Title: Energetic Assessment of SCWG Experiments with Reed Canary Grass and Ethanol Solution on Laboratory and Pilot Scale

Authors: Julian Dutzi, Nikolaos Boukis, Jörg Sauer

Publication Year: 2023

Proposed by: Nikolaos Boukis

Project Areas: Supercritical water, Biomass, Gasification

Abstract

The energetic assessment of biomass conversion processes is important for evaluating their application potential. Process energy efficiency is often evaluated based on simulation results for processes under idealized conditions. The present work uses data from a laboratory plant to perform an evaluation of the supercritical water gasification (SCWG). For this purpose, experiments were conducted with two types of feedstock, Reed Canary Grass and ethanol. Under the present lab-plant configuration, a cold gas efficiency of up to 79% could be reached, which is comparable to the gasification of biomass in fluidized-bed gasifiers or entrained-flow gasifiers. Based on the obtained data on the produced substances and their distribution, a scale up to pilot plant size was conducted. A model was derived from the available data to energetically assess different SCWG plant sizes based on real laboratory results. This model can be transferred to other feedstocks and other process designs to approximate the optimal size for the used biomass feedstock. The importance of heat recuperation in this process is described in detail based on pilot-scale data.

Title: Process Effluent Recycling in the Supercritical Water Gasification of Dry Biomass

Authors: Julian Dutzi, Nikolaos Boukis and Jörg Sauer

Publication Year: 2023

Proposed by: Nikolaos Boukis

Project Areas: Biomass Resources, Process design, Technologies

Abstract

The influence of process water recycling during the Supercritical Water Gasification (SCWG) of dry biomasses was investigated. Dry biomass has to be diluted with water to a dry matter content of approximately 10 wt.% to gasify it in the process of supercritical water gasification. The treatment of wastewater in the SCWG process is cost intensive due to organic contaminants; therefore, the recycling of the process effluent is attractive. Salt separation is needed to avoid accumulation of salts in the effluents, since salts enhance corrosion rates and might cause blocking of the flow when the effluent is recycled. The grass Reed Canary Grass and grapevines were gasified. The recycling of the process effluent did not influence the composition of the product gas. In both cases the carbon efficiency decreased by 4% when wastewater was used to dilute the biomass. An increase in organic carbon and potassium in the reactor effluent was observed after gasification of the biomass with recycled process effluent. The addition of potassium hydroxide to the feed as a homogenous catalyst needs to be closely monitored and adjusted according to the potassium content of the reactor effluent. Insufficient salt separation proved to be an issue regarding formation of solid deposits in the reaction system.

Title: Optimizing the Design of a Biomass-to-Biofuel Supply Chain Network Using a Decentralized Processing Approach

Authors: Fragkoulis Psathas, Paraskevas N. Georgiou, Athanasios Rentizelas

Publication Year: 2022

Proposed by: Athanasios Rentizelas

Project Areas: Biomass Resources, Biomass Availability

Abstract

When designing biomass-to-biofuel supply chains, the biomass uncertainty, seasonality and geographical dispersion that affect economic viability need to be considered. This work presents a novel methodology that can optimize the design of biofuel supply chains by adopting a decentralized network structure consisting of a mix of fixed and mobile processing facilities. The model considers a variable biomass yield profile and the mobile fast pyrolysis technology. The mixed-integer linear programming model developed identifies the optimal biofuel production and biomass harvesting schedule schemes under the objective of profit maximization. It was applied in the case study of marginal lands in Scotland, which are assumed to be planted with Miscanthus. The trade-offs observed between economies of scale against the transportation costs, the effect of the relocation costs and the contribution of storage capacity were investigated. The results showed that, in most cases, harvesting is most concentrated during the month of the highest biomass yield, provided that storage facilities are available. Storage capacity plays an important role to widen the operational time window of processing facilities since scenarios with restricted or costly storage resulted in facilities of higher capacity operating within a narrower time window, leading to higher investment costs. Relocation costs proved to have a minor share in the total transportation costs.

