochemical process performed in the first stage achieved promising results, displaying a three-times higher H2 production yield compared to conventional dark fermentation. In addition, the experiments using the MFC in the second stage were found to successfully exploit the effluent from the first stage, with COD removal yields of 86% +/- 8% and energy recovery with a maximum current output of 1.6 mA and a maximum power density of 1.2 W/m3

Combined application of Life Cycle Assessment and linear programming to evaluate food waste-to-food strategies: Seeking for answers in the nexus approach

The great concern regarding food loss (FL) has been studied previously, but in an isolated way, disregarding interdependencies with other areas. This paper aims to go a step further by proposing a new procedure to assess different waste management alternatives based on the nexus approach by means of an integrated Water-Energy-Food-Climate Nexus Index (WEFCNI). The environmental profile of the waste management techniques is determined using Life Cycle Assessment (LCA) which, in combination with Linear Programming (LP), explores the optimal aggregation of weighting factors that lead to an aggregated nexus index. The management of residues from the anchovy canning industry in Cantabria (Spain) has been used as a case study, considering the three current applied alternatives: (i) valorisation of FL as animal feed in aquaculture (food waste-to-food approach), (ii) incineration of FL with energy recovery, and (iii) landfilling with biogas recovery. The last two considered the use of energy recovered to produce a new aquaculture product (food waste-to-energy-to-food scenarios). The results indicate that incineration is the best performing scenario when the nutritional energy provided by the valorisation alternative is not high enough and the valorisation technology presents the highest water consumption. Therefore, a minimisation in the consumption of natural resources is suggested in order to improve the application of circular economy within the sector. The use of the nexus index as an environmental management tool is extendable to any food system with the aim of facilitating the decision-making process in the development of more sustainable products.The authors thank the Ministry of Economy and Competitiveness of the Spanish Government for its financial support via the project GeSAC-Conserva: Sustainable Management of the Cantabrian Anchovies (CTM2013-43539-R) and to Julia Celaya for her technical support. Jara Laso thanks the Ministry of Economy and Competitiveness of Spanish Government for its financial support via the research fellowship BES-2014-069368. Pere Fullana and Alba Bala thank the UNESCO Chair in Life Cycle and Climate Change. Ian Vázquez-Rowe thanks the Pontificia Universidad Católica del Perú for financing the Walaya Project

Organic waste biorefineries: looking towards implementation

The concept of biorefinery expands the possibilities to extract value from organic matter in form of either bespoke crops or organic waste. The viability of biorefinery schemes depends on the recovery of higher-value chemicals with potential for a wide distribution and an untapped marketability. The feasibility of biorefining organic waste is enhanced by the fact that the biorefinery will typically receive a waste management fee for accepting organic waste. The development and implementation of waste biorefinery concepts can open up a wide array of possibilities to shift waste management towards higher sustainability. However, barriers encompassing environmental, technical, economic, logistic, social and legislative aspects need to be overcome. For instance, waste biorefineries are likely to be complex systems due to the variability, heterogeneity and low purity of waste materials as opposed to dedicated biomasses. This article discusses the drivers that can make the biorefinery concept applicable to waste management and the possibilities for its development to full scale. Technological, strategic and market constraints affect the successful implementations of these systems. Fluctuations in waste characteristics, the level of contamination in the organic waste fraction, the proximity of the organic waste resource, the markets for the biorefinery products, the potential for integration with other industrial processes and disposal of final residues are all critical aspects requiring detailed analysis. Furthermore, interventions from policy makers are necessary to foster sustainable bio-based solutions for waste management

Waste and climate change: Can appropriate management strategies contribute to mitigation?

[No abstract available