Energy balance of biogas production from microalgae: Effect of harvesting method, multiple raceways, scale of plant and combined heat and power generation

A previously-developed mechanistic energy balance model for production of biogas from the anaerobic digestion of microalgal biomass grown in open raceway systems was used to consider the energetic viability of a number of scenarios, and to explore some of the most critical parameters affecting net energy production. The output demonstrated that no single harvesting method of those considered (centrifugation, settlement or flocculation) produced an energy output sufficiently greater than operational energy inputs to make microalgal biogas production energetically viable. Combinations of harvesting methods could produce energy outputs 2.3–3.4 times greater than the operational energy inputs. Electrical energy to power pumps, mixers and harvesting systems was 5–8 times greater than the heating energy requirement. If the energy to power the plant is generated locally in a combined heat and power unit, a considerable amount of ‘low grade’ heat will be available that is not required by the process, and for the system to show a net operational energy return this must be exploited. It is concluded that the production of microalgal biogas may be energetically viable, but it is dependent on the effective use of the heat generated by the combustion of biogas in combined heat and power units to show an operational energy retur

Review of \u3ci\u3eRe-Dressing America’s Frontier Past\u3c/i\u3e. By Peter Boag.

Long-established notions about life on the frontier are upended in this well-researched and finely written study of gender presentation, as the author maintains that cross-dressing was “very much a part of daily life on the frontier West.” Peter Boag recognizes the diversity and complexity of this issue, and one of the book’s strengths is that he seeks no simple answer to questions of why some women dressed as men, and some men dressed as women. Most readers will be familiar with the “progress narrative”—the story of women who passed as men in order to seek gainful employment, to serve their country in the military, or simply to travel unmolested—but Boag also includes women who continued to present themselves as men long after the need to crossdress would seem to have passed. As a parallel, he explores the gender implications of men who took the less understandable course of abandoning masculine privilege in order to embrace the more difficult frontier life of a person perceived to be a woman

Review of \u3ci\u3eRe-Dressing America’s Frontier Past\u3c/i\u3e. By Peter Boag.

Long-established notions about life on the frontier are upended in this well-researched and finely written study of gender presentation, as the author maintains that cross-dressing was “very much a part of daily life on the frontier West.” Peter Boag recognizes the diversity and complexity of this issue, and one of the book’s strengths is that he seeks no simple answer to questions of why some women dressed as men, and some men dressed as women. Most readers will be familiar with the “progress narrative”—the story of women who passed as men in order to seek gainful employment, to serve their country in the military, or simply to travel unmolested—but Boag also includes women who continued to present themselves as men long after the need to crossdress would seem to have passed. As a parallel, he explores the gender implications of men who took the less understandable course of abandoning masculine privilege in order to embrace the more difficult frontier life of a person perceived to be a woman

Ultra-low voltage embedded processor system for Internet-of-Things microcontrollers

As devices get an ever increasing foothold on the internet and the Internet of Things becomes the usual landscape in the mass consumer electronic products is necessary to bring embedded processors capable of bringing performance to the micro controllers of such devices. compares Is the intention of this project to compare under different scenarios suitable for the applications two embedded processors form Atmel s one AVR 8-bit and an AVR32 UC3 to identify which is the one that has the lowest power consumption, lowest energy consumption. It has been shown that the AVR has the less power consumption(about half) but in terms of energy the AVR32 is less taxing. A test bench was implemented including SPI communication modules and memories,This is due to the long execution times of the AVR which are for 1.5 to 10 longer than the AVR32. These conclusions scale when implementing on lower feature size (this project uses UMC s 130nm typical process library and UMC s 65 typical process library). Also the conclusion stand when restricting the standard library such that an Ultra low voltage friendly net list is produced and tested yielding similar results

Integrating microalgae production with anaerobic digestion: a biorefinery approach

This is the peer reviewed version of the following article: [Uggetti, E. , Sialve, B. , Trably, E. and Steyer, J. (2014), Integrating microalgae production with anaerobic digestion: a biorefinery approach. Biofuels, Bioprod. Bioref, 8: 516-529. doi:10.1002/bbb.1469], which has been published in final form at https://doi.org/10.1002/bbb.1469. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingIn the energy and chemical sectors, alternative production chains should be considered in order to simultaneously reduce the dependence on oil and mitigate climate change. Biomass is probably the only viable alternative to fossil resources for production of liquid transportation fuels and chemicals since, besides fossils, it is one of the only available sources of carbon-rich material on Earth. Over recent years, interest in microalgae biomass has grown in both fundamental and applied research fields. The biorefinery concept includes different technologies able to convert biomass into added-value chemicals, products (food and feed) and biofuels (biodiesel, bioethanol, biohydrogen). As in oil refinery, a biorefinery aims at producing multiple products, maximizing the value derived from differences in biomass components, including microalgae. This paper provides an overview of the various microalgae-derived products, focusing on anaerobic digestion for conversion of microalgal biomass into methane. Special attention is paid to the range of possible inputs for anaerobic digestion (microalgal biomass and microalgal residue after lipid extraction) and the outputs resulting from the process (e.g. biogas and digestate). The strong interest in microalgae anaerobic digestion lies in its ability to mineralize microalgae containing organic nitrogen and phosphorus, resulting in a flux of ammonium and phosphate that can then be used as substrate for growing microalgae or that can be further processed to produce fertilizers. At present, anaerobic digestion outputs can provide nutrients, CO2 and water to cultivate microalgae, which in turn, are used as substrate for methane and fertilizer generation.Peer ReviewedPostprint (author's final draft

