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

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

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

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

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

Evaluate the blend quality of powders using a simplified mixing law

The research presents an easy to follow approach to evaluate blend quality of particle blends which are complex in shape and vary in size. For some materials simulations with discrete modelling approaches are challenging because of size and shape constrains but also of the access to recourses and knowhow of practitioners in the field using blending equipment for evaluating the blend quality of their products. A significant proportion of bulk handling operations happens in agriculture and related industries e.g. producing fertilisers, handling and storing food such as beans, lentils and rice. Different materials such as mung beans, black eye beans, lentils and rice were blended in a variable speed screw blender. The blender could vary the screw speed and then results taken from experiments were analysed to quantify the blend quality. It was found that a screw speed of 120 rpm gave the highest blend “quality” defined as a50 / 50 percent mix for different materials and blending time intervals. It was also found that the sampling position in the variable speed screw blender mattered because of axial and radial segregation occurring in the blender

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

Automated determination of landslide locations after large trigger events: advantages and disadvantages compared to manual mapping

Earthquakes in mountainous areas can trigger thousands of co-seismic landslides, causing significant damage, hampering relief efforts, and rapidly redistributing sediment across the landscape. Efforts to understand the controls on these landslides rely heavily on manually mapped landslide inventories, but these are costly and time-consuming to collect, and their reproducibility is not typically well constrained. Here we develop a new automated landslide detection algorithm (ALDI) based on pixel-wise NDVI differencing of Landsat time series within Google Earth Engine accounting for seasonality. We compare classified inventories to manually mapped inventories from five recent earthquakes: 2005 Kashmir, 2007 Aisen, 2008 Wenchuan, 2010 Haiti, and 2015 Gorkha. We test the ability of ALDI to recover landslide locations (using ROC curves) and landslide sizes (in terms of landslide area-frequency statistics). We find that ALDI more skilfully identifies landslides than published inventories in 10 of 14 cases when ALDI is locally optimised, and in 8 of 14 cases both when ALDI is globally optimised and in holdback testing. These results reflect both good performance of the automated approach but also surprisingly poor performance of manual mapping, which has implications not only for how future classifiers are tested but also for the interpretations that are based on these inventories. We conclude that ALDI already represents a viable alternative to manual mapping in terms of its ability to identify landslide-affected image pixels. Its fast run-time, cost-free image requirements and near-global coverage make it an attractive alternative with the potential to significantly improve the coverage and quantity of landslide inventories. Its simplicity (pixel-wise analysis only) and parsimony of inputs (optical imagery only) suggests that considerable further improvement should be possible

Limits on the validity of infinite length assumptions for modelling shallow landslides

The infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models. Its assumption that shallow landslides are infinitely long (in a downslope direction) is usually considered valid for natural landslides on the basis that they are generally long relative to their depth. However, this is rarely justified, because the critical length/depth (L/H) ratio below which edge effects become important is unknown. We establish this critical L/H ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two-dimensional slopes, assuming that the difference between the predictions is due to error in the infinite slope method. We test the infinite slope method for six different L/H ratios to find the critical ratio at which its predictions fall within 5% of those from the finite element method. We repeat these tests for 5000 synthetic slopes with a range of failure plane depths, pore water pressures, friction angles, soil cohesions, soil unit weights and slope angles characteristic of natural slopes. We find that: (1) infinite slope stability predictions are consistently too conservative for small L/H ratios; (2) the predictions always converge to within 5% of the finite element benchmarks by a L/H ratio of 25 (i.e. the infinite slope assumption is reasonable for landslides 25 times longer than they are deep); but (3) they can converge at much lower ratios depending on slope properties, particularly for low cohesion soils. The implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse (e.g. >25 m). However, it may also be valid even at much finer grid resolutions (e.g. 1 m), because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have L/H ratios less than 25

Sargassum – Golden menace or golden opportunity

The brown seaweed Sargassum muticum is an invasive species to the coasts of the British Isles, mainland Europe and North America. Attempts at its eradication and control have generally not been successful, although time-consuming and costly. The environmental and economic costs of biological invasions of non-native species in the early part of the last decade were estimated to be worth ~ US$1.4 trillion per year, globally, equivalent to 5$ 29.2 billion in on-shore spending in 2014. One of the key recommendations of the Caribbean Sea Commission in 2015 for addressing the threat of the Sargassum is to support research on commercial uses of Sargassum. Commercial exploration of this biomass for food, fuel and pharmaceutical products could encourage its harvesting and control. Sargassum has a naturally high content of antioxidants, carotenoids and phenols, including the well-known anti-cancer compound fucoxanthin, making this species a potential source of a range of pharmaceutically relevant materials. Macroalgae may also be a potential source of fuel. This paper discusses the use of Sargassum for both fuel and high value products together with the processes required to exploit it, especially on handling the discontinuity of supply