Beatriz Fidalgo

Pyrolysis of fast-growing aquatic biomass - Lemna minor (duckweed): characterization of pyrolysis products.

The aim of this work was to conduct the experimental study of pyrolysis of fast-growing aquatic biomass -Lemna minor (commonly known as duckweed) with the emphasis on the characterization of main products of pyrolysis. The yields of pyrolysis gas, pyrolytic oil (bio-oil) and char were determined as a function of pyrolysis temperature and the sweep gas (Ar) flow rate. Thermogravimetric/differential thermogravimetric (TG/DTG) analyses of duckweed samples in inert (helium gas) and oxidative (air) atmosphere revealed differences in the TG/DTG patterns obtained for duckweed and typical plant biomass. The bio-oil samples produced by duckweed pyrolysis at different reaction conditions were analyzed using GC-MS technique. It was found that pyrolysis temperature had minor effect on the bio-oil product slate, but exerted major influence on the relative quantities of the individual pyrolysis products obtained. While, the residence time of the pyrolysis vapors had negligible effect on the yield and composition of the duckweed pyrolysis products.

Carbon Materials as Catalysts for Decomposition and CO2 Reforming of Methane: A Review

Abstract The decomposition and CO2 reforming of methane, respectively, are promising alternatives to industrial steam methane reforming. In recent years, research has been focused on the development of catalysts that can operate without getting deactivated by carbon deposition, where, in particular, carbon catalysts have shown positive results. In this work, the role of carbon materials in heterogeneous catalysis is assessed and publications on methane decomposition and CO2 reforming of methane over carbon materials are reviewed. The influence of textural properties (BET surface area and micropore volume, etc.) and oxygen surface groups on the catalytic activity of carbon materials are discussed. In addition, this review examines how activated carbon and carbon black catalysts, which are the most commonly used carbon catalysts, are deactivated. Characteristics of the carbon deposits from methane are discussed and the influence of the reactivity to CO2 of fresh carbon and carbonaceous deposits for high and steady conversion during CO2 reforming of CH4 are also considered.

Energy recovery from human faeces via gasification: A thermodynamic equilibrium modelling approach.

Highlights • On dry basis, typical human faeces contain 83 wt.% organic fraction and 17 wt.% ash.• The LHV of dry human faeces ranged from 19 to 22 MJ/kg, values similar to wood biomass.• Syngas from dry human faeces had LHV of 15–17 MJ/kg at equivalence ratio of ∼0.31.• Energy is best recovered from moist human faeces at equivalence ratio above 0.6.• Recoverable exergy potential from moist human faeces can be up to 15 MJ/kg.

An experimental investigation of the combustion performance of human faeces

Highlights • Dry human faeces have a Higher Heating Value (HHV) of 24 MJ/kg.• Faeces combustion was investigated using a bench-scale downdraft combustor test rig.• Combustion temperature of 431–558 °C was achieved at air flow rate of 10–18 L/min.• Fuel burn rate of 1.5–2.3 g/min was achieved at air flow rate of 10–18 L/min.• Combustion temperature of up to 600 ± 10 °C can handle 60 wt.% moisture in faeces.

Mixtures of Steel-Making Slag and Carbons as Catalyst for Microwave-Assisted Dry Reforming of CH4

The use of steel-making slag as catalysts for microwave-assisted dry reforming of CH4 was studied. Two carbon materials (an activated carbon and a metallurgical coke), mixtures of the carbon materials and Fe-rich slag, and mixtures of the carbon materials and Ni/Al2O3 were tested as catalysts. The mixtures of slag with carbons gave rise to higher and steadier conversions than those achieved over the carbon materials alone. In addition, the use of the metallurgical coke mixed with metal-rich catalysts gave rise to remarkable results. Thus, no CH4 and CO2 conversions were achieved when coke was used alone, whereas high conversions were obtained when it was mixed with the metal-rich catalysts.

Conceptual energy and water recovery system for self-sustained nano membrane toilet

Highlights • Energy and water recovery system from human excreta is modelled in Aspen Plus.• The Nano Membrane Toilet is proven to be a self-sustained system.• Up to 87% of total amount of water fed to the system can be recovered.• Net power output of the entire system is similar to the USB port peak power (2–6 W).• The specific net power output varies between 23.1 and 69.2 Wh/kgsettledsolids.

Thermodynamic analysis of a gamma type Stirling engine in an energy recovery system

Highlights • The performance of Stirling engine integrated to a micro-combustor in the NMT system was investigated.• Energy recovery and power generation of 27u202fWh/h from combustion of human faeces.• The integrated position of the Stirling engine to the micro-combustor is highly paramount.• Sensitivity of the performance of the Stirling engine to working gas temperature.• Requirements for optimum performance of the Stirling engine for integration with micro-combustor.

Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces

Highlights • Ignition, gasification and combustion of simulant and real faeces were studied.• Trials using fuel flowrates of 1.2u202fg/min and 7.5–8u202fL/min of air were carried out.• Mean temperatures of 440–670u202f°C allowed self-sustained combustion.• Maximum temperatures reached for real faeces were in the range of 1210–1240u202f°C.• Combustion trials lasted up to 160u202fmin without external heat supply.

Probabilistic performance assessment of complex energy process systems – The case of a self-sustained sanitation system

Highlights • A probabilistic model is developed to assess the performance of an NMT.• Energy and environmental performance uncertainties of the system are qualified.• A realistic prediction of the energy and environmental performance of the system.• Probabilistic approach can be applied in other complex engineering systems.

Conventional and microwave-heated oxygen pulsing techniques on metal-doped activated carbons

Conventional and microwave-heated oxygen pulsing techniques on metal-doped activated carbons to achieve a controlled meso/micropore structure were investigated. The gas pulsing experiments consisted of repeated cycles. Each cycle consists of an oxidising stage, under O2/Ar atmosphere and constant temperature, and a burn-off stage, under N2 atmosphere at variable temperature (heating and cooling). The porosity of the carbons was analysed by nitrogen adsorption at −196xa0°C. Two different activated carbons, Cu-doped BPL (BPL-Cu) and ASC, were used as raw materials. The commercial activated carbon ASC showed higher reactivity towards O2, due to the catalytic effect of the metals (mainly, Cu and Cr) that are on the carbon surface and their better dispersion. After several pulses, ASC underwent a moderate increase in the micropore volume and a significant increase in mesopore volume. BPL-Cu showed a higher increase in microporosity than mesoporosity, giving rise to a meso/micropore volume ratio lower than that of the original BPL-Cu. Oxygen pulsing technique was carried out in a conventional furnace and in a microwave oven. Conventional and microwave-heated oxygen pulsing on ASC yielded similar textural development. However, the time required under microwave heating was remarkably reduced respect to conventional heating (around 2.5 times less), which suggests that microwave-heated oxygen pulsing technique would be an interesting alternative to conventional activation.