Achieving a Green Solution: Limitations and Focus Points for Sustainable Algal Fuels

Research investigating the potential of producing biofuels from algae has been enjoying a recent revival due to heightened oil prices, uncertain fossil fuel sources and legislative targets aimed at reducing our contribution to climate change. If the concept is to become a reality however, many obstacles need to be overcome. Recent studies have suggested that open ponds provide the most sustainable means of cultivation infrastructure due to their low energy inputs compared to more energy intensive photobioreactors. Most studies have focused on strains of algae which are capable of yielding high oil concentrations combined with high productivity. Yet it is very difficult to cultivate such strains in open ponds as a result of microbial competition and limited radiation-use efficiency. To improve viability, the use of wastewater has been considered by many researchers as a potential source of nutrients with the added benefit of tertiary water treatment however productivity rates are affected and optimal conditions can be difficult to maintain year round. This paper investigates the process streams which are likely to provide the most viable methods of energy recovery from cultivating and processing algal biomass. The key findings are the importance of a flexible approach which depends upon location of the cultivation ponds and the industry targeted. Additionally this study recommends moving towards technologies producing higher energy recoveries such as pyrolysis or anaerobic digestion as opposed to other studies which focused upon biodiesel production

Light regime characterization in an airlift photobioreactor for production of microalgae with high starch content

The slow development of microalgal biotechnology is due to the failure in the design of large-scale photobioreactors (PBRs) where light energy is efficiently utilized. In this work, both the quality and the amount of light reaching a given point of the PBR were determined and correlated with cell density, light path length, and PBR geometry. This was made for two different geometries of the downcomer of an airlift PBR using optical fiber technology that allows to obtain information about quantitative and qualitative aspects of light patterns. This is important since the ability of microalgae to use the energy of photons is different, depending on the wavelength of the radiation. The results show that the circular geometry allows a more efficient light penetration, especially in the locations with a higher radial coordinate (r) when compared to the plane geometry; these observations were confirmed by the occurrence of a higher fraction of illuminated volume of the PBR for this geometry. An equation is proposed to correlate the relative light intensity with the penetration distance for both geometries and different microalgae cell concentrations. It was shown that the attenuation of light intensity is dependent on its wavelength, cell concentration, geometry of PBR, and the penetration distance of light.Fundação para a Ciência e a Tecnologia (FCT

Microalgal Biomass for Greenhouse Gas Reductions: Potential for Replacement of Fossil Fuels and Animal Feeds

Microalgal biomass production offers a number of advantages over conventional biomass production, including higher productivities, use of otherwise nonproductive land, reuse and recovery of waste nutrients, use of saline or brackish waters, and reuse of CO2 from power-plant flue gas or similar sources. Microalgal biomass production and utilization offers potential for greenhouse gas (GHG) avoidance by providing biofuel replacement of fossil fuels and carbon-neutral animal feeds. This paper presents an initial analysis of the potential for GHG avoidance using a proposed algal biomass production system coupled to recovery of flue-gas CO2 combined with waste sludge and/or animal manure utilization. A model is constructed around a 50-MW natural gas-fired electrical generation plant operating at 50% capacity as a semibase-load facility. This facility is projected to produce 216 million k·Wh/240-day season while releasing 30.3 million kg-C/season of GHG-CO2. An algal system designed to capture 70% of flue-gas CO2 would produce 42,400 metric tons (dry wt.) of algal biomass/season and requires 880 ha of high-rate algal ponds operating at a productivity of 20 g-dry-wt/m2-day. This algal biomass is assumed to be fractionated into 20% extractable algal oil, useful for biodiesel, with the 50% protein content providing animal feed replacement and 30% residual algal biomass digested to produce methane gas, providing gross GHG avoidances of 20, 8.5, and 7.8%, respectively. The total gross GHG avoidance potential of 36.3% results in a net GHG avoidance of 26.3% after accounting for 10% parasitic energy costs. Parasitic energy is required to deliver CO2 to the algal culture and to harvest and process algal biomass and algal products. At CO2 utilization efficiencies predicted to range from 60–80%, net GHG avoidances are estimated to range from 22–30%. To provide nutrients for algal growth and to ensure optimal algae digestion, importation of 53 t/day of waste paper, municipal sludge, or animal manure would be required. This analysis does not address the economics of the processes considered. Rather, the focus is directed at determination of the technical feasibility of applying integrated algal processes for fossil-fuel replacement and power-plant GHG avoidance. The technology discussed remains in early stages of development, with many important technical issues yet to be addressed. Although theoretically promising, successful integration of waste treatment processes with algal recovery of flue-gas CO2 will require pilot-scale trials and field demonstrations to more precisely define the many detailed design requirements