The cleanability of stainless steel used as a food contact surface: an updated short review

The effect of surface roughness on the cleanability of stainless steel as used in the foodindustry

A review of the harvesting of micro-algae for biofuel production

Many researchers consider efficient harvesting is the major challenge of commercialising micro-algal biofuel. Although micro-algal biomass can be ‘energy rich’, the growth of algae in dilute suspension at around 0.02–0.05 % dry solids poses considerable challenges in achieving a viable energy balance in micro-algal biofuel process operations. Additional challenges of micro-algae harvesting come from the small size of micro-algal cells, the similarity of density of the algal cells to the growth medium, the negative surface charge on the algae and the algal growth rates which require frequent harvesting compared to terrestrial plants. Algae can be harvested by a number of methods; sedimentation, flocculation, flotation, centrifugation and filtration or a combination of any of these. This paper reviews the various methods of harvesting and dewatering micro-algae for the production of biofuel. There appears to be no one method or combination of harvesting methods suited to all micro-algae and harvesting method will have a considerable influence on the design and operation of both upstream and downstream processes in an overall micro-algal biofuel production process

Synthesis of cubic diamond in the graphite-magnesium carbonate and graphite-K2Mg(CO3)(2) systems at high pressure of 9-10 GPa region

Cubic diamond was synthesized with two systems, (1) graphite with pure magnesium carbonate (magnesite) and (2) graphite with mixed potassium and magnesium carbonate at pressures and temperatures above 9.5 GPa, 1600 degrees C and 9 GPa, 1650 degrees C, respectively. At these conditions (1) the pure magnesite is solid, whereas (2) the mixed carbonate exists as a melt. In this pressure range, graphite seems to be partially transformed into hexagonal diamond. Measured carbon isotope delta(13)C values for all the materials suggest that the origin of the carbon source to form cubic diamond was the initial graphite powder, and not the carbonates

Energy balance of biogas production from microalgae: Development of an energy and mass balance model

The paper describes the construction of a mechanistic energy balance model for the production of biogas from anaerobic digestion of micro-algal biomass grown in raceways, based on simple principles and taking into account growth, harvesting and energy extraction. The model compares operational energy inputs with the calorific value of the output biomass in terms of the energy return on operational energy invested (EROOI). Initial results indicate that production of microalgal biogas will require: a) Favourable climatic conditions. The production of microalgal biofuel in UK would be energetically challenging at best. b) Achievement of ‘reasonable yields’ equivalent to ~3% photosynthetic efficiency (25 g m-2 day-1). c) Low or no cost and embodied energy sources of CO2 and nutrients from flue gas and wastewater. d) Mesophilic rather than thermophilic digestion. e) Adequate conversion of the organic carbon to biogas (≥ 60%). The model itself provides a powerful assessment tool both for comparison of alternative options and potentially for benchmarking real schemes

Comparison between automated anaerobic digestion test systems for determination of biochemical methane potential of cellulose

This study investigated the use of two automated systems, the Automatic Methane Potential Test System II (AMPTS II) and the CJC lab system, a newly developed system, to measure BMP of cellulose

Methods of energy extraction from microalgal biomass: a review

The potential of algal biomass as a source of liquid and gaseous biofuels is a highly topical theme, The process operations for algal biofuel production can be grouped into three areas: growth, harvesting and energy extraction, with a wide range of combinations of unit operations that can form a microalgal biofuel production system, but as yet there is no successful economically viable commercial system producing biofuel. This suggests that there are major technical and engineering difficulties to be resolved before economic algal biofuel production can be achieved. This article briefly reviews the methods by which useful energy may be extracted from microalgae biomass: (a) direct combustion, (b) pyrolysis,(c) gasification, (d) liquefaction, (e) hydrogen production by biochemical processes in certain algae, (f) fuel cells, (g) fermentation to bioethanol, (h) transesterification to biodiesel, (i) anaerobic digestion

Effects of centrifugal stress on cell disruption and glycerol leakage from Dunaliella salina

Dunaliella salina accumulates large amounts of intracellular glycerol in response to the increases in salt concentration, thus is a potential source for producing fuel grade glycerol as an alternative to biodiesel-derived crude glycerol. D. salina lacks a cell wall; therefore the mode of harvesting Dunaliella cells is critical to avoid cell disruption caused by extreme engineering conditions. This study explored cell disruption and glycerol leakage of D. salina under various centrifugal stresses during cell harvesting. Results show a centrifugal g-force lower than 5000 g caused little cell disruption, while a g-force higher than 9000 g led to ~40 % loss of the intact cells and glycerol yields from the recovered algal pellets. Theoretical calculations of the centrifugal stresses that could rupture Dunaliella cells were in agreement with the experimental results, indicating optimisation of centrifugation conditions is important for recovering intact cells of from D. salina enriched in glycerol

Slow pyrolysis as a method for the destruction of Japanese wireweed, Sargassum muticum

Japanese wireweed, Sargassum muticum is an invasive species to Great Britain, which might be controlled by harvesting it for energy and chemicals. Pyrolysis is the thermal decomposition of the organic components of dry biomass by heating in the absence of air. The distribution of matter between solid, liquid and syngas depends on the biomass and the pyrolysis temperature and time. Slow pyrolysis with lower temperatures (~ 400 oC) tends to produce more solid char. Pyrolysis char can be an effective soil ameliorant, a sequestration agent due to its stability or burned as a fuel. The research attempts to answer the question: Could slow pyrolysis be an energy efficient means for the destruction of Japanese wireweed and produce a potential product, biochar? A simple test rig was developed to establish the yield of biochar, biocrude and syngas from the slow pyrolysis of Sargassum muticum. An energy balance was calculated using compositional data from the analysis of the seaweed feedstock, higher heating values (HHV) from bomb-calorimetry and literature values. The energy required to heat 1 kg of dry seaweed by 400 oC for slow pyrolysis was estimated at 0.5 MJ. The HHV of syngas and biocrude produced from the pyrolysis totalled 2.9 MJ. There is, therefore, sufficient energy in the biocrude and syngas fractions produced by the pyrolysis of seaweed to power the process and produce useful biochar, but insufficient energy for drying