Title: Soil Compaction in Harvesting Operations of Phalaris Arundincea L.

Authors: Leonardo Bianchini, Riccardo Alemanno, Valerio Di Stefano, Massimo Cecchini and Andrea Colantoni

Publication Year: 2022

Proposed by: Andrea Colantoni (Tuscia University)

Project Areas: Biomass Resources, Biomass Availability, Phytoremediation

Abstract

Tillage and harvesting operations of perennial forage crops have problems with soil compaction. The effects of this phenomenon are soil deterioration with reduced crop performance and yield. This study aims to assess soil disturbance by measuring the level of compaction caused by the harvesting operations of Phalaris arundinacea L. P. arundinacea is a species that lends itself to biomass production and phytoremediation of contaminated soils; it adapts to difficult soil conditions, outperforming other species in terms of ease of planting, cost, maturity time, yield, and contamination levels. The crop was sown in three plots of the experimental teaching farm of the University of Tuscia, Viterbo, Italy. Following a detailed analysis of the chemical–physical characteristics of the soil, minimum tillage was chosen in order to concentrate on harvesting operations, which were carried out with a disc mower coupled to a tractor. This was followed by penetration resistance and soil moisture measurements to verify the incidence of the operations and the effect of the type of crop on compaction. On the study site, measurements were taken at points that the wheels of the tractor had gone over and at points that they had not. The soil analysis results indicate different chemical–physical characteristics between the two areas, the texture being frankly sandy to clayey. Penetration resistance measurements indicated differences for the first 20 cm between the part that was covered by the tractor’s tyres and the part that was left touched but also between the three plots. Moisture influenced penetration resistance. This study provides an evaluation of the first data obtained from a project that will last four years and which will explore the dynamics between soil, cultivation, and harvesting operations, giving a fundamental basis for further investigation of further harvesting operations and soil characteristics, which are crucial for planning and managing crops and reducing impacts on the soil in order to preserve it.

Title: Membrane and Electrochemical Based Technologies for the Decontamination of Exploitable Streams Produced by Thermochemical Processing of Contaminated Biomass

Authors: Dimitrios Koutsonikolas, George Karagiannakis, Konstantinos Plakas, Vasileios Chatzis, George Skevis, Paola Giudicianni, Davide Amato, Pino Sabia, Nikolaos Boukis, Katharina Stoll

Publication Year: 2022

Proposed by: Nikolaos Boukis

Project Areas: Biomass thermochemical conversion

Abstract

Phytoremediation is an emerging concept for contaminated soil restoration via the use of resilient plants that can absorb soil contaminants. The harvested contaminated biomass can be thermochemically converted to energy carriers/chemicals, linking soil decontamination with biomass-to-energy and aligning with circular economy principles. Two thermochemical conversion steps of contaminated biomass, both used for contaminated biomass treatment/exploitation, are considered: Supercritical Water Gasification and Fast Pyrolysis. For the former, the vast majority of contaminants are transferred into liquid and gaseous effluents, and thus the application of purification steps is necessary prior to further processing. In Fast Pyrolysis, contaminants are mainly retained in the solid phase, but a part appears in the liquid phase due to fine solids entrainment. Contaminants include heavy metals, particulate matter, and hydrogen sulfide. The purified streams allow the in-process re-use of water for the Super Critical Water Gasification, the sulfur-free catalytic conversion of the fuel-rich gaseous stream of the same process into liquid fuels and recovery of an exploitable bio-oil rich stream from the Fast Pyrolysis. Considering the fundamental importance of purification/decontamination to exploit the aforementioned streams in an integrated context, a review of available such technologies is conducted, and options are shortlisted. Technologies of choice include polymeric-based membrane gas absorption for desulfurization, electrooxidation/electrocoagulation for the liquid product of Supercritical Water Gasification and microfiltration via ceramic membranes for fine solids removal from the Fast Pyrolysis bio-oil. Challenges, risks, and suitable strategies to implement these options in the context of biomass-to-energy conversion are discussed and recommendations are made.