Category Archives: Scientific Papers

Microalgal biofuels: Flexible bioenergies for sustainable development

aaaaaa11111Abstract – To confront energy shortage, global warming and climate changes, biofuels derived from biomass have received increasing attention from the industry, academia and governments. Of the potential sources of biofuels a most promising one is the simple photosynthetic microalgae, which can be grown in open ponds, photobioreactors and fermenters. The advantages to produce biofuels from microalgae include easy adaption to environmental conditions, high photosynthesis efficiency, high lipid content and noncompetition for farmlands. Nonetheless, the real hallmark of microalgae is the fact that these microscopic organisms can provide the biomass feedstock for the flexible production of several different types of renewable and sustainable biofuels such as biodiesel, bioethanol, biogas, biohydrogen among others via thermochemical and biochemical conversion processes. Amazingly, from a sustainability perspective the integrated algal biofuels production, where biodiesel, bioethanol and biogas are continuously produced from one biomass source, can evidently lead to an increase in the energetic productivity of the microalgal biomass, thus improving the economics of this algal biorefinery approach. Developments in several areas, such as genetic and metabolic engineering, are expected to further improve the costeffectiveness of the biofuels from microalgae in an environmentally sustainable manner.
Source: ScienceDirect, December 2, 2013
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New Tools for Precision Feeding

18The Pig Site – The current high feed costs increase the need for developing cost-effective feeding strategies for growing-finishing pigs. Well-tested mathematical models that represent nutrient utilisation for growth allow for a systematic approach to optimising feeding programmes for individual pig units, considering local pig performance potentials and available feed ingredients, as well as environmental and economic conditions.

In this paper, Professor Kees de Lange presented examples are given where the NRC (2012) Nutrient Requirements of Swine model for growing-finishing pigs is used to explore effects of gender, pig performance potentials, feed intake, and use of high-fibre co-products as feed ingredients on nutrient requirements.

These examples stress the need to monitor closely current performance and to evaluate feeding programmes regularly…>>Continue Reading<<

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Estimating the Biodiesel Supply Curve

2The CROP Site – The purpose of this post is to derive the biodiesel supply curve from the relationships first presented in the September 25 post.

We begin by reviewing the main results of that earlier post. Figure 1 shows a scatter of monthly biodiesel production and net returns above variable costs for each calendar year between 2010 and 2013. Monthly biodiesel production is estimated by the EIA and monthly biodiesel net production returns above variable costs are based on a model of a representative Iowa biodiesel plant (see the post here).

A best-fit regression line is also shown for each year, with the natural log (ln) of production used as the dependent variable. The data are divided by calendar years because in years when the blenders tax credit is not in place (2010 and 2012) there is little relationship between biodiesel production and returns. Basically, production in these years is “stuck” at the RFS biodiesel mandate regardless of the level of returns.

In the other years (2011 and 2013) market participants expect the credit to expire at the end of a calendar year, so there there is an obvious incentive for blenders to bid up the price of biodiesel in order to increase production and take full advantage of the credit before it expires. In essence, the unusual market circumstances in 2011 and 2013 provide a unique opportunity to identify a biodiesel supply curve even with a seemingly binding RFS mandate in place…>>Continue Reading<<

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Effects of Slaughtering Methods on Protein Denaturation of Frozen Pacu Fillets

Pacu_sheddViegas et al, October 2013

Summary – Pacu is an omnivorous, freshwater fish typical of the wetlands located in South Mato Grosso, Brazil, which can also be found in the rivers of the Amazon and Prata basins. It is a species widely cultivated in Brazil due to its fast growth, hardiness and good acceptance by the consumers (MPA, 2010).

The freshwater fish cultivated in Brazil are most commonly stunned and slaughtered by thermal shock (1:1 water and ice); a method that is proven stressful since it does not kill immediately and can affect meat quality.

Due to pacu importance to Brazilian Aquaculture, it is necessary to determine the best slaughtering method in order to improve meat quality. The objective of this study is to evaluate how the usual methods used to slaughter pacu (electrical stunning, thermal shock and CO2 narcosis) influence protein denaturation of frozen fillets stored for 180 days.

Click here to access the complete article
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Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate

Mezarri et al., October, 2013
 
Abstract – This study investigated the interactions between naturally occurring bacteria and the microalgae Chlorella vulgaris within a lab scale photobioreactor treating ammonia-rich swine wastewater digestate effluent. Nitrification and denitrification were assessed by targeting ammonia monoxygenases (amoA), nitrate (narG), nitrite (nirS), nitric oxide (norB) and nitrous oxide (nosZ) reductases genes. Oxygen produced from microalgae photosynthesis stimulated nitrification. Under limiting carbon availability (i.e., <1.44 for mg TOC/mg NO2-N and 1.72 for mg TOC/mg NO3–N), incomplete denitrification led to accumulation of NO2 and NO3. Significant N2O emission (up to 118 μg N2O–N) was linked to NO2 metabolism in Chlorella. The addition of acetate as external carbon source recovered heterotrophic denitrification activity suppressing N2O emission. Effluent methane concentrations trapped within photobioreactor was removed concomitantly with ammonia. Overall, closed photobioreactors can be built to effectively remove nitrogen and mitigate simultaneously greenhouse gases emissions that would occur otherwise in open microalgae-based wastewater treatment systems.
 
Click here to access the article at ScienceDirect
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Optimization methods applied to renewable and sustainable energy: A review

4Science Direct (Summary) – Energy is a vital input for social and economic development. As a result of the generalization of agricultural, industrial and domestic activities the demand for energy has increased remarkably, especially in emergent countries. This has meant rapid grower in the level of greenhouse gas emissions and the increase in fuel prices, which are the main driving forces behind efforts to utilize renewable energy sources more effectively, i.e. energy which comes from natural resources and is also naturally replenished. Despite the obvious advantages of renewable energy, it presents important drawbacks, such as the discontinuity of generation, as most renewable energy resources depend on the climate, which is why their use requires complex design, planning and control optimization methods. Continue reading

Biofuels from microalgae—A review of technologies for production, processing, and extractions of biofuels and co-products

4Science Direct (Summary) – Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world’s forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Continue reading